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# November 2013
You are currently browsing the monthly archive for November 2013.
## “Basic Concepts in Information Theory”
I have been wanting to write a post about using mutual information for feature selection, but I know that a few readers do not know information theory. Some of my executive friends have forgotten all of their calculus, so I will probably first write a short executive introduction to information theory next week or find an appropriate introduction on the internet. Earlier today while I was looking for a very basic introduction, I ran across the 111 page “Basic Concepts in Information Theory” by Marc Uro and the 3 page blog post “A Short, Simple Introduction to Information Theory” by Ryan Moulton which are both appropriate for undergraduate sophomores.
Marc’s book is great. It covers all of the basic information theory ideas like entropy, cross-entropy, mutual information, linear codes, compression, and Shannon capacity. Most of his explanations use only basic probability with a little summation notation and a matrix or two. (His notation is carefully crafted, but sometimes a bit non-standard). He avoids using calculus, so this book can be read by a bright freshman.
Ryan’s two page web post uses a little probability, logarithms, and summation notation but nothing else.
## The Big O writes on Scientific Error, Bias, and Self-(peer)-review.
I have slightly edited the post below by my friend the big O.
After all my complaining I have reached an actual argument about scientists or, better put, the science class. They lack rigorous checks and balances.
To think that science can effectively check itself for error and bias just because they’re supposed to is analogous to thinking that the house of representatives can effectively check itself for error and bias just because they’re supposed to. But we know that the job of congressman frequently attracts a type of personality. We know there is an attractive glory to accomplishment in government as there is an attractive glory to accomplishing something in science. We know that money provides an incentivizing role in even the noblest of endeavors.
And so in government we have branches whose explicit role is to check and balance one another. And we have a press whose job is to check and seek error with the government itself. And we have a population who feel no embarrassment at checking everyone: we scrutinize the press, we critique the government in general, and we attack specific branches of government, all the while recognizing that government by the people (etc.) is prone to errors and biases specifically because it is a government run by people.
This is not the attitude we have with the class of people who conduct science. The scientist class has reached such a rarefied status that it lacks equivalent checks and balances. We expect scientists to nobly check themselves. But i argue they cannot because they’re people. We need more rigorous outside skepticism than we currently have.
Science has the hardest arguments on earth to develop, prove, justify, and explain because the arguments of science are targeted at revealing something close to objective truth. there are more obstacles and unseen variables between scientific theory and proof than in any other field. I think we would be better off to consider non-scientist (a “scientist” today being someone who is sanctioned by a university to be labeled as such) checking and balancing as part of – not apart from – the scientific process.
I like the idea of retaining a unembarrassed and reasoned skepticism of the “truth” offered by scientists – particularly in the weak sciences – and instead accept effectiveness (e.g. when science becomes technology) as truth. When something – a theory or an experiment – works in our daily lives we can label that something as “true enough to be effective” and realize that as an auspicious label. The rest should invite continued checking and balancing from both in and outside the scientific class.
$$\$$
And then in another email, I added this as a response to my critics:
The one thing I do not attack is the scientific method or reason.
I say the scientific method is not currently being employed to an extent that it could be and we’re worse off for it. As evidence of this I see the very frequent conflation of science – which is an effective process – with scientists – whom I consider to be as flawed and for the same reasons as any other profession. (That npr study conforms with my personal experience that scientists my be more justifying of their bias than others). This conflation leads to a citizenry reluctant to be skeptical of scientists and scientific work because they fear they are questioning science. They are not. they are a part (apparently unknowingly) of science and their reluctance to analyze, question, investigate, criticize scientists and scientist’s work leads to a weakening of science.
The peer review you cite is precisely what I am labeling inadequate. What if a congressman suggested his law was good because it had been peer reviewed? What if he said he had special training as a lawyer or an economist or a historian? Would that be a satisfying rational not to have separate gov’t branches, press, or citizenry actively challenge his work? Scientific peer review is equivalent to gov’t peer review – it is necessary but less adequate than broadening that peer review to others currently only limitedly involved or allowed in the process.
Again: re: the scientific method, I don’t believe that a science that includes only an academia certified science class does or even can adequately follow the scientific method to its fullest rigor anymore than congress can adequately run the government to its fullest rigor minus the critical analysis of outside agencies such as other branches of gov’t, the press, and citizenry.
## Simple Fact about Maximizing a Gaussian
Over the last few weeks, I’ve been working with some tricky features. Interestingly, I needed to add noise to the features to improve my classifier performance. I will write a post on these “confounding features” later. For now, let me just point out the following useful fact.
If
$$f(x, \sigma) = {1\over{\sigma \sqrt{2 \pi}}} \exp{\left(-{{x^2}\over{2 \sigma^2}}\right)},$$
then
$$\max_\sigma f(x,\sigma) = f(x, |x|).$$
So, if you have a Gaussian with mean zero and you want to fatten it to maximize the likelihood of the probability density function at $x$ without changing the mean, then set the standard deviation to $|x|$.
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https://www.physicsforums.com/threads/time-dilation-questions.271906/
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# Time dilation questions
1. Nov 14, 2008
### yinfudan
In a standard configuration, which frame O' is moving along the x-axis of frame O with speed v, clock is synchronized to 0 when origin O' coincides origin O. Also, let us use normalized scale. The unit of time t is second; the unit of x-axis x is light-second; and thus the velocity v = x/t is the ratio of speed with the light speed, 0<=v<1, γ=1 / sqrt(1-v2)
My question is, is it true that the famous time dilation only applies to an observer in frame O watching clocks at rest in frame O'? More specifically, when the clock rested at x'=0 in frame O' reaches the first tick at t'=1, the observer's clock in frame O has reached γ ticks. Also, the clock rested at x'=1 in frame O' ticks at the same rate as the clock rested at x'=0 in frame O'. But for an observer in frame O, the clock rested at x'=1 in frame O' will reach its first tick later than the clock rested at x'=0 in frame O'. This delay is vγ.
Another question is, a uniformly moving clock in frame O' will cause different time dilation rates for an observer in frame O. Is it true? For example, a moving clock in frame O' with positive speed has an even higher time dilation rate. For example, if in frame O', a clock is traveling at the speed of light from origin O' at t'=0 (v'clock=1, normalized scale), when this clock is reaching x'=1 at t'=1, the observer's clock in frame O has ticked (1+v)γ ticks, which is a higher rate than γ. On the other hand, a moving clock in frame O' with negative speed has a lower time dilation rate and can even cause time contraction. For example, if in frame O', a clock is traveling at the speed of light but to the -x' direction, from origin O' at t'=0, when this clock is reaching x'=-1 at t'=1, the observer's clock in frame O has only ticked (1-v)γ ticks, appearing as the clock in frame O' is ticking faster.
Could you please review my statement and tell me if it is correct or not? Thanks a lot!
Last edited: Nov 14, 2008
2. Nov 14, 2008
### JesseM
Time dilation is symmetrical, if that's what you're asking. An observer in frame O' watching clocks at rest in frame O will see them slowed down by the same time dilation factor. See this thread for an illustration.
The clocks at x'=0 and x'=1 will reach there first ticks at different times in frame O because of the relativity of simultaneity--clocks which are synchronized in frame O' will be out-of-sync in frame O. They are both ticking at the same rate in frame O, but in frame O the two clocks showed different starting times at t=0, and their times continue to be out-of-sync by the same fixed amount at later times.
As a general rule, if two clocks are synchronized and a distance of d apart from one another in their own rest frame, then in a frame where they are moving at speed v along the axis connecting them, they will be out-of-sync by the constant amount vd/c^2, with the trailing clock being ahead of the leading clock by this amount. So with d=1 for the clocks at x'=0 and x'=1, in the O frame they will be out-of-sync by v/c^2, meaning that when the clock at x'=0 reads a time of 1 second, the clock at x'=1 reads (1 second - v/c^2) in the O frame. Since the clock at x'=1 is slowed by a factor of gamma, it takes an additional gamma*v/c^2 seconds for this clock to reach a time of 1 second in the O frame.
You can use the relativistic velocity addition formula to figure out the speed of this clock in frame O, and from there you can figure out the time dilation factor in frame O. But I don't understand what you mean by "normalized scale"--what units are you talking about when you say the speed is 1? Are you using a scale where c=1 (in which case it would be impossible for a clock to move at this speed) or some other set of units? Anyway, if the clock is traveling at velocity v1 in the +x' direction in frame O', and frame O' is moving at velocity v in the +x direction in frame O, then the clock is moving at velocity v2 = (v + v1)/(1 + v*v1/c^2) in the +x direction of frame O. So, its time dilation factor in frame O would be $$1/\sqrt{1 - v_2^2 /c^2}$$. I don't think this is the same as $$(v1 + v)/\sqrt{1 - v^2/c^2}$$ as you seem to suggest above.
No clock is observed to experience "time contraction" (i.e. a faster rate of ticking than a clock at rest) in any inertial frame.
A clock cannot travel at the speed of light in SR. And in the limit as a clock's speed approaches c, its time dilation factor approaches infinity (i.e. the clock approaches being completely frozen). Also, if a clock is traveling at v1 in the -x' direction in frame O' (i.e. negative velocity in the +x' direction of frame O', the phrase 'negative speed' is meaningless since speed is the magnitude of the velocity vector), then in frame O the velocity addition formula tells you that it must be moving at velocity v2 = (-v1 + v)/(1 - v1*v/c^2) in the +x direction of frame O (if v2 is negative, then this means the object is moving in the -x direction). The time dilation factor will still be $$1/\sqrt{1 - v_2^2/c^2}$$.
3. Nov 14, 2008
### Staff: Mentor
No. Observers in any frame will observe time dilation for any clock moving with respect to that frame.
OK.
OK.
OK. This is due to both time dilation and the relativity of simultaneity (clock desynchronization).
Sure. Time dilation depends on the speed of the moving clock in the observing frame.
This is a bit confusing (for example, clocks don't move at the speed of light), but since frame O will see that moving clock move faster than the clocks at rest in O', O will see that moving clock as being more strongly time dilated.
No one will see anything "time contracted", whatever that might mean. Since, with respect to O, the moving clock is now moving slower than clocks at rest in O', O will see it less strongly time dilated. But both O and O' will see this moving clock as time dilated, as expected.
4. Nov 14, 2008
### yinfudan
Thank you Doc Al!
I still have some concern regarding my second question: "Another question is, a uniformly moving clock in frame O' will cause different time dilation rates for an observer in frame O. Is it true?"
I will prepare another two examples avoiding clocking traveling at the speed of light. I will reply with the examples as soon as possible. Hope you could comment on it again.
Thank you!
5. Nov 14, 2008
### yinfudan
Again our measurement is done in a standard configuration, which frame O' is moving along the x-axis of frame O with speed v, clock is synchronized to 0 when origin O' coincides origin O. Also, let us use normalized scale. The unit of time t is second; the unit of x-axis x is light-second; and thus the velocity v=x/t is the ratio of speed with the light speed, 0<=v<1, γ=1/sqrt(1-v2)
First example: In frame O', a clock is traveling at 0.75 times speed of light from origin O' at t'=0 (v'clock=0.75, normalized scale). When this clock reaches x'=0.75 at t'=1 in frame O', the observer in frame O sees the clock reaches x=(v+0.75)*γ at t=(1+0.75*v)*γ.
Let v=0.66, thus γ=1.34. Therefore after one second in frame O', t=(1+0.75*0.66)*1.34=2.00 seconds has passed in frame O. So the time dilation factor is increased.
Second example: In frame O', a clock is traveling at 0.75 times speed of light from origin O' at t'=0, towards -x' direction instead. When this clock reaches x'=-0.75 at t'=1 in frame O', the observer in frame O sees the clock reaches x=(v-0.75)*γ at t=(1-0.75*v)*γ.
Let v=0.66, thus γ=1.34. Therefore after one second in frame O', t=(1-0.75*0.66)*1.34=0.67 seconds has passed in frame O. In this case, the observer in frame O thinks the clock in frame O' is running more quickly. Can I call this time contraction?
6. Nov 14, 2008
### JesseM
Yes, that's correct according to the Lorentz transformation:
x = gamma * (x' + vt')
t = gamma * (t' + vx'/c^2)
Would actually be closer to 1.33, but OK.
If you want three significant figures it should be 1.99 seconds, although for greater precision we might use 1.9899753 seconds.
Yes, that's true. If we have marker at the origin of O' and another marker at x'=0.75 of O', then the time between the event of the clock passing the first marker and the event of the clock passing the second marker is 1 second in the O' frame but 1.9899753 seconds in the O frame. Both frames must agree on how much time elapsed on the moving clock between passing the two markers (because all frames agree on local events like what a clock reads as it passes next to some other object); since the O frame says it took twice as long to pass between the two markers, it must have been ticking twice as slow. To use your numbers, in the O' frame we can calculate that the clock must have been slowed by a factor of sqrt(1 - 0.75^2) = 0.66144, so if it read a time of T=0 as it passed the first marker it must have read a time of T=0.66144 as it passed the second marker. This means that in the O frame the clock took 1.9899753 seconds to go from reading T=0 to T=0.66144, which means it must have been ticking at a rate of 0.33238 ticks per second of time in the O frame.
This is the same answer as you'd get if you used the velocity addition formula--if the clock is moving at 0.75c in frame O' and O' is moving at 0.66c relative to frame O, then the clock is moving at (0.75c + 0.66c)/(1 + 0.75*0.66) = 1.41c/1.495 = 0.943144c in frame O, and sqrt(1 - 0.943144^2) = 0.33238.
More precisely it'd be t=0.672199
No, you've made a mistake here, the clock is still running slow in frame O, just by a smaller amount. Again suppose in frame O' we have a marker at the origin, and another at position x'=-0.75. If the clock reads T=0 as it passes the first marker at the origin, it will read T=0.66144 as it passes the second marker. In frame O, 0.672199 seconds passed between the event of the clock passing next to the first marker and the event of it passing next to the second, so the clock was still running slightly slow, by a factor of 0.66144/0.672199 = 0.984 ticks per second of time in frame O.
This is also what you get if you use the velocity addition formula to find the clock's speed in frame O--the formula tells you the clock's velocity in the +x direction must have been (0.66c - 0.75c)/(1 - 0.66*0.75) = -0.1782c (i.e. a speed of 0.1782c in the -x direction), so the time dilation factor would be sqrt(1 - 0.1782^2) = 0.984.
7. Nov 15, 2008
### yinfudan
Thank you very much Jesse for your answer in such great detail.
Now I agree with you in the second example, that the moving clock in frame O' is running slightly slow. However, I do have another question if we think in a different way - we simply replace the moving clock with a moving baseball:
Second example: In frame O', a baseball is traveling at 0.75 times speed of light from origin O' at t'=0, towards -x' direction instead. When this baseball reaches x'=-0.75 at t'=1 in frame O', the observer in frame O sees the baseball reaches x=(v-0.75)*γ at t=(1-0.75*v)*γ. Let v=0.66, thus γ=1.33. Therefore, when x'=-0.75, t'=1, x=-0.12, t=0.67.
You can still put two markers on x'=0 and x'=0.75 on frame O'. Note that the two markers are at rest in frame O', and are moving together with frame O' respective to frame O. And the observer in frame O even sees the distance between the two markers shorter by γ times, which is 0.75/1.33=0.56. Also, at t=0.67, the observer in frame O checks his own clock, it reads 0.67. At the same time, the observer also checks the clock resting at origin O' in frame O', it reads 0.67/γ=0.67/1.33=0.50.
Could you please confirm everything is still correct above?
Now, someone in frame O' can clearly claim, the time span between the baseball passing the first marker and the baseball passing the second marker is 1 second. Or in other words, baseball moving process takes 1 second.
But the observer in frame O is confused. According to his own clock, the baseball moving process takes 0.67 second. According to the clock in frame O', the baseball moving process takes 0.50 second. Which is correct? Is the time dilated (0.67 > 0.50) or contracted (0.67 < 1)?
8. Nov 15, 2008
### JesseM
OK, that works.
You mean x'=-0.75, right?
Yup, that's about right (the exact time on the clock would be 0.505 seconds), but note that the clock resting at at x'=-0.75 in O' does *not* read 0.505 at that same moment in frame O, because of the relativity of simultaneity. As I mentioned in my first post on this thread:
In this case, d=0.75 in the rest frame of the two clocks, and they are both moving at 0.66c in the O frame, so in the O frame the trailing clock (the one at x'=-0.75c) is ahead of the leading clock (the one at x'=0) by 0.75*0.66 = 0.495 seconds. This means that when the clock at x'=0 reads 0.505 seconds, the clock at x'=-0.75 reads 0.505 + 0.495 = 1 second, according to the frame O definition of simultaneity.
Yes.
No, in order to time a moving process, you must compare the time on a local clock at the starting point with the time on a local clock at the ending point. Frame O sees that when the baseball was next to the clock at x'=0, the clock at x'=0 read 0 seconds (while the clock at x'=-0.75 already read 0.495 seconds at that moment in frame O), and that when the baseball was next to the clock at x'=-0.75, the clock at x'=-0.75 read 1 second (while the clock at x'=0 read only 0.505 seconds at that moment in frame O). So, frame O can see that frame O' will measure the time to be 1 second, not 0.505 seconds.
9. Nov 15, 2008
### yinfudan
Thank you very much for your time and patience, Jesse. Now comes to the last question regarding this scenario:
Due to time dilation, the observer in frame O will think most processes take more time to finish in frame O than in frame O'. For example, a tick of a resting clock in frame O' takes 1 second in frame O' but 1.33 second in frame O.
But in this case, the observer in frame O can see and deduce frame O' will measure the baseball moving process to be 1 second. But the observer in frame O measures the process in his own frame, it is 0.67 second. So this time, this process in takes less time to finish in frame O than in frame O'.
So the observer feels time dilation rate is not reliable. It varies with different processes. How can it be?
Last edited: Nov 15, 2008
10. Nov 16, 2008
### JesseM
Not "most processes", only processes along the worldlines of objects which have a lower speed in frame O' than in frame O will take longer to finish in frame O. As a counterexample, a clock at rest in frame O (which naturally has a greater speed in frame O') takes 1.33 seconds between ticks in frame O' but 1 second between ticks in frame O. Strictly speaking, the time dilation equation as it's normally written is only intended to compare the time between events along the worldline of an object at rest in one frame with the time between the same events in a frame where that object is moving at speed v; if the time between the events in the frame where the object is at rest is T, then the time T' between the events in the second frame where the object is moving at speed v will be given by $$T' = \frac{T}{\sqrt{1 - v^2/c^2}}$$. If you wanted to talk about the time in each frame between events on the wordline of an object that was not at rest in either frame, this equation wouldn't be the correct one to use (although each frame could use it to determine how much the time was expanded in their own frame relative to the object's own rest frame, and then compare their answers).
Last edited: Nov 16, 2008
11. Nov 16, 2008
### yinfudan
I got your point Jesse. Thank you so much! Tomorrow I am going to post another thread about length contraction - an experiment that will cause a gradient colored moving rod. I really hope you could take a look, because I find myself easier to understand your responds.
Similar Discussions: Time dilation questions
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http://mathhelpforum.com/calculus/207380-calculus-curve-sketching.html
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# Math Help - Calculus curve sketching
1. ## Calculus curve sketching
sketch the graph of a function f having given characteristics
f(2) = f(4) = 0
f(3) is defined.
f'(x) < 0 if x < 3
f'(3) does not exist.
f'(x) > 0 if x > 3
f"(x) < 0, x does not equal 3
2. ## Re: Calculus curve sketching
Hey asilverster635.
If you show us what you have tried and any partial attempts you have made, then you will get a more specific and directed answer from other members.
3. ## Re: Calculus curve sketching
i have no idea how to do this type of problem
4. ## Re: Calculus curve sketching
If the derivative doesn't exist at a point it means there is a discontinuity.
If you have a positive derivative it means the function is increasing: if it is negative then it is decreasing.
If f(3) is defined but f'(3) doesn't exist, then it means you have either a discontinuity in the graph or the graph itself has a "kink" in it and isn't smooth (but is still continuous).
If second derivative is increasing then first derivative is increasing: if decreasing then derivative is decreasing.
There are many solutions to this problem graphically and function-wise but they will have the attributes outlined with the above characteristics of derivatives.
5. ## Re: Calculus curve sketching
All of these have a graphical equivalent - for example f(2)=0 means that the graph passes through (0,2). Once you have "translated" them all, you have a description of the graph, so you just need to draw it.
- Hollywood
6. ## Re: Calculus curve sketching
Originally Posted by chiro
If the derivative doesn't exist at a point it means there is a discontinuity.
Technically not correct - the graph could have a "kink" like the function f(x)=|x| at x=0.
Originally Posted by chiro
If second derivative is increasing then first derivative is increasing: if decreasing then derivative is decreasing.
It's probably better to say that if the second derivative is negative, then the function is concave down. And also (though it's not needed for this problem) if the second derivative is positive, then the function is concave up.
- Hollywood
thanks guys
8. ## Re: Calculus curve sketching
Originally Posted by hollywood
the graph could have a "kink" like the function f(x)=|x| at x=0.
A better word would be "corner". I don't know of any mathematical term for it.
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https://rd.springer.com/article/10.1007/s11804-019-00091-9
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Journal of Marine Science and Application
, Volume 18, Issue 2, pp 123–130
# Modeling of Roll-Heave-Pitch Motions of a Ram Wing Translating over Non-uniform Surface
• Konstantin I. Matveev
Open Access
Research Article
## Abstract
Ground-effect vehicles flying close to water or ground often employ ram wings which generate aerodynamic lift primarily on their lower surfaces. The subject of this paper is the 3-DOF modeling of roll, heave, and pitch motions of such a wing in the presence of surface waves and other ground non-uniformities. The potential-flow extreme-ground-effect theory is applied for calculating unsteady pressure distribution under the wing which defines instantaneous lift force and moments. Dynamic simulations of a selected ram wing configuration are carried out in the presence of surface waves of various headings and wavelengths, as well as for transient flights over a ground obstacle. The largest amplitudes of the vehicle motions are observed in beam waves when the periods of the encounter are long. Nonlinear effects are more pronounced for pitch angles than for roll and heave. The present method can be adapted for modeling of air-supported lifting surfaces on fast marine vehicles.
## Keywords
Ram wing Ground effect Seakeeping Dynamics Modeling Potential flow theory
## 1 Introduction
High-speed marine craft can benefit from application or aerodynamically supported wings or platforms. Examples include racing boats of hydroplane and tunnel-hull types, wing-in-ground vehicles, and fast amphibious platforms (Matveev and Kornev 2013). Their air-supported lifting elements often operate in strong ground effect, which usually enhances lift and reduces drag, whereas the upper surfaces of these wings either are weakly affected by the proximity to water or may not even contribute to the lift, e.g., if they used as cargo platforms. The wings of this sort are usually referred to as ram wings (Gallington and Miller 1970).
The most remarkable of aerodynamically assisted marine craft are wing-in-ground (WIG) vehicles. Large, up to 500 tons in displacement, WIG craft were developed in Russia in the last century for military purposes, but they were later abandoned due to high cost and unclear fit into the naval strategy. Smaller, more economical WIG crafts were intermittently produced in several countries, and projects for large WIG transports are still actively considered. One of the most important concerns with these vehicles is their stability and dynamics in open sea conditions due to potentially dangerous high-speed flight close to water.
An extensive list of references on WIG craft is given in a review by Rozhdestvensky (2006). As concerns ram wings operating at low clearances to the ground (less than 0.1 of the wing chord), an important work of Windall and Barrows (1970) can be noted where it was first shown that the airflow under ram wings becomes primarily two-dimensional in a horizontal plane. Gallington and Miller (1970) developed a simplified theory, carried out validating experiments, and constructed experimental model prototypes of ram wings. Staunfenbiel (1987) analyzed the stability of WIG craft, emphasizing dependency of their aerodynamic coefficients on height. One of the first attempts to use viscous solvers of computational fluid dynamics to model three-dimensional WIG was described by Hirata and Kodama (1995). A number of extensions of the extreme-ground-effect (EGE) potential-flow theory for ram wings, including lift-augmenting mechanisms, compressibility effects, and stability, are detailed in the book by Rozhdestvensky (2000). Benedict et al. (2002) analyzed the WIG take-off regimes when the wing is in close proximity to water. Tuck (1984), Barber (2007), and Zong et al. (2012) calculated water surface deformations caused by wings steadily flying in ground effect. Matveev and Chaney (2013), and Liang et al. (2014) modeled airfoils heaving above water surfaces.
Steady and unsteady aerodynamics of ram wings can be effectively modeled with help of EGE theory which assumes potential flow with dominant horizontal air velocities in the channel formed between the wing and the underlying surface (Windall and Barrows 1970; Rozhdestvensky 2000). The EGE theory has been previously validated against experimental data for ram wings with and without side plates (Rozhdestvensky 2000; Matveev 2013) and for power-augmented ram wings where air-based front propulsors produce high-speed airflow incident on the wing even in static conditions (Matveev 2008; Matveev and Soderlund 2008). Simplified modeling for heave-and-pitch motions of ram wings was developed by Matveev (2013). However, from the seaworthiness perspective, the roll dynamics is also of major importance in disturbed environments, such as water surface waves. The present study addresses modeling of small-amplitude 3-DOF motions of a ram wing with aerodynamic coupling between roll, heave, and pitch.
## 2 Mathematical Model
A ram wing flying close to the water surface is considered as shown in Fig. 1. The viscous effects are neglected. The distance from the wing’s lower surface to the water is assumed to be much smaller than the wing chord. With additional assumptions of small slopes of the water waves and small attack angle of the wing, the horizontal (x and z) components of the airflow velocity under the wing become much greater than the vertical (y) component. This allows us to apply the two-dimensional extreme-ground-effect theory developed by Rozhdestvensky (2000). If compressibility effects are also neglected, then the mass conservation principle results in the following equation for the perturbed velocity potential φ in the channel under the wing,
$$\frac{\partial }{\partial x}\left(h\frac{\partial \varphi }{\partial x}\right)+\frac{\partial }{\partial z}\left(h\frac{\partial \varphi }{\partial z}\right)=U\frac{\partial h}{\partial x}-\frac{\partial h}{\partial t}$$
(1)
where h = yp − yw is the local height of the channel between the wing and water, yp and yw are the vertical coordinates of the wing lower side and the water surface, respectively, and U is the constant forward speed of the vehicle. In the applied here, reference frame translating with the vehicle along axis x, the velocity of the incident airflow is −U. Rozhdestvensky (2000) showed that the appropriate boundary conditions in the limit of small ground clearances are φ = 0 at the wing leading edge and the zero gage pressure on the other edges, which imposes the following requirement for the velocity potential at those boundaries,
$$2U\frac{\partial \varphi }{\partial x}-2\frac{\partial \varphi }{\partial t}-{\left(\frac{\partial \varphi }{\partial x}\right)}^2-{\left(\frac{\partial \varphi }{\partial z}\right)}^2=0$$
(2)
After determining a solution for φ, the pressure distribution on the wing lower surface can be calculated from the unsteady Bernoulli equation,
$$p\left(x,z,t\right)=\rho \left[U\frac{\partial \varphi }{\partial x}-\frac{\partial \varphi }{\partial t}-\frac{1}{2}{\left(\frac{\partial \varphi }{\partial x}\right)}^2-\frac{1}{2}{\left(\frac{\partial \varphi }{\partial z}\right)}^2\right]$$
(3)
where ρ is the air density. After that, the instantaneous lift force and coordinates of the center of pressure are found by integrations as follows,
$$L(t)={\int}_0^c\ {\int}_{-s/2}^{s/2}\ p\left(x,z,t\right)\kern0.1em \mathrm{d}z\mathrm{d}x$$
(4)
$${x}_p(t)=\frac{1}{L}{\int}_0^c\ {\int}_{-s/2}^{s/2}\ x\ p\left(x,z,t\right)\kern0.1em \mathrm{d}z\mathrm{d}x$$
(5)
$${z}_p(t)=\frac{1}{L}{\int}_0^c\ {\int}_{-s/2}^{s/2}\ z\ p\kern0.1em \left(x,z,t\right)\kern0.1em \mathrm{d}z\mathrm{d}x$$
(6)
where c and s are the wing chord and span, respectively (Fig. 1b).
In this study, only heave, pitch, and roll motions are considered. Since the vehicle is assumed to translate at a constant forward speed and the underwing lift force dominates in the EGE theory, the other forces (drag, thrust, lift on upper wing side, etc.) are much smaller and only weakly affected by ground effect. Hence, these forces and their moments are neglected in the present analysis of heave-pitch-roll motions. However, if one intends to do detailed modeling of a practical vehicle, these forces can be directly added to the present model.
Under the assumptions of low-amplitude motions and zero non-diagonal products of inertia, the governing dynamics equations can be written in simplified forms as follows,
$$M{\ddot{z}}_{\mathrm{cg}}=L- Mg$$
(7)
$${I}_{zz}\ddot{\alpha}=L\left({x}_p-{x}_{\mathrm{cg}}\right)$$
(8)
$${I}_{xx}\ddot{\psi}=L\left({z}_p-{z}_{\mathrm{cg}}\right)$$
(9)
where xcg, ycg, and zcg are the coordinates of the vehicle’s center of gravity, α and ψ are the trim and roll angles, respectively, M is the vehicle’s mass, Ixx and Izz are the moments of inertia with respect to x and z axes, respectively, and g is the gravitational constant.
The numerical implementation of the model described above is accomplished using a finite-difference method. The second-order spatial discretization and the first-order time stepping are applied for finding the velocity potential, pressure distribution, and simulating vehicle’s dynamics. The wing planform is divided into cells with dimensions ∆x and ∆z along x and z axes, respectively. At a node (xi, zj) away from the wing edges, the discretized form of Eq. (1) for the unknown perturbation velocity potential φ can be written as follows,
$$\frac{h_{i+1,j}-{h}_{i-1,j}}{2\Delta x}\frac{\varphi_{i+1,j}-{\varphi}_{i-1,j}}{2\Delta x}+{h}_{i,j}\frac{\varphi_{i+1,j}-2{\varphi}_{i,j}+{\varphi}_{i-1,j}}{{\Delta x}^2}+\frac{h_{i,j+1}-{h}_{i,j-1}}{2\Delta z}\frac{\varphi_{i,j+1}-{\varphi}_{i,j-1}}{2\Delta z}+{h}_{i,j}\frac{\varphi_{i,j+1}-2{\varphi}_{i,j}+{\varphi}_{i-1,j+1}}{{\Delta z}^2}=U\frac{h_{i+1,j}-{h}_{i-1,j}}{2\Delta x}-{\left(\frac{\partial h}{\partial t}\right)}_{i,j}$$
(10)
where the local channel height and its time derivative (vertical velocity) are treated as known parameters from the previous time step. The boundary conditions (Eq. (2)) at the trailing and side edges are nonlinear with respect to φ. They are discretized with one-sided spatial derivatives and solved iteratively together with Eq. (1). For example, at the trailing edge (x1 = 0) the following numerical scheme is used,
$$2U\frac{-3{\varphi}_{1,j}+4{\varphi}_{2,j}-{\varphi}_{3,j}}{2\Delta x}-2\frac{\varphi_{1,j}-{\hat{\varphi}}_{1,j}}{\Delta t}-{\left(\frac{\partial \varphi }{\partial x}\right)}_{1,j}\frac{-3{\varphi}_{1,j}+4{\varphi}_{2,j}-{\varphi}_{3,j}}{2\Delta x}-{\left(\frac{\partial \varphi }{\partial z}\right)}_{1,j}\frac{\varphi_{1,j+1}-{\varphi}_{1,j-1}}{2\Delta z}=0$$
(11)
where $${\hat{\varphi}}_{i,j}$$ is the velocity potential value from the previous time step. The coefficients (∂φ/∂x)1, j and (∂φ/∂z)1, j are initially taken as known parameters from the previous step. Then, a linear system of equations (Eqs. (10), (11)) is solved for φi, j. The derivatives (∂φ/∂x)1, j and (∂φ/∂z)1, j are evaluated with this new solution and substituted back into Eq. (11). This process is repeated until a converged solution is obtained for the velocity potential at each time step.
The input parameters in the present model include the wing geometry, initial conditions, and the water surface elevations. Mesh-independence studies have been conducted to establish the adequate spatial step. The sensitivities of the lift coefficient, CL = 2L/(ρU2S), and the longitudinal center of pressure, xp, to the cell size, ∆x, for a selected ram wing (described in section 3) in the equilibrium flight are shown in Fig. 2. As one can see, having 20 spatial intervals along the chord (and the same number along the span for a ram wing with aspect ratio of one) is sufficient to obtain mesh-independent results; this mesh was employed for all parametric calculations presented below. In time-dependent simulations with varying time step ∆t, it was found that the condition ∆t = ∆x/(2U) is adequate; selecting shorter time steps does not produce a noticeable effect.
Most simulations in this study are conducted in the presence of low-amplitude water waves. The water surface elevations are described using the standard regular wave theory (Lewandowski 2004) in the reference frame translating along axis x with the vehicle speed U,
$${y}_w=A\ \sin \left[\omega t-k\left(x+ Ut\right)\ \cos \chi - kz\ \sin \chi \right]$$
(12)
where A is the wave amplitude, ω = 2π/T is the angular frequency, T is the period, k = 2π/λ = ω2/g is the wave number, λ is the wavelength, and χ is the direction of wave propagation in the Earth-fixed frame of reference (Fig. 1b), so that χ = 0° and χ = 180° correspond to the following and head waves, respectively. The wave amplitude is selected as A = λ/60, according to one of the common relationships for low-amplitude regular waves. Since the vehicle translation occurs at high Froude numbers, defined as $$Fr=U/\sqrt{gc}$$, an assumption commonly used for ground-effect vehicles is invoked that wave systems are not affected by the flying craft. It was shown by Barber (2007) that effects of the water surface deformations on the vehicle’s steady and unsteady aerodynamic coefficients are very small for typical non-augmented ram wings such as considered in this paper. However, these effects may need to be accounted for in case of power-augmented ram wings, especially at low Froude numbers.
The current mathematical model was previously validated for cases of steady flow around several configurations of ram wings in the extreme ground effect (Rozhdestvensky 2000; Matveev 2013), as well as for power augmented ram platforms hovering over solid ground and water (Matveev 2008; Matveev and Soderlund 2008). One validation example is given in the next section. No accurate measurements for unsteady motions of ram wings in the extreme ground effect are available in the technical literature, so conducting such experiments would represent a promising topic for future research.
## 3 Validation and Simulation Results
One validation example is shown here for the flat ram wing with side plates tested by Gallington and Miller (1970). The configuration with the main geometric parameters is shown in Fig. 3(a). The test data for the pressure coefficient on the wing lower surface and numerical predictions obtained with the present model are given in Fig. 3(b) for α = 5.7°, hp/c = 0.033, ht/c = 0.017, and the wing aspect ratio of 2/3. An agreement can be considered satisfactory keeping in mind unknown experimental uncertainties.
One representative configuration has been chosen in this study to illustrate dynamics of ram wings. The main specifications are listed in Table 1. The wing has an S-shaped lower surface (Fig. 1(a)) to ensure its stability without employing a tail wing (Matveev and Kornev 2013). The distance between the wing lower surface and the chord line is described by an equation yL(x) = − d sin (2πx/c). In the EGE theory, only lift on the lower side is accounted for so the upper side is not specified. In the equilibrium’s steady motion over a flat surface, the wing trailing edge gap is selected as yp(0)/c = 0.04, trim angle (between the chord line and horizontal plane) is α = 4°, and the lift coefficient is CL = 0.209. The center of gravity lies in the wing center plane, so the equilibrium roll angle is ψ = 0°.
Table 1
Main parameters of ram wing
Non-dimensional mass $$\mu =\frac{2M}{\rho w{c}^2}$$ 4 Non-dimensional moments of inertia $$i=\frac{I_{xx}}{M{c}^2}=\frac{I_{zz}}{M{s}^2}$$ 0.05 Longitudinal center of gravity $${X}_{\mathrm{cg}}=\frac{x_{\mathrm{cg}}}{c}$$ 0.637 Aspect ratio $$\mathrm{AR}=\frac{s}{c}$$ 1 Froude number $$Fr=\frac{U}{\sqrt{gc}}$$ 4.37 Profile curvature $$\frac{d}{c}$$ (Fig. 1a) 0.003
To demonstrate stability of the selected setup, time histories of the vehicle’s vertical position of the center of gravity and pitch and roll angles upon initial deviations from the equilibrium (∆ycg/c = 0.01, ∆α = 1°, ∆ψ = 1°) are shown in Fig. 4. The kinematic parameters approach the equilibrium values after a transient process. Initially, the altitude further increases since the pitch angle is greater than the equilibrium value. The pitch angle monotonically decreases to equilibrium (Fig. 4b), while the altitude initially increases due to a high pitch angle and then decreases (Fig. 4a). The roll motions show heavily damped oscillations.
A series of simulations has been carried out to model ram wing motions over regular water waves. Five different wave headings were explored ranging from the following waves (χ = 0°) to head waves (χ = 180°) with increments of 45°. The wavelength was set to three wing chords, λ/c = 3. At the start of simulations, the wing was assigned the equilibrium state. The wave amplitude was slowly increased from zero to the final value, A/λ = 1/60, to avoid any abrupt transient events. Eventually, the wing motions reached steady-state limit-cycle oscillations. Time variations of kinematic variables over three cycles in such regimes are illustrated in Fig. 5.
In case of the head and following wave headings (Fig. 5a–c), the frequency of vehicle’s encounter with waves is high (the highest is for head waves), since the effective wavelength with respect to the moving wing is short (Fig. 1a). The heave and pitch amplitudes are greater for the following waves than for the head waves, as in the former case the wing has longer time to react to variations of the underlying surface. The heave motions only slightly deviate from sinusoidal functions, while non-linear distortions are more pronounced in the pitch response. The roll motions are absent, since there is no disturbing moment with respect to the x-axis at parallel courses of waves and the vehicle. The time-averaged position of the vehicle is greater than that in flight over the flat surface (dashed lines in Fig. 5), implying that the time-averaged lift is higher. This nonlinear effect has been known to happen for wing-in-ground craft moving over wavy surfaces (Rozhdestvensky 2006).
Simulation results for situations with bow (χ = 145°) and quartering waves (χ = 45°) are shown in Fig. 4(d–f). The frequencies of encounter are smaller than in previous cases due to oblique wave headings with respect to the wing direction. The heave amplitudes are greater for the quartering seas, as well as the time-averaged heave and pitch. With the appearance of the heeling moment, the roll motions are also present (Fig. 5f).
Simulated motions for the case with beam waves (χ = 90°) are depicted in Fig. 5(g–i). The roll amplitudes are the highest at this wave heading (Fig. 5i). The heave and pitch motions are also present (Fig. 5(g–h)), since variations in the under-platform channel in the transverse z-direction also lead to variation of the total lift force and longitudinal center of pressure. The heave and pitch amplitudes are even greater than for other wave headings. However, the period of these oscillations is several times higher, as the vehicle speed is perpendicular to the wave heading, and the period is defined only by the wave speed. In the limit of long waves (low-frequency forcing), the vehicle would essentially follow the wave contour.
Besides the wave headings, the lengths and amplitudes of waves also affect the vehicle motions. Another set of simulations was conducted in this study for a range of wavelengths, while the amplitude was kept as the same fraction of wavelength, A = λ/60. With increasing the absolute wave height, it is possible to encounter situations when the vehicle will collide with the water surface, which in practice often leads to catastrophic consequences. Hence, it is important to know the maximum wavelength that will allow a wing to fly without contact the water. Results of simulations are presented in Fig. 6 in form of vehicle’s heave, pitch, and roll amplitudes normalized by the wave amplitude (for heave) and by the maximum wave slope kA (for pitch and roll), Since oscillations are not sinusoidal in large-amplitude waves, the effective amplitude of heave motion is defined as follows,
$${y}_1=\left[\max \left({y}_{\mathrm{cg}}(t)\right)-\min \left({y}_{\mathrm{cg}}(t)\right)\right]/2$$
(13)
where ycg(t) is the vertical position of the center of gravity over at least one period of oscillations in the limit-cycle regime. The amplitudes of pitch and roll motions are defined similar to Eq. (13).
For the chosen ram wing configuration, it was found that almost all wave headings (with the exception of beam waves) had maximum limiting wavelengths that allowed the wing not to touch water (Fig. 6). The smallest range of permissible wavelengths appears to be in head waves, as the wing does not have enough time to respond to the variation of the clearance and fly over the wave crests. The wave headings in order of increasing maximum permissible wavelength correspond to the bow, following, and quartering waves, respectively (Fig. 6). In case of the beam waves, the frequency of encounter is sufficiently small, so even in long and high waves, the vehicle has ample time to follow the wave contour without touching the surface, and its normalized heave and roll amplitudes approach one in the limit of very long waves.
Besides flying over surface waves, ram wings are likely to encounter other obstacles on the underlying surface, such as low-height islands and floating ice in water or ice ridges on ice sheets. The unsteady response of the wing to such non-uniformities can be also modeled with the current method. As an example, a triangular bump is considered here that may have variable orientation with respect to the vehicle heading (Fig. 7). The bump length and height are selected as L/c = 2 and H/c = 0.04, respectively, with two orientations, β = 0° and 60°.
The variations of the vehicle’s kinematic parameters are shown in Fig. 8. The non-dimensional time intervals tU/c with at least some portion of the wing being above the bump are 2–5 at orientation 0° and 0.13–6.87 at 60°. In both cases, the center of gravity moves up and then relaxes back to the equilibrium value with a small overshoot, and the heave motion is more pronounced for the longer-influencing oblique bump. The pitch response is similar but somewhat delayed in the beginning for β = 60°, and it is more oscillatory for β = 0° due to more abrupt disturbance. Also, oscillatory roll motions are present only for the oblique incidence, since one side the vehicle feels the bump presence earlier. Even though the bump height equals to the equilibrium flying height of the platform trailing edge (over the flat horizontal surface), no contact with ground occurs due to sufficient increase of the lift force resulting in the effective rise of the flying height.
## 4 Conclusions
A dynamic model for roll-heave-pitch motions of a ram wing has been developed using the extreme-ground-effect theory. It allows us to simulate motions of a vehicle flying over non-uniform surface. The model is computationally economical, since viscous effects are neglected and flow under the wing is considered to be two-dimensional.
The main conclusions of this paper include the following. The model is found to reasonably agree with test data for a ram wing in a steady condition. It is numerically confirmed that an S-shape of the wing lower surface can provide stability of tailless WIG craft. Nonlinear effects are more pronounced for pitch angles than other kinematic variables. The time-averaged vertical positions of the vehicle increase in the presence of waves in comparison with a flight above a flat surface. All motions (heave, pitch, and roll) have the greatest amplitudes in beam waves, although the oscillation periods are also longest in such conditions. The head waves are most dangerous from a collision standpoint, since a ram wing may not have enough time to respond to the water surface variation. Oblique course headings toward transverse obstacles on the ground can be recommended to reduce effective slopes of these obstacles along the vehicle direction.
The present model can be also used to evaluate motion amplitudes and occurrence of regimes when the wing touches water/ground. It can be extended by including other forces (e.g., thrust, drag), adding other degrees of freedom, introducing control surfaces (flaps), and simulating random waves and wind gusts. With incorporation of elements of the planing hull theory, one can possibly simulate takeoff and landing phases, as well as brief contacts between water and the wing flying in rough sea conditions.
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https://physics.stackexchange.com/questions/556890/speed-of-object-falling-into-a-black-hole-below-event-horizon
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Speed of object falling into a black hole, below event horizon
Suppose I am at rest at a great distance $$r_0$$ from a black hole with a mass $$M$$ without rotation or charge.
During my free fall in vacuum from $$\tau=0$$ and $$r=r_0$$, I will pass the event horizon in finite proper time and the increment of my proper time in Schwarzschild coordinates is $$\text{d}\tau=(2M/r-2M/r_0)^{-1/2}\,\text{d}r$$ (disregarding my destruction by tidal forces etc.)
If it is correct to view $$\frac{\text{d}r}{\text{d}\tau}=\sqrt{2M/r-2M/r_0}$$ as the locally measured speed, I would travel at $$v>c=1$$ shortly after passing the event horizon and before reaching $$r=0$$. But the locally measured speed of light is always $$c=1$$. This seems contradictory.
Where do I go wrong? Is it correct to say that $$\frac{\text{d}r}{\text{d}\tau}=\sqrt{2M/r-2M/r_0}$$ is the locally measured speed even within the event horizon and can this be greater than $$c=1$$?
I've read quite a few Q&A's in stackexchange, but I couldn't find and answer to this question.
• I've removed a number of comments that were attempting to answer the question and/or responses to them. Please keep in mind that comments should be used for suggesting improvements and requesting clarification on the question, not for answering. – David Z Jun 5 '20 at 0:08
The problem is that in GR coordinates do not necessarily have a physical meaning. They are just a way of labelling points in spacetime. For example the Schwarzschild coordinate $$r$$ is not a radial distance. It's actually the circumference of the circle centred on the black hole and passing through your point divided by $$2\pi$$. That is, it's what the radial distance would be if space were flat.
This means that the coordinate velocity $$dr/dt$$ also does not have a physical significance. You can certainly calculate $$dr/dt$$, e.g. for the observer at infinity, and you would find the coordinate velocity for that observer is:
$$v = \left(1 - \frac{r_s}{r}\right)\sqrt{\frac{r_s}{r}}c \tag{1}$$
giving the notorious result that the infalling object slows to a halt at the horizon.
Alternative you could ask what an observer hovering some distance $$r$$ (these are known as shell observers) would observe i.e. what speed would the falling object pass them. And in that case the result is:
$$v = \sqrt{\frac{r_s}{r}}c \tag{2}$$
and now we find that the speed the falling object passes the shell observer tends to $$c$$ as the shell observer approaches the horizon. The difference between the two results is due to the relative time dilation between the shell observer and the observer at infinity.
More generally the shell observer and the observer at infinity will always observe different velocities. If you're interested I go into this in detail in my answer to the question Does light really travel more slowly near a massive body? As explained in that answer the coordinate velocity can be greater than $$c$$ even outside the horizon, and this is because the coordinate velocity is not a physically meaningful quantity.
Now you are asking about the velocity inside the horizon, but this is even harder to discuss in any meaningful way. For any observer outside the horizon no object ever passes the horizon, so there is no velocity inside to observe. And inside the horizon it's impossible to stay at fixed $$r$$ so we cannot have any shell observers to watch the falling object flash past them. I guess the best we could do is ask how fast the infalling observer observes the singularity to be approaching, though note that this is theoretical since no light from the singularity could ever reach the observer's eye. And the answer that the speed would indeed exceed $$c$$ inside the horizon, though I must emphasise again that you shouldn't assign any physical sigificance to this.
• Comments are not for extended discussion; this conversation has been moved to chat. – David Z Jun 5 '20 at 0:08
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https://people.maths.bris.ac.uk/~matyd/GroupNames/288/SD16sD9.html
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## G = SD16⋊D9order 288 = 25·32
### 2nd semidirect product of SD16 and D9 acting via D9/C9=C2
Series: Derived Chief Lower central Upper central
Derived series C1 — C36 — SD16⋊D9
Chief series C1 — C3 — C9 — C18 — C36 — C4×D9 — Q8×D9 — SD16⋊D9
Lower central C9 — C18 — C36 — SD16⋊D9
Upper central C1 — C2 — C4 — SD16
Generators and relations for SD16⋊D9
G = < a,b,c,d | a8=b2=c9=d2=1, bab=a3, ac=ca, dad=a5, bc=cb, dbd=a4b, dcd=c-1 >
Subgroups: 396 in 90 conjugacy classes, 34 normal (all characteristic)
C1, C2, C2 [×2], C3, C4, C4 [×4], C22 [×2], S3, C6, C6, C8, C8, C2×C4 [×3], D4, D4, Q8, Q8 [×3], C9, Dic3 [×3], C12, C12, D6, C2×C6, M4(2), SD16, SD16, Q16 [×2], C2×Q8, C4○D4, D9, C18, C18, C3⋊C8, C24, Dic6 [×3], C4×S3 [×2], C2×Dic3, C3⋊D4, C3×D4, C3×Q8, C8.C22, Dic9, Dic9 [×2], C36, C36, D18, C2×C18, C8⋊S3, Dic12, D4.S3, C3⋊Q16, C3×SD16, D42S3, S3×Q8, C9⋊C8, C72, Dic18 [×2], Dic18, C4×D9, C4×D9, C2×Dic9, C9⋊D4, D4×C9, Q8×C9, D4.D6, Dic36, C8⋊D9, D4.D9, C9⋊Q16, C9×SD16, D42D9, Q8×D9, SD16⋊D9
Quotients: C1, C2 [×7], C22 [×7], S3, D4 [×2], C23, D6 [×3], C2×D4, D9, C22×S3, C8.C22, D18 [×3], S3×D4, C22×D9, D4.D6, D4×D9, SD16⋊D9
Smallest permutation representation of SD16⋊D9
On 144 points
Generators in S144
(1 140 32 122 14 131 23 113)(2 141 33 123 15 132 24 114)(3 142 34 124 16 133 25 115)(4 143 35 125 17 134 26 116)(5 144 36 126 18 135 27 117)(6 136 28 118 10 127 19 109)(7 137 29 119 11 128 20 110)(8 138 30 120 12 129 21 111)(9 139 31 121 13 130 22 112)(37 91 55 82 46 100 64 73)(38 92 56 83 47 101 65 74)(39 93 57 84 48 102 66 75)(40 94 58 85 49 103 67 76)(41 95 59 86 50 104 68 77)(42 96 60 87 51 105 69 78)(43 97 61 88 52 106 70 79)(44 98 62 89 53 107 71 80)(45 99 63 90 54 108 72 81)
(1 41)(2 42)(3 43)(4 44)(5 45)(6 37)(7 38)(8 39)(9 40)(10 46)(11 47)(12 48)(13 49)(14 50)(15 51)(16 52)(17 53)(18 54)(19 55)(20 56)(21 57)(22 58)(23 59)(24 60)(25 61)(26 62)(27 63)(28 64)(29 65)(30 66)(31 67)(32 68)(33 69)(34 70)(35 71)(36 72)(73 127)(74 128)(75 129)(76 130)(77 131)(78 132)(79 133)(80 134)(81 135)(82 136)(83 137)(84 138)(85 139)(86 140)(87 141)(88 142)(89 143)(90 144)(91 118)(92 119)(93 120)(94 121)(95 122)(96 123)(97 124)(98 125)(99 126)(100 109)(101 110)(102 111)(103 112)(104 113)(105 114)(106 115)(107 116)(108 117)
(1 2 3 4 5 6 7 8 9)(10 11 12 13 14 15 16 17 18)(19 20 21 22 23 24 25 26 27)(28 29 30 31 32 33 34 35 36)(37 38 39 40 41 42 43 44 45)(46 47 48 49 50 51 52 53 54)(55 56 57 58 59 60 61 62 63)(64 65 66 67 68 69 70 71 72)(73 74 75 76 77 78 79 80 81)(82 83 84 85 86 87 88 89 90)(91 92 93 94 95 96 97 98 99)(100 101 102 103 104 105 106 107 108)(109 110 111 112 113 114 115 116 117)(118 119 120 121 122 123 124 125 126)(127 128 129 130 131 132 133 134 135)(136 137 138 139 140 141 142 143 144)
(1 9)(2 8)(3 7)(4 6)(10 17)(11 16)(12 15)(13 14)(19 26)(20 25)(21 24)(22 23)(28 35)(29 34)(30 33)(31 32)(37 53)(38 52)(39 51)(40 50)(41 49)(42 48)(43 47)(44 46)(45 54)(55 71)(56 70)(57 69)(58 68)(59 67)(60 66)(61 65)(62 64)(63 72)(73 80)(74 79)(75 78)(76 77)(82 89)(83 88)(84 87)(85 86)(91 98)(92 97)(93 96)(94 95)(100 107)(101 106)(102 105)(103 104)(109 125)(110 124)(111 123)(112 122)(113 121)(114 120)(115 119)(116 118)(117 126)(127 143)(128 142)(129 141)(130 140)(131 139)(132 138)(133 137)(134 136)(135 144)
G:=sub<Sym(144)| (1,140,32,122,14,131,23,113)(2,141,33,123,15,132,24,114)(3,142,34,124,16,133,25,115)(4,143,35,125,17,134,26,116)(5,144,36,126,18,135,27,117)(6,136,28,118,10,127,19,109)(7,137,29,119,11,128,20,110)(8,138,30,120,12,129,21,111)(9,139,31,121,13,130,22,112)(37,91,55,82,46,100,64,73)(38,92,56,83,47,101,65,74)(39,93,57,84,48,102,66,75)(40,94,58,85,49,103,67,76)(41,95,59,86,50,104,68,77)(42,96,60,87,51,105,69,78)(43,97,61,88,52,106,70,79)(44,98,62,89,53,107,71,80)(45,99,63,90,54,108,72,81), (1,41)(2,42)(3,43)(4,44)(5,45)(6,37)(7,38)(8,39)(9,40)(10,46)(11,47)(12,48)(13,49)(14,50)(15,51)(16,52)(17,53)(18,54)(19,55)(20,56)(21,57)(22,58)(23,59)(24,60)(25,61)(26,62)(27,63)(28,64)(29,65)(30,66)(31,67)(32,68)(33,69)(34,70)(35,71)(36,72)(73,127)(74,128)(75,129)(76,130)(77,131)(78,132)(79,133)(80,134)(81,135)(82,136)(83,137)(84,138)(85,139)(86,140)(87,141)(88,142)(89,143)(90,144)(91,118)(92,119)(93,120)(94,121)(95,122)(96,123)(97,124)(98,125)(99,126)(100,109)(101,110)(102,111)(103,112)(104,113)(105,114)(106,115)(107,116)(108,117), (1,2,3,4,5,6,7,8,9)(10,11,12,13,14,15,16,17,18)(19,20,21,22,23,24,25,26,27)(28,29,30,31,32,33,34,35,36)(37,38,39,40,41,42,43,44,45)(46,47,48,49,50,51,52,53,54)(55,56,57,58,59,60,61,62,63)(64,65,66,67,68,69,70,71,72)(73,74,75,76,77,78,79,80,81)(82,83,84,85,86,87,88,89,90)(91,92,93,94,95,96,97,98,99)(100,101,102,103,104,105,106,107,108)(109,110,111,112,113,114,115,116,117)(118,119,120,121,122,123,124,125,126)(127,128,129,130,131,132,133,134,135)(136,137,138,139,140,141,142,143,144), (1,9)(2,8)(3,7)(4,6)(10,17)(11,16)(12,15)(13,14)(19,26)(20,25)(21,24)(22,23)(28,35)(29,34)(30,33)(31,32)(37,53)(38,52)(39,51)(40,50)(41,49)(42,48)(43,47)(44,46)(45,54)(55,71)(56,70)(57,69)(58,68)(59,67)(60,66)(61,65)(62,64)(63,72)(73,80)(74,79)(75,78)(76,77)(82,89)(83,88)(84,87)(85,86)(91,98)(92,97)(93,96)(94,95)(100,107)(101,106)(102,105)(103,104)(109,125)(110,124)(111,123)(112,122)(113,121)(114,120)(115,119)(116,118)(117,126)(127,143)(128,142)(129,141)(130,140)(131,139)(132,138)(133,137)(134,136)(135,144)>;
G:=Group( (1,140,32,122,14,131,23,113)(2,141,33,123,15,132,24,114)(3,142,34,124,16,133,25,115)(4,143,35,125,17,134,26,116)(5,144,36,126,18,135,27,117)(6,136,28,118,10,127,19,109)(7,137,29,119,11,128,20,110)(8,138,30,120,12,129,21,111)(9,139,31,121,13,130,22,112)(37,91,55,82,46,100,64,73)(38,92,56,83,47,101,65,74)(39,93,57,84,48,102,66,75)(40,94,58,85,49,103,67,76)(41,95,59,86,50,104,68,77)(42,96,60,87,51,105,69,78)(43,97,61,88,52,106,70,79)(44,98,62,89,53,107,71,80)(45,99,63,90,54,108,72,81), (1,41)(2,42)(3,43)(4,44)(5,45)(6,37)(7,38)(8,39)(9,40)(10,46)(11,47)(12,48)(13,49)(14,50)(15,51)(16,52)(17,53)(18,54)(19,55)(20,56)(21,57)(22,58)(23,59)(24,60)(25,61)(26,62)(27,63)(28,64)(29,65)(30,66)(31,67)(32,68)(33,69)(34,70)(35,71)(36,72)(73,127)(74,128)(75,129)(76,130)(77,131)(78,132)(79,133)(80,134)(81,135)(82,136)(83,137)(84,138)(85,139)(86,140)(87,141)(88,142)(89,143)(90,144)(91,118)(92,119)(93,120)(94,121)(95,122)(96,123)(97,124)(98,125)(99,126)(100,109)(101,110)(102,111)(103,112)(104,113)(105,114)(106,115)(107,116)(108,117), (1,2,3,4,5,6,7,8,9)(10,11,12,13,14,15,16,17,18)(19,20,21,22,23,24,25,26,27)(28,29,30,31,32,33,34,35,36)(37,38,39,40,41,42,43,44,45)(46,47,48,49,50,51,52,53,54)(55,56,57,58,59,60,61,62,63)(64,65,66,67,68,69,70,71,72)(73,74,75,76,77,78,79,80,81)(82,83,84,85,86,87,88,89,90)(91,92,93,94,95,96,97,98,99)(100,101,102,103,104,105,106,107,108)(109,110,111,112,113,114,115,116,117)(118,119,120,121,122,123,124,125,126)(127,128,129,130,131,132,133,134,135)(136,137,138,139,140,141,142,143,144), (1,9)(2,8)(3,7)(4,6)(10,17)(11,16)(12,15)(13,14)(19,26)(20,25)(21,24)(22,23)(28,35)(29,34)(30,33)(31,32)(37,53)(38,52)(39,51)(40,50)(41,49)(42,48)(43,47)(44,46)(45,54)(55,71)(56,70)(57,69)(58,68)(59,67)(60,66)(61,65)(62,64)(63,72)(73,80)(74,79)(75,78)(76,77)(82,89)(83,88)(84,87)(85,86)(91,98)(92,97)(93,96)(94,95)(100,107)(101,106)(102,105)(103,104)(109,125)(110,124)(111,123)(112,122)(113,121)(114,120)(115,119)(116,118)(117,126)(127,143)(128,142)(129,141)(130,140)(131,139)(132,138)(133,137)(134,136)(135,144) );
G=PermutationGroup([(1,140,32,122,14,131,23,113),(2,141,33,123,15,132,24,114),(3,142,34,124,16,133,25,115),(4,143,35,125,17,134,26,116),(5,144,36,126,18,135,27,117),(6,136,28,118,10,127,19,109),(7,137,29,119,11,128,20,110),(8,138,30,120,12,129,21,111),(9,139,31,121,13,130,22,112),(37,91,55,82,46,100,64,73),(38,92,56,83,47,101,65,74),(39,93,57,84,48,102,66,75),(40,94,58,85,49,103,67,76),(41,95,59,86,50,104,68,77),(42,96,60,87,51,105,69,78),(43,97,61,88,52,106,70,79),(44,98,62,89,53,107,71,80),(45,99,63,90,54,108,72,81)], [(1,41),(2,42),(3,43),(4,44),(5,45),(6,37),(7,38),(8,39),(9,40),(10,46),(11,47),(12,48),(13,49),(14,50),(15,51),(16,52),(17,53),(18,54),(19,55),(20,56),(21,57),(22,58),(23,59),(24,60),(25,61),(26,62),(27,63),(28,64),(29,65),(30,66),(31,67),(32,68),(33,69),(34,70),(35,71),(36,72),(73,127),(74,128),(75,129),(76,130),(77,131),(78,132),(79,133),(80,134),(81,135),(82,136),(83,137),(84,138),(85,139),(86,140),(87,141),(88,142),(89,143),(90,144),(91,118),(92,119),(93,120),(94,121),(95,122),(96,123),(97,124),(98,125),(99,126),(100,109),(101,110),(102,111),(103,112),(104,113),(105,114),(106,115),(107,116),(108,117)], [(1,2,3,4,5,6,7,8,9),(10,11,12,13,14,15,16,17,18),(19,20,21,22,23,24,25,26,27),(28,29,30,31,32,33,34,35,36),(37,38,39,40,41,42,43,44,45),(46,47,48,49,50,51,52,53,54),(55,56,57,58,59,60,61,62,63),(64,65,66,67,68,69,70,71,72),(73,74,75,76,77,78,79,80,81),(82,83,84,85,86,87,88,89,90),(91,92,93,94,95,96,97,98,99),(100,101,102,103,104,105,106,107,108),(109,110,111,112,113,114,115,116,117),(118,119,120,121,122,123,124,125,126),(127,128,129,130,131,132,133,134,135),(136,137,138,139,140,141,142,143,144)], [(1,9),(2,8),(3,7),(4,6),(10,17),(11,16),(12,15),(13,14),(19,26),(20,25),(21,24),(22,23),(28,35),(29,34),(30,33),(31,32),(37,53),(38,52),(39,51),(40,50),(41,49),(42,48),(43,47),(44,46),(45,54),(55,71),(56,70),(57,69),(58,68),(59,67),(60,66),(61,65),(62,64),(63,72),(73,80),(74,79),(75,78),(76,77),(82,89),(83,88),(84,87),(85,86),(91,98),(92,97),(93,96),(94,95),(100,107),(101,106),(102,105),(103,104),(109,125),(110,124),(111,123),(112,122),(113,121),(114,120),(115,119),(116,118),(117,126),(127,143),(128,142),(129,141),(130,140),(131,139),(132,138),(133,137),(134,136),(135,144)])
39 conjugacy classes
class 1 2A 2B 2C 3 4A 4B 4C 4D 4E 6A 6B 8A 8B 9A 9B 9C 12A 12B 18A 18B 18C 18D 18E 18F 24A 24B 36A 36B 36C 36D 36E 36F 72A ··· 72F order 1 2 2 2 3 4 4 4 4 4 6 6 8 8 9 9 9 12 12 18 18 18 18 18 18 24 24 36 36 36 36 36 36 72 ··· 72 size 1 1 4 18 2 2 4 18 36 36 2 8 4 36 2 2 2 4 8 2 2 2 8 8 8 4 4 4 4 4 8 8 8 4 ··· 4
39 irreducible representations
dim 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 4 4 4 4 4 type + + + + + + + + + + + + + + + + + + - + - + - image C1 C2 C2 C2 C2 C2 C2 C2 S3 D4 D4 D6 D6 D6 D9 D18 D18 D18 C8.C22 S3×D4 D4.D6 D4×D9 SD16⋊D9 kernel SD16⋊D9 Dic36 C8⋊D9 D4.D9 C9⋊Q16 C9×SD16 D4⋊2D9 Q8×D9 C3×SD16 Dic9 D18 C24 C3×D4 C3×Q8 SD16 C8 D4 Q8 C9 C6 C3 C2 C1 # reps 1 1 1 1 1 1 1 1 1 1 1 1 1 1 3 3 3 3 1 1 2 3 6
Matrix representation of SD16⋊D9 in GL6(𝔽73)
1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 66 13 0 0 0 0 13 7 0 0 13 7 0 0 0 0 7 60 0 0
,
1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0
,
42 45 0 0 0 0 28 70 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 1
,
42 70 0 0 0 0 28 31 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 0 0 72 0 0 0 0 0 0 72
G:=sub<GL(6,GF(73))| [1,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,13,7,0,0,0,0,7,60,0,0,66,13,0,0,0,0,13,7,0,0],[1,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0],[42,28,0,0,0,0,45,70,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,1],[42,28,0,0,0,0,70,31,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,72,0,0,0,0,0,0,72] >;
SD16⋊D9 in GAP, Magma, Sage, TeX
{\rm SD}_{16}\rtimes D_9
% in TeX
G:=Group("SD16:D9");
// GroupNames label
G:=SmallGroup(288,125);
// by ID
G=gap.SmallGroup(288,125);
# by ID
G:=PCGroup([7,-2,-2,-2,-2,-2,-3,-3,120,422,135,346,185,80,6725,292,9414]);
// Polycyclic
G:=Group<a,b,c,d|a^8=b^2=c^9=d^2=1,b*a*b=a^3,a*c=c*a,d*a*d=a^5,b*c=c*b,d*b*d=a^4*b,d*c*d=c^-1>;
// generators/relations
×
𝔽
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https://www.physicsforums.com/threads/qed-coherence-in-matter.217809/
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# QED coherence in matter
1. Feb 25, 2008
### mgb2
Hi,
I would like to know what do you think about the Giuliano Preparata theory on QED coherence in matter.
He studied the problem of the ground state in condensed matter under the hypotesis that the standard perturbative vacuum is unstable with respect to a new coherent vacuum, whose spectrum emerge quite naturally through a simple variational procedure.
https://www.amazon.com/Introduction-Realistic-Quantum-Physics/dp/9812381767#cited
https://www.amazon.com/Qed-Coherence-Matter-Giuliano-Preparata/dp/9810222491
Ciao
mgb2
#### Attached Files:
• ###### del giudice.pdf
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Last edited: Feb 25, 2008
2. Feb 27, 2008
### mgb2
But, is never possible that nobody of you is interested in this new way to watch to the reality of the world (without introducing new concepts, of course) ?
Just looking at interaction and dynamical evolution between matter and e.m. field in terms of quantized matter-wave-field and quantized e.m.-wave-field.
If you consider a piece of matter (N=10^23 but described by a field) what is the effect of interaction with the zero point energy fluctuations of the e.m. field??
What happens when the electric dipole moment field interact with e.m. field?
look at the article!!
Ciao
mgb2
#### Attached Files:
• ###### Srivastava.pdf
File size:
116.7 KB
Views:
152
Last edited: Feb 27, 2008
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https://forum.allaboutcircuits.com/threads/circuit-analysis-help.63892/
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# Circuit analysis help
#### geft
Joined Dec 8, 2011
19
I'm having a hard time finding V2 in terms of I2. I've tried various forms of KCL and KVL but I can't seem to find the right answer. I hope someone can enlighten me.
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Last edited:
#### jegues
Joined Sep 13, 2010
733
Can you show us your work?
Then we can further diagnose what the problem is and point you in the right direction.
#### geft
Joined Dec 8, 2011
19
$$I_2 = \frac{V_2-2V_x}{2} + \frac{V_2}{5} = \frac{V_2-2\frac{V_2}{4}}{2} + \frac{V_2}{5} = 0.45V_2$$
$$Z_{22} = \frac{V_2}{I_2} = \frac{V_2}{0.45V_2} = 2.222$$
This is clearly wrong since the answer is supposed to be 1.111 ohm.
Last edited:
#### Zazoo
Joined Jul 27, 2011
114
$$I_2 = \frac{V_2-2V_x}{2} + \frac{V_2}{5} = \frac{V_2-2\frac{V_2}{4}}{2} + \frac{V_2}{5} = 0.45V_2$$
$$Z_{22} = \frac{V_2}{I_2} = \frac{V_2}{0.45V_2} = 2.222$$
This is clearly wrong since the answer is supposed to be 1.111 ohm.
My node equation is:
$$I_2 = \frac{V_2-(-2V_x)}{2} + \frac{V_2}{5} = \frac{V_2+2V_2(\frac{1}{1+4})}{2} + \frac{V_2}{5} = 0.9V_2$$
Current direction was chosen as leaving the node for both branches.
Note the polarity on the dependent voltage source.
Also, Vx can be replaced by the expression for a 1Ω and 4Ω voltage divider (making it 1/5 V2)
This gives 1.111ohms when used in the second equation.
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https://offshoremechanics.asmedigitalcollection.asme.org/thermalscienceapplication/article/12/6/061006/1082082/A-Modified-Correlation-for-Flow-Boiling-Heat
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## Abstract
Corrugated plate heat exchangers are increasingly used in two-phase flow applications for their flexible compact size and efficient heat transfer performance. This paper presents a brief review of recent studies on the flow boiling in plate heat exchangers and creates a database containing 533 data points from previous experimental studies. The collected database covers seven working fluids, a wide range of vapor quality (both mean and local) 0.01–0.94, heat flux 0.5–46 kW m−2, mass flux 5.5–137 kg m−2 s−1, chevron angle 30–70 deg, and hydraulic diameter 1.7–4.0 mm. Based on the database a brief comparison between several previous correlations are discussed. A new prediction method for flow boiling heat transfer coefficient is developed by multiple regression analysis and modifying an existing correlation. A criterion proposed by Li and Wu about the transition from micro- to macroscale was introduced with a combined dimensionless number Bd·Rel0.5 which attempts to comprehensively consider four types of forces during flow boiling. It was observed that the modified correlation shows a better agreement and predicts 74.3% and 94.9% of total data points within ±30% and ±50% error bands, respectively.
## 1 Introduction
Plate heat exchangers (PHEs) are a type of industrial compact heat exchangers consisting of a certain number of corrugated thin metal plates. Since they provide obvious advantages over shell and tube heat exchangers, PHEs are widely used in various industries such as refrigeration, air-conditioning, food processing, chemical industry, marine, power, and energy generation systems. The corrugated plates promote the flow turbulence at relatively low Reynolds number, which helps in the disruption of the boundary layer thus contributing to better thermal performance. The high-surface area to volume ratio leads itself to be used in limited spaces and reduces the refrigerant charge. As presented in Amalfi et al. [1], commercial PHEs can be mainly divided into four types: gasketed, brazed, welded/semi-welded, and shell-and-plate. By simply adding/removing plates, PHEs can accommodate a wide band of application requirements. The drawback is that they are limited to by temperature and pressure combination, prone to fouling in harsh media and has higher maintenance cost compared to shell and tube heat exchangers.
The geometry of the corrugated plate (see Fig. 1) is mainly characterized by the chevron angle (β), the corrugation pitch (λ), and the amplitude of surface corrugation (a). It needs to be pointed out that the pitch between two plates b is twice the length of the amplitude of surface corrugation a. The calculations of geometric parameters will follow the definitions in Amalfi et al. [1,2] and in order not to cause confusion some of the nomenclature have changed in this paper.
Fig. 1
Fig. 1
Close modal
The corrugation aspect ratio γ and the enlargement factor φ can describe the severity of sinusoidal surface waviness:
$γ=4aλ=2bλ$
(1)
$φ=effectiveareaprojectedarea=∫0λ1+(γπ2)2cos2(2πλx)dxλ$
(2)
For engineering calculations, the enlargement factor φ can be obtained approximately from a three-point integration formula, using a dimensionless corrugation parameter Λ:
$φ(Λ)≈16(1+1+Λ2+41+Λ2/2)$
(3)
$Λ=2πaλ$
(4)
And the effective hydraulic diameter dh is usually given as a characteristic length:
$dh=4aφ=2bφ$
(5)
Furthermore, as defined in Solotych et al. [4], L and A indicate the wavelength and amplitude of the surface corrugation, respectively, and the chevron angle B is followed by two numbers depending on the symmetric or mixed plate arrangement.
The heat transfer of flow boiling in plate heat exchangers is a function of various factors, including mass flux, heat flux, vapor quality, evaporation temperature, and geometric parameters. The corrugated channels between plates enhance the heat transfer and complicate the prediction of the heat transfer coefficient. Consequently, there is no widely accepted model to describe the flow boiling mechanism and estimate the heat transfer coefficient until now [1,5]. This paper reviews the recent studies on the flow boiling in plate heat exchangers in Sec. 2. A database containing 533 data points was established for a new correlation by collecting existing experimental results from literatures. A new criterion about the transition from micro- to macroscale based on this paper authors’ previous studies [6] was introduced into the development of the correlation, and it was observed that this correlation showed better accuracy compared with the correlations in the literature.
## 2 Literature Review
The flow boiling heat transfer in plate heat exchangers is the result of nucleate boiling and forced convective boiling [7]. The dominant heat transfer regime varies with the increasing vapor quality, and the single-phase flow occurs at a high vapor quality after dry-out. However, so far there is no universal conclusion to indicate how these mechanisms work during flow boiling in PHEs. Some of the published work concluded that the nucleate boiling plays a dominant role [5,6], while other work concluded that the main mechanism is forced convective boiling [812]. In the nucleate boiling region, the heat transfer coefficient is mainly dependent on heat flux, while in the forced convection region, the heat transfer coefficient is mainly dependent on the vapor quality and the mass flux [7]. Moreover, others considered both contribute to the heat transfer of flow boiling inside PHEs [1315]. The nucleate boiling is usually associated with experiments carried out at low mass flux, while forced convective boiling is associated with experiments carried out at high mass flux in some researches [13,16]. Additionally, experimental results showed the dry-out mechanism at high vapor quality has a notable influence on the heat transfer process [17,18], especially near the micro–macroscale transition [19].
Kim et al. [17] conducted an experiment about the influence of heat transfer performance with different chevron angles. They found the higher chevron angles could significantly increase the heat transfer coefficient. Panchal et al. [20] also investigated the flow boiling of ammonia and R22 in various PHEs with different chevron angles. They got a similar conclusion that plates with higher chevron angles provided more efficient heat transfer. Han et al. [10] investigated R410A and R22 using PHEs with various chevron angles (20 deg, 35 deg, and 45 deg) then got the similar conclusion that the heat transfer coefficient increased with mass flux, vapor quality, and chevron angles, but decreased with saturation temperature. Recently, Elmaaty et al. [21] reviewed some literatures related to PHE and explicated some basic concepts of geometric parameters. They improved pervious correlation and proposed the Nusselt number was increasing with increase of chevron angle between 30 deg and 60 deg. Engelhorn and Reinhart [22] tested a plate heat exchanger as evaporator with working fluid R22 and found that the heat transfer coefficient increased with heat flux and mass flux and decreased with evaporation temperature. The group of Lin [13,23] conducted a series of experimental studies with R134a and R410A on heat transfer coefficient and pressure drop in a single-channel-brazed PHE with chevron angle 60 deg. Their results showed that the heat transfer coefficient in PHE was higher than that for a circular pipe even at a lower mass flux under similar conditions. At high vapor quality, the difference was quite notable, and they attributed the phenomenon to forced convective boiling dominance and highly turbulent flow. However, they observed that there was no significant effect of saturation temperature on the heat transfer coefficient. Danilova et al. [24] conducted one of the first studies on flow boiling in plate heat exchangers, testing refrigerants R12, R22, R113, and ammonia. They found that the heat transfer coefficient increased almost linearly with vapor quality and refrigerant mass flux, while the heat flux only had a weak effect on the heat transfer coefficient. They created an early correlation using Nusselt number and Bond number for evaporation heat transfer in PHEs. Huang et al. [25] investigated the performance characteristics of plate heat exchangers used as liquid over-feed evaporators with the fluids R12, R134a, R507a, and ammonia. They proposed that nucleate boiling regime dominated the flow boiling and therefore the heat transfer coefficient was strongly related to the imposed heat flux, while mass flux and vapor quality had a moderate effect on heat transfer. Ayub [8] made a detailed research regarding heat transfer and the fluid flow characteristics of different exchangers, and showed that the heat transfer coefficient was more mass flux driven rather than heat flux.
With the concern of environment issues during the last decades, the use of chloro-fluoro-carbons (CFCs) and hydro-chloro-fluoro-carbons (HCFCs) such as R12 and R22 has been either fully banned or stricter regulations have been imposed for the Montreal Protocol. This therefore leads to a fact that further work needs to be undertaken to study the performance characteristics of newer environment friendly refrigerants. Meanwhile, a few new techniques (e.g., infrared thermography) have been developed for high resolution and accuracy measurements, which could provide useful approaches to study flow boiling within PHEs. Longo’s group [2629] conducted extensive experiments to investigate heat transfer in a brazed PHE with numerous refrigerants: R134a, R410A, R236fa, R600a (isobutane), R290 (propane), R1270 (propylene), and R1234yf. In their work heat transfer coefficient showed a weak sensitivity to the system pressure and great sensitivity to the heat flux and outlet conditions. Also, their results presented good agreement with the Cooper and Gorenflo model [30] which were developed for tubular flows. Solotych et al. [4] used an infrared camera to measure the local heat transfer coefficient of the dielectric fluid HFE7100 within two specially fabricated plate heat exchangers. Adiabatic flow visualizations were conducted to link the flow patterns with the observed heat transfer. It was observed that the maximum heat transfer coefficient occurred upstream of the contact points of the corrugations, while the minimum was at the contact points. Lee et al. [11] investigated the performance of low global warming potential (GWP) refrigerants R1233zd(E) and R245fa. They concluded that the heat transfer coefficient showed a strong dependence on mass flux and vapor quality and not on the heat flux and saturation temperature due to the convective boiling regime. Kim et al. [17] similarly made a comparative characteristic evaluation of R1234ze(E) and R134a in PHEs and developed an empirical correlation. Vakili-Farahani et al. [3,31] also used an infrared radiation (IR) camera to investigate upward flow boiling heat transfer with high resolution and obtained heat transfer data of R245fa in the PHE in three different manners: mean (all over the plate), local (pixel-by-pixel), and quasi-local “window”(six locations along the flow direction). Based on their experimental results, the quasi-local data points were predicted well by the Hsieh and Lin [23] method and a newly modified version of the Danilova et al. [24] method. In further experimental studies, Amalfi et al. [32] concluded that the local flow boiling heat transfer coefficients were found to increase with mass flux, heat flux, and saturation temperature while rising, leveling off and then decreasing with increasing vapor quality. Zhang et al. [33] conducted comparative experiments of R134a, R1234yf, and R1234ze in a plate heat exchanger used for the evaporator of the organic Rankine cycle. The experimental results indicated that heat transfer coefficients were strongly dependent on the heat flux and saturation temperature. Besides, in terms of the thermal-hydraulic performance in a plate heat exchanger, they concluded that R1234yf was a suitable replacement of R134a due to the higher heat transfer coefficient and lower pressure drop.
In recent several years, some work was made for comprehensive literature reviews and widely available correlations. Eldeeb et al. [7] conducted an extensive survey of correlations for heat transfer coefficient and pressure drop of evaporation and condensation in PHEs during past decades. Longo et al. [14] collected 251 previous experimental data points and proposed a simplified criterion on whether nucleate boiling or convective boiling dominance. Their model was verified by a set of 505 experimental data points of various refrigerants. Amalfi et al. [1] presented a systematic review of numerous published papers and then proposed a general prediction method to estimate flow boiling heat transfer coefficient and two-phase frictional pressure drop based on a consolidated databank of 3416 data points collected from open literatures. The heat transfer correlations derived from dimensional analysis and their new model were broken down into macro- or micro-scale methods with Bond number criterion. It showed a good potential in estimating the thermal performance of different refrigerants inside PHEs, and the experiment data of Rossato et al. [18] displayed a good agreement with this model for R32, except for the effect of dry-out mechanism. Recently, Ayub et al. [34] carried out a review of the existing evaporation heat transfer experimental data of three refrigerants R717 (ammonia), R134a, and R410A and developed a simplified Nusselt number correlation that showed better agreement with previous studies and manufacturers’ data versus Amalfi et al. [1] model. Detailed summaries of previous correlations were available from Eldeeb et al. [7] and Ayub et al. [34].
The existing survey showed a strong demand for a well-accepted correlation for the design and selection of plate heat exchanges. This paper makes a similar contribution just as Ayub et al. [34] and develops a modified two-phase Nusselt number correlation based on the analysis of a database covering the experimental data points of seven refrigerants. In the research of Amalfi et al. [1], the transition criterion from macro- to micro-scale was at a Bond number Bd = 4, which was suggested by Kew and Cornwell [35] for the investigation of heat transfer in tubular channels. In 2010, Li and Wu [36] presented a better criterion for flow boiling heat transfer inside macro/microchannels with a combined dimensionless number Bd·Rel0.5: microscale when Bd·Rel0.5 ≤ 200. In this paper, a modified correlation was introduced with the new criterion in PHEs; meanwhile, the coefficients and exponents have changed for the simulations of some new data points.
## 3 Database Description
A database containing 533 data points was established by collecting experimental results from nine different papers, most of whom were published recently [1012,1719,3133]. Almost all the experiments were conducted with contemporary apparatus, and the results had satisfactory uncertainties. Figure 2 illustrates the distribution of all the data points with respect to refrigerant type, hydraulic diameter dh, heat flux q, chevron angle β, mass flux G, and vapor quality x. The database covers seven refrigerants: R717 (ammonia), R134a, R245fa, R1233zd(E), R1234ze(E), R32, and R410A. All properties of the refrigerants refer to NIST REFPROP Version 9.1 [37]. The experimental conditions vary in the following ranges: hydraulic diameter from 1.7 to 4 mm, chevron angle from 30 deg to 70 deg, vapor quality from 0.01 to 0.94, mass flux from 5.5 to 137 kg m−2 s−1, heat flux from 0.5 to 46 kW m−2, and evaporation pressure from 0.11 to 2.12 MPa. The data points from the previous investigation shown in Table 1.
Fig. 2
Fig. 2
Close modal
Table 1
Previous investigation used in the establishment of the database
AuthorRefrigerantsGeometric parametersn
Han et al. [10]R410AL4.9A1.1B70-70; L5.2A1.1B55-55; L7.0A1.1B45-4551
Kim et al. [17]R1234ze(E)L7.5A0.97B30-30/60-60102
Kim et al. [19]R134aL7.0A1.0B65-6542
Lee et al. [11]R1233zd(E)L7.5A0.97B60-6059
Lee et al. [11]R245faL7.5A0.97B60-6010
Vakili-Farahani et al. [31]R245faL3.7A0.5B65-65110
Amalfi et al. [32]R245faL3.7A0.5B65-6547
Khan et al. [12]AmmoniaL6.25A1.1B30-3047
Rossato et al. [18]R32L4.6A0.73B60-6026
Zhang et al. [33]R134aL7.0A1.0B65-6539
AuthorRefrigerantsGeometric parametersn
Han et al. [10]R410AL4.9A1.1B70-70; L5.2A1.1B55-55; L7.0A1.1B45-4551
Kim et al. [17]R1234ze(E)L7.5A0.97B30-30/60-60102
Kim et al. [19]R134aL7.0A1.0B65-6542
Lee et al. [11]R1233zd(E)L7.5A0.97B60-6059
Lee et al. [11]R245faL7.5A0.97B60-6010
Vakili-Farahani et al. [31]R245faL3.7A0.5B65-65110
Amalfi et al. [32]R245faL3.7A0.5B65-6547
Khan et al. [12]AmmoniaL6.25A1.1B30-3047
Rossato et al. [18]R32L4.6A0.73B60-6026
Zhang et al. [33]R134aL7.0A1.0B65-6539
The working fluids selected in this paper as shown in Fig. 2(a) are mostly the replacements for R12, R22, etc. In Fig. 2(b), hydraulic diameter of PHEs mainly lies in the range 1.5–2.0 mm and 3.0–3.5 mm. As shown in Figs. 2(d) and 2(e), more than 78% of total data points fall in the heat flux range less than 10 kW m−2, and about 90% of data points fall in the mass flux range from 5 to 60 kg m−2 s−1. The distribution of the database against the chevron angle is presented in Fig. 2(c). Most of plate heat exchangers in this paper are 30 deg, 60 deg, and 65 deg, and the maximum is 70 deg. Furthermore, from Fig. 2(f), 42.4% of data points refer to the local vapor quality while 57.6% to the mean vapor quality. The data points referring to local vapor quality were mainly from Vakili-Farahani et al. [31], Lee et al. [11], and Amalfi et al. [32]. The range of local vapor quality is mostly less than 0.5, while mean vapor quality has a wide range from 0.08 to 0.94.
Typically, the Bond number is a measure of body forces compared to surface-tension forces, defined as follows in two-phase flow:
$Bd=(ρl−ρv)gdh2σ$
(6)
The transition from micro- to macroscale was at a Bond number Bd = 4 as suggested by Kew and Cornwell [35]. The Bond number range of data points is from 2.6 to 38: 61.7% macroscale (Bd > 4) while 38.3% micro-scale (Bd ≤ 4). However, as suggested by Li and Wu [36], a combination dimensionless number Bd·Rel0.5 shows a comprehensive description of four forces related to two-phase flow: surface tension, gravitational, inertia, and viscous forces. The Rel is liquid Reynolds number reflecting the measure of inertia forces to viscous forces:
$Rel=G(1−x)dhμl$
(7)
The range of Bd·Rel0.5 is from 11 to 2100 and the Bd·Rel0.5 versus Bond number is shown in Fig. 3. In this database, only 36.0% of points fall in the range Bd·Rel0.5 > 200, although 61.7% have Bond numbers greater than 4.0. This phenomenon is likely caused by a low mass flux or a high vapor quality, so that the effect of liquid surface tension cannot be negligible despite the large hydraulic diameters. The criterion from micro- to macroscale for flow boiling heat transfer inside tubular channels was at Bd·Rel0.5 1= 200 based on the investigation of a wide range of data points [36]. In this paper, an attempt is made to modify the new criterion in plate heat exchangers.
Fig. 3
Fig. 3
Close modal
## 4 A Modified Heat Transfer Correlation
As mentioned in Ayub et al. [34], numerous correlations in PHEs were proposed during past several decades while different correlations give noticeable differences for the same dataset. The proposed correlations based upon their own data usually have limited use.
In order to propose a new correlation for predicting the heat transfer coefficient, many parameters need to be taken into account, such as the chevron angle β, hydraulic diameter dh, destiny of the liquid phase ρl and the vapor phase ρv, surface tension σ and so on. Amalfi et al. [1] proposed a general heat transfer correlation for flow boiling inside PHEs based on 1903 collected data points covering a wide range of conditions, and it showed a good potential in estimating the thermal performance of different fluids in PHEs:
$Nu=982β*1.101Wem0.315Bo0.320ρ*−0.224,Bd<4Nu=18.495β*0.248Rev0.135Relo0.351Bd0.235Bo0.198ρ*−0.223,Bd>4$
(8)
They found if the Bond number was less than 4, which means the channel is in microscale, the Nusselt number was associated with the homogeneous Weber number, Boiling number, density ratio, and the chevron angle. While the Bond number was greater than 4, it means the channel is in macroscale, the heat and mass transfer is driven by the same dimensionless numbers as microscale except the homogeneous Weber number, which is replaced by vapor Reynolds number and liquid only Reynolds numbers. The detailed analysis about the effect of the geometry parameters or operation conditions on heat transfer characteristics and the mechanisms of mass and heat transfer is presented in the published literature of them. Recent studies such as Rossato et al. [18] showed good agreement with their correlation. Nevertheless, others concluded that it overestimated or underestimated the heat transfer coefficient [33,19]. For the database used in this paper, several brief comparisons of correlation are presented in Fig. 4.
Fig. 4
Fig. 4
Close modal
The correlation above predicted the most points (75%) within ±50% error band; however, the existing error may be still considerable for the utilization of PHEs to satisfy the most predicted points within ±50%, which was regarded as highly acceptable accuracy in the application field. The correlation proposed by Ayub et al. [34] made an excellent attempt to simplify the complex factors about flow boiling in PHEs. Unfortunately, their valid ranges may be rather limited (about one-third of points outside the valid ranges) and the correlation tends to overestimate the two-phase Nusselt numbers.
The dimension analysis for flow boiling heat transfer in plate heat exchangers in previous work was quite comprehensive and worthy of reference. For the simulations of some new data points in the database, the coefficients and exponents have changed and the new criterion is introduced here to modify the correlation:
$Nu=1441β*1.30Wem0.284Bo0.283ρ*−0.239,Bd⋅Rel0.5≤200$
(9)
$Nu=4.06β*1.34Rev0.368Relo0.258Bd0.317Bo0.415ρ*0.354,Bd⋅Rel0.5>200$
(10)
Where the dimensionless numbers have the same definitions as follows. Also, the maximum value of chevron angle is 70 deg and the correlation is valid for 11 < Bd·Rel0.5 < 2100, 0.11 MPa < Psat < 2.12 MPa.
$chevronangleratio:β*=β/βmax$
(11)
$densityratio:ρ*=ρl/ρv$
(12)
$Bondnumber:Bd=(ρl−ρv)gdh2σ$
(13)
$homogeneousWebernumber:Wem=G2dhρmσ$
(14)
$Boilingnumber:Bo=qGilv$
(15)
$vapor Reynolds number:Rev=Gxdhμv$
(16)
$liquid only Reynolds number:Relo=Gdhμlv$
(17)
$homogeneous vapor qualityρm=(xρv+1−xρl)−1$
(18)
The number Bo·Rel0.5 presents the interrelation of surface tension, body force, viscous force, and inertia force in saturated-flow boiling in microchannels [36]. When Bo·Rel0.5≤200, surface tension and viscous force are accounted for heat transfer characteristics, while Bo·Rel0.5>200, the inertia force and body force dominate the heat and mass transfer. Compared with only using the Bond number to distinguish the channel type, using the non-dimensional parameter Bo·Rel0.5 has more accuracy.
Figure 5 shows the comparison of the two-phase Nusselt numbers predicted by the modified correlation and all experimental results used in the development of the new correlation. The modified correlation predicts 74.3% of the database within the ±30% error band, and 94.9% of the database within the ±50% error band. In addition, the mean relative error e = +3.4% and the mean absolute error |e| = 21.3%. In the modified correlation, the exponent of density ratio is a positive number when Bd·Rel0.5 > 200 (macroscale), but this does not mean the heat transfer coefficient will directly increase with the density ratio of refrigerants due to changes in other properties. Figures 6(a) and 6(b) show comparisons between the new correlation and two existing correlations on micro- or macroscale, respectively. Compared to the existing correlations, the new one makes appropriate modifications about the underestimation or overestimation. It can be observed that the new correlation predicts better particularly for Bd·Rel0.51≤ 200, while for Bd·Rel0.5> 200, the current correlation presents slightly better accuracy and the validation in further investigations may still be required.
Fig. 5
Fig. 5
Close modal
Fig. 6
Fig. 6
Close modal
Last but not least, the difference in prediction accuracy between the current correlation and others may result from the different data types: some referring to the local values while others to the mean values. Early investigations about heat transfer inside plate heat exchangers were mostly with respect to mean rather than local values. The current modified correlation makes an attempt to unify the prediction of heat transfer coefficient for both mean (57.6%) and local (42.4%) data points. Similarly, future efforts need to be put into testifying this correlation or yet develop newer better models.
## 5 Conclusions
A review of investigations about flow boiling heat transfer in plate heat exchangers is presented. The heat transfer coefficient is influenced by both experimental conditions and plate geometries, which leads to the difficulty in the establishment of widely accepted predicting correlation. On one hand, previous experimental investigations used to be based on their own data sets. Some existing correlations behaved good accuracy; however, their experimental conditions and valid ranges were quite limited. On the other hand, there are still numerous controversial issues about the physical mechanism of flow boiling inside plate heat exchangers, and it is quite challenging to unify the fundamental theories. This work made an attempt to develop a modified correlation based on the data points available in open literatures.
1. A database containing 533 data points collected from literatures has been established for the development of new correlations. It’s observed that several existing correlations presented moderate accuracy for the current data points.
2. Based on the dataset some modifications of one existing correlation were made here and the modified correlation predicts better: 74.3% of data points within ±30% error band and 94.9% within ±50% error band. It is valid for 11 < Bd·Rel0.5 < 2100, 0.11 MPa < Psat < 2.12 MPa, and 30 deg ≤ β ≤ 70 deg, respectively. Both mean and local experimental results were considered in the development of the modified correlation.
3. In this work, a new criterion about the transition from micro- to macroscale has been introduced for the flow boiling heat transfer in plate heat exchangers with a combined dimensionless number Bd·Rel0.5. The new correlation predicted better particularly for Bd·Rel0.5 ≤ 200, while for Bd·Rel0.5> 200, this correlation presented slightly better accuracy. Future efforts for the validation of this correlation or the development of newer better models may still be required.
## Acknowledgment
This work is supported by the National Science Foundation of Zhejiang Province in China (LY19E060004) and Science and Technology on Thermal Energy and Power Laboratory Open Foundation of China (No. TPL2017BA003).
## Nomenclature
a=
amplitude of surface corrugation, m
b=
corrugation pressing depth, m
d=
diameter, m
e=
error
h=
heat transfer coefficient, W/(m2 K)
i=
latent heat, kJ/kg
n=
number of data points
q=
heat flux, W/m2
t=
temperature, K
x=
vapor quality
L=
length, m
W=
width, m
A=
abbreviation for corrugation amplitude
B=
abbreviation for the chevron angle
G=
mass flux, kg/(m2 s)
L=
abbreviation for corrugation pitch
Bd=
Bond number
Bo=
Boiling number
Nu=
Nusselt number
Re=
Reynolds number
We=
Weber number
### Greek Symbols
β=
chevron angle, deg
β*=
chevron angle ratio
γ=
corrugation aspect ratio
Λ=
dimensionless corrugation parameter
λ=
corrugation pitch, m
μ=
viscosity, Pa s
ρ=
density, kg/m3
ρ*=
density ratio
σ=
surface tension, N/m
φ=
surface enlargement factor
### Subscripts
ch=
channel
eq=
equivalent
h=
hydraulic
l=
liquid
lo=
liquid only
lv=
liquid-vapor
m=
mean or homogeneous
p=
port
Ref=
refrigerant
sat=
saturation
v=
vapor
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## Sunday, January 3, 2021
### LaTex, a curse and a blessing
I've been making teaching materials on computers for over 25 years. Maybe 15 years ago, I was introduced to MathType, and it made my equations so much nicer. Now it doesn't work with Word, and you have to pay a yearly fee. No thanks. It seems crazy to me that MS Word doesn't have a better equation editor. (I don't really remember what I don't like about it, but I think it has annoyed me lots over the years.)
I got a new computer in the Spring, and since then, whenever I need to make a formula, I've been using my old computer with an old version of Word, and my very old copy of MathType. Today I wondered if it was time to bite the bullet, and make a quiz using LaTex.
I've tried to learn a bit of Latex a number of times before, and it just felt overwhelmingly weird. I especially hated that I couldn't see what I was doing. This time was better in a number of ways. First, my colleague showed me overleaf, where I can see what I'm doing. You can choose split screen, and hit recompile after every little change.
The next thing that helped was that I got a bunch of materials from the author of the book I'll be using. (Oscar Levin, Discrete Mathematics: An Open Introduction.) I used those as templates for my own work. I deleted what I didn't want, and began to add what I did want. (If you want to learn LaTEx (or TEx), and you don't have a bunch of materials someone else made that you can modify, this quiz template might be helpful.)
The reason I was using LaTex was the equations, but that was one of the things I didn't know how to do. This site, codecogs, came to the rescue!
I also needed to include an image of a Venn diagram. I read up (googled latex image), tried to do what they said, and my image ended up in a weird place, next to the questions. I guessed, and added a line that I saw in other places in my documents from Levin (\vskip 1em). I figure that's a vertical skip. I have no idea what the 1em is. (I tried 5em for more space. Nope.) It worked!
But the image was still too big. Read up again, use [scale=0.5], put it in the wrong place, so it doesn't work. Figure out the right position, it works! And now the image doesn't look right hanging out on the left. I read up, use "the centered environment," and it is all just prefect!
Here's the centering:
\begin{center}
\includegraphics[scale=0.5]{venn10}
\end{center}
That took me over an hour. (Maybe two.) I made a second version of that quiz in ten minutes.
I'm learning...
Summary
Does LaTex seem way too complicated, but it still might be the answer to your problems?
• Use a simple environment like overleaf where the split screen lets you see what you've done.
• Use something simple like codecogs to build your equations.
Good luck!
## Thursday, December 31, 2020
### Square & Triangular Numbers
It's my vacation. And here I am, playing with math. Woo hoo.
If you've played with this problem before, perhaps this is boring and old hat. But I've seen the question many times, and never before have I followed up on it.
I just got a book I ordered. A Friendly Introduction to Number Theory, by Joseph Silverman. THe very first problem he asks the reader to attempt is:
Exercise 1.1. The first two numbers which are both squares and triangles are 1 and 36. Find the next one, and if possible, the one after that. Can you figure out a way to efficiently find triangle-square numbers? Do you think there are infinitely many?
I found the next one easily, by making lists on paper of the square and triangular numbers. It was about 6 times as big as 35 (which is about 6 times as big as 1). So I figured it would take too long to find another by hand. I wrote a Sage script. (It took me a few tries. I had lots more print statements until I was sure it was working.) I now have 7 of them. But more importantly, I've found a pattern. If you want to play with this, I would recommend not reading further.
.
.
.
.
.
The business about each one being about 6 times as big as the one before looked promising. So I checked. Let's call them m (for matching numbers), where the actual number is m2.
m0 = 1,
m1 = 6*m0=6,
m2 = 6*m1 - 1 = 35,
m3 = 6*m2 - 6 = 204,
m4 = 6*m3 - 35 = 1189.
At this point, it becomes clear that m(i) = 6*m(i-1) - m(i-2). And that's where I am now. I don't really know that this will continue to work forever. But it does continue for all the numbers I've found using Sage. And I just found one more to see if it continues further. It does.
Next step, proof. I will see if that's something I can do.
I just found a closed form for the formula. It's ugly but it works. (I learned how to do that step from Oscar Levin's Discrete Mathematics: An Open Introduction, in 2.4, Solving Recurrence Relations. That's the book I'll be using to teach discrete math from this coming semester.)
Now the next step is proof....
## Tuesday, December 15, 2020
### Getting Better at Canvas
I am not a Canvas expert, but I've learned a lot this past semester, and hope to keep learning more.
This post is a compilation of some of the things I've learned that make Canvas better for me and my students.
Images
I took a course offered by my employer (Contra Costa Community College District) called Becoming an Effective Online Instructor (BEOI). In the course they recommended using lots of pictures in our Canvas pages. I haven't gotten to the point of "lots" yet, but I'm trying to become more aware of what images will help students learn mathematical concepts, and also what mathematical images bring beauty to the screen.
I love this image, titled Banded Torus, by Thomas Banchoff and Davide Cervone. I recently realized that part of its power for me was its black background. So I changed the cover images for my calculus and precalculus courses, to incorporate a black background. Both of these are done on desmos in reverse contract. The originals, with white background, were nowhere near as lovely.
For calculus, I wanted to show both slope and area.
For precalculus, I wanted to show all of the functions we study (along with the circle). I did leave out the rational functions, not wanting the image to look too busy.
Orientation
That BEOI course offered very specific ideas about how to set up an orientation module. (I had to do one their way for the course, and then I modified it to make it my own for my students.) One of the items in it is a quiz. I loved putting that together. I tell students where the answer to each question is (as part of the question), so they can look it up. Partly, it's a way to emphasize certain things from all of the pages I am hoping they will have read. (Yes, you can call me at home! But not after 8pm.), and it's also a chance to be silly (how many chickens does Sue have?). It also allows students to start out the semester with a perfect quiz score (hopefully!).
Zoom Recordings
I guess Zoom saves these already, but I wanted them listed in my modules. So I had a module with links to each day's recording. In a mid-semester survey, two students requested that the various topics covered be listed with timestamps. I don't have time to do that, but I figured out a way to allow students to do it for each other. I have one page in each unit where I link to each recording by date, and list the topics we covered underneath. I set that page so that students can edit it. (They didn't this semester, but if we start out this way, and they get a bit of extra credit for it, we might be able to jointly build a great resource.)
Quiz & Test Retakes
Until this semester, I did not use the Canvas grades function. I do my grading using Excel, and it has lots more flexibility for my crazy formulas that calculate the grade four different ways and take whichever is best for the student. But everything was online this time. So that's where the grades were. I turned off the totals, so students wouldn't see the wrong scores that Canvas figured.
I allow students to take quizzes multiple times. (New version each time, of course.) And they get two chances on most tests. I started out building a new Canvas assignment for each retake. What a mess to figure grades! I finally realized that Canvas would accept multiple attempts on an assignment, and allow me to look at each one. That feature works great.
There is a "hide grades" feature that is supposed to hide the grades until I'm ready to post them. But it apparently doesn't hide my comments, which defeats the purpose. (Since I explain my grading in the comments.) Maybe there's a better way to do that, and I'll learn it soon. [Edit: After I wrote this post, I found out that there is indeed a better way. In the gradebook, go to the assignment, at the name of it, click on the three dots, choose 'Grade Posting Policy', and choose manually. Then remember to 'Post Grades' when you're done.]
Organizing Content
The Canvas "modules" serve as containers for each of my units. So each one starts with a "unit sheet", giving an introduction to the ideas they'll be learning about, objectives, and a schedule. That schedule is what I want my students to think of as their home base in my class. I add details to it daily, I highlight the current class session, and I link to pages and assignments in it. I add more detail to it when I'm prepping my next class. It works great for me, and I want it to work great for my students. I put a link to it on the Home page, so it's easy to get to.
Community Page-Building
Canvas pages start out as editable only by the teacher. But you can change that to allow students to edit a page. Our fist topic in our second unit (in trigonometry) was radians, and I wanted them to do something after our first test, before that next class session. So I created this page, and I told them to find the best videos online that explain radians. I think comparing video explanations was a great way for them to be thinking about whether they really understood the concept.
Next Semester
I am still thinking about how to get students to participate more, and will be looking for ideas to help with that. I know I should make a few videos where I explain some of the key concepts. But I seem to be resisting doing that.
What have you learned recently about how to use Canvas well?
## Thursday, November 12, 2020
### Note-Taking & Learning Something New at 64
I've been teaching for over 30 years, almost all of it at the community college level. So I've gotten pretty used to what I do. (But not bored. I still discover new ideas every semester, and I still love connecting with students.)
That changed with quarantine. Before 2020, I was pretty sure that I never wanted to teach online. It looked like way more work, and it was clear to me that I wouldn't be able to have the same level of connection with my students in an online class. I was right about both things, but (amazingly, to me) I am enjoying teaching online.
I meet my students in Zoom two days a week. Most of them won't turn their cameras on, and I want to respect that. (I offered extra credit for cameras on, and I get to see 2 to 5 faces each day. It's better than none.)
I have a light load this semester. Just two classes. And it still feels like full-time work. Next semester I'll have over twice as many units (in 3 classes). I'm starting to prepare ahead of time, so I don't drown.
I started taking notes for the Discrete Math book I'll be using, and after I wrote up some notes, I went back and wrote an introduction to note-taking. Tonight I described it to my bother (who's becoming a teacher), and realized that it was a bit of an epiphany for me.
I have terrible handwriting, and always thought I didn't know how to take good notes. I copy the board in a math class, just like everyone else. That's not really note-taking to my way of thinking. I highlight the good bits when I'm reading, and when I come to an example, I try to do it myself before looking at the author's steps. But notes? Nah, that just never seemed like one of my skills.
Well, I was a little excited as I finished up my notes for the first section of the textbook. I had set the Canvas page so that students could edit it too, and so I had purposely left some parts of my notes incomplete. As I looked at what I had written and did a bit of rearranging, I saw some patterns.
So I wrote this introduction:
How do you take notes when you read? My reading notes may surprise you. I see 4 types of things that I'm doing in my notes:
• The first, organizing by making lists, will be familiar to you.
• But I am also trying to connect a new term to other meanings outside of math.
• And I am reacting to what I read (surprise, and noticing how powerful something feels).
• I also made up my own example.
That seemed kind of cool.
Then, when I talked to my brother, I realized that I had always thought I was no good at taking notes. (I didn't think I really needed to be any better at it, because I am good at most academics anyway. But...) I never thought I could teach students how to take better notes. And I realized that this one task I gave myself, to make some reading notes for the textbook, suddenly showed me that I know a lot about reading math and taking notes that I can share with students.
So that's my epiphany. I do know how to take good notes, and now I know how to describe that process to students.
What helps you conquer a text you're reading? Do you take "good notes"? What does that mean to you?
## Sunday, September 20, 2020
### Division by 0
[Once again, I have written something for my class that I think will be valuable for others.]
Big question: What are the values of , , and ?
We want to be able to look at each of these fractions, know what it equals, and understand why. This becomes vital in calculus. [Note: Many students have trouble with this. It may be because elementary teachers are often uncomfortable with division, and teach it by memorization, instead of as something deep to understand. Or it may be that this is deep, and our brains need more time to really make sense of it.]
To help ourselves understand this, we tie it to something simpler that we understand better. Division is the inverse of multiplication (ie they undo each other). So it will help to explore how the two operations are connected.
[Note: One notational problem with division is that it's written in different ways that place the numbers in opposite orders. , but these are also equal to. When I was young, I had trouble keeping track of which was which, so I would write down an easy problem, like this one, to help me remember.]
Now we consider the multiplication problem that goes with this division problem: , and we can say that 6 divided by 3 is 2 because .
Let's use T for top, B for bottom, and A for answer, and rewrite this equivalence of a division problem and its associated multiplication problem, in a way that will always be true:
In the fraction (or division), we have top over bottom gives answer, and that gives us a multiplication problem where the original bottom times the answer from the division gives us the original top. [Note: I am purposely avoiding the proper terms: numerator or dividend, denominator or divisor, and quotient (for the answer). For anyone who gets those terms mixed up, it's easier just to focus on position for the moment.]
Now we are ready to consider each of the three original questions, using this correspondence.
1. Let's think about the multiplication associated with :
So what do we multiply 0 by to get 3? Hmm. It seems that nothing works. There is no number that can multiply with 0 and give us 3. So the division problem (or fraction) has no solution, and we say that is undefined. This is why we say "division by 0 is undefined".
2. . Ahh, this one is easier. so the answer is 0.
3. . Hmm, this time A could be any number, and the multiplication would be correct. This is still division by 0, so it is still undefined, but it is very different from the first case. We call it indeterminate. We can see why by looking at a rational function example.
Example:
When x= -2 or 2, this function will be undefined (because we have division by 0). But the function's behavior for x values very close to -2 is very different from its behavior for x values very close to 2.
is a vertical asymptote for the graph. This means that as x approaches -2, the y values approach . (This can be written "as ".) You can verify this by trying these x values: -2.1, -1.9, -2.01, -1.99,... (You can also use desmos to view the function.)
What happens near ? We see that the y value does not depend on the factor , because it cancels. So, as long as , . At , this would equal 1/4. The function is not defined here, but now we can see that as .
So why was called indeterminate? Because the value associated with it in a particular function is determined by other parts of the function. Although is undefined, we saw that, in this particular function the value of the function got close to 1/4 as the x value got close to 2, which is the number that would give us . This concept goes with the concept of limits, one of the 3 major topics in calculus.
## Wednesday, September 16, 2020
### What sorts of things are impossible?
Here's an interesting article in QUanta, by David Richeson. I'll be thinking about what else I might add to this post...
## Friday, September 11, 2020
### Solving Application Problems (in Trigonometry)
I started this blog in 2009, was active for about 6 years, and then not so much for the past 5 years. I wrote two posts in the spring, both related to online teaching. We were all trying to learn how to teach well as we scrambled to do it while learning. I was happy to keep seeing my students online, and Zoom was our class. I used Canvas a little but not much.
Over the summer I learned a lot about effective online teaching. (I'm still not sure it can ever be nearly as effective as in-person, but...) I developed my Canvas shells for each course, and I started the semester readier than I had expected to be. My Canvas shells are not done. I created a "module" that orients students to online learning and my course. And I created a module for our first unit. The rest is still in progress.
Today I added a page for my trig students, on solving application problems. I want to share it here. (And I may share lots of my Canvas "pages" here, sometimes with modifications.)
Years ago, I modified George Polya's wonderful outline of problem solving steps. We start with that. It's a good idea to print it out, and turn to it whenever you're stuck.
Draw a Diagram.
Always start by drawing a diagram. This step is vital, and is a major part of "Understanding the Problem".
Your diagram does not need to be artistically good. It does need to show relationships well. An artist might show my shadow going off at an angle. But for a math diagram, it is better to show the right angle involved, as a right angle.
In the diagrams on the right, the top drawing is prettier, and the shadow is more evocative, but the bottom drawing shows the right angle between a vertical object and its horizontal shadow, which is what will help you do your mathematical analysis.
Example (#22 in 2.4, page 93): If the angle of elevation of the sun is 63.4° when a building casts a shadow of 37.5 feet, what is the height of the building?
Draw your diagram now, labeling it with everything given and a variable for the value requested. (My drawing is below.)
.
.
.
.
.
.
I labeled the height of the building h.
Write a Trig Equation.
In a simple problem, with only a few pieces of information this is all you need for the "Devising a Plan" step. We are given the value of the side adjacent (next to) the given angle, and we want to find the value of the side opposite the angle. (The hypotenuse is neither given nor asked for.) Which trig function uses adjacent and opposite? (Two of them do, but the one we use most of the time is...)
.
.
.
.
... , and this gives us
Do a bit of algebra.
This is the "Carry out the Plan" step. To solve for h, we multiply both sides of the equation by 37.5:
I pulled out my calculator for that last step (making sure it was in degree mode). Since our given length was given to tenths of a foot, I round, and give my final answer as 74.9 feet.
This is the "looking back" step on the handout. If we look at our diagram, does a height of about 75 feet seem reasonable? Well, the height seems bigger than the shadow, and maybe about twice as big, so yes, it seems reasonable.
Practice.
If you get stuck on application problems, a good way to practice is to re-do problems that you've watched someone else do (perhaps on youtube). Try not to look at your notes. If you need to, go ahead and look. Do as much of the problem on your own as you can. If you looked at your notes at all, do it again the next day.
## Thursday, June 25, 2020
### Playful Math Education Carnival #139 (formerly known as Math Teachers at Play or MT@P)
"It’s like a free online monthly magazine of mathematical adventures." (Denise Gaskins)
Black Lives Matter. How does that idea and movement intersect with math and play? It's hard to imagine play intersecting with the painful history of racism in the U.S. We can collect data to show how pervasive anti-Blackness has been and is. We can discuss how math courses have been used to filter out students from desirable professions (doctors, engineers, lawyers). We can discuss how Black people are more involved in the history of math than you'd guess from the Eurocentric naming. (Check out who knew Pascal's triangle before Pascal!) None of that is playful. But celebration can be playful. Let's celebrate Juneteenth!
## 139
Every number is cool.* Here are some ways 139 is cool:
• 139 is the sum of 5 consecutive prime numbers (19 + 23 + 29 + 31 + 37).
• 139 is the smallest prime before a prime gap of length 10.
• 137 and 139 form the 11th pair of twin primes.
• 139 is the 34th prime number.
Puzzle: The digit sum is the result after adding the digits repeatedly until you get down to one digit. 139’s digit sum is 4. If you write 139 in base two, you get 100 1011, which still has a digit sum of 4. Does this always happen? If not, does it happen in any other bases?
New Homeschoolers
I have a hunch the quarantine has moved lots of families from school to homeschooling. If you’re new to homeschooling, get ready to have fun playing with math. Most mathematicians are in it at least partially for the fun of it. We like to play with numbers, shapes, and logic. The more you play with math with your kids, the more likely they are to enjoy it.
There are vast resources online to help you. Until 3rd grade, just play games, cook, measure, read mathy stories, and have fun with it all. If your kid wants a curriculum before that because they love math, then check out Beast Academy. It has levels 2 to 5 (topics correspond to grades 2 to 5, difficulty levels are a grade or two higher). Some families never use a curriculum; if you’re interested, you may want to explore unschooling. Math lovers eventually want to take classes, which you can do either through your local community college (I’ll be teaching trigonometry, pre-calculus, and calculus I online this fall) or Art of Problem Solving. There are lots of other great resources; these are just my personal favorites.
You might find ideas that work for you in my book, Playing with Math: Stories from Math Circles, Homeschoolers, and Passionate Teachers. Or from other books from my publisher, Natural Math. I also highly recommend Denise Gaskins’ blog (especially this post on homeschooling math), website, and booksDan and Christopher have some good ideas about playing mathematically with kids too.
Talking Math With Your Kids (#TMWYK)
Math & Language Play
One of my favorite math educators, Marilyn Burns, invented a game where students look for $1 words. A=1¢, B=2¢, etc. You could combine math and any other subject by making$1 phrases. Sometimes kids like the simplest games. This might be a craze at your house. (My son used to love Shut the Box, a simple dice game that did nothing for me. It sure was good number practice for him.)
π-ku, a competition, in which all their favorites will be posted at the Aperiodical blog. I'll try:
Three One Four.
Hmm.
Not very hard.
Games
So much of math is based on logic, any logic games you play will deepen your students' affinity for math. Here are a few others:
• Set Tic Tac Toe, described by Tanya Khovanova, invented by her students. You may want to play the basic game of Set for a few months before attempting this. But if I could figure out a way to do this at a distance, I'd love to try this out.
• Planarity game. (This is connected to a field of math called graph theory.)
• Play with wallpaper symmetries.
Math History
Podcasts aren't my thing. Yet. But if this series is as good as it sounds, I'll just have to figure this newfangled genre out. Opinionated History of Mathematics. With an interview and glowing review at Aperiodical.
Online Events
This summer Art of Inquiry is hosting free science webinars on space, astrobiology, and AI for school children and their families. The webinars are led by university professors and industry experts. You can register for the events on Eventbrite. Here is their June-July 2020 schedule:
• Living Through a Revolution: Multi-messenger Astrophysics - Dr. Roopesh Ojha, GSFC NASA, June 26th
• Figuring out the Earth from inside out - Dr. Kanani Lee, Lawrence Livermore National Laboratory, June 30th
• Mars Rovers - Dr. Allan Treiman, Lunar and Planetary Institute, July 3rd
• The search for life on Mars in XXI century - Dr. Alex Pavlov, GSFC NASA, July 10th
• Where in the Universe did we come from? - Dr. Ethan Siegel, science author, "Starts with a Bang" Forbes contributor, July 23rd
• Why we should build a Moon base - Dr. Ian Crawford, University of London, July 31st
If you know of other math-related online events, please mention them in the comments.
This series of blog carnivals was founded and is kept going by the fabulous Denise Gaskins. You can find out more at her blog. Last month's carnival was hosted by John Golden, the Math Hombre. Check it out!
-----
*Well, sometimes their coolness is in their bad reputation (sounds like a few people I knew in high school) ...
## Thursday, June 18, 2020
The Math Teachers at Play Blog Carnival (aka Playful Math Education Carnival) will be a bit late this month.
I am looking for good posts now. If you can send me any links by Saturday, that would be great. I am hoping to put it together on Sunday.
Want to know what a blog carnival is? Check out last month's, by my pal John Golden.
## Sunday, April 19, 2020
### Corona Post #2: Teaching Online
[#2 because my previous post in March on my online math circle was due to people needing to take their math circles online when the shelter-in-place orders were just starting.]
I've been teaching online for 4 weeks now, two before our spring break and two after. At first I was just trying to learn how to manage teaching on zoom. I bought a whiteboard that's still sitting on two chairs in my living room, and I sit in a tiny chair while I write on it. Not ideal, but I get to see my students, and I feel like I'm still working with them where they are, not just lecturing.
(Some day I'll finally install it on my living room wall. I procrastinate with tasks like that. I'm not sure why it feels intimidating...)
A few weeks ago I made a google slides presentation for my Discrete Math course to explain a way of counting possibilities called Stars & Bars. I had fun doing it. You're welcome to modify it and use it in your teaching.
Just now I made another. This one is for Calculus II, on Taylor & Maclaurin Series (really just a Maclaurin series). I was motivated by knowing that there would be too much writing for my little whiteboard. This presentation has a handout to go with it.
I'm also teaching Calculus I. I haven't made any cool new materials for that course yet. But I will...
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http://mathhelpforum.com/calculus/35364-taylor-polynomial-print.html
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# Taylor Polynomial
• Apr 21st 2008, 09:49 AM
akhayoon
Taylor Polynomial
Question was
evaluate the 4th taylor polynomial of $\sqrt{3+x^{2}}$ around a=-1
$f4(x)=2-\frac{-(x+1)}{2}-\frac{(x+2)^{2}}{(8)2!}-\frac{3(x+1)^{3}}{(32)3!}-\frac{15(x+1)^{4}}{(128)4!}$
the marker notes however that there was something missing in the 3rd term
that the 3 in the fourth term was wrong, and that the 15 and 128 in the last term is wrong as well...
but after looking at my derivatives I can't figure out why this is???
• Apr 21st 2008, 10:41 AM
Opalg
Quote:
Originally Posted by akhayoon
Question was
evaluate the 4th taylor polynomial of $\sqrt{3+x^{2}}$ around a=-1
$f4(x)=2-\frac{-(x+1)}{2}-\frac{(x+2)^{2}}{(8)2!}-\frac{3(x+1)^{3}}{(32)3!}-\frac{15(x+1)^{4}}{(128)4!}$
the marker notes however that there was something missing in the 3rd term
that the 3 in the fourth term was wrong, and that the 15 and 128 in the last term is wrong as well...
but after looking at my derivatives I can't figure out why this is???
$f'(x) = x(3+x^2)^{-1/2},\ \ f'(-1) = {\textstyle-\frac12}$.
$f''(x) = (3+x^2)^{-1/2} - x^2(3+x^2)^{-3/2},\ \ f''(-1) = {\textstyle\frac12 - \frac18 =\frac38}$.
$f'''(x) = -3x(3+x^2)^{-1/2} + 3x^3(3+x^2)^{-5/2},\ \ f'''(-1) = {\textstyle\frac38 - \frac3{32} =\frac9{32}}$.
That gives $f_3(x) = 2 - \frac{(x+1)}{2} + \frac{3(x+1)^{2}}{(8)2!} + \frac{9(x+1)^{3}}{(32)3!}$. I'll leave you to sort out the (x+1)^4 term.
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https://ggfx.data-imaginist.com/reference/raster_placement.html
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When using raster objects directly you need to somehow define how it should be located in resized in the plot. These function can be used to inform the filter on how it should be used. They only work on raster type object, so cannot be used around functions or layer id's.
ras_fill(raster, align_to = "canvas")
ras_fit(raster, align_to = "canvas")
ras_stretch(raster, align_to = "canvas")
ras_place(raster, align_to = "canvas", anchor = "topleft", offset = c(0, 0))
ras_tile(
raster,
align_to = "canvas",
anchor = "topleft",
offset = c(0, 0),
flip = FALSE
)
## Arguments
raster A raster or nativeRaster object or an object coercible to a raster object Should the raster be positioned according to the canvas or the current viewport Where should the raster be placed relative to the alignment area A unit or numeric vector giving an additional offset relative to the anchor. Positive values moves right/down and negative values move left/up Should every other repetition be flipped
## Value
The input with additional information attached
## Examples
library(ggplot2)
system.file('help', 'figures', 'logo.png', package = 'ggfx')
))
# Default is to fill the viewport area, preserving the aspect ratio of the
# raster
ggplot(mtcars) +
with_blend(
geom_point(aes(mpg, disp)),
logo
)
# But you can change that with these functions:
ggplot(mtcars) +
with_blend(
geom_point(aes(mpg, disp)),
ras_place(logo, 'vp', 'bottomright')
)
# Here we tile it with flipping, centering on the middle of the canvas
ggplot(mtcars) +
with_blend(
geom_point(aes(mpg, disp)),
ras_tile(logo, anchor = 'center', flip = TRUE)
)
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http://projecteuclid.org/euclid.aop/1176993221
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## The Annals of Probability
### Synonymity, Generalized Martingales, and Subfiltration
Douglas N. Hoover
#### Abstract
Aldous recently introduced the notion of synonymity of stochastic processes, a notion of equivalence for processes on a stochastic basis which generalizes the notion of "having the same distribution". We show that generalized martingale properties, such as the semimartingale property, are preserved under synonymity, and that synonymous semimartingales have decompositions with the same distribution law. A variation of our method yields a relatively elementary proof of the theorem of Stricker that semimartingale remains a semimartingale with respect to any subfiltration to which it is adapted.
#### Article information
Source
Ann. Probab. Volume 12, Number 3 (1984), 703-713.
Dates
First available in Project Euclid: 19 April 2007
http://projecteuclid.org/euclid.aop/1176993221
JSTOR
Digital Object Identifier
doi:10.1214/aop/1176993221
Mathematical Reviews number (MathSciNet)
MR744227
Subjects
Primary: 60G07: General theory of processes
Secondary: 60G48: Generalizations of martingales
#### Citation
Hoover, Douglas N. Synonymity, Generalized Martingales, and Subfiltration. Ann. Probab. 12 (1984), no. 3, 703--713. doi:10.1214/aop/1176993221. http://projecteuclid.org/euclid.aop/1176993221.
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https://korali.readthedocs.io/en/master/modules/problem/reinforcementLearning/reinforcementLearning.html
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# Reinforcement Learning
Describes a sequential decision making problem. We are given an environment that transitions to a state $$s'$$ and returns a reward $$r$$ for a given action $$a$$ and state $$s$$ with probability $$p(s',r|s,a)$$. We want to find the policy $$\pi$$ that choses an action $$a$$ for a given state $$s$$ with probability $$\pi(a|s)$$ such that for every state $$s$$ the chosen action $$a$$ is such that the value function
$\begin{split}V^\pi(s)=\E_{\substack{a_t\sim \pi(\cdot|s_t) \\ s_{t+1},r_t\sim p(\cdot,\cdot|s_t,a_t)}}\left[\sum\limits_{t=0}^\infty \gamma^t r_t\bigg|s_0=s\right]\end{split}$
is maximal. Here $$\gamma$$ is the discount factor.
We distinguish discrete and continuous action domains. Sub-Categories:
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https://www.muchlearning.org/?page=65&node_id=try-intro
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# Try Muchlearning
#### Try MuchLearning's TestMe™ feature
based on MuchLearning's Step-By-Step Calculus
Ideal for all students before taking their first calculus course.
Ideal for students willing to gain an edge in their first calculus course.
Ideal for students willing to gain an edge in their second calculus course.
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http://www.ms.u-tokyo.ac.jp/seminar/2018/sem18-170.html
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## 数理人口学・数理生物学セミナー
### 2018年07月18日(水)
15:00-16:00 数理科学研究科棟(駒場) 118号室
Malay Banerjee 氏 (Department of Mathematics & Statistics, IIT Kanpur)
Effect of demographic stochasticity on large amplitude oscillation
[ 講演概要 ]
Classical Rosenzweig-MacArthur model exhibits two types of stable coexistence, steady-state and oscillatory coexistence. The oscillatory coexistence is the result of super-critical Hopf-bifurcation and the Hopf-bifurcating limit cycle remains stable for parameter values beyond the bifurcation threshold. The size of the limit cycle grows with the increase in carrying capacity of prey and finally both the populations show high amplitude oscillations. Time evolution of prey and predator population densities exhibit large amplitude peaks separated by low density lengthy valleys. Persistence of both the populations at low population density over a longer time period is more prominent in case of fast growth of prey and comparatively slow growth of predator species due to slow-fast dynamics. In this situation, small amount of demographic stochasticity can cause the extinction of one or both the species. Main aim of this talk is to explain the effect of demographic stochasticity on the high amplitude oscillations produced by two and higher dimensional interacting population models.
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https://rd.springer.com/chapter/10.1007/978-88-470-0530-3_25
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IFAE 2006 pp 171-174
# Single Top at Hadron Colliders
• Simona Rolli
Conference paper
## Abstract
At hadron colliders, the strong production of $$t\bar t$$ pairs yelds large top quark samples, allowing detailed studies of many properties of top quark production and decay. However, the precise determination of the properties of the Wtb vertex, and the associated coupling strenghts, will more likely be obtained from measurements of the electroweak production of single top quarks. Single top quarks can be produced via three different reactions. These reactions are shown in Fig. 1 from left to right. The first two graphs, usually referred to as the 2 → 2 and 2 → 3 processes, respectively, both refer to the same physical W-gluon fusion process. The second production mechanism (the third graph from the left), referred to as the Wt process, is the direct production of a top quark and a W boson. This process is immeasurably small at the Tevatron, but is predicted to have a sizeable cross-section (≈ 60–110 pb) at the LHC. The third reaction proceeds via production of an off-shell W and will be called the W* process.
## Keywords
Hadron Collider Production Cross Section Cross Section Limit Gluon Fusion Process Electroweak Production
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
## Preview
Unable to display preview. Download preview PDF.
## References
1. 1.
S. Rolli, http://ncdf70.fnal.gov:8001/ifae2006/IFAE_SingleTop6.pdfGoogle Scholar
2. 2.
B.W. Harris, E. Laenen, L. Phaf, Z. Sullivan, S. Wienzierl, Phys. Rev.D 66, 054024(2002).
3. 3.
M. Feindt, e-print archive physics/0402093 (2004).Google Scholar
4. 4.
CDF Collaboration, CDF note 8185-conf, ttp://www-cdf.fnal.gov/physics/new/top/confNotes/cdf8185_stconfnote_700pb.pdfGoogle Scholar
5. 5.
D0 Collaboration, D0 note 4871-conf, http://www-d0.fnal.gov/Run2Physics/WWW/results/prelim/TOP/T20/T20.pdfGoogle Scholar
6. 6.
ATLAS Detector and Physics Performance Technical Design Report CERN/LHCC/99-14, ATLAS TDR 14, 25 May 1999.Google Scholar
7. 7.
S. Rolli, M. Cobal, M.P. Giordani, ATL-COM-PHYS-2006-036.Google Scholar
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https://en.wikipedia.org/wiki/Closed_formula
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# Closed-form expression
(Redirected from Closed formula)
"Closed formula" redirects here. For "closed formula" in the sense of a logic formula with no free variables, see Sentence (mathematical logic).
In mathematics, a closed-form expression is a mathematical expression that can be evaluated in a finite number of operations. It may contain constants, variables, certain "well-known" operations (e.g., + − × ÷), and functions (e.g., nth root, exponent, logarithm, trigonometric functions, and inverse hyperbolic functions), but usually no limit. The set of operations and functions admitted in a closed-form expression may vary with author and context.
Problems are said to be tractable if they can be solved in terms of a closed-form expression.
## Example: roots of polynomials
The solutions of any quadratic equation with complex coefficients can be expressed in closed form in terms of addition, subtraction, multiplication, division, and square root extraction, each of which is an elementary function. For example, the quadratic equation:
${\displaystyle ax^{2}+bx+c=0,\,}$
is tractable since its solutions can be expressed as closed-form expression, i.e. in terms of elementary functions:
${\displaystyle x={-b\pm {\sqrt {b^{2}-4ac}} \over 2a}}$
Similarly solutions of cubic and quartic (third and fourth degree) equations can be expressed using arithmetic, square roots, and cube roots, or alternatively using arithmetic and trigonometric functions. However, there are quintic equations without closed-form solutions using elementary functions, such as x5 − x + 1 = 0.
An area of study in mathematics referred to broadly as Galois theory involves proving that no closed-form expression exists in certain contexts, based on the central example of closed-form solutions to polynomials.
## Alternative definitions
Changing the definition of "well-known" to include additional functions can change the set of equations with closed-form solutions. Many cumulative distribution functions cannot be expressed in closed form, unless one considers special functions such as the error function or gamma function to be well known. It is possible to solve the quintic equation if general hypergeometric functions are included, although the solution is far too complicated algebraically to be useful. For many practical computer applications, it is entirely reasonable to assume that the gamma function and other special functions are well-known, since numerical implementations are widely available.
## Analytic expression
An analytic expression (or expression in analytic form) is a mathematical expression constructed using well-known operations that lend themselves readily to calculation. Similar to closed-form expressions, the set of well-known functions allowed can vary according to context but always includes the basic arithmetic operations (addition, subtraction, multiplication, and division), exponentiation to a real exponent (which includes extraction of the nth root), logarithms, and trigonometric functions.
However, the class of expressions considered to be analytic expressions tends to be wider than that for closed-form expressions. In particular, special functions such as the Bessel functions and the gamma function are usually allowed, and often so are infinite series and continued fractions. On the other hand, limits in general, and integrals in particular, are typically excluded.
If an analytic expression involves only the algebraic operations (addition, subtraction, multiplication, division and exponentiation to a rational exponent) and rational constants then it is more specifically referred to as an algebraic expression.
## Comparison of different classes of expressions
Closed-form expressions are an important sub-class of analytic expressions, which contain a bounded[citation needed] or unbounded number of applications of well-known functions. Unlike the broader analytic expressions, the closed-form expressions do not include infinite series or continued fractions; neither includes integrals or limits. Indeed, by the Stone–Weierstrass theorem, any continuous function on the unit interval can be expressed as a limit of polynomials, so any class of functions containing the polynomials and closed under limits will necessarily include all continuous functions.
Similarly, an equation or system of equations is said to have a closed-form solution if, and only if, at least one solution can be expressed as a closed-form expression; and it is said to have an analytic solution if and only if at least one solution can be expressed as an analytic expression. There is a subtle distinction between a "closed-form function" and a "closed-form number" in the discussion of a "closed-form solution", discussed in (Chow 1999) and below. A closed-form or analytic solution is sometimes referred to as an explicit solution.
## Dealing with non-closed-form expressions
### Transformation into closed-form expressions
The expression:
${\displaystyle f(x)=\sum _{i=0}^{\infty }{x \over 2^{i}}}$
is not in closed form because the summation entails an infinite number of elementary operations. However, by summing a geometric series this expression can be expressed in the closed-form:[1]
${\displaystyle f(x)=2x}$
### Differential Galois theory
The integral of a closed-form expression may or may not itself be expressible as a closed-form expression. This study is referred to as differential Galois theory, by analogy with algebraic Galois theory.
The basic theorem of differential Galois theory is due to Joseph Liouville in the 1830s and 1840s and hence referred to as Liouville's theorem.
A standard example of an elementary function whose antiderivative does not have a closed-form expression is:
${\displaystyle e^{-x^{2}}}$
whose antiderivative is (up to constants) the error function:
${\displaystyle \operatorname {erf} (x)={\frac {2}{\sqrt {\pi }}}\int _{0}^{x}e^{-t^{2}}\,\mathrm {d} t.}$
### Mathematical modelling and computer simulation
Equations or systems too complex for closed-form or analytic solutions can often be analysed by mathematical modelling and computer simulation.
## Closed-form number
Three subfields of the complex numbers C have been suggested as encoding the notion of a "closed-form number"; in increasing order of generality, these are the EL numbers, Liouville numbers, and elementary numbers. The Liouville numbers, denoted L (not to be confused with Liouville numbers in the sense of rational approximation), form the smallest algebraically closed subfield of C closed under exponentiation and logarithm (formally, intersection of all such subfields)—that is, numbers which involve explicit exponentiation and logarithms, but allow explicit and implicit polynomials (roots of polynomials); this is defined in (Ritt 1948, p. 60). L was originally referred to as elementary numbers, but this term is now used more broadly to refer to numbers defined explicitly or implicitly in terms of algebraic operations, exponentials, and logarithms. A narrower definition proposed in (Chow 1999, pp. 441–442), denoted E, and referred to as EL numbers, is the smallest subfield of C closed under exponentiation and logarithm—this need not be algebraically closed, and correspond to explicit algebraic, exponential, and logarithmic operations. "EL" stands both for "Exponential-Logarithmic" and as an abbreviation for "elementary".
Whether a number is a closed-form number is related to whether a number is transcendental. Formally, Liouville numbers and elementary numbers contain the algebraic numbers, and they include some but not all transcendental numbers. In contrast, EL numbers do not contain all algebraic numbers, but do include some transcendental numbers. Closed-form numbers can be studied via transcendental number theory, in which a major result is the Gelfond–Schneider theorem, and a major open question is Schanuel's conjecture.
## Numerical computations
For purposes of numeric computations, being in closed form is not in general necessary, as many limits and integrals can be efficiently computed.
## Conversion from numerical forms
There is software that attempts to find closed-form expressions for numerical values, including RIES,[2] identify in Maple[3] and SymPy,[4] Plouffe's Inverter,[5] and the Inverse Symbolic Calculator.[6]
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http://math.stackexchange.com/questions/168617/to-show-f-is-continuous
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# To show $f$ is continuous
Let $f:[0,1]\rightarrow \mathbb{R}$ is such that for every sequence $x_n\in [0,1]$, whenever both $x_n$ and $f(x_n)$ converges , we have $$\lim_{n\rightarrow\infty} f(x_n)=f(\lim_{n\rightarrow\infty}x_n),$$ we need to prove $f$ is continuous
well, I take $x_n$ and $y_n$ in $[0,1]$ such that $|(x_n-y_n)|\rightarrow 0$, and the given condition holds,Now enough to show $|f(x_n)-f(y_n)|\rightarrow 0$
I construct a new sequence $$z_1=x_1$$ $$z_2=y_1$$ $$\dots$$ $$z_{2n-1}=x_n$$ and $$z_{2n}=y_n$$
We see, that subsequence of $f(z_n)$ converges so it must be convergent to the same limit. Am I going in right path? please help.
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Consider the function $f$ on $[0,1]$ defined by $f(0)=0$ and $f(x)=1/x$ for all $x \in (0,1]$. Then it satisfies the hypothesis but is not continuous on $[0,1]$. So the claim is false. The claim is false because the antecedent requires both $(x_n)$ and $(f(x_n))$ to be convergent. And for all $(x_n)$ that converges to $0, (f(x_n))$ is not convergent and hence the antecedent is false. Therefore the implication stands true, yet the function is not continuous on $[0,1]$! – Kasun Fernando Jul 9 '12 at 14:07
I will prove a different claim because I have pointed out that what is mentioned here is wrong by a counter-example.
Let $f:[0,1]→\mathbb{R}$ is such that for every sequence $x_n∈[0,1]$ whenever $(x_n)$ converges , we have $\lim\limits_{n→∞}f(x_n)=f \left(\lim\limits_{n→∞}x_n \right)$ then $f$ is continous on $[0,1]$.
I think the best way is to use proof by contradiction. Assume $f$ is not continuous at $c \in [0,1]$ then there exist $\epsilon_{0} > 0$ such that for all $n \in \mathbb{N}$ there exist $x_{n} \in (c-1/n,c+1/n) \cap [0,1]$ such that $|f(x_n)-f(c)| \geq \epsilon_{0}>0$
Obviously $( x_n )$ converges to $c$ but $(f(x_n))$ does not converge to $f(c)$ ( Note that all the terms of $(f(x_n))$ are a positive distance away from $f(c)$ ) which is a contradiction with the given property of the function.
Since our choice of $c$ was arbitrary, we have that $f$ is continuous on $[0,1]$
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are you assuming that $f(x_n)$ converges? why not $f(x_n)\rightarrow\infty$? – La Belle Noiseuse Jul 9 '12 at 13:39
Who cares about $f(x_n)$, as long as it does not converge to $f(x)$? – Siminore Jul 9 '12 at 13:41
I am wondering where he is using the fact given about $x_n$ and $f(x_n)$ converges together. – La Belle Noiseuse Jul 9 '12 at 13:42
Consider the function $f$ on $[0,1]$ defined by $f(0)=0$ and $f(x)=1/x$ for all non-zero $x$. Then it satisfies the hypothesis but is not continuous on $[0,1]$. So the claim is false. What I have proven is the sequential criterion for continuity! – Kasun Fernando Jul 9 '12 at 14:00
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https://repository.uantwerpen.be/link/irua/81419
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Publication
Title
Search for new physics in lepton+photon+X events with 929 $pb^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}$=1.96 TeV
Author
Institution/Organisation
CDF Collaboration
Abstract
We present results of a search at CDF in 929±56 pb-1 of pp̅ collisions at 1.96 TeV for the anomalous production of events containing a high-transverse momentum charged lepton (ℓ, either e or μ) and photon (γ), accompanied by missing transverse energy (E̸T), and/or additional leptons and photons, and jets (X). We use the same selection criteria as in a previous CDF Run I search, but with an order-magnitude larger data set, a higher pp̅ collision energy, and the CDF II detector. We find 163 ℓγE̸T+X events, compared to an expectation of 150.6±13.0 events. We observe 74 ℓℓγ+X events, compared to an expectation of 65.1±7.7 events. We find no events similar to the Run I eeγγE̸T event.
Language
English
Source (journal)
Physical review : D : particles and fields. - Lancaster, Pa, 1970 - 2003
Publication
Lancaster, Pa : 2007
ISSN
0556-2821
Volume/pages
75:11(2007), p. 112001,1-112001,15
ISI
000247625300004
Full text (Publishers DOI)
Full text (open access)
UAntwerpen
Faculty/Department Publication type Subject Affiliation Publications with a UAntwerp address
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https://www.physicsforums.com/threads/electron-in-a-one-dimensional-box.241858/
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# Homework Help: Electron in a One-Dimensional Box
1. Jun 24, 2008
### Domnu
Problem
An electron in a one-dimensional box with walls at $$x=(0,a)$$ is in the quantum state
$$\psi(x) = A, 0<x<a/2$$
$$\psi(x) = -A, a/2 < x < a$$
Obtain an expression for the normalization constant, $$A$$. What is the lowest energy of the electron that will be measured in this state?
Solution
Well, we know that
$$\int_{0}^A |\psi(x)|^2 dx = 1 \iff A^2 \cdot a = 1 \iff A = \sqrt{\frac{1}{a}}$$
so this is our normalization constant, $$A$$. Now, to find the lowest energy of the electrong that will be measured in this state, we have:
$$-\frac{\hbar^2}{2m} \frac{\partial^2 \psi}{\partial x^2} = E \psi$$
but the left hand side evaluates to 0 since $$\psi$$ is independent of $$x$$. So this is the lowest (and only observed) energy in this state... is this right?
2. Jun 24, 2008
### daschaich
Well, $$\psi$$ is independent of $$x$$ everywhere except around $$x = a / 2$$. Around there things could get a little weird. (In fact, as this problem is stated, $$\psi$$ changes infinitely quickly from one side of $$a / 2$$ to the other, so around there things could get very weird.)
Even without doing any calculations, though, you should know that since the electron is stuck in the box, it must have nonzero energy. If nothing else, the box gives it $$\Delta x < \infty$$, so it must have $$\Delta p > 0$$ by Heisenberg.
If you've already studied the infinite potential well (one-dimensional box), you might also know that the energy eigenfunctions (or stationary states) are all $$sin$$ functions (since one of the walls is at $$x = 0$$). Now, the given wavefunction $$\psi$$ is not such a $$sin$$ function, so to get the measurable energies we have to rewrite it as a sum of the energy eigenfunctions -- that is, as a Fourier series of $$sin$$ functions.
Hopefully that's enough to get you started.
3. Jun 25, 2008
### maverick280857
Well, its a step function so if you compute the derivative you get a delta function...and then a derivative of a delta function and so on.
By the way, if you solve for the wavefunction of a particle in a 1D box, you get sin or cosine functions. Any state the particle is in can be written as a linear combination of these eigenfunctions. This is a rather strange state...and interesting too
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https://brilliant.org/problems/mean-of-the-solutions-2/
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# Mean of the Solutions
Algebra Level 3
Find the mean of all of the real solutions of: $x^2+x\sqrt{x}=12x$
×
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https://math.eretrandre.org/tetrationforum/showthread.php?tid=1207&pid=8925
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• 0 Vote(s) - 0 Average
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Where is the proof of a generalized integral for integer heights? Chenjesu Junior Fellow Posts: 21 Threads: 4 Joined: May 2016 03/03/2019, 06:05 AM (This post was last modified: 03/03/2019, 06:35 AM by Chenjesu.) https://en.wikipedia.org/wiki/List_of_in..._functions Under "other integrals" it gives the integral of any integer height but provides no proof or citation. I remember seeing a paper with similar formula some time ago, but at the end it said something about its conjecture being unproven. Is there any reference that proves this integral formula? Micah Junior Fellow Posts: 9 Threads: 2 Joined: Feb 2019 03/03/2019, 07:29 AM (This post was last modified: 03/03/2019, 07:31 AM by Micah. Edit Reason: found source of interest ) Are we certain that the form posted on Wikipedia is correctly derived? Without the proof there may be no way of knowing it's correctness, We could take a look at the first few cases of the integral in order to inspect the forms, and then conjecture about a generalization from there, have you derived the first few forms of the integral? $\int\limits x^x dx = I_1$ $\int\limits x^{x^x} dx = I _2$ $\dots$ That may be a starting point for a proof. Also, I may be misinterpreting something on the wikipedia page that you posted, but shouldn't there be constants of integration in all of these antiderivatives as they do not have limits? This may also be of some use: https://en.wikipedia.org/wiki/Puiseux_series Thanks for the thought provoking question! -Micah Chenjesu Junior Fellow Posts: 21 Threads: 4 Joined: May 2016 03/03/2019, 08:55 AM (This post was last modified: 03/03/2019, 08:57 AM by Chenjesu.) I am not sure it is correct at all, that is why I am asking for the proof. I think it's likely someone found that old paper with the unproven conjecture and stuck it on wikipedia without reading it carefully. « Next Oldest | Next Newest »
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https://yaduvasudev.github.io/courses/5800/19/lectures.html
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# CS5800 Advanced Data Structures and Algorithms
## Lectures
# Date Topics covered References
1 Jul 30, 09:00 Administrative details about the course and evaluation. Introduction to algorithm design - TA allocation and stable matchings as an example. [KT] - Chapter 1
[E] - Section 4.5
2 Jul 31, 08:00 Gale-Shapley algorithm to find a stable matching, example instances, proof of correctness. [KT] - Chapter 1
[E] - Section 4.5
3 Aug 2, 12:00 Introduction to asymptotic analysis of algorithms. Implementing the Gale-Shapley algorithm - choosing the best data structures to make the implementation efficient. [KT] - Sections 2.1-2.3
[CLRS] - Chapter 3
4 Aug 5, 10:00 Divide and conquer paradigm - Karatsuba's algorithm for integer multiplication. Solving recurrence relations - guess and verify, examples. [DPV] - Section 2.1
[E] - Section 1.9
[CLRS] - Section 4.3
5 Aug 6, 09:00 Solving recurrence relations - recursion tree method, Master theorem, examples. Strassen's algorithm for matrix multiplication (check the Wikipedia page).
Optional reading: The Akra-Bazzi method for solving recurrence relations.
[E] - Section 1.7
[CLRS] - Sections 4.2-4.5
6 Aug 7, 08:00 Quicksort - example instance, proof of correctness, analyzing the recurrence. Why is an average case analysis assuming a uniformly random input unsatisfactory? Moving to randomized quicksort. [E] - Section 1.5
[CLRS] - Sections 7.1, 7.2
T1 Aug 9, 12:00 Tutorial #1.
7 Aug 13, 09:00 Basic discrete probability - sample space, random variables, expectation.
Basic notes on probability
8 Aug 14, 08:00 Linearity of expectation - examples, number of fixed-points of a random permutation, randomized algorithm for Max-3-SAT.
Setting up the analysis of randomized quicksort.
Basic notes on probability
[CLRS] - Section 7.4
9 Aug 16, 12:00 Analysis of the expected running time of randomized quicksort. Extending the idea of the partition algorithm for randomized selection. [CLRS] - Sections 7.4, 9.2
10 Aug 19, 10:00 Randomized selection - analysis of the expected number of comparisons. Linear-time selection in the worst case - median of the medians algorithm. [E] - Section 1.8
[CLRS] - Sections 9.2, 9.3
11 Aug 20, 09:00 Median of median algorithms - writing and solving the recurrence. Finding the closest pair of points in 1D - a divide-and-conquer approach. Extending the idea to points on the plane, improving the brute-force algorithm. [E] - Section 1.8
[CLRS] - Section 33.4
12 Aug 21, 08:00 Finding the closest pair of points in 2D - preprocessing the input to improve the efficiency of the divide-and-conquer algorithm. [CLRS] - Section 33.4
SE1 Aug 23, 12:00 Short exam #1.
13 Aug 26, 10:00 Lower bounds for sorting algorithms in the comparison model - decision trees and adversary arguments. Extending to stronger average-case bounds. [CLRS] - Section 8.1
[notes]
14 Aug 27, 09:00 Average-case lower bounds for sorting algorithms in the comparison model - converting full binary trees to balanced binary trees with smaller average depth.
Discussion of solutions of short exam 1.
[notes]
15 Aug 28, 08:00 Compactly representing a large text with a binary encoding. Improving over fixed-length codes using variable length codes. Notion of prefix-free codes. Constructing prefix-free codes via Shannon-Fano coding. Representing prefix-free codes as binary trees. Moving towards Huffman codes. [KT] - Section 4.8
[CLRS] - Section 16.3
T2 Aug 30, 12:00 Tutorial #2.
16 Sep 3, 09:00 Huffman coding - example. When do greedy algorithms work? - Greedy choice property and optimal substructure. Proving the correctness of Huffman's algorithm. [KT] - Section 4.8
[CLRS] - Section 16.3
[notes]
17 Sep 4, 08:00 Huffman coding - correctness of the algorithm (contd.). Implementation details - priority queues and min-heaps. [KT] - Section 4.8
[CLRS] - Section 16.3, 6.5
18 Sep 6, 12:00 Huffman coding - implementation details (contd). Minimum spanning trees - examples, greedy choices and optimal substructure. [CLRS] - Section 23.1
[notes]
Q1 Sep 7, 10:00 Quiz #1.
19 Sep 9, 10:00 Quiz #1 review. Minimum spanning trees - greedy choices and optimal substructure (contd). [CLRS] - Section 23.1
[notes]
20 Sep 10, 09:00 Graphs with distinct edge weights have unique MST. Boruvka's algorithm - example instance, correctness, analysis, implementation details. [E] - Section 7.1, 7.3
21 Sep 13, 12:00 Kruskal's algorithm - idea, implementation details. Union-Find ADT and its implementation. Obtaining a running time of $$O(m \log n)$$ for Kruskal's algorithm using a simple Union-Find data structure. [KT] - Section 4.6
[notes]
22 Sep 16, 10:00 Implementing Union-Find using union-by-rank - analyzing the worst case complexity. The path compression heuristic - algorithm and worst case analysis. [KT] - Section 4.6
[notes]
23 Sep 17, 09:00 Amortized analysis of algorithms - aggregate method and accounting method. Examples - incrementing a binary counter, maintaining a dynamic table with insertions. [CLRS] - Section 17.1, 17.2, 17.4
24 Sep 18, 08:00 Analysis of path compression - obtaining the amortized $$O(\log^* n)$$ bound using a clever use of the accounting method. Implications for the running time of Kruskal's algorithm for finding MST. [KT] - Section 4.6
[DPV] - Section 5.1.4
T3 Sep 20, 12:00 Tutorial #3.
25 Sep 23, 10:00 Prim's algorithm - implementation using binary heaps. Improving the amortized complexity of decrease-min using better implementations of priority queues. Binomial trees and binomial heaps. [CLRS] - Section 23.2
[class notes]
SE2 Sep 27, 12:00 Short exam #2.
26 Oct 1, 09:00 Algorithms for binomial heaps. Improving the worst-case complexity of insert and merge by postponing the book-keeping. Extract-min in lazy binomial heaps. [class notes]
[Kaplan and Zwick's slides]
27 Oct 9, 08:00 Extract-min in lazy binomial heaps - amortized analysis using the potential method. Naive approach to improving the complexity of decrease key operation. [class notes]
[Erickson's notes]
[Kaplan and Zwick's slides]
[CLRS] - Section 17.3
28 Oct 11, 12:00 Decrease-key operation using cascading cuts. Bounding the degree of the trees. Amortized analysis of Fibonacci heap operations using the potential method. [class notes]
[Erickson's notes]
[Kaplan and Zwick's slides]
[CLRS] - Section 17.3
29 Oct 14, 10:00 Shortest paths in digraphs - optimal substructure property. Introduction to dynamic programming - characterizing the solution, writing the recurrence relation. Bellman-Ford recurrence for single-source shortest path. [class notes]
[E] - Section 8.7
30 Oct 15, 09:00 Bellman-Ford recurrence for single-source shortest path - expressing the algorithm in a bottom-up manner. Extending the idea to all-pairs shortest path problem. The Fischer-Meyer idea - a different recurrence and a faster algorithm. [class notes]
[E] - Section 8.7, 9.5, 9.6
31 Oct 16, 08:00 All pairs shortest path - Floyd-Warshall algorithm. Dynamic programming on strings and sequences - text justification. [class notes]
[E] - Section 9.8
32 Oct 18, 12:00 Dynamic programming on strings and sequences (contd.) - text justification and edit distance. [E] - Section 3.7
[KT] - Section 6.6
Q2 Oct 19, 09:30 Quiz 2.
33 Oct 22, 09:00 Review of Quiz 2. Dynamic programming on strings and sequences (contd.) - saving space for edit distance using divide and conquer. [E] - Section 3.7
[KT] - Section 6.6
34 Oct 23, 08:00 Dynamic programming on strings and sequences (contd.) - linear space algorithm for edit distance using divide and conquer. Dynamic programming on sets - subset sum and knapsack. Notion of peudo-polynomial time. [KT] - Section 6.4, 6.7
35 Oct 25, 12:00 Two variants of knapsack problem - pseudo-polynomial time algorithm. Independent set problem on restricted classes of graphs - paths and trees. [class notes]
[KT] - Section 6.4
[DPV] - Section 6.4
36 Oct 26, 09:30 Maxflow problem - greedy method, correcting wrong greedy choices using a residual graph. Augmenting paths to improve flows, examples. Ford-Fulkerson method - augmenting flows using the residual graph, examples. Proving that the Ford-Fulkerson method terminates with a feasible flow. [class notes]
[KT] - Section 7.1
37 Oct 28, 10:00 Correctness of the Ford-Fulkerson method. Notion of an s-t cut, existence of a cut with value of the maxflow, maxflow-mincut theorem, proof that an integral flow network contains an integral maxflow. [class notes]
[KT] - Section 7.2
38 Oct 29, 09:00 Example instance where Ford-Fulkerson algorithm takes exponential time to converge to the maxflow. Methods to improve the running time: augmenting via the fattest path - algorithm and the idea behind the analysis, augmenting via the path with the least number of edges. [Trevisan's notes]
39 Oct 30, 08:00 Edmonds-Karp/Dinitz algorithm - augmenting via the shortest path, brief overview of the running time bound. Application of the maxflow-mincut theorem and algorithm - maximum matching in bipartite graphs. [class notes]
[Trevisan's notes] - Section 2
40 Nov 1, 12:00 Applications of the maxflow-mincut theorem - König-Egerváry theorem, Hall's theorem characterizing perfect matchings in bipartite graphs. [class notes]
41 Nov 4, 10:00 Algorithmic questions that were considered during the course, and some of their variants. Connections between optimization problems and decision problems. Aiming for a theory of computational complexity. [class notes]
42 Nov 5, 09:00 Definition of the class NP - short witnesses that can be verified efficiently. Comparing the complexity of problems using polynomial-time reductions. Cook-Levin theorem (statement) and the concept of NP-completeness. [class notes]
43 Nov 6, 08:00 Examples of many-one reductions - 3SAT, Independent Set, Vertex Cover and Clique. [class notes]
SE3 Nov 8, 12:00 Short exam #3.
44 Nov 11, 10:00 Going beyond NP-completeness: Exact exponential algorithms and approximation algorithms. Wrap-up of the course.
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https://www.physicsforums.com/threads/field-of-zero-characteristics.949581/
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# I Field of zero characteristics
Tags:
1. Jun 14, 2018
### Danijel
I am interested in the following theorem:
Every field of zero characteristics has a prime subfield isomorphic to ℚ.
I am following the usual proof, where we identify every p∈ℚ as a/b , a∈ℤ,beℕ, and define h:ℚ→P as h(a/b)=(a*1)(b*1)-1 (where a*1=1+1+1... a times) I have worked out the multiplicative rule for this homomorphism, but I am not sure how to prove the additive. I am also interested in what does the notation
(a*1)(b*1)-1 exactly mean. Thanks.
2. Jun 14, 2018
### Staff: Mentor
All we know about the prime field is its characteristic and $0,1 \in \mathbb{P}$. $a\in \mathbb{P}$ is not sure. However $\underbrace{1+\ldots +1}_{a \text{ times}}=a \,\cdot \, 1$ for $a \in \mathbb{N}$ is, and likewise for negative $a$. That's why $a$ times $1$ is used instead of $a$. We only have isomorphic images of $a$ in $\mathbb{P}$.
For the homomorphism, I guess $\dfrac{a}{b}+\dfrac{c}{d}=\dfrac{ad+bc}{bd}$ will be needed.
3. Jun 14, 2018
### mathwonk
this probably won't help much until you have some commutative algebra but it gives the outline. First of all since the field F is an abelian group, there is exactly one additive homomorphism from the integers Z into F for each choice of the image of 1 from Z, so choose that image to be the unit element 1 in P. Now you have the unique additive homomorphism from Z to P that fresh described sending each positive integer n to 1+...+1 (n times). By definition of the multiplication in Z this is also a multiplicative map hence a ring map. Then since each non zero integer goes to an invertible element of F, (because F has characteristic zero), there is a unique extension of the previously defined ring homomorphism Z-->F to a ring homomorphism Q --> F. Then since Q is a field, this ring map is necessarily injective, hence defines an isomorphism onto the smallest subfield of F, i.e. the prime field.
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https://brilliant.org/problems/trickier-logs/
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# Trickier logs
Level pending
Find the value of
$$\log(\tan(1))+\log(\tan(2))+\dots+\log(\tan(89))$$
where $$\log$$ is the natural logarithm and all angles are in degrees.
×
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https://kr.mathworks.com/help/matlab/math/solve-system-of-pdes.html?lang=en
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# Solve System of PDEs
This example shows how to formulate, compute, and plot the solution to a system of two partial differential equations.
Consider the system of PDEs
$\frac{\partial {\mathit{u}}_{1}}{\partial \mathit{t}}=0.024\frac{{\partial }^{2}{\mathit{u}}_{1}}{\partial {\mathit{x}}^{2}}-\mathit{F}\left({\mathit{u}}_{1}-{\mathit{u}}_{2}\right),$
$\frac{\partial {\mathit{u}}_{2}}{\partial \mathit{t}}=0.170\frac{{\partial }^{2}{\mathit{u}}_{2}}{\partial {\mathit{x}}^{2}}+\mathit{F}\left({\mathit{u}}_{1}-{\mathit{u}}_{2}\right).$
(The function $\mathit{F}\left(\mathit{y}\right)={\mathit{e}}^{5.73\mathit{y}}-{\mathit{e}}^{-11.46\mathit{y}}$ is used as a shorthand.)
The equation holds on the interval $0\le \mathit{x}\le 1$ for times $\mathit{t}\ge 0$. The initial conditions are
${\mathit{u}}_{1}\left(\mathit{x},0\right)=1,$
${\mathit{u}}_{2}\left(\mathit{x},0\right)=0.$
The boundary conditions are
$\begin{array}{l}\frac{\partial }{\partial \mathit{x}}{\mathit{u}}_{1}\left(0,\mathit{t}\right)=0,\\ {\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathit{u}}_{2}\left(0,\mathit{t}\right)=0,\\ \frac{\partial }{\partial \mathit{x}}{\mathit{u}}_{2}\left(1,\mathit{t}\right)=0,\\ {\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathit{u}}_{1}\left(1,\mathit{t}\right)=1.\end{array}$
To solve this equation in MATLAB®, you need to code the equation, the initial conditions, and the boundary conditions, then select a suitable solution mesh before calling the solver pdepe. You either can include the required functions as local functions at the end of a file (as done here), or save them as separate, named files in a directory on the MATLAB path.
### Code Equation
Before you can code the equation, you need to make sure that it is in the form that the pdepe solver expects:
$\mathit{c}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right)\frac{\partial \mathit{u}}{\partial \mathit{t}}={\mathit{x}}^{-\mathit{m}}\frac{\partial }{\partial \mathit{x}}\left({\mathit{x}}^{\mathit{m}}\mathit{f}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right)\right)+\mathit{s}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right).$
In this form, the PDE coefficients are matrix-valued and the equation becomes
$\left[\begin{array}{cc}1& 0\\ 0& 1\end{array}\right]\frac{\partial }{\partial \mathit{t}}\left[\begin{array}{c}{\mathit{u}}_{1}\\ {\mathit{u}}_{2}\end{array}\right]=\frac{\partial }{\partial \mathit{x}}\left[\begin{array}{c}0.024\frac{\partial {\mathit{u}}_{1}}{\partial \mathit{x}}\\ 0.170\frac{\partial {\mathit{u}}_{2}}{\partial \mathit{x}}\end{array}\right]+\left[\begin{array}{c}-\mathit{F}\left({\mathit{u}}_{1}-{\mathit{u}}_{2}\right)\\ \mathit{F}\left({\mathit{u}}_{1}-{\mathit{u}}_{2}\right)\end{array}\right].$
So the values of the coefficients in the equation are
$\mathit{m}=0$
$\mathit{c}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right)=\left[\begin{array}{c}1\\ 1\end{array}\right]$ (diagonal values only)
$\mathit{f}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right)=\left[\begin{array}{c}0.024\frac{\partial {\mathit{u}}_{1}}{\partial \mathit{x}}\\ 0.170\frac{\partial {\mathit{u}}_{2}}{\partial \mathit{x}}\end{array}\right]$
$\mathit{s}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right)=\left[\begin{array}{c}-\mathit{F}\left({\mathit{u}}_{1}-{\mathit{u}}_{2}\right)\\ \mathit{F}\left({\mathit{u}}_{1}-{\mathit{u}}_{2}\right)\end{array}\right]$
Now you can create a function to code the equation. The function should have the signature [c,f,s] = pdefun(x,t,u,dudx):
• x is the independent spatial variable.
• t is the independent time variable.
• u is the dependent variable being differentiated with respect to x and t. It is a two-element vector where u(1) is ${\mathit{u}}_{1}\left(\mathit{x},\mathit{t}\right)$ and u(2) is ${\mathit{u}}_{2}\left(\mathit{x},\mathit{t}\right)$.
• dudx is the partial spatial derivative $\partial \mathit{u}/\partial \mathit{x}$. It is a two-element vector where dudx(1) is $\partial {\mathit{u}}_{1}/\partial \mathit{x}$ and dudx(2) is $\partial {\mathit{u}}_{2}/\partial \mathit{x}$.
• The outputs c, f, and s correspond to coefficients in the standard PDE equation form expected by pdepe.
As a result, the equations in this example can be represented by the function:
function [c,f,s] = pdefun(x,t,u,dudx)
c = [1; 1];
f = [0.024; 0.17] .* dudx;
y = u(1) - u(2);
F = exp(5.73*y)-exp(-11.47*y);
s = [-F; F];
end
(Note: All functions are included as local functions at the end of the example.)
### Code Initial Conditions
Next, write a function that returns the initial condition. The initial condition is applied at the first time value and provides the value of $\mathit{u}\left(\mathit{x},{\mathit{t}}_{0}\right)$ for any value of x. The number of initial conditions must equal the number of equations, so for this problem there are two initial conditions. Use the function signature u0 = pdeic(x) to write the function.
The initial conditions are
${\mathit{u}}_{1}\left(\mathit{x},0\right)=1,$
${\mathit{u}}_{2}\left(\mathit{x},0\right)=0.$
The corresponding function is
function u0 = pdeic(x)
u0 = [1; 0];
end
### Code Boundary Conditions
Now, write a function that evaluates the boundary conditions
$\begin{array}{l}\frac{\partial }{\partial \mathit{x}}{\mathit{u}}_{1}\left(0,\mathit{t}\right)=0,\\ {\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathit{u}}_{2}\left(0,\mathit{t}\right)=0,\\ \frac{\partial }{\partial \mathit{x}}{\mathit{u}}_{2}\left(1,\mathit{t}\right)=0,\\ {\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\mathit{u}}_{1}\left(1,\mathit{t}\right)=1.\end{array}$
For problems posed on the interval $\mathit{a}\le \mathit{x}\le \mathit{b}$, the boundary conditions apply for all $\mathit{t}$ and either $\mathit{x}=\mathit{a}$ or $\mathit{x}=\mathit{b}$. The standard form for the boundary conditions expected by the solver is
$\mathit{p}\left(\mathit{x},\mathit{t},\mathit{u}\right)+\mathit{q}\left(\mathit{x},\mathit{t}\right)\mathit{f}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right)=0.$
Written in this form, the boundary conditions for the partial derivatives of $\mathit{u}$ need to be expressed in terms of the flux $\mathit{f}\left(\mathit{x},\mathit{t},\mathit{u},\frac{\partial \mathit{u}}{\partial \mathit{x}}\right)$. So the boundary conditions for this problem are
For $\mathit{x}=0$, the equation is
$\left[\begin{array}{c}0\\ {\mathit{u}}_{2}\end{array}\right]+\left[\begin{array}{c}1\\ 0\end{array}\right]\cdot \left[\begin{array}{c}0.024\frac{\partial {\mathit{u}}_{1}}{\partial \mathit{x}}\\ 0.170\frac{\partial {\mathit{u}}_{2}}{\partial \mathit{x}}\end{array}\right]=0.$
The coefficients are:
${\mathit{p}}_{\mathit{L}}\left(\mathit{x},\mathit{t},\mathit{u}\right)=\left[\begin{array}{c}0\\ {\mathit{u}}_{2}\end{array}\right],$
${\mathit{q}}_{\mathit{L}}\left(\mathit{x},\mathit{t}\right)=\left[\begin{array}{c}1\\ 0\end{array}\right].$
Likewise, for $\mathit{x}=1$ the equation is
$\left[\begin{array}{c}{\mathit{u}}_{1}-1\\ 0\end{array}\right]+\left[\begin{array}{c}0\\ 1\end{array}\right]\cdot \left[\begin{array}{c}0.024\frac{\partial {\mathit{u}}_{1}}{\partial \mathit{x}}\\ 0.170\frac{\partial {\mathit{u}}_{2}}{\partial \mathit{x}}\end{array}\right]=0.$
The coefficients are:
${\mathit{p}}_{\mathit{R}}\left(\mathit{x},\mathit{t},\mathit{u}\right)=\left[\begin{array}{c}{\mathit{u}}_{1}-1\\ 0\end{array}\right],$
${\mathit{q}}_{\mathit{R}}\left(\mathit{x},\mathit{t}\right)=\left[\begin{array}{c}0\\ 1\end{array}\right].$
The boundary function should use the function signature [pl,ql,pr,qr] = pdebc(xl,ul,xr,ur,t):
• The inputs xl and ul correspond to $\mathit{u}$ and $\mathit{x}$ for the left boundary.
• The inputs xr and ur correspond to $\mathit{u}$ and $\mathit{x}$ for the right boundary.
• t is the independent time variable.
• The outputs pl and ql correspond to ${\mathit{p}}_{\mathit{L}}\left(\mathit{x},\mathit{t},\mathit{u}\right)$ and ${\mathit{q}}_{\mathit{L}}\left(\mathit{x},\mathit{t}\right)$ for the left boundary ($\mathit{x}=0$ for this problem).
• The outputs pr and qr correspond to ${\mathit{p}}_{\mathit{R}}\left(\mathit{x},\mathit{t},\mathit{u}\right)$ and ${\mathit{q}}_{\mathit{R}}\left(\mathit{x},\mathit{t}\right)$ for the right boundary ($\mathit{x}=1$ for this problem).
The boundary conditions in this example are represented by the function:
function [pl,ql,pr,qr] = pdebc(xl,ul,xr,ur,t)
pl = [0; ul(2)];
ql = [1; 0];
pr = [ur(1)-1; 0];
qr = [0; 1];
end
### Select Solution Mesh
The solution to this problem changes rapidly when $\mathit{t}$ is small. Although pdepe selects a time step that is appropriate to resolve the sharp changes, to see the behavior in the output plots you need to select appropriate output times. For the spatial mesh, there are boundary layers in the solution at both ends of $0\le \mathit{x}\le 1$, so you need to specify mesh points there to resolve the sharp changes.
x = [0 0.005 0.01 0.05 0.1 0.2 0.5 0.7 0.9 0.95 0.99 0.995 1];
t = [0 0.005 0.01 0.05 0.1 0.5 1 1.5 2];
### Solve Equation
Finally, solve the equation using the symmetry $\mathit{m}$, the PDE equation, the initial conditions, the boundary conditions, and the meshes for $\mathit{x}$ and $\mathit{t}$.
m = 0;
sol = pdepe(m,@pdefun,@pdeic,@pdebc,x,t);
pdepe returns the solution in a 3-D array sol, where sol(i,j,k) approximates the kth component of the solution ${\mathit{u}}_{\mathit{k}}$ evaluated at t(i) and x(j). Extract each solution component into a separate variable.
u1 = sol(:,:,1);
u2 = sol(:,:,2);
### Plot Solution
Create surface plots of the solutions for ${\mathit{u}}_{1}$ and ${\mathit{u}}_{2}$ plotted at the selected mesh points for $\mathit{x}$ and $\mathit{t}$.
surf(x,t,u1)
title('u_1(x,t)')
xlabel('Distance x')
ylabel('Time t')
surf(x,t,u2)
title('u_2(x,t)')
xlabel('Distance x')
ylabel('Time t')
### Local Functions
Listed here are the local helper functions that the PDE solver pdepe calls to calculate the solution. Alternatively, you can save these functions as their own files in a directory on the MATLAB path.
function [c,f,s] = pdefun(x,t,u,dudx) % Equation to solve
c = [1; 1];
f = [0.024; 0.17] .* dudx;
y = u(1) - u(2);
F = exp(5.73*y)-exp(-11.47*y);
s = [-F; F];
end
% ---------------------------------------------
function u0 = pdeic(x) % Initial Conditions
u0 = [1; 0];
end
% ---------------------------------------------
function [pl,ql,pr,qr] = pdebc(xl,ul,xr,ur,t) % Boundary Conditions
pl = [0; ul(2)];
ql = [1; 0];
pr = [ur(1)-1; 0];
qr = [0; 1];
end
% ---------------------------------------------
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|
https://www.aimsciences.org/article/doi/10.3934/dcdsb.2008.10.783
|
# American Institute of Mathematical Sciences
September 2008, 10(4): 783-799. doi: 10.3934/dcdsb.2008.10.783
## Kawahara equation in a bounded domain
1 Departamento de Matemática, Universidade Estadual de Maringá, 87020-900, Maringá, Brazil, Brazil
Received August 2007 Revised May 2008 Published August 2008
This paper deals with an initial-boundary value problem for the nonlinear one-dimensional Kawahara equation posed on a bounded interval. For reasonable initial and boundary conditions we prove the existence and uniqueness of a global regular solution subject to dispersive smoothing. We also show the exponential decay of the obtained solution as $t\to\infty$ and its asymptotics while the coefficient of the higher derivative approaches zero.
Citation: Gleb G. Doronin, Nikolai A. Larkin. Kawahara equation in a bounded domain. Discrete & Continuous Dynamical Systems - B, 2008, 10 (4) : 783-799. doi: 10.3934/dcdsb.2008.10.783
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2018 Impact Factor: 1.008
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|
https://thegradient.pub/symmetries-scaffolds-and-a-new-era-of-scientific-discovery/
|
# Symmetries, Scaffolds, and a New Era of Scientific Discovery
### The Challenge of Drug Discovery
The development of new medicines is often laborious, time-consuming, costly, and prone to failure. The failure rate is notoriously high, with the most recent statistic being 90% [1,2]. The range of potential drug-like molecules is estimated to be between $10^{23}$ and $10^{60}$, resulting in a large and discrete search space, while it is predicted that “only” about $10^8$ molecular substances have been synthesised [3]. The chemical space of molecular candidates is vast, and within this space, interesting and powerful drugs are waiting to be found.
Impactful drugs, like the discovery of thalidomide or penicillin, have changed the course of medicine and shaped the field. However, the first drug is notorious for being part of the thalidomide tragedy, which caused birth defects and deaths among pregnant women in the 1960s [4]. The root cause was ignored handedness (or, in jargon, the chirality) between the molecular compounds, i.e. molecules that are non-superimposable on their mirror images with regards to a symmetry axis [5]. A left-handed compound might have different pharmacological properties than a right-handed compound; could it yield a toxin, or could it yield the next “wonder drug”?
The study of symmetry, along with a better understanding of the functioning of the molecules, is therefore vital to the drug development pipeline. However, existing research is predominantly focused on the study of 1-D and 2-D molecular representations, instead of leveraging the full geometrical information within these models. Developing tools to leverage the geometrical information and efficiently navigate the search space is one of the core challenges in modern chemistry. Fortunately, the field of geometric deep learning, a field that exploits the symmetries of machine learning models in non-Euclidean domains [6], is increasingly being used to speed up nearly every stage of the drug development pipeline. From the prediction of the physicochemical properties of a particular compound to clinical development, while respecting the geometry of the task at hand [7] -- they all contribute to addressing the grand challenges facing drug discovery. This article will cover how the application of geometric deep learning and the field of molecular machine learning is ushering us into a new era of scientific discovery.
### A Brief History of Computer-Aided Drug Discovery
For the past three decades, computer-aided discovery and design methods have been a significant contributor to the development of relatively small, therapeutic molecules [8]. Ever since, there has been a considerable increase in the amount of public quantitative molecular bioactivity data and biomedical data on the effects of a molecule on a living system [9,10]. Due to this steep increase in the amount of data, it quickly becomes infeasible to mine knowledge by hand to generate new insights; automated tools, such as machine learning algorithms, form one solution to this problem. Simplified correlations can be inferred between the input elements that retain the necessary information required to get to the desired outcome. This gives room to accommodate more data, however, explainability and scientific accuracy (not statistical accuracy) can be compromised.
The use of deep learning has proven to be highly successful in data-rich fields such as computer vision, natural language processing, and speech recognition [11]. Building upon these successes, deep learning is increasingly being applied to problems in the natural sciences, which includes the field of chemistry. Traditional advances in chemistry have combined the implementation of novel experiments with analytic theory, which mirrors the classical scientific method by developing falsifiable hypotheses. Now, as we are steering more into the era of big data, computer-aided approaches are gradually being applied to accelerate our scientific research and understanding. Similarly, these methods allow for data-driven research that generates falsifiable hypotheses which are then tested [12].
Data-driven applications have increasingly been shown to accelerate solving diverse problems in the drug discovery pipeline [13] -- from the use of predictive analytical methods in high-throughput screening to the use of generative models for discovering and designing novel compounds. While the exploration of the chemical space is beneficial, it unfortunately lacks the ability to discover novel and unknown chemical compounds. The main reason for this is that the current chemical space, which is merely a fraction of the active chemical space, is limited to established, well-known compounds.
One of the most significant advances in the field of molecular machine learning is the ability to predict the physicochemical properties of specific drugs. The first approach included the use of Quantitative Structure-Activity Relationship (QSAR) models. These models use molecular descriptors to predict the physicochemical properties and biological activities of molecular compounds in regression and classification tasks [14]. Through advances in artificial intelligence, the paradigm shifted more to the use of deep learning models. Classical machine learning methods, such as regression models, still outperform deep learning methods at certain complex benchmark tasks due to the limited data availability [15].
We can represent molecular structures in several distinct ways, as seen in Figure 2. Developing a one-size-fits-all and generalizable solution is a significant challenge, as these representations capture and reflect different valid configurations of the same molecular instance. To this end, existing methods from natural language processing have been adopted, such as the use of sequence-based models (e.g. recurrent neural networks [18] and Transformers [19]) to tackle 1D and 2D structures, or graph neural networks (GNNs) for handling 3D representations. There can be many simplified molecular-input line-entry specification (SMILES) strings that all represent the same graph, while a recurrent model needs to learn to map all valid permutations of the SMILES string to the same output. A GNN, which inherently respects permutation symmetries, handles this more elegantly.
The properties and interactions of a molecule are not only based on the interatomic bonds and the information provided in a molecular graph, but are also determined by the underlying physical interactions between the atoms, which depend on their 3D geometry [20]. Because of this, 3D molecular representations encode the full geometry of the molecule and thus bring in more information. This is especially useful when determining whether a molecule is the right fit for a binding receptor on a cell membrane.
Including 3D information about molecules as additional input to a machine learning model is expected to result in a more expressive and realistic method of defining their dynamics. The field of geometric deep learning (GDL) allows us to leverage the intrinsic geometrical features of a molecule and enhance the quality of our models. In recent years, GDL has repeatedly proven to be useful in generating insights on relevant molecular properties, as a result of its natural feature extraction capabilities, which will be discussed below [6].
### Symmetries, Chiralities, and Geometric Deep Learning
Physical systems and their interactions are inherently equivariant [21]: orientations within the system should not change the physical laws that govern the behaviour and properties of interacting elements. In the field of GDL, symmetry is considered to be an indispensable topic, as it encompasses the properties of an arbitrary coordinate system with respect to transformations such as translations, reflections, rotations, scalings, or permutations [17].
Traditional machine learning models make no assumption of symmetry (and hence, are not symmetry-aware), and are sensitive to the choice of coordinate system. To be able to recognize an n-dimensional pattern in any orientation, such a model needs to explicitly be passed every possible configuration and permutation of an input (such as an image) to understand all input cases. To avoid having to augment the data a multitude of times, one could leverage the geometry of the image. Leveraging the geometry of the task at hand is not a novel concept -- in the field of image analysis, when considering a 2-D image, convolutional neural networks (CNNs) are able to detect an object irrespective of its position within the image. By respecting the geometry of the task at hand, the model learns more efficiently, as one can significantly reduce the number of trainable parameters [22].
In machine learning, the notion of symmetry is often recast in terms of invariance and equivariance. These express the behaviour of any mathematical function with respect to a transformation $T$ of an acting symmetry group [23]. Based on the definitions provided in [17], we illustrate these concepts below. We take a mathematical function, $F$, which we apply to a given input, $X$. $F(X)$ can therein transform equivariantly or invariantly:
• Equivariance: A function $F$ applied to an input $X$ is equivariant to a transformation $T$ if the transformation of $X$ commutes with the transformation of $F(X)$, via a transformation $T$ of the same symmetry group, such that: $F(T(X)) = T(F(X))$.
• Invariance: Invariance is a special case of equivariance, where $F(X)$ is invariant to $T$ if $T$ is the trivial group action (i.e., identity): $F(T(X)) = T(F(X)) = F(X)$.
Or, in other words, equivariance deals with the notion that one transforms the output in the same way one transforms the input, while invariance deals with the notion that transformations of the input do not affect the output, as visible in Figure 3.
For molecules, relevant transformations within the 3D space involve rotations, and translations are part of a symmetry group under which a system is invariant. This symmetry group is denoted as the special Euclidean group in 3 dimensions, SE(3). The difference between the Euclidean group in 3 dimensions, E(3), is the omission of the reflection as a valid transformation. This principle introduces us to the notion of translation invariance: for a molecule of atoms, translating our input coordinates $r_1, \dots, r_n$ by $g \in R_3$ to become $r_{1} +g, \dots, r_{n} +g$, which should not change the output of the model [20].
However, this is not entirely true for chiral molecules, as transforming the molecular representation does change the molecule. Their biological and pharmacological properties can significantly change depending on the handedness of the molecule. This is exemplified by enantiomers, which are pairs of molecules that are mirror images of each other, but have different pharmacological properties [25].
Enantiomers can have very different effects -- mirroring an enantiomer could either yield a lead candidate or a deadly toxin [26]. With this in mind, it would be desirable to consider machine learning systems that take into account the symmetry of the task at hand. Thus, integrating symmetry into these modelling tasks has recently been considered a valuable addition to the model to represent these systems and interactions more faithfully. Some recent papers have leveraged this technique within the field of molecular design, of which two will be briefly explained below.
### E(n) Equivariant Normalizing Flows
To understand the functioning of the normalizing flow, we first start by considering the class of generative models. Under the umbrella term of generative models, we consider (1) energy-based models, (2) variational autoencoders, (3) generative adversarial networks, (4) normalizing flows, and (5) diffusion models.
Mathematically defined, generative models typically consist of two elements, which are a distribution $p_z$ and a learnable function $g: z \rightarrow x$, where $z$ denotes the latent space and $x$ denotes an arbitrary point in the sample space. Discriminative models, on the other hand, have a learnable function of the form $g: x \rightarrow y$, where $x$ denotes an arbitrary point in the sample space, and $y$ denotes the labels of the learned features in the feature space. The difference lies in how $g$ is learned, i.e. what the objective function is. Generative models aim to model the training distribution in order to sample new data points, whilst discriminative models aim to model the decision boundary between classes.
While the aforementioned generative models all share distinct objectives, they may not necessarily learn the exact probability density function $p(x)$ and likelihood, which are both difficult to compute. This is where the class of normalizing flows come in. The likelihood of a point $x$ can be found by inverting the learnable function $g^{-1}$ and going back to a point in the latent space $z$, which is done through a slight change in the variables. Applying normalizing flows to molecular instances, in this case, generating molecular features and 3-D positions, would require the positional information of nodes $x \in R^{M\times n}$, where $M$ denotes the number of nodes present in the $n$-dimensional space. An atom type is represented by $h$, where $h$ is the representation in $R^{M \times nf}$. The discrete features $h$ are mapped into a continuous latent space, yielding the following for the change of variables formula [27,28].
The learnable function $f$ is constructed by the development of a Neural Ordinary Differential Equation (NODE) of which the dynamics are governed by an E(n) Equivariant Graph Neural Network (E-GNN) [29]. In differential equations, we would simply aim to find the derivative of a function. However, ordinary differential equations use the concept of evolution of the derivative that slowly converges towards an analytical estimate of the solution. Integrating the NODE collects all the terms for the likelihood, among which lies the base distribution on the output $\log P_z(z_x, z_h)$ [28]. Taken all together, this would yield the following procedure:
It was found that the E-NF significantly outperformed non-equivariant models in terms of log-likelihood and that it produced 85% valid atom configurations based on 10.000 generated examples. Using the method, 4.91% were stable, and of this subset, 99.80% were unique and 93.28% were novel.
### E(3) Equivariant Diffusion Models
A more recent method is the use of E(3) Equivariant Diffusion Models for molecule generation [30,31]. Diffusion models fall under the same class of generative models, which have been described above. However, the sampling procedure differs. Let us recall that we have the positional information $x$ of the nodes and $h$ denoting the different atom types. A forward diffusion process is defined by adding a small amount of Gaussian noise to the sample in $T$, producing a sequence of noisy samples $x_1, \dots, x_t$, with a controlled step size [32]. In other words, diffusion models are trained to reverse this noising process. In order to generate new samples at inference time, one starts with a Gaussian distribution and uses the trained diffusion model to remove noise stepwise until one arrives at a "final" sample. Comparing this approach to the previous method, it was found that it significantly outperforms state-of-the-art generative methods in terms of the scalability, quality, and efficiency of the network. Bringing this together yields the following procedure:
In comparison to the E-NF, EDMs are able to generate 16x more stable molecules than E-NF, while only using half of the training time, which significantly increases the amount of (novel) compounds available. The more stable and testable compounds there are, the higher the probability of finding a novel candidate in the high-throughput screening phase that might work. However, what is important to note is that stability is a trivial metric for in silico design as all drug molecules must be stable. Nonetheless, a more relevant metric would be synthesizability (which refers to the steps needed to synthesise the molecule) because many stable, generated molecules are nowhere near synthesizable [33].
However, if we put the presented numbers from both studies in perspective -- typical success rates (so-called “hit-rates”, which showcase the most optimal molecule based on their bioactivity) from human-based experimental methods are in the range of 0.01-0.14%, while virtual screen rates are between 1-40% [34], showing a significant increase in finding the best compounds. It must be noted that the experiments described in both of the studies are done on datasets with a small number of samples.
At the scale of real-world applications, integrating the full geometric information would require an incredible amount of computational resources. Alternatives have been proposed, for example in [20], which provides a novel approach to implicitly integrating the 3D geometry of molecules into the neural network’s learning process, while only requiring 2D molecular graphs when using the network to make predictions. While using more detailed representations (i.e. 2D -> 3D -> beyond) is a step in the right direction, the availability of data drastically drops. The real-world performance of these models is bottlenecked by the availability of high-quality geometric data (unlike the benchmark datasets in academic papers). To make further progress, we need to start thinking about data generation. Even though the recent methods have demonstrated their success in small-scale case studies, and there might be more on the horizon -- this might just be a glimpse of the undiscovered iceberg of future drug candidates.
### A New Era of Scientific Discovery?
We have seen how machine learning can accelerate the process of traditional drug discovery, and it is undeniable that it will act as a strong catalyst for future research.
Using computer-aided methods for drug discovery significantly reduces the monetary and human resources spent on the screening procedure, as they can find suitable lead candidates faster, and devote less time to synthesising non-promising compounds. This aids us in our understanding of how drug candidates work, as these models add an extra layer to the preclinical drug discovery funnel. This brings us to the prospect of lowering costs for drug development, with the eventual grand objective to develop drugs for rare diseases. This paradigm shift can potentially complement our current biological and chemical understanding of the natural and physical sciences.
The recent advances in AI have great potential to reinvent the status quo and rethink and accelerate how we tackle the many global, societal challenges we face. It is undeniable that their influence will only increase in the coming years. With the advent of Moore’s Law in 1965, which has been considered a driving force of technological innovation and social change, this is not going to change anytime soon. What was unimaginable generations ago becomes imaginable. Molecules are vital to life as we know it. They carry information to our cells from other cells, our food, the air we breathe, and the drugs we take. Their complexity means that they are both fundamental to biology whilst still being poorly understood. However, advances in our understanding of the physicochemical properties of molecules and how these properties interact with cells are expected to usher in a new era of drug discovery. It is very possible that the era has just begun.
### Author Bio
Meilina Reksoprodjo is an MSc student in Data Science in Engineering at the Eindhoven University of Technology (TU/e), specializing in explainable AI & geometric deep learning in the context of drug discovery. She holds a BSc degree in Artificial Intelligence from Radboud University. For more updates, she is active on Twitter or Linkedin.
### Acknowledgements
The author is grateful to Marco Cognetta, David D, Lin Min Htoo, Koen Minartz, Rıza Ozcelik, Tadija Radusinović, Maxim Snoep, Dr. Namid Stillman, Esther Shi, Koen Smeets, Sang Truong, Joost van der Haar, Stefan van der Sman, Derek van Tilborg and Dr. Yew Mun Yip for proofreading this article and providing valuable input for improving the text.
### Citation
Meilina Reksoprodjo, "Symmetries, Scaffolds, and a New Era of Scientific Discovery", The Gradient, 2022.
BibTeX citation:
@article{reksoprodjooverview2022,
author = {Meilina Reksoprodjo},
title = {Symmetries, Scaffolds, and a New Era of Scientific Discovery},
year = {2022},
}
### Bibliography
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[2] A. Mullard, "Parsing clinical success rates", Nature Reviews Drug Discovery, vol. 15, no. 7, pp. 447-447, 2016. Available: 10.1038/nrd.2016.136.
[3] R. Gómez-Bombarelli et al., "Automatic Chemical Design Using a Data-Driven Continuous Representation of Molecules", ACS Central Science, vol. 4, no. 2, pp. 268-276, 2018. Available: 10.1021/acscentsci.7b00572.
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[5] C. Yerkes, "Lecture 22", Butane.chem.uiuc.edu, 2022. [Online]. Available: http://butane.chem.uiuc.edu:80/cyerkes/Chem204sp06/Lecture_Notes/lect21c.html.
[6] M. M. Bronstein, J. Bruna, T. Cohen, and P. Velickovič, “Geometric deep learning: Grids, groups, graphs, geodesics, and gauges”, arXiv:2104.13478, 2021.
[7] J. Vamathevan et al., "Applications of machine learning in drug discovery and development", Nature Reviews Drug Discovery, vol. 18, no. 6, pp. 463-477, 2019. Available: 10.1038/s41573-019-0024-5.
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[12] B. McMahon, "AI is Ushering In a New Scientific Revolution", The Gradient, 2022. Available: https://thegradient.pub/ai-scientific-revolution/
[13] H. Chen, O. Engkvist, Y. Wang, M. Olivecrona and T. Blaschke, "The rise of deep learning in drug discovery", Drug Discovery Today, vol. 23, no. 6, pp. 1241-1250, 2018. Available: 10.1016/j.drudis.2018.01.039.
[14] K. Roy, S. Kar and R. Das, A primer on QSAR/QSPR modeling, 1st ed. Springer, 2015, pp. 1-36.
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[17] K. Atz, F. Grisoni and G. Schneider, "Geometric deep learning on molecular representations", Nature Machine Intelligence, vol. 3, no. 12, pp. 1023-1032, 2021. Available: 10.1038/s42256-021-00418-8.
[18] E. Jannik Bjerrum, R. Threlfall. “Molecular Generation with Recurrent Neural Networks (RNNs)”. arXiv:1705.04612, 2017.
[19] Y. Rong et al., "Self-Supervised Graph Transformer on Large-Scale Molecular Data", Proceedings of the 33th International Conference on Neural Information Processing Systems (NeurIPS), 2020, pp. 12559–12571.
[20] H. Stark et al., “3-D Infomax improves GNNs for Molecular Property Prediction”, presented at the 39th International Conference on Machine Learning (ICML), 2022.
[21] T. Smidt, "Euclidean Symmetry and Equivariance in Machine Learning", Trends in Chemistry, vol. 3, no. 2, pp. 82-85, 2021. Available: 10.1016/j.trechm.2020.10.006.
[22] A. White, "Deep learning for molecules and materials", Living Journal of Computational Molecular Science, vol. 3, no. 1, 2022. Available: 10.33011/livecoms.3.1.1499.
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[24] E. van der Pol, "AMMI Seminar 1 - Geometric Deep Learning and Reinforcement Learning", African Masters of Machine Intelligence [Online], 2021.
[25] L. Nguyen, H. He and C. Pham-Huy, "Chiral Drugs: An Overview", International Journal of Biomedical Science, vol. 2, no. 2, pp. 85-100, 2006.
[26] W. H. Brooks, W. C. Guida and K. G. Daniel, "The Significance of Chirality in Drug Design and Development", Current Topics in Medicinal Chemistry, vol. 11, no. 7, pp. 760-770, 2011. Available: 10.2174/156802611795165098.
[27] V. G. Satorras, E. Hoogeboom, F. B. Fuchs, I. Posner, and M. Welling. “E(n) equivariant Normalizing Flows”, in the 34th Advances in Neural Information Processing Systems (NeurIPS) [Online], 2021. Available: https://proceedings.neurips.cc/paper/2021/hash/21b5680d80f75a616096f2e791affac6-Abstract.html
[28] E. Hoogeboom, "How to build E(n) Equivariant Normalizing Flows, for points with features?", ehoogeboom.github.io/, 2022. [Online]. Available: https://ehoogeboom.github.io/post/en_flows/.
[29] V. G. Satorras, E. Hoogeboom, and M. Welling. “E(n) equivariant graph neural networks”, in Proceedings of the 38th International Conference on Machine Learning (ICML) [Online], 2021. Available: http://proceedings.mlr.press/v139/satorras21a/satorras21a.pdf.
[30] E. Hoogeboom et al., “Equivariant Diffusion for Molecule Generation in 3-D”, in Proceedings of the 39th International Conference on Machine Learning,(ICML), 2022, pp. 8867--8887.
[31] M. Xu, L. Yu, Y. Song, C. Shi, S. Ermon and J. Tang, "GeoDiff: A Geometric Diffusion Model for Molecular Conformation Generation", presented at the 11th International Conference on Learning Representations (ICLR 2022) [Online]. Available: arXiv:2203.02923.
[32] L. Weng, "What are Diffusion Models?", lilianweng.github.io, 2022. [Online]. Available: https://lilianweng.github.io/posts/2021-07-11-diffusion-models/.
[33] W. Gao and C. Coley, "The Synthesizability of Molecules Proposed by Generative Models", Journal of Chemical Information and Modeling, vol. 60, no. 12, pp. 5714-5723, 2020. Available: 10.1021/acs.jcim.0c00174.
[34] T. Zhu et al., "Hit Identification and Optimization in Virtual Screening: Practical Recommendations Based on a Critical Literature Analysis", Journal of Medicinal Chemistry, vol. 56, no. 17, pp. 6560-6572, 2013. Available: 10.1021/jm301916b.
### Meilina Reksoprodjo
Meilina Reksoprodjo is an MSc student in Data Science in Engineering at the Eindhoven University of Technology, specializing in explainable AI & geometric deep learning for drug discovery.
|
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http://www.mediawiki.org/wiki/Extension:JsMath
|
# Extension:JsMath
MediaWiki extensions manual - list
JsMath
Release status: beta
Description Math rendering with the javascript library jsMath.
Author(s) Tommy Ekola
MediaWiki tested with 1.11.0
Translate the JsMath extension if possible
Check usage and version matrix; code metrics
JsMath is an extension that provides an additional math rendering mode using the javascript library jsMath. This extension will add an extra option "jsMath" to the math tab in the preferences form. When the user selects this rendering mode the javascript library jsMath will be included on pages and math formulas written using the [itex] tag (in wiki texts) will be output inside special tags that are recognized and processed by jsMath on the user's web browser.
The main benefits of using jsMath, instead of the normal math rendering, are primarily that
1. formulas resize when the text on a page is enlarged,
2. it is possible to get high-quality print output, and
3. it works on almost all browsers (compare this to MathML).
The main drawback is that it takes time for jsMath to process math formulas on the client, especially if a page contains a lot of math. A user might therefore only want to enable jsMath when he or she needs to do a print-out.
As an alternative: The MathJax javascript library, which is the jsMath replacement, can be used through the MathJax extension. This extension supports TeX style labeling (with automatic numbering) and referencing through \label{} and \eqref{}. (Comment placed here by the author of the MathJax extension Dirk Nuyens 22:13, 15 November 2010 (UTC))
## Installation
### Install jsMath
Detailed instructions are available from the homepage of jsMath.
### Configure jsMath
Detailed instructions are available from the homepage of jsMath.
This extension assumes that jsMath is configured through the file easy/load.js. You can edit this file to your heart's content, but below are some recommendations:
1. Turn off jsMath's special interpretation of $$, $, and as math mode delimiters. processSlashParens: 0, // process \(...$$ in text? processSlashBrackets: 0, // process \[...$ in text?
processDoubleDollars: 0, // process $$...$$ in text?
processSingleDollars: 0, // process $...$ in text?
processLaTeXenvironments: 0, // process \begin{xxx}...\end{xxx} outside math mode?
fixEscapedDollars: 0, // convert \$to$ outside of math mode?
2. Load AMSmath and some extra fonts. Notice that you also need to install the extra fonts cmbsy10, cmmib10, msam10 and msbm10 on the server, as outlined on this page.
loadFiles: ["extensions/AMSmath.js", "extensions/AMSsymbols.js",
"extensions/boldsymbol.js", "extensions/moreArrows.js"],
Create the directory $IP/extensions/JsMath and save the php code in the files JsMath.php and JsMath.i18n.php, respectively, in that directory. ### Configure the extension First of all you need to have TeX support installed (see this page). Make sure the file$IP/LocalSettings.php contains the line
$wgUseTeX = true; Then you add the following lines at the end of the file$IP/LocalSettings.php
$wgJsMathRoot = ".../jsMath"; require_once( "$IP/extensions/JsMath/JsMath.php" );
where $wgJsMathRoot is the root directory of the javascript library jsMath on the server (it should have the same value as the root variable in easy/load.js). If you want jsMath rendering to be the default for users then you should add the following line before JsMath.php is loaded $wgJsMathDefault = 1;
If you want to include any plugins to jsMath that cannot be included in easy/load.js then you should add them to the $wgJsMathPlugins array before JsMath.php is loaded. For example, to load the smallFonts.js plugin you write $wgJsMathPlugins = array( $wgJsMathRoot . "/plugins/smallFonts.js" ); ## The Code ### JsMath.php <?php /* * @author Tommy Ekola * @copyright © 2008 by Tommy Ekola ([email protected]) * @licence GNU General Public Licence 2 or later */ if (! defined( 'MEDIAWIKI' ) ) { echo( "This is an extension to the MediaWiki package and cannot be run standalone.\n" ); die( -1 ); } // Extension information$wgExtensionCredits['other'][] = array(
'name' => 'JsMath',
'description' => 'jsMath rendering of math formulas',
'version' => '0.9',
'author' => 'Tommy Ekola',
'url' => 'http://www.mediawiki.org/wiki/Extension:JsMath');
// Configuration
if(! isset( $wgJsMathRoot )) { echo( "The root directory of jsMath is not specified. Make sure \$wgJsMathRoot is set in $IP/LocalSettings.php" ); die( -1 ); } define( 'MW_MATH_JSMATH', 6 ); if($wgJsMathDefault ) {
$wgDefaultUserOptions['math'] = MW_MATH_JSMATH; } // Load jsMath on the page$wgExtensionFunctions[] = 'wfJsMathSetup';
function wfJsMathSetup() {
global $wgOut,$wgJsMimeType, $wgJsMathRoot,$wgUseTeX, $wgJsMathPlugins; if(!$wgUseTeX ) return;
wfJsMathMessages();
// Put jsMath div tags in the content part of the page
$wgOut->addInlineScript( "jsMath = {Setup: {DIV: function(id,styles) {\n" . " var div = jsMath.document.createElement('div');\n" . " div.id = 'jsMath_'+id;\n" . " for (var i in styles) {div.style[i]= styles[i]}\n" . " var el = jsMath.document.getElementById('content');\n" . " if(!el) el = jsMath.document.getElementById('globalWrapper');\n" . " if(!el) el = jsMath.document.body;\n" . " if(!el) return;\n" . " if (!el.hasChildNodes) {\n" . " el.appendChild(div);\n" . " }\n" . " else {\n" . " el.insertBefore(div,el.firstChild);\n" . " }\n" . " return div;\n" . "}}}" ); if( isset($wgJsMathPlugins )) {
foreach( $wgJsMathPlugins as$plugin ) {
$wgOut->addScript( '<script type="' .$wgJsMimeType . '" src="'
. $plugin . '"></script>' ); } }$wgOut->addScript( '<script type="' . $wgJsMimeType . '" src="' .$wgJsMathRoot . '/easy/load.js"></script>' );
}
// Internationalization
function wfJsMathMessages() {
static $messagesLoaded = false; global$wgMessageCache;
if ( !$messagesLoaded ) {$messagesLoaded = true;
require( dirname( __FILE__ ) . '/JsMath.i18n.php' );
foreach( $messages as$lang => $langMessages ) {$wgMessageCache->addMessages( $langMessages,$lang );
}
}
return true;
}
// Warn the user if javascript is turned off.
$wgHooks['SiteNoticeAfter'][] = 'wfJsMathNotice'; function wfJsMathNotice( &$sitenotice ) {
global $wgUseTeX; if(!$wgUseTeX ) return true;
sitenotice .= "\n<noscript>\n" ." <div style='color:#CC0000; text-align:center'>\n" ." <b>Warning: " ."<a href='http://www.math.union.edu/locate/jsMath'>jsMath</a>" ." requires JavaScript\n" ." to process the mathematics on this page.<br>\n" ." If your browser supports JavaScript, be sure it" ." is enabled.</b>\n" ." </div>\n" ." <hr>\n" ."</noscript>"; return true; } // Add a jsMath option to the math part of the preferences form.wgHooks['RenderPreferencesForm'][] = 'wfJsMathPreferences';
function wfJsMathPreferences( $preferences,$output) {
global $wgUseTeX; if(!$wgUseTeX ) return true;
$html =$output->getHTML();
// Create html option for jsMath
wfJsMathMessages();
$checked = ( MW_MATH_JSMATH ==$preferences->mMath );
$jsmathopt = Xml::openElement( 'div' ) . Xml::radioLabel( wfMsg( 'mw_math_jsmath' ), 'wpMath', MW_MATH_JSMATH, "mw-sp-math-" . MW_MATH_JSMATH,$checked )
. Xml::closeElement( 'div' ) . "\n";
// Insert jsMath option into the form
$i = strpos($html, "<fieldset>\n<legend>" . wfMsg('math') . '</legend>' );
if( $i !== FALSE ) {$newhtml = substr($html,0,$i)
. preg_replace( '(</fieldset>)', $jsmathopt . '</fieldset>', substr($html,$i,-1), 1 ); // Replace the old output with the new output$output->clearHTML();
$output->addHTML($newhtml );
}
return true;
}
// Strip the math tag before the parser does, and associate the
// replacement marker with the corresponding jsMath code.
$wgHooks['ParserBeforeStrip'][] = 'wfJsMathParser'; function wfJsMathParser(&$parser, &$text, &$state) {
global $wgUser,$wgContLang;
if( $parser->mOptions->getUseTeX() &&$wgUser->getOption('math') == MW_MATH_JSMATH ) {
$render = ($parser->mOutputType == OT_HTML);
$uniq_prefix =$parser->mUniqPrefix;
$commentState = new ReplacementArray;$nowikiState = new ReplacementArray;
$generalItems = array();$elements = array('math','nowiki');
$matches = array();$text = Parser::extractTagsAndParams( $elements,$text, $matches,$uniq_prefix );
foreach( $matches as$marker => $data ) { list($element, $content,$params, $tag ) =$data;
if( $render ) {$tagName = strtolower( $element ); switch($tagName ) {
case '!--':
// Comment
if( substr( $tag, -3 ) == '-->' ) {$output = $tag; } else { // Unclosed comment in input. // Close it so later stripping can remove it$output = "$tag-->"; } break; case 'nowiki':$output = $tag; break; case 'math':$attribs = Sanitizer::validateTagAttributes( $params,$tag );
$attribs = Sanitizer::mergeAttributes( array('class' => 'math'),$attribs );
$output =$wgContLang->armourMath(
Xml::tags( 'span', $attribs, "\\displaystyle " .$content ));
break;
}
}
if( $element == '!--' ) {$commentState->setPair( $marker,$output );
} elseif ( $element == 'nowiki' ) {$nowikiState->setPair( $marker,$output );
} elseif ( $element == 'math' ) {$generalItems[$marker] =$output;
} else {
throw new MWException( "Caught invalid tag $element in math strip" ); } } # Add the math items to the state$state->general->mergeArray( $generalItems ); # Unstrip nowiki and comments$text = $nowikiState->replace($text );
$text =$commentState->replace( $text ); } return true; } ### JsMath.i18n.php <?php /* * @author Tommy Ekola * @copyright © 2008 by Tommy Ekola ([email protected]) * @licence GNU General Public Licence 2 or later */$messages =
array(
'en' =>
array('mw_math_jsmath' => 'jsMath'));
|
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|
https://darcynorman.net/2007/01/01/script-for-running-cron-on-all-sites-in-a-shared-drupal-instance/
|
# Script for running Cron on all sites in a shared Drupal instance
After realizing that the sympal_scripts were silently failing to properly call cron.php on sites served from subdirectories on a shared Drupal multisite instance, I rolled up my sleeves to build a script that actually worked. What I've come up with works, but is likely not the cleanest or most efficient way of doing things. But it works. Which is better than the solution I had earlier today.
I also took the chance to get more familiar with Ruby. I could have come up with a shell script solution, but I wanted the flexibility to more easily extend the script as needed. And I wanted the chance to play with Ruby in a non-Hello-World scenario.
Here's the code:
#!/usr/local/bin/ruby
# Drupal multisite hosting auto cron.php runner
# Initial draft version by D'Arcy Norman [email protected]
# URL goes here
# Idea and some code from a handy page by (some unidentified guy) at http://whytheluckystiff.net/articles/wearingRubySlippersToWork.html
require 'net/http'
# this script assumes that $base_url has been properly set in each site's settings.php file. # further, it assumes that it is at the START of a line, with spacing as follows: #$base_url = 'http://mywonderfuldrupalserver.com/site';
# also further, it assumes there is no comment before nor after the content of that line.
# customize this variable to point to your Drupal directory
drupalsitesdir = '/usr/www/drupal' # no trailing slash
Dir[drupalsitesdir + '/sites/**/*.php'].each do |path|
File.open(path) do |f|
f.grep( /^\$base_url = / ) do |line| line = line.strip(); baseurl = line.gsub('$base_url = \'', '')
baseurl = baseurl.gsub('\';', '')
baseurl = baseurl.gsub(' // NO trailing slash!', '')
if !baseurl.empty?
cronurl = baseurl + "/cron.php"
puts cronurl
if !cronurl.empty?
url = URI.parse(cronurl)
req = Net::HTTP::Get.new(url.path)
res = Net::HTTP.start(url.host, url.port) {|http|http.request(req)}
puts res.body
end
end
end
end
end
No warranty, no guarantee. It works on my servers, and on my PowerBook.
Some caveats:
• It requires a version of Ruby more recent than what ships on MacOSX 10.3 server. Easy enough to update, following the Ruby on Rails installation instructions.
• It requires \$base_url to be set in the settings.php file for each site you want to run cron.php on automatically.
• It requires one trivial edit to the script, telling it where Drupal lives on your machine. I might take a look at parameterizing this so it could be run more flexibily.
• It requires cron (or something similar) to trigger the script on a regular basis.
|
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|
http://www.almoststochastic.com/2016/10/a-primer-on-filtering.html?showComment=1518390834702
|
2016/10/26
A primer on filtering
Say that you have a dynamical process of interest $X_1,\ldots,X_n$ and you can only observe the process with some noise, i.e., you get an observation sequence $Y_1,\ldots,Y_n$. What is the optimal way to estimate $X_n$ conditioned on the whole sequence of observations $Y_{1:n}$?
To start from the bottom, suppose you have an observation $Y$ and you think that it is related to something you want to learn about (let's call that something $X$ as the uncle of Einstein would). There are many methods in science about how to go from $Y$ to $X$, e.g. you can solve an optimization problem. A Bayesian approach would be to specify a probability distribution over $X$, denoted $p(x)$, and the likelihood $p(y|x)$ which encodes how $X$ becomes observable to us through the observation process. Then, our curiosity about $X$ can be reframed as obtaining its posterior distribution $p(x|y)$ which is possible by the celebrated Bayes' formula, \begin{align*} p(x|y) = \frac{p(y|x)p(x)}{p(y)}. \end{align*} In the filtering setup, $X$ is assumed to be a changing, dynamic process; hence denoted with $(X_n)_{n\in\bN}$. Since $X_n$ changes with time $n$, accordingly, you collect observations from this process at each time step $n$ which is denoted by $(Y_n)_{n\in\bN}$. Simply, the process could be depicted as in the following graphical model. \begin{align*} \begin{array}{ccccccc} & X_0 \to & X_1 & \to & X_2 & \to & \dots \\ && \downarrow && \downarrow \\ & & Y_1 & & Y_2 & & \dots \end{array} \end{align*} As you can see clearly, $X_n$ is a Markov process. $Y_n$ are independent given the $X$ process. What filtering aims at is to obtain the most refined (optimal) information about $X_n$ given the whole sequence of observations $Y_{1:n}=y_{1:n}$. Ideally, this would be the exact posterior distribution $p(x_n|y_{1:n})$. In order to have it, as you would guess, we have to specify two things: First, how $X_n$ evolves (the transition model), second, how $Y_n$ and $X_n$ are related (the observation model).
Generally, such models are specified in the following way, \begin{align*} X_0 &\sim p(x_0), \\ X_n | \{X_{n-1} = x_{n-1}\} &\sim p(x_n | x_{n-1}), \\ Y_n | \{X_n = x_n\} &\sim p(y_n|x_n). \end{align*} The prior on $X_0$ is usually of little practical importance, as there are strong results about what happens if you set it wrong: as long as the filter is stable, it forgets its initial condition independent of the fact that it is right or wrong. The transition model $p(x_n|x_{n-1})$ specifies how your process evolves (or rather how you think it evolves). For example, if you are working on object tracking, it is the model of the vehicle. If you work on weather and fluid dynamics, it is the (possibly stochastic) partial differential equation from fluid mechanics. If you try to land the Apollo to the moon, it would be the controlled state process (you need an additional control input in that case). To summarise, if you work on X dynamics, it is how your X evolves. The observation process $p(y_n|x_n)$ is somewhat more concrete thing to have. You may have a model of the vehicle but you can only observe it through some sensor signals. This model would encode that process: What you measure as a sensor signal and how it is related to the true position. Of course this is subject to many uncertainties, for example, in this case, you have parameters from the weather environment (e.g. connectivity) on signal's way to the satellite and/or vast amount of noise. You should encode all of it into $p(y_n|x_n)$. For the weather dynamics, you will not be able to observe ocean currents or large eddies despite you can have a pretty good idea about how they evolve (since it is physics). So both distributions $p(x_n|x_{n-1})$ and $p(y_n|x_n)$ really complete each other, you need the information from both of them in order to estimate $x_n$ at any given time $n$.
As I have written above, the goal here is to obtain $p(x_n|y_{1:n})$. One way to do is to use Bayes' theorem iteratively to achieve this task. In order to have a recursive formula for it, we need to figure out how to obtain it from $p(x_{n-1}|y_{1:n-1})$. Why? Because that's all we need. If we have a procedure for that, we'd start with $p(x_1)$ and obtain $p(x_1|y_1)$ by using Bayes' theorem as I showed in the beginning, then continue to $p(x_2|y_{1:2})$ with "the method" (which I will explain in the following) which maps densities in the following way $p(x_{n-1}|y_{1:n-1}) \mapsto p(x_n|y_{1:n})$, and so on.
There are two steps to doing this.
(i) Prediction. Given $p(x_{n-1}|y_{1:n-1})$, the usual way is to first obtain the predictive distribution of the state $p(x_n|y_{1:n-1})$ using the following relationship, \begin{align*} p(x_n|y_{1:n-1}) = \int p(x_n|x_{n-1}) p(x_{n-1}|y_{1:n-1}) \mbox{d}x_{n-1}. \end{align*} The name of this can get as fancy as it can get: the Chapman-Kolmogorov equation. At the core it uses conditional independence structure of the model and the marginalisation rule, nothing more than that. All it does is to integrate out the variable $x_{n-1}$ from the joint distribution $p(x_n,x_{n-1}|y_{1:n-1})$ which can be factorised as in the integral because of the conditional independence. Nevertheless, recall that having a formula doesn't mean that we can compute it. We have to compute the integral, and most of the cases, it is impossible.
(ii) Update. Update step is taking the observation into the account. You have the predictive distribution from above, so it's your "guess" about what could happen. Now you need to correct your prediction using the data. This means we need to obtain $p(x_n|y_{1:n})$ from $p(x_n|y_{1:n-1})$. This is possible (of course) by the use of Bayes' theorem, \begin{align*} p(x_n|y_{1:n}) = p(x_n|y_{1:n-1}) \frac{p(y_n|x_n)}{p(y_n|y_{1:n-1})}. \end{align*} Why did I call this "the use of Bayes' theorem"? If you look at what I described as Bayes' theorem above, this relationship might not be obvious. Try to look at in this way, \begin{align*} p(x_n|y_n,y_{1:n-1}) = p(x_n|y_{1:n-1}) \frac{p(y_n|x_n)}{p(y_n|y_{1:n-1})}, \end{align*} and now *ignore* all $y_{1:n-1}$ terms. Try to write it down without $y_{1:n-1}$, you will see that it is in fact the Bayes' rule, just conditioned on $y_{1:n-1}$.
You might ask the question why this has a prediction-correction structure. Why do we need to predict first and then update? I have no answer beyond that this is a possible way to do it.
Now, we have the recipe. Let's see what we can do with that.
If the model is linear and Gaussian, all these computations are analytically possible. This is what makes the Kalman filters special. Suppose we have the following probabilistic model (stochastic linear dynamical system), \begin{align*} X_0 &\sim \mathcal{N}(x_0;\mu_0,P_0), \\ X_n | \{X_{n-1} = x_{n-1}\} &\sim \mathcal{N}(x_n;A x_{n-1},Q), \\ Y_n | \{X_n = x_n\} &\sim \mathcal{N}(y_n;C x_n,R). \end{align*} Collecting $Y_{1:n} = y_{1:n}$, we are naturally after the posterior distribution $p(x_n|y_{1:n})$. If you bravely compute the integral and update rule above, you will see that they can be carried out analytically. Resulting posterior $p(x_n|y_{1:n})$ is Gaussian so it can be parameterised by its mean and covariance. So instead of updating the probability measure (which is not obvious at all), all you need to do is to update its mean and covariance recursively, as you can get the whole information using those and the functional form encoded by the Gaussian density (this is called finite-dimensional filtering, as you do it by updating the finite-dimensional sufficient statistics). If you denote the posterior with $p(x_n|y_{1:n}) = \mathcal{N}(x_n;\mu_n,P_n)$, the prediction step is given by, \begin{align*} \mu_{n|n-1} &= A \mu_{n-1}, \\ P_{n|n-1} &= A P_n A^\top + Q. \end{align*} Then the update step is the following, \begin{align*} \mu_n &= \mu_{n|n-1} + P_{n|n-1} C^\top (C P_{n|n-1} C^\top + R)^{-1} (y_n - C x_{n|n-1}), \\ P_n &= P_{n|n-1} - P_{n|n-1} C^\top (C P_{n|n-1} C^\top + R)^{-1} C P_{n|n-1}. \end{align*} Notice that, in the prediction step, we don't have $y_n$ nor any parameter from the observation model $p(y_n|x_n)$, it only includes the parameters of the transition model $p(x_n|x_{n-1})$. And the reverse is true for the update step, as it only involves the parameters of the observation model $p(y_n|x_n)$ and it does not have any parameter of the transition model $p(x_n|x_{n-1})$.
So let's conclude with a note about particle filters. What do particle filters do? It approximates the posterior probability distribution $p(x_n|y_{1:n})$ where $p(x_n|x_{n-1})$ and $p(y_n|x_n)$ are specified in general ways so, essentially, when it is not possible to perform above computations. Don't be mad at me, but most of the particle filters don't use the above recursions but rather they use something else. However, conceptually, this post should be helpful for you to understand what they are trying to do.
Unknown said...
I think you could show the sequential nature of the Bayes' theorem and from that, show the Kalman filter as a special case of it. There are other examples of sequential inference in reliability analysis with some uncommon probabilistic models.
Deniz said...
Hi. I did not understand the first part of the comment. But I'd love to see other analytically tractable nonGaussian models, if there are any.
Anonymous said...
Awesome post.
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http://umj.imath.kiev.ua/article/?lang=en&article=11283
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2019
Том 71
№ 10
# Approximation of $\bar {\psi} - integrals$−integrals of periodic functions by Fourier sums (small smoothness). Iof periodic functions by Fourier sums (small smoothness). I
Stepanets O. I.
Abstract
We investigate the rate of convergence of Fourier series on the classes $L^{\bar {\psi} } \text{N}$ in the uniform and integral metrics. The results obtained are extended to the case where the classes $L^{\bar {\psi} } \text{N}$ are the classes of convolutions of functions from $\text{N}$ with kernels with slowly decreasing coefficients. In particular, we obtain asymptotic equalities for the upper bounds of deviations of the Fourier sums on the sets $L^{\bar {\psi} } \text{N}$ which are solutions of the Kolmogorov-Nikol’skii problem. In addition, we establish an analog of the well-known Lebesgue inequality.
English version (Springer): Ukrainian Mathematical Journal 50 (1998), no. 2, pp 314–333.
Citation Example: Stepanets O. I. Approximation of $\bar {\psi} - integrals$−integrals of periodic functions by Fourier sums (small smoothness). Iof periodic functions by Fourier sums (small smoothness). I // Ukr. Mat. Zh. - 1998. - 50, № 2. - pp. 274-291.
Full text
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http://neuroplausible.com/connectionism
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Block Practical: Connectionist Models and Cognitive Processes
These are the course materials I used to teach second year undergraduate students basic programming in Python and connectionism in the Experimental Psychology Department, University of Oxford.
This is less of a blog post and more of a materials dump from an elective practical I taught about three years ago to second year undergraduate students in the Experimental Psychology Department at the University of Oxford. I thoughtlessly deleted the webpage that contained them, assuming no student after 2 years would need them. How wrong I was! I received an email the other day from a Ph.D. student at a university on the other side of the world pretty much asking where these materials had disappeared to. This made me question my assumption nobody was looking at these materials. So to save myself and others from looking for them again, here they are for everybody.
This elective practical taught second year undergraduates to program in Python at a basic level and to understand the basics of artificial neural networks. They proved highly suitable as my students had not done much/any programming before and had not really heard of neural networks (things might have changed now, hype, etc).
To clarify, I do not teach this course any more and I will not be updating or using these materials. If you want to use them for your own teaching, they are CC BY 4.0, and I would super appreciate an email or tweet if you use them.
A really basic neural network diagram, by Wikipedia user Glosser.ca
How to install Python
Windows Users
This is a little tricky:
1. Install Python: download from here
2. Install matplotlib, numpy, and scipy using pip. Specifically you need to download the following from here:
• matplotlib-1.4.3-cp27-none-win32.whl
• numpy-1.10.0b1+mkl-cp27-none-win32.whl
• scipy-0.16.0-cp27-none-win32.whl
This requires you to be in the Scripts folder of the Python27 installation. And to use the windows command prompt. For me this looks like:
C:\Python27\Scripts>pip install NAME_OF_WHEEL_FILE.whl
For all three of those you need to run a pip command like above.
1. Install PyGTK: download from here
2. To check that everything works, open network.py and see if it runs without any errors.
Mac Users
I finally managed to do this on my mac. Use Homebrew to install matplotlib, numpy, scipy, pygtk.
Linux Users
Use your favourite package manager to install matplotlib, numpy, scipy, pygtk.
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http://physicallensonthecell.org/chemical-physics/ideal-gas-basis-mass-action-and-window-free-energywork-relations
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# The Ideal Gas: The basis for "mass action" and a window into free-energy/work relations
## The Ideal Gas: The basis for "mass action" and a window into free-energy/work relations
The simplest possible multi-particle system, the ideal gas, is a surprisingly valuable tool for gaining insight into biological systems - from mass-action models to gradient-driven transporters. The word "ideal" really means non-interacting, so in an ideal gas all molecules behave as if no others are present. The gas molecules only feel a force from the walls of their container, which merely redirects their momenta like billiard balls. Not surprisingly, it is possible to do exact calculations fairly simply under such extreme assumptions. What's amazing is how relevant those calculations turn out to be, particularly for understanding the basic mechanisms of biological machines and chemical-reaction systems.
Although ideal particles do not react or bind, their statistical/thermodynamic behavior in the various states (e.g., bound or not, reacted or not) can be used to build powerful models - e.g., for transporters.
### Mass-action kinetics are ideal-gas kinetics
The key assumption behind mass-action models is that events (binding, reactions, ...) occur precisely in proportion to the concentration(s) of the participating molecules. This certainly cannot be true for all concentrations, because all molecules interact with one another at close enough distances - i.e., at high enough concentrations. In reality, beyond a certain concentration, simple crowding effects due to steric/excluded-volume effects mean that each molecule can have only a maximum number of neighbors.
But in the ideal gas - and in mass-action kinetics - no such crowding effects occur. All molecules are treated as point particles. They do not interact with one another, although virtual/effective interactions occur in a mass-action picture. (We can say these interactions are "virtual" because the only effect is to change the number of particles - no true forces or interactions occur.)
### Pressure and work in an ideal gas
Ideal gases can perform work directly using pressure. The molecules of an ideal gas exert a pressure on the walls of the container holding them due to collisions, as sketched above. The amount of this pressure depends on the number of molecules colliding with each unit area of the wall per second, as well as the speed of these collisions. These quantities can be calculated based on the mass $m$ of each molecule, the total number of molecules, $N$, the total volume of the container $V$ and the temperature, $T$. In turn, $T$ determines the average speed via the relation $(3/2) \, N \, k_B T = \avg{(1/2) \, m \, v^2}$. See the book by Zuckerman for more details.
All these facts can be combined - consult a physics book - to yield the ideal gas law relating pressure $P$ to the other quantities:
(1)
We can calculate the work done by an ideal gas to change the size of its container by pushing one wall a distance $d$ as shown above. We use the basic rule of physics that work is force ($f$) multiplied by distance and the definition of pressure as force per unit area. If we denote the area of the wall by $A$, we have
(2)
If $d$ is small enough so that the pressure is nearly constant, we can calculate $P$ using (1) at either the beginning or end of the expansion. More generally, for a volume change of arbitrary size (from $V_i$ to $V_f$) in an ideal gas, we need to integrate:
(3)
which assumes the expansion is performed slowly enough so that (1) applies throughout the process.
### Free energy and work in an ideal gas
The free energy of the ideal gas can be calculated exactly in the limit of large $N$ (see below). We will see that it does, in fact, correlate precisely with the expression for work just derived. The free energy depends on temperature, volume, and the number of molecules; for large $N$, it is given by
(4)
where $\lambda$ is a constant for fixed temperature. For reference, it is given by $\lambda = h / \sqrt{2 \pi m k_B T}$ with $h$ being Planck's constant and $m$ the mass of an atom. See the book by Zuckerman for full details.
Does the free energy tell us anything about work? If we examine the free energy change occuring during the same expansion as above, from $V_i$ to $V_f$ at constant $T$, we get
(5)
Comparing to (3), this is exactly the negative of the work done! In other words, the free energy of the ideal gas decreases by exactly the amount of work done (when the expansion is performed slowly). More generally, the work can be no greater than the free energy decrease. The ideal gas has allowed us to demonstrate this principle concretely.
### The ideal gas free energy from statistical mechanics
The free energy is derived from the "partition function" $Z$, which is simply a sum/integral over Boltzmann factors for all possible configurations/states of a system. Summing over all possibilities is why the free energy encompasses the full thermodynamic behavior of a system.
The mathematical relation is
(6)
where $Z$ is defined by
(7)
where $\lambda(T) \propto 1/\sqrt(T)$ is the thermal de Broglie wavelength (which is not important for the phenomena of interest here), $\rall$ is the set of $(x,y,z)$ coordinates for all molecules and $U$ is the potential energy function. The factor $1/N!$ accounts for interchangeability of identical molecules, and the integral is over all volume allowed to each molecule. For more information, see the book by Zuckerman, or any statistical mechanics book.
The partition function can be evaluated exactly for the case of the ideal gas because the non-interaction assumption can be formulated as $U(\rall) = 0$ for all configurations - in other words, the locations of the molecules do not change the energy or lead to forces. This makes the Boltzmann factor exactly $1$ for all $\rall$, and so each molecule's inegration over the full volume yields a factor of $V$, making the final result
(8)
Although (8) assumes there are no degrees of freedom internal to the molecule - which might be more reasonable in some cases (ions) than others (flexible molecules) - the expression is sufficient for most of the biophysical explorations undertaken here.
The combination of (6) and (8) can be used to derive (4) in conjunction with Stirling's approximation for large $N$. See a statistical mechanics book for details.
### References
• Any basic physics textbook.
• D.M. Zuckerman, "Statistical Physics of Biomolecules: An Introduction," (CRC Press, 2010), Chapters 5, 7.
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https://kanglu.me/
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# Kang Lu
### Personal Information
I am a fifth-year math Ph.D. student at Indiana University–Purdue University Indianapolis (IUPUI), advised by Evgeny Mukhin.
• Email: lukang[at]iu[dot]edu
• Address: 402 N. Blackford, LD 270, Indianapolis IN 46202
• Name in Chinese: 陆康
• My CV may be found here.
### Research Interests
Generally speaking, I am interested in Representation Theory and Quantum Algebras.
More specifically, my current research interests are: Bethe ansatz method, Representation Theory of Quantum Groups, Lie Algebras and Superalgebras, and Integrable System.
### Preprints
1. Fine gradings of complex simple Lie algebras and Finite Root Systems
(with Gang Han, Jun Yu), 29 Oct. 2014. (arXiv:1410.7945) not for publication
### Publications
1. Solutions of $\mathfrak{gl}_{m|n}$ XXX Bethe ansatz equation and rational difference operators
(with Chenliang Huang, E. Mukhin), J. Phys A: Math. and Theor., (arXiv:1811.11225)
2. On the Gaudin model of type $G_2$
(with E. Mukhin), Commun. Contemp. Math. 21 (2019), no. 3, 1850012, 31 pages, (arXiv:1711.02511)
3. Multiplicity free gradings on semisimple Lie and Jordan algebras and skew root systems
(with Gang Han, Yucheng Liu), Algebra Colloq. 26 (2019), no. 1, 123-138, (arXiv:1611.03943)
4. Lower bounds for numbers of real self-dual spaces in problems of Schubert calculus
SIGMA 14 (2018), 046, 15 pages, (arXiv:1710.06534)
5. Self-dual Grassmannian, Wronski map, and representations of $\mathfrak{gl}_N$, $\mathfrak{sp}_{2r}$, $\mathfrak{so}_{2r+1}$
(with E. Mukhin, A. Varchenko), Pure Appl. Math. Q. 13 (2017), no.2, 291 – 335 , a special issue of in honor of Yuri Manin’s 80-th birthday, (arXiv:1705.02048)
6. On the Gaudin model associated to Lie algebras of classical types
(with E. Mukhin, A. Varchenko), J. Math. Phys. 57 (2016), 101703, 23 pages (arXiv:1512.08524)
My Erdös Number: 4.
Paul Erdős–>Shizuo Kakutani–>Karl Endel Petersen–>A. N. Varchenko–>Kang Lu
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https://byjus.com/question-answer/half-the-girls-and-one-third-of-the-boys-of-a-college-reside-in-the/
|
Question
Half the girls and one-third of the boys of a college reside in the hostel. What fractional part of the student body is hostel dwellers if the total number of girls in the college is 100 and is 114 of the total strength?
A
58
B
78
C
38
D
18
Solution
The correct option is C $$\dfrac{3}{8}$$It is given that the total number of students in college is $$400$$ and the number of girls is $$100$$. Therefore, the number of boys in the college is$$400-100=300$$.Also it is given that half the girls and one-third of the boys of college reside in the hostel, therefore, the number of hostel dwellers are as follows:$$\left( \dfrac { 1 }{ 2 } \times 100 \right) +\left( \dfrac { 1 }{ 3 } \times 300 \right) =50+100=150$$Now, we divide the number of hostel dwellers by the total number of students to find the required fraction:$$\dfrac { 150 }{ 400 } =\dfrac { 3 }{ 8 }$$ Hence, $$\dfrac { 3 }{ 8 }$$ of the student body is hostel dwellers.Mathematics
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https://www.gradesaver.com/textbooks/math/algebra/college-algebra-11th-edition/chapter-4-section-4-4-evaluating-logarithms-and-the-change-of-base-theorem-4-4-exercises-page-435/48
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## College Algebra (11th Edition)
Published by Pearson
# Chapter 4 - Section 4.4 - Evaluating Logarithms and the Change-of-Base Theorem - 4.4 Exercises - Page 435: 48
#### Answer
$-4$
#### Work Step by Step
$\bf{\text{Solution Outline:}}$ Use the properties of logarithms to evaluate the given expression, $\ln\left( \dfrac{1}{e^4} \right) .$ $\bf{\text{Solution Details:}}$ Using the Quotient Rule of Logarithms, which is given by $\log_b \dfrac{x}{y}=\log_bx-\log_by,$ the expression above is equivalent \begin{array}{l}\require{cancel} \ln1-\ln e^4 .\end{array} Using the Power Rule of Logarithms, which is given by $\log_b x^y=y\log_bx,$ the expression above is equivalent to \begin{array}{l}\require{cancel} \ln1-4\ln e .\end{array} Since $\ln e=1$ and $\ln1=0,$ the expression above is equivalent to \begin{array}{l}\require{cancel} 0-4(1) \\\\= -4 .\end{array}
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http://www.jstor.org/stable/2958783
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## Access
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Access your personal account or get JSTOR access through your library or other institution:
# Consistent Nonparametric Regression
Charles J. Stone
The Annals of Statistics
Vol. 5, No. 4 (Jul., 1977), pp. 595-620
Stable URL: http://www.jstor.org/stable/2958783
Page Count: 26
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## Abstract
Let (X, Y) be a pair of random variables such that X is Rd-valued and Y is Rd'-valued. Given a random sample (X1, Y1), ⋯, (Xn, Yn) from the distribution of (X, Y), the conditional distribution $P^Y(\bullet \mid X)$ of Y given X can be estimated nonparametrically by P̂n Y(A ∣ X) = ∑n 1 Wni(X)IA(Yi), where the weight function Wn is of the form Wni(X) = Wni(X, X1, ⋯, Xn), 1 ≤ i ≤ n. The weight function Wn is called a probability weight function if it is nonnegative and ∑n 1 Wni(X) = 1. Associated with $\hat{P}_n^Y(\bullet \mid X)$ in a natural way are nonparametric estimators of conditional expectations, variances, covariances, standard deviations, correlations and quantiles and nonparametric approximate Bayes rules in prediction and multiple classification problems. Consistency of a sequence {Wn} of weight functions is defined and sufficient conditions for consistency are obtained. When applied to sequences of probability weight functions, these conditions are both necessary and sufficient. Consistent sequences of probability weight functions defined in terms of nearest neighbors are constructed. The results are applied to verify the consistency of the estimators of the various quantities discussed above and the consistency in Bayes risk of the approximate Bayes rules.
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https://worldwidescience.org/topicpages/s/soil+nitrogen+transformations.html
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#### Sample records for soil nitrogen transformations
1. Transformation of fertilizer nitrogen in soil
International Nuclear Information System (INIS)
Soechting, H.
1980-01-01
Pot experiments are described in which the transformations between nitrogen added as fertilizer urea, plant-assimilated nitrogen, and different chemical fractions of soil or added straw nitrogen were studied with 15 N as a tracer. The data indicated that: (a) The transformation of added fertilizer nitrogen to immobilized amide nitrogen is decreased with added decomposable organic carbon. The transformation to immobilized α-amino N is increased, on the other hand, by the addition of decomposable organic carbon. (b) The freshly immobilized amide nitrogen is more readily remineralized than the α-amino form. The immobilization of added nitrogen continues in the presence of growing plants. (c) Mineralization of nitrogen added as 15 N-labelled straw is also increased with increasing fertilizer-nitrogen additions. (author)
2. Nitrogen Transformations in Broiler Litter-Amended Soils
Directory of Open Access Journals (Sweden)
Kokoasse Kpomblekou-A
2012-01-01
Full Text Available Nitrogen mineralization rates in ten surface soils amended with (200 μg N g−1 soil or without broiler litter were investigated. The soil-broiler litter mixture was incubated at 25±1∘C for 28 weeks. A nonlinear regression approach for N mineralization was used to estimate the readily mineralizable organic N pools (N0 and the first-order rate constant (k. The cumulative N mineralized in the nonamended soils did not exceed 80 mg N kg−1 soil. However, in Decatur soil amended with broiler litter 2, it exceeded 320 mg N kg−1 soil. The greatest calculated N0 of the native soils was observed in Sucarnoochee soil alone (123 mg NO3− kg−1 soil which when amended with broiler litter 1 reached 596 mg N kg−1 soil. The added broiler litter mineralized initially at a fast rate (k1 followed by a slow rate (k2 of the most resistant fraction. Half-life of organic N remaining in the soils alone varied from 33 to 75 weeks and from 43 to 15 weeks in the amended soils. When N0 was regressed against soil organic N (=0.782∗∗ and C (=0.884∗∗∗, positive linear relationships were obtained. The N0 pools increased with sand but decreased with silt and clay contents.
3. SOIL NITROGEN TRANSFORMATIONS AND ROLE OF LIGHT FRACTION ORGANIC MATTER IN FOREST SOILS
Science.gov (United States)
Depletion of soil organic matter through cultivation may alter substrate availability for microbes, altering the dynamic balance between nitrogen (N) immobilization and mineralization. Soil light fraction (LF) organic matter is an active pool that decreases upon cultivation, and...
4. Transformation of nitrogenous fertilizers of surface and deep application in calcareous soil
International Nuclear Information System (INIS)
Zuo Dongfeng
1990-01-01
The transformations of 15 N labelled fertilizer N in calcareous soil were studied under greennhouse conditions. The experimental results indicate that the ratio of fixed ammonium is closely related to the methods of fertilizer application to the soil. When fertilizer N applied as deep dressing the fixation of nitrogen by clay minerals and microorganisms may markedly reduce the losses of nitrogen, but the amount of nitrogen fixed by the clay minerals and that by microorganisms showed negative correlation (r = -0.9185 ** ). The more the amount of fixed nitrogen by clay minerals, the less by microorganisms. No obvious interrelation between the residual utilization of urea, ammonium bicarbonate, ammonium sulfate and the ammount of nitrogen fixed by organisms can be observed, but the residual utilization of these fertilizers by the succeeding crop has been related to the total amount of mineral nitrogen
5. Nitrogen transformations and greenhouse gas emissions from a riparian wetland soil: An undisturbed soil column study
Energy Technology Data Exchange (ETDEWEB)
Munoz-Leoz, Borja [Department of Chemical and Environmental Engineering, University of the Basque Country, UPV/EHU, E-48013 Bilbao (Spain); Antigueedad, Inaki [Department of Geodynamic, University of the Basque Country, UPV/EHU, E-48940 Leioa (Spain); Garbisu, Carlos [Department of Ecosystems, NEIKER-Tecnalia, E-48160 Derio (Spain); Ruiz-Romera, Estilita, E-mail: [email protected] [Department of Chemical and Environmental Engineering, University of the Basque Country, UPV/EHU, E-48013 Bilbao (Spain)
2011-01-15
Riparian wetlands bordering intensively managed agricultural fields can act as biological filters that retain and transform agrochemicals such as nitrate and pesticides. Nitrate removal in wetlands has usually been attributed to denitrification processes which in turn imply the production of greenhouse gases (CO{sub 2} and N{sub 2}O). Denitrification processes were studied in the Salburua wetland (northern Spain) by using undisturbed soil columns which were subsequently divided into three sections corresponding to A-, Bg- and B2g-soil horizons. Soil horizons were subjected to leaching with a 200 mg NO{sub 3}{sup -} L{sup -1} solution (rate: 90 mL day{sup -1}) for 125 days at two different temperatures (10 and 20 {sup o}C), using a new experimental design for leaching assays which enabled not only to evaluate leachate composition but also to measure gas emissions during the leaching process. Column leachate samples were analyzed for NO{sub 3}{sup -} concentration, NH{sub 4}{sup +} concentration, and dissolved organic carbon. Emissions of greenhouse gases (CO{sub 2} and N{sub 2}O) were determined in the undisturbed soil columns. The A horizon at 20 {sup o}C showed the highest rates of NO{sub 3}{sup -} removal (1.56 mg N-NO{sub 3}{sup -} kg{sup -1} DW soil day{sup -1}) and CO{sub 2} and N{sub 2}O production (5.89 mg CO{sub 2} kg{sup -1} DW soil day{sup -1} and 55.71 {mu}g N-N{sub 2}O kg{sup -1} DW soil day{sup -1}). For the Salburua wetland riparian soil, we estimated a potential nitrate removal capacity of 1012 kg N-NO{sub 3}{sup -} ha{sup -1} year{sup -1}, and potential greenhouse gas emissions of 5620 kg CO{sub 2} ha{sup -1} year{sup -1} and 240 kg N-N{sub 2}O ha{sup -1} year{sup -1}. - Research Highlights: {yields}A new experimental design is proposed for leaching assays to simulate nitrogen transformations in riparian wetland soil. {yields}Denitrification is the main process responsible for nitrate removal in the riparian zone of Salburua wetland. {yields
6. Effect of Nitrogen Fertilizer on Combined Forms and Transformation of Fluorine in Tea Garden Soil
Directory of Open Access Journals (Sweden)
ZHANG Yong-li
2015-10-01
Full Text Available In order to investigate the effect of nitrogen fertilizer on combined forms and transformation of fluorine in tea garden soil, soil pot experiment was carried out. The research object was red-yellow soil in Shizipu tea plantation in the south of Anhui Province. Five treatments were N0P0K0 (CK, N0P1K1 (N0, N1P1K1 (N1, N2P1K1 (N2, N3P1K1 (N3. Water-soluble fluorine content, exchangeable fluorine content, Fe/Mn oxide-bound fluorine content, organic matter-bound fluorine content, ammonium nitrogen content and soil pH value in 0~15 cm soil layer were analyzed in 10, 20, 30, 50, 70, 90 days after fertilization. The results showed that compared with CK, in the short term (10 or 20 days after applying NPK, the content of water-soluble fluorine in 0~15 cm soil layer was decreased and the content of exchangeable fluorine, Fe/Mn oxide-bound fluorine and organic matter-bound fluorine were increased. After 20 days, the content of soil water-soluble fluorine was increased and the content of soil exchangeable fluorine, Fe/Mn oxide-bound fluorine and organic matter-bound fluorine were reduced. The effect on water-soluble fluorine and exchangeable fluorine increased with time and the application rate of nitrogen. The content of water-soluble fluorine in tea garden soil had a moderately positive correlation with the application rate of nitrogen while the content of exchangeable fluorine had a moderately or highly negative correlation with the application rate of nitrogen. The content of water-soluble fluorine had a quite highly negative correlation with the soil pH (P<0.01, but the content of exchangeable fluorine had a moderately or highly negative correlation with the soil pH (P<0.01. Therefore, nitrogen fertilizer changed the soil pH during its form transformation and thus affected the transformation and the availability of fluorine in soil.
7. Effects of land use change on soil gross nitrogen transformation rates in subtropical acid soils of Southwest China.
Science.gov (United States)
Xu, Yongbo; Xu, Zhihong
2015-07-01
Land use change affects soil gross nitrogen (N) transformations, but such information is particularly lacking under subtropical conditions. A study was carried out to investigate the potential gross N transformation rates in forest and agricultural (converted from the forest) soils in subtropical China. The simultaneously occurring gross N transformations in soil were quantified by a (15)N tracing study under aerobic conditions. The results showed that change of land use types substantially altered most gross N transformation rates. The gross ammonification and nitrification rates were significantly higher in the agricultural soils than in the forest soils, while the reverse was true for the gross N immobilization rates. The higher total carbon (C) concentrations and C / N ratio in the forest soils relative to the agricultural soils were related to the greater gross N immobilization rates in the forest soils. The lower gross ammonification combined with negligible gross nitrification rates, but much higher gross N immobilization rates in the forest soils than in the agricultural soils suggest that this may be a mechanism to effectively conserve available mineral N in the forest soils through increasing microbial biomass N, the relatively labile organic N. The greater gross nitrification rates and lower gross N immobilization rates in the agricultural soils suggest that conversion of forests to agricultural soils may exert more negative effects on the environment by N loss through NO3 (-) leaching or denitrification (when conditions for denitrification exist).
8. Soil gross nitrogen transformations in responses to land use conversion in a subtropical karst region.
Science.gov (United States)
Li, Dejun; Liu, Jing; Chen, Hao; Zheng, Liang; Wang, Kelin
2018-04-15
Gross nitrogen (N) transformations can provide important information for assessing indigenous soil N supply capacity and soil nitrate leaching potential. The current study aimed to assess the variation of gross N transformations in response to conversion of maize-soybean fields to sugarcane, mulberry, and forage grass fields in a subtropical karst region of southwest China. Mature forests were included for comparison. Gross rates of N mineralization (GNM) were highest in the forests, intermediate in the maize-soybean and forage grass fields, and lowest in the sugarcane and mulberry fields, suggesting capacity of indigenous soil N supply derived from organic N mineralization was lowered after conversion to sugarcane and mulberry fields. The relative high indigenous soil N supply capacity in the maize-soybean fields was obtained at the cost of soil organic N depletion. Gross nitrification (GN) rates were highest in the forests, intermediate in the forage grass fields and lowest in the other three agricultural land use types. The nitrate retention capacity (24.1 ± 2.0% on average) was similar among the five land use types, implying that nitrate leaching potential was not changed after land use conversion. Microbial biomass N exerted significant direct effects on the rates of N mineralization, nitrification, ammonium immobilization and nitrate immobilization. Soil organic carbon, total N and exchangeable magnesium had significant indirect effects on these N transformation rates. Our findings suggest that forage grass cultivation instead of other agricultural land uses should be recommended from the perspective of increasing indigenous soil N supply while not depleting soil organic N pool. Copyright © 2018 Elsevier Ltd. All rights reserved.
9. Nitrogen utilization and transformation in red soil fertilized with urea and ryegrass
International Nuclear Information System (INIS)
Wu Gang; Zhang Qinzheng; Ye Qingfu; Zhu Zhujun; Xi Haifu; He Zhenli
1998-01-01
The influence of fertilization with urea and ryegrass on nitrogen utilization and transformation in red soil has been studied by using 15 N tracer method. When urea and ryegrass were applied alone or in combination, the percentage of N uptaken by ryegrass for labelled urea was 3 and 1.7 times that from labelled ryegrass for the application rate of 200 mgN·kg -1 and 100 mgN·kg -1 , respectively; combining application of ryegrass and urea reduced uptake of urea N and increased uptake of ryegrass N by ryegrass plant, but the percentage of N residue in soil increased for urea and decreased for ryegrass; when urea and ryegrass were applied alone, the percentage of N residue in soil from labelled ryegrass was more than 69% while that from labelled urea was less than 25%, and much more ryegrass N was incorporated into humus than urea N
10. Nitrogen-15 natural abundance of different soil N pools as a tool for assessing N transformation processes in alpine soils
Science.gov (United States)
Makarov, Mikhail; Malysheva, Tatiana; Tiunov, Alexei; Kadulin, Maxim; Maslov, Mikhail
2017-04-01
Nitrogen availability, net N mineralization, nitrification and 15N natural abundance of total soil N and small soil N pools (N-NH4+, N-NO3-, DON and microbial biomass N) were studied in a toposequence of alpine ecosystems in the Northern Caucasus. The toposequence was represented by (1) low productive alpine lichen heath (ALH) of the wind-exposed ridge and upper slope; (2) more productive Festuca varia grassland (FG) of the middle slope; (3) most productive Geranium gymnocaulon/Hedysarum caucasicum meadow (GHM) of the lower slope and (4) low productive snow bed community (SBC) of the slope bottom. Nitrogen transformation in the alpine soils produces distinct N pools with different 15N enrichment: DON/microbial biomass N > total N > N-NH4+ > N-NO3-. Grassland and meadow soils of the middle part of the toposequence are characterized by higher nitrogen transformation activities and higher δ15 values of total N and N-NH4+. Field incubation of alpine soils increased δ15N of N-NH4+ from -2.6 - +2.0‰ to +6.1 - +15.7‰. The N-NO3-produced in the incubation experiment had extremely low (negative) δ15N values (up to -14‰). We found a positive correlation between δ15N of different soil N pools (total N, N-NH4+ and N-NO3-) and net N mineralization and nitrification. Nitrification controls the formation of 15N enriched N-NH4+ pool while N mineralization probably had an important role in regulation of 15N enrichment of DON pool in alpine soils. Overall, our results support the hypothesis that 15N is more enriched in N-rich and more depleted in N-poor ecosystems. We conclude that δ15N values of different soil N pools could be a good indicator of microbial N transformation in alpine soils of the Northern Caucasus. Acknowledgement: This study was supported by Russian Science Foundation (16-14-10208).
11. Temporal and spatial variation of nitrogen transformations in a coniferous forest soils.
NARCIS (Netherlands)
Laverman, A.M.; Zoomer, H.R.; van Verseveld, H.W.; Verhoef, H.A.
2000-01-01
Forest soils show a great degree of temporal and spatial variation of nitrogen mineralization. The aim of the present study was to explain temporal variation in nitrate leaching from a nitrogen-saturated coniferous forest soil by potential nitrification, mineralization rates and nitrate uptake by
12. Temporal and spatial variation of nitrogen transformations in a coniferous soil.
NARCIS (Netherlands)
Laverman, A.M.; Zoomer, H.R.; van Verseveld, H.W.; Verhoef, H.A.
2000-01-01
Forest soils show a great degree of temporal and spatial variation of nitrogen mineralization. The aim of the present study was to explain temporal variation in nitrate leaching from a nitrogen-saturated coniferous forest soil by potential nitrification, mineralization rates and nitrate uptake by
13. [Effects of snow pack on soil nitrogen transformation enzyme activities in a subalpine Abies faxioniana forest of western Sichuan, China].
Science.gov (United States)
Xiong, Li; Xu, Zhen-Feng; Wu, Fu-Zhong; Yang, Wan-Qin; Yin, Rui; Li, Zhi-Ping; Gou, Xiao-Lin; Tang, Shi-Shan
2014-05-01
This study characterized the dynamics of the activities of urease, nitrate reductase and nitrite reductase in both soil organic layer and mineral soil layer under three depths of snow pack (deep snowpack, moderate snowpack and shallow snowpack) over the three critical periods (snow formed period, snow stable period, and snow melt period) in the subalpine Abies faxoniana forest of western Sichuan in the winter of 2012 and 2013. Throughout the winter, soil temperature under deep snowpack increased by 46.2% and 26.2%, respectively in comparison with moderate snowpack and shallow snowpack. In general, the three nitrogen-related soil enzyme activities under shallow snowpack were 0.8 to 3.9 times of those under deep snowpack during the winter. In the beginning and thawing periods of seasonal snow pack, shallow snowpack significantly increased the activities of urease, nitrate and nitrite reductase enzyme in both soil organic layer and mineral soil layer. Although the activities of the studied enzymes in soil organic layer and mineral soil layer were observed to be higher than those under deep- and moderate snowpacks in deep winter, no significant difference was found under the three snow packs. Meanwhile, the effects of snowpack on the activities of the measured enzymes were related with season, soil layer and enzyme type. Significant variations of the activities of nitrogen-related enzymes were found in three critical periods over the winter, and the three measured soil enzymes were significantly higher in organic layer than in mineral layer. In addition, the activities of the three measured soil enzymes were closely related with temperature and moisture in soils. In conclusion, the decrease of snow pack induced by winter warming might increase the activities of soil enzymes related with nitrogen transformation and further stimulate the process of wintertime nitrogen transformation in soils of the subalpine forest.
14. The effect of urea fertiliser formulations on gross nitrogen transformations in a permanent grassland soil.
Science.gov (United States)
Harty, Mary; Mueller, Christoph; Laughlin, Ronnie; Watson, Catherine; Richards, Karl; Lanigan, Gary; Forrestal, Patrick; McGeough, Karen
2015-04-01
Introduction By 2050, the current food production rate will need to increase by 70 % in order to meet the needs of the projected world population (FAO, 2014). Under the climate change response bill, Ireland has a target to reduce GHG emissions by 20% by 2020. Agriculture was responsible for almost one third of Ireland's overall Greenhouse Gas (GHG) emissions in 2012, with 39% of these emissions arising from chemical/organic fertilisers in the form of nitrous oxide (N2O). N2O losses represent environmental damage through ozone depletion and global warming as well as acidification, eutrophication, surface and groundwater contamination and it also represents financial loss to the farmer (Cameron 2013). The contradictory aims of increasing food production while reducing GHG emissions will require an adjustment to the current system of agricultural production. As part of a larger study evaluating the switching of nitrogen (N) fertiliser formulation to minimise N2O emissions, (from calcium ammonium nitrate (CAN) to urea based formulations), this experiment examined the effect of urea based fertiliser formulations on gross N transformations in a permanent pasture soil at Hillsborough, Co. Down, Northern Ireland. Study Design/Methodology A laboratory incubation study was undertaken, to examine the effect of urea in various combinations with two types of inhibitors on soil N dynamics and N2O and N2 emissions. The inhibitors examined were the urease inhibitor N-(butyl) thiophosphoric triamide (nBTPT) and the nitrification inhibitor dicyandiamide (DCD). The fertiliser products were labelled with 15N and the soil was incubated at 15 ° C at a water filled pore space of 65%. Soil mineral N (urea, NH4+, NO2- and NO3-) concentrations, gaseous losses (N2O and N2) and the 15N enrichments of NH4+, NO2-, NO3-, N2O and N2were analysed on 8 separate occasions over 25 days. An adapted numerical 15N tracing model (Müller et al., 2007) was used to quantify the effect of the inhibitors on
15. INFLUENCE OF TECHNOGENIC LANDSCAPES RECULTIVATION ON FUNCTIONING OF SOIL MICROORGANISMS COMMUNITIES WHICH TAKE PART IN TRANSFORMATION OF NITROGEN COMPOUNDS
Directory of Open Access Journals (Sweden)
O. V. Syshchykova
2014-04-01
Full Text Available It is established that mining recultivation of tailings dams slimes promotes restoration of numerical structure of soil microorganisms community which take part in processes of nitrogen compounds transformation. The certificate of that is number restoration of the organotrophic bacteria of a nitrogen cycle to 0.3 million CFU/g of soil and increase by 2-3 times of streptomycetes quantity in blankets. The received results of quantitative structure of the microorganisms which are taking part in processes of nitrogen mineral compounds transformation in the chernozem usual allow to claim that in blankets the number of microorganisms makes 3.89 and 2.33 million CFU/g soil. It should be noted that the best conditions for microflora development are formed on slime with drawing 50 cm of loess-like loam and 30 cm of a fertile layer. The microorganism quantity on the specified monitoring area increases by 3-4 times in the soil of a fertile layer and by 1.3-1.6 times in loess-like loam in comparison with slime without recultivation. Increase of microbiological processes intensity, extremely important, considering strengthening of ecosystems self-regulation functions. It is established high level of microbiological transformation of organic substance, the indicator is made 7.3-11.1 in the edatopes of the recultivated slimes. Increasing indicators of microbiological transformation and mineralization of organic compounds in the technozems confirm restoration of a slimes biogenity at carrying out of recultivation that promotes an intensification of mineralization processes and assimilation by plants nitrogen compounds in the soil. Keywords: microorganisms, nitrogen compounds, technozems, mining recultivation.
16. INFLUENCE OF TECHNOGENIC LANDSCAPES RECULTIVATION ON FUNCTIONING OF SOIL MICROORGANISMS COMMUNITIES WHICH TAKE PART IN TRANSFORMATION OF NITROGEN COMPOUNDS
Directory of Open Access Journals (Sweden)
Syshchykova Oksana Vitalyevna
2014-04-01
Full Text Available It is established that mining recultivation of tailings dams slimes promotes restoration of numerical structure of soil microorganisms community which take part in processes of nitrogen compounds transformation. The certificate of that is number restoration of the organotrophic bacteria of a nitrogen cycle to 0.3 million CFU/g of soil and increase by 2-3 times of streptomycetes quantity in blankets. The received results of quantitative structure of the microorganisms which are taking part in processes of nitrogen mineral compounds transformation in the chernozem usual allow to claim that in blankets the number of microorganisms makes 3.89 and 2.33 million CFU/g soil. It should be noted that the best conditions for microflora development are formed on slime with drawing 50 cm of loess-like loam and 30 cm of a fertile layer. The microorganism quantity on the specified monitoring area increases by 3-4 times in the soil of a fertile layer and by 1.3-1.6 times in loess-like loam in comparison with slime without recultivation. Increase of microbiological processes intensity, extremely important, considering strengthening of ecosystems self-regulation functions. It is established high level of microbiological transformation of organic substance, the indicator is made 7.3-11.1 in the edatopes of the recultivated slimes. Increasing indicators of microbiological transformation and mineralization of organic compounds in the technozems confirm restoration of a slimes biogenity at carrying out of recultivation that promotes an intensification of mineralization processes and assimilation by plants nitrogen compounds in the soil.
17. Urbanization effects on soil nitrogen transformations and microbial biomass in the subtropics
Science.gov (United States)
Heather A. Enloe; B. Graeme Lockaby; Wayne C. Zipperer; Greg L. Somers
2015-01-01
As urbanization can involve multiple alterations to the soil environment, it is uncertain how urbanization effects soil nitrogen cycling. We established 22â0.04 ha plots in six different land cover typesârural slash pine (Pinus elliottii) plantations (n=3), rural natural pine forests (n=3), rural natural oak forests (n=4), urban pine forests (n=3), urban oak forests (n...
18. Ureic nitrogen transformation in multi-layer soil columns treated with urease and nitrification inhibitors.
Science.gov (United States)
Giovannini, Camilla; Garcia-Mina, Josè M; Ciavatta, Claudio; Marzadori, Claudio
2009-06-10
The use of N-(n-butyl)thiophosphoric triamide (NBPT), as a urease inhibitor, is one of the most successful strategies utilized to increase the efficiency of urea-based fertilization. To date, NBPT has been added to the soil incorporated in fertilizers containing either urea or the inhibitor at a fixed percentage on the urea weight. The possibility of using NBPT physically separated from urea-based fertilizers could make its use more flexible. In particular, a granulated product containing NBPT could be utilized in soils treated with different urea-based fertilizers including livestock urine, the amount depending on soil characteristics and/or the urea source (e.g., mineral fertilizer, organo-mineral fertilizer, or animal slurry). In this study, a multilayer soil column device was used to investigate the influence of an experimental granular product (RV) containing NBPT and a garlic extract, combining the ability to protect NBPT by oxidation and nitrification inhibition activity, on (a) spatial variability of soil urease and nitrification activities and (b) timing of urea hydrolysis and mineral-N form accumulation (NO(2)(-), NO(3)(-), NH(4)(+)) in soil treated with urea. The results clearly demonstrated that RV can, effectively, inhibit the soil urease activity along the soil column profile up to 8-10 cm soil layer depth and that the inhibition power of RV was dependent on time and soil depth. However, nitrification activity is not significantly influenced by RV addition. In addition, the soil N transformations were clearly affected by RV; in fact, RV retarded urea hydrolysis and reduced the accumulation of NH(4)(+)-N and NO(2)(-)-N ions along the soil profile. The RV product was demonstrated to be an innovative additive able to modify some key ureic N trasformation processes correlated with the efficiency of the urea-based fertilization, in a soil column higher than 10 cm.
19. Litter Controls Earthworm-Mediated Carbon and Nitrogen Transformations in Soil from Temperate Riparian Buffers
OpenAIRE
Maria Kernecker; Joann K. Whalen; Robert L. Bradley
2014-01-01
Nutrient cycling in riparian buffers is partly influenced by decomposition of crop, grass, and native tree species litter. Nonnative earthworms in riparian soils in southern Quebec are expected to speed the processes of litter decomposition and nitrogen (N) mineralization, increasing carbon (C) and N losses in gaseous forms or via leachate. A 5-month microcosm experiment evaluated the effect of Aporrectodea turgida on the decomposition of 3 litter types (deciduous leaves, reed canarygrass, an...
20. Coupling of microbial nitrogen transformations and climate in sclerophyll forest soils from the Mediterranean Region of central Chile.
Science.gov (United States)
Pérez, Cecilia A; Armesto, Juan J
2018-06-01
The Mediterranean region of central Chile is experiencing extensive "mega-droughts" with detrimental effects for the environment and economy of the region. In the northern hemisphere, nitrogen (N) limitation of Mediterranean ecosystems has been explained by the decoupling between N inputs and plant uptake during the dormant season. In central Chile, soils have often been considered N-rich in comparison to other Mediterranean ecosystems of the world, yet the impacts of expected intensification of seasonal drought remain unknown. In this work, we seek to disentangle patterns of microbial N transformations and their seasonal coupling with climate in the Chilean sclerophyll forest-type. We aim to assess how water limitation affects microbial N transformations, thus addressing the impact of ongoing regional climate trends on soil N status. We studied four stands of the sclerophyll forest-type in Chile. Field measurements in surface soils showed a 67% decline of free-living diazotrophic activity (DA) and 59% decrease of net N mineralization rates during the summer rainless and dormant season, accompanied by a stimulation of in-situ denitrification rates to values 70% higher than in wetter winter. Higher rates of both free-living DA and net N mineralization found during spring, provided evidence for strong coupling of these two processes during the growing season. Overall, the experimental addition of water in the field to litter samples almost doubled DA but had no effect on denitrification rates. We conclude that coupling of microbial mediated soil N transformations during the wetter growing season explains the N enrichment of sclerophyll forest soils. Expected increases in the length and intensity of the dry period, according to climate change models, reflected in the current mega-droughts may drastically reduce biological N fixation and net N mineralization, increasing at the same time denitrification rates, thereby potentially reducing long-term soil N capital
1. Effect of organic matter application and water regimes on the transformation of fertilizer nitrogen in a Philippine soil
International Nuclear Information System (INIS)
Yoshida, Tomio; Padre, B.C. Jr.
1975-01-01
Greenhouse experiments using the tracer technique showed that about 20 per cent of the fertilizer nitrogen added as basal to the Maahas clay soil was immobilized in submerged soils to which no organic material was added. The addition of organic matter to the soil increases the amount of nitrogen immobilized and the magnitude depends on the carbon to nitrogen ratio of the materials added. More fertilizer nitrogen was immobilized in the soils under upland and alternate wet-and-dry conditions than under submerged soil conditions. The uptake of fertilizer nitrogen by rice plants growing under submerged soil conditions ceased at the vegetative stage of growth because only a small amount of available nitrogen remains in the soil at this time, but the rice plant continued to absorb gradually untagged nitrogen from the soil throughout the reproductive stages of growth. Losses of fertilizer nitrogen were great under the alternate wet-and-dry conditions (submerged-upland). The loss of nitrogen from the soil-plant system was reduced by the addition of rice straw, which also reduced the uptake of fertilizer nitrogen but not the total dry matter production under the experimental conditions. Fertilizer nitrogen immobilized during the first crop remained mostly in the soil throughout the full period of the second crop. The total nitrogen uptake by rice plants was not affected by the soil moisture tension under the upland conditions used in the study but the movement of nitrogen from the leaves to the panicles during the reproductive stage seemed to decrease as the soil moisture tension increased. (auth.)
2. The transformation of nitrogen in soil under Robinia Pseudacacia shelterbelt and in adjoining cultivated field
Science.gov (United States)
Szajdak, L.; Gaca, W.
2009-04-01
The shelterbelts perform more than twenty different functions favorable to the environment, human economy, health and culture. The most important for agricultural landscape is increase of water retention, purification of ground waters and prevent of pollution spread in the landscape, restriction of wind and water erosion effects, isolation of polluting elements in the landscape, preservation of biological diversity in agricultural areas and mitigation of effects of unfavorable climatic phenomena. Denitrification is defined as the reduction of nitrate or nitrite coupled to electron transport phosphorylation resulting in gaseous N either as molecular N2 or as an oxide of N. High content of moisture, low oxygen, neutral and basic pH favour the denitrification. Nitrate reductase is an important enzyme involved in the process of denitrification. The reduction of nitrate to nitrite is catalyzed by nitrate reductase. Nitrite reductase is catalyzed reduction nitrite to nitrous oxide. The conversion of N2O to N2 is catalyzed by nitrous oxide reductase. This process leads to the lost of nitrogen in soil mainly in the form of N2 and N2O. Nitrous oxide is a greenhouse gas which cause significant depletion of the Earth's stratospheric ozone layer. The investigations were carried out in Dezydery Chlapowski Agroecological Landscape Park in Turew (40 km South-West of Poznań, West Polish Lowland). Our investigations were focused on the soils under Robinia pseudacacia shelterbelt and in adjoining cultivated field. The afforestation was created 200 years ago and it is consist of mainly Robinia pseudacacia with admixture of Quercus petraea and Quercus robur. This shelterbelt and adjoining cultivated field are located on grey-brown podzolic soil. The aim of this study is to present information on the changes of nitrate reductase activity in soil with admixture urea (organic form of nitrogen) in two different concentrations 0,25% N and 0,5% N. Our results have shown that this process
3. Litter Controls Earthworm-Mediated Carbon and Nitrogen Transformations in Soil from Temperate Riparian Buffers
Directory of Open Access Journals (Sweden)
Maria Kernecker
2014-01-01
Full Text Available Nutrient cycling in riparian buffers is partly influenced by decomposition of crop, grass, and native tree species litter. Nonnative earthworms in riparian soils in southern Quebec are expected to speed the processes of litter decomposition and nitrogen (N mineralization, increasing carbon (C and N losses in gaseous forms or via leachate. A 5-month microcosm experiment evaluated the effect of Aporrectodea turgida on the decomposition of 3 litter types (deciduous leaves, reed canarygrass, and soybean stem residue. Earthworms increased CO2 and N2O losses from microcosms with soybean residue, by 112% and 670%, respectively, but reduced CO2 and N2O fluxes from microcosms with reed canarygrass by 120% and 220%, respectively. Litter type controlled the CO2 flux (soybean ≥ deciduous-mix litter = reed canarygrass > no litter and the N2O flux (soybean ≥ no litter ≥ reed canarygrass > deciduous-mix litter. However, in the presence of earthworms, there was a slight increase in C and N gaseous losses of C and N relative to their losses via leachate, across litter treatments. We conclude that litter type determines the earthworm-mediated decomposition effect, highlighting the importance of vegetation management in controlling C and N losses from riparian buffers to the environment.
4. [Responses of rhizosphere nitrogen and phosphorus transformations to different acid rain intensities in a hilly red soil tea plantation].
Science.gov (United States)
Chen, Xi; Chen, Fu-sheng; Ye, Su-qiong; Yu, Su-qin; Fang, Xiang-min; Hu, Xiao-fei
2015-01-01
Tea (Camellia sinensis) plantation in hilly red soil region has been long impacted by acid deposition, however its effects on nitrogen (N) and phosphorus (P) transformations in rhizosphere soils remain unclear. A 25-year old tea plantation in a typical hilly red soil region was selected for an in situ simulation experiment treated by pH 4.5, pH 3.5, pH 2.5 and control. Rhizosihere and bulk soils were collected in the third year from the simulated acid deposition experiment. Soil mineral N, available P contents and major enzyme activities were analyzed using the chemical extraction and biochemical methods, and N and P mineralization rates were estimated using the indoor aerobic incubation methods. Our results showed that compared to the control, the treatments of pH 4.5, pH 3.5 and pH 2.5, respectively decreased 7.1%, 42.1% and 49.9% NO3(-)-N, 6.4%, 35.9% and 40.3% mineral N, 10.5%, 41.1% and 46.9% available P, 18.7%, 30.1% and 44.7% ammonification rate, 3.6%, 12.7% and 38.8% net N-mineralization rate, and 31.5%, 41.8% and 63.0% P mineralization rate in rhizosphere soils; however, among the 4 treatments, rhizosphere soil nitrification rate was not significantly different, the rhizosphere soil urease and acid phosphatase activities generally increased with the increasing intensity of acid rain (PpH 4.5, pH 3.5 and pH 2.5 did not cause significant changes in NO3(-)-N, mineral N, available P as well as in the rates of nitrification, ammonification, net N-mineralization and P mineralization. With increasing the acid intensity, the rhizosphere effects of NH4+-N, NO3(-)-N, mineral N, ammonification and net N-mineralization rates were altered from positive to negative effects, those of urease and acid phosphatease showed the opposite trends, those of available P and P mineralization were negative and that of nitrification was positive. In sum, prolonged elevated acid rain could reduce N and P transformation rates, decrease their availability, alter their rhizosphere
5. Influence of Pesticides and Nitrogen Fertilizers on Bacterial Activities and Nitrogen Transformations in Some of the Soils of North Iraq
International Nuclear Information System (INIS)
Shall, K.G.; Khan, M.F.A.
1981-01-01
For the proper development of agriculture in North Iraq having a mediterranean type of climate, soils of medium to below average fertility and fruit/crop production mostly confined to hilly valley lands, the use of fertilizers, insecticides and herbicides is being planned at maximum levels for the years to come. The pesticides being used are dipterex (= chlorofos = dimethyl 2,2,2-trichloro-1-hydroxyethyl phosphonate), benlate (= benomyl = methyl N-[l-(butyl-carbomoyl)-2-benzimidazole] carbamate), mesurol (= methiocarb = 4-methylthio-3,5-xylyl N-4Dethyl-carbamate) and topsin (= thiophanate = 1,2-di-(3-ethoxycarbonyl-2-thioureido) benzene)
6. Influence of Pesticides and Nitrogen Fertilizers on Bacterial Activities and Nitrogen Transformations in Some of the Soils of North Iraq
Energy Technology Data Exchange (ETDEWEB)
Shall, K. G.; Khan, M. F.A. [Department of Soil Science, College of Agriculture, University of Sulaimaniyah (Iraq)
1981-05-15
For the proper development of agriculture in North Iraq having a mediterranean type of climate, soils of medium to below average fertility and fruit/crop production mostly confined to hilly valley lands, the use of fertilizers, insecticides and herbicides is being planned at maximum levels for the years to come. The pesticides being used are dipterex (= chlorofos = dimethyl 2,2,2-trichloro-1-hydroxyethyl phosphonate), benlate (= benomyl = methyl N-[l-(butyl-carbomoyl)-2-benzimidazole] carbamate), mesurol (= methiocarb = 4-methylthio-3,5-xylyl N-4Dethyl-carbamate) and topsin (= thiophanate = 1,2-di-(3-ethoxycarbonyl-2-thioureido) benzene)
7. Quantification Of 15N Internal Transformation To Assess Nitrogen Supply Capacity In Deforested Soil
International Nuclear Information System (INIS)
Handayani, I.P.; Prawito, P.; Sisworo, E.L.
2002-01-01
Quantification of deforested soil's capacity to supply available N via mineralization and immobilization using 15N pool dilution is crucial to make fertilizer recommendation. The objective of this research was to measure the soil's capacity to minemlize and ilmnobilize N, so that the actual value of available N released by soil can be predicted. The results showed that Imperata grassland released the highest available N (amonium + nitrate) about 33.93 mg/kg/d and can immobilize 11.68 mg/kg/d of N. On the other hand, agriculture lields had the lowest inorganic N by nearly 23.15 mg/kg/d, and no immobilization occurred. The implication is that agriculture fields have a very low labile and stabile pool N (nearly 0), while Imperata grassland have capacity to store more pool N into labile or stabil pool (about 34%). In conclusion, dynamics of N cycling in ecosystem are dependent upon the content of pool C-N utilized by microorganisms and plants
8. Effects of Wheat and Faba Bean Intercropping on Microorganism Involved in Nitrogen Transformation in the Rhizosphere Soils
Directory of Open Access Journals (Sweden)
TANG Yan-fen
2016-09-01
Full Text Available Soil microorganism is one of the key factors that affects soil ecological activity. It is an important symbol of soil health, and the soil nitrogen cycle is closely related to the microorganisms. The relationship between nitrogen and microorganisms under the intercropping is im-portant for the farmland ecosystem. In this paper, phospholipid fatty acids(PLFA analysis was used to determine soil microbial communi-ties, e.g., biomasses of anaerobic bacteria, aerobic bacteria, bacteria, fungi and actinobacteria. The abundance of nitrifying genes(AOB, AOA and three denitrifying genes (nirK, norB, nosZ were measured using real-time quantitative polymerase chain reaction. The enzymes, nitrate and ammonium concentrations were measured using conventional methods. The results showed that along with the growth period, the TPLFAs(total phospholipid fatty acids increased and the bacterias, fungus, actinomyces and aerobic bacterias significantly(P<0.05 dif-fered between intercropping and monoculture. The greater abundance of AOB than AOA and the variation range of 105~106 were observed in all samples. The gene copies of norB and nosZ were pronounced by intercropping in the rhizosphere of faba bean at elongation and heading stages, respectively. The abundance of nirK remarkably(P<0.05differed between intercropping and monoculture. In intercropping rhizo-sphere, the contents of NO3--N were lower than monoculture, while the NH4+-N contents were converse (P<0.05. Conclusively, wheat and fa-ba bean intercropping system could change rhizosphere microenvironment, and then the microbial community structure in the soils, which would facilitate the conservation and supplying of soil nitrogen and reduce the nitrogen loss and pollution under the intercropping conditions to some extent. This might be the nitrogen nutrition mechanism for the overyielding of wheat and faba bean intercropping system.
9. Soil and fertilizer nitrogen
International Nuclear Information System (INIS)
Winteringham, F.P.W.
1984-01-01
As a result of the intensified practices and effectively diminishing land resources per capita, increasing weights of both native soil- and added fertilizer-nitrogen will be lost to agriculture and its products, and will find their way into the environment. Soil-nitrogen levels and contingent productivity can nevertheless be maintained in the face of these losses on the basis of improved soil-N management. In some local situations nitrate levels in water for drinking purposes are likely to continue rising. In some cases agriculture and clearance practices are only one of several sources. In others they are clearly mainly responsible. In developing countries these losses represent those of a relatively increasingly costly input. This is due to the fact that industrial fertilizer nitrogen production is a particularly high energy-consuming process. In the more advanced industrialized countries they represent an addition to the problems and costs of environmental quality and health protection. The programmes, information and data reviewed here suggest that these problems can be contained by improved and extended soil and water management in agriculture on the basis of existing technology. In particular there appears to be enormous scope for the better exploitation of existing legumes both as non-legume crop alternatives or as biofertilizers which also possess more desirable C:N ratios than chemical fertilizer
10. Dissolved nitrogen transformations and microbial community structure in the organic layer of forest soils in Olkiluoto in 2006
International Nuclear Information System (INIS)
Potila, H.; Sarjala, T.; Aro, L.
2007-02-01
Carbon (C) and nitrogen (N) cycles in the ecosystem are strongly coupled. Biomass, structure and activity of the bacterial and fungal community are the key factors influencing C and N cycles. Changes in the function of soil microbial community can be a signal of plant responses to environmental changes. Dissolved N compounds, microbial biomass, microbial activity, fungal community structure and functional diversity of microbial communities were measured in September 2006 from five monitoring plots on Olkiluoto to assess information about soil microbial community structure and activity. High within and between variation in the studied plots were detected. However, in this study the values and their variation in the level of N mineralisation, dissolved N compounds, fungal biomass and microbial community structure in the studied plots were within a normal range in comparison with other published data of similar forest types in Finland. (orig.)
11. Isotopic dilution methods to determine the gross transformation rates of nitrogen, phosphorus, and sulfur in soil: a review of the theory, methodologies, and limitations
International Nuclear Information System (INIS)
Di, H. J.; Cameron, K. C.; McLaren, R. G.
2000-01-01
The rates at which nutrients are released to, and removed from, the mineral nutrient pool are important in regulating the nutrient supply to plants. These nutrient transformation rates need to be taken into account when developing nutrient management strategies for economical and sustainable production. A method that is gaining popularity for determining the gross transformation rates of nutrients in the soil is the isotopic dilution technique. The technique involves labelling a soil mineral nutrient pool, e.g. NH 4 + , NO 3 - , PO 4 3- , or SO 4 2- , and monitoring the changes with time of the size of the labelled nutrient pool and the excess tracer abundance (atom %, if stable isotope tracer is used) or specific activity (if radioisotope is used) in the nutrient pool. Because of the complexity of the concepts and procedures involved, the method has sometimes been used incorrectly, and results misinterpreted. This paper discusses the isotopic dilution technique, including the theoretical background, the methodologies to determine the gross flux rates of nitrogen, phosphorus, and sulfur, and the limitations of the technique. The assumptions, conceptual models, experimental procedures, and compounding factors are discussed. Possible effects on the results by factors such as the uniformity of tracer distribution in the soil, changes in soil moisture content, substrate concentration, and aeration status, and duration of the experiment are also discussed. The influx and out-flux transformation rates derived from this technique are often contributed by several processes simultaneously, and thus cannot always be attributed to a particular nutrient transformation process. Despite the various constraints or possible compounding factors, the technique is a valuable tool that can provide important quantitative information on nutrient dynamics in the soil-plant system. Copyright (2000) CSIRO Publishing
12. The mineralization and transformation of both added organic nitrogen and native soil N in red soils from four different ecological conditions
International Nuclear Information System (INIS)
Ye Qingfu; Zhang Qinzheng; He Zhenli; Xi Haifu; Wu Gang; Wilson, M.J.
1998-01-01
The NH 4 + -N, microbial biomass-N, humus-N, and extractable organic N derived from the added 15 N-labelled ryegrass and soil indigenous pool were measured separately with 15 N tracing techniques. Based on the recovery of NH 4 + - 15 N and lost- 15 N (mainly as NH 3 ), more than 30% of the added ryegrass 15 N was mineralized in 15 d. The amount of mineralized N increased with time up to 90 d for all soils except for the upland soil in which it decreased slightly. The mineralization of ryegrass N and incorporation of ryegrass- 15 N into microbial biomass was greatest in upland soil. The transformation of ryegrass 15 N into humus 15 N occurred rapidly in 15 d, with higher humus 15 N occurring in the upland or tea-garden soil than the paddy and unarable soil. The addition of ryegrass caused additional mineralization of soil indigenous organic N and enhanced the turnover of both microbial biomass N and stable organic N in soils
13. Use of nitrogen-15 in soil-plant studies
International Nuclear Information System (INIS)
Sachdev, M.S.; Sachdev, P.; Subbiah, B.V.
1996-01-01
In this paper an overview of the selected work carried out in the country and elsewhere on the fertilizer nitrogen use efficiency, fate and balance-sheet, soil and fertilizer nitrogen transformations and biological nitrogen fixation using 15 N is given. 129 refs., 4 tabs
14. Mean age distribution of inorganic soil-nitrogen
Science.gov (United States)
Woo, Dong K.; Kumar, Praveen
2016-07-01
Excess reactive nitrogen in soils of intensively managed landscapes causes adverse environmental impact, and continues to remain a global concern. Many novel strategies have been developed to provide better management practices and, yet, the problem remains unresolved. The objective of this study is to develop a model to characterize the "age" of inorganic soil-nitrogen (nitrate, and ammonia/ammonium). We use the general theory of age, which provides an assessment of the time elapsed since inorganic nitrogen has been introduced into the soil system. We analyze a corn-corn-soybean rotation, common in the Midwest United States, as an example application. We observe two counter-intuitive results: (1) the mean nitrogen age in the topsoil layer is relatively high; and (2) mean nitrogen age is lower under soybean cultivation compared to corn although no fertilizer is applied for soybean cultivation. The first result can be explained by cation-exchange of ammonium that retards the leaching of nitrogen, resulting in an increase in the mean nitrogen age near the soil surface. The second result arises because the soybean utilizes the nitrogen fertilizer left from the previous year, thereby removing the older nitrogen and reducing mean nitrogen age. Estimating the mean nitrogen age can thus serve as an important tool to disentangle complex nitrogen dynamics by providing a nuanced characterization of the time scales of soil-nitrogen transformation and transport processes.
15. Nitrogen transformations in wetlands: Effects of water flow patterns
Energy Technology Data Exchange (ETDEWEB)
Davidsson, T.
1997-11-01
In this thesis, I have studied nitrogen turnover processes in water meadows. A water meadow is a wetland where water infiltrates through the soil of a grassland field. It is hypothesized that infiltration of water through the soil matrix promotes nutrient transformations compared to surface flow of water, by increasing the contact between water, nutrients, soil organic matter and bacteria. I have studied how the balance between nitrogen removal (denitrification, assimilative uptake, adsorption) and release (mineralization, desorption) processes are affected by water flow characteristics. Mass balance studies and direct denitrification measurements at two field sites showed that, although denitrification was high, net nitrogen removal in the water meadows was poor. This was due to release of ammonium and dissolved organic nitrogen (DON) from the soils. In laboratory studies, using {sup 15}N isotope techniques, I have shown that nitrogen turnover is considerably affected by hydrological conditions and by soil type. Infiltration increased virtually all the nitrogen processes, due to deeper penetration of nitrate and oxygen, and extended zones of turnover processes. On the contrary, soils and sediments with surface water flow, diffusion is the main transfer mechanism. The relation between release and removal processes sometimes resulted in shifts towards net nitrogen production. This occurred in infiltration treatments when ammonium efflux was high in relation to denitrification. It was concluded that ammonium and DON was of soil origin and hence not a product of dissimilatory nitrate reduction to ammonium. Both denitrification potential and mineralization rates were higher in peaty than in sandy soil. Vertical or horizontal subsurface flow is substantial in many wetland types, such as riparian zones, tidal salt marshes, fens, root-zone systems and water meadows. Moreover, any environment where aquatic and terrestrial ecosystems meet, and where water level fluctuates
16. Different effects of transgenic maize and nontransgenic maize on nitrogen-transforming archaea and bacteria in tropical soils
NARCIS (Netherlands)
Cotta, Simone Raposo; Franco Dias, Armando Cavalcante; Marriel, Ivanildo Evodio; Andreote, Fernando Dini; Seldin, Lucy; van Elsas, Jan Dirk
2014-01-01
The composition of the rhizosphere microbiome is a result of interactions between plant roots, soil, and environmental conditions. The impact of genetic variation in plant species on the composition of the root-associated microbiota remains poorly understood. This study assessed the abundances and
17. Uptake of fertilizer nitrogen and soil nitrogen by rice using 15N-labelled nitrogen fertilizer
International Nuclear Information System (INIS)
Reddy, K.R.; Patrick, W.H. Jr.
1980-01-01
Data from five field experiments using labelled nitrogen fertilizer were used to determine the relative effects of soil nitrogen and fertilizer nitrogen on rice yield. Yield of grain was closely correlated with total aboveground nitrogen uptake (soil + fertilizer), less closely correlated with soil nitrogen uptake and not significantly correlated with fertilizer nitrogen uptake. When yield increase rather than yield was correlated with fertilizer nitrogen uptake, the correlation coefficient was statistically significant. (orig.)
18. Nitrogen transformations in stratified aquatic microbial ecosystems
DEFF Research Database (Denmark)
Revsbech, N. P.; Risgaard-Petersen, N.; Schramm, A.
2006-01-01
Abstract New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about n...
19. Nitrogen Soil Testing for Corn in Virginia
OpenAIRE
Evanylo, Gregory K.; Alley, Marcus M., 1947-
2009-01-01
An adequate supply of plant-available nitrogen (N) is crucial for efficient corn production, and corn N requirements are greater than any other nutrient. This publication reviews the link between nitrogen and corn production, nitrogen behavior, soil testing, test procedures and recommendations.
20. Modelling the soil nitrogen denitrification
International Nuclear Information System (INIS)
Budoi, G.H.; Danuso, F.; Giovanardi, R.; Gavriluta, A.; Alexandrescu, A.; Bireescu, L.
1999-01-01
The paper presents the differential equations used to compute the daily amounts of N denitrified and to compute the amount of N denitrified in a given period of time. It shows also the equations which compute the correction factors of the maximum denitrification rate as a function of soil temperature (F td ), moisture (F md ) and pH (F pHd ), original equations used by NICROS - nitrogen crop simulation model to describe the influence of these abiotic factors. The temperature factor, F td . The optimum temperature for denitrification is between 25-37 o C. The process is slow at temperatures below 10 o C, there is an increased inhibition below 5 o C and stop completely at 0 o C. The maximum temperature for denitrification is practically that which limits the soil microbiological activity, generally 75 o C. The following relations are used to compute the F td factor: F td 1/(1 + e -0,3347 tmed+ 4,99 ) if t med ≤ 37; F td = 1 - (t med - 37)/38 if 75 > t med > 37; F td = 0 if t med ≥ 75, where t med is the average daily soil temperature. The moisture factor, F md . The denitrification has maximum intensity at soil water saturation, U sat , and stop below 80 % from U sat . F md = 0 if soil moisture U s ≤ 0,8*U sat , and F md = (U s - 0,8*U sat )/(U sat - 0,8*U sat ) if U s > 0,8*U sat . The pH factor, F pHd . Denitrification takes place at pH between 4-9 and is maximum at pH between 7-8. The relations used to compute the F pHd factor are: F pHd = 1/(1 + e -3,1923 pH + 18,87 ) if pH ≤ 8; F pHd = (9 - pH) when pH is between 8-9, and F pHd = 0 if pH > 9. Refs. 6 (author)
1. Nitrogen transformations in stratified aquatic microbial ecosystems
DEFF Research Database (Denmark)
Revsbech, Niels Peter; Risgaard-Petersen, N.; Schramm, Andreas
2006-01-01
Abstract New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about n...... performing dissimilatory reduction of nitrate to ammonium have given new dimensions to the understanding of nitrogen cycling in nature, and the occurrence of these organisms and processes in stratified microbial communities will be described in detail.......Abstract New analytical methods such as advanced molecular techniques and microsensors have resulted in new insights about how nitrogen transformations in stratified microbial systems such as sediments and biofilms are regulated at a µm-mm scale. A large and ever-expanding knowledge base about...... nitrogen fixation, nitrification, denitrification, and dissimilatory reduction of nitrate to ammonium, and about the microorganisms performing the processes, has been produced by use of these techniques. During the last decade the discovery of anammmox bacteria and migrating, nitrate accumulating bacteria...
2. Worldwide organic soil carbon and nitrogen data
Energy Technology Data Exchange (ETDEWEB)
Zinke, P.J.; Stangenberger, A.G. [Univ. of California, Berkeley, CA (United States). Dept. of Forestry and Resource Management; Post, W.M.; Emanual, W.R.; Olson, J.S. [Oak Ridge National Lab., TN (United States)
1986-09-01
The objective of the research presented in this package was to identify data that could be used to estimate the size of the soil organic carbon pool under relatively undisturbed soil conditions. A subset of the data can be used to estimate amounts of soil carbon storage at equilibrium with natural soil-forming factors. The magnitude of soil properties so defined is a resulting nonequilibrium values for carbon storage. Variation in these values is due to differences in local and geographic soil-forming factors. Therefore, information is included on location, soil nitrogen content, climate, and vegetation along with carbon density and variation.
3. Soil nitrogen as fertilizer or pollutant
International Nuclear Information System (INIS)
1980-01-01
The results of 22 studies and surveys are reported on a global scale on N fertilizer applications and the fate of 15 N-labelled fertilizer in various soils, water and nitrate movement, residues, soil-N transformations in relation to leaching, nitrate pollution, nitrogen balance and related aspects under a variety of climatic conditions and crop cultivation are described. Some studies did not contain actual isotope applications, and have therefore not been entered in INIS as individual items. A 13-page report on research coordination includes background information, common methodology, field lysimeter experiments and their results, and the collection and evaluation of data. In conclusion, variations in the fate and behaviour of N residues are considered as are water pollution, the critical role of models and the need for behaviour prediction, the fate of agricultural N residues, the conservation of useful N residues, and future programmes. The report concludes with 7 recommendations, 20 references, and 3 annexes. Annex 1 lists programme participants by country, chief investigator, basis of collaboration and subject area, Annex 2 the titles and authors of working papers; Annex 3 gives guidelines for 15 N-residue experiment objectives, data presentation, etc. All participants in the Coordination Meeting are listed
4. Natural 15N abundance of soil N pools and N2O reflect the nitrogen dynamics of forest soils
DEFF Research Database (Denmark)
Pörtl, K.; Zechmeister-Boltenstern, S.; Wanek, W.
2007-01-01
Natural N-15 abundance measurements of ecosystem nitrogen (N) pools and N-15 pool dilution assays of gross N transformation rates were applied to investigate the potential of delta N-15 signatures of soil N pools to reflect the dynamics in the forest soil N cycle. Intact soil cores were collected...
5. An online tool for tracking soil nitrogen
Science.gov (United States)
Wang, J.; Umar, M.; Banger, K.; Pittelkow, C. M.; Nafziger, E. D.
2016-12-01
Near real-time crop models can be useful tools for optimizing agricultural management practices. For example, model simulations can potentially provide current estimates of nitrogen availability in soil, helping growers decide whether more nitrogen needs to be applied in a given season. Traditionally, crop models have been used at point locations (i.e. single fields) with homogenous soil, climate and initial conditions. However, nitrogen availability across fields with varied weather and soil conditions at a regional or national level is necessary to guide better management decisions. This study presents the development of a publicly available, online tool that automates the integration of high-spatial-resolution forecast and past weather and soil data in DSSAT to estimate nitrogen availability for individual fields in Illinois. The model has been calibrated with field experiments from past year at six research corn fields across Illinois. These sites were treated with applications of different N fertilizer timings and amounts. The tool requires minimal management information from growers and yet has the capability to simulate nitrogen-water-crop interactions with calibrated parameters that are more appropriate for Illinois. The results from the tool will be combined with incoming field experiment data from 2016 for model validation and further improvement of model's predictive accuracy. The tool has the potential to help guide better nitrogen management practices to maximize economic and environmental benefits.
6. 9 Nitrogen Uptake in Soils
African Journals Online (AJOL)
User
+ depletion zone and. L. C the mean concentration in solution. D is the soil NH4. + diffusion coefficient, and b is the soil NH. 4. + buffer power. D = DLθ fL / b. (5) where D. L is the NH. 4. + diffusion coefficient in water, θ is the soil water fraction by volume, and fL is the diffusion impedance factor. Kirk & Soliva (1997) assumed ...
7. [Temporal-spatial distribution of agricultural diffuse nitrogen pollution and relationship with soil respiration and nitrification].
Science.gov (United States)
Wei, Ouyang; Cai, Guan-Qing; Huang, Hao-Bo; Geng, Xiao-Jun
2014-06-01
8. Are Nitrogen Fertilizers Deleterious to Soil Health?
Directory of Open Access Journals (Sweden)
Bijay- Singh
2018-04-01
Full Text Available Soil is one of the most important natural resources and medium for plant growth. Anthropogenic interventions such as tillage, irrigation, and fertilizer application can affect the health of the soil. Use of fertilizer nitrogen (N for crop production influences soil health primarily through changes in organic matter content, microbial life, and acidity in the soil. Soil organic matter (SOM constitutes the storehouse of soil N. Studies with 15N-labelled fertilizers show that in a cropping season, plants take more N from the soil than from the fertilizer. A large number of long-term field experiments prove that optimum fertilizer N application to crops neither resulted in loss of organic matter nor adversely affected microbial activity in the soil. Fertilizer N, when applied at or below the level at which maximum yields are achieved, resulted in the build-up of SOM and microbial biomass by promoting plant growth and increasing the amount of litter and root biomass added to soil. Only when fertilizer N was applied at rates more than the optimum, increased residual inorganic N accelerated the loss of SOM through its mineralization. Soil microbial life was also adversely affected at very high fertilizers rates. Optimum fertilizer use on agricultural crops reduces soil erosion but repeated application of high fertilizer N doses may lead to soil acidity, a negative soil health trait. Site-specific management strategies based on principles of synchronization of N demand by crops with N supply from all sources including soil and fertilizer could ensure high yields, along with maintenance of soil health. Balanced application of different nutrients and integrated nutrient management based on organic manures and mineral fertilizers also contributed to soil health maintenance and improvement. Thus, fertilizer N, when applied as per the need of the field crops in a balanced proportion with other nutrients and along with organic manures, if available with the
9. Modelling carbon and nitrogen turnover in variably saturated soils
Science.gov (United States)
Batlle-Aguilar, J.; Brovelli, A.; Porporato, A.; Barry, D. A.
2009-04-01
Natural ecosystems provide services such as ameliorating the impacts of deleterious human activities on both surface and groundwater. For example, several studies have shown that a healthy riparian ecosystem can reduce the nutrient loading of agricultural wastewater, thus protecting the receiving surface water body. As a result, in order to develop better protection strategies and/or restore natural conditions, there is a growing interest in understanding ecosystem functioning, including feedbacks and nonlinearities. Biogeochemical transformations in soils are heavily influenced by microbial decomposition of soil organic matter. Carbon and nutrient cycles are in turn strongly sensitive to environmental conditions, and primarily to soil moisture and temperature. These two physical variables affect the reaction rates of almost all soil biogeochemical transformations, including microbial and fungal activity, nutrient uptake and release from plants, etc. Soil water saturation and temperature are not constants, but vary both in space and time, thus further complicating the picture. In order to interpret field experiments and elucidate the different mechanisms taking place, numerical tools are beneficial. In this work we developed a 3D numerical reactive-transport model as an aid in the investigation the complex physical, chemical and biological interactions occurring in soils. The new code couples the USGS models (MODFLOW 2000-VSF, MT3DMS and PHREEQC) using an operator-splitting algorithm, and is a further development an existing reactive/density-dependent flow model PHWAT. The model was tested using simplified test cases. Following verification, a process-based biogeochemical reaction network describing the turnover of carbon and nitrogen in soils was implemented. Using this tool, we investigated the coupled effect of moisture content and temperature fluctuations on nitrogen and organic matter cycling in the riparian zone, in order to help understand the relative
10. Nitrogen uptake and fertilizer nitrogen use efficiency of wheat under different soil water conditions
International Nuclear Information System (INIS)
Wang Baiqun; Zhang Wei; Yu Cunzu
1999-01-01
The pot experiment was conducted to study the effects of soil water regime and fertilizer nitrogen rate on the yields, nitrogen uptake and fertilizer nitrogen utilization of wheat by using 15 N tracer method. The results showed that the aboveground biomass, stem yield and grain yield increased with the increase of soil moisture in the fertilizer nitrogen treatments. All the yield increased with the increase of the fertilizer nitrogen rate in the soil water treatments. It was found that both soil water regime and fertilizer nitrogen rate significantly influenced the amount of nitrogen uptake by wheat according to the variance analysis. The amount of nitrogen uptake increased with the rise of the soil moisture in fertilizer nitrogen treatments and the amount also increased with the increase of the urea nitrogen rate in the soil water regime. Soil water regimes not only had an impact on nitrogen uptake but also had a close relationship with soil nitrogen supply and fertilizer nitrogen use efficiency. The soil A values decreased in urea treatment and increased with the rise of the soil moisture in the combination treatment of urea with pig manure. The fertilizer nitrogen use efficiency rose with the rise of the soil moisture in the same fertilizer nitrogen treatment. The fertilizer nitrogen use efficiency of the urea treatment was 13.3%, 27.9% and 32.3% in the soils with 50%, 70% and 90% of the field water capacity, respectively. The fertilizer nitrogen use efficiency in the combination treatment of urea with pig manure was 20.0%, 29.9% and 34.4% in the soils of above three levels, respectively. It was concluded that the low soil moisture restricted urea nitrogen use efficiency (UNUE) and the UNUE could be raised by combination treatment of urea with manure in the soil of enough moisture
11. Availability of residual nitrogen from fertilizers in soil
International Nuclear Information System (INIS)
Jakovljevic, M.; Filipovic, R.; Petrovic, M.
1983-01-01
The plant availability of residual fertilizer nitrogen for the next crop was studied in chernozem and pseudogley soils. Release of nitrogen was examined after incubation at 3 and 30 0 C. It was found that the use of increased doses of nitrogen fertilizer (ammonium nitrate) led to an increased release of residual fertilizer nitrogen into plant available forms. The release of this nitrogen fraction was 5-10 times faster in comparison with the remaining soil nitrogen. (author)
12. Availability of residual nitrogen from fertilizers in soil
Energy Technology Data Exchange (ETDEWEB)
Jakovljevic, M.; Filipovic, R.; Petrovic, M. (Institut za Primeni Nuklearne Energije u Poljoprivedri, Veterinarstvu i Sumarstvu, Zemun (Yugoslavia))
1983-05-01
The plant availability of residual fertilizer nitrogen for the next crop was studied in chernozem and pseudogley soils. Release of nitrogen was examined after incubation at 3 and 30/sup 0/C. It was found that the use of increased doses of nitrogen fertilizer (ammonium nitrate) led to an increased release of residual fertilizer nitrogen into plant available forms. The release of this nitrogen fraction was 5-10 times faster in comparison with the remaining soil nitrogen.
13. Mineralization of nitrogen by protozoan activity in soil
NARCIS (Netherlands)
Kuikman, P.
1990-01-01
In general, more than 95% of the nitrogen in soils is present in organic forms. This nitrogen is not directly available to plants unless microbial decomposition takes place with the release of mineral nitrogen. In modern agriculture, nitrogen is often applied to arable soils as a fertilizer
14. MOTOR 2.0: module for transformation of organic matter and nutrients in soil; user guide and technical documentation
NARCIS (Netherlands)
Assinck, F.B.T.; Rappoldt, C.
2004-01-01
MOTOR is a MOdule describing the Transformation of Organic matteR and nutrients in soil. It calculates the transformations between pools of organic matter and mineral nitrogen in soil. Pools are characterized by a carbon and nitrogen content and can be labelled. MOTOR is a flexible tool because the
15. Influence of forest disturbance on stable nitrogen isotope ratios in soil and vegetation profiles
Science.gov (United States)
Jennifer D. Knoepp; Scott R. Taylor; Lindsay R. Boring; Chelcy F. Miniat
2015-01-01
Soil and plant stable nitrogen isotope ratios (15 N) are influenced by atmospheric nitrogen (N) inputs and processes that regulate organic matter (OM) transformation and N cycling. The resulting 15N patterns may be useful for discerning ecosystem differences in N cycling. We studied two ecosystems; longleaf pine wiregrass (...
16. [Effects of controlled release blend bulk urea on soil nitrogen and soil enzyme activity in wheat and rice fields].
Science.gov (United States)
Zhang, Jing Sheng; Wang, Chang Quan; Li, Bing; Liang, Jing Yue; He, Jie; Xiang, Hao; Yin, Bin; Luo, Jing
2017-06-18
A field experiment was conducted to investigate the effect of controlled-release fertilizer (CRF) combined with urea (UR) on the soil fertility and environment in wheat-rice rotation system. Changes in four forms of nitrogen (total nitrogen, ammonium nitrogen, nitrate nitrogen, and microbial biomass nitrogen) and in activities of three soil enzymes participating in nitrogen transformation (urease, protease, and nitrate reductase) were measured in seven fertilization treatments (no fertilization, routine fertilization, 10%CRF+90%UR, 20%CRF+80%UR, 40%CRF+60%UR, 80%CRF+20%UR, and 100%CRF). The results showed that soil total nitrogen was stable in the whole growth period of wheat and rice. There was no significant difference among the treatments of over 20% CRF in soil total nitrogen content of wheat and rice. The soil inorganic nitrogen content was increased dramatically in treatments of 40% or above CRF during the mid-late growing stages of wheat and rice. With the advance of the growth period, conventional fertilization significantly decreased soil microbial biomass nitrogen, but the treatments of 40% and above CRF increased the soil microbial biomass nitrogen significantly. The soil enzyme activities were increased with over 40% of CRF in the mid-late growing stage of wheat and rice. By increasing the CRF ratio, the soil protease activity and nitrate reductase activity were improved gradually, and peaked in 100% CRF. The treatments of above 20% CRF could decrease the urease activity in tillering stage of rice and delay the peak of ammonium nitrogen, which would benefit nitrogen loss reduction. The treatments of 40% and above CRF were beneficial to improving soil nitrogen supply and enhancing soil urease and protease activities, which could promote the effectiveness of nitrogen during the later growth stages of wheat and rice. The 100% CRF treatment improved the nitrate reductase activity significantly during the later stage of wheat and rice. Compared with the
17. Transformers as a potential for soil contamination
Directory of Open Access Journals (Sweden)
N. Stojić
2014-10-01
Full Text Available The aim of this paper is to investigate the presence of PCBs and heavy metals in the surrounding soil and also in the soil of the receiving pit located below the PCB contaminated transformer. Concentrations of PCBs in our samples are ranged from 0,308 to 0,872 mg/kg of absolutely dry soil.
18. Fate of nitrogenous fertilizers in forest soil
International Nuclear Information System (INIS)
Pang, P.C.K.
1984-01-01
The fate of the nitrogenous fertilizers through the processes of denitrification, ammonia volatilization, immobilization and uptake by a conifer is determined, with the aid of 15 N-labelled fertizers. The foliage of Douglas-fir was able to absorb gaseous ammonia under optimal conditions. Denitrification and immobilization of fertilizer-N by forest soil were highest with forest floor samples and decreased with depth. Laboratory studies with four-year-old Douglas-fir demostrated that a higher quantity of fertilizer-N was utilized by trees when the nitrogen was supplied as NO 3 - rather than NH 4 + . (M.A.C.) [pt
19. Soil Carbon and Nitrogen Cycle Modeling
Science.gov (United States)
Woo, D.; Chaoka, S.; Kumar, P.; Quijano, J. C.
2012-12-01
Second generation bioenergy crops, such as miscanthus (Miscantus × giganteus) and switchgrass (Panicum virgatum), are regarded as clean energy sources, and are an attractive option to mitigate the human-induced climate change. However, the global climate change and the expansion of perennial grass bioenergy crops have the power to alter the biogeochemical cycles in soil, especially, soil carbon storages, over long time scales. In order to develop a predictive understanding, this study develops a coupled hydrological-soil nutrient model to simulate soil carbon responses under different climate scenarios such as: (i) current weather condition, (ii) decreased precipitation by -15%, and (iii) increased temperature up to +3C for four different crops, namely miscanthus, switchgrass, maize, and natural prairie. We use Precision Agricultural Landscape Modeling System (PALMS), version 5.4.0, to capture biophysical and hydrological components coupled with a multilayer carbon and ¬nitrogen cycle model. We apply the model at daily time scale to the Energy Biosciences Institute study site, located in the University of Illinois Research Farms, in Urbana, Illinois. The atmospheric forcing used to run the model was generated stochastically from parameters obtained using available data recorded in Bondville Ameriflux Site. The model simulations are validated with observations of drainage and nitrate and ammonium concentrations recorded in drain tiles during 2011. The results of this study show (1) total soil carbon storage of miscanthus accumulates most noticeably due to the significant amount of aboveground plant carbon, and a relatively high carbon to nitrogen ratio and lignin content, which reduce the litter decomposition rate. Also, (2) the decreased precipitation contributes to the enhancement of total soil carbon storage and soil nitrogen concentration because of the reduced microbial biomass pool. However, (3) an opposite effect on the cycle is introduced by the increased
20. Biochar decelerates soil organic nitrogen cycling but stimulates soil nitrification in a temperate arable field trial.
Directory of Open Access Journals (Sweden)
Judith Prommer
Full Text Available Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50-80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies.
1. Biochar decelerates soil organic nitrogen cycling but stimulates soil nitrification in a temperate arable field trial.
Science.gov (United States)
Prommer, Judith; Wanek, Wolfgang; Hofhansl, Florian; Trojan, Daniela; Offre, Pierre; Urich, Tim; Schleper, Christa; Sassmann, Stefan; Kitzler, Barbara; Soja, Gerhard; Hood-Nowotny, Rebecca Clare
2014-01-01
Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N) cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem) in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50-80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers) and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies.
2. Biochar Decelerates Soil Organic Nitrogen Cycling but Stimulates Soil Nitrification in a Temperate Arable Field Trial
Science.gov (United States)
Prommer, Judith; Wanek, Wolfgang; Hofhansl, Florian; Trojan, Daniela; Offre, Pierre; Urich, Tim; Schleper, Christa; Sassmann, Stefan; Kitzler, Barbara; Soja, Gerhard; Hood-Nowotny, Rebecca Clare
2014-01-01
Biochar production and subsequent soil incorporation could provide carbon farming solutions to global climate change and escalating food demand. There is evidence that biochar amendment causes fundamental changes in soil nutrient cycles, often resulting in marked increases in crop production, particularly in acidic and in infertile soils with low soil organic matter contents, although comparable outcomes in temperate soils are variable. We offer insight into the mechanisms underlying these findings by focusing attention on the soil nitrogen (N) cycle, specifically on hitherto unmeasured processes of organic N cycling in arable soils. We here investigated the impacts of biochar addition on soil organic and inorganic N pools and on gross transformation rates of both pools in a biochar field trial on arable land (Chernozem) in Traismauer, Lower Austria. We found that biochar increased total soil organic carbon but decreased the extractable organic C pool and soil nitrate. While gross rates of organic N transformation processes were reduced by 50–80%, gross N mineralization of organic N was not affected. In contrast, biochar promoted soil ammonia-oxidizer populations (bacterial and archaeal nitrifiers) and accelerated gross nitrification rates more than two-fold. Our findings indicate a de-coupling of the soil organic and inorganic N cycles, with a build-up of organic N, and deceleration of inorganic N release from this pool. The results therefore suggest that addition of inorganic fertilizer-N in combination with biochar could compensate for the reduction in organic N mineralization, with plants and microbes drawing on fertilizer-N for growth, in turn fuelling the belowground build-up of organic N. We conclude that combined addition of biochar with fertilizer-N may increase soil organic N in turn enhancing soil carbon sequestration and thereby could play a fundamental role in future soil management strategies. PMID:24497947
3. Grassland Soil Carbon Responses to Nitrogen Additions
Science.gov (United States)
Hofmockel, K. S.; Tfailly, M.; Callister, S.; Bramer, L.; Thompson, A.
2017-12-01
Using a long-term continental scale experiment, we tested if increases in nitrogen (N) inputs augment the accumulation of plant and microbial residues onto mineral soil surfaces. This research investigates N effects on molecular biogeochemistry across six sites from the Nutrient Network (NutNet) experiment. The coupling between concurrently changing carbon (C) and N cycles remains a key uncertainty in understanding feedbacks between the terrestrial C cycle and climate change. Existing models do not consider the full suite of linked C-N processes, particularly belowground, that could drive future C-climate feedbacks. Soil harbors a wealth of diverse organic molecules, most of which have not been measured in hypothesis driven field research. For the first time we systematically assess the chemical composition of soil organic matter (SOM) and functional characteristics of the soil microbiome, to enhance our understanding of the molecular underpinnings of ecosystem C and N cycling. We have acquired soils from 5 ecosystem experiments across the US that have been subjected to 8 years of N addition treatments. These soils have been analyzed for chemical composition to identify how the soil fertility and stability is altered by N fertilization. We found distinct SOM signatures from our field experiments and shifts in soil chemistry in response to 8 years of N fertilization. Across all sites, we found the molecular composition of SOM varied with clay content, supporting the importance of soil mineralogy in the accumulation of specific chemical classes of SOM. While many molecules were common across sites, we discovered a suite of molecules that were site specific. N fertilization had a significant effect on SOM composition. Differences between control and N amended plots were greater in sites rich in lipids and more complex molecules, compared to sites with SOM rich in amino-sugar and protein like substances. Our results have important implications for how SOM is
4. Energy Transformations of Soil Organic Matter in a Changing World
Science.gov (United States)
Herrmann, A. M.; Coucheney, E.; Grice, S. M.; Ritz, K.; Harris, J.
2011-12-01
The role of soils in governing the terrestrial carbon balance is acknowledged as being important but remains poorly understood within the context of climate change. Soils exchange energy with their surroundings and are therefore open systems thermodynamically, but little is known how energy transformations of decomposition processes are affected by temperature. Soil organic matter and the soil biomass can be conceptualised as analogous to the 'fuel' and 'biological engine' of the earth, respectively, and are pivotal in driving the belowground carbon cycle. Thermodynamic principles of soil organic matter decomposition were evaluated by means of isothermal microcalorimetry (TAM Air, TA Instruments, Sollentuna Sweden: (i) Mineral forest soils from the Flakaliden long-term nitrogen fertilisation experiment (Sweden) were amended with a range of different substrates representing structurally simple to complex, ecologically pertinent organic matter and heat signatures were determined at temperatures between 5 and 25°C. (ii) Thermodynamic and resource-use efficiencies of the biomass were determined in arable soils which received contrasting long-term management regimes with respect to organic matter and nitrogen since 1956. The work showed that (i) structurally labile components have higher activation energy and temperature dependence than structurally more complex organic components. This is, however, in contrast to the thermodynamic argument which suggests the opposite that reactions metabolising structurally complex, aromatic components have higher temperature dependence than reactions metabolising structurally more labile components. (ii) Microbial communities exposed to long-term stress by heavy metal and low pH were less thermodynamic efficient and showed a decrease in resource-use efficiency in comparison with conventional input regimes. Differences in efficiencies were mirrored in both the phenotypic and functional profiles of the communities. We will present our
5. Soil warming opens the nitrogen cycle at the alpine treeline.
Science.gov (United States)
Dawes, Melissa A; Schleppi, Patrick; Hättenschwiler, Stephan; Rixen, Christian; Hagedorn, Frank
2017-01-01
Climate warming may alter ecosystem nitrogen (N) cycling by accelerating N transformations in the soil, and changes may be especially pronounced in cold regions characterized by N-poor ecosystems. We investigated N dynamics across the plant-soil continuum during 6 years of experimental soil warming (2007-2012; +4 °C) at a Swiss high-elevation treeline site (Stillberg, Davos; 2180 m a.s.l.) featuring Larix decidua and Pinus uncinata. In the soil, we observed considerable increases in the NH4+ pool size in the first years of warming (by >50%), but this effect declined over time. In contrast, dissolved organic nitrogen (DON) concentrations in soil solutions from the organic layer increased under warming, especially in later years (maximum of +45% in 2012), suggesting enhanced DON leaching from the main rooting zone. Throughout the experimental period, foliar N concentrations showed species-specific but small warming effects, whereas δ 15 N values showed a sustained increase in warmed plots that was consistent for all species analysed. The estimated total plant N pool size at the end of the study was greater (+17%) in warmed plots with Pinus but not in those containing Larix, with responses driven by trees. Irrespective of plot tree species identity, warming led to an enhanced N pool size of Vaccinium dwarf shrubs, no change in that of Empetrum hermaphroditum (dwarf shrub) and forbs, and a reduction in that of grasses, nonvascular plants, and fine roots. In combination, higher foliar δ 15 N values and the transient response in soil inorganic N indicate a persistent increase in plant-available N and greater cumulative plant N uptake in warmer soils. Overall, greater N availability and increased DON concentrations suggest an opening of the N cycle with global warming, which might contribute to growth stimulation of some plant species while simultaneously leading to greater N losses from treeline ecosystems and possibly other cold biomes. © 2016 John Wiley & Sons
6. Mapping soil total nitrogen of cultivated land at county scale by using hyperspectral image
Science.gov (United States)
Gu, Xiaohe; Zhang, Li Yan; Shu, Meiyan; Yang, Guijun
2018-02-01
Monitoring total nitrogen content (TNC) in the soil of cultivated land quantitively and mastering its spatial distribution are helpful for crop growing, soil fertility adjustment and sustainable development of agriculture. The study aimed to develop a universal method to map total nitrogen content in soil of cultivated land by HSI image at county scale. Several mathematical transformations were used to improve the expression ability of HSI image. The correlations between soil TNC and the reflectivity and its mathematical transformations were analyzed. Then the susceptible bands and its transformations were screened to develop the optimizing model of map soil TNC in the Anping County based on the method of multiple linear regression. Results showed that the bands of 14th, 16th, 19th, 37th and 60th with different mathematical transformations were screened as susceptible bands. Differential transformation was helpful for reducing the noise interference to the diagnosis ability of the target spectrum. The determination coefficient of the first order differential of logarithmic transformation was biggest (0.505), while the RMSE was lowest. The study confirmed the first order differential of logarithm transformation as the optimal inversion model for soil TNC, which was used to map soil TNC of cultivated land in the study area.
7. Nitrogen Transformation and Microbial Spatial Distribution in Drinking Water Biofilter
Science.gov (United States)
Qian, Yongxing; Zhang, Huining; Jin, Huizheng; Wu, Chengxia
2018-02-01
Well understanding the rule of nitrogen mutual transformation in biofilters is important for controlling the DBPs formation in the subsequent disinfection process. Ammonia nitrogen removal effect and nitrogen transformation approach in biofilter of drinking water was researched in the study. The biofilter removed ammonia of 48.5% and total phosphorus of 72.3%. And the removal rate of TN, NO3 --N, DON were 37.1%, 33.1%, 46.9%, respectively. Biomass and bioactivity of different depth of the biofilter were determined, too. The overall distribution of biomass showed a decreasing trend from top to bottom. The bioactivity in lower layer gradually increased. Especially the bioactivity of heterotrophic microorganisms showed a gradual increase trend. The amount of the nitrogen loss was 3.06mg/L. Non-nitrification pathway of “nitrogen loss” phenomenon in biofilter might exist assimilation, nitrification and denitrification in autotrophic.
8. Modelling Nitrogen Transformation in Horizontal Subsurface Flow ...
African Journals Online (AJOL)
A mathematical model was developed to permit dynamic simulation of nitrogen interaction in a pilot horizontal subsurface flow constructed wetland receiving effluents from primary facultative pond. The system was planted with Phragmites mauritianus, which was provided with root zone depth of 75 cm. The root zone was ...
9. Nitrogen cycling in a flooded-soil ecosystem planted to rice (Oryza sativa L.)
International Nuclear Information System (INIS)
Reddy, K.R.
1982-01-01
15 N studies of various aspects of the nitrogen cycle in a flooded rice ecosystem on Crowley silt loam soil in Louisiana were reviewed to construct a mass balance model of the nitrogen cycle for this system. Nitrogen transformations modeled included 1) net ammonification (0.22 mg NH 4+ -N kg dry soil - 1 day - 1 ). 2) net nitrification (207 mg NO 3- -N kg dry soil - 1 day - 1 ). 3) denitrification (0.37 mg N kg dry soil - 1 day - 1 ), and 4) biological N 2 fixation (0.16 mg N kg dry soil - 1 day - 1 ). Nitrogen inputs included 1) application of fertilizers, 2) incorporation of crop residues, 3) biological N 2 fixation, and 4) deposition. Nitrogen outputs included 1) crop removal, 2) gaseous losses from NH 3 volatilization and simultaneous occurrence of nitrification-denitrification, and 3) leaching and runoff. Mass balance calculations indicated that 33% of the available inorganic nitrogen was recovered by rice, and the remaining nitrogen was lost from the system. Losses of N due to ammonia volatilization were minimal because fertilizer-N was incorporated into the soil. A significant portion of inorganic-N was lost by ammonium diffusion from the anaerobic layer to the aerobic layer in response to a concentration gradient and subsequent nitrification in the aerobic layer followed by nitrate diffusion into the anaerobic layer and denitrification into gaseous end products. Leaching and surface runoff losses were minimal. (orig.)
10. Acidification and Nitrogen Eutrophication of Austrian Forest Soils
Directory of Open Access Journals (Sweden)
Robert Jandl
2012-01-01
Full Text Available We evaluated the effect of acidic deposition and nitrogen on Austrian forests soils. Until thirty years ago air pollution had led to soil acidification, and concerns on the future productivity of forests were raised. Elevated rates of nitrogen deposition were believed to cause nitrate leaching and imbalanced forest nutrition. We used data from a soil monitoring network to evaluate the trends and current status of the pH and the C : N ratio of Austrian forest soils. Deposition measurements and nitrogen contents of Norway spruce needles and mosses were used to assess the nitrogen supply. The pH values of soils have increased because of decreasing proton depositions caused by reduction of emissions. The C : N ratio of Austrian forest soils is widening. Despite high nitrogen deposition rates the increase in forest stand density and productivity has increased the nitrogen demand. The Austrian Bioindicator Grid shows that forest ecosystems are still deficient in nitrogen. Soils retain nitrogen efficiently, and nitrate leaching into the groundwater is presently not a large-scale problem. The decline of soil acidity and the deposition of nitrogen together with climate change effects will further increase the productivity of the forests until a limiting factor such as water scarcity becomes effective.
11. Quantification Of {sup 1}5{sup N} Internal Transformation To Assess Nitrogen Supply Capacity In Deforested Soil; Kuantifikasi Transformasi Internal {sup 5N} ntuk Memprediksi Daya Suplai Nitrogen Pada Lahan Paska Deforestasi
Energy Technology Data Exchange (ETDEWEB)
Handayani, I P; Prawito, P [Bengkulu University, Bengkulu (Indonesia); Sisworo, E L [Center for Research and Development of Isotopes and Radiation Technology, National Nuclear Energy Agency, Jakarta (Indonesia)
2002-07-01
Quantification of deforested soil's capacity to supply available N via mineralization and immobilization using {sup 15N} pool dilution is crucial to make fertilizer recommendation. The objective of this research was to measure the soil's capacity to minemlize and ilmnobilize N, so that the actual value of available N released by soil can be predicted. The results showed that Imperata grassland released the highest available N (amonium + nitrate) about 33.93 mg/kg/d and can immobilize 11.68 mg/kg/d of N. On the other hand, agriculture lields had the lowest inorganic N by nearly 23.15 mg/kg/d, and no immobilization occurred. The implication is that agriculture fields have a very low labile and stabile pool N (nearly 0), while Imperata grassland have capacity to store more pool N into labile or stabil pool (about 34%). In conclusion, dynamics of N cycling in ecosystem are dependent upon the content of pool C-N utilized by microorganisms and plants.
12. EFFECT OF BLUE GREEN ALGAE ON SOIL NITROGEN
African Journals Online (AJOL)
2012-07-31
Jul 31, 2012 ... associated with soil dessication at the end of the cultivation cycle and algal growth ... blue-green algae (BGA) on soil nitrogen was carried out from June to December 2005. .... Nitrogen fixation by free living Micro-organisms.
13. Fourier transform infrared spectroscopic study of intact cells of the nitrogen-fixing bacterium Azospirillum brasilense
Science.gov (United States)
Kamnev, A. A.; Ristić, M.; Antonyuk, L. P.; Chernyshev, A. V.; Ignatov, V. V.
1997-06-01
The data of Fourier transform infrared (FTIR) spectroscopic measurements performed on intact cells of the soil nitrogen-fixing bacterium Azospirillum brasilense grown in a standard medium and under the conditions of an increased metal uptake are compared and discussed. The structural FTIR information obtained is considered together with atomic absorption spectrometry (AAS) data on the content of metal cations in the bacterial cells. Some methodological aspects concerning preparation of bacterial cell samples for FTIR measurements are also discussed.
14. Isotope studies on soil and fertilizer nitrogen
International Nuclear Information System (INIS)
Olson, R.A.
1979-01-01
Reductions in isotope cost in the 1960s and equipment innovations, have extended compared to 1940, the research of soil and plant scientists so that 15 N is now an indispensable tool when working with N. Leadership of FAO/IAEA coordinated research programmes and the Nitrogen Laboratory of the Tennessee Valley Authority helped greatly in bringing about this expanded usage. Recognized isotope effects are of insufficient magnitude to invalidate tracer measurements of field crop uptake in the treatment year if enrichment of 0.3 at.% excess 15 N or greater is employed. Thus, use of 15 N depleted tracer with potential of 0.366% 15 N differential from the standard isotope ratio of N in air is feasible. Its manufacture has allowed further economy in the isotope tag and ultimate treatment of field-scale plots. Interest in Δ 15 N measurements for predicting the NO - 3 contaminant source in surface and ground waters has depreciated. Variations in natural isotope ratio of soil N commonly exceed the differences in Δ 15 N values of the presumed source materials. 15 N provides the only correct measure of fertilizer N utilization efficiency. The field study examples of irrigated maize demonstrate that little or no fertilizer N is likely to escape the root zone where the rate applied does not exceed that required for maximum yield; also, that light and frequent irrigations afford higher yields than heavier, less frequent irrigations. Delaying fertilizer N applications until the crop is well established affords not only higher yields, but greater residual fertilizer N for future crops. Measured effective root activity for absorbing NO - 3 has been invaluable in estimating fertilizer requirements of a crop in relation to residual mineral N in soil at planting and projecting the depth at which the NO - 3 becomes an environmental hazard. The tag likewise is indispensable in determining symbiotic N fixation
15. [Nitrogen Fraction Distributions and Impacts on Soil Nitrogen Mineralization in Different Vegetation Restorations of Karst Rocky Desertification].
Science.gov (United States)
Hu, Ning; Ma, Zhi-min; Lan, Jia-cheng; Wu, Yu-chun; Chen, Gao-qi; Fu, Wa-li; Wen, Zhi-lin; Wang, Wen-jing
2015-09-01
In order to illuminate the impact on soil nitrogen accumulation and supply in karst rocky desertification area, the distribution characteristics of soil nitrogen pool for each class of soil aggregates and the relationship between aggregates nitrogen pool and soil nitrogen mineralization were analyzed in this study. The results showed that the content of total nitrogen, light fraction nitrogen, available nitrogen and mineral nitrogen in soil aggregates had an increasing tendency along with the descending of aggregate-size, and the highest content was occurred in 5mm and 2-5 mm classes, and the others were the smallest. With the positive vegetation succession, the weight percentage of > 5 mm aggregate-size classes was improved and the nitrogen storage of macro-aggregates also was increased. Accordingly, the capacity of soil supply mineral nitrogen and storage organic nitrogen were intensified.
16. Estimating Soil Bulk Density and Total Nitrogen from Catchment ...
African Journals Online (AJOL)
Even though data on soil bulk density (BD) and total nitrogen (TN) are essential for planning modern farming techniques, their data availability is limited for many applications in the developing word. This study is designed to estimate BD and TN from soil properties, land-use systems, soil types and landforms in the ...
17. Mineralization of Nitrogen in Hydromorphic Soils Amended with ...
African Journals Online (AJOL)
... to 320.00 mg kg-1 for Mangrove soil (mangal acid sulphate soils). The order of cumulative nitrogen released in the waste amended soil followed the order: sewage sludge>kitchen waste> poultry manure> oil palm waste> cow manure. Total mineralized N indicated negative correlation with total organic N and C:N ratio ...
18. Patterns and controls on nitrogen cycling of biological soil crusts
Science.gov (United States)
Barger, Nichole N.; Zaady, Eli; Weber, Bettina; Garcia-Pichel, Ferran; Belnap, Jayne
2016-01-01
Biocrusts play a significant role in the nitrogen [N ] cycle within arid and semi-arid ecosystems, as they contribute major N inputs via biological fixation and dust capture, harbor internal N transformation processes, and direct N losses via N dissolved, gaseous and erosional loss processes (Fig. 1). Because soil N availability in arid and semi-arid ecosystems is generally low and may limit net primary production (NPP), especially during periods when adequate water is available, understanding the mechanisms and controls of N input and loss pathways in biocrusts is critically important to our broader understanding of N cycling in dryland environments. In particular, N cycling by biocrusts likely regulates short-term soil N availability to support vascular plant growth, as well as long-term N accumulation and maintenance of soil fertility. In this chapter, we review the influence of biocrust nutrient input, internal cycling, and loss pathways across a range of biomes. We examine linkages between N fixation capabilities of biocrust organisms and spatio-temporal patterns of soil N availability that may influence the longer-term productivity of dryland ecosystems. Lastly, biocrust influence on N loss pathways such as N gas loss, leakage of N compounds from biocrusts, and transfer in wind and water erosion are important to understand the maintenance of dryland soil fertility over longer time scales. Although great strides have been made in understanding the influence of biocrusts on ecosystem N cycling, there are important knowledge gaps in our understanding of the influence of biocrusts on ecosystem N cycling that should be the focus of future studies. Because work on the interaction of N cycling and biocrusts was reviewed in Belnap and Lange (2003), this chapter will focus primarily on research findings that have emerged over the last 15 years (2000-2015).
19. 15N isotopic techniques to study nitrogen cycle in soil-plant-atmosphere system
International Nuclear Information System (INIS)
Kumar, Manoj; Chandrakala, J.U.; Sachdev, M.S.; Sachdev, P.
2009-01-01
Intensification of agriculture to meet the increasing food demand has caused severe disruption in natural balance of global as well as regional nitrogen cycle, potentially threatening the future sustainability of agriculture and environment of the total fertilizer nitrogen used in agriculture globally, only less than half is recovered by crop plants, rest is lost to the environment, resulting in several environmental problems such as ground water pollution and global warming, besides huge economic loss of this costly input in agriculture. Improving fertilizer nitrogen use efficiency and minimising N loss to the environment is the key to regain the lost control of nitrogen cycle in agriculture. Fertilizer nitrogen use efficiency depends largely on N requirement of crops, N supply from soil and fertilizer through N transformations in soil, and N losses from the soil-water-plant system. 15 N isotopic techniques have the potential to provide accurate measurement quantification of different processes involved in N cycle such as fixation of atmospheric N 2 , transformations- mineralization and immobilization- of soil and fertilizer N which governs N supply to plants, and N losses to the environment through ammonia volatilization, denitrification and nitrate leaching. 15 N tracers can also give precise identification of ways and sources of N loss from agriculture. These information can be used to develop strategies for increasing fertilizer N use efficiency and minimizing the loss of this costly input from agriculture to environment, which in turn will help to achieve the tripartite goal of food security, agricultural profitability and environmental quality. (author)
20. Study of some nitrogen transformation reactions as influenced by the agrochemicals in some soils of north Iraq by using labelled compounds. Part of a coordinated programme on isotopic-tracer-aided studies of agrochemical residue - soil biota interactions
International Nuclear Information System (INIS)
Shali, K.G.
1982-06-01
The effect is described of different pesticides when applied to autoclaved soils to which the mixture of nitrifier, ammonifier, and azotobacter were added and incubated for 90 days. The results are given of the respiration parameter of 14 CO 2 evolved at 30 and 60 days of incubation from soil samples obtained at depths of 15, 30, 45, and 60 cm. Graphs show the survival of mixture of nitrifier, ammonifier, and azotobacter treated with pesticides Benlate, Sevin, and Diptrex at three dose levels. Total bacterial counts as estimated by 14 C-glucose oxidation are also shown
1. [Retaining and transformation of incoming soil N from highland to adjacent terrestrial water body in riparian buffer zone].
Science.gov (United States)
Wang, Qing-cheng; Yu, Hong-li; Yao, Qin; Han, Zhuang-xing; Qiao, Shu-liang
2007-11-01
Highland soil nitrogen can enter adjacent water body via erosion and leaching, being one of the important pollutants in terrestrial water bodies. Riparian buffer zone is a transitional zone between highland and its adjacent water body, and a healthy riparian buffer zone can retain and transform the incoming soil N through physical, biological, and biochemical processes. In this paper, the major pathways through which soil nitrogen enters terrestrial water body and the mechanisms the nitrogen was retained and transformed in riparian buffer zone were introduced systematically, and the factors governing the nitrogen retaining and transformation were analyzed from the aspects of hydrological processes, soil characters, vegetation features, and human activities. The problems existing in riparian buffer zone study were discussed, and some suggestions for the further study in China were presented.
2. Organic carbon, nitrogen and phosphorus contents of some tea soils
International Nuclear Information System (INIS)
Ahmed, M.S.; Zamir, M.R.; Sanauallah, A.F.M.
2005-01-01
Soil samples were collected from Rungicherra Tea-Estate of Moulvibazar district, Bangladesh. Organic carbon, organic matter, total nitrogen and available phosphorus content of the collected soil of different topographic positions have been determined. The experimental data have been analyzed statistically and plotted against topography and soil depth. Organic carbon and organic matter content varied from 0.79 to 1.24% and 1.37 to 2.14%. respectively. Total nitrogen and available phosphorus content of these soils varied respectively from 0.095 to 0.13% and 2.31 to 4.02 ppm. (author)
3. Contribution of bacterial cell nitrogen to soil humic fractions
International Nuclear Information System (INIS)
Knowles, R.; Barro, L.
1981-01-01
Living cells of Serratia marcescens, uniformly labelled with 15 N, were added to samples of maple (Acer saccharum) and black spruce (Picea mariana) forest soils. After different periods of incubation from zero time to 100 days, the soils were subjected to alkali-acid and phenol extraction to provide humic acid, fulvic acid, humin and 'humoprotein' fractions. Significant amounts of the cell nitrogen were recovered in the humic and fulvic acids immediately after addition. After incubation, less cell nitrogen appeared in the humic acid and more in the fulvic acid. The amount of cell nitrogen recovered in the humin fraction increased with incubation. Roughly 5 to 10 per cent of the added cell nitrogen was found as amino acid nitrogen from humoprotein in a phenol extract of the humic acid. The data are consistent with the occurrence of co-precipitation of biologically labile biomass nitrogen compounds with humic polymers during the alkaline extraction procedure involved in the humic-fulvic fractionation. (orig.)
4. Climate change induces shifts in abundance and activity pattern of bacteria and archaea catalyzing major transformation steps in nitrogen turnover in a soil from a mid-European beech forest.
Science.gov (United States)
Gschwendtner, Silvia; Tejedor, Javier; Bimüller, Carolin; Bimueller, Carolin; Dannenmann, Michael; Kögel-Knabner, Ingrid; Knabner, Ingrid Kögel; Schloter, Michael
2014-01-01
Ongoing climate change will lead to more extreme weather events, including severe drought periods and intense drying rewetting cycles. This will directly influence microbial nitrogen (N) turnover rates in soil by changing the water content and the oxygen partial pressure. Therefore, a space for time climate change experiment was conducted by transferring intact beech seedling-soil mesocosms from a northwest (NW) exposed site, representing today's climatic conditions, to a southwest (SW) exposed site, providing a model climate for future conditions with naturally occurring increased soil temperature (+0.8°C in average). In addition, severe drought and intense rainfall was simulated by a rainout shelter at SW and manual rewetting after 39 days drought, respectively. Soil samples were taken in June, at the end of the drought period (August), 24 and 72 hours after rewetting (August) and after a regeneration period of four weeks (September). To follow dynamics of bacterial and archaeal communities involved in N turnover, abundance and activity of nitrifiers, denitrifiers, N2-fixing microbes and N-mineralizers was analyzed based on marker genes and the related transcripts by qPCR from DNA and RNA directly extracted from soil. Abundance of the transcripts was reduced under climate change with most pronounced effects for denitrification. Our results revealed that already a transfer from NW to SW without further treatment resulted in decreased cnor and nosZ transcripts, encoding for nitric oxide reductase and nitrous oxide reductase, respectively, while nirK transcripts, encoding for nitrite reductase, remained unaffected. Severe drought additionally led to reduced nirK and cnor transcripts at SW. After rewetting, nirK transcripts increased rapidly at both sites, while cnor and nosZ transcripts increased only at NW. Our data indicate that the climate change influences activity pattern of microbial communities involved in denitrification processes to a different extend
5. Adjustment of nitrogen fertilization to the needs of plants and limitations posed by the risk of nitrate accumulation and pollution of the soil and subsoil
Energy Technology Data Exchange (ETDEWEB)
Muller, J C
1980-01-01
In chalky Champagne, nitrogen balance is study to adjust availability to plant response. For this, it is necessary to know some parameters whose measurement is obtained progressively; plants exportation, nitrogen transformations in terms of transport processes in soil system, kinetic of mineralization of soil organic nitrogen, plants residus and agricultural waste waters. Lysimeters with rotation of Champagne (wheat, sugarbeet, potatoes...) are used to measure losses of nitrogen and follow transport of nitrates by mean of soil solution captors. Comparisons with field results, lysimeters results and laboratory experimentations are used to adjust an experimental model. Two examples show: 1) Nitrogen fertilizer requirement for wheat. 2) Possibility of maximum application for agricultural waste waters.
6. Abiotic versus biotic controls on soil nitrogen cycling in drylands along a 3200 km transect
Science.gov (United States)
Liu, Dongwei; Zhu, Weixing; Wang, Xiaobo; Pan, Yuepeng; Wang, Chao; Xi, Dan; Bai, Edith; Wang, Yuesi; Han, Xingguo; Fang, Yunting
2017-03-01
Nitrogen (N) cycling in drylands under changing climate is not well understood. Our understanding of N cycling over larger scales to date relies heavily on the measurement of bulk soil N, and the information about internal soil N transformations remains limited. The 15N natural abundance (δ15N) of ammonium and nitrate can serve as a proxy record for the N processes in soils. To better understand the patterns and mechanisms of N cycling in drylands, we collected soils along a 3200 km transect at about 100 km intervals in northern China, with mean annual precipitation (MAP) ranging from 36 to 436 mm. We analyzed N pools and δ15N of ammonium, dual isotopes (15N and 18O) of nitrate, and the microbial gene abundance associated with soil N transformations. We found that N status and its driving factors were different above and below a MAP threshold of 100 mm. In the arid zone with MAP below 100 mm, soil inorganic N accumulated, with a large fraction being of atmospheric origin, and ammonia volatilization was strong in soils with high pH. In addition, the abundance of microbial genes associated with soil N transformations was low. In the semiarid zone with MAP above 100 mm, soil inorganic N concentrations were low and were controlled mainly by biological processes (e.g., plant uptake and denitrification). The preference for soil ammonium over nitrate by the dominant plant species may enhance the possibility of soil nitrate losses via denitrification. Overall, our study suggests that a shift from abiotic to biotic controls on soil N biogeochemistry under global climate changes would greatly affect N losses, soil N availability, and other N transformation processes in these drylands in China.
7. Differences in nitrogen cycling and soil mineralisation between a ...
African Journals Online (AJOL)
Differences in nitrogen cycling and soil mineralisation between a eucalypt plantation and a mixed eucalypt and Acacia mangium plantation on a sandy tropical soil. ... An ecological intensification of eucalypt plantations was tested with the replacement of half of the Eucalyptus urophylla × E. grandis by Acacia mangium in the ...
8. Moss-nitrogen input to boreal forest soils
DEFF Research Database (Denmark)
Rousk, Kathrin; Jones, Davey; DeLuca, Thomas
2014-01-01
Cyanobacteria living epiphytically on mosses in pristine, unpolluted areas fix substantial amounts of atmospheric nitrogen (N) and therefore represent a primary source of N in N-limited boreal forests. However, the fate of this N is unclear, in particular, how the fixed N2 enters the soil and bec...... and that transfer of N to the soil is not facilitated by fungal hyphae....
9. Transformation of nitrogen and distribution of nitrogen-related bacteria in a polluted urban stream.
Science.gov (United States)
Jiao, Y; Jin, W B; Zhao, Q L; Zhang, G D; Yan, Y; Wan, J
2009-01-01
Most researchers focused on either nitrogen species or microbial community for polluted urban stream while ignoring the interaction between them and its effect on nitrogen transformation, which restricted the rational selection of an effective and feasible remediation technology. Taking Buji stream in Shenzhen (China) as target stream, the distribution of nitrogen-related bacteria was investigated by most probable number (MPN) besides analysis of nitrogen species etc. The nitrogen-related bacteria in sediment were 10(2) times richer than those in water. Owing to their faster growth, the MPN of ammonifying bacteria and denitrifying bacteria were 10(5) and 10(2) times higher than those of nitrifying bacteria, respectively. The ammonifying bacteria numbers were significantly related to BOD5 in water, while nitrifying bacteria in sediment correlated well with nitrate in water. Thus, nitrification occurred mainly in sediment surface and was limited by low proportion of nitrifying bacteria. The denitrifying bacteria in sediment had good relationship with BOD5 and nitrite and nitrate in water. Low DO and rich organic compounds were beneficial to denitrification but unfavourable to nitrification. Denitrification was restricted by low nitrite and nitrate concentration. These results could be served as a reference for implementing the remediation scheme of nitrogen polluted urban stream.
10. Nitrogen dynamics in a soil-sugar cane system
International Nuclear Information System (INIS)
Oliveira, Julio Cesar Martins de; Reichardt, Klaus; Bacchi, Osny O.S.; Timm, Luis Carlos; Tominaga, Tania Toyomi; Castro Navarro, Roberta de; Cassaro, Fabio Augusto Meira; Dourado-Neto, Durval; Trivelin, Paulo Cesar Ocheuse; Piccolo, Marisa de Cassia
2000-01-01
Results of an organic matter management experiment of a sugar cane crop are reported for the first cropping year. Sugar cane was planted in October 1997, and labeled with a 15 N fertilizer pulse to study the fate of organic matter in the soil-plant system. A nitrogen balance is presented, partitioning the system in plant components (stalk, tip and straw), soil components (five soil organic matter fractions) and evaluating leaching losses. The 15 N label permitted to determine, at the end of the growing season, amounts of nitrogen derived from the fertilizer, present in the above mentioned compartments. (author)
11. Climate response of the soil nitrogen cycle in three forest types of a headwater Mediterranean catchment
Science.gov (United States)
Lupon, Anna; Gerber, Stefan; Sabater, Francesc; Bernal, Susana
2015-05-01
Future changes in climate may affect soil nitrogen (N) transformations, and consequently, plant nutrition and N losses from terrestrial to stream ecosystems. We investigated the response of soil N cycling to changes in soil moisture, soil temperature, and precipitation across three Mediterranean forest types (evergreen oak, beech, and riparian) by fusing a simple process-based model (which included climate modifiers for key soil N processes) with measurements of soil organic N content, mineralization, nitrification, and concentration of ammonium and nitrate. The model describes sources (atmospheric deposition and net N mineralization) and sinks (plant uptake and hydrological losses) of inorganic N from and to the 0-10 cm soil pool as well as net nitrification. For the three forest types, the model successfully recreated the magnitude and temporal pattern of soil N processes and N concentrations (Nash-Sutcliffe coefficient = 0.49-0.96). Changes in soil water availability drove net N mineralization and net nitrification at the oak and beech forests, while temperature and precipitation were the strongest climatic factors for riparian soil N processes. In most cases, net N mineralization and net nitrification showed a different sensitivity to climatic drivers (temperature, soil moisture, and precipitation). Our model suggests that future climate change may have a minimal effect on the soil N cycle of these forests (warming and negative drying effects on the soil N cycle may counterbalance each other.
12. Organic nitrogen components in soils from southeast China*
Science.gov (United States)
Chen, Xian-you; Wu, Liang-huan; Cao, Xiao-chuang; Zhu, Yuan-hong
2013-01-01
Objective: To investigate the amounts of extractable organic nitrogen (EON), and the relationships between EON and total extractable nitrogen (TEN), especially the amino acids (AAs) adsorbed by soils, and a series of other hydrolyzed soil nitrogen indices in typical land use soil types from southeast China. Under traditional agricultural planting conditions, the functions of EON, especially AAs in the rhizosphere and in bulk soil zones were also investigated. Methods: Pot experiments were conducted using plants of pakchoi (Brassica chinensis L.) and rice (Oryza sativa L.). In the rhizosphere and bulk soil zone studies, organic nitrogen components were extracted with either distilled water, 0.5 mol/L K2SO4 or acid hydrolysis. Results: K2SO4-EON constituted more than 30% of TEN pools. K2SO4-extractable AAs accounted for 25% of EON pools and nearly 10% of TEN pools in rhizosphere soils. Overall, both K2SO4-EON and extractable AAs contents had positive correlations with TEN pools. Conclusions: EON represented a major component of TEN pools in garden and paddy soils under traditional planting conditions. Although only a small proportion of the EON was present in the form of water-extractable and K2SO4-extractable AAs, the release of AAs from soil exchangeable sites might be an important source of organic nitrogen (N) for plant growth. Our findings suggest that the content of most organic forms of N was significantly greater in rhizosphere than in bulk soil zone samples. However, it was also apparent that the TEN pool content was lower in rhizosphere than in bulk soil samples without added N. PMID:23549843
13. Effects of vegetation type on microbial biomass carbon and nitrogen in subalpine mountain forest soils.
Science.gov (United States)
Ravindran, Anita; Yang, Shang-Shyng
2015-08-01
Microbial biomass plays an important role in nutrient transformation and conservation of forest and grassland ecosystems. The objective of this study was to determine the microbial biomass among three vegetation types in subalpine mountain forest soils of Taiwan. Tatachia is a typical high-altitude subalpine temperate forest ecosystem in Taiwan with an elevation of 1800-3952 m and consists of three vegetation types: spruce, hemlock, and grassland. Three plots were selected in each vegetation type. Soil samples were collected from the organic layer, topsoil, and subsoil. Microbial biomass carbon (Cmic) was determined by the chloroform fumigation-extraction method, and microbial biomass nitrogen (Nmic) was determined from the total nitrogen (Ntot) released during fumigation-extraction. Bacteria, actinomycetes, fungi, cellulolytic microbes, phosphate-solubilizing microbes, and nitrogen-fixing microbes were also counted. The Cmic and Nmic were highest in the surface soil and declined with the soil depth. These were also highest in spruce soils, followed by in hemlock soils, and were lowest in grassland soils. Cmic and Nmic had the highest values in the spring season and the lowest values in the winter season. Cmic and Nmic had significantly positive correlations with total organic carbon (Corg) and Ntot. Contributions of Cmic and Nmic, respectively, to Corg and Ntot indicated that the microbial biomass was immobilized more in spruce and hemlock soils than in grassland soils. Microbial populations of the tested vegetation types decreased with increasing soil depth. Cmic and Nmic were high in the organic layer and decreased with the depth of layers. These values were higher for spruce and hemlock soils than for grassland soils. Positive correlations were observed between Cmic and Nmic and between Corg and Ntot. Copyright © 2014. Published by Elsevier B.V.
14. Microbial Biofertilizer Decreases Nicotine Content by Improving Soil Nitrogen Supply.
Science.gov (United States)
Shang, Cui; Chen, Anwei; Chen, Guiqiu; Li, Huanke; Guan, Song; He, Jianmin
2017-01-01
Biofertilizers have been widely used in many countries for their benefit to soil biological and physicochemical properties. A new microbial biofertilizer containing Phanerochaete chrysosporium and Bacillus thuringiensis was prepared to decrease nicotine content in tobacco leaves by regulating soil nitrogen supply. Soil NO 3 - -N, NH 4 + -N, nitrogen supply-related enzyme activities, and nitrogen accumulation in plant leaves throughout the growing period were investigated to explore the mechanism of nicotine reduction. The experimental results indicated that biofertilizer can reduce the nicotine content in tobacco leaves, with a maximum decrement of 16-18 % in mature upper leaves. In the meantime, the total nitrogen in mature lower and middle leaves increased with the application of biofertilizer, while an opposite result was observed in upper leaves. Protein concentration in leaves had similar fluctuation to that of total nitrogen in response to biofertilizer. NO 3 - -N content and nitrate reductase activity in biofertilizer-amended soil increased by 92.3 and 42.2 %, respectively, compared to those in the control, whereas the NH 4 + -N and urease activity decreased by 37.8 and 29.3 %, respectively. Nitrogen uptake was improved in the early growing stage, but this phenomenon was not observed during the late growth period. Nicotine decrease is attributing to the adjustment of biofertilizer in soil nitrogen supply and its uptake in tobacco, which result in changes of nitrogen content as well as its distribution in tobacco leaves. The application of biofertilizer containing P. chrysosporium and B. thuringiensis can reduce the nicotine content and improve tobacco quality, which may provide some useful information for tobacco cultivation.
15. Translocation of labelled fertilizer nitrogen in soil columns
International Nuclear Information System (INIS)
Haunold, E.; Zvara, J.
1975-01-01
The translocation of 15 labeled ammonium and nitrate fertilizer was studied under normal weather conditions for two years in columns filled with different soils. At the end of the experimental period, which usually lasted for 9 months, between 5.9-10.3% of the ammonium fertilizer was leached out, 33.7-50.1% remained in the soil and 39.5-59.7% was lost as gas. For nitrate nitrogen the figures were: 22.6-47.3% leached out, 16.7-40% remaining in the soil, 12.7-60.0% lost as gas. The ammonium fertilizer moving through the soil interchanged with 1-13% of the soil nitrogen, the nitrate fertilizer with only 0.5-2%
16. Transformations of Nitrogen from Secondary Treated Wastewater when Infiltrated in Managed Aquifer Recharge Schemes
Science.gov (United States)
Silver, Matthew; Wefer-Roehl, Annette; Kübeck, Christine; Schüth, Christoph
2016-04-01
The EU FP7 project MARSOL seeks to address water scarcity challenges in arid regions, where managed aquifer recharge (MAR) is an upcoming technology to recharge depleted aquifers using alternative water sources. Within this framework, we conduct column experiments to investigate transformations of nitrogen species when secondary treated wastewater (STWW) is infiltrated through two natural soils being considered for managed aquifer recharge. The soils vary considerably in organic matter content, with total organic matter determined by loss on ignition of 6.8 and 2.9 percent by mass for Soil 1 and Soil 2, respectively. Ammonium (NH4+) concentrations as high as 8.6 mg/L have been measured in pore water samples from Soil #1, indicating that ammonium could be a contaminant of concern in MAR applications using STWW, with consideration of the EU limit of 0.5 mg/L for NH4+. The two forms of nitrogen with the highest concentrations in the secondary treated wastewater are nitrate (NO3-) and dissolved organic nitrogen (DON). In water samples taken from the soil columns, a mass balance of measured ions shows a deficit of nitrogen in ionic form in the upper to middle depths of the soil, suggesting the presence of unmeasured species. These are likely nitrous oxide or dinitrogen gas, which would signify that denitrification is occurring. Measurements of N2O from water samples will verify its presence and spatial variation. The ammonium concentrations increase slowly in the upper parts of the soil but then increase more sharply at greater depth, after NO3- is depleted, suggesting that DON is the source of the produced NH4+. The production of NH4+ is presumed to be facilitated microbiologically. It is hypothesized that at higher organic carbon to total nitrogen (C:N) ratios, more NH4+ will be formed. To test this, in the experiments with Soil #2, three different inflow waters are used, listed in order of decreasing C:N ratio: STWW, STWW with NO3- added to a concentration of 80 mg
17. Soil emissions of gaseous reactive nitrogen from North American arid lands: an overlooked source.
Science.gov (United States)
Sparks, J. P.; McCalley, C. K.; Strahm, B. D.
2008-12-01
The biosphere-atmosphere exchange and transformation of nitrogen has important ramifications for both terrestrial biogeochemistry and atmospheric chemistry. Several important mechanisms within this process (e.g., photochemistry, nitrogen deposition, aerosol formation) are strongly influenced by the emission of reactive nitrogen compounds from the Earth's surface. Therefore, a quantification of emission sources is a high priority for future conceptual understanding. One source largely overlooked in most global treatments are the soil emissions from arid and semi-arid landscapes worldwide. Approximately 35-40% of global terrestrial land cover is aridland and emission of reactive nitrogen from soils in these regions has the potential to strongly influence both regional and global biogeochemistry. Here we present estimates of soil emission of oxidized (NO, total NOy including NO2 and HONO) and reduced (NH3) forms of reactive nitrogen from two North American arid regions: the Mojave Desert and the Colorado Plateau. Soil fluxes in these regions are highly dependent on soil moisture conditions. Soil moisture is largely driven by pulsed rain events with fluxes increasing 20-40 fold after a rain event. Using field measurements made across seasons under an array of moisture conditions, precipitation records, and spatially explicit cover type information we have estimated annual estimates for the Mojave Desert (1.5 ± 0.7 g N ha-1 yr-1), the shale derived (1.4 ± 0.9 g N ha-1 yr-1), and sandy soil derived (2.8 ± 1.2 g N ha-1 yr-1) regions of the Colorado Plateau. The chemical composition of soil emissions varies significantly both with season and soil moisture content. Emissions from dry soils tend to be dominated by ammonia and forms of NOy other than NO. In contrast, NO becomes a dominant portion of the flux post rain events (~30% of the total flux). This variability in chemical form has significant implications for the tropospheric fate of the emitted N. NO and other
18. Modelling nitrogen saturation and carbon accumulation in heathland soils under elevated nitrogen deposition
International Nuclear Information System (INIS)
Evans, C.D.; Caporn, S.J.M.; Carroll, J.A.; Pilkington, M.G.; Wilson, D.B.; Ray, N.; Cresswell, N.
2006-01-01
A simple model of nitrogen (N) saturation, based on an extension of the biogeochemical model MAGIC, has been tested at two long-running heathland N manipulation experiments. The model simulates N immobilisation as a function of organic soil C/N ratio, but permits a proportion of immobilised N to be accompanied by accumulation of soil carbon (C), slowing the rate of C/N ratio change and subsequent N saturation. The model successfully reproduced observed treatment effects on soil C and N, and inorganic N leaching, for both sites. At the C-rich upland site, N addition led to relatively small reductions in soil C/N, low inorganic N leaching, and a substantial increase in organic soil C. At the C-poor lowland site, soil C/N ratio decreases and N leaching increases were much more dramatic, and soil C accumulation predicted to be smaller. The study suggests that (i) a simple model can effectively simulate observed changes in soil and leachate N; (ii) previous model predictions based on a constant soil C pool may overpredict future N leaching; (iii) N saturation may develop most rapidly in dry, organic-poor, high-decomposition systems; and (iv) N deposition may lead to significantly enhanced soil C sequestration, particularly in wet, nutrient-poor, organic-rich systems. - Enhanced carbon sequestration may slow the rate of nitrogen saturation in heathlands
19. Modelling nitrogen transformation and removal in mara river basin wetlands upstream of lake Victoria
Science.gov (United States)
Mayo, Aloyce W.; Muraza, Marwa; Norbert, Joel
2018-06-01
Lake Victoria, the largest lake in Africa, is a resource of social-economic potential in East Africa. This lake receives water from numerous tributaries including Mara River, which contributes about 4.8% of the total Lake water inflow. Unfortunately, Mara River basin faces environmental problems because of intensive settlement, agriculture, overgrazing in the basin and mining activities, which has lead to water pollution in the river, soil erosion and degradation, decreased soil fertility, loss of vegetation cover, decreased water infiltration capacity and increased sedimentation. One of the pollutants carried by the river includes nitrogen, which has contributed to ecological degradation of the Lake Victoria. Therefore this research work was intended to determine the effectiveness of Mara River wetland for removal of nitrogen and to establish nitrogen removal mechanisms in the wetland. To predict nitrogen removal in the wetland, the dynamics of nitrogen transformation was studied using a conceptual numerical model that takes into account of various processes in the system using STELLA II version 9.0®2006 software. Samples of model input from water, plants and sediments were taken for 45 days and were analyzed for pH, temperature, and DO in situ and chemical parameters such as NH3-N, Org-N, NO2-N, and NO3-N were analyzed in the laboratory in accordance with Standard methods. For plants, the density, dominance, biomass productivity and TN were determined and for sediments TN was analyzed. Inflow into the wetland was determined using stage-discharge relationship and was found to be 734,400 m3/day and the average wetland volume was 1,113,500 m3. Data collected by this study were used for model calibration of nitrogen transformation in this wetland while data from another wetland were used for model validation. It was found that about 37.8% of total nitrogen was removed by the wetland system largely through sedimentation (26.6%), plant uptake (6.6%) and
20. Studies in utilization of fertilizer and soil nitrogen by carrots
International Nuclear Information System (INIS)
Moussa, A.G.; Markgraf, G.; Geissler, T.
1985-01-01
Pot experiments were conducted to determine the extent of fertilizer N utilization by carrots, using double-labelled 15 N-ammonium nitrate. The degree of soil N utilization was also studied. The residual effect of nitrogen in the individual variants was determined in spinach grown as succeeding crop. Under the experimental conditions, N utilization was highest at high water supply (100 % of water capacity). Due to the daily rhythm of pot watering to approximately 100 % of water capacity, gas exchange (air and oxygen) was ensured as well, providing optimum growth conditions. At medium nitrogen rates (12.5 g N/m 2 ), carrots took up 44.5 % of the fertilizer N on sand and 54.5 % on loess soil. When water supply decreased to 70 % of the water capacity, utilization of fertilizer N declined to 26 % on sand and 43.8 % on loess soil. Spinach grown as succeeding crop took up more soil N than fertilizer N. (author)
1. Gaseous losses of fertilizer nitrogen from soils under various conditions
International Nuclear Information System (INIS)
Smirnov, P.M.; Pedishyus, R.K.
1974-01-01
Effects of aerobic and anaerobic conditions; pH, and soil sterilization on the nitrogen loss from ( 15 NH 4 ) 2 SO 4 , Ca( 15 NO 3 ) 2 and Na 15 NO 2 have been studied in vitro. Composition of the liberated gases has been determined by the adsorption chromatography technique. Gaseous losses of fertilizer nitrogen are shown to proceed most intensely during first 10 to 30 days after nitrogen application, Ca(NO 3 ) 2 nitrogen loss being much higher than that of (NH 4 ) 2 SO 4 . Under anaerobic conditions nitrogen losses are markedly higher than in the presence of oxygen. Nitrogen of Ca(NO 3 ) 2 and (NH 4 ) 2 SO 4 is lost mainly as N 2 O and N 2 , the proportion of NO and NO 2 under aerobic and, particularly, anaerobic conditions is very small. Fertilizer type and aeration affect strongly the composition of liberated gases and the N 2 O:N 2 ratio. Under anaerobic conditions, Ca(NO 3 ) 2 nitrogen, beginning from the first days, is lost mainly as N 2 (75-80%), N 2 O makes up only 12 to 14%. Under aerobic conditions, (NH 4 ) 2 SO 4 and Ca(NO 3 ) 2 release initially a considerable amount of N 2 O, its reduction to N 2 being inhibited. In the course of time, however, a noticeable growth of the N 2 fraction occurs and it is accompanied by the decrease in N 2 O. Soil pH effects are related mainly to the composition of gases released rather than to the total nitrogen loss by Ca(NO 3 ) 2 . Under anaerobic conditions, more reduced gaseous products N 2 O and N 2 - are formed at acidic and neutral soil reaction, the amount of N 2 being greater at pH 7 than at pH 4.4. Under aerobic conditions, Ca(NO 3 ) 2 at pH 7 loses nitrogen mostly as N 2 , while under acidic soil reaction (pH 4.1-4.4) the losses occur as N 2 O and in part as NO and NO 2 . Sterilized soil at acidic pH liberates primarily nitrogen oxide which is formed apparently as a result of chemical reactions with participation of nitrites
2. Modeling of nitrogen transformation in an integrated multi-trophic aquaculture (IMTA)
Science.gov (United States)
Silfiana; Widowati; Putro, S. P.; Udjiani, T.
2018-03-01
The dynamic model of nitrogen transformation in IMTA (Integrated Multi-Trophic Aquaculture) is purposed. IMTA is a polyculture with several biotas maintained in it to optimize waste recycling as a food source. The purpose of this paper is to predict nitrogen decrease and nitrogen transformation in IMTA consisting of ammonia (NH3), Nitrite (NO2) and Nitrate (NO3). Nitrogen transformation of several processes, nitrification, assimilation, and volatilization. Numerical simulations are performed by providing initial parameters and values based on a review of previous research. The numerical results show that the rate of change in nitrogen concentration in IMTA decrease and reaches stable at different times.
3. Soil nitrate testing supports nitrogen management in irrigated annual crops
Directory of Open Access Journals (Sweden)
Patricia A. Lazicki
2016-12-01
Full Text Available Soil nitrate (NO3− tests are an integral part of nutrient management in annual crops. They help growers make field-specific nitrogen (N fertilization decisions, use N more efficiently and, if necessary, comply with California's Irrigated Lands Regulatory Program, which requires an N management plan and an estimate of soil NO3− from most growers. As NO3− is easily leached into deeper soil layers and groundwater by rain and excess irrigation water, precipitation and irrigation schedules need to be taken into account when sampling soil and interpreting test results. We reviewed current knowledge on best practices for taking and using soil NO3− tests in California irrigated annual crops, including how sampling for soil NO3− differs from sampling for other nutrients, how tests performed at different times of the year are interpreted and some of the special challenges associated with NO3− testing in organic systems.
4. LBA-ECO ND-08 Soil Respiration, Soil Fractions, Carbon and Nitrogen, Para, Brazil
Data.gov (United States)
National Aeronautics and Space Administration — ABSTRACT: This data set provides (1) carbon (C) and nitrogen (N) concentration measurements of two soil aggregate fractions (250-2000 micon, small macro-aggregates...
5. Convergence of soil nitrogen isotopes across global climate gradients
Science.gov (United States)
Craine, Joseph M.; Elmore, Andrew J.; Wang, Lixin; Augusto, Laurent; Baisden, W. Troy; Brookshire, E. N. J.; Cramer, Michael D.; Hasselquist, Niles J.; Hobbie, Erik A.; Kahmen, Ansgar; Koba, Keisuke; Kranabetter, J. Marty; Mack, Michelle C.; Marin-Spiotta, Erika; Mayor, Jordan R.; McLauchlan, Kendra K.; Michelsen, Anders; Nardoto, Gabriela B.; Oliveira, Rafael S.; Perakis, Steven S.; Peri, Pablo L.; Quesada, Carlos A.; Richter, Andreas; Schipper, Louis A.; Stevenson, Bryan A.; Turner, Benjamin L.; Viani, Ricardo A. G.; Wanek, Wolfgang; Zeller, Bernd
2015-01-01
Quantifying global patterns of terrestrial nitrogen (N) cycling is central to predicting future patterns of primary productivity, carbon sequestration, nutrient fluxes to aquatic systems, and climate forcing. With limited direct measures of soil N cycling at the global scale, syntheses of the 15 N: 14 N ratio of soil organic matter across climate gradients provide key insights into understanding global patterns of N cycling. In synthesizing data from over 6000 soil samples, we show strong global relationships among soil N isotopes, mean annual temperature (MAT), mean annual precipitation (MAP), and the concentrations of organic carbon and clay in soil. In both hot ecosystems and dry ecosystems, soil organic matter was more enriched in 15 N than in corresponding cold ecosystems or wet ecosystems. Below a MAT of 9.8°C, soil δ15N was invariant with MAT. At the global scale, soil organic C concentrations also declined with increasing MAT and decreasing MAP. After standardizing for variation among mineral soils in soil C and clay concentrations, soil δ15N showed no consistent trends across global climate and latitudinal gradients. Our analyses could place new constraints on interpretations of patterns of ecosystem N cycling and global budgets of gaseous N loss.
6. A Compilation of Global Soil Microbial Biomass Carbon, Nitrogen, and Phosphorus Data
Data.gov (United States)
National Aeronautics and Space Administration — This data set provides the concentrations of soil microbial biomass carbon (C), nitrogen (N) and phosphorus (P), soil organic carbon, total nitrogen, and total...
7. Predicting soil nitrogen content using narrow-band indices from ...
African Journals Online (AJOL)
Optimal fertiliser applications for sustainable forest stand productivity management, whilst protecting the environment, is vital. This study estimated soil nitrogen content using leaf-level narrow-band vegetation indices derived from a hand-held 350–2 500 nm spectroradiometer. Leaf-level spectral data were collected and ...
8. Evaluation of the soil organic carbon, nitrogen and available ...
African Journals Online (AJOL)
The result obtained indicates that the level of these chemical properties were generally low as compared to standard measures and parameter for ratings soil fertility in the Nigerian Savanna. Keywords: Status of organic carbon, total nitrogen, available phosphorus, top horizons, research farm. Bowen Journal of Agriculture ...
9. Total Nitrogen and Available Phosphorus Dynamics in Soils ...
African Journals Online (AJOL)
Total nitrogen and available phosphorus concentration of soils in three secondary forest fields aged 1, 5 and 10 years of age regenerating from degraded abandoned rubber plantation (Hevea brasiliensis) and a mature forest in the west African Rainforest belt in southern Nigeria were investigated in order to determine the ...
10. Soil organic nitrogen mineralization across a global latitudinal gradient
Science.gov (United States)
D.L. Jones; K. Kielland; F.L. Sinclair; R.A. Dahlgren; K.K. Newsham; J.F. Farrar; D.V. Murphy
2009-01-01
Understanding and accurately predicting the fate of carbon and nitrogen in the terrestrial biosphere remains a central goal in ecosystem science. Amino acids represent a key pool of C and N in soil, and their availability to plants and microorganisms has been implicated as a major driver in regulating ecosystem functioning. Because of potential differences in...
11. Development of soil properties and nitrogen cycling in created wetlands
Science.gov (United States)
Wolf, K.L.; Ahn, C.; Noe, G.B.
2011-01-01
Mitigation wetlands are expected to compensate for the loss of structure and function of natural wetlands within 5–10 years of creation; however, the age-based trajectory of development in wetlands is unclear. This study investigates the development of coupled structural (soil properties) and functional (nitrogen cycling) attributes of created non-tidal freshwater wetlands of varying ages and natural reference wetlands to determine if created wetlands attain the water quality ecosystem service of nitrogen (N) cycling over time. Soil condition component and its constituents, gravimetric soil moisture, total organic carbon, and total N, generally increased and bulk density decreased with age of the created wetland. Nitrogen flux rates demonstrated age-related patterns, with younger created wetlands having lower rates of ammonification, nitrification, nitrogen mineralization, and denitrification potential than older created wetlands and natural reference wetlands. Results show a clear age-related trajectory in coupled soil condition and N cycle development, which is essential for water quality improvement. These findings can be used to enhance N processing in created wetlands and inform the regulatory evaluation of mitigation wetlands by identifying structural indicators of N processing performance.
12. Nitrogen Fertilization Increases Cottonwood Growth on Old-Field Soil
Science.gov (United States)
B. G. Blackmon; E. H. White
1972-01-01
Nitrogen (150 lb ./acre as NH4N03 ) applied to a 6-year-old eastern cottonwood plantation in an old field on Commerce silt loam soil increased diameter, basal area, and volume growth by 200 percent over untreated controls. The plantation did not respond to 100 pounds P per acre from concentrated superphosphate.
13. Improvement of nitrogen utilization and soil properties by addition of a mineral soil conditioner: mechanism and performance.
Science.gov (United States)
Yan, Xiaodan; Shi, Lin; Cai, Rumeng
2018-01-01
A mineral soil conditioner (MSC) composed of activated potash feldspar, gypsum, and calcium carbonate and containing an amount of available mineral nutrients, is shown to be effective for plant growth and acidic soil amelioration. In this study, a field test was conducted over four rice seasons by examining treatment with control check (CK), MSC, biological active carbon, and lime to investigate the nitrogen-use efficiency and mechanism of soil characteristic variations due to the desilicification and allitization of soil as well as the unrestrained use of nitrogen (N) fertilizer in recent years. Influences of MSC on the xylem sap intensity and mean rice yields were evaluated, and the soil type was also analyzed using the FactSage 6.1 Reaction, phase diagram, and Equilib modules. The results of the field trial showed that MSC application increased the xylem sap intensity and nitrogen export intensity by 37.33-39.85% and 31.40-51.20%, respectively. A significant increase (5.63-15.48%) in mean grain yields was achieved with MSC application over that with biological active carbon and lime application. The effects of MSC had a tendency to increase with time in the field experiment results, and grain yields increased after the initial application. The new formation of clay minerals exhibits a significant influence on [Formula: see text] fixation, especially for 2:1 phyllosilicates with illite, owing to the interlayers of the clay minerals. Our preliminary results showed that kaolinite, the main 1:1 phyllosilicate clay mineral in ferralsol, transformed to illite at room temperature as a consequence of the presence of H 4 SiO 4 and available K + supplied by MSC. This indicated that improving the soil quality combined with reducing N losses from soils is an efficient way to control non-point source pollution from agriculture without the risk of decreased in grain yield.
14. Impact of Hydrologic and Micro-topographic Variabilities on Spatial Distribution of Mean Soil-Nitrogen Age
Science.gov (United States)
Woo, D.; Kumar, P.
2015-12-01
Excess reactive nitrogen in soils of intensively managed agricultural fields causes adverse environmental impact, and continues to remain a global concern. Many novel strategies have been developed to provide better management practices and, yet, the problem remains unresolved. The objective of this study is to develop a 3-dimensional model to characterize the spatially distributed age" of soil-nitrogen (nitrate and ammonia-ammonium) across a watershed. We use the general theory of age, which provides an assessment of the elapsed time since nitrogen is introduced into the soil system. Micro-topographic variability incorporates heterogeneity of nutrient transformations and transport associated with topographic depressions that form temporary ponds and produce prolonged periods of anoxic conditions, and roadside agricultural ditches that support rapid surface movement. This modeling effort utilizes 1-m Light Detection and Ranging (LiDAR) data. We find a significant correlation between hydrologic variability and mean nitrate age that enables assessment of preferential flow paths of nitrate leaching. The estimation of the mean nitrogen age can thus serve as a tool to disentangle complex nitrogen dynamics by providing the analysis of the time scales of soil-nitrogen transformation and transport processes without introducing additional parameters.
15. [Interactions of straw, nitrogen fertilizer and bacterivorous nematodes on soil labile carbon and nitrogen and greenhouse gas emissions].
Science.gov (United States)
Zhang, Teng-Hao; Wang, Nan; Liu, Man-Qiang; Li, Fang-Hui; Zhu, Kang-Li; Li, Hui-Xin; Hu, Feng
2014-11-01
A 3 x 2 factorial design of microcosm experiment was conducted to investigate the interactive effects of straw, nitrogen fertilizer and bacterivorous nematodes on soil microbial biomass carbon (C(mic)) and nitrogen (N(mic)), dissolved organic carbon (DOC) and nitrogen (DON), mineral nitrogen (NH(4+)-N and NO(3-)-N), and greenhouse gas (CO2, N2O and CH4) emissions. Results showed that straw amendment remarkably increased the numbers of bacterivorous nematodes and the contents of Cmic and Nmic, but Cmic and Nmic decreased with the increasing dose of nitrogen fertilization. The effects of bacterivorous nematodes strongly depended on either straw or nitrogen fertilization. The interactions of straw, nitrogen fertilization and bacterivorous nematodes on soil DOC, DON and mineral nitrogen were strong. Straw and nitrogen fertilization increased DOC and mineral nitrogen contents, but their influences on DON depended on the bacterivorous nematodes. The DOC and mineral nitrogen were negatively and positively influenced by the bacterivorous nematodes, re- spectively. Straw significantly promoted CO2 and N2O emissions but inhibited CH4 emission, while interactions between nematodes and nitrogen fertilization on emissions of greenhouse gases were obvious. In the presence of straw, nematodes increased cumulative CO2 emissions with low nitrogen fertilization, but decreased CO2 and N2O emissions with high nitrogen fertilization on the 56th day after incubation. In summary, mechanical understanding the soil ecological process would inevitably needs to consider the roles of soil microfauna.
16. Nitrogen Deposition Effects on Soil Carbon Dynamics in Temperate Forests
DEFF Research Database (Denmark)
Ginzburg Ozeri, Shimon
Soils contain the largest fraction of terrestrial carbon (C). Understanding the factors regulating the decomposition and storage of soil organic matter (SOM) is essential for predictions of the C sink strength of the terrestrial environment in the light of global change. Elevated long-term nitrog...... implications for modelling the carbon sink-strength of temperate forests under global change.......Soils contain the largest fraction of terrestrial carbon (C). Understanding the factors regulating the decomposition and storage of soil organic matter (SOM) is essential for predictions of the C sink strength of the terrestrial environment in the light of global change. Elevated long-term nitrogen...... (N) deposition into forest ecosystems has been increasing globally and was hypothesized to raise soil organic C (SOC) stocks by increasing forest productivity and by reducing SOM decomposition. Yet, these effects of N deposition on forest SOC stocks are uncertain and largely based on observations...
17. Hydrologic control on redox and nitrogen dynamics in a peatland soil
International Nuclear Information System (INIS)
Rubol, Simonetta; Silver, Whendee L.; Bellin, Alberto
2012-01-01
Soils are a dominant source of nitrous oxide (N 2 O), a potent greenhouse gas. However, the complexity of the drivers of N 2 O production and emissions has hindered our ability to predict the magnitude and spatial dynamics of N 2 O fluxes. Soil moisture can be considered a key driver because it influences oxygen (O 2 ) supply, which feeds back on N 2 O sources (nitrification versus denitrification) and sinks (reduction to dinitrogen). Soil water content is directly linked to O 2 and redox potential, which regulate microbial metabolism and chemical transformations in the environment. Despite its importance, only a few laboratory studies have addressed the effects of hydrological transient dynamics on nitrogen (N) cycling in the vadose zone. To further investigate these aspects, we performed a long term experiment in a 1.5 m depth soil column supplemented by chamber experiments. With this experiment, we aimed to investigate how soil moisture dynamics influence redox sensitive N cycling in a peatland soil. As expected, increased soil moisture lowered O 2 concentrations and redox potential in the soil. The decline was more severe for prolonged saturated conditions than for short events and at deep than at the soil surface. Gaseous and dissolved N 2 O, dissolved nitrate (NO 3 − ) and ammonium (NH 4 + ) changed considerably along the soil column profile following trends in soil O 2 and redox potential. Hot spots of N 2 O concentrations corresponded to high variability in soil O 2 in the upper and lower parts of the column. Results from chamber experiments confirmed high NO 3 − reduction potential in soils, particularly from the bottom of the column. Under our experimental conditions, we identified a close coupling of soil O 2 and N 2 O dynamics, both of which lagged behind soil moisture changes. These results highlight the relationship among soil hydrologic properties, redox potential and N cycling, and suggest that models working at a daily scale need to consider
18. Nitrogen release from forest soils containing sulfide-bearing sediments
Science.gov (United States)
Maileena Nieminen, Tiina; Merilä, Päivi; Ukonmaanaho, Liisa
2014-05-01
Soils containing sediments dominated by metal sulfides cause high acidity and release of heavy metals, when excavated or drained, as the aeration of these sediments causes formation of sulfuric acid. Consequent leaching of acidity and heavy metals can kill tree seedlings and animals such as fish, contaminate water, and corrode concrete and steel. These types of soils are called acid sulfate soils. Their metamorphic equivalents, such as sulfide rich black shales, pose a very similar risk of acidity and metal release to the environment. Until today the main focus in treatment of the acid sulfate soils has been to prevent acidification and metal toxicity to agricultural crop plants, and only limited attention has been paid to the environmental threat caused by the release of acidity and heavy metals to the surrounding water courses. Even less attention is paid on release of major nutrients, such as nitrogen, although these sediments are extremely rich in carbon and nitrogen and present a potentially high microbiological activity. In Europe, the largest cover of acid sulfate soils is found in coastal lowlands of Finland. Estimates of acid sulfate soils in agricultural use range from 1 300 to 3 000 km2, but the area in other land use classes, such as managed peatland forests, is presumably larger. In Finland, 49 500 km2 of peatlands have been drained for forestry, and most of these peatland forests will be at the regeneration stage within 10 to 30 years. As ditch network maintenance is often a prerequisite for a successful establishment of the following tree generation, the effects of maintenance operations on the quality of drainage water should be under special control in peatlands underlain by sulfide-bearing sediments. Therefore, identification of risk areas and effective prevention of acidity and metal release during drain maintenance related soil excavating are great challenges for forestry on coastal lowlands of Finland. The organic and inorganic nitrogen
19. 15N-urea transport and transformation in two deforsted Amazonian soils under laboratory conditions
International Nuclear Information System (INIS)
Victoria, R.L.; Libardi, P.L.; Reichardt, K.; Matsui, E.
1982-01-01
Brazilian agriculture is now expanding toward the Amazon region, where large new areas of virgin lands are being brought under cultivation. There is therefore an urgent need to better understand the conditions and characteristics of the soils of that region. In this study a Red Yellow Podzol and a Yellow Latosol were used to examine urea transport and transformation in the laboratory under water-saturated conditions. The soils were collected in an area that was deforested in 1976 and planted to tropical fruits since then. Soils were subjected to miscible displacement techniques under both continuous feed and pulse applications of urea to mathematically describe urea transport and transformation as functions of depth and time. Transformation mechanisms were considered to be first order kinetics. Urea was readily leached from both soils. Recovery of urea in the effluent of the 30 cm columns was 91%, for the Podzol and 86% for the Latosol. NH 4+ -N from urea hydrolysis was also readily leached and its recovery in the effluent was 4.2% for the Podzol and 11.2% for the Latosol. Very little nitrogen-including exchangeable NH 4+ -N and biomass nitrogen - was left in the columns of either soil at the end of the experiment. (orig.)
20. Bacterial quorum sensing and nitrogen cycling in rhizosphere soil
Energy Technology Data Exchange (ETDEWEB)
DeAngelis, K.M.; Lindow, S.E.; Firestone, M.K.
2008-10-01
Plant photosynthate fuels carbon-limited microbial growth and activity, resulting in increased rhizosphere nitrogen (N)-mineralization. Most soil organic N is macromolecular (chitin, protein, nucleotides); enzymatic depolymerization is likely rate-limiting for plant N accumulation. Analyzing Avena (wild oat) planted in microcosms containing sieved field soil, we observed increased rhizosphere chitinase and protease specific activities, bacterial cell densities, and dissolved organic nitrogen (DON) compared to bulk soil. Low-molecular weight DON (<3000 Da) was undetectable in bulk soil but comprised 15% of rhizosphere DON. Extracellular enzyme production in many bacteria requires quorum sensing (QS), cell-density dependent group behavior. Because proteobacteria are considered major rhizosphere colonizers, we assayed the proteobacterial QS signals acyl-homoserine lactones (AHLs), which were significantly increased in the rhizosphere. To investigate the linkage between soil signaling and N cycling, we characterized 533 bacterial isolates from Avena rhizosphere: 24% had chitinase or protease activity and AHL production; disruption of QS in 7 of 8 eight isolates disrupted enzyme activity. Many {alpha}-Proteobacteria were newly found with QS-controlled extracellular enzyme activity. Enhanced specific activities of N-cycling enzymes accompanied by bacterial density-dependent behaviors in rhizosphere soil gives rise to the hypothesis that QS could be a control point in the complex process of rhizosphere N-mineralization.
1. Solvent-dependent transformation of aflatoxin B1 in soil.
Science.gov (United States)
Starr, James M; Rushing, Blake R; Selim, Mustafa I
2017-08-01
To date, all studies of aflatoxin B 1 (AFB 1 ) transformation in soil or in purified mineral systems have identified aflatoxins B 2 (AFB 2 ) and G 2 (AFG 2 ) as the primary transformation products. However, identification in these studies was made using thin layer chromatography which has relatively low resolution, and these studies did not identify a viable mechanism by which such transformations would occur. Further, the use of methanol as the solvent delivery vehicle in these studies may have contributed to formation of artifactual transformation products. In this study, we investigated the role of the solvent vehicle in the transformation of AFB 1 in soil. To do this, we spiked soils with AFB 1 dissolved in water (93:7, water/methanol) or methanol and used HPLC-UV and HPLC-MS to identify the transformation products. Contrasting previous published reports, we did not detect AFB 2 or AFG 2 . In an aqueous-soil environment, we identified aflatoxin B 2a (AFB 2a ) as the single major transformation product. We propose that AFB 2a is formed from hydrolysis of AFB 1 with the soil acting as an acid catalyst. Alternatively, when methanol was used, we identified methoxy aflatoxin species likely formed via acid-catalyzed addition of methanol to AFB 1 . These results suggest that where soil moisture is adequate, AFB 1 is hydrolyzed to AFB 2a and that reactive organic solvents should be avoided when replicating natural conditions to study the fate of AFB 1 in soil.
2. What is the prognosis of nitrogen losses from UK soils?
Science.gov (United States)
Burt, T. P.; Worrall, F.; Whelan, M.; Howden, N. J.
2009-12-01
The UK’s high population density, intensive agriculture and relative short, unimpeded rivers mean that the UK is a known “hotspot” of fluvial nitrogen flux. Furthermore, it is known that the fluvial flux of nitrogen from the UK is increasing. This study estimates the release of nitrate from the UK terrestrial biosphere to understand this rising fluvial flux and i to assess the in-stream losses of nitrate, thusgiving an assessment of the fluvial component of the total nitrogen budget of UK. The approach taken by the study is to use an export coefficient model coupled with a description of mineralisation and immobilisation of nitrogen within soil reserves. The study applies the modelling approach to the whole of the UK from 1925 to 2007 using long term records of: land use (including - agricultural, forestry and urban uses); livestock; human population and atmospheric deposition. The study shows that: i) The flux of nitrate from the UK soils varied from 420 to 1463 Ktonnes N/yr with two peaks in the period since 1925, one in 1944 and one in 1967, the first is caused by mineralisation of soil organic matter following large-scale land use change in the Second World War, and the second is a multifactorial response to land use change and intensification. ii) The current trend in the release from soils is downward whilst the current fluvial flux at the tidal limit is upwards. With the current trends fluvial flux at the tidal limit will be greater than release from the soils of the UK, i.e. there will be net gain across the fluvial network. This apparent gain can be explained by the breakthrough of high nitrate groundwater into surface waters.
3. Seasonal photochemical transformations of nitrogen species in a forest stream and lake.
Directory of Open Access Journals (Sweden)
Petr Porcal
Full Text Available The photochemical release of inorganic nitrogen from dissolved organic matter is an important source of bio-available nitrogen (N in N-limited aquatic ecosystems. We conducted photochemical experiments and used mathematical models based on pseudo-first-order reaction kinetics to quantify the photochemical transformations of individual N species and their seasonal effects on N cycling in a mountain forest stream and lake (Plešné Lake, Czech Republic. Results from laboratory experiments on photochemical changes in N speciation were compared to measured lake N budgets. Concentrations of organic nitrogen (Norg; 40-58 µmol L-1 decreased from 3 to 26% during 48-hour laboratory irradiation (an equivalent of 4-5 days of natural solar insolation due to photochemical mineralization to ammonium (NH4+ and other N forms (Nx; possibly N oxides and N2. In addition to Norg mineralization, Nx also originated from photochemical nitrate (NO3- reduction. Laboratory exposure of a first-order forest stream water samples showed a high amount of seasonality, with the maximum rates of Norg mineralization and NH4+ production in winter and spring, and the maximum NO3- reduction occurring in summer. These photochemical changes could have an ecologically significant effect on NH4+ concentrations in streams (doubling their terrestrial fluxes from soils and on concentrations of dissolved Norg in the lake. In contrast, photochemical reactions reduced NO3- fluxes by a negligible (<1% amount and had a negligible effect on the aquatic cycle of this N form.
4. Fate of fertilizer nitrogen in flooded rice soil - I. Leaching losses of nitrogen
International Nuclear Information System (INIS)
Daftardar, S.Y.; Deb, D.L.; Datta, N.P.
1979-01-01
A greenhouse experiment on rice (Oryza sativa L. cv IR 22) was conducted under flooded conditions using CO( 15 NH 2 ) 2 , 15 NH 4 NO 3 and NH 4 ( 15 NO 3 ) to study the leaching loss of added fertilizer nitrogen in two typical rice soils. The loss of nitrogen was in the order: NO 3 -N (4 to 25.6 percent) > amide-N (1.2 to 16.2 percent) > NH 4 -N (0.07 to 0.3 percent). The basal applied urea was lost by percolation in the first month while the basal applied NO 3 -N was lost in the first 8 days. Leaching loss did not occur after split application of fertilizer nitrogen at primordial initiation stage. The loss of nitrogen in kaolinitic Dapoli clay loam soil was about 2.5 to 4.5 times more than that in montmorillonitic Karjat sandy loam soil. Cropping reduced the percolation loss of N by 40 to 60 percent. (auth.)
5. The Impacts of Soil Fertility and Salinity on Soil Nitrogen Dynamics Mediated by the Soil Microbial Community Beneath the Halophytic Shrub Tamarisk.
Science.gov (United States)
Iwaoka, Chikae; Imada, Shogo; Taniguchi, Takeshi; Du, Sheng; Yamanaka, Norikazu; Tateno, Ryunosuke
2018-05-01
Nitrogen (N) is one of the most common limiting nutrients for primary production in terrestrial ecosystems. Soil microbes transform organic N into inorganic N, which is available to plants, but soil microbe activity in drylands is sometimes critically suppressed by environmental factors, such as low soil substrate availability or high salinity. Tamarisk (Tamarix spp.) is a halophytic shrub species that is widely distributed in the drylands of China; it produces litter enriched in nutrients and salts that are thought to increase soil fertility and salinity under its crown. To elucidate the effects of tamarisks on the soil microbial community, and thus N dynamics, by creating "islands of fertility" and "islands of salinity," we collected soil samples from under tamarisk crowns and adjacent barren areas at three habitats in the summer and fall. We analyzed soil physicochemical properties, inorganic N dynamics, and prokaryotic community abundance and composition. In soils sampled beneath tamarisks, the N mineralization rate was significantly higher, and the prokaryotic community structure was significantly different, from soils sampled in barren areas, irrespective of site and season. Tamarisks provided suitable nutrient conditions for one of the important decomposers in the area, Verrucomicrobia, by creating "islands of fertility," but provided unsuitable salinity conditions for other important decomposers, Flavobacteria, Gammaproteobacteria, and Deltaproteobacteria, by mitigating salt accumulation. However, the quantity of these decomposers tended to be higher beneath tamarisks, because they were relatively unaffected by the small salinity gradient created by the tamarisks, which may explain the higher N mineralization rate beneath tamarisks.
6. Laccase mediated transformation of 17β-estradiol in soil
International Nuclear Information System (INIS)
Singh, Rashmi; Cabrera, Miguel L.; Radcliffe, David E.; Zhang, Hao; Huang, Qingguo
2015-01-01
It is known that 17β-estradiol (E2) can be transformed by reactions mediated by some oxidoreductases such as laccase in water. Whether or how such reactions can happen in soil is however unknown although they may significantly impact the environmental fate of E2 that is introduced to soil by land application of animal wastes. We herein studied the reaction of E2 in a model soil mediated by laccase, and found that the reaction behaviors differ significantly from those in water partly because of the dramatic difference in laccase stability. We also examined E2 transformation in soil using 14 C-labeling in combination with soil organic matter extraction and size exclusion chromatography, which indicated that applied 14 C radioactivity was preferably bound to humic acids. The study provides useful information for understanding the environmental fate of E2 and for developing a novel soil remediation strategy via enzyme-enhanced humification reactions. - Highlights: • E2 was effectively transformed in soil through reactions mediated by laccase. • The reaction behaviors in soil differ significantly from those in water. • E2 was preferably bound to the humic acids in soil. • Laccase treatment resulted in changes in the structures of the humic acids. - E2 was effectively transformed in soil by preferably binding to the humic acids through reactions mediated by laccase
7. Empirical model for mineralisation of manure nitrogen in soil
DEFF Research Database (Denmark)
Sørensen, Peter; Thomsen, Ingrid Kaag; Schröder, Jaap
2017-01-01
A simple empirical model was developed for estimation of net mineralisation of pig and cattle slurry nitrogen (N) in arable soils under cool and moist climate conditions during the initial 5 years after spring application. The model is based on a Danish 3-year field experiment with measurements...... of N uptake in spring barley and ryegrass catch crops, supplemented with data from the literature on the temporal release of organic residues in soil. The model estimates a faster mineralisation rate for organic N in pig slurry compared with cattle slurry, and the description includes an initial N...
8. Soil Carbon and Nitrogen Stocks of Different Hawaiian Sugarcane Cultivars
Directory of Open Access Journals (Sweden)
2015-06-01
Full Text Available Sugarcane has been widely used as a biofuel crop due to its high biological productivity, ease of conversion to ethanol, and its relatively high potential for greenhouse gas reduction and lower environmental impacts relative to other derived biofuels from traditional agronomic crops. In this investigation, we studied four sugarcane cultivars (H-65-7052, H-78-3567, H-86-3792 and H-87-4319 grown on a Hawaiian commercial sugarcane plantation to determine their ability to store and accumulate soil carbon (C and nitrogen (N across a 24-month growth cycle on contrasting soil types. The main study objective establish baseline parameters for biofuel production life cycle analyses; sub-objectives included (1 determining which of four main sugarcane cultivars sequestered the most soil C and (2 assessing how soil C sequestration varies among two common Hawaiian soil series (Pulehu-sandy clay loam and Molokai-clay. Soil samples were collected at 20 cm increments to depths of up to 120 cm using hand augers at the three main growth stages (tillering, grand growth, and maturity from two experimental plots at to observe total carbon (TC, total nitrogen (TN, dissolved organic carbon (DOC and nitrates (NO−3 using laboratory flash combustion for TC and TN and solution filtering and analysis for DOC and NO−3. Aboveground plant biomass was collected and subsampled to determine lignin and C and N content. This study determined that there was an increase of TC with the advancement of growing stages in the studied four sugarcane cultivars at both soil types (increase in TC of 15–35 kg·m2. Nitrogen accumulation was more variable, and NO−3 (<5 ppm were insignificant. The C and N accumulation varies in the whole profile based on the ability of the sugarcane cultivar’s roots to explore and grow in the different soil types. For the purpose of storing C in the soil, cultivar H-65-7052 (TC accumulation of ~30 kg·m−2 and H-86-3792 (25 kg·m−2 rather H-78
9. Soil Nitrogen Availability Is Reflected in the Bacterial Pathway1
Institute of Scientific and Technical Information of China (English)
V.KRIVTSOV; B.S.GRIFFITHS; K.LIDDELL; A.GARSIDE; R.SALMOND; T.BEZGINOVA; J.THOMPSON
2011-01-01
Measurements of concentrations of easily extractable soil nitrogen (N) were carried out on samples collected at the Heron Wood Reserve, Scotland, concurrently with investigations of N associated with total microbial biomass and the abundances of bacteria,fungi, and invertebrates. Soil biota at the studied site appeared to be limited by N. There was a remarkable difference between the ambient (i.e., easily extractable N) and biomass nitrogen. The abundance data of bacteria, protozoa and nematodes significantly negatively correlated with ambient N but showed positive correlations with the total microbial N content. There were, however,remarkable differences between the correlation patterns exhibited by the fungal and the bacterial pathways, as fungi did not show any correlations with chemical variables. These differences should be taken into account whilst interpreting biological interactions both at this important site and elsewhere.
10. [Spatial characteristics of soil organic carbon and nitrogen storages in Songnen Plain maize belt].
Science.gov (United States)
Zhang, Chun-Hua; Wang, Zong-Ming; Ren, Chun-Ying; Song, Kai-Shan; Zhang, Bai; Liu, Dian-Wei
2010-03-01
By using the data of 382 typical soil profiles from the second soil survey at national and county levels, and in combining with 1:500000 digital soil maps, a spatial database of soil profiles was established. Based on this, the one meter depth soil organic carbon and nitrogen storage in Songnen Plain maize belt of China was estimated, with the spatial characteristics of the soil organic carbon and nitrogen densities as well as the relationships between the soil organic carbon and nitrogen densities and the soil types and land use types analyzed. The soil organic carbon and nitrogen storage in the maize belt was (163.12 +/- 26.48) Tg and (9.53 +/- 1.75) Tg, respectively, mainly concentrated in meadow soil, chernozem, and black soil. The soil organic carbon and nitrogen densities were 5.51-25.25 and 0.37-0.80 kg x m(-2), respectively, and the C/N ratio was about 7.90 -12.67. The eastern and northern parts of the belt had much higher carbon and nitrogen densities than the other parts of the belt, and upland soils had the highest organic carbon density [(19.07 +/- 2.44) kg x m(-2)], forest soils had the highest nitrogen density [(0.82 +/- 0.25) kg x m(-2)], while lowland soils had the lower organic carbon and nitrogen densities.
11. Nitrogen fixation by free-living organisms in rice soils. Studies with 15N
International Nuclear Information System (INIS)
Rao, V.R.; Charyulu, P.B.B.N.; Nayak, D.N.; Ramakrishna, C.
1979-01-01
Heterotrophic nitrogen fixation as influenced by water regime, organic matter, combined nitrogen and pesticides was investigated in several Indian rice soils by means of the 15 N 2 tracer technique. Soil submergence accelerated nitrogen fixation. Addition of cellulose to both non-flooded and flooded soils enhanced nitrogen fixation. Under submerged conditions, addition of sucrose, glucose and malate in that order stimulated nitrogen fixation in alluvial soil, while only sucrose enhanced nitrogen fixation in laterite soil. Nitrogen fixation in flooded alluvial and laterite soils decreased with increasing concentration of combined nitrogen. Nitrogen fixation was appreciable in acid sulphate and saline soils under both flooded and non-flooded conditions, despite high salinity and acidity. Application of certain pesticides at rates equivalent to recommended field level greatly influenced nitrogen fixation in flooded rice soils. Additions of benomyl (carbamate fungicide) and carbofuran (methyl carbamate insecticide) to alluvial and laterite soils resulted in significant stimulation of nitrogen fixation. Gamma-BHC stimulated nitrogen fixation only in alluvial soil, with considerable inhibition in a laterite soil. Nitrogen fixation by Azospirillum lipoferum was investigated by 15 N 2 . Large variations in 15 N 2 incorporation by A. lipoferum isolated from the roots of several rice cultivars was observed. Specific lines of rice harbouring A. lipoferum with high nitrogenase activity might be selected. Nitrogen fixed by heterotrophic organisms in a complex system such as soil could not be evaluated precisely. Indigenous nitrogen fixation in a flooded soil would be in the range of 5-10 kg N/ha, increasable 3 to 4-fold by appropriate fertilizers and cultural practices
12. [Influence of water deficit and supplemental irrigation on nitrogen uptake by winter wheat and nitrogen residual in soil].
Science.gov (United States)
Wang, Zhaohui; Wang, Bing; Li, Shengxiu
2004-08-01
Pot experiment in greenhouse showed that water deficit at all growth stages and supplemental irrigation at tillering stage significantly decreased the nitrogen uptake by winter wheat and increased the mineral N residual (79.8-113.7 mg x kg(-1)) in soil. Supplemental irrigation at over-wintering, jointing or filling stage significantly increased the nitrogen uptake by plant and decreased the nitrogen residual (47.2-60.3 mg x kg(-1)) in soil. But, the increase of nitrogen uptake caused by supplemental irrigation did not always mean a high magnitude of efficient use of nitrogen by plants. Supplemental irrigation at over-wintering stage didn't induce any significant change in nitrogen content of grain, irrigation at filling stage increased the nitrogen content by 20.9%, and doing this at jointing stage decreased the nitrogen content by 19.6%, as compared to the control.
13. Mortality hotspots: nitrogen cycling in forest soils during vertebrate decomposition
Science.gov (United States)
Decomposing plants and animals fundamentally transform their surrounding environments, and serve as a critical source of limiting nutrients for macro- and micro-fauna. Animal mortality hotspots alter soil biogeochemical cycles, and these natural ephemeral nutrient patches are important for maintaini...
14. Effect of combined N applied at low level on the nitrogen fixation by grasses and contribution to nitrogen fertility in soil
International Nuclear Information System (INIS)
Yao Yunyin; Chen Ming; Ma Changlin
1990-01-01
This paper reports the study on the effect of combined N applied at low level on teh nitrogen fixation by alfalfa in monoculture and mixed culture with meadow fescue, and the effect on the absorption and utilization of indigenous soil nitrogen and nitrogen fertilizer. Amount of nitrogen fixed by alfalfa could be raised and duration of high peak of symbiotic nitrogen fixation activity could be extended when nitrogen fertilizer was applied reasonably. It was especially important for the early pastures or pastures with low supporting nitrogen capacity. Transfer of nitrogen fixed by alfalfa to meadow fescue occured in mixed culture. Nitrogen fixed from alfalfa was uptaken more easily than indigenous nitrogen in soil. Planting alfalfa could raise soil fertility significantly. Meadow fescue may be able to fix nitrogen from the air in some way. When combined N was appropriately applied to soil, on which alfalfa and meadow fescue had been planted, it could promote increasing nitrogen fertility in soil
15. Soil nitrogen availability in the open steppe with Stipa tenacissima
Science.gov (United States)
Novosadova, Irena; Damian Ruiz Sinoga, Jose; Záhora, Jaroslav
2010-05-01
functioning, particularly in Mediterranean areas, where nutrient availability, mainly nitrogen and phosphorous, represents a limiting factor (Sardans et al., 2005) together with water availability. Soil N availability has been found to affect plant water use efficiency (Sardans et al., 2008a). This strong link between N availability and water use efficiency makes particularly important the understanding of factors affecting soil N availability in Mediterranean ecosystems in view of the future predicted increasing drought in this area. Changes in the soil nitrogen availability in the open steppe with S. tenacissima were monitored over a two distinct period of time during the years 2008 and 2009 at a field site in semi-arid south-eastern Spain (Novosádová et al., 2010). The availability of ammonia-nitrogen and nitrate nitrogen was estimated in situ according to Binkley at Matson (1982) by the trapping of mineral N into the ion exchange resin inserted into special cover. The availability of soil ammonia-N as well as the availability of nitrate-N were in the 2008 year significantly influenced by the addition of different substrate (only 38% of control after the cellulose addition and 176% of control after the raw silk addition). In the following 2009 year was the N availability probably due to favorable soil moisture nearly the same in all experimental variants. The availability of ammonia-N was, in general, higher than the availability of nitrate-N, but the differences were less noticeable in 2008 year. It can be concluded, that the microbial competition for available nitrogen is very high and spatially and/or temporary significantly different.
16. Spatial analysis and hazard assessment on soil total nitrogen in the middle subtropical zone of China
Science.gov (United States)
Lu, Peng; Lin, Wenpeng; Niu, Zheng; Su, Yirong; Wu, Jinshui
2006-10-01
Nitrogen (N) is one of the main factors affecting environmental pollution. In recent years, non-point source pollution and water body eutrophication have become increasing concerns for both scientists and the policy-makers. In order to assess the environmental hazard of soil total N pollution, a typical ecological unit was selected as the experimental site. This paper showed that Box-Cox transformation achieved normality in the data set, and dampened the effect of outliers. The best theoretical model of soil total N was a Gaussian model. Spatial variability of soil total N at NE60° and NE150° directions showed that it had a strip anisotropic structure. The ordinary kriging estimate of soil total N concentration was mapped. The spatial distribution pattern of soil total N in the direction of NE150° displayed a strip-shaped structure. Kriging standard deviations (KSD) provided valuable information that will increase the accuracy of total N mapping. The probability kriging method is useful to assess the hazard of N pollution by providing the conditional probability of N concentration exceeding the threshold value, where we found soil total N>2.0g/kg. The probability distribution of soil total N will be helpful to conduct hazard assessment, optimal fertilization, and develop management practices to control the non-point sources of N pollution.
17. Hydrologic control on redox and nitrogen dynamics in a peatland soil.
Science.gov (United States)
Rubol, Simonetta; Silver, Whendee L; Bellin, Alberto
2012-08-15
Soils are a dominant source of nitrous oxide (N(2)O), a potent greenhouse gas. However, the complexity of the drivers of N(2)O production and emissions has hindered our ability to predict the magnitude and spatial dynamics of N(2)O fluxes. Soil moisture can be considered a key driver because it influences oxygen (O(2)) supply, which feeds back on N(2)O sources (nitrification versus denitrification) and sinks (reduction to dinitrogen). Soil water content is directly linked to O(2) and redox potential, which regulate microbial metabolism and chemical transformations in the environment. Despite its importance, only a few laboratory studies have addressed the effects of hydrological transient dynamics on nitrogen (N) cycling in the vadose zone. To further investigate these aspects, we performed a long term experiment in a 1.5 m depth soil column supplemented by chamber experiments. With this experiment, we aimed to investigate how soil moisture dynamics influence redox sensitive N cycling in a peatland soil. As expected, increased soil moisture lowered O(2) concentrations and redox potential in the soil. The decline was more severe for prolonged saturated conditions than for short events and at deep than at the soil surface. Gaseous and dissolved N(2)O, dissolved nitrate (NO(3)(-)) and ammonium (NH(4)(+)) changed considerably along the soil column profile following trends in soil O(2) and redox potential. Hot spots of N(2)O concentrations corresponded to high variability in soil O(2) in the upper and lower parts of the column. Results from chamber experiments confirmed high NO(3)(-) reduction potential in soils, particularly from the bottom of the column. Under our experimental conditions, we identified a close coupling of soil O(2) and N(2)O dynamics, both of which lagged behind soil moisture changes. These results highlight the relationship among soil hydrologic properties, redox potential and N cycling, and suggest that models working at a daily scale need to
18. Mechanistic modeling of reactive soil nitrogen emissions across agricultural management practices
Science.gov (United States)
Rasool, Q. Z.; Miller, D. J.; Bash, J. O.; Venterea, R. T.; Cooter, E. J.; Hastings, M. G.; Cohan, D. S.
2017-12-01
The global reactive nitrogen (N) budget has increased by a factor of 2-3 from pre-industrial levels. This increase is especially pronounced in highly N fertilized agricultural regions in summer. The reactive N emissions from soil to atmosphere can be in reduced (NH3) or oxidized (NO, HONO, N2O) forms, depending on complex biogeochemical transformations of soil N reservoirs. Air quality models like CMAQ typically neglect soil emissions of HONO and N2O. Previously, soil NO emissions estimated by models like CMAQ remained parametric and inconsistent with soil NH3 emissions. Thus, there is a need to more mechanistically and consistently represent the soil N processes that lead to reactive N emissions to the atmosphere. Our updated approach estimates soil NO, HONO and N2O emissions by incorporating detailed agricultural fertilizer inputs from EPIC, and CMAQ-modeled N deposition, into the soil N pool. EPIC addresses the nitrification, denitrification and volatilization rates along with soil N pools for agricultural soils. Suitable updates to account for factors like nitrite (NO2-) accumulation not addressed in EPIC, will also be made. The NO and N2O emissions from nitrification and denitrification are computed mechanistically using the N sub-model of DAYCENT. These mechanistic definitions use soil water content, temperature, NH4+ and NO3- concentrations, gas diffusivity and labile C availability as dependent parameters at various soil layers. Soil HONO emissions found to be most probable under high NO2- availability will be based on observed ratios of HONO to NO emissions under different soil moistures, pH and soil types. The updated scheme will utilize field-specific soil properties and N inputs across differing manure management practices such as tillage. Comparison of the modeled soil NO emission rates from the new mechanistic and existing schemes against field measurements will be discussed. Our updated framework will help to predict the diurnal and daily variability
19. Impacts of insect biological control on soil N transformations in Tamarix-invaded ecosystems in the Great Basin
Science.gov (United States)
Understanding the impacts of insect biological control of Tamarix spp. on soil nitrogen (N) transformations is important because changes to N supply could alter plant community succession. We investigated short-term and longer-term impacts of herbivory by the northern tamarisk beetle (Diorhabda cari...
20. Soil microbial responses to nitrogen addition in arid ecosystems
Directory of Open Access Journals (Sweden)
Robert L Sinsabaugh
2015-08-01
Full Text Available The N cycle of arid ecosystems is influenced by low soil organic matter, high soil pH and extremes in water potential and temperature that lead to open canopies and development of biological soil crusts (biocrusts. We investigated the effects of N amendment on soil microbial dynamics in a Larrea tridentata-Ambrosia dumosa shrubland site in southern Nevada USA. Sites were fertilized with a NO3-NH4 mix at 0, 7, and 15 kg ha-1 yr-1 from March 2012 to March 2013. In March 2013, biocrust (0-0.5 cm and bulk soils (0-10 cm were collected beneath Ambrosia canopies and in the interspaces between plants. Biomass responses were assessed as bacterial and fungal SSU rRNA gene copy number and chlorophyll a concentration. Metabolic responses were measured by five ecoenzyme activities (EEA and rates of N transformation. By most measures, nutrient availability, microbial biomass and process rates were greater in soils beneath the shrub canopy compared to the interspace between plants, and greater in the surface biocrust horizon compared to the deeper 10 cm soil profile. Most measures responded positively to experimental N addition. Effect sizes were generally greater for bulk soil than biocrust. Results were incorporated into a meta-analysis of arid ecosystem responses to N.
1. Zeolite Soil Application Method Affects Inorganic Nitrogen, Moisture, and Corn Growth
Science.gov (United States)
Adoption of new management techniques which improve soil water storage and soil nitrogen plant availability yet limit nitrogen leaching may help improve environmental quality. A benchtop study was conducted to determine the influence of a single urea fertilizer rate (224 kilograms of Nitrogen per ...
2. Impact of Tile Drainage on the Distribution of Concentration and Age of Inorganic Soil Nitrogen.
Science.gov (United States)
Woo, D.; Kumar, P.
2017-12-01
Extensive network of tile drainage network across the Midwestern United States, northern Europe and other regions of the world have enhanced agricultural productivity. Because of its impact on sub-surface flow patterns and moisture and temperature dynamics, it controls the nitrogen cycle in agricultural systems, and its influence on nitrogen dynamics plays a key role in determining the short- and long-term evolution of soil inorganic nitrogen concentration and age. The spatial mapping of nitrogen concentration and age under tile-drained fields has, therefore, the potential to open up novel solution to the vexing challenge of reducing environmental impacts while at the same time maintaining agricultural productivity. The objective of this study is to explore the impacts of tile drains on the age dynamics of nitrate, immobile ammonium, mobile ammonia/um, and non-reactive tracer (such as chloride) by implementing two mobile interacting pore domains to capture matrix and preferential flow paths in a coupled ecohydrology and biogeochemistry model, Dhara. We applied this model to an agricultural farm supporting a corn-soybean rotation in the Midwestern United States. It should be expected that the installation of tile drains decrease the age of soil nutrient due to nutrient losses through tile drainage. However, an increase in the age of mobile ammonia/um is observed in contrast to the cases for nitrate, immobile ammonium, and non-reactive tracer. These results arise because the depletion of mobile ammonia/um due to tile drainage causes a high mobility flux from immobile ammonium to mobile ammonia/um, which also carries a considerable amount of relatively old age of immobile ammonium to mobile ammonia/um. In addition, the ages of nitrate and mobile ammonia/um in tile drainage range from 1 to 3 years, and less than a year, respectively, implying that not considering age transformations between nitrogen species would result in substantial underestimation of nitrogen ages
3. Exchangeable basic cations and nitrogen distribution in soil as affected by crop residues and nitrogen
Directory of Open Access Journals (Sweden)
Ciro Antonio Rosolem
2011-06-01
Full Text Available In this work, a greenhouse experiment was conducted to study the effects of N fertilization and residues of pearl millet, black oats and oilseed radish on pH and Ca, Mg, K, NO3-, and NH4+ distribution within the profile of a Distroferric Red Latosol. The equivalent of 8 t ha-1 of plant residues were placed on soil surface. Lime was applied on the soil surface and nitrogen was applied over the straw at 0, 50, 100, and 150 mg kg-1, as ammonium nitrate. Corn was grown for 57 days. Calcium contents and pH in the soil profile were decreased by Pearl millet residue, while black oat and oilseed radish increased Ca contents and these effects are not related with Ca contents in residue tissue. However, the presence of plant residues increased nitrate, ammonium, and potassium contents in the deeper layers of the pots.
4. Effects of poultry manure, compost, and biochar amendments on soil nitrogen dynamics in maize production systems
Science.gov (United States)
Ryals, R.; Tang, J.; Hastings, M. G.; Dell, C. J.; Sims, T.
2013-12-01
Intensification of animal agriculture has profound impacts on the global and local biogeochemistry of nitrogen (N), resulting in consequences to environmental and human health. In the Chesapeake Bay watershed, intensive agriculture is the primary contributor to N pollution, with animal manure comprising more than half of N from agriculture. Management interventions may play an important role in mitigating reactive N pollution in the Bay watershed. The objective of our research was to test management strategies that maximize benefits of poultry manure as an agricultural resource while minimizing it as a source of reactive nitrogen to the atmosphere and ground and surface waters. We conducted field experiments in two agricultural regions of the Chesapeake Bay watershed (Georgetown, Delaware and State College, Pennsylvania) to explore the effects of poultry manure amendments on gaseous N losses and soil N transformations. Treatments were applied at rates needed to meet the plant N demand at each site and included unfertilized controls, fertilizer N (urea), and raw, composted, or and biocharred poultry manure. The fate of the N from all sources was followed throughout the growing season. Global greenhouse gases emitted from soil (nitrous oxide [N2O] and carbon dioxide [CO2]) and regional air pollutants (nitrogen oxides [NOx] and ammonia [NH3]) were measured. Gas measurements were coupled with data on treatment effects on temperature, moisture, and concentrations of nitrate (NO3¬-) and ammonium (NH4+) in surface soils (0-10 cm). Soil NO3- and NH4+ were also measured approximately monthly in the soil profile (0-10, 10-30, 30-50, 50-70, and 70-100 cm) as an index of leaching potential. Plant N uptake and grain production were also quantified to quantify crop N use efficiency and compare measured N losses for each N source. Our results suggest that the form of poultry manure amendments can affect the magnitude of reactive N losses to the environment.
5. Dynamics of dissolved and extractable organic nitrogen upon soil amendment with crop residues
NARCIS (Netherlands)
Ros, G.H.; Hoffland, E.
2010-01-01
Dissolved organic nitrogen (DON) is increasingly recognized as a pivotal pool in the soil nitrogen (N) cycle. Numerous devices and sampling procedures have been used to estimate its size, varying from in situ collection of soil solution to extraction of dried soil with salt solutions. Extractable
6. Priming effects of the endophytic fungus Phomopsis liquidambari on soil mineral N transformations.
Science.gov (United States)
Chen, Yan; Ren, Cheng-Gang; Yang, Bo; Peng, Yao; Dai, Chuan-Chao
2013-01-01
Nitrogen (N) is a crucial nutrient for soil biota, and its cycling is determined by the organic carbon decomposing process. Some endophytic fungi are latent saprotrophs that trigger their saprotrophic metabolism to promote litter organic matter cycling as soon as the host tissue senesces or dies. However, the effects of endophytic fungi on litter and soil N dynamics in vitro have rarely been investigated. In this study, we investigated N dynamics (total and mineral N) in both litter and soil in incubations of a pure culture of an endophytic fungus Phomopsis liquidambari with litter and following soil burial of the litter. Soil enzymes and microbial communities participating in the N transformations were also investigated. A pure culture of P. liquidambari released litter NH (4) (+) -N in the initial stages (10 days) of the incubation. However, following soil burial, the presence of both P. liquidambari and soil ammonia-oxidizing bacteria (AOB) resulted in an increase in soil NO (3) (-) -N. These results indicate that the endophytic fungus P. liquidambari in vitro stimulates organic mineralization and promote NH (4) (+) -N release. Such effects triggered soil AOB-driven nitrification process.
7. Anthropogenic nitrogen deposition enhances carbon sequestration in boreal soils.
Science.gov (United States)
Maaroufi, Nadia I; Nordin, Annika; Hasselquist, Niles J; Bach, Lisbet H; Palmqvist, Kristin; Gundale, Michael J
2015-08-01
It is proposed that carbon (C) sequestration in response to reactive nitrogen (Nr ) deposition in boreal forests accounts for a large portion of the terrestrial sink for anthropogenic CO2 emissions. While studies have helped clarify the magnitude by which Nr deposition enhances C sequestration by forest vegetation, there remains a paucity of long-term experimental studies evaluating how soil C pools respond. We conducted a long-term experiment, maintained since 1996, consisting of three N addition levels (0, 12.5, and 50 kg N ha(-1) yr(-1) ) in the boreal zone of northern Sweden to understand how atmospheric Nr deposition affects soil C accumulation, soil microbial communities, and soil respiration. We hypothesized that soil C sequestration will increase, and soil microbial biomass and soil respiration will decrease, with disproportionately large changes expected compared to low levels of N addition. Our data showed that the low N addition treatment caused a non-significant increase in the organic horizon C pool of ~15% and a significant increase of ~30% in response to the high N treatment relative to the control. The relationship between C sequestration and N addition in the organic horizon was linear, with a slope of 10 kg C kg(-1) N. We also found a concomitant decrease in total microbial and fungal biomasses and a ~11% reduction in soil respiration in response to the high N treatment. Our data complement previous data from the same study system describing aboveground C sequestration, indicating a total ecosystem sequestration rate of 26 kg C kg(-1) N. These estimates are far lower than suggested by some previous modeling studies, and thus will help improve and validate current modeling efforts aimed at separating the effect of multiple global change factors on the C balance of the boreal region. © 2015 John Wiley & Sons Ltd.
8. Importance of soil nitrogen and select intensifying measures in the soil-plant-fertilizer system demonstrated in sugar beets
International Nuclear Information System (INIS)
Rauhe, K.; Sielaff, B.; Barth, F.J.
1981-01-01
Sugar beets were gradually fertilized with 15 N-labelled nitrogen fertilizer without or in combination with irrigation. To gain optimum crop yields 180 - 200 kg/ha fertilizer nitrogen were required. Within the range of maximum yield the total nitrogen uptake amounted to 300 - 360 kg/ha under conditions of irrigation. Nitrogen was taken up from the fertilizer by 40% and from the soil by 60%. The immobilization rate of fertilizer nitrogen was near 30% after 2 years of vegetation. Only 33% and 25%, resp., of soil nitrogen could be replaced by fertilizing without and combined with irrigation, resp. It was shown that despite of increased application of the main intensifying factors, nitrogen and water, the soil nitrogen was mineralized intensively
9. Transformation of the herbicide [14C]glufosinate in soils
International Nuclear Information System (INIS)
Smith, A.E.
1989-01-01
The degradation of 2 μg/g [ 14 C]glufosinate (DL-homoalan-4-ylmethylphosphinic acid) was studied in clay, clay loam, and sandy loam soils at 85% field capacity and at 20 degree C. Over a 4-week period the soils were extracted and analyzed for transformation products by radiochemical and gas chromatographic techniques. In all soils there was release of [ 14 C]carbon dioxide and formation of [ 14 C]-3-(hydroxymethylphosphinyl)propionic acid (MPPA) as major degradation products. Within 21 days, about 55% of the applied 14 C herbicide had been transformed to MPPA in the sandy loam and 19% to [ 14 C]carbon dioxide. After 28 days, approximately 45% of the 14 C herbicide had been transformed to MPPA in the clay and clay loam and 10% released as [ 14 C]carbon dioxide. At all samplings, other 14 C transformation products appeared to be insignificant
10. The effects of soil water conditions on nitrogen fertilization use efficiency
International Nuclear Information System (INIS)
Zhou Lingyun
1996-01-01
Concerning with applied nitrogen fertilizer, the uptake as well as loss of nitrogen is mainly related to soil water content. The effects of soil water condition in wheat field on the uptake, leach and loss of nitrogen fertilizer were studied using 15 N tracing technique. The results showed that within certain range of soil water supply, from 180 to 360 mm of available water storage, the loss of nitrogen was in direct proportion to the amount of fertilizer application and the nitrogen use efficiency decreased with the increase of nitrogen application. In other words, the nitrogen use efficiency descended with the nitrogen application increased in an order of 75 kgN/ha, 150 kgN/ha, 225 kgN/ha. One interesting result was that the nitrogen use efficiencies ranged from 17.0% to 30.5% for the treatments receiving the same application rate of 75 kgN/ha
11. A Dynamic Economic Analysis of Nitrogen-Induced Soil Acidification in China
OpenAIRE
Yang, Ziyan
2015-01-01
This paper studies the environmental value of nitrogen fertilizer in a rapeseed-rice double-crop system in China to address the issue of nitrogen-induced soil acidification in China’s farmland. Previous literature always regarded the acid rain as the most important contributor to soil acidification. Thus, previous literature seldom linked soil quality with nitrogen leaching but studied acidification as a side product of air pollution. However, the latest scientific evidences show that China’s...
12. Effects of nitrogen addition on soil fauna communities in Larix gmelinii and Fraxinus mandshurica plantations
OpenAIRE
Haifeng Zhuang; Yue Sun; Jiacun Gu; Yang Xu; Zhengquan Wang
2010-01-01
Soil fauna play a key role in regulating carbon allocation and nutrient cycling in terrestrial ecosystems. As soil fauna are sensitive to environmental changes, increases in soil nitrogen (N) availability resulting from global changes may profoundly influence the structure and function of soil faunal communities. However, the response of soil fauna in forest ecosystems to increases in soil N availability is still poorly understood. In order to explore the relationship between soil N availabil...
13. Soil Microbial Communities and Gas Dynamics Contribute to Arbuscular Mycorrhizal Nitrogen Uptake and Transfer to Plants
Science.gov (United States)
Hestrin, R.; Harrison, M. J.; Lehmann, J.
2016-12-01
Arbuscular mycorrhizal fungi (AMF) associate with most terrestrial plants and influence ecosystem ecology and biogeochemistry. There is evidence that AMF play a role in soil nitrogen cycling, in part by taking up nitrogen and transferring it to plants. However, many aspects of this process are poorly understood, including the factors that control fungal access to nitrogen stored in soil organic matter. In this study, we used stable isotopes and root exclusion to track nitrogen movement from organic matter into AMF and host plants. AMF significantly increased total plant biomass and nitrogen content, but both AMF and other soil microbes seemed to compete with plants for nitrogen. Surprisingly, gaseous nitrogen species also contributed significantly to plant nitrogen content under alkaline soil conditions. Our current experiments investigate whether free-living microbial communities that have evolved under a soil nitrogen gradient influence AMF access to soil organic nitrogen and subsequent nitrogen transfer to plants. This research links interactions between plants, mycorrhizal symbionts, and free-living microbes with terrestrial carbon and nitrogen dynamics.
14. Effects of combined application of organic and inorganic fertilizers plus nitrification inhibitor DMPP on nitrogen runoff loss in vegetable soils.
Science.gov (United States)
Yu, Qiaogang; Ma, Junwei; Zou, Ping; Lin, Hui; Sun, Wanchun; Yin, Jianzhen; Fu, Jianrong
2015-01-01
The application of nitrogen fertilizers leads to various ecological problems such as large amounts of nitrogen runoff loss causing water body eutrophication. The proposal that nitrification inhibitors could be used as nitrogen runoff loss retardants has been suggested in many countries. In this study, simulated artificial rainfall was used to illustrate the effect of the nitrification inhibitor DMPP (3,4-dimethyl pyrazole phosphate) on nitrogen loss from vegetable fields under combined organic and inorganic nitrogen fertilizer application. The results showed that during the three-time simulated artificial rainfall period, the ammonium nitrogen content in the surface runoff water collected from the DMPP application treatment increased by 1.05, 1.13, and 1.10 times compared to regular organic and inorganic combined fertilization treatment, respectively. In the organic and inorganic combined fertilization with DMPP addition treatment, the nitrate nitrogen content decreased by 38.8, 43.0, and 30.1% in the three simulated artificial rainfall runoff water, respectively. Besides, the nitrite nitrogen content decreased by 95.4, 96.7, and 94.1% in the three-time simulated artificial rainfall runoff water, respectively. A robust decline in the nitrate and nitrite nitrogen surface runoff loss could be observed in the treatments after the DMPP addition. The nitrite nitrogen in DMPP addition treatment exhibited a significant low level, which is near to the no fertilizer application treatment. Compared to only organic and inorganic combined fertilizer treatment, the total inorganic nitrogen runoff loss declined by 22.0 to 45.3% in the organic and inorganic combined fertilizers with DMPP addition treatment. Therefore, DMPP could be used as an effective nitrification inhibitor to control the soil ammonium oxidation in agriculture and decline the nitrogen runoff loss, minimizing the nitrogen transformation risk to the water body and being beneficial for the ecological environment.
15. Non-Linear Nitrogen Cycling and Ecosystem Calcium Depletion Along a Temperate Forest Soil Nitrogen Gradient
Science.gov (United States)
Sinkhorn, E. R.; Perakis, S. S.; Compton, J. E.; Cromack, K.; Bullen, T. D.
2007-12-01
Understanding how N availability influences base cation stores is critical for assessing long-term ecosystem sustainability. Indices of nitrogen (N) availability and the distribution of nutrients in plant biomass, soil, and soil water were examined across ten Douglas-fir (Pseudotsuga menziesii) stands spanning a three-fold soil N gradient (0-10 cm: 0.21 - 0.69% N, 0-100 cm: 9.2 - 28.8 Mg N ha-1) in the Oregon Coast Range. This gradient is largely the consequence of historical inputs from N2-fixing red alder stands that can add 100-200 kg N ha-1 yr-1 to the ecosystem for decades. Annual net N mineralization and litterfall N return displayed non-linear relationships with soil N, increasing initially, and then decreasing as N-richness increased. In contrast, nitrate leaching from deep soils increased linearly across the soil N gradient and ranged from 0.074 to 30 kg N ha-1 yr-1. Soil exchangeable Ca, Mg, and K pools to 1 m depth were negatively related to nitrate losses across sites. Ca was the only base cation exhibiting concentration decreases in both plant and soil pools across the soil N gradient, and a greater proportion of total available ecosystem Ca was sequestered in aboveground plant biomass at high N, low Ca sites. Our work supports a hierarchical model of coupled N-Ca cycles across gradients of soil N enrichment, with microbial production of mobile nitrate anions leading to depletion of readily available Ca at the ecosystem scale, and plant sequestration promoting Ca conservation as Ca supply diminishes. The preferential storage of Ca in aboveground biomass at high N and low Ca sites, while critical for sustaining plant productivity, may also predispose forests to Ca depletion in areas managed for intensive biomass removal. Long-term N enrichment of temperate forest soils appears capable of sustaining an open N cycle and key symptoms of N-saturation for multiple decades after the cessation of elevated N inputs.
16. [Effects of nitrogen deposition on the concentration and spectral characteristics of dissolved organic matter in soil solution in a young Cunninghamia lanceolata plantation.
Science.gov (United States)
Yuan, Xiao Chun; Chen, Yue Min; Yuan, Shuo; Zheng, Wei; Si, You Tao; Yuan, Zhi Peng; Lin, Wei Sheng; Yang, Yu Sheng
2017-01-01
To study the effects of nitrogen deposition on the concentration and spectral characteristics of dissolved organic matter (DOM) in the forest soil solution from the subtropical Cunninghamia lanceolata plantation, using negative pressure sampling method, the dynamics of DOM in soil solutions from 0-15 and 15-30 cm soil layer was monitored for two years and the spectroscopic features of DOM were analyzed. The results showed that nitrogen deposition significantly reduced the concentration of dissolved organic carbon (DOC), and increased the aromatic index (AI) and the humic index (HIX), but had no significant effect on dissolved organic nitrogen (DON) concentration in both soil layers. There was obvious seasonal variation in DOM concentration of the soil solution, which was prominently higher in summer and autumn than in spring and winter.Fourier-transform infrared (FTIR) absorption spectrometry indicated that the DOM in forest soil solution had absorption peaks in the similar position of six regions, being the highest in wave number of 1145-1149 cm -1 . Three-dimensional fluorescence spectra indicated that DOM was mainly consisted of protein-like substances (Ex/Em=230 nm/300 nm) and microbial degradation products (Ex/Em=275 nm/300 nm). The availability of protein-like substances from 0-15 cm soil layer was reduced in the nitrogen treatments. Nitrogen deposition significantly reduced the concentration of DOC in soil solution, maybe largely by reducing soil pH, inhibiting soil carbon mineralization and stimulating plant growth. In particular, the decline of DOC concentration in the surface layer was due to the production inhibition of the protein-like substances and carboxylic acids. Short-term nitrogen deposition might be beneficial to the maintenance of soil fertility, while the long-term accumulation of nitrogen deposition might lead to the hard utilization of soil nutrients.
17. Soil biochemical properties of grassland ecosystems under anthropogenic emission of nitrogen compounds
Science.gov (United States)
Kudrevatykh, Irina; Ivashchenko, Kristina; Ananyeva, Nadezhda
2016-04-01
Inflow of pollutants in terrestrial ecosystems nowadays increases dramatically, that might be led to disturbance of natural biogeochemical cycles and landscapes structure. Production of nitrogen fertilizers is one of the air pollution sources, namely by nitrogen compounds (NH4+, NO3-, NO2-). Air pollution by nitrogen compounds of terrestrial ecosystems might be affected on soil biochemical properties, which results increasing mineral nitrogen content in soil, changing soil P/N and Al/Ca ratios, and, finally, the deterioration of soil microbial community functioning. The research is focused on the assessment of anthropogenic emission of nitrogen compounds on soil properties of grassland ecosystems in European Russia. Soil samples (Voronic Chernozem Pachic, upper 10 cm mineral layer, totally 10) were taken from grassland ecosystem: near (5-10 m) nitrogen fertilizer factory (NFF), and far from it (20-30 km, served as a control) in Tula region. In soil samples the NH4+ and NO3- (Kudeyarov's photocolorimetric method), P, Ca, Al (X-ray fluorescence method) contents were measured. Soil microbial biomass carbon (Cmic) was analyzed by substrate-induced respiration method. Soil microbial respiration (MR) was assessed by CO2 rate production. Soil microbial metabolic quotient (qCO2) was calculated as MR/Cmic ratio. Near NFF the soil ammonium and nitrate nitrogen contents were a strongly varied, variation coefficient (CV) was 42 and 86This study was supported by Russian Foundation of Basic Research Grant No. 14-04-00098, 15-44-03220, 15-04-00915.
18. PENETRATION OF NITROGEN INTO WATER AS A RESULT OF FERTILIZATION OF LIGHT SOIL
Directory of Open Access Journals (Sweden)
Franciszek Czyżyk
2014-10-01
Full Text Available In this article there are present the results of six-year study of infiltration of nitrogen through the sand soil (loamy sand. Every year the soil was fertilized by compost (from sewage sludge and equivalent doses of nitrogen in mineral fertilizers. Two variants of compost fertilization (K1-10 and K2-15 g N·m-2 were used. Additionally two variants of NPK with equivalent doses of nitrogen as an ammonium nitrate supplemented with PK as a superphosphate and potassium salt were applied. Systematically there were investigated the volume of all leachates and their chemical composition. With increasing doses of fertilizers the concentrations of total nitrogen and nitrate nitrogen in the leachate were increased. The concentration of nitrogen in the leachate from the soil fertilized by nitrate was much greater than in compost with equivalent dose of nitrogen. Not only nitrates but also nitrogen from soluble organic compounds were rinsed from the soil. In the case of soil fertilized by compost the participation of nitrates in the total value of nitorgen in the leachate was 41-77%. However in the case of fertilization by ammonium sulphate this proportion was significantly higher and was in the range 60-95%. Over the years, a systematic soil fertilization by both ways increased the nitrogen concentrations in leachate. It shows that in the soil there is surplus of nitrogen, increasing during the time.
19. Nitrification and nitrogen mineralization in agricultural soils contaminated by copper mining activities in Central Chile
OpenAIRE
Moya, Héctor; Verdejo, José; Yáñez, Carolina; Álvaro, Juan E.; Sauvé, Sébastien; Neaman, Alexander
2017-01-01
Microbiological bioassays of nitrification and nitrogen mineralization have been used for evaluation of soil quality on metal-contaminated soils. We evaluated the effectiveness of nitrification and nitrogen mineralization bioassays as quality indicators of soil degradation caused by metal contamination. We performed standard tests based on protocols of ISO 14238 (2012) and ISO 15685 (2012) on 90 soil samples collected from agricultural areas in central Chile that were historically contaminate...
20. Permafrost carbon−climate feedback is sensitive to deep soil carbon decomposability but not deep soil nitrogen dynamics
Science.gov (United States)
Koven, Charles D.; Lawrence, David M.; Riley, William J.
2015-01-01
Permafrost soils contain enormous amounts of organic carbon whose stability is contingent on remaining frozen. With future warming, these soils may release carbon to the atmosphere and act as a positive feedback to climate change. Significant uncertainty remains on the postthaw carbon dynamics of permafrost-affected ecosystems, in particular since most of the carbon resides at depth where decomposition dynamics may differ from surface soils, and since nitrogen mineralized by decomposition may enhance plant growth. Here we show, using a carbon−nitrogen model that includes permafrost processes forced in an unmitigated warming scenario, that the future carbon balance of the permafrost region is highly sensitive to the decomposability of deeper carbon, with the net balance ranging from 21 Pg C to 164 Pg C losses by 2300. Increased soil nitrogen mineralization reduces nutrient limitations, but the impact of deep nitrogen on the carbon budget is small due to enhanced nitrogen availability from warming surface soils and seasonal asynchrony between deeper nitrogen availability and plant nitrogen demands. Although nitrogen dynamics are highly uncertain, the future carbon balance of this region is projected to hinge more on the rate and extent of permafrost thaw and soil decomposition than on enhanced nitrogen availability for vegetation growth resulting from permafrost thaw. PMID:25775603
1. Modelling soil nitrogen: The MAGIC model with nitrogen retention linked to carbon turnover using decomposer dynamics
International Nuclear Information System (INIS)
Oulehle, F.; Cosby, B.J.; Wright, R.F.; Hruška, J.; Kopáček, J.; Krám, P.; Evans, C.D.; Moldan, F.
2012-01-01
We present a new formulation of the acidification model MAGIC that uses decomposer dynamics to link nitrogen (N) cycling to carbon (C) turnover in soils. The new model is evaluated by application to 15–30 years of water chemistry data at three coniferous-forested sites in the Czech Republic where deposition of sulphur (S) and N have decreased by >80% and 40%, respectively. Sulphate concentrations in waters have declined commensurately with S deposition, but nitrate concentrations have shown much larger decreases relative to N deposition. This behaviour is inconsistent with most conceptual models of N saturation, and with earlier versions of MAGIC which assume N retention to be a first-order function of N deposition and/or controlled by the soil C/N ratio. In comparison with earlier versions, the new formulation more correctly simulates observed short-term changes in nitrate leaching, as well as long-term retention of N in soils. The model suggests that, despite recent deposition reductions and recovery, progressive N saturation will lead to increased future nitrate leaching, ecosystem eutrophication and re-acidification. - Highlights: ► New version of the biogeochemical model MAGIC developed to simulate C/N dynamics. ► New formulation of N retention based directly on the decomposer processes. ► The new formulation simulates observed changes in nitrate leaching and in soil C/N. ► The model suggests progressive N saturation at sites examined. ► The model performance meets a growing need for realistic process-based simulations. - Process-based modelling of nitrogen dynamics and acidification in forest ecosystems.
2. Nitrogen transport, transformation, and retention in the Three Gorges Reservoir : A mass balance approach
NARCIS (Netherlands)
Ran, Xiangbin; Bouwman, Lex; Yu, Zhigang; Beusen, Arthur; Chen, Hongtao; Yao, Qingzhen
2017-01-01
Dam construction in river systems affects the biogeochemistry of nitrogen (N), yet most studies on N cycling in reservoirs do not consider the transformations and retention of the different N species. This study addresses the N inputs, transport, transformations, and retention in the Three Gorges
3. Experience of application of the general-purpose pressure and pressure drop transformers on nitrogen tetroxide
International Nuclear Information System (INIS)
Grishchuk, M.Kh.
1979-01-01
An experience of application of the general-purpose pressure and pressure drop transformers at the Nuclear Power Engineering Institute of the BSSR Academy of Sciences for measurements on nitrogen tetroxide has been described. The concrete recommendations on the types of transformers and the volume of preparational work before putting them into operation have been given
4. Restoration using Azolla imbricata increases nitrogen functional bacterial groups and genes in soil.
Science.gov (United States)
Lu, Xiao-Ming; Lu, Peng-Zhen; Yang, Ke
2017-05-01
Microbial groups are major factors that influence soil function. Currently, there is a lack of studies on microbial functional groups. Although soil microorganisms play an important role in the nitrogen cycle, systematic studies of the effects of environmental factors on microbial populations in relation to key metabolic processes in the nitrogen cycle are seldom reported. In this study, we conducted a systematic analysis of the changes in nitrogen functional groups in mandarin orange garden soil treated with Azolla imbricata. The structures of the major functional bacterial groups and the functional gene abundances involved in key processes of the soil nitrogen cycle were analyzed using high-throughput sequencing (HTS) and quantitative real-time PCR, respectively. The results indicated that returning A. imbricata had an important influence on the composition of soil nitrogen functional bacterial communities. Treatment with A. imbricata increased the diversity of the nitrogen functional bacteria. The abundances of nitrogen functional genes were significantly higher in the treated soil compared with the control soil. Both the diversity of the major nitrogen functional bacteria (nifH bacteria, nirK bacteria, and narG bacteria) and the abundances of nitrogen functional genes in the soil showed significant positive correlations with the soil pH, the organic carbon content, available nitrogen, available phosphorus, and NH 4 + -N and NO 3 - -N contents. Treatment with 12.5 kg fresh A. imbricata per mandarin orange tree was effective to improve the quality of the mandarin orange garden soil. This study analyzed the mechanism of the changes in functional bacterial groups and genes involved in key metabolic processes of the nitrogen cycle in soil treated by A. imbricata.
5. Competition for nitrogen between Fagus sylvatica and Acer pseudoplatanus seedlings depends on soil nitrogen availability
Directory of Open Access Journals (Sweden)
Xiuyuan eLi
2015-04-01
Full Text Available Competition for nitrogen (N, particularly in resource-limited habitats, might be avoided by different N acquisition strategies of plants. In our study, we investigated whether slow-growing European beech and fast-growing sycamore maple seedlings avoid competition for growth-limiting N by different N uptake patterns and the potential alteration by soil N availability in a microcosm experiment. We quantified growth and biomass indices, 15N uptake capacity and N pools in the fine roots. Overall, growth indices, N acquisition and N pools in the fine roots were influenced by species-specific competition depending on soil N availability. With interspecific competition, growth of sycamore maple reduced regardless of soil N supply, whereas beech only showed reduced growth when N was limited. Both species responded to interspecific competition by alteration of N pools in the fine roots; however, sycamore maple showed a stronger response compared to beech for almost all N pools in roots, except for structural N at low soil N availability. Beech generally preferred organic N acquisition while sycamore maple took up more inorganic N. Furthermore, with interspecific competition, beech had an enhanced organic N uptake capacity, while in sycamore maple inorganic N uptake capacity was impaired by the presence of beech. Although sycamore maple could tolerate the suboptimal conditions at the cost of reduced growth, our study indicates its reduced competitive ability for N compared to beech.
6. Nitrogen turnover of three different agricultural soils determined by 15N triple labelling
Science.gov (United States)
Fiedler, Sebastian R.; Kleineidam, Kristina; Strasilla, Nicol; Schlüter, Steffen; Reent Köster, Jan; Well, Reinhard; Müller, Christoph; Wrage-Mönnig, Nicole
2017-04-01
To meet the demand for data to improve existing N turnover models and to evaluate the effect of different soil physical properties on gross nitrogen (N) transformation rates, we investigated two arable soils and a grassland soil after addition of ammonium nitrate (NH4NO3), where either ammonium (NH4+), or nitrate (NO3-), or both pools have been labelled with 15N at 60 atom% excess (triple 15N tracing method). Besides NH4+, NO3- and nitrite (NO2-) contents with their respective 15N enrichment, nitrous oxide (N2O) and dinitrogen (N2) fluxes have been determined. Each soil was adjusted to 60 % of maximum water holding capacity and pre-incubated at 20˚ C for two weeks. After application of the differently labelled N fertilizer, the soils were further incubated at 20˚ C under aerobic conditions in a He-N2-O2 atmosphere (21 % O2, 76 He, 2% N2) to increase the sensitivity of N2 rates via the 15N gas flux method. Over a 2 week period soil N pools were quantified by 2 M KCl extraction (adjusted to pH 7 to prevent nitrite losses) (Stevens and Laughlin, 1995) and N gas fluxes were measured by gas chromatography in combination with IRMS. Here, we present the pool sizes and fluxes as well as the 15N enrichments during the study. Results are discussed in light of the soil differences that were responsible for the difference in gross N dynamics quantified by the 15N tracing model Ntrace (Müller et al., 2007). References Müller, C., T. Rütting, J. Kattge, R.J. Laughlin, and R.J. Stevens, (2007) Estimation of parameters in complex 15N tracing models by Monte Carlo sampling. Soil Biology & Biochemistry. 39(3): p. 715-726. Stevens, R.J. and R.J. Laughlin, (1995) Nitrite transformations during soil extraction with potassium chloride. Soil Science Society of America Journal. 59(3): p. 933-938.
7. Identification of TNT Transformation Products in Soil
Science.gov (United States)
1992-06-01
Unannounced 0 Just i•icatio BYDlstrtbton, --.- Availabilit ? CodoeS Dist Special moI QUA=~lI3E1 3 ii CONTENTS Preface...extracted. Soil-to-solvent ratios varied from 1:2 to (Jenkins et al. 1989) and water (Jenkins et al. 1986, 1:5 (mass [g]:volume [mL]); the smallest...cultures, composting systems and MassSelectiveDetector (MSD) throughaHewlett- water , little research has been conducted to define Packard 5890 Series
8. Hydrologic control on redox and nitrogen dynamics in a peatland soil
Energy Technology Data Exchange (ETDEWEB)
Rubol, Simonetta, E-mail: [email protected] [Dipartimento di Ingegneria Civile ed Ambientale, Universita di Trento, Via Mesiano 77, I 38123 Trento (Italy); Silver, Whendee L. [Department of Environmental Science, Policy, and Management, 130 Mulford Hall, University of California, Berkeley, CA, 94720 (United States); Bellin, Alberto [Dipartimento di Ingegneria Civile ed Ambientale, Universita di Trento, Via Mesiano 77, I 38123 Trento (Italy)
2012-08-15
Soils are a dominant source of nitrous oxide (N{sub 2}O), a potent greenhouse gas. However, the complexity of the drivers of N{sub 2}O production and emissions has hindered our ability to predict the magnitude and spatial dynamics of N{sub 2}O fluxes. Soil moisture can be considered a key driver because it influences oxygen (O{sub 2}) supply, which feeds back on N{sub 2}O sources (nitrification versus denitrification) and sinks (reduction to dinitrogen). Soil water content is directly linked to O{sub 2} and redox potential, which regulate microbial metabolism and chemical transformations in the environment. Despite its importance, only a few laboratory studies have addressed the effects of hydrological transient dynamics on nitrogen (N) cycling in the vadose zone. To further investigate these aspects, we performed a long term experiment in a 1.5 m depth soil column supplemented by chamber experiments. With this experiment, we aimed to investigate how soil moisture dynamics influence redox sensitive N cycling in a peatland soil. As expected, increased soil moisture lowered O{sub 2} concentrations and redox potential in the soil. The decline was more severe for prolonged saturated conditions than for short events and at deep than at the soil surface. Gaseous and dissolved N{sub 2}O, dissolved nitrate (NO{sub 3}{sup -}) and ammonium (NH{sub 4}{sup +}) changed considerably along the soil column profile following trends in soil O{sub 2} and redox potential. Hot spots of N{sub 2}O concentrations corresponded to high variability in soil O{sub 2} in the upper and lower parts of the column. Results from chamber experiments confirmed high NO{sub 3}{sup -} reduction potential in soils, particularly from the bottom of the column. Under our experimental conditions, we identified a close coupling of soil O{sub 2} and N{sub 2}O dynamics, both of which lagged behind soil moisture changes. These results highlight the relationship among soil hydrologic properties, redox potential
9. Fertilizer nitrogen fixation in plants and its transmutation in soils in case of annual application
International Nuclear Information System (INIS)
Shilova, E.I.; Smirnov, P.M.; Khon, N.I.
1974-01-01
Using certain combinations of 15 N labeled and unlabeled nitrogen-containing fertilizers data were obtained for direct determination of nitrogen balance in the year of fertilization and subsequently. Annual and total (for 3 years) increment in utilization of soil nitrogen resulting from repeated fertilization was also determined. Coefficient of nitrogen utilization by barley decreased over the 3-year period after additional application of ammonium sulfate while biological immobilization of nitrogen tended to increase. Application of straw during the first year of the experiment did not significantly affect the nitrogen balance in the following years. The total coefficient of nitrogen utilization for the 2 to 3-year period was higher than that of the first year while biological immobilization was relatively lower. Additional utilization of soil nitrogen as compared to the control was the same over the whole 3-year period; additional mobilization (annual and total) was relatively higher due to lower removal of soil nitrogen in the subsequent years. Utilization of previously immobilized nitrogen was higher in the case of repeated fertilization than without application of nitrogen fertilizers. The content of newly immobilized nitrogen during 3 years in the hydrolyzable undistilable fraction (nitrogen of bounded amino acids) was relatively lower and this was accompanied by the growth of hydrolyzable distilable and unhydrolyzable nitrogen
10. Nitrogen Transformation and Removal in Horizontal Surface Flow ...
African Journals Online (AJOL)
The potential use of Constructed Mangrove Wetlands (CMWs) as a cheaper, effective and appropriate method for Nitrogen removal from domestic sewage of coastal zone in peri-urban cities was investigated from August 2007 to. September, 2008. Field investigations were made on horizontal surface flow constructed ...
11. Transformation of saturated nitrogen-containing heterocyclic compounds by microorganisms.
Science.gov (United States)
Parshikov, Igor A; Silva, Eliane O; Furtado, Niege A J C
2014-02-01
The saturated nitrogen-containing heterocyclic compounds include many drugs and compounds that may be used as synthons for the synthesis of other pharmacologically active substances. The need for new derivatives of saturated nitrogen-containing heterocycles for organic synthesis, biotechnology and the pharmaceutical industry, including optically active derivatives, has increased interest in microbial synthesis. This review provides an overview of microbial technologies that can be valuable to produce new derivatives of saturated nitrogen-containing heterocycles, including hydroxylated derivatives. The chemo-, regio- and enantioselectivity of microbial processes can be indispensable for the synthesis of new compounds. Microbial processes carried out with fungi, including Beauveria bassiana, Cunninghamella verticillata, Penicillium simplicissimum, Aspergillus niger and Saccharomyces cerevisiae, and bacteria, including Pseudomonas sp., Sphingomonas sp. and Rhodococcus erythropolis, biotransform many substrates efficiently. Among the biological activities of saturated nitrogen-containing heterocyclic compounds are antimicrobial, antitumor, antihypertensive and anti-HIV activities; some derivatives are effective for the treatment and prevention of malaria and trypanosomiasis, and others are potent glycosidase inhibitors.
12. [Effects of elevated atmospheric CO2 and nitrogen application on cotton biomass, nitrogen utilization and soil urease activity].
Science.gov (United States)
Lyu, Ning; Yin, Fei-hu; Chen, Yun; Gao, Zhi-jian; Liu, Yu; Shi, Lei
2015-11-01
In this study, a semi-open-top artificial climate chamber was used to study the effect of CO2 enrichment (360 and 540 µmol · mol(-1)) and nitrogen addition (0, 150, 300 and 450 kg · hm(-2)) on cotton dry matter accumulation and distribution, nitrogen absorption and soil urease activity. The results showed that the dry matter accumulation of bud, stem, leaf and the whole plant increased significantly in the higher CO2 concentration treatment irrespective of nitrogen level. The dry matter of all the detected parts of plant with 300 kg · hm(-2) nitrogen addition was significantly higher than those with the other nitrogen levels irrespective of CO2 concentration, indicating reasonable nitrogen fertilization could significantly improve cotton dry matter accumulation. Elevated CO2 concentration had significant impact on the nitrogen absorption contents of cotton bud and stem. Compared to those under CO2 concentration of 360 µmol · mol(-1), the nitrogen contents of bud and stem both increased significantly under CO2 concentration of 540 µmol · mol(-1). The nitrogen content of cotton bud in the treatment of 300 kg · hm(-2) nitrogen was the highest among the four nitrogen fertilizer treatments. While the nitrogen contents of cotton stem in the treatments of 150 kg · hm(-2) and 300 kg · hm(-2) nitrogen levels were higher than those in the treatment of 0 kg · hm(-2) and 450 kg · hm(-2) nitrogen levels. The nitrogen content of cotton leaf was significantly influenced by the in- teraction of CO2 elevation and N addition as the nitrogen content of leaf increased in the treatments of 0, 150 and 300 kg · hm(-2) nitrogen levels under the CO2 concentration of 540 µmol · mol(-1). The nitrogen content in cotton root was significantly increased with the increase of nitrogen fertilizer level under elevated CO2 (540 µmol · mol(-1)) treatment. Overall, the cotton nitrogen absorption content under the elevated CO2 (540 µmol · mol(-1)) treatment was higher than that
13. Origin, distribution and transformation of authigenic carbonates in loessic soils
Directory of Open Access Journals (Sweden)
Martin Kolesár
2015-01-01
Full Text Available Processes of authigenic carbonates formation are component part of terrestrial biogeochemical cycle of carbon, which starts with co-accumulation of oxalic acid and Ca in Ca- oxalates. After plant decay are these biominerals slowly transformed under the influence of microbial processes into authigenic carbonates (calcites, depending on soil condition. The formation of authigenic calcites runs over in soil system where is rather high Ca and Mg concentration, presence of oxalomorphic plants and sufficient oxalotrophic stability of microorganisms. In addition to Ca-oxalates, Ca and Mg ions necessary for carbonate formation comes also from air (precipitation, dust, mineral weathering, subsurface water flow and decaying organic matter. The distribution pattern of authigenic calcites with depth, the size and shape of individual forms of calcites on loessic soils of SW Slovakia, as it is resulted from micromorphological study indicate that through the historical development of that soils as landscape units, soil water regime has played decisive role at vertical redistribution of forms (size, shape of authigenic calcites. To this witness the depth of variation of needle calcite zones and horizons of micritic calcites occurrence depending on soil types (leaching. Needle shape calcite zones which approach closest to the soil surface, gradually coalescence to the horizons of micritic calcites with the depth. Micritic calcites are without, or with microsparitic domains. Our study concurrently support the ideas of their inorganic origin depending on evaporitic soil regime. This formations have its own historic dynamics on which depends also the preservation of calcaric nature of soils.
14. Organic carbon, nitrogen and phosphorus contents of some soils of kaliti tea-estate, Bangladesh
International Nuclear Information System (INIS)
Ahmed, M. S.; Shahin, M. M. H.; Sanaullah, A. F. M.
2005-01-01
Some soil samples were collected from Kaliti Tea-Estate of Moulvibazar district, Bangladesh. Total nitrogen, organic carbon, organic matter, carbon-nitrogen ratio and available phosphorus content of the collected soil samples of different depths and of different topographic positions have been determined. Total nitrogen was found 0.07 to 0.12 % organic carbon and organic matter content found to vary from 0.79 to 1.25 and 1.36 to 2.15 % respectively. Carbon-nitrogen ratio of these soils varied from 9.84 to 10.69, while available phosphorus content varied from 2.11 to 4.13 ppm. (author)
15. Clinoptilolite zeolite influence on inorganic nitrogen in silt loam and sandy agricultural soils
Science.gov (United States)
Development of best management practices can help improve inorganic nitrogen (N) availability to plants and reduce nitrate-nitrogen (NO3-N) leaching in soils. This study was conducted to determine the influence of the zeolite mineral Clinoptilolite (CL) additions on NO3-N and ammonium-nitrogen (NH4...
16. Clinoptilolite zeolite influence on nitrogen in a manure-amended sandy agricultural soil
Science.gov (United States)
Development of best management practices can help improve inorganic nitrogen (N) availability to plants and reduce nitrate-nitrogen (NO3-N) leaching in soils. This study was conducted to determine the influence of the zeolite mineral clinoptilolite (CL) additions on NO3-N and ammonium-nitrogen (NH4-...
17. Effects of mapped variation in soil conditions on estimates of soil carbon and nitrogen stocks for South America
NARCIS (Netherlands)
Batjes, N.H.
2000-01-01
Organic carbon and total nitrogen stocks for South America are computed using four 1:5,000,000 scale soil data sets of different spatial resolution. These are the 60' by 60' resolution Zobler soil data file, the 30' by 30' resolution World Inventory of Soil Emission Potentials (WISE) database, a 5'
18. Characterizing the transformation and transfer of nitrogen during the aerobic treatment of organic wastes and digestates
Energy Technology Data Exchange (ETDEWEB)
Zeng Yang, E-mail: [email protected] [Irstea, UR GERE, 17 avenue de Cucille, CS 64427, F-35044 Rennes Cedex (France); Universite Europeenne de Bretagne, F-35000 Rennes (France); Guardia, Amaury de; Daumoin, Mylene; Benoist, Jean-Claude [Irstea, UR GERE, 17 avenue de Cucille, CS 64427, F-35044 Rennes Cedex (France)
2012-12-15
Highlights: Black-Right-Pointing-Pointer Ammonia emissions varied depending on the nature of wastes and the treatment conditions. Black-Right-Pointing-Pointer Nitrogen losses resulted from ammonia emissions and nitrification-denitrification. Black-Right-Pointing-Pointer Ammonification can be estimated from biodegradable carbon and carbon/nitrogen ratio. Black-Right-Pointing-Pointer Ammonification was the main process contributing to N losses. Black-Right-Pointing-Pointer Nitrification rate was negatively correlated to stripping rate of ammonia nitrogen. - Abstract: The transformation and transfer of nitrogen during the aerobic treatment of seven wastes were studied in ventilated air-tight 10-L reactors at 35 Degree-Sign C. Studied wastes included distinct types of organic wastes and their digestates. Ammonia emissions varied depending on the kind of waste and treatment conditions. These emissions accounted for 2-43% of the initial nitrogen. Total nitrogen losses, which resulted mainly from ammonia emissions and nitrification-denitrification, accounted for 1-76% of the initial nitrogen. Ammonification was the main process responsible for nitrogen losses. An equation which allows estimating the ammonification flow of each type of waste according to its biodegradable carbon and carbon/nitrogen ratio was proposed. As a consequence of the lower contribution of storage and leachate rates, stripping and nitrification rates of ammonia nitrogen were negatively correlated. This observation suggests the possibility of promotingnitrification in order to reduce ammonia emissions.
19. The transformation of nitrogen during pressurized entrained-flow pyrolysis of Chlorella vulgaris.
Science.gov (United States)
Maliutina, Kristina; Tahmasebi, Arash; Yu, Jianglong
2018-08-01
The transformation of nitrogen in microalgae during entrained-flow pyrolysis of Chlorella vulgaris was systematically investigated at the temperatures of 600-900 °C and pressures of 0.1-4.0 MPa. It was found that pressure had a profound impact on the transformation of nitrogen during pyrolysis. The nitrogen retention in bio-char and its content in bio-oil reached a maximum value at 1.0 MPa. The highest conversion of nitrogen (50.25 wt%) into bio-oil was achieved at 1.0 MPa and 800 °C, which was about 7 wt% higher than that at atmospheric pressure. Higher pressures promoted the formation of pyrrolic-N (N-5) and quaternary-N (N-Q) compounds in bio-oil at the expense of nitrile-N and pyridinic-N (N-6) compounds. The X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results on bio-chars clearly evidenced the transformation of N-5 structures into N-6 and N-Q structures at elevated pressures. The nitrogen transformation pathways during pyrolysis of microalgae were proposed and discussed. Copyright © 2018 Elsevier Ltd. All rights reserved.
20. Differences in microbial community structure and nitrogen cycling in natural and drained tropical peatland soils.
Science.gov (United States)
Espenberg, Mikk; Truu, Marika; Mander, Ülo; Kasak, Kuno; Nõlvak, Hiie; Ligi, Teele; Oopkaup, Kristjan; Maddison, Martin; Truu, Jaak
2018-03-16
Tropical peatlands, which play a crucial role in the maintenance of different ecosystem services, are increasingly drained for agriculture, forestry, peat extraction and human settlement purposes. The present study investigated the differences between natural and drained sites of a tropical peatland in the community structure of soil bacteria and archaea and their potential to perform nitrogen transformation processes. The results indicate significant dissimilarities in the structure of soil bacterial and archaeal communities as well as nirK, nirS, nosZ, nifH and archaeal amoA gene-possessing microbial communities. The reduced denitrification and N 2 -fixing potential was detected in the drained tropical peatland soil. In undisturbed peatland soil, the N 2 O emission was primarily related to nirS-type denitrifiers and dissimilatory nitrate reduction to ammonium, while the conversion of N 2 O to N 2 was controlled by microbes possessing nosZ clade I genes. The denitrifying microbial community of the drained site differed significantly from the natural site community. The main reducers of N 2 O were microbes harbouring nosZ clade II genes in the drained site. Additionally, the importance of DNRA process as one of the controlling mechanisms of N 2 O fluxes in the natural peatlands of the tropics revealed from the results of the study.
1. Nitrogen transformations in response to temperature and rainfall manipulation in oak savanna: A global change experiment
Science.gov (United States)
Wellman, R. L.; Boutton, T. W.; Tjoelker, M. G.; Volder, A.; Briske, D. D.
2013-12-01
Increasing concentrations of greenhouse gases are projected to elevate global surface air temperatures by 1.1 to 6.4°C by the end of the century, and potentially magnify the intensity and variability of seasonal precipitation distribution. The mid-latitude grasslands of North America are predicted to experience substantial modification in precipitation regimes, with a shift towards drier summers and wetter spring and fall seasons. Despite these predictions, little is known concerning the effects of these global climate change drivers or their potential interactive effects on nitrogen (N) cycling processes. The purpose of this study is to quantify seasonal variation in rates of N-mineralization, nitrification, and N-losses via leaching in soil subjected to experimental warming and rainfall manipulation. Research was conducted at the Texas A&M Warming and Rainfall Manipulation (WaRM) Site in College Station where eight 9x18m rainout shelters and two unsheltered controls were established in post oak savanna in 2003. Replicate annual rainfall redistribution treatments (n = 4) are applied at the shelter level (long term mean vs. 40% of summer redistributed to fall and spring with same annual total). Warming treatments (ambient vs. 24-hr IR canopy warming of 1-3°C) were applied to planted monocultures of juniper and little bluestem, and a juniper-grass combination. Both juniper and little bluestem are key species within the post oak savanna region. Plots were sampled from the full factorial design during years six and seven of the WaRM experiment. Soil N-mineralization, nitrification, and N-losses via leaching were assessed quarterly for two years using the resin core incubation method. Rainfall, species composition, and time interacted significantly to influence both ammonification and nitrification. Highest rates of ammonification (0.115 mg NH4+ -N/ kg soil/day) occurred in grass monocultures during summer in the control rainfall plots, whereas highest rates of
2. Biological and Physicochemical Parameters Related to the Nitrogen Cycle in the Rhizospheric Soil of Native Potato (Solanum phureja Crops of Colombia
Directory of Open Access Journals (Sweden)
Nathalia Flórez-Zapata
2011-01-01
Full Text Available Nitrogen (N plays an important role in agricultural production. This study was designed to evaluate the presence of cultivable N cycle-associated microorganisms (nitrogen-fixing bacteria—NFB, proteolytic bacteria—PR, ammonifiers—AMO, ammonium-oxidizing bacteria—AOB, nitrite-oxidizing bacteria—NOB, and denitrifiers—DEN, and their relationship with physical-chemical and agronomic soil descriptors, in Solanum phureja rhizospheric soil samples, from traditional and organic crop management farms. A cluster analysis with the physical and chemical properties of soil, allowed to identify the organic matter content as an important factor that determines the outcome of that grouping. Significant differences (<0.05 between farms were found in the abundance of this groups, but correlation analysis showed that proteolytic and nitrogen fixing bacteria were the main nitrogen associated functional groups affected by soils' physical-chemical characteristics. The amount of ammonia available is affected by the agricultural management strategy, which consequently affects the NFB abundance. Finally the results showed that PR, protease activity and soil properties related with organic matter transformation has a positive relationship with productivity, which given the high organic matter content of the Andean soils being studied, we conclude that nitrogen mineralization process has an important role in the nitrogen cycle and its bioavailability in this ecosystem.
3. Biological and Physicochemical Parameters Related to the Nitrogen Cycle in the Rhizospheric Soil of Native Potato (Solanum phureja) Crops of Colombia
International Nuclear Information System (INIS)
Zapata, N.F; Velez, D.U
2011-01-01
Nitrogen (N) plays an important role in agricultural production. This study was designed to evaluate the presence of cultivable N cycle-associated microorganisms (nitrogen-fixing bacteria NFB, proteolytic bacteria PR, ammonifiers AMO, ammonium-oxidizing bacteria AOB, nitrite-oxidizing bacteria NOB, and denitrifiers DEN), and their relationship with physical-chemical and agronomic soil descriptors, in Solanum phureja rhizospheric soil samples, from traditional and organic crop management farms. A cluster analysis with the physical and chemical properties of soil, allowed to identify the organic matter content as an important factor that determines the outcome of that grouping. Significant differences (P<0.05) between farms were found in the abundance of this groups, but correlation analysis showed that proteolytic and nitrogen fixing bacteria were the main nitrogen associated functional groups affected by soils' physical-chemical characteristics. The amount of ammonia available is affected by the agricultural management strategy, which consequently affects the NFB abundance. Finally the results showed that PR, protease activity and soil properties related with organic matter transformation has a positive relationship with productivity, which given the high organic matter content of the Andean soils being studied, we conclude that nitrogen mineralization process has an important role in the nitrogen cycle and its bioavailability in this ecosystem.
4. [Effects of nitrogen and irrigation water application on yield, water and nitrogen utilization and soil nitrate nitrogen accumulation in summer cotton].
Science.gov (United States)
Si, Zhuan Yun; Gao, Yang; Shen, Xiao Jun; Liu, Hao; Gong, Xue Wen; Duan, Ai Wang
2017-12-01
A field experiment was carried out to study the effects of nitrogen and irrigation water application on growth, yield, and water and nitrogen use efficiency of summer cotton, and to develop the optimal water and nitrogen management model for suitable yield and less nitrogen loss in summer cotton field in the Huang-Huai region. Two experimental factors were arranged in a split plot design. The main plots were used for arranging nitrogen factor which consisted of five nitrogen fertilizer le-vels(0, 60, 120, 180, 240 kg·hm -2 , referred as N 0 , N 1 , N 2 , N 3 , N 4 ), and the subplots for irrigation factor which consisted of three irrigation quota levels (30, 22.5, 15 mm, referred as I 1 , I 2 , I 3 ). There were 15 treatments with three replications. Water was applied with drip irrigation system. Experimental results showed that both irrigation and nitrogen fertilization promoted cotton growth and yield obviously, but nitrogen fertilizer showed more important effects than irrigation and was the main factor of regulating growth and yield of summer cotton in the experimental region. With the increase of nitrogen fertilization rate and irrigation amount, the dry mater accumulation of reproductive organs, the above-ground biomass at the flowering-bolling stage and seed cotton yield increased gradually, reached peak values at nitrogen fertilization rate of 180 kg·hm -2 and decreased slowly with the nitrogen fertilization rate further increased. The maximum yield of 4016 kg·hm -2 was observed in the treatment of N 3 I 1 . Increasing nitrogen fertilizer amount would improve significantly total N absorption of shoots and N content of stem and leaf, but decrease nitrogen partial factor productivity. The maximum irrigation-water use efficiency of 5.40 kg·m -3 and field water use efficiency of 1.24 kg·m -3 were found in the treatments of N 3 I 3 and N 3 I 1 , respectively. With increasing nitrogen fertilization amount, soil NO 3 - -N content increased and the main soil
5. Soil microbial community and its interaction with soil carbon and nitrogen dynamics following afforestation in central China.
Science.gov (United States)
Deng, Qi; Cheng, Xiaoli; Hui, Dafeng; Zhang, Qian; Li, Ming; Zhang, Quanfa
2016-01-15
Afforestation may alter soil microbial community structure and function, and further affect soil carbon (C) and nitrogen (N) dynamics. Here we investigated soil microbial carbon and nitrogen (MBC and MBN) and microbial community [e.g. bacteria (B), fungi (F)] derived from phospholipid fatty acids (PLFAs) analysis in afforested (implementing woodland and shrubland plantations) and adjacent croplands in central China. Relationships of microbial properties with biotic factors [litter, fine root, soil organic carbon (SOC), total nitrogen (TN) and inorganic N], abiotic factors (soil temperature, moisture and pH), and major biological processes [basal microbial respiration, microbial metabolic quotient (qCO2), net N mineralization and nitrification] were developed. Afforested soils had higher mean MBC, MBN and MBN:TN ratios than the croplands due to an increase in litter input, but had lower MBC:SOC ratio resulting from low-quality (higher C:N ratio) litter. Afforested soils also had higher F:B ratio, which was probably attributed to higher C:N ratios in litter and soil, and shifts of soil inorganic N forms, water, pH and disturbance. Alterations in soil microbial biomass and community structure following afforestation were associated with declines in basal microbial respiration, qCO2, net N mineralization and nitrification, which likely maintained higher soil carbon and nitrogen storage and stability. Copyright © 2015 Elsevier B.V. All rights reserved.
6. Influence of natural zeolite and nitrification inhibitor on organics degradation and nitrogen transformation during sludge composting.
Science.gov (United States)
Zhang, Junya; Sui, Qianwen; Li, Kun; Chen, Meixue; Tong, Juan; Qi, Lu; Wei, Yuansong
2016-01-01
7. 15N abundance in Antarctica: origin of soil nitrogen and ecological implications
International Nuclear Information System (INIS)
Wada, E.; Shibata, R.; Torii, T
1981-01-01
The results of an investigation of the nitrogen cycle in Antartica are reported which show that nitrate in Antarctic soils is extremely depleted in 15 N compared with biogenic nitrogen and that algae collected from a nitrate-rich saline pond and from a penguin rookery exhibit, respectively, the lowest and the highest 15 N/ 14 N ratios among terrestrial biogenic nitrogen so far observed. The possible causes of these extreme nitrogen isotopic compositions are discussed. (U.K.)
8. Effects of wetland recovery on soil labile carbon and nitrogen in the Sanjiang Plain.
Science.gov (United States)
Huang, Jingyu; Song, Changchun; Nkrumah, Philip Nti
2013-07-01
Soil management significantly affects the soil labile organic factors. Understanding carbon and nitrogen dynamics is extremely helpful in conducting research on active carbon and nitrogen components for different kinds of soil management. In this paper, we examined the changes in microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), dissolved organic carbon (DOC), and dissolved organic nitrogen (DON) to assess the effect and mechanisms of land types, organic input, soil respiration, microbial species, and vegetation recovery under Deyeuxia angustifolia freshwater marshes (DAMs) and recovered freshwater marsh (RFM) in the Sanjiang Plain, Northeast China. Identifying the relationship among the dynamics of labile carbon, nitrogen, and soil qualification mechanism using different land management practices is therefore important. Cultivation and land use affect intensely the DOC, DON, MBC, and MBN in the soil. After DAM soil tillage, the DOC, DON, MBC, and MBN at the surface of the agricultural soil layer declined significantly. In contrast, their recovery was significant in the RFM surface soil. A long time was needed for the concentration of cultivated soil total organic carbon and total nitrogen to be restored to the wetland level. The labile carbon and nitrogen fractions can reach a level similar to that of the wetland within a short time. Typical wetland ecosystem signs, such as vegetation, microbes, and animals, can be recovered by soil labile carbon and nitrogen fraction restoration. In this paper, the D. angustifolia biomass attained natural wetland level after 8 years, indicating that wetland soil labile fractions can support wetland eco-function in a short period of time (4 to 8 years) for reconstructed wetland under suitable environmental conditions.
9. Understanding on Soil Inorganic Carbon Transformation in North China
Science.gov (United States)
Li, Guitong; Yang, Lifang; Zhang, Chenglei; Zhang, Hongjie
2015-04-01
Soil total carbon balance in long-term fertilization field experiments in North China Plain. Four long-term fertilization experiments (20-30 years) were investigated on SOC in 40 cm, calcium carbonate and active carbonate (AC) in 180 or 100 cm soil profile, δ13C values of SOC and δ13C and δ18O values of carbonate in soil profile, particle distribution of SOC and SIC in main soil layers, and ratios of pedogenic carbonate (PC) in SIC and C3-SOC in SOC. The most important conclusion is that fertilization of more than 20 years can produce detectable impact on pool size, profile distribution, ratio of active component and PC of SIC, which make it clear that SIC pool must be considered in the proper evaluation of the response of soil carbon balance to human activities in arid and semi-arid region. Land use impact on soil total carbon pool in Inner Mongolia. With the data of the second survey of soils in Inner Mongolia and the 58 soil profile data from Wu-lan-cha-bu-meng and Xi-lin-hao-te, combining with the 13C and 18O techniques, SIC density and stock in Inner Mongolia is estimated. The main conclusion is that soils in inner Mongolia have the same level of SOC and SIC, with the density in 100cm pedons of 8.97 kg•m-2 and 8.61 kg•m-2, respectively. Meanwhile, the significantly positive relationship between SOC and SIC in A layer indicates co-sequestration of SOC and SIC exist. Evaluation of the methods for measuring CA enzyme activity in soil. In laboratory, method in literature to measure CA activity in soil sample was repeated, and found it was not valid indeed. The failure could not attribute to the disturbance of common ions like NO3-, SO42-, Ca2+, and Mg2+. The adsorption of CA to soil material was testified as the main reason for that failure. A series of extractants were tested but no one can extract the adsorbed CA and be used in measuring CA activity in soil sample. Carbonate transformation in field with straw returned and biochar added. In 2009, a field
10. Soil nitrogen dynamics and Capsicum Annuum sp. plant response to biochar amendment in silt loam soil
Science.gov (United States)
Horel, Agota; Gelybo, Gyorgyi; Dencso, Marton; Toth, Eszter; Farkas, Csilla; Kasa, Ilona; Pokovai, Klara
2017-04-01
The present study investigated the growth of Capsicum Annuum sp. (pepper) in small-scale experiment to observe changes in plant growth and health as reflected by leaf area, plant height, yield, root density, and nitrogen usage. Based on field conditions, part of the study aimed to examine the photosynthetic and photochemical responses of plants to treatments resulting from different plant growth rates. During the 12.5 week long study, four treatments were investigated with biochar amount of 0, 0.5%, 2.5%, and 5.0% (by weight) added to silt loam soil. The plants were placed under natural environmental conditions, such that photosynthetic activities from photosynthetically active radiation (PAR) and the plants photochemical reflectance index (PRI) could be continuously measured after exposure to sunlight. In this study we found that benefits from biochar addition to silt loam soil most distinguishable occurred in the BC2.5 treatments, where the highest plant yield, highest root density, and highest leaf areas were observed compared to other treatments. Furthermore, data showed that too low (0.5%) or too high (5.0%) biochar addition to the soil had diminishing effects on Capsicum Annuum sp. growth and yield over time. At the end of the 12th week, BC2.5 had 22.2%, while BC0.5 and BC5.0 showed 17.4% and 15.7% increase in yield dry weight respectively compared to controls. The collected data also showed that the PRI values of plants growing on biochar treated soils were generally lower compared to control treatments, which could relate to leaf nitrogen levels. Total nitrogen amount showed marginal changes over time in all treatments. The total nitrogen concentration showed 28.6% and 17.7% increase after the 6th week of the experiment for BC2.5 and BC5.0, respectively, while inorganic nutrients of NO3-N and NH4+-N showed a continuous decrease during the course of the study, with a substantial drop during the first few weeks. The present study provides evidence for impact
11. Nitrogen deposition alters nitrogen cycling and reduces soil carbon content in low-productivity semiarid Mediterranean ecosystems
International Nuclear Information System (INIS)
Ochoa-Hueso, Raúl; Maestre, Fernando T.; Ríos, Asunción de los; Valea, Sergio; Theobald, Mark R.; Vivanco, Marta G.; Manrique, Esteban; Bowker, Mathew A.
2013-01-01
Anthropogenic N deposition poses a threat to European Mediterranean ecosystems. We combined data from an extant N deposition gradient (4.3–7.3 kg N ha −1 yr −1 ) from semiarid areas of Spain and a field experiment in central Spain to evaluate N deposition effects on soil fertility, function and cyanobacteria community. Soil organic N did not increase along the extant gradient. Nitrogen fixation decreased along existing and experimental N deposition gradients, a result possibly related to compositional shifts in soil cyanobacteria community. Net ammonification and nitrification (which dominated N-mineralization) were reduced and increased, respectively, by N fertilization, suggesting alterations in the N cycle. Soil organic C content, C:N ratios and the activity of β-glucosidase decreased along the extant gradient in most locations. Our results suggest that semiarid soils in low-productivity sites are unable to store additional N inputs, and that are also unable to mitigate increasing C emissions when experiencing increased N deposition. -- Highlights: •Soil organic N does not increase along the extant N deposition gradient. •Reduced N fixation is related to compositional shifts in soil cyanobacteria community. •Nitrogen cycling is altered by simulated N deposition. •Soil organic C content decrease along the extant N deposition gradient. •Semiarid soils are unable to mitigate CO 2 emissions after increased N deposition. -- N deposition alters N cycling and reduces soil C content in semiarid Mediterranean ecosystems
12. Nitrogen transformation and nitrous oxide emissions affected by biochar amendment and fertilizer stabilizers
Science.gov (United States)
Biochar as a soil amendment and the use of fertilizer stabilizers (N transformation inhibitors) have been shown to reduce N2O emissions, but the mechanisms or processes involved are not well understood. The objective of this research was to investigate N transformation processes and the relationship...
13. Combined climate factors alleviate changes in gross soil nitrogen dynamics in heathlands
DEFF Research Database (Denmark)
Bjorsne, Anna-Karin; Rutting, Tobias; Ambus, Per
2014-01-01
of exposure to three climate change factors, i.e. warming, elevated CO2 (eCO(2)) and summer drought, applied both in isolation and in combination. By conducting laboratory N-15 tracing experiments we show that warming increased both gross N mineralization and nitrification rates. In contrast, gross......The ongoing climate change affects biogeochemical cycling in terrestrial ecosystems, but the magnitude and direction of this impact is yet unclear. To shed further light on the climate change impact, we investigated alterations in the soil nitrogen (N) cycling in a Danish heathland after 5 years......CO(2). In the full treatment combination, simulating the predicted climate for the year 2075, gross N transformations were only moderately affected compared to control, suggesting a minor alteration of the N cycle due to climate change. Overall, our study confirms the importance of multifactorial field...
14. Improvement of wine terroir management according to biogeochemical cycle of nitrogen in soil
Science.gov (United States)
Najat, Nassr; Aude, Langenfeld; Mohammed, Benbrahim; Lionel, Ley; Laurent, Deliere; Jean-Pascal, Goutouly; David, Lafond; Marie, Thiollet-Scholtus
2015-04-01
Good wine terroir production implies a well-balanced Biogeochemical Cycle of Nitrogen (BCN) at field level i.e. in soil and in plant. Nitrogen is very important for grape quality and soil sustainability. The mineralization of organic nitrogen is the main source of mineral nitrogen for the vine. This mineralization depends mainly on the soil microbial activity. This study is focused on the functional microbial populations implicated in the BCN, in particular nitrifying bacteria. An experimental network with 6 vine sites located in Atlantic coast (Loire valley and Bordeaux) and in North-East (Alsace) of France has been set up since 2012. These vine sites represent a diversity of environmental factors (i.e. soil and climate). The adopted approach is based on the measure of several indicators to assess nitrogen dynamic in soil, i.e. nitrogen mineralization, regarding microbial biomass and activity. Statistical analyses are performed to determine the relationship between biological indicator and nitrogen mineralisation regarding farmer's practices. The variability of the BCN indicators seems to be correlated to the physical and chemical parameters in the soil of the field. For all the sites, the bacterial biomass is correlated to the rate and kinetic of nitrogen in soil, however this bioindicator depend also on others parameters. Moreover, the functional bacterial diversity depends on the soil organic matter content. Differences in the bacterial biomass and kinetic of nitrogen mineralization are observed between the sites with clayey (Loire valley site) and sandy soils (Bordeaux site). In some tested vine systems, effects on bacterial activity and nitrogen dynamic are also observed depending on the farmer's practices: soil tillage, reduction of inputs, i.e. pesticides and fertilizers, and soil cover management between rows. The BCN indicators seem to be strong to assess the dynamics of the nitrogen in various sites underline the functional diversity of the soils. These
15. Effect of blue-green algae on soil nitrogen | Paudel | African Journal ...
African Journals Online (AJOL)
Effect of blue-green algae on soil nitrogen. ... African Journal of Biotechnology ... In paddy fields, the death of algal biomass is most frequently associated with soil dessication at the end of the cultivation cycle and algal growth has frequently resulted in a gradual build up of soil fertility with a residual effect on succeeding crop ...
16. Burrowing herbivores alter soil carbon and nitrogen dynamics in a semi-arid ecosystem, Argentina
Science.gov (United States)
Kenneth L. Clark; Lyn C. Branch; Jose L. Hierro; Diego Villarreal
2016-01-01
Activities of burrowing herbivores, including movement of soil and litter and deposition of waste material, can alter the distribution of labile carbon (C) and nitrogen (N) in soil, affecting spatial patterning of nutrient dynamics in ecosystems where they are abundant. Their role in ecosystem processes in surface soil has been studied extensively, but effects of...
17. RESPONSE OF SOIL MICROBIAL BIOMASS AND COMMUNITY COMPOSITION TO CHRONIC NITROGEN ADDITIONS AT HARVARD FOREST
Science.gov (United States)
Soil microbial communities may respond to anthropogenic increases in ecosystem nitrogen (N) availability, and their response may ultimately feedback on ecosystem carbon and N dynamics. We examined the long-term effects of chronic N additions on soil microbes by measuring soil mi...
18. Reduced nitrogen leaching by intercropping maize with red fescue on sandy soils in North Europe
DEFF Research Database (Denmark)
Manevski, Kiril; Børgesen, Christen Duus; Andersen, Mathias Neumann
2015-01-01
Aim To study maize (Zea mays L.) growth and soil nitrogen (N) dynamics in monocrop and intercropped systems in a North European climate and soil conditions with the support of a simulation model. Methods Field data for 3 years at two sites/soil types in Denmark and three main factors: (i) cropping...
19. Nitrogen loss from grassland on peat soils through nitrous oxide production.
NARCIS (Netherlands)
Koops, J.G.; Beusichem, van M.L.; Oenema, O.
1997-01-01
Nitrous oxide (N2O) in soils is produced through nitrification and denitrification. The N2O produced is considered as a nitrogen (N) loss because it will most likely escape from the soil to the atmosphere as N2O or N2. Aim of the study was to quantify N2O production in grassland on peat soils in
20. Litter quality mediated nitrogen effect on plant litter decomposition regardless of soil fauna presence.
Science.gov (United States)
Zhang, Weidong; Chao, Lin; Yang, Qingpeng; Wang, Qingkui; Fang, Yunting; Wang, Silong
2016-10-01
Nitrogen addition has been shown to affect plant litter decomposition in terrestrial ecosystems. The way that nitrogen deposition impacts the relationship between plant litter decomposition and altered soil nitrogen availability is unclear, however. This study examined 18 co-occurring litter types in a subtropical forest in China in terms of their decomposition (1 yr of exposure in the field) with nitrogen addition treatment (0, 0.4, 1.6, and 4.0 mol·N·m -2 ·yr -1 ) and soil fauna exclusion (litter bags with 0.1 and 2 cm mesh size). Results showed that the plant litter decomposition rate is significantly reduced because of nitrogen addition; the strength of the nitrogen addition effect is closely related to the nitrogen addition levels. Plant litters with diverse quality responded to nitrogen addition differently. When soil fauna was present, the nitrogen addition effect on medium-quality or high-quality plant litter decomposition rate was -26% ± 5% and -29% ± 4%, respectively; these values are significantly higher than that of low-quality plant litter decomposition. The pattern is similar when soil fauna is absent. In general, the plant litter decomposition rate is decreased by soil fauna exclusion; an average inhibition of -17% ± 1.5% was exhibited across nitrogen addition treatment and litter quality groups. However, this effect is weakly related to nitrogen addition treatment and plant litter quality. We conclude that the variations in plant litter quality, nitrogen deposition, and soil fauna are important factors of decomposition and nutrient cycling in a subtropical forest ecosystem. © 2016 by the Ecological Society of America.
1. [Dynamic changes in functional genes for nitrogen bioremediation of petroleum-contaminated soil cycle during].
Science.gov (United States)
Wu, Bin-Bin; Lu, Dian-Nan; Liu, Zheng
2012-06-01
Microorganisms in nitrogen cycle serve as an important part of the ecological function of soil. The aim of this research was to monitor the abundance of nitrogen-fixing, denitrifying and nitrifying bacteria during bioaugmentation of petroleum-contaminated soil using real-time polymerase chain reaction (real-time PCR) of nifH, narG and amoA genes which encode the key enzymes in nitrogen fixation, nitrification and ammoniation respectively. Three different kinds of soils, which are petroleum-contaminated soil, normal soil, and remediated soil, were monitored. It was shown that the amounts of functional microorganisms in petroleum-contaminated soil were far less than those in normal soil, while the amounts in remediated soil and normal soil were comparable. Results of this experiment demonstrate that nitrogen circular functional bacteria are inhibited in petroleum-contaminated soil and can be recovered through bioremediation. Furthermore, copies of the three functional genes as well as total petroleum hydrocarbons (TPH) for soils with six different treatments were monitored. Among all treatments, the one, into which both E. cloacae as an inoculant and wheat straw as an additive were added, obtained the maximum copies of 2.68 x 10(6), 1.71 x 10(6) and 8.54 x 10(4) per gram dry soil for nifH, narG and amoA genes respectively, companying with the highest degradation rate (48% in 40 days) of TPH. The recovery of functional genes and removal of TPH were better in soil inoculated with E cloacae and C echinulata collectively than soil inoculated with E cloacae only. All above results suggest that the nitrogen circular functional genes could be applied to monitor and assess the bioremediation of petroleum-contaminated soil.
2. Modeling of Heavy Metal Transformation in Soil Ecosystem
Science.gov (United States)
Kalinichenko, Kira; Nikovskaya, Galina N.
2017-04-01
The intensification of industrial activity leads to an increase in heavy metals pollution of soils. In our opinion, sludge from biological treatment of municipal waste water, stabilized under aerobic-anaerobic conditions (commonly known as biosolid), may be considered as concentrate of natural soil. In their chemical, physical and chemical and biological properties these systems are similar gel-like nanocomposites. These contain microorganisms, humic substances, clay, clusters of nanoparticles of heavy metal compounds, and so on involved into heteropolysaccharides matrix. It is known that microorganisms play an important role in the transformation of different nature substances in soil and its health maintenance. The regularities of transformation of heavy metal compounds in soil ecosystem were studied at the model of biosolid. At biosolid swelling its structure changing (gel-sol transition, weakening of coagulation contacts between metal containing nanoparticles, microbial cells and metabolites, loosening and even destroying of the nanocomposite structure) can occur [1, 2]. The promotion of the sludge heterotrophic microbial activities leads to solubilization of heavy metal compounds in the system. The microbiological process can be realized in alcaligeneous or acidogeneous regimes in dependence on the type of carbon source and followed by the synthesis of metabolites with the properties of flocculants and heavy metals extragents [3]. In this case the heavy metals solubilization (bioleaching) in the form of nanoparticles of hydroxycarbonate complexes or water soluble complexes with oxycarbonic acids is observed. Under the action of biosolid microorganisms the heavy metals-oxycarbonic acids complexes can be transformed (catabolised) into nano-sizing heavy metals- hydroxycarbonates complexes. These ecologically friendly complexes and microbial heteropolysaccharides are able to interact with soil colloids, stay in the top soil profile, and improve soil structure due
3. [Runoff loss of soil mineral nitrogen and its relationship with grass coverage on Loess slope land].
Science.gov (United States)
Zhang, Yali; Li, Huai'en; Zhang, Xingchang; Xiao, Bo
2006-12-01
In a simulated rainfall experiment on Loess slope land, this paper determined the rainfall, surface runoff and the effective depth of interaction (EDI) between rainfall and soil mineral nitrogen, and studied the effects of grass coverage on the EDI and the runoff loss of soil mineral nitrogen. The results showed that with the increase of EDI, soil nitrogen in deeper layers could be released into surface runoff through dissolution and desorption. The higher the grass coverage, the deeper the EDI was. Grass coverage promoted the interaction between surface runoff and surface soil. On the slope land with 60%, 80% and 100% of grass coverage, the mean content of runoff mineral nitrogen increased by 34.52%, 32.67% and 6.00%, while surface runoff decreased by 4.72%, 9.84% and 12.89%, and eroded sediment decreased by 83.55%, 87.11% and 89.01%, respectively, compared with bare slope land. The total runoff loss of soil mineral nitrogen on the lands with 60%, 80%, and 100% of grass coverage was 95.73%, 109.04%, and 84.05% of that on bare land, respectively. Grass cover had dual effects on the surface runoff of soil mineral nitrogen. On one hand, it enhanced the influx of soil mineral nitrogen to surface runoff, and on the other hand, it markedly decreased the runoff, resulting in the decrease of soil mineral nitrogen loss through runoff and sediment. These two distinct factors codetermined the total runoff loss of soil mineral nitrogen.
4. The impact of post-fire salvage logging on microbial nitrogen cyclers in Mediterranean forest soil.
Science.gov (United States)
Pereg, Lily; Mataix-Solera, Jorge; McMillan, Mary; García-Orenes, Fuensanta
2018-04-01
Forest fires are a regular occurrence in the Mediterranean basin. High severity fires and post-fire management can affect biological, chemical and physical properties of soil, including the composition and abundance of soil microbial communities. Salvage logging is a post-fire management strategy, which involves the removal of burnt wood from land after a fire. The main objective of this work was to evaluate the impact of post-fire salvage logging and microaggregation on soil microbial communities, specifically on the abundance of nitrogen cyclers and, thus, the potential of the soil for microbial nitrogen cycling. The abundance of nitrogen cyclers was assessed by quantification of microbial nitrogen cycling genes in soil DNA, including nifH (involved in nitrogen fixation), nirS/K and nosZ (involved in denitrification), amoA-B and amoA-Arch (involved in bacterial and archaeal nitrification, respectively). It was demonstrated that salvage logging reduced bacterial load post-fire when compared to tree retention control and resulted in significant changes to the abundance of functional bacteria involved in nitrogen cycling. Microbial gene pools involved in various stages of the nitrogen cycle were larger in control soil than in soil subjected to post-fire salvage logging and were significantly correlated with organic matter, available phosphorous, nitrogen and aggregate stability. The microaggregate fraction of the soil, which has been associated with greater organic carbon, was shown to be a hotspot for nitrogen cyclers particularly under salvage logging. The impact of post-fire management strategies on soil microbial communities needs to be considered in relation to maintaining ecosystem productivity, resilience and potential impact on climate change. Copyright © 2017 Elsevier B.V. All rights reserved.
5. Nitrogen enrichment in runoff sediments as affected by soil texture in Beijing mountain area.
Science.gov (United States)
Yang, Yang; Ye, Zhihan; Liu, Baoyuan; Zeng, Xianqin; Fu, Suhua; Lu, Bingjun
2014-02-01
Enrichment ratio (ER) is widely used in nonpoint source pollution models to estimate the nutrient loss associated with soil erosion. The objective of this study was to determine the ER of total nitrogen (ERN) in the sediments eroded from the typical soils with varying soil textures in Beijing mountain area. Each of the four soils was packed into a 40 by 30 by 15 cm soil pan and received 40-min simulated rainfalls at the intensity of 90 mm h(-1) on five slopes. ERN for most sediments were above unity, indicating the common occurrence of nitrogen enrichment accompanied with soil erosion in Beijing mountain area. Soil texture was not the only factor that influenced N enrichment in this experiment since the ERN for the two fine-textured soils were not always lower. Soil properties such as soil structure might exert a more important influence in some circumstances. The selective erosion of clay particles was the main reason for N enrichment, as implied by the significant positive correlation between the ER of total nitrogen and clay fraction in eroded sediments. Significant regression equations between ERN and sediment yield were obtained for two pairs of soils, which were artificially categorized by soil texture. The one for fine-textured soils had greater intercept and more negative slope. Thus, the initially higher ERN would be lower than that for the other two soils with coarser texture once the sediment yield exceeded 629 kg ha(-1).
6. Calibration of Soil Available Nitrogen and Water Content with Grain Yield of Dry land Wheat
Directory of Open Access Journals (Sweden)
V. Feiziasl
2017-01-01
Full Text Available Introduction: Nitrogen (N is one of the most important growth-limiting nutrients for dryland wheat. Mineral nitrogen or ammonium (NH4+ and nitrate (NO3− are two common forms of inorganic nitrogen that can serve as limiting factors for plant growth. Nitrogen fertilization in dryland area can increase the use of soil moisture, and improve wheat yields to some extent. Many researchers have been confirmed interactions between water stress and nitrogen fertilizers on wheat, especially under field conditions. Because of water stress affects forms of nitrogen uptake that leads to disorder in plant metabolism, reduction in grain yield and crop quality in dryland condition. On the other hand, use of suitable methods for determining nitrogen requirement can increase dryland wheat production. However, nitrogen recommendations should be based on soil profile content or precipitation. An efficient method for nitrogen fertilizer recommendation involves choosing an effective soil extractant and calibrating soil nitrogen (Total N, NO3− andNH4+ tests against yield responses to applied nitrogen in field experiments. Soil testing enables initial N supply to be measured and N supply throughout the season due to mineralization to be estimated. This study was carried out to establish relationship between nitrogen forms (Total N, NO3− andNH4+ in soil and soil profile water content with plant response for recommendation of nitrogen fertilizer. Materials and Methods: This study was carried out in split-split plot in a RCBD in Dryland Agricultural Research Institute (DARI, Maragheh, Iranwhere N application times (fall, 2/3 in fall and 1/3 in spring were assigned to the main plots, N rates to sub plot (0, 30, 60 and 90 kg/ha, and 7 dryland wheat genotypes to sub-sub plots (Azar2, Ohadi, Rasad and 1-4 other genotypes in three replications in 2010-2011. Soil samples were collected from 0-20, 20-40, 40-60 and 60-80 cm in sub-sub plots in shooting stage (ZGS32. Ammonium
7. Nitrogen requirements of cassava in selected soils of Thailand
Directory of Open Access Journals (Sweden)
Jakchaiwat Kaweewong
2013-08-01
Full Text Available Cassava (Manihot esculenta is one of the most important export crops in Thailand, yet the nitrogen requirement is unknown and not considered by growers and producers. Cassava requirements for N were determined in field experiments during a period of four years and four sites on the Satuk (Suk, Don Chedi (Dc, Pak Chong (Pc,and Ban Beung (BBg soil series in Lopburi, Supanburi, Nakhon Ratchasima, and Chonburi sites, respectively. The fertilizer treatment structure comprised 0, 62.5, 125, 187.5, 250 and 312.5 kg N ha^(-1 as urea. At each site cassava was harvested at nine months and yield parameters and the minimum datasets were taken. The fertilizer rate which resulted in maximum yield ranged from 187.5 kg N ha^(-1 in Supanburi and Chonburi (fresh weight yield of 47,500 and 30,000 kg ha^(-1 respectively to 250 kg N ha^(-1 in Lopburi and Nakhon Ratchasima (fresh weight yield of 64,100 and 46,700 kg ha^(-1 respectively. Yield appeared to decrease at the higher, 312 kg ha^(-1, at Supanburi and Lopburi, and 250 kg ha^(-1 (Chonburi fertilizer N rates. Net revenue was 70.4 and 72.9 % higher than where no N was appliedLopburi and Nakhon Ratchasima sites. Net revenue at the Supanburi and Chonburi sites were 53.8 and 211.0 % higher than that where no N was applied. This study suggests that at all sites improved cassava production and net revenue could be obtained with the judicious application of higher quantities of N. The results provide needed guidance to nitrogen fertilization of the important industrial crop cassava in Thailand.
8. CLASSIFICATION OF ANTHROPOGENIC TRANSFORMATIONS SOILS URBOECOSYSTEMS OF DNEPROPETROVSK
Directory of Open Access Journals (Sweden)
YAKOVYSHYNA T.F.
2015-12-01
Full Text Available Raising of problem. The functioning of the city, as artificially created system of the result of the anthropogenic activity, promotes degradation and, sometimes, destruction of the environment, with change it to the technogenic replacement. First of all suffers the soil, as a basic component of any ecosystem, where the circulation of materials close, because it is a powerful biogeochemical barrier to their migration, able to deposit toxicants a long time through its protective functions. The leading role of the formation of the urban soil plays an anthropogenic factor, which is able to influence directly – the destruction of the soil profile due to construction activity and indirectly – with aerogenic or hydrogenous pollution xenobiotics contained in the emissions and discharges of the industrial enterprises; and it is determined by the type of economic use and history of area developing. The variability of using the urban soil is reflected in the soil profile and contributed to the creation of the organic-mineral layer by the mixing, mound, burial and (or contamination of the different substances on the surface. Therefore, classification of the urban soils by the anthropogenic destruction degree of the soil profile is very important scientific and practical task for the urban ecology to the achievement standards of the ecological safety of the modern city, because the restoring of their protective functions is impossible without knowledge of the morphological structure. Purpose. Classify the anthropogenical soils of city Dnipropetrovsk disturbed by the construction activities by the determining of the morphological characteristics of the soil profile structure with separation of the anthropogenic and technogenic surface formations compared to the zonal soil – ordinery chernozem. Conclusion. Within urboecosystem city Dnipropetrovsk long-term human impact to the zonal soil – chernozem led to its transformation into urbanozem witch
9. Estimation of Corn Yield and Soil Nitrogen via Soil Electrical Conductivity Measurement Treated with Organic, Chemical and Biological Fertilizers
Directory of Open Access Journals (Sweden)
2016-02-01
Full Text Available Introduction Around the world maize is the second crop with the most cultivated areas and amount of production, so as the most important strategic crop, have a special situation in policies, decision making, resources and inputs allocation. On the other side, negative environmental consequences of intensive consumption of agrochemicals resulted to change view concerning food production. One of the most important visions is sustainable production of enough food plus attention to social, economic and environmental aspects. Many researchers stated that the first step to achieve this goal is optimization and improvement of resources use efficiencies. According to little knowledge on relation between soil electrical conductivity and yield of maize, beside the environmental concerns about nitrogen consumption and need to replace chemical nitrogen by ecological inputs, this study designed and aimed to evaluate agroecological characteristics of corn and some soil characteristics as affected by application of organic and biological fertilizers under field conditions. Materials and Methods In order to probing the possibility of grain yield and soil nitrogen estimation via measurement of soil properties, a field experiment was conducted during growing season 2010 at Research Station, Ferdowsi University of Mashhad, Iran. A randomized complete block design (RCBD with three replications was used. Treatments included: 1- manure (30 ton ha-1, 2-vermicompost (10 ton ha-1, 3- nitroxin (containing Azotobacter sp. and Azospirillum sp., inoculation was done according to Kennedy et al., 4- nitrogen as urea (400 kg ha-1 and 5- control (without fertilizer. Studied traits were soil pH, soil EC, soil respiration rate, N content of soil and maize yield. Soil respiration rate was measured using equation 1: CO2= (V0- V× N×22 Equation 1 In which V0 is the volume of consumed acid for control treatment titration, V is of the volume of consumed acid for sample treatment
10. Aerobic and anaerobic nitrogen transformation processes in N2-fixing cyanobacterial aggregates.
Science.gov (United States)
Klawonn, Isabell; Bonaglia, Stefano; Brüchert, Volker; Ploug, Helle
2015-06-01
Colonies of N(2)-fixing cyanobacteria are key players in supplying new nitrogen to the ocean, but the biological fate of this fixed nitrogen remains poorly constrained. Here, we report on aerobic and anaerobic microbial nitrogen transformation processes that co-occur within millimetre-sized cyanobacterial aggregates (Nodularia spumigena) collected in aerated surface waters in the Baltic Sea. Microelectrode profiles showed steep oxygen gradients inside the aggregates and the potential for nitrous oxide production in the aggregates' anoxic centres. (15)N-isotope labelling experiments and nutrient analyses revealed that N(2) fixation, ammonification, nitrification, nitrate reduction to ammonium, denitrification and possibly anaerobic ammonium oxidation (anammox) can co-occur within these consortia. Thus, N. spumigena aggregates are potential sites of nitrogen gain, recycling and loss. Rates of nitrate reduction to ammonium and N(2) were limited by low internal nitrification rates and low concentrations of nitrate in the ambient water. Presumably, patterns of N-transformation processes similar to those observed in this study arise also in other phytoplankton colonies, marine snow and fecal pellets. Anoxic microniches, as a pre-condition for anaerobic nitrogen transformations, may occur within large aggregates (⩾1 mm) even when suspended in fully oxygenated waters, whereas anoxia in small aggregates (1.5 μM), O(2)-depleted water layers, for example, in the chemocline of the Baltic Sea or the oceanic mesopelagic zone, aggregates may promote N-recycling and -loss processes.
11. Soil organic carbon and nitrogen pools drive soil C-CO2 emissions from selected soils in Maritime Antarctica.
Science.gov (United States)
Pires, C V; Schaefer, C E R G; Hashigushi, A K; Thomazini, A; Filho, E I F; Mendonça, E S
2017-10-15
The ongoing trend of increasing air temperatures will potentially affect soil organic matter (SOM) turnover and soil C-CO 2 emissions in terrestrial ecosystems of Maritime Antarctica. The effects of SOM quality on this process remain little explored. We evaluated (i) the quantity and quality of soil organic matter and (ii) the potential of C release through CO 2 emissions in lab conditions in different soil types from Maritime Antarctica. Soil samples (0-10 and 10-20cm) were collected in Keller Peninsula and the vicinity of Arctowski station, to determine the quantity and quality of organic matter and the potential to emit CO 2 under different temperature scenarios (2, 5, 8 and 11°C) in lab. Soil organic matter mineralization is low, especially in soils with low organic C and N contents. Recalcitrant C form is predominant, especially in the passive pool, which is correlated with humic substances. Ornithogenic soils had greater C and N contents (reaching to 43.15gkg -1 and 5.22gkg -1 for total organic carbon and nitrogen, respectively). C and N were more present in the humic acid fraction. Lowest C mineralization was recorded from shallow soils on basaltic/andesites. C mineralization rates at 2°C were significant lower than at higher temperatures. Ornithogenic soils presented the lowest values of C-CO 2 mineralized by g of C. On the other hand, shallow soils on basaltic/andesites were the most sensitive sites to emit C-CO 2 by g of C. With permafrost degradation, soils on basaltic/andesites and sulfates are expected to release more C-CO 2 than ornithogenic soils. With greater clay contents, more protection was afforded to soil organic matter, with lower microbial activity and mineralization. The trend of soil temperature increases will favor C-CO 2 emissions, especially in the reduced pool of C stored and protected on permafrost, or in occasional Histosols. Copyright © 2016 Elsevier B.V. All rights reserved.
12. [Influences of biochar and nitrogen fertilizer on soil nematode assemblage of upland red soil].
Science.gov (United States)
Lu, Yan-yan; Wang, Ming-wei; Chen, Xiao-vun; Liu, Man-qiang; Chen, Xiao-min; Cheng, Yan-hong; Huang, Qian-ru; Hu, Feng
2016-01-01
The use of biochar as soil remediation amendment has received more and more concerns, but little attention has been paid to its effect on soil fauna. Based on the field experiment in an upland red soil, we studied the influences of different application rates of biochar (0, 10, 20, 30, 40 t · hm⁻²) and nitrogen fertilizer (60, 90, 120 kg N · hm⁻²) on soil basic properties and nematode assemblages during drought and wet periods. Our results showed that the biochar amendment significantly affect soil moisture and pH regardless of drought or wet period. With the increasing of biochar application, soil pH significantly increased, while soil moisture increased first and then decreased. Soil microbial properties (microbial biomass C, microbial biomass N, microbial biomass C/N, basal respiration) were also significantly affected by the application of biochar and N fertilizer. Low doses of biochar could stimulate the microbial activity, while high doses depressed microbial activity. For example, averaged across different N application rates, biochar amendment at less than 30 t · hm⁻² could increase microbial activity in the drought and wet periods. Besides, the effects of biochar also depended on wet or drought period. When the biochar application rate higher than 30 t · hm⁻², the microbial biomass C was significantly higher in the drought period than the control, but no differences were observed in the wet period. On the contrary, microbial biomass N showed a reverse pattern. Dissolved organic matter and mineral N were affected by biochar and N fertilizer significantly in the drought period, however, in the wet period they were only affected by N fertilizer rather than biochar. There was significant interaction between biochar and N fertilizer on soil nematode abundance and nematode trophic composition independent of sampling period. Combined high doses of both biochar and N fertilization promoted soil nematode abundance. Moreover, the biochar amendment
13. Effects of floodgates operation on nitrogen transformation in a lake based on structural equation modeling analysis.
Science.gov (United States)
Zhu, Longji; Zhou, Haixuan; Xie, Xinyu; Li, Xueke; Zhang, Duoying; Jia, Liming; Wei, Qingbin; Zhao, Yue; Wei, Zimin; Ma, Yingying
2018-08-01
Floodgates operation is one of the primary means of flood control in lake development. However, knowledge on the linkages between floodgates operation and nitrogen transformation during the flood season is limited. In this study, water samples from six sampling sites along Lake Xingkai watershed were collected before and after floodgates operation. The causal relationships between environmental factors, bacterioplankton community composition and nitrogen fractions were determined during flood season. We found that concentrations of nitrogen fractions decreased significantly when the floodgates were opened, while the concentrations of total nitrogen (TN) and NO 3 - increased when the floodgates had been shut for a period. Further, we proposed a possible mechanism that the influence of floodgates operation on nitrogen transformation was largely mediated through changes in dissolved organic matter, dissolved oxygen and bacterioplankton community composition as revealed by structural equation modeling (SEM). We conclude that floodgates operation has a high risk for future eutrophication of downstream watershed, although it can reduce nitrogen content temporarily. Therefore, the environmental impacts of floodgates operation should be carefully evaluated before the floodwaters were discharged into downstream watershed. Copyright © 2018. Published by Elsevier B.V.
14. Change in gene abundance in the nitrogen biogeochemical cycle with temperature and nitrogen addition in Antarctic soils.
Science.gov (United States)
Jung, Jaejoon; Yeom, Jinki; Kim, Jisun; Han, Jiwon; Lim, Hyoun Soo; Park, Hyun; Hyun, Seunghun; Park, Woojun
2011-12-01
15. Manganese toxicity effects on nodulation and nitrogen fixation of beans (Phaseolus vulgaris L. ), in acid soils
Energy Technology Data Exchange (ETDEWEB)
Doebereiner, J
1966-02-01
Three greenhouse experiments were conducted to study manganese toxicity effects on the nitrogen fixing symbiosis of beans (Phaseolus vulgaris). Addition of 40 ppm of manganese to two acid soils affected nodulation and nitrogen fixation. Dependent on the Rhizobion strain either nodule numbers or efficiency in nitrogen fixation were reduced; the efficiency of one Rhizobium-host combination was more affected than another. Under less severe conditions of manganese toxicity, reduction of nodule numbers or of efficiency in nitrogen fixation could be compensated by an increase of nodule size. In the absence of manganese toxicity nodulation and nitrogen fixation of beans were abundant in a soil with pH 4.4. Naturally occurring manganese toxicity in a gray hydromorphic soil was eliminated by liming. The total nitrogen content of bean plants which were dependent on symbiotic nitrogen fixation decreased linearly with the logarithm of the manganese concentration in the plants. This did not happen when the plants were grown with mineral nitrogen. The role of manganese toxicity in the well known sensitivity to acid soil conditions of certain legumes and the importance of selection of manganese tolerant Rhizobium strains for the inoculation of beans in acid tropical soils, are discussed. 25 references, 1 figure, 6 tables.
16. [Effects of biochar on soil nitrogen cycle and related mechanisms: a review].
Science.gov (United States)
Pan, Yi-Fan; Yang, Min; Dong, Da; Wu, Wei-Xiang
2013-09-01
Biochar has its unique physical and chemical properties, playing a significant role in soil amelioration, nutrient retention, fertility improvement, and carbon storage, and being a hotspot in the research areas of soil ecosystem, biogeochemical cycling, and agricultural carbon sequestration. As a kind of anthropogenic materials, biochar has the potential in controlling soil nitrogen (N) cycle directly or indirectly, and thus, has profound effects on soil ecological functions. This paper reviewed the latest literatures regarding the effects of biochar applications on soil N cycle, with the focuses on the nitrogen species adsorption and the biochemical processes (nitrification, denitrification, and nitrogen fixation) , and analyzed the related action mechanisms of biochar. The future research areas for better understanding the interactions between biochar and soil N cycle were proposed.
17. The effect of elevated cadmium content in soil on the uptake of nitrogen by plants
Energy Technology Data Exchange (ETDEWEB)
Ciecko, Z.; Kalembasa, S.; Wyszkowski, M.; Rolka, E. [University of Warmia & Mazury Olsztyn, Olsztyn (Poland). Dept. of Environmental Chemistry
2004-07-01
The aim of this study was to determine the effect of cadmium (10, 20, 30 and 40 mg Cd/kg of soil) contamination in soil with the application of different substances (compost, brown coal, lime and bentonite) on the intake of nitrogen by some plants. The correlations between the nitrogen content in the plants and the cadmium concentration in the soil, as well as the plant yield and the content of micro- and macroelements in the plants were determined. Plant species and cadmium dose determined the effects of soil contamination with cadmium on the content of nitrogen. Large doses of cadmium caused an increase in nitrogen content in the Avena sativa straw and roots and in the Zea mays roots. Soil contamination with cadmium resulted in a decrease of nitrogen content in the Avena sativa grain, in above-ground parts and roots of the Lupinus luteus, in the above-ground parts of the Zea mays and in the above-ground parts and roots of Phacelia tanacaetifolia. Among the experimental different substances, the application of bentonite had the strongest and a usually negative effect on the nitrogen content in plants. The greatest effect of bentonite was on Avena sativa grain, above-ground parts Zea mays and Lupinus luteus and Phacelia tanacaetifolia. The content of nitrogen in the plants was generally positively correlated with the content of the macroelements and some of the microelements, regardless of the substances added to the soil.
18. Effect of phosphate additive on the nitrogen transformation during pig manure composting.
Science.gov (United States)
Wu, Juan; He, Shengzhou; Liang, Ying; Li, Guoxue; Li, Song; Chen, Shili; Nadeem, Faisal; Hu, Jingwei
2017-07-01
Previous studies revealed that phosphate, as an additive to composting, could significantly reduce NH 3 emission and nitrogen loss through change of pH and nitrogen fixation to form ammonium phosphate. However, few studies have explored the influence of pH change and phosphate additive on NO x - -N, NH 4 + -N, NH 3 , and N 2 O, which are dominate forms of nitrogen in composting. In this study, the equimolar H 3 PO 4 , H 2 SO 4 , and K 2 HPO 4 were added into pig manure composting to evaluate the effect of H + and PO 4 3- on nitrogen transformation. As a result, we reached the conclusion that pH displays significant influence on adsorption from PO 4 3- to NH 4 + . The NH 4 + -N concentration in H 3 PO 4 treatment kept over 3 g kg -1 DM (dry matter) which is obviously higher than that in H 2 SO 4 treatment, and NH 4 + -N concentration in K 2 HPO 4 treatment (pH>8.5) is lower than 0.5 g kg -1 DM because adsorption capacity of PO 4 3- is greatly weakened and NH 4 + -N rapidly transformed to NH 3 -N influenced by high pH value. The N 2 O emission of composting is significantly correlated with incomplete denitrification of NO x - -N, and PO 4 3- addition could raise NO x - -N contents to restrict denitrification and further to promote N 2 O emission. The study reveals the influence mechanism of phosphate additive to nitrogen transformation during composting, presents theoretical basis for additive selection in nitrogen fixation, and lays foundation for study about nitrogen circulation mechanism during composting.
19. Do soil tests help forecast nitrogen response in first-year corn following alfalfa on fine-textured soils?
Science.gov (United States)
Improved methods of predicting grain yield response to fertilizer N for first-year corn (Zea mays L.) following alfalfa (Medicago sativa L.) on fine-textured soils are needed. Data from 21 site-years in the North Central Region were used to (i) determine how Illinois soil nitrogen test (ISNT) and pr...
20. Differences on nitrogen availability in a soil amended with fresh, composted and thermally-dried sewage sludge.
Science.gov (United States)
Tarrasón, D; Ojeda, G; Ortiz, O; Alcañiz, J M
2008-01-01
Anaerobically-digested sludge called fresh sludge (F), composted sludge (C) and thermally-drying sludge (T), all from the same batch, were applied to the surface of a calcareous Udic Calciustept with loamy texture. Dosage equivalent was 10 t ha(-1) of dry matter. The concentration of mineral nitrogen (ammonium and nitrate) in the soil was measured in order to estimate the effects of the post-treatments to which the different kinds of sewage sludge are subjected in relation to the availability of N in the surface layer of the soil. The most significant differences in NH(4)-N and NO(3)-N concentrations due to the transformation of the organic matter were observed during the first three weeks following soil amendment. Thermally-dried and composted sludge initially displayed higher concentrations of ammonium and nitrate in soil. Five months after the amendment, soil applied with fresh sludge showed the highest concentrations of NH(4)-N and NO(3)-N (6.1 and 36.6 mg kg(-1), respectively). It is clear that the processes of composting and thermal-drying influence the bioavailability of nitrogen from the different types of sewage sludge.
1. Nitrogen losses in vineyards under different types of soil groundcover. A field runoff simulator approach in central Spain
NARCIS (Netherlands)
García-Díaz, Andrés; Bienes, Ramón; Sastre, Blanca; Novara, Agata; Gristina, Luciano; Cerda Bolinches, Artemio
2017-01-01
The soils of Mediterranean vineyards are usually managed with continuous tillage, resulting in bare soil, low infiltration and high soil erosion rates. Soil nutrients, such as nitrogen, could be lost dissolved in the runoff, causing a decrease in soil fertility on such degraded soils and producing
2. Influence of carbohydrate addition on nitrogen transformations and greenhouse gas emissions of intensive aquaculture system.
Science.gov (United States)
Hu, Zhen; Lee, Jae Woo; Chandran, Kartik; Kim, Sungpyo; Sharma, Keshab; Khanal, Samir Kumar
2014-02-01
Aquaculture is one of the fastest-growing segments of the food economy in modern times. It is also being considered as an important source of greenhouse gas (GHG) emissions. To date, limited studies have been conducted on GHG emissions from aquaculture system. In this study, daily addition of fish feed and soluble starch at a carbon-to-nitrogen (C/N) ratio of 16:1 (w/w) was used to examine the effects of carbohydrate addition on nitrogen transformations and GHG emissions in a zero-water exchange intensive aquaculture system. The addition of soluble starch stimulated heterotrophic bacterial growth and denitrification, which led to lower total ammonia nitrogen, nitrite and nitrate concentrations in aqueous phase. About 76.2% of the nitrogen output was emitted in the form of gaseous nitrogen (i.e., N2 and N2O) in the treatment tank (i.e., aquaculture tank with soluble starch addition), while gaseous nitrogen accounted for 33.3% of the nitrogen output in the control tank (i.e., aquaculture tank without soluble starch addition). Although soluble starch addition reduced daily N2O emissions by 83.4%, it resulted in an increase of daily carbon dioxide (CO2) emissions by 91.1%. Overall, starch addition did not contribute to controlling the GHG emissions from the aquaculture system. © 2013.
3. Comparisons between three nitrogen fertilizers (nitric, ammoniacal and uric) in an andic soil of the Comoro Islands. Studies in a controlled medium with nitrogen 15
International Nuclear Information System (INIS)
Egoumenides, C.; Pichot, J.; Haribou, A.
1980-01-01
The fixation rate (nitrogen in the plant + nitrogen remaining in the soil) was measured for nitrogen from three different labelled fertilizers: calcium nitrate, ammonium sulfate and urea. This experiment, which was realized in pots with and without cultures led to the following observations: the same fixation rates occur for all fertilizers, which are greater when cultures are employed then when they are not employed (86% ans 72% respectively); the utilization rate of nitrogen fertilizers by plants is significantly higher with the nitric form of fertilizer than with the two other forms (73% and 63% respectively). With cultures, the nitrogen nonutilized by the plant is found in nitrogen organic forms of the soil. On the other hand, in the case of bare soil, the reorganization of nitrogen fertilizers (above all nitric fertilizers) is found to be highly limited, the greatest proportion of the fertilizer's nitrogen remaining in the mineral form [fr
4. Enzymology under global change: organic nitrogen turnover in alpine and sub-Arctic soils
NARCIS (Netherlands)
Weedon, J.T.; Aerts, R.; Kowalchuk, G.A.; van Bodegom, P.M.
2011-01-01
Understanding global change impacts on the globally important carbon storage in alpine, Arctic and sub-Arctic soils requires knowledge of the mechanisms underlying the balance between plant primary productivity and decomposition. Given that nitrogen availability limits both processes, understanding
5. The influence of site factors on nitrogen mineralization in forest soils ...
African Journals Online (AJOL)
The influence of site factors on nitrogen mineralization in forest soils of the ... on N mineralization, as well as the effect of N mineralization on forest productivity. ... of the natural log of mean annual temperature, geological substrate and total N ...
6. Enzymology under global change: organic nitrogen turnover in alpine and sub-Arctic soils.
NARCIS (Netherlands)
Weedon, J.T.; Aerts, R.; Kowalchuk, G.A.; van Bodegom, P.M.
2011-01-01
Understanding global change impacts on the globally important carbon storage in alpine, Arctic and sub-Arctic soils requires knowledge of the mechanisms underlying the balance between plant primary productivity and decomposition. Given that nitrogen availability limits both processes, understanding
7. Effects of biochar addition to soil on nitrogen fluxes in a winter wheat lysimeter experiment
Science.gov (United States)
Hüppi, Roman; Leifeld, Jens; Neftel, Albrecht; Conen, Franz; Six, Johan
2014-05-01
Biochar is a carbon-rich, porous residue from pyrolysis of biomass that potentially increases crop yields by reducing losses of nitrogen from soils and/or enhancing the uptake of applied fertiliser by the crops. Previous research is scarce about biochar's ability to increase wheat yields in temperate soils or how it changes nitrogen dynamics in the field. In a lysimeter system with two different soils (sandy/silt loam) nitrogen fluxes were traced by isotopic 15N enriched fertiliser to identify changes in nitrous oxide emissions, leaching and plant uptake after biochar addition. 20t/ha woodchip-waste biochar (pH=13) was applied to these soils in four lysimeters per soil type; the same number of lysimeters served as a control. The soils were cropped with winter wheat during the season 2012/2013. 170 kg-N/ha ammonium nitrate fertiliser with 10% 15N was applied in 3 events during the growing season and 15N concentrations where measured at different points in time in plant, soil, leachate and emitted nitrous oxide. After one year the lysimeter system showed no difference between biochar and control treatment in grain- and straw yield or nitrogen uptake. However biochar did reduce nitrous oxide emissions in the silt loam and losses of nitrate leaching in sandy loam. This study indicates potential reduction of nitrogen loss from cropland soil by biochar application but could not confirm increased yields in an intensive wheat production system.
8. Nitrification inhibitors mitigated reactive gaseous nitrogen intensity in intensive vegetable soils from China.
Science.gov (United States)
Fan, Changhua; Li, Bo; Xiong, Zhengqin
2018-01-15
Nitrification inhibitors, a promising tool for reducing nitrous oxide (N 2 O) losses and promoting nitrogen use efficiency by slowing nitrification, have gained extensive attention worldwide. However, there have been few attempts to explore the broad responses of multiple reactive gaseous nitrogen emissions of N 2 O, nitric oxide (NO) and ammonia (NH 3 ) and vegetable yield to nitrification inhibitor applications across intensive vegetable soils in China. A greenhouse pot experiment with five consecutive vegetable crops was performed to assess the efficacies of two nitrification inhibitors, namely, nitrapyrin and dicyandiamide on reactive gaseous nitrogen emissions, vegetable yield and reactive gaseous nitrogen intensity in four typical vegetable soils representing the intensive vegetable cropping systems across mainland China: an Acrisol from Hunan Province, an Anthrosol from Shanxi Province, a Cambisol from Shandong Province and a Phaeozem from Heilongjiang Province. The results showed soil type had significant influences on reactive gaseous nitrogen intensity, with reactive gaseous nitrogen emissions and yield mainly driven by soil factors: pH, nitrate, C:N ratio, cation exchange capacity and microbial biomass carbon. The highest reactive gaseous nitrogen emissions and reactive gaseous nitrogen intensity were in Acrisol while the highest vegetable yield occurred in Phaeozem. Nitrification inhibitor applications decreased N 2 O and NO emissions by 1.8-61.0% and 0.8-79.5%, respectively, but promoted NH 3 volatilization by 3.2-44.6% across all soils. Furthermore, significant positive correlations were observed between inhibited N 2 O+NO and stimulated NH 3 emissions with nitrification inhibitor additions across all soils, indicating that reduced nitrification posed the threat of NH 3 losses. Additionally, reactive gaseous nitrogen intensity was significantly reduced in the Anthrosol and Cambisol due to the reduced reactive gaseous nitrogen emissions and increased
9. Impacts of atmospheric nitrogen deposition on vegetation and soils in Joshua Tree National Park
Science.gov (United States)
E.B. Allen; L. Rao; R.J. Steers; A. Bytnerowicz; M.E. Fenn
2009-01-01
The western Mojave Desert is downwind of nitrogen emissions from coastal and inland urban sources, especially automobiles. The objectives of this research were to measure reactive nitrogen (N) in the atmosphere and soils along a N-deposition gradient at Joshua Tree National Park and to examine its effects on invasive and native plant species. Atmospheric nitric acid (...
10. Different types of nitrogen deposition show variable effects on the soil carbon cycle process of temperate forests.
Science.gov (United States)
Du, Yuhan; Guo, Peng; Liu, Jianqiu; Wang, Chunyu; Yang, Ning; Jiao, Zhenxia
2014-10-01
Nitrogen (N) deposition significantly affects the soil carbon (C) cycle process of forests. However, the influence of different types of N on it still remained unclear. In this work, ammonium nitrate was selected as an inorganic N (IN) source, while urea and glycine were chosen as organic N (ON) sources. Different ratios of IN to ON (1 : 4, 2 : 3, 3 : 2, 4 : 1, and 5 : 0) were mixed with equal total amounts and then used to fertilize temperate forest soils for 2 years. Results showed that IN deposition inhibited soil C cycle processes, such as soil respiration, soil organic C decomposition, and enzymatic activities, and induced the accumulation of recalcitrant organic C. By contrast, ON deposition promoted these processes. Addition of ON also resulted in accelerated transformation of recalcitrant compounds into labile compounds and increased CO2 efflux. Meanwhile, greater ON deposition may convert C sequestration in forest soils into C source. These results indicated the importance of the IN to ON ratio in controlling the soil C cycle, which can consequently change the ecological effect of N deposition. © 2014 John Wiley & Sons Ltd.
11. Man-induced transformation of mountain meadow soils of Aragats mountain massif (Armenia)
Science.gov (United States)
Avetisyan, M. H.
2018-01-01
The article considers issues of degradation of mountain meadow soils of the Aragats mountain massif of the Republic of Armenia and provides the averaged research results obtained for 2013 and 2014. The present research was initiated in the frames of long-term complex investigations of agroecosystems of Armenia’s mountain massifs and covered sod soils of high mountain meadow pasturelands and meadow steppe grasslands lying on southern slope of Mt. Aragats. With a purpose of studying the peculiarities of migration and transformation of flows of major nutrients namely carbon, nitrogen, phosphorus in study mountain meadow and meadow steppe belts of the Aragats massif we investigated water migration of chemical elements and regularities of their leaching depending on different belts. Field measurement data have indicated that organic carbon and humus in a heavily grazed plot are almost twice as low as on a control site. Lysimetric data analysis has demonstrated that heavy grazing and illegal deforestation have brought to an increase in intrasoil water acidity. The results generated from this research support a conclusion that a man’s intervention has brought to disturbance of structure and nutrient and water regimes of soils and loss of significant amounts of soil nutrients throughout the studied region.
12. The regulatory role of endogenous iron on greenhouse gas emissions under intensive nitrogen fertilization in subtropical soils of China.
Science.gov (United States)
Han, Jiangpei; Shi, Liangsheng; Wang, Yakun; Chen, Zhuowei; Wu, Laosheng
2018-05-01
Anaerobic batch experiments were conducted to study the regulatory role of endogenous iron in greenhouse gas emissions under intensive nitrogen fertilization in subtropical soils of China. Fe 2+ , Fe 3+ , and NO 3 - -N dynamics and N 2 O, CH 4 , and CO 2 emissions, as well as the relationships between N fertilizer, endogenous iron, and greenhouse gas emissions were investigated. The emissions of N 2 O increased to different extents from all the test soils by N1 (260 mg N kg -1 ) application compared with N0. After 24 days of anaerobic incubation, the cumulative emissions of N 2 O from red soils in De'an (DR) were significantly higher than that from paddy soils in De'an (DP) and Qujialing (QP) under N1. However, N application enhanced CH 4 and CO 2 emissions from the red soils slightly but inhibited the emissions from paddy soils. The maximal CH 4 and CO 2 emission fluxes occurred in DP soil without N input. Pearson's correlation analysis showed that there were significant correlations (P greenhouse gas emissions mainly through the involvement in denitrification. The proportion of the electrons donated by Fe 2+ used for N 2 O production in denitrification in DP soil was approximately 37.53%. Moreover, positive correlations between Fe 2+ and CH 4 , CO 2 were found in both DR and QP soils, suggesting that endogenous iron might regulate the anaerobic decomposition of organic carbon to CH 4 and CO 2 in the two soils. Soil pH was also an important factor controlling greenhouse gas emissions by affecting endogenous iron availability and C and N transformation processes.
13. Study on the reduction and hysteresis effect of soil nitrogen pollution by Alfalfa in channel buffer bank
Science.gov (United States)
Chi, Yixia; Xue, Lianqing; Zhang, Zhanyu; Li, Dongying
2018-01-01
Based on the simulation experiments of solute transport in channel buffer bank and pot experiments, this study analyzed the transport of nitrogen pollution from farmland drains along the South-North Water Transfer east route project; and compared the nitrogen transport rule and purification effect of alfalfa in channel buffer bank soil under situations of bare land and alfalfa mulching. The results showed that: (1) soil nitrogen content decreased gradually with the width increase of channel buffer bank by the soil adsorption and decomposition; (2) the migration rates of nitrogen were 0.06 g·kg-1 by the alfalfa mulching; (3) the removed rates of nitrogen from the soil were 0.088 g·kg-1 by cutting alfalfa; (4) the residual nitrogen of soil with alfalfa was 10% of the bare land. Alfalfa in channel buffer bank had obvious reduction and hysteresis effect to soil nitrogen pollution.
14. Microbial nitrogen transformation potential in surface run-off leachate from a tropical landfill
International Nuclear Information System (INIS)
Mangimbulude, Jubhar C.; Straalen, Nico M. van; Röling, Wilfred F.M.
2012-01-01
Highlights: ► Microbial nitrogen transformations can alleviate toxic ammonium discharge. ► Aerobic ammonium oxidation was rate-limiting in Indonesian landfill leachate. ►Organic nitrogen ammonification was most dominant. ► Anaerobic nitrate reduction and ammonium oxidation potential were also high. ► A two-stage aerobic-anaerobic nitrogen removal system needs to be implemented. - Abstract: Ammonium is one of the major toxic compounds and a critical long-term pollutant in landfill leachate. Leachate from the Jatibarang landfill in Semarang, Indonesia, contains ammonium in concentrations ranging from 376 to 929 mg N L −1 . The objective of this study was to determine seasonal variation in the potential for organic nitrogen ammonification, aerobic nitrification, anaerobic nitrate reduction and anaerobic ammonium oxidation (anammox) at this landfilling site. Seasonal samples from leachate collection treatment ponds were used as an inoculum to feed synthetic media to determine potential rates of nitrogen transformations. Aerobic ammonium oxidation potential ( −1 h −1 ) was more than a hundred times lower than the anaerobic nitrogen transformation processes and organic nitrogen ammonification, which were of the same order of magnitude. Anaerobic nitrate oxidation did not proceed beyond nitrite; isolates grown with nitrate as electron acceptor did not degrade nitrite further. Effects of season were only observed for aerobic nitrification and anammox, and were relatively minor: rates were up to three times higher in the dry season. To completely remove the excess ammonium from the leachate, we propose a two-stage treatment system to be implemented. Aeration in the first leachate pond would strongly contribute to aerobic ammonium oxidation to nitrate by providing the currently missing oxygen in the anaerobic leachate and allowing for the growth of ammonium oxidisers. In the second pond the remaining ammonium and produced nitrate can be converted by a
15. Carbon and nitrogen mineralization in vineyard acid soils amended with a bentonitic winery waste
Science.gov (United States)
Fernández-Calviño, David; Rodríguez-Salgado, Isabel; Pérez-Rodríguez, Paula; Díaz-Raviña, Montserrat; Nóvoa-Muñoz, Juan Carlos; Arias-Estévez, Manuel
2015-04-01
Carbon mineralization and nitrogen ammonification processes were determined in different vineyard soils. The measurements were performed in samples non-amended and amended with different bentonitic winery waste concentrations. Carbon mineralization was measured as CO2 released by the soil under laboratory conditions, whereas NH4+ was determined after its extraction with KCl 2M. The time evolution of both, carbon mineralization and nitrogen ammonification, was followed during 42 days. The released CO2 was low in the analyzed vineyard soils, and hence the metabolic activity in these soils was low. The addition of the bentonitic winery waste to the studied soils increased highly the carbon mineralization (2-5 fold), showing that the organic matter added together the bentonitic waste to the soil have low stability. In both cases, amended and non-amended samples, the maximum carbon mineralization was measured during the first days (2-4 days), decreasing as the incubation time increased. The NH4+ results showed an important effect of bentonitic winery waste on the ammonification behavior in the studied soils. In the non-amended samples the ammonification was no detected in none of the soils, whereas in the amended soils important NH4+ concentrations were detected. In these cases, the ammonification was fast, reaching the maximum values of NH4 between 7 and 14 days after the bentonitic waste additions. Also, the percentages of ammonification respect to the total nitrogen in the soil were high, showing that the nitrogen provided by the bentonitic waste to the soil is non-stable. The fast carbon mineralization found in the soils amended with bentonitic winery wastes shows low possibilities of the use of this waste for the increasing the organic carbon pools in the soil.On the other hand, the use of this waste as N-fertilizer can be possible. However, due its fast ammonification, the waste should be added to the soils during active plant growth periods.
16. Improvement of the soil nitrogen content and maize growth by earthworms and arbuscular mycorrhizal fungi in soils polluted by oxytetracycline.
Science.gov (United States)
Cao, Jia; Wang, Chong; Ji, Dingge
2016-11-15
Interactions between earthworms (Eisenia fetida) and arbuscular mycorrhizal fungi (Rhizophagus intraradices, AM fungi) have been suggested to improve the maize nitrogen (N) content and biomass and were studied in soils polluted by oxytetracycline (OTC). Maize was planted and amended with AMF and/or earthworms (E) in the soil with low (1mgkg(-1) soil DM) or high (100mgkg(-1) soil DM) amounts of OTC pollution in comparison to soil without OTC. The root colonization, shoot and root biomass, shoot and root N contents, soil nitrogen forms, ammonia-oxidizing bacteria (AOB) and archaea (AOA) were measured at harvest. The results indicated that OTC decreased maize shoot and root biomass (psoil urease activity and AOB and AOA abundance, which resulted in a lower N availability for maize roots and shoots. There was a significant interaction between earthworms and AM fungi on the urease activity in soil polluted by OTC (ppolluted soil by increasing the urease activity and relieving the stress from OTC on the soil N cycle. AM fungi and earthworms interactively increased maize shoot and root biomass (ppolluted soils through their regulation of the urease activity and the abundance of ammonia oxidizers, resulting in different soil NH4(+)-N and NO3(-)-N contents, which may contribute to the N content of maize shoots and roots. Earthworms and AM fungi could be used as an efficient method to relieve the OTC stress in agro-ecosystems. Copyright © 2016 Elsevier B.V. All rights reserved.
17. Organic nitrogen storage in mineral soil: Implications for policy and management
Energy Technology Data Exchange (ETDEWEB)
Bingham, Andrew H., E-mail: [email protected] [Air Resources Division, National Park Service, P.O. Box 25287, Denver, CO 80225 (United States); Cotrufo, M. Francesca [Department of Soil and Crop Sciences and Natural Resources Ecology Laboratory, Colorado State University, 200 West Lake Street, Fort Collins, CO 80523 (United States)
2016-05-01
Nitrogen is one of the most important ecosystem nutrients and often its availability limits net primary production as well as stabilization of soil organic matter. The long-term storage of nitrogen-containing organic matter in soils was classically attributed to chemical complexity of plant and microbial residues that retarded microbial degradation. Recent advances have revised this framework, with the understanding that persistent soil organic matter consists largely of chemically labile, microbially processed organic compounds. Chemical bonding to minerals and physical protection in aggregates are more important to long-term (i.e., centuries to millennia) preservation of these organic compounds that contain the bulk of soil nitrogen rather than molecular complexity, with the exception of nitrogen in pyrogenic organic matter. This review examines for the first time the factors and mechanisms at each stage of movement into long-term storage that influence the sequestration of organic nitrogen in the mineral soil of natural temperate ecosystems. Because the factors which govern persistence are different under this newly accepted paradigm we examine the policy and management implications that are altered, such as critical load considerations, nitrogen saturation and mitigation consequences. Finally, it emphasizes how essential it is for this important but underappreciated pool to be better quantified and incorporated into policy and management decisions, especially given the lack of evidence for many soils having a finite capacity to sequester nitrogen. - Highlights: • We review the current framework for long-term nitrogen stabilization in soils. • We highlight the most important factors according to this framework. • We discuss how these factors may influence management and policy decisions.
18. The use of N15 for studying the mechanism of transformation in the soil and plant
International Nuclear Information System (INIS)
Alchater, M.S.
1995-01-01
This research pertains to the study of the mechanism of transformation of added N 15 in the soil and plant in an attempt to determine the competition between microbial biomass and the plant for the use of N fertilizer in the form of (N 15 H 4)2 So 4. Additional amounts of barley straw were added as a source of energy. The study led to determining the real utilization coefficient of the canopy and the root system which amounted to 79% of N 15 added alone. Whereas it amounted to the treatments in which barley straw was added to N 15. Furthermore, there was a decrease in the amount of organic N 15 in the form of Gamma-amine as compared with other forms of organic N which also decreased to lesser degree. The results also indicated that the important N in the immobilization of nitrogen, as observed in previous field trials. Nitrogen balance and the contribution of soil N to plant nutrition were also calculated. 2 figs., 5 tabs
19. The effects of warming and nitrogen addition on soil nitrogen cycling in a temperate grassland, northeastern China.
Directory of Open Access Journals (Sweden)
Lin-Na Ma
Full Text Available Both climate warming and atmospheric nitrogen (N deposition are predicted to affect soil N cycling in terrestrial biomes over the next century. However, the interactive effects of warming and N deposition on soil N mineralization in temperate grasslands are poorly understood.A field manipulation experiment was conducted to examine the effects of warming and N addition on soil N cycling in a temperate grassland of northeastern China from 2007 to 2009. Soil samples were incubated at a constant temperature and moisture, from samples collected in the field. The results showed that both warming and N addition significantly stimulated soil net N mineralization rate and net nitrification rate. Combined warming and N addition caused an interactive effect on N mineralization, which could be explained by the relative shift of soil microbial community structure because of fungal biomass increase and strong plant uptake of added N due to warming. Irrespective of strong intra- and inter-annual variations in soil N mineralization, the responses of N mineralization to warming and N addition did not change during the three growing seasons, suggesting independence of warming and N responses of N mineralization from precipitation variations in the temperate grassland.Interactions between climate warming and N deposition on soil N cycling were significant. These findings will improve our understanding on the response of soil N cycling to the simultaneous climate change drivers in temperate grassland ecosystem.
20. The soil acidity as restrictive factor of the use of nitrogen fertilizer by spring barley
International Nuclear Information System (INIS)
Hejnak, V.; Lippold, H.
1999-01-01
In two - year micro - plot trials was studied the effect of soil pH value (pH > 6,5 and pH 15 N in first year and no enriched in second year, rates of 0, 85, 170 and 255 mg N per pot, i.e. 0, 30, 60 and 90 kg N.ha -1 ) on the spring barley productivity and on the use of nitrogen fertilizer by plants in the application year of 15 N and in the following year. The productivity of spring barley is significantly higher in neutral soil than in acid soil. The gradated rates of nitrogen fertilization increased this difference. The total nitrogen uptake by plants was higher in neutral soil. The share of the nitrogen from 'the old soil's supply' in the total uptake by the harvest ranges from 95 to 82 % and is practically identical in studied soils. 'Priming effect' was higher in soil with better fertility (153 - 186 mg N per pot) than in acid soil (to 49 mg N per pot only). The gradated rates of ammonium sulphate increased the uptake nitrogen from fertilizer by harvest of spring barley in the application year of 15 N from 39 mg N to 107 mg N per pot in neutral soil and from 26 mg N to 83 mg N per pot in acid soil and in the following year from 3,05 mg N to 8,15 mg N per pot in neutral soil and from 1,76 mg N to 3,37 mg N per pot in acid soil. The total balance of fertilizer nitrogen ( 15 N) in soil - crop system in two years from application showed that in neutral soil 46 % used by spring barley (42 % in the application year and 4 % in the following year), 16 % rested in soil and loss was 38 % and in acid soil 35 % used by harvest (33 % in first year and 2 % second year), 12 % rested in soil and loss was 53 %. Refs. 5 (author)
1. Soil carbon mineralization following biochar addition associated with external nitrogen
Directory of Open Access Journals (Sweden)
Rudong Zhao
2015-12-01
Full Text Available Biochar has been attracting increasing attention for its potentials of C sequestration and soil amendment. This study aimed to understand the effects of combining biochar with additional external N on soil C mineralization. A typical red soil (Plinthudults was treated with two biochars made from two types of plantation-tree trunks (soil-biochar treatments, and was also treated with external N (soil-biochar-N treatments. All treatments were incubated for 42 d. The CO2-C released from the treatments was detected periodically. After the incubation, soil properties such as pH, microbial biomass C (MBC, and microbial biomass N (MBN were measured. The addition of biochar with external N increased the soil pH (4.31-4.33 compared to the soil treated with external N only (4.21. This was not observed in the comparison of soil-biochar treatments (4.75-4.80 to soil only (4.74. Biochar additions (whether or not they were associated with external N increased soil MBC and MBN, but decreased CO2-C value per unit total C (added biochar C + soil C according to the model fitting. The total CO2-C released in soil-biochar treatments were enhanced compared to soil only (i.e., 3.15 vs. 2.57 mg and 3.23 vs. 2.45 mg, which was attributed to the labile C fractions in the biochars and through soil microorganism enhancement. However, there were few changes in soil C mineralization in soil-biochar-N treatments. Additionally, the potentially available C per unit total C in soil-biochar-N treatments was lower than that observed in the soil-biochar treatments. Therefore, we believe in the short term, that C mineralization in the soil can be enhanced by biochar addition, but not by adding external N concomitantly.
2. Investigation of transformation of radionuclides in soils oil polluted
International Nuclear Information System (INIS)
Humbatov, F.Y.; Ahmedov, M.M.; Ibadov, N.A.; Balayev, V.S.
2004-01-01
3. Nitrogen deposition may enhance soil carbon storage via change of soil respiration dynamic during a spring freeze-thaw cycle period.
Science.gov (United States)
Yan, Guoyong; Xing, Yajuan; Xu, Lijian; Wang, Jianyu; Meng, Wei; Wang, Qinggui; Yu, Jinghua; Zhang, Zhi; Wang, Zhidong; Jiang, Siling; Liu, Boqi; Han, Shijie
2016-06-30
As crucial terrestrial ecosystems, temperate forests play an important role in global soil carbon dioxide flux, and this process can be sensitive to atmospheric nitrogen deposition. It is often reported that the nitrogen addition induces a change in soil carbon dioxide emission in growing season. However, the important effects of interactions between nitrogen deposition and the freeze-thaw-cycle have never been investigated. Here we show nitrogen deposition delays spikes of soil respiration and weaken soil respiration. We found the nitrogen addition, time and nitrogen addition×time exerted the negative impact on the soil respiration of spring freeze-thaw periods due to delay of spikes and inhibition of soil respiration (p nitrogen), 39% (medium-nitrogen) and 36% (high-nitrogen) compared with the control. And the decrease values of soil respiration under medium- and high-nitrogen treatments during spring freeze-thaw-cycle period in temperate forest would be approximately equivalent to 1% of global annual C emissions. Therefore, we show interactions between nitrogen deposition and freeze-thaw-cycle in temperate forest ecosystems are important to predict global carbon emissions and sequestrations. We anticipate our finding to be a starting point for more sophisticated prediction of soil respirations in temperate forests ecosystems.
4. Dissolved organic carbon and nitrogen release from boreal Holocene permafrost and seasonally frozen soils of Alaska
Science.gov (United States)
Wickland, Kimberly P.; Waldrop, Mark P.; Aiken, George R.; Koch, Joshua C.; Torre Jorgenson, M.; Striegl, Robert G.
2018-06-01
Permafrost (perennially frozen) soils store vast amounts of organic carbon (C) and nitrogen (N) that are vulnerable to mobilization as dissolved organic carbon (DOC) and dissolved organic and inorganic nitrogen (DON, DIN) upon thaw. Such releases will affect the biogeochemistry of permafrost regions, yet little is known about the chemical composition and source variability of active-layer (seasonally frozen) and permafrost soil DOC, DON and DIN. We quantified DOC, total dissolved N (TDN), DON, and DIN leachate yields from deep active-layer and near-surface boreal Holocene permafrost soils in interior Alaska varying in soil C and N content and radiocarbon age to determine potential release upon thaw. Soil cores were collected at three sites distributed across the Alaska boreal region in late winter, cut in 15 cm thick sections, and deep active-layer and shallow permafrost sections were thawed and leached. Leachates were analyzed for DOC, TDN, nitrate (NO3 ‑), and ammonium (NH4 +) concentrations, dissolved organic matter optical properties, and DOC biodegradability. Soils were analyzed for C, N, and radiocarbon (14C) content. Soil DOC, TDN, DON, and DIN yields increased linearly with soil C and N content, and decreased with increasing radiocarbon age. These relationships were significantly different for active-layer and permafrost soils such that for a given soil C or N content, or radiocarbon age, permafrost soils released more DOC and TDN (mostly as DON) per gram soil than active-layer soils. Permafrost soil DOC biodegradability was significantly correlated with soil Δ14C and DOM optical properties. Our results demonstrate that near-surface Holocene permafrost soils preserve greater relative potential DOC and TDN yields than overlying seasonally frozen soils that are exposed to annual leaching and decomposition. While many factors control the fate of DOC and TDN, the greater relative yields from newly thawed Holocene permafrost soils will have the largest
5. Effect of soil-moisture stress on nitrogen uptake and fixation by plants
International Nuclear Information System (INIS)
Mitrosuhardjo, M.M.
1983-01-01
The effect of four levels of soil moisture, namely 25, 30, 35, and 40% (g/g) on nitrogen uptake and fixation by plants was studied in a greenhouse experiment. Soybean and wheat were used in this experiment. Both crops were grown in pots containing 7 kg loamy alluvial soil. Rhizobium japonicum was used as an inoculant for soybean, one week after planting. Nitrogen-15 labelled urea with 10% atom excess was applied to each pot with a dose rate of 70 mg N/pot (20 kg N/ha) two weeks after planting. Soil moisture was regularly controlled with porous-cup mercury tensiometers, and the amount of water consumed by plants was always recorded. Water was applied to each pot with a distribution pipe which was laid down in the centre of the soil depth, horizontally in a circular form, and was connected with a smaller pipe to the soil surface. The result obtained showed that the amount of water consumed by plants grown in a higher level of soil moisture was increased until soil aeration problems arose. A different amount of water consumption between soybean and wheat was observed at least until a certain period of growing time. Fertilizer nitrogen taken up by both crops varied with the different levels of soil moisture. Generally, greater fertilizer nitrogen was taken up by both crops grown in a higher level of soil moisture. The symbiotic fixation of nitrogen was reasonable, although no clarification has been found about the role of the four levels of soil-moisture treatment on it. A similar effect of soil-moisture stress on nodule dry matter and acetylene reduction was found. (author)
6. Response of Soil Bulk Density and Mineral Nitrogen to Harvesting and Cultural Treatments
Science.gov (United States)
Minyi Zhou; Mason C. Carter; Thomas J. Dean
1998-01-01
The interactive effects of harvest intensity, site preparation, and fertilization on soil compaction and nitrogen mineralization were examined in a loblolly pine (Pinus taeda L.) stand growing on a sandy, well-drained soil in eastern Texas. The experimental design was 2 by 2 by 2 factorial, consisting of two harvesting treatments (mechanical whole-...
7. Prescribed fire, soil inorganic nitrogen dynamics, and plant responses in a semiarid grassland
Science.gov (United States)
David J. Augustine; Paul Brewer; Dana M. Blumenthal; Justin D. Derner; Joseph C. von Fischer
2014-01-01
In arid and semiarid ecosystems, fire can potentially affect ecosystem dynamics through changes in soil moisture, temperature, and nitrogen cycling, as well as through direct effects on plant meristem mortality. We examined effects of annual and triennial prescribed fires conducted in early spring on soil moisture, temperature, and N, plant growth, and plant N content...
8. Relationships between soil-based management zones and canopy sensing for corn nitrogen management
Science.gov (United States)
Integrating soil-based management zones (MZ) with crop-based active canopy sensors to direct spatially variable nitrogen (N) applications has been proposed for improving N fertilizer management of corn (Zea mays L.). Analyses are needed to evaluate relationships between canopy sensing and soil-based...
9. Will nitrogen deposition mitigate warming-increased soil respiration in a young subtropical plantation?
Science.gov (United States)
Xiaofei Liu; Zhijie Yang; Chengfang Lin; Christian P. Giardina; Decheng Xiong; Weisheng Lin; Shidong Chen; Chao Xu; Guangshui Chen; Jinsheng Xie; Yiqing Li; Yusheng Yang
2017-01-01
Global change such as climate warming and nitrogen (N) deposition is likely to alter terrestrial carbon (C) cycling, including soil respiration (Rs), the largest CO2 source from soils to the atmosphere. To examine the effects of warming, N addition and their interactions on Rs, we...
10. Sustained effects of atmospheric [CO2] and nitrogen availability on forest soil CO2 efflux
Science.gov (United States)
A. Christopher Oishi; Sari Palmroth; Kurt H. Johnsen; Heather R. McCarthy; Ram. Oren
2014-01-01
Soil CO2 efflux (Fsoil) is the largest source of carbon from forests and reflects primary productivity as well as how carbon is allocated within forest ecosystems. Through early stages of stand development, both elevated [CO2] and availability of soil nitrogen (N; sum of mineralization, deposition, and fixation) have been shown to increase gross primary productivity,...
11. Spring nitrogen fertilization of ryegrass-bermudagrass for phytoremediation of phosphorus-enriched soils
Science.gov (United States)
Nitrogen fertilization of forage grasses is critical for optimizing biomass and utilization of manure soil nutrients. Field studies were conducted in 2007-09 to determine the effects of spring N fertilization on amelioration of high soil P when cool-season, annual ryegrass (Lolium multiflorum L.) is...
12. Search for correlatable, isotopically light carbon and nitrogen components in Lunar soils and breccias
International Nuclear Information System (INIS)
Norris, S.J.; Swart, P.K.; Wright, I.P.; Grady, M.M.; Pillinger, C.T.
1983-01-01
Using stepped heating extraction techniques, determinations of carbon and nitrogen content and delta 13 C and delta 15 N values have been obtained for selected lunar soils and breccias. Only nitrogen data have been gathered for representative splits separated by size, density and magnetic properties from 12023. A plot of the total delta 13 C (after terrestrial contamination is removed) versus delta 15 N values for the bulk samples reveals little evidence for a correlation between isotopically light carbon and isotopically light nitrogen of putative ancient solar wind origin. Soil 12023 is used to examine the current interpretation for the stepped release profile of nitrogen from bulk lunar samples. Mature agglutinates, postulated by previous workers to be the host of the light nitrogen, are shown to have a very constant delta 15 N value which is heavy rather than light. The actual host of the light nitrogen in 12023 has not been identified. The lowest values encountered during the study were found associated with the finest soil, but none of these was as low as for some temperature steps of the bulk soil. Interpretations regarding the origin of light nitrogen, if it is not present in agglutinates, await the results of more definitive efforts to identify the host phase
13. Fate of nitrogen (15N) from velvet bean in the soil-plant system
International Nuclear Information System (INIS)
Scivittaro, Walkyria Bueno; Muraoka, Takashi; Boaretto, Antonio Enedi; Trivelin, Paulo Cesar Ocheuze
2004-01-01
Because of their potential for N 2 biological fixation, legumes are an alternative source of nitrogen to crops, and can even replace or supplement mineral fertilization. A greenhouse experiment was carried out to evaluate temporal patterns of velvet bean (Mucuna aterrima) green manure release of nitrogen to rice plants, and to study the fate of nitrogen from velvet bean in rice cultivation. The isotopic dilution methodology was used. Treatments consisted of a control and 10 incubation periods of soil fertilized with 15 N-labeled velvet bean (0, 20, 40, 60, 90, 120, 150, 180, 210, and 240 days). The plant material was previously chopped, sifted (10 mm mesh sieve) and oven-dried (65 deg C). Incubation of the plant material (2.2 g kg -1 soil) was initiated by the longest period, in order to synchronize the planting of the test crop, rice (Oryza sativa), at time zero for all treatments. Green manure incorporation promoted increases in rice dry matter yield and nitrogen uptake. These variables showed maximum values at incubation periods of 38 and 169 days, respectively. Green manure nitrogen utilization by rice plants was highest at an incubation period corresponding to 151 days. More than 60% of the green manure nitrogen remained in the soil after rice cultivation. The highest green manure nitrogen recovery from the soil-plant system occurred at an incubation period equivalent to 77 days. (author)
14. Stimulation of nitrogen fixation in soddy-podzolic soils with fungi
Science.gov (United States)
Kurakov, A. V.; Prokhorov, I. S.; Kostina, N. V.; Makhova, E. G.; Sadykova, V. S.
2006-09-01
Stimulation of nitrogen fixation in soddy-podzolic soils is related to the hydrolytic activity of fungi decomposing plant polymers. It was found that the rate of nitrogen fixation upon the simultaneous inoculation of the strains of nitrogen-fixing bacteria Bacillus cereus var. mycoides and the cellulolytic fungus Trichoderma asperellum into a sterile soil enriched with cellulose or Jerusalem artichoke residues is two to four times higher than upon the inoculation of the strains of Bacillus cereus var. mycoides L1 only. The increase in the nitrogen fixation depended on the resistance of the substrates added into the soil to fungal hydrolysis. The biomass of the fungi decomposing plant polymers increased by two-four times. The nitrogen-fixing activity of the soil decreased when the growth of the fungi was inhibited with cycloheximide, which attested to a close correlation between the intensity of the nitrogen fixation and the decomposition of the plant polymers by fungi. The introduction of an antifungal antibiotic, together with starch or with plant residues, significantly (by 60-90%) decreased the rate of nitrogen fixation in the soll.
15. NitroScape: A model to integrate nitrogen transfers and transformations in rural landscapes
Energy Technology Data Exchange (ETDEWEB)
Duretz, S. [INRA-AgroParisTech, UMR 1091 Environnement et Grandes Cultures (EGC), 78850 Thiverval-Grignon (France); Drouet, J.L., E-mail: [email protected] [INRA-AgroParisTech, UMR 1091 Environnement et Grandes Cultures (EGC), 78850 Thiverval-Grignon (France); Durand, P. [INRA-AgroCampus, UMR 1069 Sol Agro et hydrosysteme Spatialisation (SAS), 35042 Rennes cedex (France); Hutchings, N.J. [Department of Agroecology, Faculty of Agricultural Sciences, University of Aarhus (AU), Blichers Alle, 8830 Tjele (Denmark); Theobald, M.R. [Department of Chemistry and Agricultural Analysis, Technical University of Madrid (UPM), 28040 Madrid (Spain); Centre for Ecology and Hydrology (CEH), Bush Estate, Penicuik, Midlothian EH26 0QB (United Kingdom); Salmon-Monviola, J. [INRA-AgroCampus, UMR 1069 Sol Agro et hydrosysteme Spatialisation (SAS), 35042 Rennes cedex (France); Dragosits, U. [Centre for Ecology and Hydrology (CEH), Bush Estate, Penicuik, Midlothian EH26 0QB (United Kingdom); Maury, O. [INRA-AgroParisTech, UMR 1091 Environnement et Grandes Cultures (EGC), 78850 Thiverval-Grignon (France); Sutton, M.A. [Centre for Ecology and Hydrology (CEH), Bush Estate, Penicuik, Midlothian EH26 0QB (United Kingdom); Cellier, P. [INRA-AgroParisTech, UMR 1091 Environnement et Grandes Cultures (EGC), 78850 Thiverval-Grignon (France)
2011-11-15
Modelling nitrogen transfer and transformation at the landscape scale is relevant to estimate the mobility of the reactive forms of nitrogen (N{sub r}) and the associated threats to the environment. Here we describe the development of a spatially and temporally explicit model to integrate N{sub r} transfer and transformation at the landscape scale. The model couples four existing models, to simulate atmospheric, farm, agro-ecosystem and hydrological N{sub r} fluxes and transformations within a landscape. Simulations were carried out on a theoretical landscape consisting of pig-crop farms interspersed with unmanaged ecosystems. Simulation results illustrated the effect of spatial interactions between landscape elements on N{sub r} fluxes and losses to the environment. More than 10% of the total N{sub 2}O emissions were due to indirect emissions. The nitrogen budgets and transformations of the unmanaged ecosystems varied considerably, depending on their location within the landscape. The model represents a new tool for assessing the effect of changes in landscape structure on N{sub r} fluxes. - Highlights: > The landscape scale is relevant to study how spatial interactions affect N{sub r} fate. > The NitroScape model integrates N{sub r} transfer and transformation at landscape scale. > NitroScape couples existing atmospheric, farm, agro-ecosystem and hydrological models. > Data exchanges within NitroScape are dynamic and spatially distributed. > More than 10% of the simulated N{sub 2}O emissions are due to indirect emissions. - A model integrating terrestrial, hydrological and atmospheric processes of N{sub r} transfer and transformation at the landscape scale has been developed to simulate the effect of spatial interactions between landscape elements on N{sub r} fate.
16. NitroScape: A model to integrate nitrogen transfers and transformations in rural landscapes
International Nuclear Information System (INIS)
Duretz, S.; Drouet, J.L.; Durand, P.; Hutchings, N.J.; Theobald, M.R.; Salmon-Monviola, J.; Dragosits, U.; Maury, O.; Sutton, M.A.; Cellier, P.
2011-01-01
Modelling nitrogen transfer and transformation at the landscape scale is relevant to estimate the mobility of the reactive forms of nitrogen (N r ) and the associated threats to the environment. Here we describe the development of a spatially and temporally explicit model to integrate N r transfer and transformation at the landscape scale. The model couples four existing models, to simulate atmospheric, farm, agro-ecosystem and hydrological N r fluxes and transformations within a landscape. Simulations were carried out on a theoretical landscape consisting of pig-crop farms interspersed with unmanaged ecosystems. Simulation results illustrated the effect of spatial interactions between landscape elements on N r fluxes and losses to the environment. More than 10% of the total N 2 O emissions were due to indirect emissions. The nitrogen budgets and transformations of the unmanaged ecosystems varied considerably, depending on their location within the landscape. The model represents a new tool for assessing the effect of changes in landscape structure on N r fluxes. - Highlights: → The landscape scale is relevant to study how spatial interactions affect N r fate. → The NitroScape model integrates N r transfer and transformation at landscape scale. → NitroScape couples existing atmospheric, farm, agro-ecosystem and hydrological models. → Data exchanges within NitroScape are dynamic and spatially distributed. → More than 10% of the simulated N 2 O emissions are due to indirect emissions. - A model integrating terrestrial, hydrological and atmospheric processes of N r transfer and transformation at the landscape scale has been developed to simulate the effect of spatial interactions between landscape elements on N r fate.
17. The Role of Biological Soil Crusts in Nitrogen Cycling and Soil Deflation in West Greenland
Science.gov (United States)
Heindel, R. C.; Governali, F. C.; Spickard, A. M.; Virginia, R. A.
2017-12-01
Although shrub expansion has been observed across the Arctic in moist tundra habitat, shrubs may be prevented from expanding in arid Arctic regions due to low soil moisture or soil erosion. This may be the case in Kangerlussuaq, West Greenland, where katabatic winds off the Greenland Ice Sheet have eroded distinct patches of mixed shrub tundra, resulting in nearly barren low productivity areas dominated by biological soil crusts (biocrusts) and graminoids. The future trajectory of these bare patches - persisting in a low biomass state or returning to a shrub-dominated state - depends on the role of the biocrust as either a long-term landscape cover limiting revegetation or as a successional facilitator. Prior to this study, little was known about the physical and ecological development of West Greenland biocrusts and how they may influence future vegetation dynamics. We found that biocrusts took 230 ± 48 years to fully develop, and that later stages of biocrust development were related to increased thickness and penetration resistance and decreased soil moisture, factors limiting shrub seedling establishment. The nitrogen (N) fixing lichen Stereocaulon sp. was found throughout the study region at all stages of biocrust development. Natural 15N abundance suggests that Stereocaulon sp. obtains about half of its N from biological fixation, and that some biologically-fixed N is incorporated into the underlying soils over time. Although soil N and C concentrations increased slightly with biocrust development, their levels under the most developed biocrusts remained low compared to the surrounding shrub and graminoid tundra. Our results suggest that deflation patches, triggered by long-term variations in climate, may remain in a low-productivity ecosystem state for hundreds to thousands of years, if precipitation and temperature regimes do not dramatically alter the vegetation potential of the region. However, if future climate change in the Arctic favors greater
18. Effect of long-term changes in soil chemistry induced by road salt applications on N-transformations in roadside soils
International Nuclear Information System (INIS)
Green, Sophie M.; Machin, Robert; Cresser, Malcolm S.
2008-01-01
Of several impacts of road salting on roadside soils, the potential disruption of the nitrogen cycle has been largely ignored. Therefore the fates of low-level ammonium-N and nitrate-N inputs to roadside soils impacted by salting over an extended period (decades) in the field have been studied. The use of road salts disrupts the proportional contributions of nitrate-N and ammonium-N to the mineral inorganic fraction of roadside soils. It is highly probable that the degree of salt exposure of the soil, in the longer term, controls the rates of key microbial N transformation processes, primarily by increasing soil pH. Additional influxes of ammonium-N to salt-impacted soils are rapidly nitrified therefore and, thereafter, increased leaching of nitrate-N to the local waterways occurs, which has particular relevance to the Water Framework Directive. The results reported are important when assessing the fate of inputs of ammonia to soils from atmospheric pollution. - Road salting effects ammonification and nitrification in roadside soils
19. Effect of long-term changes in soil chemistry induced by road salt applications on N-transformations in roadside soils
Energy Technology Data Exchange (ETDEWEB)
Green, Sophie M. [Environment Department, University of York, Heslington, York Y010 5DD (United Kingdom)], E-mail: [email protected]; Machin, Robert; Cresser, Malcolm S. [Environment Department, University of York, Heslington, York Y010 5DD (United Kingdom)
2008-03-15
Of several impacts of road salting on roadside soils, the potential disruption of the nitrogen cycle has been largely ignored. Therefore the fates of low-level ammonium-N and nitrate-N inputs to roadside soils impacted by salting over an extended period (decades) in the field have been studied. The use of road salts disrupts the proportional contributions of nitrate-N and ammonium-N to the mineral inorganic fraction of roadside soils. It is highly probable that the degree of salt exposure of the soil, in the longer term, controls the rates of key microbial N transformation processes, primarily by increasing soil pH. Additional influxes of ammonium-N to salt-impacted soils are rapidly nitrified therefore and, thereafter, increased leaching of nitrate-N to the local waterways occurs, which has particular relevance to the Water Framework Directive. The results reported are important when assessing the fate of inputs of ammonia to soils from atmospheric pollution. - Road salting effects ammonification and nitrification in roadside soils.
20. Organic amendment of crop soil and its relation to hotspots of bacterial nitrogen cycling
Science.gov (United States)
Pereg, Lily; McMillan, Mary
2015-04-01
Crop production in Australian soils requires a high use of fertilisers, including N, P and K for continues utilisation of the soil. Growers often grow crops in rotation of summer crop, such as cotton with winter crop, such as wheat in the same field. Growers are getting more and more aware about sustainability of the soil resources and the more adventurous ones use soil amendments, such as organic supplements in addition to the chemical fertilisers. We have collected soil samples from fields that were cultivated in preparation for planting cotton and tested the soil for its bacterial populations with potential to perform different functions, including those related to the nitrogen cycling. One of our aims was to determine whether organic amendments create hotspots for bacterial functions related to bacterial nitrogen cycling. This pan of the project will be discussed in this presentation.
1. Statistical Analysis of Nitrogen in the Soil of Constructed Wetland with Horizontal Sub-Surface Flow
Directory of Open Access Journals (Sweden)
Jakubaszek Anita
2014-06-01
Full Text Available The removal of nitrogen compounds in constructed wetlands depends on various physical, chemical and biomechanical factors as well as on conditions of the environment. The paper presents the results of a statistical analysis of the depositing of nitrogen at HSSF (horizontal subsurface flow construcred wetland. The results of the substrate showed that the highest contents of nitrogen existed in the surface soil layer up to 20 cm of the depth. Nitrogen accumulation decreased in the deposit with depth, and in the direction of the wastewater flow.
2. Impacts of twenty years of experimental warming on soil carbon, nitrogen, moisture and soil across alpine/subarctic tundra communities
DEFF Research Database (Denmark)
M. Alatalo, Juha; K. Jägerbrand, Annika; Juhanson, Jaanis
2017-01-01
High-altitude and alpine areas are predicted to experience rapid and substantial increases in future temperature, which may have serious impacts on soil carbon, nutrient and soil fauna. Here we report the impact of 20 years of experimental warming on soil properties and soil mites in three...... contrasting plant communities in alpine/subarctic Sweden. Long-term warming decreased juvenile oribatid mite density, but had no effect on adult oribatids density, total mite density, any major mite group or the most common species. Long-term warming also caused loss of nitrogen, carbon and moisture from...
3. Severe soil frost reduced losses of carbon and nitrogen from the forest floor during simulated snowmelt: A laboratory experiment
Science.gov (United States)
Andrew B. Reinmann; Pamela H. Templer; John L. Campbell
2012-01-01
Considerable progress has been made in understanding the impacts of soil frost on carbon (C) and nitrogen (N) cycling, but the effects of soil frost on C and N fluxes during snowmelt remain poorly understood. We conducted a laboratory experiment to determine the effects of soil frost on C and N fluxes from forest floor soils during snowmelt. Soil cores were collected...
4. Changes in N-transforming archaea and bacteria in soil during the establishment of bioenergy crops.
Directory of Open Access Journals (Sweden)
Yuejian Mao
Full Text Available Widespread adaptation of biomass production for bioenergy may influence important biogeochemical functions in the landscape, which are mainly carried out by soil microbes. Here we explore the impact of four potential bioenergy feedstock crops (maize, switchgrass, Miscanthus X giganteus, and mixed tallgrass prairie on nitrogen cycling microorganisms in the soil by monitoring the changes in the quantity (real-time PCR and diversity (barcoded pyrosequencing of key functional genes (nifH, bacterial/archaeal amoA and nosZ and 16S rRNA genes over two years after bioenergy crop establishment. The quantities of these N-cycling genes were relatively stable in all four crops, except maize (the only fertilized crop, in which the population size of AOB doubled in less than 3 months. The nitrification rate was significantly correlated with the quantity of ammonia-oxidizing archaea (AOA not bacteria (AOB, indicating that archaea were the major ammonia oxidizers. Deep sequencing revealed high diversity of nifH, archaeal amoA, bacterial amoA, nosZ and 16S rRNA genes, with 229, 309, 330, 331 and 8989 OTUs observed, respectively. Rarefaction analysis revealed the diversity of archaeal amoA in maize markedly decreased in the second year. Ordination analysis of T-RFLP and pyrosequencing results showed that the N-transforming microbial community structures in the soil under these crops gradually differentiated. Thus far, our two-year study has shown that specific N-transforming microbial communities develop in the soil in response to planting different bioenergy crops, and each functional group responded in a different way. Our results also suggest that cultivation of maize with N-fertilization increases the abundance of AOB and denitrifiers, reduces the diversity of AOA, and results in significant changes in the structure of denitrification community.
5. The effect of ammonium chloride and urea application on soil bacterial communities closely related to the reductive transformation of pentachlorophenol.
Science.gov (United States)
Yu, Huan-Yun; Wang, Yong-kui; Chen, Peng-cheng; Li, Fang-bai; Chen, Man-jia; Hu, Min
2014-05-15
6. Evaluation of soil water and plant nitrogen Status by nuclear techniques
International Nuclear Information System (INIS)
Reichardt, K.; Kirda, C.; Zapata, F.; Hardarson, G.; Axmann, H.
1984-01-01
Methodologies used to estimate soil water and nitrogen status of crops in field experiments are studied. Sampling procedures in a pasture experiment, consisting of three soil transects of 1.8 x 96m, one bare, one cropped to rye grass and one to alfafa, are discussed. Data are analysed with respect to soil water contents measured through the use of neutron probes, N fertilizer uptake using 15 N labelled fertilizer and N 2 fixation, also using isotopic methodology. (Author) [pt
7. Black Nitrogen as a source for the built-up of microbial biomass in soils
Science.gov (United States)
López-Martín, María; Milter, Anja; Knicker, Heike
2016-04-01
In areas with frequent wildfires, soil organic nitrogen (SON) is sequestered in pyrogenic organic matter (PyOM) due to heat-induced transformation of proteinaceous compounds into N-heterocycles, i.e. pyrrole, imidazole and indole compounds. These newly formed structures, known as Black Nitrogen (BN), have been assumed to be hardly degradable by microorganisms, thus being efficiently sequestered from the N cycle. On the other hand, a previous study showed that nitrogen of BN can be used by plants for the built-up of their biomass (de la Rosa and Knicker 2011). Thus, BN may play an important role as an N source during the recovery of the forest after a fire event. In order to obtain a more profound understanding of the role of BN within the N cycle in soils, we studied the bioavailability and incorporation of N derived from PyOM into microbial amino acids. For that, pots with soil from a burnt and an unburnt Cambisol located under a Mediterranean forest were covered with different amendments. The toppings were mixtures of unlabeled KNO3 with 15N labeled grass or 15N-labeled PyOM from burned grass and K15NO3 mixed with unlabeled grass material or PyOM. The pots were kept in the greenhouse under controlled conditions for 16 months and were sampled after 0.5, 1, 5, 8 and 16 months. From all samples the amino acids were extracted after hydrolysis (6 M HCl, 22 h, 110 °C) and quantified via gas chromatography mass spectrometry (GC/MS). The fate of 15N was followed by isotopic ratio mass spectrometry (IRMS). The results show that the contribution of extractable amino acids to total soil organic matter was always higher in the unburnt than in the burnt soil. However, with ongoing incubation their amount decreased. Already after 0.5 months, some PyOM-derived 15N was incorporated into the extractable amino acids and the amount increased with experiment time. Since this can only occur after prior microbial degradation of PyOM our results clearly support a lower biochemical
8. Soil-pit Method for Distribution and Leaching Loss of Nitrogen in Winter Wheat’s Soil, Weishan Irrigation District
Science.gov (United States)
Zhao, Erni; Xu, Lirong; Wang, Rongzhen
2018-01-01
Unreasonable application of irrigation and fertilizer will cause the waste of water and nitrogen and environmental pollution. In this paper, a series of soil-pit experiments were carried out to study the distribution and leaching loss of nitrogen in winter wheat’s soil. The results showed that NO3 - concentration at 20-80cm depth mainly responded to fertilizer application at the beginning of field experiment, but the amount of irrigation became the dominant factor with the growth of winter wheat. It is noteworthy that the distribution of NO3 - was mainly affected by the amount of fertilizer applied at the depth of 120-160cm in the whole period of growth of winter wheat. The accumulation position of NH4 + was deepened as the amount of irrigation increased, however, the maximum aggregation depth of ammonium nitrogen was no more than 80cm owing to its poor migration. It can be concluded that the influence of irrigation amount on the concentration of NH4 + in soil solution was more obvious than that of fertilizer. Compared with fertilizer, the amount of irrigation played a leading role in the utilization ratio of nitrogen and the yield of winter wheat. In summary, the best water and fertilizer treatment occurred in No.3 soil-pit, which meant that the middle amount of water and fertilizer could get higher wheat yield and less nitrogen leaching losses in the study area.
9. Transformation of soil and vegetable conditions at oil production territories
Science.gov (United States)
Gatina, Evgeniia
2017-04-01
On the territory of modern oil production soil, vegetation, ecosystem conditions of the environment are significantly transformed. Researches have been conducted on the oil production territories located in a boreal coniferous forest natural zone from 2005 to 2015. Standard geobotanical and soil methods are used. Mechanical destruction of a plant cover, change of the water conditions, intake of oil products and salty waters in ecosystems, pollution of the atmosphere are considered as the major technology-related factors defining transformation of land ecosystems at operation of the oil field. Under the mechanical destruction of a plant cover the pioneer plant communities are formed. These communities are characterized by most reduced specific wealth with prevalence of types of meadow groups of plants and presence of types of wetland groups of plants. The biodiversity of biocenosis which are affected linear infrastructure facilities of oil production territories and change of the water conditions, decreases. It is observed decrease in species wealth, simplification of structure of communities. Under the salting of soils in ecosystems there is a decrease species diversity of communities to prevalence nitrophilous and meadow plant species. At the increased content of organic substances in the soils that is a consequence of intake of oil products, is characteristic increase in specific richness of communities, introduction of types of wetland and oligotrophic groups of plants in forest communities. Influence depends on distance to an influence source. In process of removal from a source of atmospheric pollution in forest communities there is a decrease in species diversity and complication of structure of community. It is caused by introduction of types of meadow groups of plants in ecotone sites of the forest communities located near a source of influence and restoration of structural features of forest communities in process of removal from an influence source
10. Nitrogen Alters Fungal Communities in Boreal Forest Soil: Implications for Carbon Cycling
Science.gov (United States)
Allison, S. D.; Treseder, K. K.
2005-12-01
One potential effect of climate change in high latitude ecosystems is to increase soil nutrient availability. In particular, greater nitrogen availability could impact decomposer communities and lead to altered rates of soil carbon cycling. Since fungi are the primary decomposers in many high-latitude ecosystems, we used molecular techniques and field surveys to test whether fungal communities and abundances differed in response to nitrogen fertilization in a boreal forest ecosystem. We predicted that fungi that degrade recalcitrant carbon would decline under nitrogen fertilization, while fungi that degrade labile carbon would increase, leading to no net change in rates of soil carbon mineralization. The molecular data showed that basidiomycete fungi dominate the active fungal community in both fertilized and unfertilized soils. However, we found that fertilization reduced peak mushroom biomass by 79%, although most of the responsive fungi were ectomycorrhizal and therefore their capacity to degrade soil carbon is uncertain. Fertilization increased the activity of the cellulose-degrading enzyme beta-glucosidase by 78%, while protease activity declined by 39% and polyphenol oxidase, a lignin-degrading enzyme, did not respond. Rates of soil respiration did not change in response to fertilization. These results suggest that increased nitrogen availability does alter the composition of the fungal community, and its potential to degrade different carbon compounds. However, these differences do not affect the total flux of CO2 from the soil, even though the contribution to CO2 respiration from different carbon pools may vary with fertilization. We conclude that in the short term, increased nitrogen availability due to climate warming or nitrogen deposition is more likely to alter the turnover of individual carbon pools rather than total carbon fluxes from the soil. Future work should determine if changes in fungal community structure and associated differences in
11. Transformation of a petroleum pollutant during soil bioremediation experiments
Directory of Open Access Journals (Sweden)
B. JOVANCICEVIC
2008-05-01
Full Text Available The experiment of ex situ soil bioremediation was performed at the locality of the Oil Refinery in Pančevo (alluvial formation of the Danube River, Serbia polluted with an oil type pollutant. The experiments of biostimulation, bioventilation and reinoculation of an autochthonous microbial consortium were performed during the six-month period (May–November 2006. The changes in the quantity and composition of the pollutant, or the bioremediation effect, were monitored by analysis of the samples of the polluted soil taken in time spans of two weeks. In this way, from the beginning until the end of the experiment, 12 samples were collected and marked as P1–P12 (Pančevo 1–Pančevo 12. The results obtained showed that more significant changes in the composition of the oil pollutant occurred only during the last phases of the experiment (P8–P12. The activity of microorganisms was reflected in the increase of the quantity of polar oil fractions, mainly fatty acid fractions. In this way, the quantity of total eluate increased, and the quantity of the insoluble residue was reduced to a minimum, whereby the oil pollutant was transformed to a form that could be removed more efficiently and more completely from the soil, as a segment of the environment.
12. Nitrogen, organic carbon and sulphur cycling in terrestrial ecosystems: linking nitrogen saturation to carbon limitation of soil microbial processes
Czech Academy of Sciences Publication Activity Database
Kopáček, Jiří; Cosby, B. J.; Evans, C. D.; Hruška, J.; Moldan, F.; Oulehle, F.; Šantrůčková, H.; Tahovská, K.; Wright, R. F.
2013-01-01
Roč. 115, 1-3 (2013), s. 33-51 ISSN 0168-2563. [BIOGEOMON : international symposium on ecosystem behavior /7./. Northport, 15.07.2012-20.07.2012] R&D Projects: GA ČR(CZ) GAP504/12/1218 Institutional support: RVO:60077344 Keywords : nitrogen * carbon * sulphur * acidification * forest soil * modelling Subject RIV: DJ - Water Pollution ; Quality Impact factor: 3.730, year: 2013
13. Transforming Pinus pinaster forest to recreation site: preliminary effects on LAI, some forest floor, and soil properties.
Science.gov (United States)
Öztürk, Melih; Bolat, İlyas
2014-04-01
This study investigates the effects of forest transformation into recreation site. A fragment of a Pinus pinaster plantation forest was transferred to a recreation site in the city of Bartın located close to the Black Sea coast of northwestern Turkey. During the transformation, some of the trees were selectively removed from the forest to generate more open spaces for the recreationists. As a result, Leaf Area Index (LAI) decreased by 0.20 (about 11%). Additionally, roads and pathways were introduced into the site together with some recreational equipment sealing parts of the soil surface. Consequently, forest environment was altered with a semi-natural landscape within the recreation site. The purpose of this study is to assess the effects of forest transformation into recreation site particularly in terms of the LAI parameter, forest floor, and soil properties. Preliminary monitoring results indicate that forest floor biomass is reduced by 26% in the recreation site compared to the control site. Soil temperature is increased by 15% in the recreation site where selective removal of trees expanded the gaps allowing more light transmission. On the other hand, the soil bulk density which is an indicator of soil compaction is unexpectedly slightly lower in the recreation site. Organic carbon (C(org)) and total nitrogen (N(total)) together with the other physical and chemical parameter values indicate that forest floor and soil have not been exposed to much disturbance. However, subsequent removal of trees that would threaten the vegetation, forest floor, and soil should not be allowed. The activities of the recreationists are to be concentrated on the paved spaces rather than soil surfaces. Furthermore, long-term monitoring and management is necessary for both the observation and conservation of the site.
14. Nitrogen and carbon isotopes in soil with special reference to the diagnosis of organic matter
International Nuclear Information System (INIS)
Wada, Eitaro; Nakamura, Koichi.
1980-01-01
Distributions of nitrogen and carbon isotopes in terrestrial ecosystems are described based on available data and our recent findings for soil organic matters. Major processes regulating N-isotope and C-isotope ratios in biogenic substances are discussed. The biological di-nitrogen fixation and the precipitation are major sources which lower the delta 15 N value for forested soil organic matters. Denitrification enhances delta 15 N value for soil in cultivated fields. An addition of chemical fertilizer lowers 15 N content in soils. The permiation of soil water is an important factor controlling vertical profiles of delta 15 N in soil systems. Among soil organic matters, non-hydrolizable fraction seems to give unique low delta 15 N value, suggesting the utility of delta 15 N analysis in studying the nature of the fractions. delta 13 C of soil organic matter is significantly lower than that for marine sediments. delta 13 C for soil humus varies with respect to chemical forms as well as an age of soil organic matters. The variation is large in paddy fields. It is, thus, probable that delta 13 C is an useful parameter in studying the early epidiagenesis of soil organic matters. Based on the known delta 15 N-delta 13 C relationships, a two-source mixing model has been applied to assess sources of organic matters in coastal sediment. (author)
15. Microbial Nitrogen Transformations in the Oxygen Minimum Zone off Peru, 01 February 1985 to 05 March 1985 (NODC Accession 9200026)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — NITROP - 85 was the major field of experiment of an N.S.F. funded program entitled "Microbial Nitrogen Transformations in the Oxygen Minimum Zone off Peru". this...
16. Fate of fertilizer nitrogen in soil-plant system under irrigating condition. Pt.1: Effect of nitrogen level
International Nuclear Information System (INIS)
Chen Qing; Wen Xianfang; Zheng Xingyun; Pan Jiarong
1997-01-01
Three nitrogen fertilization levels including optimum rate of nitrogen applied (N1.0, 150 kg N·ha -1 ), 150% of optimum rate (N1.5, 225 kg N·ha -1 ) and 50% of optimum rate (N0.5, 75 kg N·ha -1 ) were selected to determine the fate of nitrogen in soil plant system by 15 N technique in 1994∼1995 field experiment which was conducted in Shijiazhuang. The results showed that under irrigated condition the nitrogen use efficiencies (NUE) of ammonium bicarbonate by winter wheat in fertilized treatments were 38.5%, 32.3% and 22.4% respectively, while the highest NUE of winter wheat was found in N0.5 treatment due to a relatively high fertility. The highest yield (6.8 x 10 3 kg grain·ha -1 , 14.7 x 10 3 kg top·ha -1 ) was obtained in N1.0 treatment, but nitrogen uptake and grain yield in N1.5 treatment were lower than those of other fertilizer treatments and there was no significant difference between N0.0 and N1.5 in grain yield. the highest residue of fertilizer N was determined in N1.5 treatment, of which 46% existed in the top layer of the soil (0∼50 cm). There was no significant difference in residual fertilizer N in soil between the other two treatments (31.28% in N0.5, 31.12% in N1.0). In 15 N balance calculation, the unaccounted part of applied N which was leaching down 50 cm in the soil profile as nitrate or gaseous loss through volatilization, denitrification were 30.20%, the soil profile as nitrate or gaseous loss through volatilization, denitrification were 30.20%, 36.56%, 31.25% in N0.5, N1.5 treatments, respectively. It is very important to control residual N in order to prevent N pollution and promote the growth of next crop
17. Enhancing Nitrogen Availability, Ammonium Adsorption-Desorption, and Soil pH Buffering Capacity using Composted Paddy Husk
Science.gov (United States)
Latifah, O.; Ahmed, O. H.; Abdul Majid, N. M.
2017-12-01
Form of nitrogen present in soils is one of the factors that affect nitrogen loss. Nitrate is mobile in soils because it does not absorb on soil colloids, thus, causing it to be leached by rainfall to deeper soil layers or into the ground water. On the other hand, temporary retention and timely release of ammonium in soils regulate nitrogen availability for crops. In this study, composted paddy husk was used in studies of soil leaching, buffering capacity, and ammonium adsorption and desorption to determine the: (i) availability of exchangeable ammonium, available nitrate, and total nitrogen in an acid soil after leaching the soil for 30 days, (ii) soil buffering capacity, and (iii) ability of the composted paddy husk to adsorb and desorb ammonium from urea. Leaching of ammonium and nitrate were lower in all treatments with urea and composted paddy husk compared with urea alone. Higher retention of soil exchangeable ammonium, available nitrate, and total nitrogen of the soils with composted paddy husk were due to the high buffering capacity and cation exchange capacity of the amendment to adsorb ammonium thus, improving nitrogen availability through temporary retention on the exchange sites of the humic acids of the composted paddy husk. Nitrogen availability can be enhanced if urea is amended with composted paddy husk.
18. [Relationship between Fe, Al oxides and stable organic carbon, nitrogen in the yellow-brown soils].
Science.gov (United States)
Heng, Li-Sha; Wang, Dai-Zhang; Jiang, Xin; Rao, Wei; Zhang, Wen-Hao; Guo, Chun-Yan; Li, Teng
2010-11-01
The stable organic carbon and nitrogen of the different particles were gained by oxidation of 6% NaOCl in the yellow-brown soils. The relationships between the contents of selective extractable Fe/Al and the stable organic carbon/nitrogen were investigated. It shown that amounts of dithionite-citrate-(Fe(d)) and oxalate-(Fe(o)) and pyrophosphate extractable (Fe(p)) were 6-60.8 g x kg(-1) and 0.13-4.8 g x kg(-1) and 0.03-0.47 g x kg(-1) in 2-250 microm particles, respectively; 43.1-170 g x kg(-1) and 5.9-14.0 g x kg(-1) and 0.28-0.78 g x kg(-1) in soils than in arid yellow-brown soils, and that of selective extractable Al are lower in the former than in the latter. Amounts of the stable organic carbon and nitrogen, higher in paddy yellow-brown soils than in arid yellow-brown soils, were 0.93-6.0 g x kg(-1) and 0.05-0.36 g x kg(-1) in 2-250 microm particles, respectively; 6.05-19.3 g x kg(-1) and 0.61-2.1 g x kg(-1) in stabilization index (SI(C) and SI(N)) of the organic carbon and nitrogen were 14.3-50.0 and 11.9-55.6 in 2-250 microm particles, respectively; 53.72-88.80 and 40.64-70.0 in soils than in paddy yellow-brown soils. The organic carbon and nitrogen are advantageously conserved in paddy yellow-brown soil. An extremely significant positive correlation of the stable organic carbon and nitrogen with selective extractable Fe/Al is observed. The most amounts between the stable organic carbon and nitrogen and selective extractable Fe/Al appear in clay particles, namely the clay particles could protect the soil organic carbon and nitrogen.
19. Denitrification controls in urban riparian soils: implications for reducing urban nonpoint source nitrogen pollution.
Science.gov (United States)
Li, Yangjie; Chen, Zhenlou; Lou, Huanjie; Wang, Dongqi; Deng, Huanguang; Wang, Chu
2014-09-01
The purpose of this research was to thoroughly analyze the influences of environmental factors on denitrification processes in urban riparian soils. Besides, the study was also carried out to identify whether the denitrification processes in urban riparian soils could control nonpoint source nitrogen pollution in urban areas. The denitrification rates (DR) over 1 year were measured using an acetylene inhibition technique during the incubation of intact soil cores from six urban riparian sites, which could be divided into three types according to their vegetation. The soil samples were analyzed to determine the soil organic carbon (SOC), soil total nitrogen (STN), C/N ratio, extractable NO3 (-)-N and NH4 (+)-N, pH value, soil water content (SWC), and the soil nitrification potential to evaluate which of these factors determined the final outcome of denitrification. A nitrate amendment experiment further indicated that the riparian DR was responsive to added nitrate. Although the DRs were very low (0.099 ~ 33.23 ng N2O-N g(-1) h(-1)) due to the small amount of nitrogen moving into the urban riparian zone, the spatial and temporal patterns of denitrification differed significantly. The extractable NO3 (-)-N proved to be the dominant factor influencing the spatial distribution of denitrification, whereas the soil temperature was a determinant of the seasonal DR variation. The six riparian sites could also be divided into two types (a nitrate-abundant and a nitrate-stressed riparian system) according to the soil NO3 (-)-N concentration. The DR in nitrate-abundant riparian systems was significantly higher than that in the nitrate-stressed riparian systems. The DR in riparian zones that were covered with bushes and had adjacent cropland was higher than in grass-covered riparian sites. Furthermore, the riparian DR decreased with soil depth, which was mainly attributed to the concentrated nitrate in surface soils. The DR was not associated with the SOC, STN, C/N ratio, and
20. Methane oxidation in soil profiles of Dutch and Finnish coniferous forests with different soil texture and atmospheric nitrogen deposition
NARCIS (Netherlands)
Saari, A.; Martikainen, P.J.; Ferm, A.; Ruuskanen, J.; Boer, W. de; Troelstra, S.R.; Laanbroek, H.J.
1997-01-01
We studied methane oxidation capacity in soil profiles of Dutch and Finnish coniferous forests. The Finnish sites (n = 9) had nitrogen depositions from 3 to 36 kg N ha⁻¹ a⁻¹. The deposition of N on the Dutch sites (n = 13) was higher ranging from 50 to 92 kg N ha⁻¹ a⁻¹. The Dutch sites had also
1. Methane oxidation in soil profiles of Dutch and Finnish coniferous forests with different soil texture and atmospheric nitrogen deposition
NARCIS (Netherlands)
Saari, A.; Martikainen, P.J.; Ferm, A.; Ruuskanen, J.; De Boer, W.; Troelstra, S.R.; Laanbroek, H.J.
1997-01-01
We studied methane oxidation capacity in soil profiles of Dutch and Finnish coniferous forests. The Finnish sites (n = 9) had nitrogen depositions from 3 to 36 kg N ha(-1) a(-1). The deposition of N on the Dutch sites (n = 13) was higher ranging from 50 to 92 kg N ha(-1) a(-1). The Dutch sites had
2. Nitrogen cycling in young mine soils in southwest Virginia
International Nuclear Information System (INIS)
Li, Rensheng.
1991-01-01
This investigation was conducted to study the nature of N form and dynamics in southwest Virginia mine soils. Fresh mine spoils contained a large amount of indigenous N, ranging from 650 to 2,500 mg/kg soil, which complicated N studies. Most of the indigenous N was geologic N which was unavailable to plants. The geologic N came from either 2:1 silicate minerals or coal fragments. Active N, consisting of hydrolyzable organic N and exchangeable N, comprised the minor fraction of indigenous N available to plants. With mine soil development, N accumulated mainly in the surface layer of mine soils via symbiotic fixation. Based on this fact, a simple, accurate method for measuring N accumulation which is corrected for indigenous N (Corr-N) has been developed. Corr-N is obtained by subtracting soil total N at 10-20 cm from soil total N at 0-5 cm. Under natural conditions the annual rate of N accumulation estimated by this method was 26 kg N/ha. Careful management enhanced N accumulation, and thus reduced the time required to build up soil N and to establish a vigorous, self-sustaining vegetative community in mine soils. Selecting proper overburn materials as a topsoil substitute, planting suitable legume species, and adding sewage sludge are effective methods for stimulating quick N accumulation and successful reclamation. For example, in experimental plots containing birdsfoot trefoil (Lotus corniculatus) the accumulation rate was more than 150 kg N/ha per year. This work also showed that about 43%-63% of litter N was released during one year's decomposition, and about 2.3%-11.6% of litter N was subsequently taken up by plants depending on the plant species and soil N level. This indicates that N will effectively cycle through the plant-litter-soil system once a vegetative community is established on the young mine soil
3. Divergent Effects of Nitrogen Addition on Soil Respiration in a Semiarid Grassland
OpenAIRE
Cheng Zhu; Yiping Ma; Honghui Wu; Tao Sun; Kimberly J. La Pierre; Zewei Sun; Qiang Yu
2016-01-01
Nitrogen (N) deposition has been steadily increasing for decades, with consequences for soil respiration. However, we have a limited understanding of how soil respiration responds to N availability. Here, we investigated the soil respiration responses to low and high levels of N addition (0.4?mol N m?2 yr?1 vs 1.6?mol N m?2 yr?1) over a two-year period in a semiarid Leymus chinensis grassland in Inner Mongolia, China. Our results show that low-level N addition increased soil respiration, plan...
4. Influence of the form and rate of 15N-labelled nitrogen fertilizers on nitrogen uptake by maize grown on two different soils
International Nuclear Information System (INIS)
Balabanova-Georgieva, R.; Ikonomova, E.
1996-01-01
The influence of 15 N-labelled urea and ammonium sulfate on the yield and uptake of fertilizer nitrogen and soil nitrogen by maize was studied under the conditions of pot experiments on calcareous black earth and leached black earth. The nitrogen fertilizers were applied in rates: N 1 =250 mg, N 2 =500 mg, N 3 =750 mg and N 4 =1000 mg/1 kg of soil, on phosphorus(P)-potassium(K) background (P=200 and K=600 mg/kg soil). When treating with N 3 and N 4 , the application of the whole nitrogen rate was compared with its split application. It was found that the form of the nitrogen fertilizer played no important role for the formation of the yield of biomass and the uptake of nitrogen with the yield when it is applied in low nitrogen rates and maize was grown on calcareous black earth. The yield of biomass and the uptake of nitrogen with the yield of maize reach their maximum under the conditions of calcareous black earth and high nitrogen rates applied as urea depressed the plants which proves the statement that in case of calcareous black earth application of ammonium sulfate should be preferred rather that urea, fertilization with which should be avoided. No depression of plants was observed under the conditions of leached black earth and application of high urea rates. The amount of nitrogen taken up is growing with the increasing of the nitrogen rate (excluding the N-treatment). The split application of high nitrogen rates increased notably the yield of maize-vegetation mass which proved the great ability of this crop for effective utilization of the nitrogen fertilizers when applied in portions and at suitable phases of plant vegetation. The role of the fertilizer nitrogen on the formation of the plant mass yield is much greater compared to that of the soil nitrogen; in the split application of urea the soil nitrogen plays a much bigger role than in its single application. The additional mobilization of the soil nitrogen under the influence of the applied nitrogen
5. [Effects of poplar-amaranth intercropping system on the soil nitrogen loss under different nitrogen applying levels].
Science.gov (United States)
Chu, Jun; Xue, Jian-Hui; Wu, Dian-Ming; Jin, Mei-Juan; Wu, Yong-Bo
2014-09-01
Characteristics of soil nitrogen loss were investigated based on field experiments in two types of poplar-amaranth intercropping systems (spacing: L1 2 m x 5 m, L2 2 m x 15 m) with four N application rates, i. e., 0 (N1), 91 (N2), 137 (N3) and 183 (N4) kg · hm(-2). The regulation effects on the soil surface runoff, leaching loss and soil erosion were different among the different types of intercropping systems: L1 > L2 > L3 (amaranth monocropping). Compared with the amaranth monocropping, the soil surface runoff rates of L1 and L2 decreased by 65.1% and 55.9%, the soil leaching rates of L1 and L2 with a distance of 0.5 m from the poplar tree row de- creased by 30.0% and 28.9%, the rates with a distance of 1. 5 m decreased by 25. 6% and 21.9%, and the soil erosion rates decreased by 65.0% and 55.1%, respectively. The control effects of two intercropping systems on TN, NO(3-)-N and NH(4+)-N in soil runoff and leaching loss were in the order of L1 > L2 > L3. Compared with the amaranth monocropping, TN, NO(3-)-N and NH(4+)-N loss rates in soil runoff of L1 decreased by 62.9%, 45.1% and 69.2%, while the loss rates of L2 decreased by 23.4%, 6.9% and 46.2% under N1 (91 kg · hm(-2)), respectively. High- er tree-planting density and closer positions to the polar tree row were more effective on controlling the loss rates of NO(3-)-N and NH(4+)-N caused by soil leaching. The loss proportion of NO(3-)-N in soil runoff decreased with the increasing nitrogen rate under the same tree-planting density, while that of NH(4+)-N increased. Leaching loss of NO(3-)-N had a similar trend with that of NH(4+)-N, i. e. , N3 > N2 > N1 > N0.
6. Biological soil crusts accelerate the nitrogen cycle through large NO and HONO emissions in drylands.
Science.gov (United States)
Weber, Bettina; Wu, Dianming; Tamm, Alexandra; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J; Su, Hang; Pöschl, Ulrich
2015-12-15
Reactive nitrogen species have a strong influence on atmospheric chemistry and climate, tightly coupling the Earth's nitrogen cycle with microbial activity in the biosphere. Their sources, however, are not well constrained, especially in dryland regions accounting for a major fraction of the global land surface. Here, we show that biological soil crusts (biocrusts) are emitters of nitric oxide (NO) and nitrous acid (HONO). Largest fluxes are obtained by dark cyanobacteria-dominated biocrusts, being ∼20 times higher than those of neighboring uncrusted soils. Based on laboratory, field, and satellite measurement data, we obtain a best estimate of ∼1.7 Tg per year for the global emission of reactive nitrogen from biocrusts (1.1 Tg a(-1) of NO-N and 0.6 Tg a(-1) of HONO-N), corresponding to ∼20% of global nitrogen oxide emissions from soils under natural vegetation. On continental scales, emissions are highest in Africa and South America and lowest in Europe. Our results suggest that dryland emissions of reactive nitrogen are largely driven by biocrusts rather than the underlying soil. They help to explain enigmatic discrepancies between measurement and modeling approaches of global reactive nitrogen emissions. As the emissions of biocrusts strongly depend on precipitation events, climate change affecting the distribution and frequency of precipitation may have a strong impact on terrestrial emissions of reactive nitrogen and related climate feedback effects. Because biocrusts also account for a large fraction of global terrestrial biological nitrogen fixation, their impacts should be further quantified and included in regional and global models of air chemistry, biogeochemistry, and climate.
7. Monitoring of soil organic carbon and nitrogen stocks in different ...
African Journals Online (AJOL)
SOC and SN stocks are a function of the SOC and SN concentrations and the bulk density of the soil that are prone to changes under land use types and soil erosion. The objective of this study was to evaluate SOC and SN stock in different land use types under surface erosion at catchment scale. In view of this, bulk density, ...
8. Soil nitrogen mineralization not affected by grass species traits
Science.gov (United States)
Maged Ikram Nosshi; Jack Butler; M. J. Trlica
2007-01-01
Species N use traits was evaluated as a mechanism whereby Bromus inermis (Bromus), an established invasive, might alter soil N supply in a Northern mixed-grass prairie. We compared soils under stands of Bromus with those from three representative native grasses of different litter C/N: Andropogon...
9. Total carbon and nitrogen in the soils of the world
NARCIS (Netherlands)
Batjes, N.H.
2014-01-01
The soil is important in sequestering atmospheric CO2 and in emitting trace gases (e.g. CO2, CH4 and N2O) that are radiatively active and enhance the ‘greenhouse’ effect. Land use changes and predicted global warming, through their effects on net primary productivity, the plant community and soil
10. Fire frequency drives decadal changes in soil carbon and nitrogen and ecosystem productivity
Science.gov (United States)
Pellegrini, Adam F. A.; Ahlström, Anders; Hobbie, Sarah E.; Reich, Peter B.; Nieradzik, Lars P.; Staver, A. Carla; Scharenbroch, Bryant C.; Jumpponen, Ari; Anderegg, William R. L.; Randerson, James T.; Jackson, Robert B.
2018-01-01
Fire frequency is changing globally and is projected to affect the global carbon cycle and climate. However, uncertainty about how ecosystems respond to decadal changes in fire frequency makes it difficult to predict the effects of altered fire regimes on the carbon cycle; for instance, we do not fully understand the long-term effects of fire on soil carbon and nutrient storage, or whether fire-driven nutrient losses limit plant productivity. Here we analyse data from 48 sites in savanna grasslands, broadleaf forests and needleleaf forests spanning up to 65 years, during which time the frequency of fires was altered at each site. We find that frequently burned plots experienced a decline in surface soil carbon and nitrogen that was non-saturating through time, having 36 per cent (±13 per cent) less carbon and 38 per cent (±16 per cent) less nitrogen after 64 years than plots that were protected from fire. Fire-driven carbon and nitrogen losses were substantial in savanna grasslands and broadleaf forests, but not in temperate and boreal needleleaf forests. We also observe comparable soil carbon and nitrogen losses in an independent field dataset and in dynamic model simulations of global vegetation. The model study predicts that the long-term losses of soil nitrogen that result from more frequent burning may in turn decrease the carbon that is sequestered by net primary productivity by about 20 per cent of the total carbon that is emitted from burning biomass over the same period. Furthermore, we estimate that the effects of changes in fire frequency on ecosystem carbon storage may be 30 per cent too low if they do not include multidecadal changes in soil carbon, especially in drier savanna grasslands. Future changes in fire frequency may shift ecosystem carbon storage by changing soil carbon pools and nitrogen limitations on plant growth, altering the carbon sink capacity of frequently burning savanna grasslands and broadleaf forests.
11. Slope position and Soil Lithological Effects on Live Leaf Nitrogen Concentration.
Science.gov (United States)
Szink, I.; Adams, T. S.; Orr, A. S.; Eissenstat, D. M.
2017-12-01
Soil lithology has been shown to have an effect on plant physiology from the roots to the leaves. Soils at ridgetop positions are typically more shallow and drier than soils at valley floor positions. Additionally, sandy soils tend to have a much lower water holding capacity and can be much harder for plants to draw nutrients from. We hypothesized that leaves from trees in shale derived soil at ridgetop positions will have lower nitrogen concentration than those in valley floor positions, and that this difference will be more pronounced in sandstone derived soils. This is due to the movement of nitrogen through the soil in a catchment, and the holding and exchange capacities of shale and sandstone lithologies. To test this, we collected live leaves using shotgun sampling from two locations in Central Pennsylvania from the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO); one location where soils are underlain by the Rose Hill Shale, and one from where soils are underlain by the Tuscarora Sandstone formation. We then measured, dried, and massed in order to determine specific leaf area (SLA). Afterwards, we powderized the leaves to determined their C:N ratio using a CE Instruments EA 1110 CHNS-O elemental Analyzer based on the "Dumas Method". We found that live leaves of the same species at higher elevations had lower nitrogen concentrations than those at lower elevations, which is consistent with our hypothesis. However, the comparison of leaves from all species in the catchment is not as strong, suggesting that there is a species specific effect on nitrogen concentration within leaves. We are currently processing additional leaves from other shale and sandstone sites. These results highlight the effect of abiotic environments on leaf nutrient concentrations, and the connection between belowground and aboveground tree physiology.
12. Microbial Nitrogen-Cycle Gene Abundance in Soil of Cropland Abandoned for Different Periods.
Directory of Open Access Journals (Sweden)
Huhe
Full Text Available In Inner Mongolia, steppe grasslands face desertification or degradation because of human overuse and abandonment after inappropriate agricultural management. The soils in these abandoned croplands exist in heterogeneous environments characterized by widely fluctuating microbial growth. Quantitative polymerase chain reaction analysis of microbial genes encoding proteins involved in the nitrogen cycle was used to study Azotobacter species, nitrifiers, and denitrifiers in the soils from steppe grasslands and croplands abandoned for 2, 6, and 26 years. Except for nitrifying archaea and nitrous oxide-reducing bacteria, the relative genotypic abundance of microbial communities involved in nitrogen metabolism differed by approximately 2- to 10-fold between abandoned cropland and steppe grassland soils. Although nitrogen-cycle gene abundances varied with abandonment time, the abundance patterns of nitrogen-cycle genes separated distinctly into abandoned cropland versus light-grazing steppe grassland, despite the lack of any cultivation for over a quarter-century. Plant biomass and plant diversity exerted a significant effect on the abundance of microbial communities that mediate the nitrogen cycle (P < 0.002 and P < 0.03, respectively. The present study elucidates the ecology of bacteria that mediate the nitrogen cycle in recently abandoned croplands.
13. Microbial Nitrogen-Cycle Gene Abundance in Soil of Cropland Abandoned for Different Periods.
Science.gov (United States)
Huhe; Borjigin, Shinchilelt; Buhebaoyin; Wu, Yanpei; Li, Minquan; Cheng, Yunxiang
2016-01-01
In Inner Mongolia, steppe grasslands face desertification or degradation because of human overuse and abandonment after inappropriate agricultural management. The soils in these abandoned croplands exist in heterogeneous environments characterized by widely fluctuating microbial growth. Quantitative polymerase chain reaction analysis of microbial genes encoding proteins involved in the nitrogen cycle was used to study Azotobacter species, nitrifiers, and denitrifiers in the soils from steppe grasslands and croplands abandoned for 2, 6, and 26 years. Except for nitrifying archaea and nitrous oxide-reducing bacteria, the relative genotypic abundance of microbial communities involved in nitrogen metabolism differed by approximately 2- to 10-fold between abandoned cropland and steppe grassland soils. Although nitrogen-cycle gene abundances varied with abandonment time, the abundance patterns of nitrogen-cycle genes separated distinctly into abandoned cropland versus light-grazing steppe grassland, despite the lack of any cultivation for over a quarter-century. Plant biomass and plant diversity exerted a significant effect on the abundance of microbial communities that mediate the nitrogen cycle (P nitrogen cycle in recently abandoned croplands.
14. Dissolved organic nitrogen (DON) losses from nested artificially drained lowland catchments with contrasting soil types
Science.gov (United States)
Tiemeyer, Bärbel; Kahle, Petra; Lennartz, Bernd
2010-05-01
Artificial drainage is a common practice to improve moisture and aeration conditions of agricultural land. It shortens the residence time of water in the soil and may therefore contribute to the degradation of peatlands as well as to the still elevated level of diffuse pollution of surface water bodies, particularly if flow anomalies like preferential flow cause a further acceleration of water and solute fluxes. Especially in the case of nitrate, artificially drained sub-catchments are found to control the catchment-scale nitrate losses. However, it is frequently found that nitrate losses and nitrogen field balances do not match. At the same time, organic fertilizers are commonly applied and, especially in lowland catchments, organic soils have been drained for agricultural use. Thus, the question arises whether dissolved organic nitrogen (DON) forms an important component of the nitrogen losses from artificially drained catchments. However, in contrast to nitrate and even to dissolved organic carbon (DOC), this component is frequently overlooked, especially in nested catchment studies with different soil types and variable land use. Here, we will present data from a hierarchical water quantity and quality measurement programme in the federal state Mecklenburg-Vorpommern (North-Eastern Germany). The monitoring programme in the pleistocene lowland catchment comprises automatic sampling stations at a collector drain outlet (4.2 ha catchment), at a ditch draining arable land on mineral soils (179 ha), at a ditch mainly draining grassland on organic soils (85 ha) and at a brook with a small rural catchment (15.5 km²) of mixed land use and soil types. At all sampling stations, daily to weekly composite samples were taken, while the discharge and the meteorological data were recorded continuously. Water samples were analyzed for nitrate-nitrogen, ammonium-nitrogen and total nitrogen. We will compare two years: 2006/07 was a very wet year (P = 934 mm) with a high summer
15. Response of soil fauna to simulated nitrogen deposition: a nursery experiment in subtropical China.
Science.gov (United States)
Xu, Guo-Liang; Mo, Jiang-Ming; Fu, Sheng-Lei; Gundersen, Per; Zhou, Guo-Yi; Xue, Jing-Hua
2007-01-01
We studied the responses of soil fauna to a simulated nitrogen deposition in nursery experimental plots in Subtropical China. Dissolved NH4NO3 was applied to the soil by spraying twice per month for 16 months, starting in January 2003 with treatments of 0, 5, 10, 15 and 30 gN/(m2 x a). Soil fauna was sampled after 6, 9, 13 and 16 months of treatment in three soil depths (0-5 cm, 5-10 cm, 10-15 cm). Soil available N increased in correspondence with the increasing N treatment, whereas soil pH decreased. Bacterial and fungal densities were elevated by the N treatment. Soil fauna increased in the lower nitrogen treatments but decreased in the higher N treatments, which might indicate that there was a threshold around 10 gN/(m2 x a) for the stimulating effects of N addition. The N effects were dependent on the soil depth and sampling time. The data also suggested that the effects of the different N treatments were related to the level of N saturation, especially the concentration of NO3- in the soil.
16. Dissolved organic carbon and nitrogen release from Holocene permafrost and seasonally frozen soils
Science.gov (United States)
Wickland, K.; Waldrop, M. P.; Koch, J. C.; Jorgenson, T.; Striegl, R. G.
2017-12-01
Permafrost (perennially frozen) soils store vast amounts of carbon (C) and nitrogen (N) that are vulnerable to mobilization to the atmosphere as greenhouse gases and to terrestrial and aquatic ecosystems as dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) upon thaw. Such releases will affect the biogeochemistry of arctic and boreal regions, yet little is known about active layer (seasonally frozen) and permafrost source variability that determines DOC and TDN mobilization. We quantified DOC and TDN leachate yields from a range of active layer and permafrost soils in Alaska varying in age and C and N content to determine potential release upon thaw. Soil cores from the upper 1 meter were collected in late winter, when soils were frozen, from three locations representing a range in geographic position, landscape setting, permafrost depth, and soil types across interior Alaska. Two 15 cm-thick segments were extracted from each core: a deep active-layer horizon and a shallow permafrost horizon. Soils were thawed and leached for DOC and TDN yields, dissolved organic matter optical properties, and DOC biodegradability; soils were analyzed for C and N content, and radiocarbon content. Soils had wide-ranging C and N content (<1-44% C, <0.1-2.3% N), and varied in radiocarbon age from 450-9200 years before present - thus capturing typical ranges of boreal and arctic soils. Soil DOC and TDN yields increased linearly with soil C and N content, and decreased with increasing radiocarbon age. However, across all sites DOC and TDN yields were significantly greater from permafrost soils (0.387 ± 0.324 mg DOC g-1 soil; 0.271 ± 0.0271 mg N g-1 soil) than from active layer soils (0.210 ± 0.192 mg DOC g-1 soil; 0.00716 ± 0.00569 mg N g-1 soil). DOC biodegradability increased with increasing radiocarbon age, and was statistically similar for active layer and permafrost soils. Our findings suggest that the continuously frozen state of permafrost soils has preserved
17. Seasonal Patterns of Soil Respiration and Related Soil Biochemical Properties under Nitrogen Addition in Winter Wheat Field
Science.gov (United States)
Liang, Guopeng; Houssou, Albert A.; Wu, Huijun; Cai, Dianxiong; Wu, Xueping; Gao, Lili; Li, Jing; Wang, Bisheng; Li, Shengping
2015-01-01
Understanding the changes of soil respiration under increasing N fertilizer in cropland ecosystems is crucial to accurately predicting global warming. This study explored seasonal variations of soil respiration and its controlling biochemical properties under a gradient of Nitrogen addition during two consecutive winter wheat growing seasons (2013–2015). N was applied at four different levels: 0, 120, 180 and 240 kg N ha-1 year-1 (denoted as N0, N12, N18 and N24, respectively). Soil respiration exhibited significant seasonal variation and was significantly affected by soil temperature with Q10 ranging from 2.04 to 2.46 and from 1.49 to 1.53 during 2013–2014 and 2014–2015 winter wheat growing season, respectively. Soil moisture had no significant effect on soil respiration during 2013–2014 winter wheat growing season but showed a significant and negative correlation with soil respiration during 2014–2015 winter wheat growing season. Soil respiration under N24 treatment was significantly higher than N0 treatment. Averaged over the two growing seasons, N12, N18 and N24 significantly increased soil respiration by 13.4, 16.4 and 25.4% compared with N0, respectively. N addition also significantly increased easily extractable glomalin-related soil protein (EEG), soil organic carbon (SOC), total N, ammonium N and nitrate N contents. In addition, soil respiration was significantly and positively correlated with β-glucosidase activity, EEG, SOC, total N, ammonium N and nitrate N contents. The results indicated that high N fertilization improved soil chemical properties, but significantly increased soil respiration. PMID:26629695
18. Seasonal Patterns of Soil Respiration and Related Soil Biochemical Properties under Nitrogen Addition in Winter Wheat Field.
Science.gov (United States)
Liang, Guopeng; Houssou, Albert A; Wu, Huijun; Cai, Dianxiong; Wu, Xueping; Gao, Lili; Li, Jing; Wang, Bisheng; Li, Shengping
2015-01-01
Understanding the changes of soil respiration under increasing N fertilizer in cropland ecosystems is crucial to accurately predicting global warming. This study explored seasonal variations of soil respiration and its controlling biochemical properties under a gradient of Nitrogen addition during two consecutive winter wheat growing seasons (2013-2015). N was applied at four different levels: 0, 120, 180 and 240 kg N ha(-1) year(-1) (denoted as N0, N12, N18 and N24, respectively). Soil respiration exhibited significant seasonal variation and was significantly affected by soil temperature with Q10 ranging from 2.04 to 2.46 and from 1.49 to 1.53 during 2013-2014 and 2014-2015 winter wheat growing season, respectively. Soil moisture had no significant effect on soil respiration during 2013-2014 winter wheat growing season but showed a significant and negative correlation with soil respiration during 2014-2015 winter wheat growing season. Soil respiration under N24 treatment was significantly higher than N0 treatment. Averaged over the two growing seasons, N12, N18 and N24 significantly increased soil respiration by 13.4, 16.4 and 25.4% compared with N0, respectively. N addition also significantly increased easily extractable glomalin-related soil protein (EEG), soil organic carbon (SOC), total N, ammonium N and nitrate N contents. In addition, soil respiration was significantly and positively correlated with β-glucosidase activity, EEG, SOC, total N, ammonium N and nitrate N contents. The results indicated that high N fertilization improved soil chemical properties, but significantly increased soil respiration.
19. Martensitic transformations, structure, and strengthness of processed high-nitrogen and high-carbon ferrous alloys
Science.gov (United States)
Kaputkina, L. M.; Prokoshkina, V. G.
2003-10-01
Structures and properties of metastable austenitic alloys Fe-18Cr-16Ni-I2Mn-(0.17 to 0. 50)N, Fe-18Cr-12Mn-(0.48 to 1.12)N, Fe-18Cr-(0.1 to 1.18)N, and Fe-(12 to 20)Ni-(0.6 to 1.3)C, Fe-(6 to 8)Mn-(0.6 to 1.0)C, Fe-(5 to 6)Cr-(4 to 5)Mn-(0.6 to 0.8)C, Fe-6Cr-(1.0 to 1.3)C resulting from martensitic transformations under cooling and cold deformation (CD), as well as following tempering processes, were studied by magnetometry, X-ray and electron microscopy analyses, hardness measurements and mechanical properties tests. Martensite with a b.c.t. lattice was formed in all alloys with M_s{>}-196^circC during cooling. Under CD transformations of γ{to}α, γ{to}\\varepsilon{to}α, or γ{to}\\varepsilon types were realized depending on the alloy composition. Carbon increased but nitrogen decreased stacking fault energy. Thus carbon assists α-martensite formation but nitrogen promotese. As CD level and/or concentration of carbon and nitrogen increase residual stresses resulting from the CD also increase. The martensitic transformation during CD can decrease the residual stresses. Kinetic of tempering of b.c.t. thermal martensite differs from those of CD-induced martensite. In the second case, deformation aging, texture, and residual stresses are more visible. The maximal strengthening under CD takes place in (Mn+N)-steels. (Cr+N) and (Cr+Mn+N)-steels are high-strength, non-magnetic and corrosion resistant and are easily hardened by a low level of plastic deformation.
20. Effects of Nitrogen Enrichment, Wildfire, and Harvesting on Forest-Soil Carbon and Nitrogen
Science.gov (United States)
Jennifer L. Parker; Ivan J. Fernandez; Lindsey E. Rustad; Stephen A. Norton
2001-01-01
Northern forest soils represent large reservoirs of C and N that may be altered by ecosystem perturbations. Soils at three paired watershed in Maine were investigated as case studies of experimentally elevated N deposition, wildfire, and whole-tree harvesting. Eight years of experimental (NH4)2SO4...
1. Water and nitrogen distribution in uncropped ridgetilled soil under ...
African Journals Online (AJOL)
A ridge-tillage configuration, with placement of nitrate nitrogen (NO3--N) or its source in the elevated portion of the ridge, can potentially isolate fertilizer from downward water flow and minimize nitrate leaching. In the experiment, the simultaneous distribution of water, nitrate, and ammonium under three ridge widths was ...
2. Controls on soil solution nitrogen along an altitudinal gradient in the Scottish uplands.
Science.gov (United States)
Jackson-Blake, L; Helliwell, R C; Britton, A J; Gibbs, S; Coull, M C; Dawson, L
2012-08-01
Nitrogen (N) deposition continues to threaten upland ecosystems, contributing to acidification, eutrophication and biodiversity loss. We present results from a monitoring study aimed at investigating the fate of this deposited N within a pristine catchment in the Cairngorm Mountains (Scotland). Six sites were established along an elevation gradient (486-908 m) spanning the key habitats of temperate maritime uplands. Bulk deposition chemistry, soil carbon content, soil solution chemistry, soil temperature and soil moisture content were monitored over a 5 year period. Results were used to assess spatial variability in soil solution N and to investigate the factors and processes driving this variability. Highest soil solution inorganic N concentrations were found in the alpine soils at the top of the hillslope. Soil carbon stock, soil solution dissolved organic carbon (DOC) and factors representing site hydrology were the best predictors of NO(3)(-) concentration, with highest concentrations at low productivity sites with low DOC and freely-draining soils. These factors act as proxies for changing net biological uptake and soil/water contact time, and therefore support the hypothesis that spatial variations in soil solution NO(3)(-) are controlled by habitat N retention capacity. Soil percent carbon was a better predictor of soil solution inorganic N concentration than mass of soil carbon. NH(4)(+) was less affected by soil hydrology than NO(3)(-) and showed the effects of net mineralization inputs, particularly at Racomitrium heath and peaty sites. Soil solution dissolved organic N concentration was strongly related to both DOC and temperature, with a stronger temperature effect at more productive sites. Due to the spatial heterogeneity in N leaching potential, a fine-scale approach to assessing surface water vulnerability to N leaching is recommended over the broad scale, critical loads approach currently in use, particularly for sensitive areas. Copyright © 2012
3. Effects of three years of simulated nitrogen deposition on soil nitrogen dynamics and greenhouse gas emissions in a Korean pine plantation of northeast China.
Science.gov (United States)
Song, Lei; Tian, Peng; Zhang, Jinbo; Jin, Guangze
2017-12-31
Continuously enhanced nitrogen (N) deposition alters the pattern of N and carbon (C) transformations, and thus influences greenhouse gas emissions. It is necessary to clarify the effect of N deposition on greenhouse gas emissions and soil N dynamics for an accurate assessment of C and N budgets under increasing N deposition. In this study, four simulated N deposition treatments (control [CK: no N addition], low-N [L: 20kgNha -1 yr -1 ], medium-N [M: 40kgNha -1 yr -1 ], and high-N [H: 80kgNha -1 yr -1 ]) were operated from 2014. Carbon dioxide, methane and nitrous oxide fluxes were monitored semimonthly, as were soil variables such as temperature, moisture and the concentrations of total dissolved N (TDN), NO 3 - , NO 2 - , NH 4 + , and dissolved organic N (DON) in soil solutions. The simulated N deposition resulted in a significant increase in TDN, NO 3 - and DON concentrations in soil solutions. The average CO 2 emission rate ranged from 222.6mgCO 2 m -2 h -1 in CK to 233.7mgCO 2 m -2 h -1 in the high-N treatment. Three years of simulated N deposition had no effect on soil CO 2 emission, which was mainly controlled by soil temperature. The mean N 2 O emission rate during the whole 3years was 0.02mgN 2 Om -2 h -1 for CK, which increased significantly to 0.05mgN 2 Om -2 h -1 in the high-N treatment. The N 2 O emission rate positively correlated with NH 4 + concentrations, and negatively correlated with soil moisture. The average CH 4 flux during the whole 3years was -0.74μgCH 4 m -2 h -1 in CK, which increased to 1.41μgCH 4 m -2 h -1 in the low-N treatment. CH 4 flux positively correlated with NO 3 - concentrations. These results indicate that short-term N deposition did not affect soil CO 2 emissions, while CH 4 and N 2 O emissions were sensitive to N deposition. Copyright © 2017 Elsevier B.V. All rights reserved.
4. Organic Nitrogen in Atmospheric Drops and Particles: Concentrations, (Limited) Speciation, and Chemical Transformations
Science.gov (United States)
Anastasio, C.; Zhang, Q.
2003-12-01
While quite a bit is known of the concentrations, speciation, and chemistry of inorganic forms of nitrogen in the atmosphere, the same cannot be said for organic forms. Despite this, there is growing evidence that organic N (ON) is ubiquitous in the atmosphere, especially in atmospheric condensed phases such as fog/cloud drops and aerosol particles. Although the major compounds that make up organic N are generally unknown, as are the sources of these compounds, it is clear that there are significant fluxes of ON between the atmosphere and ecosystems. It also appears that organic N can have significant effects in both spheres. The goal of our recent work in this area has been to better describe the atmospheric component of the biogeochemistry of organic nitrogen. Based on particle, gas, and fogwater samples from Northern California we have made three major findings: 1) Organic N represents a significant component, approximately 20%, of the total atmospheric N loading in these samples. This is broadly consistent with studies from other locations. 2) Amino compounds, primarily as combined amino acids, account for approximately 20% of the measured ON in our condensed phase samples. Given the properties of amino acids, these compounds could significantly affect the chemical and physical properties of atmospheric particles. 3) Organic nitrogen in atmospheric particles and drops is transformed to inorganic forms - primarily ammonium, nitrate, and nitrogen oxides (NOx) - during exposure to sunlight and/or ozone. These chemical reactions likely increase the bioavailability of the condensed phase nitrogen pool and enhance its biological effects after deposition to ecosystems.
5. Alterations in soil microbial activity and N-transformation processes due to sulfadiazine loads in pig-manure
International Nuclear Information System (INIS)
Kotzerke, Anja; Sharma, Shilpi; Schauss, Kristina; Heuer, Holger; Thiele-Bruhn, Soeren; Smalla, Kornelia; Wilke, Berndt-Michael; Schloter, Michael
2008-01-01
Most veterinary drugs enter the environment via manure application. However, it is unclear how these substances interact with soil biota. Therefore, it was the aim of the present study to investigate the effects of manure containing different concentrations of the antibiotic sulfadiazine (SDZ) on the soil microbial communities. It was shown that manure alone has a stimulating effect on microbial activity. Only potential nitrification was negatively influenced by manure application. The addition of SDZ to the manure reduced microbial activity. Depending on the SDZ concentration, levels of activity were in the range of the control soil without manure application. Also, selected processes in nitrogen turnover were negatively influenced by the addition of SDZ to the manure, with nitrification being the only exception. The effects were visible for up to 4 days after application of the manure with or without SDZ and were correlated with the bioavailability of the antibiotic. - This study gives first insights into the effects of manure containing the antibiotic sulfadiazine on microbial activity and nitrogen transformation potentials in soil
6. EFFECTS OF NITRIFICATION INHIBITORS ON MINERAL NITROGEN DYNAMICS IN AGRICULTURE SOILS
OpenAIRE
Ferisman Tindaon; Gero Benckiser; ohannes Carl Gottlieb Ottow
2011-01-01
Experiments were conducted under laboratory conditions to elucidate the effect of three nitrification inhibitors viz, 3.4dimethylpyrazo-lephosphate (DMPP), 4-Chlormethylpyrazole (ClMP) and dicyandiamide (DCD) on mineral nitrogen dynamics of (NH4)2SO4 in soil incubated at 25oC in soils. The quantitative determination of ammonium, nitrite and nitrate were carried out spectrophotometrically, while potential denitrify-cation capacity (PDC) was measured gas chromatographically. DMPP, ClMP and DCD ...
7. Effects of Nitrification Inhibitors on Mineral Nitrogen Dynamics in Agriculture Soils
OpenAIRE
Tindaon, Ferisman; Benckiser, Gero; Ottow, Johannes Carl Gottlieb
2011-01-01
Experiments were conducted under laboratory conditions to elucidate the effect of three nitrification inhibitors viz, 3.4dime-thylpyrazo-lephosphate (DMPP), 4-Chlormethylpyrazole (ClMP) and dicyandiamide (DCD) on mineral nitrogen dynamics of (NH4)2SO4 in soil incubated at 25oC in soils. The quantitative determination of ammonium, nitrite and nitrate were carried out spectrophotometrically, while potential denitrify-cation capacity (PDC) was measured gas chromatographically. DMPP, ClMP and DCD...
8. Comparisons of soil nitrogen mass balances for an ombrotrophic bog and a minerotrophic fen in northern Minnesota
Science.gov (United States)
Brian H. Hill; Terri M. Jicha; LaRae L.P. Lehto; Colleen M. Elonen; Stephen D. Sebestyen; Randy Kolka
2016-01-01
Wecompared nitrogen (N) storage and flux in soils froman ombrotrophic bogwith that of a minerotrophic fen to quantify the differences in N cycling between these two peatlands types in northernMinnesota (USA). Precipitation, atmospheric deposition, and bog and fen outflowswere analyzed for nitrogen species. Upland and peatland soil sampleswere analyzed for N content,...
9. Irrigation and Nitrogen Regimes Promote the Use of Soil Water and Nitrate Nitrogen from Deep Soil Layers by Regulating Root Growth in Wheat.
Science.gov (United States)
Liu, Weixing; Ma, Geng; Wang, Chenyang; Wang, Jiarui; Lu, Hongfang; Li, Shasha; Feng, Wei; Xie, Yingxin; Ma, Dongyun; Kang, Guozhang
2018-01-01
Unreasonably high irrigation levels and excessive nitrogen (N) supplementation are common occurrences in the North China Plain that affect winter wheat production. Therefore, a 6-yr-long stationary field experiment was conducted to investigate the effects of irrigation and N regimes on root development and their relationship with soil water and N use in different soil layers. Compared to the non-irrigated treatment (W0), a single irrigation at jointing (W1) significantly increased yield by 3.6-45.6%. With increases in water (W2, a second irrigation at flowering), grain yield was significantly improved by 14.1-45.3% compared to the W1 treatments during the drier growing seasons (2010-2011, 2012-2013, and 2015-2016). However, under sufficient pre-sowing soil moisture conditions, grain yield was not increased, and water use efficiency (WUE) decreased significantly in the W2 treatments during normal precipitation seasons (2011-2012, 2013-2014, and 2014-2015). Irrigating the soil twice inhibited root growth into the deeper soil depth profiles and thus weakened the utilization of soil water and NO 3 -N from the deep soil layers. N applications increased yield by 19.1-64.5%, with a corresponding increase in WUE of 66.9-83.9% compared to the no-N treatment (N0). However, there was no further increase in grain yield and the WUE response when N rates exceeded 240 and 180 kg N ha -1 , respectively. A N application rate of 240 kg ha -1 facilitated root growth in the deep soil layers, which was conducive to utilization of soil water and NO 3 -N and also in reducing the residual NO 3 -N. Correlation analysis indicated that the grain yield was significantly positively correlated with soil water storage (SWS) and nitrate nitrogen accumulation (SNA) prior to sowing. Therefore, N rates of 180-240 kg ha -1 with two irrigations can reduce the risk of yield loss that occurs due to reduced precipitation during the wheat growing seasons, while under better soil moisture conditions, a
10. Fungal endophyte Phomopsis liquidambari affects nitrogen transformation processes and related microorganisms in the rice rhizosphere
Directory of Open Access Journals (Sweden)
Bo eYang
2015-09-01
Full Text Available The endophytic fungus Phomopsis liquidambari performs an important ecosystem service by assisting its host with acquiring soil nitrogen (N, but little is known regarding how this fungus influences soil N nutrient properties and microbial communities. In this study, we investigated the impact of P. liquidambari on N dynamics，the abundance and composition of N cycling genes in rhizosphere soil treated with three levels of N (urea. Ammonia-oxidizing archaea (AOA, ammonia-oxidizing bacteria (AOB and diazotrophs were assayed using quantitative real-time polymerase chain reaction and denaturing gradient gel electrophoresis at four rice growing stages (S0: before planting, S1: tillering stage, S2: grain filling stage, and S3: ripening stage. A significant increase in the available nitrate and ammonium contents was found in the rhizosphere soil of endophyte-infected rice under low N conditions. Moreover, P. liquidambari significantly increased the potential nitrification rates (PNR, affected the abundance and community structure of AOA, AOB and diazotrophs under low N conditions in the S1 and S2 stages. The root exudates were determined due to their important role in rhizosphere interactions. P. liquidambari colonization altered the exudation of organic compounds by rice roots and P. liquidambari increased the concentration of soluble saccharides, total free amino acids and organic acids
11. Effect of the major components of industrial air pollution on nonsymbiotic nitrogen-fixation activity in soil
Energy Technology Data Exchange (ETDEWEB)
Islamov, S S; Chunderova, A I
1976-01-01
Industrial pollution of atmosphere inhibits the activity of non-symbiotic nitrogen fixation in soils. The inhibiting effect of polluted air can be explained by the presence of carbon monoxide and nitrogen dioxide in it. Sulfur dioxide does not depress the nitrogenase complex of aerobic and anaerobic nitrogen fixing microorganisms.
12. Soil warming alters nitrogen cycling in a New England forest: implications for ecosystem function and structure.
Science.gov (United States)
Butler, S M; Melillo, J M; Johnson, J E; Mohan, J; Steudler, P A; Lux, H; Burrows, E; Smith, R M; Vario, C L; Scott, L; Hill, T D; Aponte, N; Bowles, F
2012-03-01
Global climate change is expected to affect terrestrial ecosystems in a variety of ways. Some of the more well-studied effects include the biogeochemical feedbacks to the climate system that can either increase or decrease the atmospheric load of greenhouse gases such as carbon dioxide and nitrous oxide. Less well-studied are the effects of climate change on the linkages between soil and plant processes. Here, we report the effects of soil warming on these linkages observed in a large field manipulation of a deciduous forest in southern New England, USA, where soil was continuously warmed 5°C above ambient for 7 years. Over this period, we have observed significant changes to the nitrogen cycle that have the potential to affect tree species composition in the long term. Since the start of the experiment, we have documented a 45% average annual increase in net nitrogen mineralization and a three-fold increase in nitrification such that in years 5 through 7, 25% of the nitrogen mineralized is then nitrified. The warming-induced increase of available nitrogen resulted in increases in the foliar nitrogen content and the relative growth rate of trees in the warmed area. Acer rubrum (red maple) trees have responded the most after 7 years of warming, with the greatest increases in both foliar nitrogen content and relative growth rates. Our study suggests that considering species-specific responses to increases in nitrogen availability and changes in nitrogen form is important in predicting future forest composition and feedbacks to the climate system.
13. Microbial responses to carbon and nitrogen supplementation in an Antarctic dry valley soil
DEFF Research Database (Denmark)
Dennis, P. G.; Sparrow, A. D.; Gregorich, E. G.
2013-01-01
The soils of the McMurdo Dry Valleys are exposed to extremely dry and cold conditions. Nevertheless, they contain active biological communities that contribute to the biogeochemical processes. We have used ester-linked fatty acid (ELFA) analysis to investigate the effects of additions of carbon...... and nitrogen in glucose and ammonium chloride, respectively, on the soil microbial community in a field experiment lasting three years in the Garwood Valley. In the control treatment, the total ELFA concentration was small by comparison with temperate soils, but very large when expressed relative to the soil...... organic carbon concentration, indicating efficient conversion of soil organic carbon into microbial biomass and rapid turnover of soil organic carbon. The ELFA concentrations increased significantly in response to carbon additions, indicating that carbon supply was the main constraint to microbial...
14. Impact of understory vegetation on soil carbon and nitrogen dynamic in aerially seeded Pinus massoniana plantations
Science.gov (United States)
Pan, Ping; Zhao, Fang; Ning, Jinkui; Ouyang, Xunzhi; Zang, Hao
2018-01-01
Understory vegetation plays a vital role in regulating soil carbon (C) and nitrogen (N) characteristics due to differences in plant functional traits. Different understory vegetation types have been reported following aerial seeding. While aerial seeding is common in areas with serious soil erosion, few studies have been conducted to investigate changes in soil C and N cycling as affected by understory vegetation in aerially seeded plantations. Here, we studied soil C and N characteristics under two naturally formed understory vegetation types (Dicranopteris and graminoid) in aerially seeded Pinus massoniana Lamb plantations. Across the two studied understory vegetation types, soil organic C was significantly correlated with all measured soil N variables, including total N, available N, microbial biomass N and water-soluble organic N, while microbial biomass C was correlated with all measured variables except soil organic C. Dicranopteris and graminoid differed in their effects on soil C and N process. Except water-soluble organic C, all the other C and N variables were higher in soils with graminoids. The higher levels of soil organic C, microbial biomass C, total N, available N, microbial biomass N and water-soluble organic N were consistent with the higher litter and root quality (C/N) of graminoid vegetation compared to Dicranopteris. Changes in soil C and N cycles might be impacted by understory vegetation types via differences in litter or root quality. PMID:29377926
15. Applying Nitrogen Site-Specifically Using Soil Electrical Conductivity Maps and Precision Agriculture Technology
Directory of Open Access Journals (Sweden)
E.D. Lund
2001-01-01
Full Text Available Soil texture varies significantly within many agricultural fields. The physical properties of soil, such as soil texture, have a direct effect on water holding capacity, cation exchange capacity, crop yield, production capability, and nitrogen (N loss variations within a field. In short, mobile nutrients are used, lost, and stored differently as soil textures vary. A uniform application of N to varying soils results in a wide range of N availability to the crop. N applied in excess of crop usage results in a waste of the grower’s input expense, a potential negative effect on the environment, and in some crops a reduction of crop quality, yield, and harvestability. Inadequate N levels represent a lost opportunity for crop yield and profit. The global positioning system (GPS-referenced mapping of bulk soil electrical conductivity (EC has been shown to serve as an effective proxy for soil texture and other soil properties. Soils with a high clay content conduct more electricity than coarser textured soils, which results in higher EC values. This paper will describe the EC mapping process and provide case studies of site-specific N applications based on EC maps. Results of these case studies suggest that N can be managed site-specifically using a variety of management practices, including soil sampling, variable yield goals, and cropping history.
16. Responses of redwood soil microbial community structure and N transformations to climate change
Science.gov (United States)
Damon C. Bradbury; Mary K. Firestone
2012-01-01
Soil microorganisms perform critical ecosystem functions, including decomposition, nitrogen (N) mineralization and nitrification. Soil temperature and water availability can be critical determinants of the rates of these processes as well as microbial community composition and structure. This research examined how changes in climate affect bacterial and fungal...
17. Limitations and potential of spectral subtractions in fourier-transform infrared (FTIR) spectroscopy of soil samples
Science.gov (United States)
Soil science research is increasingly applying Fourier transform infrared (FTIR) spectroscopy for analysis of soil organic matter (SOM). However, the compositional complexity of soils and the dominance of the mineral component can limit spectroscopic resolution of SOM and other minor components. The...
18. Naturally occurring soil salinity does not reduce N-transforming enzymes or organisms
Science.gov (United States)
Soil salinity can negatively affect plant production and important biogeochemical cycles which are mainly carried out by soil microbes. The objective of this study was to contribute new information on soil biological N transformations by examining the impact primary salinity reduction has on a) the ...
19. Modelling soil nitrogen: The MAGIC model with nitrogen retention linked to carbon turnover using decomposer dynamics
Czech Academy of Sciences Publication Activity Database
Oulehle, F.; Cosby, B. J.; Wright, R. F.; Hruška, J.; Kopáček, Jiří; Krám, P.; Evans, C. D.; Moldan, F.
2012-01-01
Roč. 165, June (2012), s. 158-166 ISSN 0269-7491 Grant - others:FM EHS(CZ) CZ-0051 Institutional support: RVO:60077344 Keywords : nitrogen saturation * leaching * acidification * Norway spruce * Bohemian Forest * Slavkov Forest * Ore Mountains * Erzgebirge Subject RIV: DA - Hydrology ; Limnology Impact factor: 3.730, year: 2012
20. Decomposition rate of organic fertilizers: effect on yield, nitrogen availability and nitrogen stock in the soil
NARCIS (Netherlands)
Opheusden, van A.H.M.; Burgt, van der G.J.H.M.; Rietberg, P.I.
2012-01-01
The nitrogen of organic fertilizers does not fully mineralize within a season, and hence will partly become available in later years. This effect is taken into account for the first year but generally not in later fertilizer applications. If it would be taken into account, fertilizer use could be
1. Carbon input increases microbial nitrogen demand, but not microbial nitrogen mining in boreal forest soils
Science.gov (United States)
Wild, Birgit; Alaei, Saeed; Bengtson, Per; Bodé, Samuel; Boeckx, Pascal; Schnecker, Jörg; Mayerhofer, Werner; Rütting, Tobias
2016-04-01
Plant primary production at mid and high latitudes is often limited by low soil N availability. It has been hypothesized that plants can indirectly increase soil N availability via root exudation, i.e., via the release of easily degradable organic compounds such as sugars into the soil. These compounds can stimulate microbial activity and extracellular enzyme synthesis, and thus promote soil organic matter (SOM) decomposition ("priming effect"). Even more, increased C availability in the rhizosphere might specifically stimulate the synthesis of enzymes targeting N-rich polymers such as proteins that store most of the soil N, but are too large for immediate uptake ("N mining"). This effect might be particularly important in boreal forests, where plants often maintain high primary production in spite of low soil N availability. We here tested the hypothesis that increased C availability promotes protein depolymerization, and thus soil N availability. In a laboratory incubation experiment, we added 13C-labeled glucose to a range of soil samples derived from boreal forests across Sweden, and monitored the release of CO2 by C mineralization, distinguishing between CO2 from the added glucose and from the native, unlabeled soil organic C (SOC). Using a set of 15N pool dilution assays, we further measured gross rates of protein depolymerization (the breakdown of proteins into amino acids) and N mineralization (the microbial release of excess N as ammonium). Comparing unamended control samples, we found a high variability in C and N mineralization rates, even when normalized by SOC content. Both C and N mineralization were significantly correlated to SOM C/N ratios, with high C mineralization at high C/N and high N mineralization at low C/N, suggesting that microorganisms adjusted C and N mineralization rates to the C/N ratio of their substrate and released C or N that was in excess. The addition of glucose significantly stimulated the mineralization of native SOC in soils
2. Zinc oxide nanoparticles affect carbon and nitrogen mineralization of Phoenix dactylifera leaf litter in a sandy soil.
Science.gov (United States)
Rashid, Muhammad Imtiaz; Shahzad, Tanvir; Shahid, Muhammad; Ismail, Iqbal M I; Shah, Ghulam Mustafa; Almeelbi, Talal
2017-02-15
We investigated the impact of zinc oxide nanoparticles (ZnO NPs; 1000mgkg -1 soil) on soil microbes and their associated soil functions such as date palm (Phoenix dactylifera) leaf litter (5gkg -1 soil) carbon and nitrogen mineralization in mesocosms containing sandy soil. Nanoparticles application in litter-amended soil significantly decreased the cultivable heterotrophic bacterial and fungal colony forming units (cfu) compared to only litter-amended soil. The decrease in cfu could be related to lower microbial biomass carbon in nanoparticles-litter amended soil. Likewise, ZnO NPs also reduced CO 2 emission by 10% in aforementioned treatment but this was higher than control (soil only). Labile Zn was only detected in the microbial biomass of nanoparticles-litter applied soil indicating that microorganisms consumed this element from freely available nutrients in the soil. In this treatment, dissolved organic carbon and mineral nitrogen were 25 and 34% lower respectively compared to litter-amended soil. Such toxic effects of nanoparticles on litter decomposition resulted in 130 and 122% lower carbon and nitrogen mineralization efficiency respectively. Hence, our results entail that ZnO NPs are toxic to soil microbes and affect their function i.e., carbon and nitrogen mineralization of applied litter thus confirming their toxicity to microbial associated soil functions. Copyright © 2016 Elsevier B.V. All rights reserved.
3. Transformation and Deposition of Sulphur and Nitrogen Compounds in the Marine Boundary Layer
Energy Technology Data Exchange (ETDEWEB)
Hertel, O
1995-10-01
In this thesis the author performs a model study of the transformation and deposition of sulphur and nitrogen compounds in the marine boundary layer, including source-receptor relationships. The central part of the study is the development and testing of a variable scale trajectory model for Europe, with special emphasis on modelling the concentrations of gases and aerosols in the marine atmosphere and the deposition to sea. A one-dimensional version of the model was developed to model the chemical degradation of dimethyl sulphide (DMS) in the marine boundary layer. Although the model reproduces the observed levels of DMS and methane sulphonic acid (MSA) well, the calculated DMS concentration is not always in phase with observed levels, probably because of a local coastal emission that is correlated with the shifting tide. Another version of the trajectory model, Atmospheric Chemistry and Deposition model (ACDEP), was developed to study the deposition of nitrogen compounds to the Danish sea waters. This model uses a new numerical scheme, the Eulerian Backward Iterative method. The model is able to reproduce observations of air concentrations and wet deposition fairly well; data for dry deposition were not available. The model was also used for calculation of deposition of nitrogen compounds to the Kattegat. Finally, a sensitivity study was performed on the model. 175 refs., 87 figs., 32 tabs.
4. Effects of pH on nitrogen transformations in media-based aquaponics.
Science.gov (United States)
Zou, Yina; Hu, Zhen; Zhang, Jian; Xie, Huijun; Guimbaud, Christophe; Fang, Yingke
2016-06-01
To investigate the effects of pH on performance and nitrogen transformations in aquaponics, media-based aquaponics operated at pH 6.0, 7.5 and 9.0 were systematically examined and compared in this study. Results showed that nitrogen utilization efficiency (NUE) reached its maximum of 50.9% at pH 6.0, followed by 47.3% at pH 7.5 and 44.7% at pH 9.0. Concentrations of nitrogen compounds (i.e., TAN, NO2(-)-N and NO3(-)-N) in three pH systems were all under tolerable levels. pH had significant effect on N2O emission and N2O conversion ratio decreased from 2.0% to 0.6% when pH increased from 6.0 to 9.0, mainly because acid environment would inhibit denitrifiers and lead to higher N2O emission. 75.2-78.5% of N2O emission from aquaponics was attributed to denitrification. In general, aquaponics was suggested to maintain pH at 6.0 for high NUE, and further investigations on N2O mitigation strategy are needed. Copyright © 2016 Elsevier Ltd. All rights reserved.
5. Nitrogen dynamics in flooded soil systems: An overview on concepts and performance of models
NARCIS (Netherlands)
Khairudin, Nurul; Gaydon, Donald S.; Jing, Qi; Zakaria, Mohamad P.; Struik, Paul C.; Keesman, Karel J.
2018-01-01
Extensive modelling studies on nitrogen (N) dynamics in flooded soil systems have been published. Consequently, many N dynamics models are available for users to select from. With the current research trend, inclined towards multi-disciplinary research, and with substantial progress in understanding
6. Corn nitrogen management influences nitrous oxide emissions in drained and undrained soils
Science.gov (United States)
Tile-drainage and nitrogen (N) fertilization are important for corn (Zea mays L.) production. To date, no studies have evaluated nitrous oxide (N2O) emissions of single vs. split-N fertilizer application under different soil drainage conditions. The objective of this study was to quantify season-lon...
7. Integrating soil information into canopy sensor algorithms for improved corn nitrogen rate recommendation
Science.gov (United States)
Crop canopy sensors have proven effective at determining site-specific nitrogen (N) needs, but several Midwest states use different algorithms to predict site-specific N need. The objective of this research was to determine if soil information can be used to improve the Missouri canopy sensor algori...
8. Changes in microbial community characteristics and soil organic matter with nitrogen additions in two tropical forests
Science.gov (United States)
Daniela F. Cusack; Whendee L. Silver; Margaret S. Torn; Sarah D. Burton; Mary K. Firestone
2011-01-01
Microbial communities and their associated enzyme activities affect the amount and chemical quality of carbon (C) in soils. Increasing nitrogen (N) deposition, particularly in N-rich tropical forests, is likely to change the composition and behavior of microbial communities and feed back on ecosystem structure and function. This study presents a novel assessment of...
9. Towards improved nitrogen management in silage maize production on sandy soils
NARCIS (Netherlands)
Schroeder, J.
1998-01-01
Maize has become a highly appreciated crop in Dutch dairy farming during the last 25 years. The current cropping technique, however, is associated with a low recovery of soil mineral nitrogen (N) and serious losses of N to the environment. This gave rise to the research described in this
10. Soil properties and not inputs control carbon, nitrogen, phosphorus ratios in cropped soils in the long-term
Science.gov (United States)
Frossard, E.; Buchmann, N.; Bünemann, E. K.; Kiba, D. I.; Lompo, F.; Oberson, A.; Tamburini, F.; Traoré, O. Y. A.
2015-09-01
Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies explicitly considered the effects of agricultural management practices on soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long-term. Thus, we analysed the C, N and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK cropping system trial (Switzerland). In each of these trials, there was a large range of C, N and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at Wagga Wagga contains illite and haematite, is richer in clay and
11. Soil bacterial and fungal community responses to nitrogen addition across soil depth and microhabitat in an arid shrubland
Science.gov (United States)
Mueller, Rebecca C.; Belnap, Jayne; Kuske, Cheryl R.
2015-01-01
Arid shrublands are stressful environments, typified by alkaline soils low in organic matter, with biologically-limiting extremes in water availability, temperature, and UV radiation. The widely-spaced plants and interspace biological soil crusts in these regions provide soil nutrients in a localized fashion, creating a mosaic pattern of plant- or crust-associated microhabitats with distinct nutrient composition. With sporadic and limited rainfall, nutrients are primarily retained in the shallow surface soil, patterning biological activity. We examined soil bacterial and fungal community responses to simulated nitrogen (N) deposition in an arid Larrea tridentata-Ambrosia dumosa field experiment in southern Nevada, USA, using high-throughput sequencing of ribosomal RNA genes. To examine potential interactions among the N application, microhabitat and soil depth, we sampled soils associated with shrub canopies and interspace biological crusts at two soil depths (0–0.5 or 0–10 cm) across the N-amendment gradient (0, 7, and 15 kg ha−1 yr−1). We hypothesized that localized compositional differences in soil microbiota would constrain the impacts of N addition to a microhabitat distribution that would reflect highly localized geochemical conditions and microbial community composition. The richness and community composition of both bacterial and fungal communities differed significantly by microhabitat and with soil depth in each microhabitat. Only bacterial communities exhibited significant responses to the N addition. Community composition correlated with microhabitat and depth differences in soil geochemical features. Given the distinct roles of soil bacteria and fungi in major nutrient cycles, the resilience of fungi and sensitivity of bacteria to N amendments suggests that increased N input predicted for many arid ecosystems could shift nutrient cycling toward pathways driven primarily by fungal communities.
12. Soil bacterial and fungal community responses to nitrogen addition across soil depths and microhabitat in an arid shrubland
Directory of Open Access Journals (Sweden)
Rebecca C Mueller
2015-09-01
Full Text Available Arid shrublands are stressful environments, typified by alkaline soils low in organic matter, with biologically-limiting extremes in water availability, temperature and UV radiation. The widely-spaced plants and interspace biological soil crusts in these regions provide soil nutrients in a localized fashion, creating a mosaic pattern of plant- or crust-associated microhabitats with distinct nutrient composition. With sporadic and limited rainfall, nutrients are primarily retained in the shallow surface soil, patterning biological activity. We examined soil bacterial and fungal community responses to simulated nitrogen (N deposition in an arid Larrea tridentata-Ambrosia dumosa field experiment in southern Nevada, USA, using high-throughput sequencing of ribosomal RNA genes. To examine potential interactions among the N application, microhabitat and soil depth, we sampled soils associated with shrub canopies and interspace biological crusts at two soil depths (0-0.5 cm or 0-10 cm across the N-amendment gradient (0, 7 and 15 kg ha-1 yr-1. We hypothesized that localized compositional differences in soil microbiota would constrain the impacts of N addition to a microhabitat distribution that would reflect highly localized geochemical conditions and microbial community composition. The richness and community composition of both bacterial and fungal communities differed significantly by microhabitat and with soil depth in each microhabitat. Only bacterial communities exhibited significant responses to the N addition. Community composition correlated with microhabitat and depth differences in soil geochemical features. Given the distinct roles of soil bacteria and fungi in major nutrient cycles, the resilience of fungi and sensitivity of bacteria to N amendments suggests that increased N input predicted for many arid ecosystems could shift nutrient cycling toward pathways driven primarily by fungal communities.
13. Linking annual N2O emission in organic soils to mineral nitrogen input as estimated by heterotrophic respiration and soil C/N ratio.
Science.gov (United States)
Mu, Zhijian; Huang, Aiying; Ni, Jiupai; Xie, Deti
2014-01-01
Organic soils are an important source of N2O, but global estimates of these fluxes remain uncertain because measurements are sparse. We tested the hypothesis that N2O fluxes can be predicted from estimates of mineral nitrogen input, calculated from readily-available measurements of CO2 flux and soil C/N ratio. From studies of organic soils throughout the world, we compiled a data set of annual CO2 and N2O fluxes which were measured concurrently. The input of soil mineral nitrogen in these studies was estimated from applied fertilizer nitrogen and organic nitrogen mineralization. The latter was calculated by dividing the rate of soil heterotrophic respiration by soil C/N ratio. This index of mineral nitrogen input explained up to 69% of the overall variability of N2O fluxes, whereas CO2 flux or soil C/N ratio alone explained only 49% and 36% of the variability, respectively. Including water table level in the model, along with mineral nitrogen input, further improved the model with the explanatory proportion of variability in N2O flux increasing to 75%. Unlike grassland or cropland soils, forest soils were evidently nitrogen-limited, so water table level had no significant effect on N2O flux. Our proposed approach, which uses the product of soil-derived CO2 flux and the inverse of soil C/N ratio as a proxy for nitrogen mineralization, shows promise for estimating regional or global N2O fluxes from organic soils, although some further enhancements may be warranted.
14. A Simple and Rapid Method to Evaluate Potentially Mineralizable Nitrogen in Sewage Sludge Amended Calcareous Soils
Directory of Open Access Journals (Sweden)
Yazdan Lotfi
2005-06-01
Full Text Available Potentially mineralizable nitrogen (PMN can be usually considered as labile nitrogen. Measurement of PMN is expensive and time consuming; therefore, a simpler and more rapid alternative may facilitate routine laboratory analysis. The objective of this study was to determine the relationship between PMN and biological index of nitrogen availability (BINA. The studied soil was previously treated with 0, 25, and 100 tons ha-1 of sewage sludge with 0, 1, 2 and 3 consecutive years of application. Soil samples were taken 6 months after the latest application. PMN was measured according to Stanford and Smith procedure (20 weeks of aerobic incubation with 2 weeks leaching intervals and BINA measured as described by Bundy and Meisinger (7 days of anaerobic incubation at 40˚ C followed by extraction of NH4+. Results showed that PMN was significantly correlated with BINA (r = 0.938, P
15. Influence of soil moisture on uptake and utilization of applied nitrogen in tea
International Nuclear Information System (INIS)
Marimuthu, S.; Raj Kumar, R.
1999-01-01
An experiment was conducted with pot-grown young tea plants to study N uptake under different soil moisture regime. Labelled urea nitrogen was found effectively utilized under rainfed conditions. However, N loss through percolation/leaching in response to saturated moisture was as high as 33.3%. Plants grown under controlled conditions utilized less amount of applied N and the rest was retained in the soil. Unaccounted loss, in both the cases, was approximately 9%. Fertilizer-use efficiency of young tea plants under rain fed conditions was about 35% while it was 15% under moisture deficient conditions. Results on N balance in tea soils are discussed. (author)
16. Biological soil crusts emit large amounts of NO and HONO affecting the nitrogen cycle in drylands
Science.gov (United States)
Tamm, Alexandra; Wu, Dianming; Ruckteschler, Nina; Rodríguez-Caballero, Emilio; Steinkamp, Jörg; Meusel, Hannah; Elbert, Wolfgang; Behrendt, Thomas; Sörgel, Matthias; Cheng, Yafang; Crutzen, Paul J.; Su, Hang; Pöschl, Ulrich; Weber, Bettina
2016-04-01
Dryland systems currently cover ˜40% of the world's land surface and are still expanding as a consequence of human impact and global change. In contrast to that, information on their role in global biochemical processes is limited, probably induced by the presumption that their sparse vegetation cover plays a negligible role in global balances. However, spaces between the sparse shrubs are not bare, but soils are mostly covered by biological soil crusts (biocrusts). These biocrust communities belong to the oldest life forms, resulting from an assembly between soil particles and cyanobacteria, lichens, bryophytes, and algae plus heterotrophic organisms in varying proportions. Depending on the dominating organism group, cyanobacteria-, lichen-, and bryophyte-dominated biocrusts are distinguished. Besides their ability to restrict soil erosion they fix atmospheric carbon and nitrogen, and by doing this they serve as a nutrient source in strongly depleted dryland ecosystems. In this study we show that a fraction of the nitrogen fixed by biocrusts is metabolized and subsequently returned to the atmosphere in the form of nitric oxide (NO) and nitrous acid (HONO). These gases affect the radical formation and oxidizing capacity within the troposphere, thus being of particular interest to atmospheric chemistry. Laboratory measurements using dynamic chamber systems showed that dark cyanobacteria-dominated crusts emitted the largest amounts of NO and HONO, being ˜20 times higher than trace gas fluxes of nearby bare soil. We showed that these nitrogen emissions have a biogenic origin, as emissions of formerly strongly emitting samples almost completely ceased after sterilization. By combining laboratory, field, and satellite measurement data we made a best estimate of global annual emissions amounting to ˜1.1 Tg of NO-N and ˜0.6 Tg of HONO-N from biocrusts. This sum of 1.7 Tg of reactive nitrogen emissions equals ˜20% of the soil release under natural vegetation according
17. A study on the migration and transformation law of nitrogen in urine in municipal wastewater transportation and treatment.
Science.gov (United States)
Wuang, Ren; Pengkang, Jin; Chenggang, Liang; Xiaochang, Wang; Lei, Zhang
2013-01-01
Many studies suggest that the total nitrogen (TN) in urine is around 9,000 mg/L and about 80% of nitrogen in municipal wastewater comes from urine, because nitrogen mainly occurs in the form of urea in fresh human urine. Based on this fact, the study on the migration and transformation law of nitrogen in urine and its influencing factors was carried out. It can be seen from the experimental results that the transformation rate of urea in urine into ammonia nitrogen after standing for 20 days is only about 18.2%, but the urea in urine can be hydrolyzed into ammonia nitrogen rapidly after it is catalyzed directly with free urease or indirectly with microorganism. Adding respectively a certain amount of urease, activated sludge and septic-tank sludge to urine samples can make the maximum transformation rate achieve 85% after 1 day, 2 days and 6 days, respectively. In combination with some corresponding treatment methods, recycling of nitrogen in urine can be achieved. The results are of great significance in guiding denitrification in municipal wastewater treatment.
18. Sources and transformations of anthropogenic nitrogen along an urban river–estuarine continuum
Directory of Open Access Journals (Sweden)
M. J. Pennino
2016-11-01
Full Text Available Urbanization has altered the fate and transport of anthropogenic nitrogen (N in rivers and estuaries globally. This study evaluates the capacity of an urbanizing river–estuarine continuum to transform N inputs from the world's largest advanced (e.g., phosphorus and biological N removal wastewater treatment facility. Effluent samples and surface water were collected monthly along the Potomac River estuary from Washington D.C. to the Chesapeake Bay over a distance of 150 km. In conjunction with box model mass balances, nitrate stable isotopes and mixing models were used to trace the fate of urban wastewater nitrate. Nitrate concentrations and δ15N-NO3− values were higher down-estuary from the Blue Plains wastewater outfall in Washington D.C. (2.25 ± 0.62 mg L−1 and 25.7 ± 2.9 ‰, respectively compared to upper-estuary concentrations (1.0 ± 0.2 mg L−1 and 9.3 ± 1.4 ‰, respectively. Nitrate concentration then decreased rapidly within 30 km down-estuary (to 0.8 ± 0.2 mg L−1, corresponding to an increase in organic nitrogen and dissolved organic carbon, suggesting biotic uptake and organic transformation. TN loads declined down-estuary (from an annual average of 48 000 ± 5000 kg day−1 at the sewage treatment plant outfall to 23 000 ± 13 000 kg day−1 at the estuary mouth, with the greatest percentage decrease during summer and fall. Annually, there was a 70 ± 31 % loss in wastewater NO3− along the estuary, and 28 ± 6 % of urban wastewater TN inputs were exported to the Chesapeake Bay, with the greatest contribution of wastewater TN loads during the spring. Our results suggest that biological transformations along the urban river–estuary continuum can significantly transform wastewater N inputs from major cities globally, and more work is necessary to evaluate the potential of organic nitrogen and carbon to contribute to eutrophication and hypoxia.
19. Invasive Andropogon gayanus (gamba grass) is an ecosystem transformer of nitrogen relations in Australian savanna.
Science.gov (United States)
Rossiter-Rachor, N A; Setterfield, S A; Douglas, M M; Hutley, L B; Cook, G D; Schmidt, S
2009-09-01
Invasion by the African grass Andropogon gayanus is drastically altering the understory structure of oligotrophic savannas in tropical Australia. We compared nitrogen (N) relations and phenology of A. gayanus and native grasses to examine the impact of invasion on N cycling and to determine possible reasons for invasiveness of A. gayanus. Andropogon gayanus produced up to 10 and four times more shoot phytomass and root biomass, with up to seven and 2.5 times greater shoot and root N pools than native grass understory. These pronounced differences in phytomass and N pools between A. gayanus and native grasses were associated with an altered N cycle. Most growth occurs in the wet season when, compared with native grasses, dominance of A. gayanus was associated with significantly lower total soil N pools, lower nitrification rates, up to three times lower soil nitrate availability, and up to three times higher soil ammonium availability. Uptake kinetics for different N sources were studied with excised roots of three grass species ex situ. Excised roots of A. gayanus had an over six times higher-uptake rate of ammonium than roots of native grasses, while native grass Eriachne triseta had a three times higher uptake rate of nitrate than A. gayanus. We hypothesize that A. gayanus stimulates ammonification but inhibits nitrification, as was shown to occur in its native range in Africa, and that this modification of the soil N cycle is linked to the species' preference for ammonium as an N source. This mechanism could result in altered soil N relations and could enhance the competitive superiority and persistence of A. gayanus in Australian savannas.
20. Nitrogen management of switchgrass and miscanthus on marginal soils
Science.gov (United States)
Miscanthus × giganteus and switchgrass yield and fertilizer N requirements have been well studied in Europe and parts of the United States, but few reports have investigated their production on eroded claypan soils economically marginal for grain crops. This study was conducted to evaluate yield pot...
1. Seasonal Soil Nitrogen Mineralization within an Integrated Crop and Livestock System in Western North Dakota, USA
Science.gov (United States)
Landblom, Douglas; Senturklu, Songul; Cihacek, Larry; Pfenning, Lauren; Brevik, Eric C.
2015-04-01
Protecting natural resources while maintaining or maximizing crop yield potential is of utmost importance for sustainable crop and livestock production systems. Since soil organic matter and its decomposition by soil organisms is at the very foundation of healthy productive soils, systems research at the North Dakota State University Dickinson Research Extension Center is evaluating seasonal soil nitrogen fertility within an integrated crop and livestock production system. The 5-year diverse crop rotation is: sunflower (SF) - hard red spring wheat (HRSW) - fall seeded winter triticale-hairy vetch (THV; spring harvested for hay)/spring seeded 7-species cover crop (CC) - Corn (C) (85-90 day var.) - field pea-barley intercrop (PBY). The HRSW and SF are harvested as cash crops and the PBY, C, and CC are harvested by grazing cattle. In the system, yearling beef steers graze the PBY and C before feedlot entry and after weaning, gestating beef cows graze the CC. Since rotation establishment, four crop years have been harvested from the crop rotation. All crops have been seeded using a JD 1590 no-till drill except C and SF. Corn and SF were planted using a JD 7000 no-till planter. The HRSW, PBY, and CC were seeded at a soil depth of 3.8 cm and a row width of 19.1 cm. Seed placement for the C and SF crops was at a soil depth of 5.1 cm and the row spacing was 0.762 m. The plant population goal/ha for C, SF, and wheat was 7,689, 50,587, and 7,244 p/ha, respectively. During the 3rd cropping year, soil bulk density was measured and during the 4th cropping year, seasonal nitrogen fertility was monitored throughout the growing season from June to October. Seasonal nitrate nitrogen (NO3-N), ammonium nitrogen (NH4-N), total season mineral nitrogen (NO3-N + NH4-N), cropping system NO3-N, and bulk density were measured in 3 replicated non-fertilized field plot areas within each 10.6 ha triple replicated crop fields. Within each plot area, 6 - 20.3 cm x 0.61 m aluminum irrigation
2. Nitrogen transformation under different dissolved oxygen levels by the anoxygenic phototrophic bacterium Marichromatium gracile.
Science.gov (United States)
Hong, Xuan; Chen, Zhongwei; Zhao, Chungui; Yang, Suping
2017-06-01
Marichromatium gracile: YL28 (M. gracile YL28) is an anoxygenic phototrophic bacterial strain that utilizes ammonia, nitrate, or nitrite as its sole nitrogen source during growth. In this study, we investigated the removal and transformation of ammonium, nitrate, and nitrite by M. gracile YL28 grown in a combinatorial culture system of sodium acetate-ammonium, sodium acetate-nitrate and sodium acetate-nitrite in response to different initial dissolved oxygen (DO) levels. In the sodium acetate-ammonium system under aerobic conditions (initial DO = 7.20-7.25 mg/L), we detected a continuous accumulation of nitrate and nitrite. However, under semi-anaerobic conditions (initial DO = 4.08-4.26 mg/L), we observed a temporary accumulation of nitrate and nitrite. Interestingly, under anaerobic conditions (initial DO = 0.36-0.67 mg/L), there was little accumulation of nitrate and nitrite, but an increase in nitrous oxide production. In the sodium acetate-nitrite system, nitrite levels declined slightly under aerobic conditions, and nitrite was completely removed under semi-anaerobic and anaerobic conditions. In addition, M. gracile YL28 was able to grow using nitrite as the sole nitrogen source in situations when nitrogen gas produced by denitrification was eliminated. Taken together, the data indicate that M. gracile YL28 performs simultaneous heterotrophic nitrification and denitrification at low-DO levels and uses nitrite as the sole nitrogen source for growth. Our study is the first to demonstrate that anoxygenic phototrophic bacteria perform heterotrophic ammonia-oxidization and denitrification under anaerobic conditions.
3. [Effects of simulated nitrogen deposition on soil microbial biomass carbon and nitrogen in natural evergreen broad-leaved forest in the Rainy Area of West China].
Science.gov (United States)
Zhou, Shi Xing; Zou, Cheng; Xiao, Yong Xiang; Xiang, Yuan Bin; Han, Bo Han; Tang, Jian Dong; Luo, Chao; Huang, Cong de
2017-01-01
To understand the effects of increasing nitrogen deposition on soil microbial biomass carbon (MBC) and nitrogen(MBN), an in situ experiment was conducted in a natural evergreen broad-leaved forest in Ya'an City, Sichuan Province. Four levels of nitrogen deposition were set: i.e., control (CK, 0 g N·m -2 ·a -1 ), low nitrogen (L, 5 g N·m -2 ·a -1 ), medium nitrogen (M, 15 g N·m -2 ·a -1 ), and high nitrogen (H, 30 g N·m -2 ·a -1 ). The results indicated that nitrogen deposition significantly decreased MBC and MBN in the 0-10 cm soil layer, and as N de-position increased, the inhibition effect was enhanced. L and M treatments had no significant effect on MBC and MBN in the 10-20 cm soil layer, while H treatment significantly reduced. The influence of N deposition on MBC and MBN was weakened with the increase of soil depth. MBC and MBN had obvious seasonal dynamic, which were highest in autumn and lowest in summer both in the 0-10 and 10-20 cm soil layers. The fluctuation ranges of soil microbial biomass C/N were respectively 10.58-11.19 and 9.62-12.20 in the 0-10 cm and 10-20 cm soil layers, which indicated that the fungi hold advantage in the soil microbial community in this natural evergreen broad-leaved forest.
4. Exogenous nutrients and carbon resource change the responses of soil organic matter decomposition and nitrogen immobilization to nitrogen deposition
Science.gov (United States)
He, Ping; Wan, Song-Ze; Fang, Xiang-Min; Wang, Fang-Chao; Chen, Fu-Sheng
2016-01-01
It is unclear whether exogenous nutrients and carbon (C) additions alter substrate immobilization to deposited nitrogen (N) during decomposition. In this study, we used laboratory microcosm experiments and 15N isotope tracer techniques with five different treatments including N addition, N+non-N nutrients addition, N+C addition, N+non-N nutrients+C addition and control, to investigate the coupling effects of non-N nutrients, C addition and N deposition on forest floor decomposition in subtropical China. The results indicated that N deposition inhibited soil organic matter and litter decomposition by 66% and 38%, respectively. Soil immobilized 15N following N addition was lowest among treatments. Litter 15N immobilized following N addition was significantly higher and lower than that of combined treatments during the early and late decomposition stage, respectively. Both soil and litter extractable mineral N were lower in combined treatments than in N addition treatment. Since soil N immobilization and litter N release were respectively enhanced and inhibited with elevated non-N nutrient and C resources, it can be speculated that the N leaching due to N deposition decreases with increasing nutrient and C resources. This study should advance our understanding of how forests responds the elevated N deposition. PMID:27020048
5. BIOCHAR AS SOIL CONDITIONER IN THE SUCCESSION OF UPLAND RICE AND COWPEA FERTILIZED WITH NITROGEN
Directory of Open Access Journals (Sweden)
NEYTON DE OLIVEIRA MIRANDA
2017-01-01
Full Text Available The effects of biochar and nitrogen application on yields of upland rice and cowpea and on soil fertility were determined in a greenhouse in Macaíba, RN, Brazil. The trial consisted of the succession of two crops in a completely randomized design and a factorial scheme, with four replicates. Initially, four doses of biochar and four doses of nitrogen were tested for cultivation of rice. Subsequently, four doses of biochar and two doses of nitrogen were tested in half of the pots maintained for planting cowpea. Soil was sampled after rice harvest for half of the pots and at end of the trial for the remaining pots. We evaluated the following parameters: mass of hundred grains of rice, dry shoot mass, panicle number, number of filled spikelets and of empty spikelets, and grain production. Determinations for cowpea were: pod number per pot, grain number per pod, and grain production per pot. Measured soil parameters were: pH, contents of organic carbon, P, K, Ca, Mg, Na, cation exchange capacity, and exchangeable sodium percentage. Biochar addition did not influence yield components of upland rice and cowpea, but resulted in increased soil N retention, which influenced rice dry shoot mass, spikelets sterility, panicle number, and grain mass. Biochar also promoted increased soil pH, potassium content, and exchangeable sodium percentage and decreased calcium and magnesium concentrations.
6. Nitrogen isotope ratios in surface and sub-surface soil horizons
International Nuclear Information System (INIS)
Rennie, D.A.; Paul, E.A.
1975-01-01
Nitrogen isotope analysis of surface soils and soil-derived nitrate for selected chernozemic and luvisolic soils showed mean delta 15 N values of 11.7 and 11.3, respectively. Isotope enrichment of the total N reached a maximum in the lower B horizon. Sub-soil parent material samples from the one deep profile included in the study indicated a delta 15 N value (NO 3 -N) of 1/3 that of the Ap horizon, at a depth of 180 cm. The delta 15 N of sub-surface soil horizons containing residual fertilizer N were low (-2.2) compared to the surface horizon (9.9). The data reported from this preliminary survey suggest that the natural variations in 15 N abundance between different soils and horizons of the same soil reflect the cumulative effects of soil genesis and soil management. More detailed knowledge and understanding of biological and other processes which control N isotope concentrations in these soils must be obtained before the data reported can be interpreted. (author)
7. Effect of nitrogen sources on the biodegradation of diesel fuel in unsaturated soil
International Nuclear Information System (INIS)
Brook, T. R.; Stiver, W. H.; Zytner, R. G.
1997-01-01
The various factors involved in controlling the rate and efficiency of the bioremediation process were studied, among them the type and concentration of contaminants, temperature, oxygen content and nutrient status. This study emphasized the effect of the nitrogen source on the degradation rate of diesel fuel in nutrient-limited soil. Various nitrogen sources were studied, including ammonium nitrate, urea, and urea oligomers. Treatment with urea produced the highest rate of hydrocarbon degradation, but ammonium levels were a better indicator of nutrient performance than total inorganic nitrogen. Other nitrogen sources produced little or no effect on the rate of biodegradation; there was no evidence that nitrate at 0.5 mg N/g concentration was inhibitory. 11 refs., 6 figs
8. Nitrogen
Science.gov (United States)
Apodaca, Lori E.
2013-01-01
The article presents an overview of the nitrogen chemical market as of July 2013, including the production of ammonia compounds. Industrial uses for ammonia include fertilizers, explosives, and plastics. Other topics include industrial capacity of U.S. ammonia producers CF Industries Holdings Inc., Koch Nitrogen Co., PCS Nitrogen, Inc., and Agrium Inc., the impact of natural gas prices on the nitrogen industry, and demand for corn crops for ethanol production.
9. A global analysis of soil microbial biomass carbon, nitrogen and phosphorus in terrestrial ecosystems
Energy Technology Data Exchange (ETDEWEB)
Xu, Xiaofeng [ORNL; Thornton, Peter E [ORNL; Post, Wilfred M [ORNL
2013-01-01
Soil microbes play a pivotal role in regulating land-atmosphere interactions; the soil microbial biomass carbon (C), nitrogen (N), phosphorus (P) and C:N:P stoichiometry are important regulators for soil biogeochemical processes; however, the current knowledge on magnitude, stoichiometry, storage, and spatial distribution of global soil microbial biomass C, N, and P is limited. In this study, 3087 pairs of data points were retrieved from 281 published papers and further used to summarize the magnitudes and stoichiometries of C, N, and P in soils and soil microbial biomass at global- and biome-levels. Finally, global stock and spatial distribution of microbial biomass C and N in 0-30 cm and 0-100 cm soil profiles were estimated. The results show that C, N, and P in soils and soil microbial biomass vary substantially across biomes; the fractions of soil nutrient C, N, and P in soil microbial biomass are 1.6% in a 95% confidence interval of (1.5%-1.6%), 2.9% in a 95% confidence interval of (2.8%-3.0%), and 4.4% in a 95% confidence interval of (3.9%-5.0%), respectively. The best estimates of C:N:P stoichiometries for soil nutrients and soil microbial biomass are 153:11:1, and 47:6:1, respectively, at global scale, and they vary in a wide range among biomes. Vertical distribution of soil microbial biomass follows the distribution of roots up to 1 m depth. The global stock of soil microbial biomass C and N were estimated to be 15.2 Pg C and 2.3 Pg N in the 0-30 cm soil profiles, and 21.2 Pg C and 3.2 Pg N in the 0-100 cm soil profiles. We did not estimate P in soil microbial biomass due to data shortage and insignificant correlation with soil total P and climate variables. The spatial patterns of soil microbial biomass C and N were consistent with those of soil organic C and total N, i.e. high density in northern high latitude, and low density in low latitudes and southern hemisphere.
10. Spatial variability of nitrogen-15 and its relation to the variability of other soil properties
International Nuclear Information System (INIS)
Selles, F.; Karamanos, R.E.; Kachanoski, R.G.
1986-01-01
The spatial variability of natural 15 N abundance of a cultivated Chernozemic soil and its native prairie counterpart were smaller than that of total N, organic C, and the C/N ratio. Further, the number of samples required to estimate the true mean of total N with a given precision at various probability levels were twofold those required to estimate the true mean of total N with a given precision at various probability levels were twofold those required to determine the mean 15 N abundance of total soil N in the surface horizons may reflect the isotopic composition of the nitrogenous substances entering the soil system or changes in the isotopic composition of soil N due to humification processes, probably induced by variations in topographic and microrelief features of the soil
11. Soil respiration, microbial biomass and exoenzyme activity in switchgrass stands under nitrogen fertilization management and climate warming.
Science.gov (United States)
Jian, S.; Li, J.; de Koff, J.; Celada, S.; Mayes, M. A.; Wang, G.; Guo, C.
2016-12-01
Switchgrass (Panicum virgatum L.), as a model bioenergy crop, received nitrogen fertilizers for increasing its biomass yields. Studies rarely investigate the interactive effects of nitrogen fertilization and climate warming on soil microbial activity and carbon cycling in switchgrass cropping systems. Enhanced nitrogen availability under fertilization can alter rates of soil organic matter decomposition and soil carbon emissions to the atmosphere and thus have an effect on climate change. Here, we assess soil CO2 emission, microbial biomass and exoenzyme activities in two switchgrass stands with no fertilizer and 60 lbs N / acre. Soils were incubated at 15 ºC and 20 ºC for 180-day. Dry switchgrass plant materials were added to incubation jars and the 13C stable isotopic probing technique was used to monitor soil CO2 respiration derived from relatively labile litter and indigenous soil. Measurements of respiration, δ13C of respiration, microbial biomass carbon and exoenzyme activity were performed on days 1, 5, 10, 15, 30, 60, 90, 120, 150 and 180. Soil respiration rate was greater in the samples incubated at 20 ºC as compared to those incubated at 15 ºC. Exoenzyme activities were significantly altered by warming, litter addition and nitrogen fertilization. There was a significant interactive effect of nitrogen fertilization and warming on the proportion of CO2 respired from soils such that nitrogen fertilization enhanced warming-induced increase by 12.0% (Pmineralization. Fertilization increased soil microbial biomass carbon at both temperatures (9.0% at 15 ºC and 14.5% at 20 ºC). Our preliminary analysis suggested that warming effects on enhanced soil respiration can be further increased with elevated fertilizer input via greater microbial biomass and exoenzyme activity. In addition to greater biomass yield under N fertilization, this study informs potential soil carbon loss from stimulated soil respiration under nitrogen fertilization and warming in
12. Effects of poly-γ-glutamic acid biopreparation (PGAB) on nitrogen conservation in the coastal saline soil
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Chen, Lihua; Xu, Xianghong; Zhang, Huan; Han, Rui; Cheng, Yao; Tan, Xueyi; Chen, Xuanyu
2017-04-01
Water leaching is the major method to decrease soil salinity of the coastal saline soil. Conservation of soil nutrition in the soil ameliorating process is helpful to maintain soil fertility and prevent environment pollution. In the experiment, glutamic acid and poly-γ-glutamic acid (PGA) producing bacteria were isolated for manufacturing the PGA biopreparation (PGAB), and the effect of PGAB on the soil nitrogen (N) conservation was assayed. The glutamic acid and PGA producing bacteria were identified as Brevibacterium flavum and Bacillus amyloliquefaciens. After soil leached with water for 90 days, compared to control treatment, salt concentration of 0-30cm soil with PGAB treatment was lowered by 39.93%, however the total N loss was decreased by 65.37%. Compared to control, the microbial biomass N increased by 1.19 times at 0-30 cm soil with PGAB treatment. The populations of soil total bacteria, fungi, actinomyces, nitrogen fixing bacteria, ammonifying bacteria, nitrifying bacteria and denitrifying bacteria and biomass of soil algae were significantly increased in PGAB treatment, while anaerobic bacteria decreased (P 0.25 mm and 0.02 mm < diameter <0.25 mm were increased by 2.93 times and 26.79% respectively in PGAB treatment. The soil erosion-resistance coefficient of PGAB treatment increased by 50%. All these suggested that the PGAB conserved the soil nitrogen effectively in the process of soil water leaching and improved the coastal saline soil quality.
13. Complexities of Nitrogen Isotope Biogeochemistry in Plant-Soil Systems: Implications for the Study of Ancient Agricultural and Animal Management Practices
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Paul eSzpak
2014-06-01
Full Text Available Nitrogen isotopic studies have potential to shed light on the structure of ancient ecosystems, agropastoral regimes, and human-environment interactions. Until relatively recently, however, little attention was paid to the complexities of nitrogen transformations in ancient plant-soil systems and their potential impact on plant and animal tissue nitrogen isotopic compositions. This paper discusses the importance of understanding nitrogen dynamics in ancient contexts, and highlights several key areas of archaeology where a more detailed understanding of these processes may enable us to answer some fundamental questions. This paper explores two larger themes that are prominent in archaeological studies using stable nitrogen isotope analysis: (1 agricultural practices (use of animal fertilizers, burning of vegetation or shifting cultivation, and tillage and (2 animal domestication and husbandry (grazing intensity/stocking rate and the foddering of domestic animals with cultigens. The paucity of plant material in ancient deposits necessitates that these issues are addressed primarily through the isotopic analysis of skeletal material rather than the plants themselves, but the interpretation of these data hinges on a thorough understanding of the underlying biogeochemical processes in plant-soil systems. Building on studies conducted in modern ecosystems and under controlled conditions, these processes are reviewed, and their relevance discussed for ancient contexts.
14. Nitrogen-rich higher-molecular soil organic compounds patterned by lignin degradation products: Considerations on the nature of soil organic nitrogen
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Liebner, Falk; Bertoli, Luca; Pour, Georg; Klinger, Karl; Ragab, Tamer; Rosenau, Thomas
2016-04-01
The pathways leading to accumulation of covalently bonded nitrogen in higher-molecular soil organic matter (SOM) are still a controversial issue in soil science and geochemistry. Similarly, structural elucidation of the variety of the types of nitrogenous moieties present in SOM is still in its infancy even though recent NMR studies suggest amide-type nitrogen to form the majority of organically bonded nitrogen which is, however, frequently not in accordance with the results of wet-chemical analyses. Following the modified polyphenol theory of Flaig and Kononova but fully aware of the imperfection of a semi-abiotic simulation approach, this work communicates the results of a study that investigated some potential nitrogen accumulation pathways occurring in the re-condensation branch of the theory following the reactions between well-known low-molecular lignin and carbohydrate degradation products with nitrogenous nucleophiles occurring in soils under aerobic conditions. Different low-molecular degradation products of lignin, cellulose, and hemicellulose, such as hydroquinone, methoxyhydroquinone, p-benzoquinone, 2,5-dihydroxy-[1,4]benzoquinone, glucose, xylose, and the respective polysaccharides, i.e. cellulose, xylan as well as various types of lignin were subjected to a joint treatment with oxygen and low-molecular N-nucleophiles, such as ammonia, amines, and amino acids in aqueous conditions, partly using respective 15N labeled compounds for further 15N CPMAS NMR studies. Product mixtures derived from mono- and polysaccharides have been comprehensively fractionated and analyzed by GC/MS after derivatization. Some of ammoxidized polyphenols and quinones have been analyzed by X-ray photoelectron spectroscopy. Some products, such as those obtained from ammoxidation of methoxy hydroquinone using 15N labeled ammonia were fractionated following the IHSS protocol. Individual humin (H), humic acid (HA), and fulvic acid (FA) fractions were subjected to elemental analyses
15. Cover crop and nitrogen fertilization influence soil carbon and nitrogen under bioenergy sweet sorghum
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Cover crop and N fertilization may maintain soil C and N levels under sweet sorghum (Sorghum bicolor [L.] Moench) biomass harvested for bioenergy production. The effect of cover crops (hairy vetch [Vicia villosa Roth], rye [Secaele cereale L.], hairy vetch/rye mixture, and the control [no cover crop...
16. Effect of nitrification inhibitors on the content of available nitrogen forms in the soil under maize (Zea mays, L. growing
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Zuzana PANAKOVA
2016-12-01
Full Text Available The objective of this research was to investigate the effect of nitrification inhibitors (dicyandiamide and 1,2,4 triazole on the content of nitrate and ammonium nitrogen in the soil and the effectiveness of nitrogen-sulphur nutrition of maize. The research was conducted in field small-plot experiment with maize on Haplic Luvisol with dominance of clay fraction in experimental years 2012 to 2015. The dose of nitrogen in all experimental treatments was 160 kg*ha-1 and was applied at one shot or split in three partial doses. Soil samples from all examined treatments were taken from three soil depths (0.0-0.3 m, 0.3-0.6 m and 0.6-0.9 m, respectively by probe rod in 4-5 week intervals. Achieved results indicate that on the average of four years and three depths of the soil profile, application of nitrification inhibitors contained in fertilizer ENSIN considerably reduced portion of nitrate nitrogen from the content of mineral nitrogen in the soil by 7-32 relative %. The application of fertilizer ENSIN considerably increased content of ammonium nitrogen in the soil by 10-59 relative %. A favourable effect on increase of ammonium nitrogen content and reduction of nitrate nitrogen content was found out in spite of the fact that in this treatment the total dose of fertilizer was applied at one shot.
17. Increased nitrogen leaching following soil freezing is due to decreased root uptake in a northern hardwood forest
Science.gov (United States)
John L. Campbell; Anne M. Socci; Pamela H. Templer
2014-01-01
The depth and duration of snow pack is declining in the northeastern United States as a result of warming air temperatures. Since snow insulates soil, a decreased snow pack can increase the frequency of soil freezing, which has been shown to have important biogeochemical implications. One of the most notable effects of soil freezing is increased inorganic nitrogen...
18. Soil Nitrogen Storage, Distribution, and Associated Controlling Factors in the Northeast Tibetan Plateau Shrublands
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Xiuqing Nie
2017-11-01
Full Text Available Although the soils in the Tibetan Plateau shrublands store large amounts of total nitrogen (N, the estimated values remain uncertain because of spatial heterogeneity and a lack of field observations. In this study, we quantified the regional soil N storage, spatial and vertical density distributions, and related climatic controls using 183 soil profiles sampled from 61 sites across the Northeast Tibetan Plateau shrublands during the period of 2011–2013. Our analysis revealed a soil N storage value of 132.40 Tg at a depth of 100 cm, with an average density of 1.21 kg m−2. Soil N density was distributed at greater levels in alpine shrublands, compared with desert shrublands. Spatially, soil N densities decreased from south to north and from east to west, and, vertically, the soil N in the upper 30 and 50 cm accounted for 42% and 64% of the total soil N stocks in the Tibetan Plateau. However, compared with desert shrublands, the surface layers in alpine shrublands exhibited a larger distribution of soil N stocks. Overall, the soil N density in the top 30 cm increased significantly with the mean annual precipitation (MAP and tended to decrease with the mean annual temperature (MAT, although the dominant climatic controls differed among shrubland types. Specifically, MAP in alpine shrublands, and MAT in desert shrubland, had a weak effect on N density. Soil pH can significant affect soil N density in the Tibetan Plateau shrublands. In conclusion, changes in soil N density should be monitored over the long term to provide accurate information about the effects of climatic factors.
19. Novel European free-living, non-diazotrophic Bradyrhizobium isolates from contrasting soils that lack nodulation and nitrogen fixation genes - a genome comparison
Science.gov (United States)
Jones, Frances Patricia; Clark, Ian M.; King, Robert; Shaw, Liz J.; Woodward, Martin J.; Hirsch, Penny R.
2016-05-01
The slow-growing genus Bradyrhizobium is biologically important in soils, with different representatives found to perform a range of biochemical functions including photosynthesis, induction of root nodules and symbiotic nitrogen fixation and denitrification. Consequently, the role of the genus in soil ecology and biogeochemical transformations is of agricultural and environmental significance. Some isolates of Bradyrhizobium have been shown to be non-symbiotic and do not possess the ability to form nodules. Here we present the genome and gene annotations of two such free-living Bradyrhizobium isolates, named G22 and BF49, from soils with differing long-term management regimes (grassland and bare fallow respectively) in addition to carbon metabolism analysis. These Bradyrhizobium isolates are the first to be isolated and sequenced from European soil and are the first free-living Bradyrhizobium isolates, lacking both nodulation and nitrogen fixation genes, to have their genomes sequenced and assembled from cultured samples. The G22 and BF49 genomes are distinctly different with respect to size and number of genes; the grassland isolate also contains a plasmid. There are also a number of functional differences between these isolates and other published genomes, suggesting that this ubiquitous genus is extremely heterogeneous and has roles within the community not including symbiotic nitrogen fixation.
20. Dicyandiamide as nitrification inhibitor of pig slurry ammonium nitrogen in soil
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Rogério Gonzatto
2016-05-01
Full Text Available ABSTRACT: Inhibition of nitrification of ammoniacal nitrogen pig slurry after its application to the soil can mitigate nitrogen (N losses by nitrate (NO3 - denitrification and leaching, with economical and environmental benefits. However, the use of this strategy is incipient in Brazil and, therefore, requires further assessment. The aim of this study was to evaluate the efficiency of dicyandiamide (DCD nitrification inhibitor in slowing the nitrification of ammoniacal N applied to the soil with pig slurry (PS. For this, incubation was performed in laboratory, where nitrification was assessed by NO3 - accumulation in the soil. Rates of 2.8, 5.7 and 11.3kg DCD ha-1 were compared, being applied to the soil during PS addition. Nitrification was inhibited by DCD, and inhibition magnitude and duration depended on DCD applied rate. At a dose of 11.3kg ha-1 DCD, nitrification was completely inhibited in the first 12 days. During the first month after PS application, each 2.8kg of DCD increase applied per hectare promoted NO3 --N reduction in the soil of 13.3kg ha-1, allowing longer ammoniacal N maintenance in the soil.
1. Carbon dioxide emission from maize straw incubated with soil under various moisture and nitrogen levels
International Nuclear Information System (INIS)
Abro, S.A.; Tian, X.; Hussain, Q.; Talpur, M.; Singh, U.
2012-01-01
A laboratory incubation experiment was conducted to investigate the decomposition of maize straw incorporated into soil amended with nitrogen (N) and moisture (M) levels. Clay loam topsoil amended with maize straw was adjusted to four initial nitrogen treatments (C/N ratios of 72, 36, 18, and 9) and four moisture levels (60%, 70%, 80% and 90 % of field capacity) for the total of 16 treatments and incubated at 20 deg. C for 51 days. CO/sub 2/-C evolved was regularly recorded for all treatments during entire incubation period. Results showed that the mixing of straw with soil accelerated decomposition rates and enhanced cumulative CO/sub 2/-C production. The incorporation of straw brought about 50% increase in the cumulative CO/sub 2/-C production as compared with controls. About 45% of added maize straw C was mineralized to CO/sub 2/-C in 51 days. We conclude that incorporation of straw into soil along with the addition of N and moisture levels significantly affected CO/sub 2/-C evolution, cumulative CO/sub 2-C/, C mineralization and soil organic carbon deposition. The CO/sub 2/ emission was in positive correlation with (R2=0.99) N, moisture and incubation time (days). The straw returning into soil may enhance carbon pools and, thus will improve soil and environmental quality. (author)
2. Organic nitrogen rearranges both structure and activity of the soil-borne microbial seedbank.
Science.gov (United States)
Leite, Márcio F A; Pan, Yao; Bloem, Jaap; Berge, Hein Ten; Kuramae, Eiko E
2017-02-15
Use of organic amendments is a valuable strategy for crop production. However, it remains unclear how organic amendments shape both soil microbial community structure and activity, and how these changes impact nutrient mineralization rates. We evaluated the effect of various organic amendments, which range in Carbon/Nitrogen (C/N) ratio and degradability, on the soil microbiome in a mesocosm study at 32, 69 and 132 days. Soil samples were collected to determine community structure (assessed by 16S and 18S rRNA gene sequences), microbial biomass (fungi and bacteria), microbial activity (leucine incorporation and active hyphal length), and carbon and nitrogen mineralization rates. We considered the microbial soil DNA as the microbial seedbank. High C/N ratio favored fungal presence, while low C/N favored dominance of bacterial populations. Our results suggest that organic amendments shape the soil microbial community structure through a feedback mechanism by which microbial activity responds to changing organic inputs and rearranges composition of the microbial seedbank. We hypothesize that the microbial seedbank composition responds to changing organic inputs according to the resistance and resilience of individual species, while changes in microbial activity may result in increases or decreases in availability of various soil nutrients that affect plant nutrient uptake.
3. From where and how do plants and microbes get nitrogen? Revisiting paradigms of soil nitrogen availability
Science.gov (United States)
Grandy, S.
2017-12-01
Despite decades of research progress, soil biogeochemists are still debating in different ecosystems what pools and fluxes provide N to plants and microbes. Current concepts argue that N mineralization regulates the supply of N for plants and microorganisms, and is a `gatekeeper' for environmental N losses. The prevailing paradigm also argues that the chemistry of plant litter inputs (e.g. initial C:N ratio) primarily drives N mineralization rates, existing as a universal regulator of a switch between net N immobilization versus net N mineralization. However, decomposer community enzyme upregulation drives proteolysis, the exocellular first step in N mineralization; then, cellular carbon use efficiency and stoichiometry are internal microbial physiological processes driving ammonification rates. Further, N mineralization is only one of multiple, microbial-driven sequences in soils that regulate bioavailable N. Emerging evidence and new conceptual models from both the ecological and biogeoscience communities argue that while depolymerization is a critical first step, clay minerals may be an important and overlooked mediator of bioavailable N, and especially in the soil rhizosphere they are both a large source and sink for N. Mineral-associated organic matter (MAOM) can hold up to 20x more N than particulate fractions, is a rich reservoir of proteins, amino acids, and nucleic acids, and is mobilized by microbes and their interactions with plants. We use this and other emerging information to develop a new model of N availability in soils, highlighting: mineralization is strongly influenced by microbial physiological traits; the various steps in N mineralization have different drivers and can become decoupled; minerals are a strong sink and source for bioavailable N that is regulated by interactions between plants and microbial communities; and plants are a driving force in the soil N cycle for their ability to prime mineral N, and influence the structure and function
4. Nitrogen in soil water at five nitrogen-enriched forest sites in Sweden
International Nuclear Information System (INIS)
Ring, Eva
2001-01-01
Increased inputs of N to forest land may increase acidification and eutrophication. This thesis deals with N in soil water at 50 cm depth in N-enriched coniferous forests in Sweden. The experimental sites were enriched in N, either by fertilization or deposition. Soil water was collected by suction cups at varying degrees of N enrichment, after clear felling at two sites in central (Billingsjoen) and S Sweden (Farabol), and in three closely situated Norway spruce stands in SW Sweden. Billingsjoen was fertilized with ammonium nitrate at totals of 360-1800 kg N ha -1 , and Farabol with urea at totals of 600 kg N ha -1 . At clearfelling, which was performed six and seven years after the last fertilization, the soil N storage was increased by fertilization at Billingsjoen but not at Farabol. At Billingsjoen, the soil-water concentration of nitrate increased with increasing N dose. The increased nitrate concentrations reduced pH by up to nearly two units. In the eighth year after clear felling, the effects on all major cations and anions in the control, the 360 and 1800 kg N ha -1 treatments were examined. At the high N dose, nitrate and aluminium had significantly increased, and the pH and acid-neutralizing capacity had decreased, compared with the control and the low N dose. At Farabol, the estimated total leaching of nitrate-N in the control surpassed that of the N treatment by approximately 40%. The difference in leaching appears attributable to the greater biomass and N storage of the field-layer vegetation in the N treatment than in the control. At Farabol, the field-layer vegetation seems to have acted as an important sink for N as opposed to the Billingsjoen clearcut where the field layer was sparse. The Norway spruce stands in SW Sweden had a similar N deposition, but the concentrations of nitrate in soil water and estimated leaching rates differed substantially. In the soil with the highest leaching rate, potential nitrification was largest and the C to N
5. Barley Benefits from Organic Nitrogen in Plant Residues Applied to Soil using 15N Isotope Dilution
International Nuclear Information System (INIS)
Gadalla, A.M.; Galal, Y.G.M.; Abdel Aziz, H.A.; El-Degwy, S.M.A.; Abd El-Haleem, M.
2008-01-01
The experiment was carried out in pots (sandy soil cultivated with Barley plant) under greenhouse conditions, at Inshas, Egypt. The aim was to evaluate the transformation of nitrogen applied either as mineral form ( 15 NH 4 ) 2 SO 4 , or as organic-material-N (plant residues) .Basal recommended doses of P and K were applied. Labeled 15 N as( 15 NH 4 ) 2 SO 4 (5 % a.e) or plant residues (ground leuceana forage, compost, and mixture of them) were applied at a rate of 20 kg N/ ha). 15 N technique was used to evaluate N-uptake and fertilizer use efficiency. The treatments were arranged in a completely randomized block design under greenhouse conditions. The obtained results showed that the dry weight of barley shoots was positively affected by reinforcement of mineral- N with organic-N. On the other hand, the highest dry weight was estimated with leuceana either applied alone or reinforced with mineral N. Similar trend was noticed with N uptake but only with organic N, while with treatment received 50% organic-N. plus 50% mineral- N. the best value of N uptake was recorded with mixture of leuceana and compost. The amount of Ndff was lowest where fertilizer 15 N was applied alone. Comparing Ndff for the three organic treatments which received a combination of fertilizer- 15 N+organic-material-N, results showed that the highest Ndff was occurred with mixture of leuceana and compost, whereas the lowest was induced with individual leuceana treatment. 15 N recovery in shoots of barley ranged between 22.14 % to 82.16 %. The lowest occurred with application of mineral 15 N alone and; the highest occurred where mineral 15 N was mixed with compost or leucaena-compost mixture
6. Mineralization of residual fertilizer nitrogen in soil after rice harvest
International Nuclear Information System (INIS)
Hazarika, S.; Sarkar, M.C.
1994-01-01
Remineralization of immobilized 15 N labelled urea N applied to rice crop at the rate of 180 kg N/ha was determined. Mineral N increased rapidly up to 14 days of incubation and thereafter remained more or less constant. The recovery of fertilizer as mineral N varied between 0.7 and 3.1 μg/g soil. The percent mineralization of labelled organic N ranged between 3.1 and 9.5. (author). 5 refs., 2 tabs., 1 fig
7. Nitrogen isotope compositions and spatial distribution characteristics of soil in the process of karst rocky desertification
International Nuclear Information System (INIS)
Luo Xuqiang; Wang Shijie; Wang Chengyuan; Liang Yuhua; Liao Xinrong; Yang Hongyan
2011-01-01
Isotopic composition and spatial distribution characteristic of total nitrogen of the surficial soil in karst rocky desertification area, including different types, different grades and different disturbed modes karst rocky desertification within the same small catchment, which belong to the Wangjiazhai peak-cluster depression basin and located in Qingzhen City, Guizhou Province were discussed in this study. Results showed that δ 15 N values of total nitrogen in top soil in yellow soil area were mainly between +0.35‰ ∼ +6.82% with the average of +4.50‰, and between +2.70‰ ∼ +6.50‰ in black calcareous with the average of +4.27‰. In both yellow soil area and black calcareous area, there were no significant difference in the δ 15 N values of total nitrogen on sample lands of rocky desertification at different levels, different ways of interruption and different slope positions, and no obvious difference on the whole (P≤0.05), which is mainly due to the high habitat heterogeneity of karst area. (authors)
8. [Transformation Regularity of Nitrogen in Aqueous Product Derived from Hydrothermal Liquefaction of Sewage Sludge in Subcritical Water].
Science.gov (United States)
Sun, Yan-qing; Sun, Zhen; Zhang, Jing-lai
2015-06-01
Hydrothermal liquefaction in subcritical water is a potential way to treat sewage sludge as a resource rather than a waste. This study focused on the transformation regularity of nitrogen in aqueous product which was derived from hydrothermal liquefaction of sewage sludge under different operating conditions. Results showed, within the studied temperature scope and time span, the concentration of total nitrogen (TN) fluctuated in the range of 2867.62 mg x L(-1) to 4171.30 mg x L(-1). The two major exiting formation of nitrogen in aqueous product was ammonia nitrogen (NH4+ -N) and organic nitrogen (Org-N). NH4+ -N possessed 54.6%-90.7% of TN, while Org-N possessed 7.4%-44.5%. The concentration of nitrate nitrogen (NO- -N) was far more less than NH4+ -N and Org-N. Temperature had a great influence on the transformation regularity of nitrogen. Both the concentration of TN and Org-N increased accordingly to the increase of reaction temperature. With the reaction time prolonging, the concentration of TN and Org-N increased, while the concentration of NH4+ -N increased first, then became stationary, and then decreased slightly.
9. Disturbance of Soil Organic Matter and Nitrogen Dynamics: Implications for Soil and Water Quality
Science.gov (United States)
2004-06-30
Elliott, E.T., 1992. Particulate soil organic- matter changes across a grassland cultivation sequence. Soil Sci. Soc. Am. J. 56, 777–783. Dale, V.H...C.A., Elliott, E.T., 1992. Particulate soil organic-matter changes across a grassland cultivation sequence. Soil Science Society of America Journal...1645-1650. Van Straalen, N.M. 1997. How to measure no effect. 2. Threshold effects in ecotoxicology . Environmetrics 8: 249-253. Verburg, P.S.J
10. Soil solution and extractable soil nitrogen response to climate change in two boreal forest ecosystems
NARCIS (Netherlands)
Verburg, P.H.
2005-01-01
Several studies show that increases in soil temperature result in higher N mineralization rates in soils. It is, however, unclear if additional N is taken up by the vegetation or accumulates in the soil. To address this question two small, forested catchments in southern Norway were experimentally
11. Connecting carbon and nitrogen storage in rural wetland soil to groundwater abstraction for urban water supply.
Science.gov (United States)
Lewis, David Bruce; Feit, Sharon J
2015-04-01
We investigated whether groundwater abstraction for urban water supply diminishes the storage of carbon (C), nitrogen (N), and organic matter in the soil of rural wetlands. Wetland soil organic matter (SOM) benefits air and water quality by sequestering large masses of C and N. Yet, the accumulation of wetland SOM depends on soil inundation, so we hypothesized that groundwater abstraction would diminish stocks of SOM, C, and N in wetland soils. Predictions of this hypothesis were tested in two types of subtropical, depressional-basin wetland: forested swamps and herbaceous-vegetation marshes. In west-central Florida, >650 ML groundwater day(-1) are abstracted for use primarily in the Tampa Bay metropolis. At higher abstraction volumes, water tables were lower and wetlands had shorter hydroperiods (less time inundated). In turn, wetlands with shorter hydroperiods had 50-60% less SOM, C, and N per kg soil. In swamps, SOM loss caused soil bulk density to double, so areal soil C and N storage per m(2) through 30.5 cm depth was diminished by 25-30% in short-hydroperiod swamps. In herbaceous-vegetation marshes, short hydroperiods caused a sharper decline in N than in C. Soil organic matter, C, and N pools were not correlated with soil texture or with wetland draining-reflooding frequency. Many years of shortened hydroperiod were probably required to diminish soil organic matter, C, and N pools by the magnitudes we observed. This diminution might have occurred decades ago, but could be maintained contemporarily by the failure each year of chronically drained soils to retain new organic matter inputs. In sum, our study attributes the contraction of hydroperiod and loss of soil organic matter, C, and N from rural wetlands to groundwater abstraction performed largely for urban water supply, revealing teleconnections between rural ecosystem change and urban resource demand. © 2014 John Wiley & Sons Ltd.
12. Effects of nitrogen enrichment on soil organic matter in tropical forests with different ambient nutrient status
Science.gov (United States)
Vaughan, E.; Cusack, D. F.; McDowell, W. H.; Marin-Spiotta, E.
2017-12-01
Nitrogen (N) enrichment is a widespread and increasingly important human influence on ecosystems globally, with implications for net primary production and biogeochemical processes. Previous research has shown that N enrichment can alter soil carbon (C) cycling, although the direction and magnitude of the changes are not consistent across studies, and may change with time. Inconsistent responses to N additions may be due to differences in ambient nutrient status, and/or variable responses of plant C inputs and microbial decomposition. Although plant production in the tropics is not often limited by N, soil processes may respond differently to N enrichment. Our study uses a 15-year N addition experiment at two different tropical forest sites in the Luquillo Long-Term Ecological Research project site in Puerto Rico to address long-term changes in soil C pools due to fertilization. The two forests differ in elevation and ambient nutrient status. Soil sampling three and five years post-fertilization showed increased soil C concentrations under fertilization, driven by increases in mineral-associated C (Cusack et al. 2011). However, the longer-term trends at these sites are unknown. To this end, soil samples were collected following fifteen years of fertilization. Soils were sampled from 0-10 cm and 10-20 cm. Bulk soil C and N concentrations will be measured and compared to samples collected before fertilization (2002) and three years post fertilization (2005). We are using density fractionation to isolate different soil organic matter pools into a free light, occluded light, and dense, mineral associated fraction. These pools represent different mechanisms of soil organic matter stabilization, and provide more detailed insight into changes in bulk soil C. These data will provide insight into the effects of N enrichment on tropical forest soils, and how those effects may change through time with a unique long-term data set.
13. Particulate Organic Matter Affects Soil Nitrogen Mineralization under Two Crop Rotation Systems.
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Rongyan Bu
Full Text Available Changes in the quantity and/or quality of soil labile organic matter between and after different types of cultivation system could play a dominant role in soil nitrogen (N mineralization. The quantity and quality of particulate organic matter (POM and potentially mineralizable-N (PMN contents were measured in soils from 16 paired rice-rapeseed (RR/cotton-rapeseed (CR rotations sites in Hubei province, central China. Then four paired soils encompassing low (10th percentile, intermediate (25th and 75th percentiles, and high (90th percentile levels of soil PMN were selected to further study the effects of POM on soil N mineralization by quantifying the net N mineralization in original soils and soils from which POM was removed. Both soil POM carbon (POM-C and N (POM-N contents were 45.8% and 55.8% higher under the RR rotation compared to the CR rotation, respectively. The PMN contents were highly correlated with the POM contents. The PMN and microbial biomass N (MBN contents concurrently and significantly decreased when POM was removed. The reduction rate of PMN was positively correlated with changes in MBN after the removal of POM. The reduction rates of PMN and MBN after POM removal are lower under RR rotations (38.0% and 16.3%, respectively than CR rotations (45.6% and 19.5%, respectively. Furthermore, infrared spectroscopy indicated that compounds with low-bioavailability accumulated (e.g., aromatic recalcitrant materials in the soil POM fraction under the RR rotation but not under the CR rotation. The results of the present study demonstrated that POM plays a vital role in soil N mineralization under different rotation systems. The discrepancy between POM content and composition resulting from different crop rotation systems caused differences in N mineralization in soils.
14. Key intermediates in nitrogen transformation during microwave pyrolysis of sewage sludge: a protein model compound study.
Science.gov (United States)
Zhang, Jun; Tian, Yu; Cui, Yanni; Zuo, Wei; Tan, Tao
2013-03-01
The nitrogen transformations with attention to NH3 and HCN were investigated at temperatures of 300-800°C during microwave pyrolysis of a protein model compound. The evolution of nitrogenated compounds in the char, tar and gas products were conducted. The amine-N, heterocyclic-N and nitrile-N compounds were identified as three important intermediates during the pyrolysis. NH3 and HCN were formed with comparable activation energies competed to consume the same reactive substances at temperatures of 300-800°C. The deamination and dehydrogenation of amine-N compounds from protein cracking contributed to the formation of NH3 (about 8.9% of Soy-N) and HCN (6.6%) from 300 to 500°C. The cracking of nitrile-N and heterocyclic-N compounds from the dehydrogenation and polymerization of amine-N generated HCN (13.4%) and NH3 (31.3%) between 500 and 800°C. It might be able to reduce the HCN and NH3 emissions through controlling the intermediates production at temperatures of 500-800°C. Copyright © 2013 Elsevier Ltd. All rights reserved.
15. Nitrogen Chemistry and Coke Transformation of FCC Coked Catalyst during the Regeneration Process
Science.gov (United States)
Shi, Junjun; Guan, Jianyu; Guo, Dawei; Zhang, Jiushun; France, Liam John; Wang, Lefu; Li, Xuehui
2016-06-01
Regeneration of the coked catalyst is an important process of fluid catalytic cracking (FCC) in petroleum refining, however, this process will emit environmentally harmful gases such as nitrogen and carbon oxides. Transformation of N and C containing compounds in industrial FCC coke under thermal decomposition was investigated via TPD and TPO to examine the evolved gaseous species and TGA, NMR and XPS to analyse the residual coke fraction. Two distinct regions of gas evolution are observed during TPD for the first time, and they arise from decomposition of aliphatic carbons and aromatic carbons. Three types of N species, pyrrolic N, pyridinic N and quaternary N are identified in the FCC coke, the former one is unstable and tends to be decomposed into pyridinic and quaternary N. Mechanisms of NO, CO and CO2 evolution during TPD are proposed and lattice oxygen is suggested to be an important oxygen resource. Regeneration process indicates that coke-C tends to preferentially oxidise compared with coke-N. Hence, new technology for promoting nitrogen-containing compounds conversion will benefit the in-situ reduction of NO by CO during FCC regeneration.
16. Effects of Soil Compaction on Carbon and Nitrogen Sequestration in Soil and Wheat, Soil Physical Properties and Aggregates Stability (Case study: Northern of Aq Qala
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Z. Saieedifar
2016-09-01
Full Text Available Introduction: Soil compaction has become a widespread problem in the world and it is considered as one of the main factors affecting land degradation in arid and semi-arid agricultural land. Compaction in arable soils is a gradual phenomenon that appearing over time and most important factors that influence it include: soil properties, high clay content, low organic matter, and frequency of wet-dry in the soil, impervious layer of soil, load heavy agricultural implements and soil and water mismanagement. Compaction induced soil degradation affects about 68 million hectares of land globally. The vast majority of compaction in modern agriculture is caused by vehicular traffic. Carbon sequestration by long-term management operation of the plant and soil, not only increase the soil carbon storage but also lead to reduce the carbon exchange and greenhouse gases emissions like CO2 from the soil profile. The aim of this study was evaluating the effect of soil compaction on carbon and nitrogen sequestration of wheat and soil and some soil physical properties such as: aggregate stability, saturated soil moisture content, bulk density and soil porosity. Materials and Methods: This experiment was accomplished in which is located near Aq Qala in a randomized completely block design (with 4 treatments and 3 replications. Soil compaction was artificially created by using a 5/7 ton heavy tractor. The treatments arrangements were: 1 T1: control, 2 T2: twice passing of tractor, 3 T3: four time of passing tractor, and 4 T4: six time of passing heavy tractor. Utilize of all agricultural inputs (fertilizers, herbicides, etc. has been identical for all treatments. Since rain-fed farming is the common method to cultivation of cereals in the study area, so no complementary irrigation was carried out in this period. In this study, after the measurement of the parameters, the data were analyzed by using SPSS 16.0 Software. LSD test was used for comparison of means
17. Phosphorus Characteristics with Controlled Nitrogen in Fertile Soils in Protected Vegetable Field
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WANG Heng
2014-06-01
Full Text Available There is an unreasonable phenomenon of fertilization in vegetable facility cultivation, with the serious imbalance of soil nutrient. In purpose of understanding the absorption characteristics of phosphorus from nitrogen-rich soil, a long-term nitrogen-controlled experiment was carried from the year 2004 to 2007, and a split plot experiment of leaching was carried in winter-spring season of 2007. The results showed that the content of phosphorus varied with different nitrogen control. The TP was decreased with nitrogen supply of none(NN 、organic manure(MN 、organic manure and straw(MN+S, and the decreased range was NN>MN>MN+S, meanwhile the increase range of TP was traditional-nitrogen(CN >traditional-nitrogen+straw(CN+S >optimized-nitrogen+straw(SN+S >optimized-nitrogen(SN. The available P with CN and CN+S reached to 213.7 mg· kg -1 、225.4 mg·kg -1, which increased by 17.1 percent and 23.5 percent, which declared the phosphorus was accumulated; The available P with other nitrogen controlled decreased with the range of NN>MN>MN+S>SN+S>SN跃CN>CN+S, which showed that the supply reduction of nitrogen could slowdown the phosphorus accumulated and promote the utilization ratio of phosphorus. The organophosphorus was increased except NN, with obvious increase with CN、CN+S（308.4 mg·kg -1 、331.4 mg·kg -1 by 28.5 percent and 38.2 percent. The absorption coefficient of phosphorus with SN+S(P 2 O 5，mg· 100 g -1 reached to 1 571, increased by 143.6 percent; Otherwise the absorption coefficient of phosphorus with CN、CN+S showed negative growth, the CN dipped to 416（P 2 O 5，mg·100 g -1 by 35.5 percent. Adding wheat straw could greatly improved the capacity of absorption of phosphorus and slow down the accumulation of available phosphorus to some extent. The concentrations of total phosphorus in the filtrate with SN+S were less than SN, contrary to the concentration of organophosphorus, thus the straw returning had a certain effect on
18. [Nitrogen fixation potential of biological soil crusts in southeast edge of Tengger Desert, Northwest China].
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Zhang, Peng; Li, Xin-Rong; Zhang, Zhi-Shan; Pan, Yan-Xia; Liu, Yan-Mei; Su, Jie-Qiong
2012-08-01
Taking three typical types of biological soil crusts (BSCs), i.e., cyanobacterial-algal crust, lichen crust, and moss crust, in the southeast fringe of Tengger Desert as test objects, this paper studied their nitrogen fixation potential, seasonal fluctuation, and responses to the environmental factors from June 2010 to May 2011. During the whole study period, the nitrogenase activity (NA) of the cyanobacterial-algal, lichen, and moss crusts had significant difference, being 14-133, 20-101, and 4-28 micromol x m(-2) x h(-1), respectively, which indicated the critical role of the species composition of BSCs in nitrogen fixation. The NA of the three crust types had similar response characteristics to environmental factors. The NA had less correlation with the precipitation during the study period, but was positively correlated to the spring > summer > winter. The high air temperature in summer and the low air temperature (desert zone had nitrogen fixation capacity throughout the year, and the controlling effects of environmental factors on the nitrogen fixation were hierarchical. Water condition was the key factor affecting the nitrogen fixation rate and duration of the crusts, while under the conditions of sufficient water supply and carbon storage, heat condition dominated the crusts nitrogen fixation rate.
19. Effect of Continuous Agriculture of Grassland Soils of the Argentine Rolling Pampa on Soil Organic Carbon and Nitrogen
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Luis A. Milesi Delaye
2013-01-01
Full Text Available Long-term soil organic carbon (SOC and soil organic nitrogen (SON following cultivation of grassland soils (100/120-year tillage (T + 20/30-year no tillage (NT of the Rolling Pampa were studied calibrating the simple AMG model coupled with the natural 13C abundance measurements issued from long-term experiments and validating it on a data set obtained by a farmer survey and by long-term NT experiments. The multisite survey and NT trials permitted coverage of the history of the 140 years with agriculture. The decrease in SOC and SON storage that occurred during the first twenty years by a loss through biological activity was 27% for SOC and 32% for SON. The calibrated model described the SOC storage evolution very well and permitted an accurate simultaneous estimation of their three parameters. The validated model simulated well SOC and SON evolution. Overall, the results analyzed separately for the T and NT period indicated that the active pool has a rapid turnover (MRT ~9 and 13 years, resp. which represents 50% of SOC in the native prairie soil and 20% of SOC at equilibrium after NT period. NT implementation on soils with the highest soil organic matter reserves will continue to decrease (17% for three decades later under current annual addition.
20. Microbial properties explain temporal variation in soil respiration in a grassland subjected to nitrogen addition
Science.gov (United States)
Li, Yue; Liu, Yinghui; Wu, Shanmei; Niu, Lei; Tian, Yuqiang
2015-01-01
The role of soil microbial variables in shaping the temporal variability of soil respiration has been well acknowledged but is poorly understood, particularly under elevated nitrogen (N) deposition conditions. We measured soil respiration along with soil microbial properties during the early, middle, and late growing seasons in temperate grassland plots that had been treated with N additions of 0, 2, 4, 8, 16, or 32 g N m−2 yr−1 for 10 years. Representing the averages over three observation periods, total (Rs) and heterotrophic (Rh) respiration were highest with 4 g N m−2 yr−1, but autotrophic respiration (Ra) was highest with 8 to 16 g N m−2 yr−1. Also, the responses of Rh and Ra were unsynchronized considering the periods separately. N addition had no significant impact on the temperature sensitivity (Q10) for Rs but inhibited the Q10 for Rh. Significant interactions between observation period and N level occurred in soil respiration components, and the temporal variations in soil respiration components were mostly associated with changes in microbial biomass carbon (MBC) and phospholipid fatty acids (PLFAs). Further observation on soil organic carbon and root biomass is needed to reveal the long-term effect of N deposition on soil C sequestration. PMID:26678303
1. Transformações do nitrogênio no solo após adição de dejeto líquido e cama sobreposta de suínos Nitrogen transformations in soil after the addition of pig slurry and pig deep‑litter
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Sandro José Giacomini
2013-02-01
Full Text Available O objetivo deste trabalho foi avaliar as transformações do N no solo após a aplicação de dejeto líquido (DLS e cama sobreposta (CSS de suínos, com e sem palha de aveia, e com e sem incorporação ao solo. Os tratamentos avaliados foram: solo (S, S + palha incorporada (S + Pi, S + palha em superfície (S + Ps, S + CSS incorporada (S + CSSi, S + CSS em superfície (S + CSSs, S + DLS incorporado (S + DLSi, S + DLS em superfície (S + DLSs, S + Pi + DLSi e S + Ps + DLSs. Avaliaram-se a volatilização de amônia, a nitrificação e a mineralização do N do DLS e da CSS. A incorporação do DLS reduziu a volatilização de amônia em 93%, em comparação à aplicação na superfície do solo. O N amoniacal da CSS foi nitrificado nos cinco primeiros dias. A taxa de nitrificação líquida foi duas vezes maior com a incorporação do DLS ao solo do que na superfície. A mineralização do N orgânico não diferiu com o modo de aplicação do DLS e da CSS no solo. Na CSS, 14,6% do N foi mineralizado, contra 34,9% no DLS. A aplicação do DLS com a palha de aveia na superfície do solo favorece a imobilização microbiana de N, mas não reduz as perdas de N por volatilização de amônia.The objective of this work was to evaluate soil N transformations after the application of pig slurry (PS and pig deep‑litter (PDL, with and without oat straw, and with and without incorporation into the soil. The evaluated treatments were: soil (S, S + incorporated straw (S + Sti, S + straw on surface (S + Sts, S + incorporated PDL (S + PDLi, S + PDL on surface (S + PDLs, S + incorporated PS (S + PSi, S + PS on surface (S + PSs, S + Sti + Psi, and S + Sts + PSs. The following were evaluated: ammonia volatilization, nitrification and N mineralization of PS and PDL. Incorporation of PS reduced ammonia volatilization in 93% when compared to surface application. The ammoniacal N in PDL was nitrified within the first five days. The net nitrification rate was two
2. PUNCS: Towards Predictive Understanding of Nitrogen Cycling in Soils
Energy Technology Data Exchange (ETDEWEB)
Loeffler, Frank E. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Microbiology. Dept. of Civil and Environmental Engineering. Center for Environmental Biotechnology; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Biosciences Division; Konstantinidis, Konstantinos T. [Georgia Inst. of Technology, Atlanta, GA (United States); Sanford, Robert A. [Univ. of Illinois, Urbana, IL (United States)
2015-11-30
In anoxic environments, the major nitrate/nitrite-consuming processes are respiratory ammonification (also known as dissimilatory nitrate reduction to ammonium) and denitrification (i.e., the formation of the gaseous products N2O and N2). Respiratory ammonification oxidizes more carbon per mole of nitrate than denitrification and generates a cation (NH4+), which is retained in soils and bioavailable for plants. Thus, these processes have profoundly different impacts on N retention and greenhouse gas (CO2, N2O) emissions. Microbes capable of respiratory ammonification or denitrification coexist but the environmental controls over these competing nitrate/nitrite-reducing processes are largely unknown. With the current level of understanding, predictions under what environmental conditions respiratory ammonification activity predominates leading to N-retention rather than N-loss are tenuous. Further, the diversity of genes encoding the ammonium-forming nitrite reductase NrfA is poorly defined hampering the development of tools to assess and monitor this activity in environmental systems. Incomplete denitrification leads to N2O, a gas implicated in ozone layer destruction and climate change. The conversion of the greenhouse gas N2O to benign N2 is catalyzed by N2O reductase, the characteristic enzyme system of complete denitrifiers. Thus, efforts to estimate N2O conversion to N2 have focused on the well-characterized denitrifier nosZ genes; however, our understanding of the diversity of genes and organisms contributing to N2O consumption is incomplete. This paucity of information limits the development of more accurate, predictive models for C- and N-fluxes and greenhouse gas emissions. A comprehensive analysis of the key catalyst of respiratory ammonification, ammonia-forming nitrite reductase NrfA, revealed the evolutionary history of
3. Effects of elevated nitrogen deposition on soil microbial biomass carbon in major subtropical forests of southern China
Institute of Scientific and Technical Information of China (English)
Hui WANG; Jiangming MO; Xiankai LU; Jinghua XUE; Jiong LI; Yunting FANG
2009-01-01
The effects of elevated nitrogen deposition on soil microbial biomass carbon (C) and extractable dissolved organic carbon (DOC) in three types of forest of southern China were studied in November, 2004 and June, 2006. Plots were established in a pine forest (PF), a mixed pine and broad-leaved forest (MF) and monsoon evergreen broad-leaved forest (MEBF) in the Dinghushan Nature Reserve. Nitrogen treatments included a control (no N addition), low N (50 kg N/(hm2.a)), medium N (100 kg N/ (hm2. a)) and high N (150 kg N/(hm2. a)). Microbial biomass C and extractable DOC were determined using a chloro-form fumigation-extraction method. Results indicate that microbial biomass C and extractable DOC were higher in June, 2006 than in November, 2004 and higher in the MEBF than in the PF or the MF. The response of soil microbial biomass C and extractable DOC to nitrogen deposition varied depending on the forest type and the level of nitrogen treatment. In the PF or MF forests, no significantly different effects of nitrogen addition were found on soil microbial biomass C and extractable DOC. In the MEBF, however, the soil microbial biomass C generally decreased with increased nitrogen levels and high nitrogen addition significantly reduced soil microbial biomass C. The response of soil extractable DOC to added nitrogen in the MEBF shows the opposite trend to soil microbial biomass C. These results suggest that nitrogen deposition may increase the accumulation of soil organic carbon in the MEBF in the study region.
4. Mobilization of interactions between functional diversity of plant and soil organisms on nitrogen availability and use
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Drut, Baptiste; Cassagne, Nathalie; Cannavacciuolo, Mario; Brauman, Alain; Le Floch, Gaëtan; Cobo, Jose; Fustec, Joëlle
2017-04-01
Keywords: legumes, earthworms, microorganisms, nitrogen, interactions Both aboveground and belowground biodiversity and their interactions can play an important role in crop productivity. Plant functional diversity, such as legume based intercrops have been shown to improve yields through plant complementarity for nitrogen use (Corre-Hellou et al., 2006). Moreover, plant species or plant genotype may influence the structure of soil microorganism communities through the composition of rhizodeposits in the rhizosphere (Dennis et al., 2010). Belowground diversity can also positively influence plant performance especially related to functional dissimilarity between soil organisms (Eisenhauer, 2012). Earthworms through their burrowing activity influence soil microbial decomposers and nutrient availability and have thus been reported to increase plant growth (Brown, 1995; Brown et al., 2004). We hypothesize that i) plant functional (genetic and/or specific) diversity associated to functional earthworms diversity are key drivers of interactions balance to improve crop performances and ii) the improvement of plant performances can be related to change in the structure of soil microorganism communities due to the diversity of rhizodeposits and the burrowing activity of earthworms. In a first mesocosm experiment, we investigated the effect of a gradient of plant diversity - one cultivar of wheat (Triticum aestivum L.), 3 different wheat cultivars, and 3 different cultivars intercropped with clover (Trifolium hybridum L.) - and the presence of one (endogeic) or two (endogeic and anecic) categories of earthworms on biomass and nitrogen accumulation of wheat. In a second mesocosm experiment, we investigated the influence of three species with different rhizodeposition - wheat, rapeseed (Brassica napus L. ) and faba bean (Vicia faba L.) in pure stand or intercropped - and the presence of endogeic earthworms on microbial activity and nitrogen availability. In the first experiment
5. Ubiquity of insect-derived nitrogen transfer to plants by endophytic insect-pathogenic fungi: an additional branch of the soil nitrogen cycle.
Science.gov (United States)
Behie, Scott W; Bidochka, Michael J
2014-03-01
The study of symbiotic nitrogen transfer in soil has largely focused on nitrogen-fixing bacteria. Vascular plants can lose a substantial amount of their nitrogen through insect herbivory. Previously, we showed that plants were able to reacquire nitrogen from insects through a partnership with the endophytic, insect-pathogenic fungus Metarhizium robertsii. That is, the endophytic capability and insect pathogenicity of M. robertsii are coupled so that the fungus acts as a conduit to provide insect-derived nitrogen to plant hosts. Here, we assess the ubiquity of this nitrogen transfer in five Metarhizium species representing those with broad (M. robertsii, M. brunneum, and M. guizhouense) and narrower insect host ranges (M. acridum and M. flavoviride), as well as the insect-pathogenic fungi Beauveria bassiana and Lecanicillium lecanii. Insects were injected with (15)N-labeled nitrogen, and we tracked the incorporation of (15)N into two dicots, haricot bean (Phaseolus vulgaris) and soybean (Glycine max), and two monocots, switchgrass (Panicum virgatum) and wheat (Triticum aestivum), in the presence of these fungi in soil microcosms. All Metarhizium species and B. bassiana but not L. lecanii showed the capacity to transfer nitrogen to plants, although to various degrees. Endophytic association by these fungi increased overall plant productivity. We also showed that in the field, where microbial competition is potentially high, M. robertsii was able to transfer insect-derived nitrogen to plants. Metarhizium spp. and B. bassiana have a worldwide distribution with high soil abundance and may play an important role in the ecological cycling of insect nitrogen back to plant communities.
6. Soil Fauna Affects Dissolved Carbon and Nitrogen in Foliar Litter in Alpine Forest and Alpine Meadow.
Science.gov (United States)
Liao, Shu; Yang, Wanqin; Tan, Yu; Peng, Yan; Li, Jun; Tan, Bo; Wu, Fuzhong
2015-01-01
Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) are generally considered important active biogeochemical pools of total carbon and nitrogen. Many studies have documented the contributions of soil fauna to litter decomposition, but the effects of the soil fauna on labile substances (i.e., DOC and TDN) in litter during early decomposition are not completely clear. Therefore, a field litterbag experiment was carried out from 13th November 2013 to 23rd October 2014 in an alpine forest and an alpine meadow located on the eastern Tibetan Plateau. Litterbags with different mesh sizes were used to provide access to or prohibit the access of the soil fauna, and the concentrations of DOC and TDN in the foliar litter were measured during the winter (the onset of freezing, deep freezing and thawing stage) and the growing season (early and late). After one year of field incubation, the concentration of DOC in the litter significantly decreased, whereas the TDN concentration in the litter increased. Similar dynamic patterns were detected under the effects of the soil fauna on both DOC and TDN in the litter between the alpine forest and the alpine meadow. The soil fauna showed greater positive effects on decreasing DOC concentration in the litter in the winter than in the growing season. In contrast, the dynamics of TND in the litter were related to seasonal changes in environmental factors, rather than the soil fauna. In addition, the soil fauna promoted a decrease in litter DOC/TDN ratio in both the alpine forest and the alpine meadow throughout the first year of decomposition, except for in the late growing season. These results suggest that the soil fauna can promote decreases in DOC and TDN concentrations in litter, contributing to early litter decomposition in these cold biomes.
7. Soil microbes shift C-degrading activity along an ambient and experimental nitrogen gradient
Science.gov (United States)
Moore, J.; Frey, S. D.
2017-12-01
The balance between soil carbon (C) accumulation and decomposition is determined in large part by the activity and biomass of soil microbes, and yet their sensitivity to global changes remains unresolved. Atmospheric nitrogen (N) deposition has increased 22% (for NH4+) in the last two decades despite initiation of the Clean Air Act. Nitrogen deposition alters ecosystem processes by changing nutrient availability and soil pH, creating physiologically stressful environments that select for stress tolerant microbes. The functional fungal community may switch from domination by species with traits associated with decomposition via oxidative enzymes to traits associated with stress tolerance if global changes push fungal physiological limits. We examined changes in soil microbial activity across seven sites representing a gradient of ambient atmospheric N deposition, and five of these sites also had long-term N addition experiments. We measured changes in abundance of decomposition genes and C mineralization rates as indicators of microbial activity. We expected microbes to be less active with high N deposition, thus decreasing C mineralization rates. We found that C mineralization rates declined with total N deposition (ambient plus experimental additions), and this decline was more sensitive to N deposition where it occurred naturally compared to experimental treatments. Carbon mineralization declined by 3% in experimentally fertilized soils compared to 10% in control soils for every 1 kg/ha/y increase in ambient N deposition. Thus, microbes exposed to ambient levels of N deposition (2 - 12 kg/ha/y) had a stronger response than those exposed to fertilized soils (20 - 50 kg/ha/y). Long-term experimental N-addition seems to have selected for a microbial community that is tolerant of high N deposition. In sum, we provide evidence that soil microbial activity responded to N deposition, and may shift over time to a community capable of tolerating environmental change.
8. Bacillus spp. from rainforest soil promote plant growth under limited nitrogen conditions.
Science.gov (United States)
Huang, X-F; Zhou, D; Guo, J; Manter, D K; Reardon, K F; Vivanco, J M
2015-03-01
The aim of this study was to evaluate effects of PGPR (plant growth-promoting rhizobacteria) isolated from rainforest soil on different plants under limited nitrogen conditions. Bacterial isolates from a Peruvian rainforest soil were screened for plant growth-promoting effects on Arabidopsis (Col-0). Four selected isolates including one Bacillus subtilis, two B. atrophaeus and one B. pumilus significantly promoted growth of Zea mays L. and Solanum lycopersicum under greenhouse conditions. Moreover, the PGPRs significantly promoted growth of S. lycopersicum in both low and nitrogen-amended soil conditions. These PGPR strains were further studied to obtain insights into possible mechanisms of plant growth promotion. Volatile chemicals from those isolates promoted Arabidopsis growth, and the expression of genes related to IAA production was induced in the Arabidopsis plants treated with PGPRs. Further, selected PGPR strains triggered induced systemic resistance (ISR) against Pseudomonas syringae pv tomato DC3000 in Arabidopsis. PGPR strains isolated from the rainforest soil promoted the plant growth of Arabidopsis, corn and tomato. New PGPR that have wider adaptability to different crops, soils and environmental conditions are needed to decrease our reliance on agricultural amendments derived from fossil-based fuels. The PGPRs isolated from a nonagricultural site constitute new plant growth-promoting strains that could be developed for agricultural uses. © 2014 The Society for Applied Microbiology.
9. Removal of nitrogen by a layered soil infiltration system during intermittent storm events.
Science.gov (United States)
Cho, Kang Woo; Song, Kyung Guen; Cho, Jin Woo; Kim, Tae Gyun; Ahn, Kyu Hong
2009-07-01
The fates of various nitrogen species were investigated in a layered biological infiltration system under an intermittently wetting regime. The layered system consisted of a mulch layer, coarse soil layer (CSL), and fine soil layer (FSL). The effects of soil texture were assessed focusing on the infiltration rate and the removal of inorganic nitrogen species. The infiltration rate drastically decreased when the uniformity coefficient was larger than four. The ammonium in the synthetic runoff was shown to be removed via adsorption during the stormwater dosing and nitrification during subsequent dry days. Stable ammonium adsorption was observed when the silt and clay content of CSL was greater than 3%. This study revealed that the nitrate leaching was caused by nitrification during dry days. Various patterns of nitrate flushing were observed depending on the soil configuration. The washout of nitrate was more severe as the silt/clay content of the CSL was greater. However, proper layering of soil proved to enhance the nitrate removal. Consequently, a strictly sandy CSL over FSL with a silt and clay content of 10% was the best configuration for the removal of ammonium and nitrate.
10. 200 years of soil carbon nitrogen and phosphorus change across the United Kingdom
Science.gov (United States)
Tipping, Ed; Quinton, John; Davies, Jessica; Bell, Vicky; Carnell, Ed; Dragosits, Ulli; Muhammed, Shibu; Naden, Pam; Stuart, Marianne; Tomlinson, Sam; Whitmore, Andy; Wu, Lianhai
2015-04-01
Human intervention over the last 200 years has resulted in vast changes to the fluxes of nitrogen (N) and phosphorus (P) entering the United Kingdom's landscape. Industrialisation has resulted in N deposition, agricultural intensification has seen widespread use of N and P fertilizers and societal actions have resulted in extensive land use change. To understand the consequences of these anthropogenic inputs for our soils, freshwaters and ecosystems it is necessary to take an integrated long term large scale approach. Integration across the compartments of the critical zone - from atmosphere, plants to soil and stream - is necessary in order to trace the effects of deposition, fertilization, cultivation and land use change. Coherent integration of C, N and P dynamics is also crucial, as biological processes tightly couple these cycles, so that in unison C N and P control the generation of biomass and consequent production of soil organic matter, having knock on effects for dissolved and particulate fluxes and ecosystem function. The Long-Term Large-Scale (LTLS) project is developing an integrated model that simulates the pools and fluxes of carbon, nitrogen and phosphorus (C, N, and P) between atmospheric, vegetation, soil and aquatic systems for the whole of the United Kingdom for a period spanning from the onset of the industrial revolution up until the present day. In this paper we will present results demonstrating the changes in the soil macronutrient cycles in response to agrarian and social change in the United Kingdom over the last 200 years
11. Research on the Effects of Drying Temperature on Nitrogen Detection of Different Soil Types by Near Infrared Sensors.
Science.gov (United States)
Nie, Pengcheng; Dong, Tao; He, Yong; Xiao, Shupei
2018-01-29
Soil is a complicated system whose components and mechanisms are complex and difficult to be fully excavated and comprehended. Nitrogen is the key parameter supporting plant growth and development, and is the material basis of plant growth as well. An accurate grasp of soil nitrogen information is the premise of scientific fertilization in precision agriculture, where near infrared sensors are widely used for rapid detection of nutrients in soil. However, soil texture, soil moisture content and drying temperature all affect soil nitrogen detection using near infrared sensors. In order to investigate the effects of drying temperature on the nitrogen detection in black soil, loess and calcium soil, three kinds of soils were detected by near infrared sensors after 25 °C placement (ambient temperature), 50 °C drying (medium temperature), 80 °C drying (medium-high temperature) and 95 °C drying (high temperature). The successive projections algorithm based on multiple linear regression (SPA-MLR), partial least squares (PLS) and competitive adaptive reweighted squares (CARS) were used to model and analyze the spectral information of different soil types. The predictive abilities were assessed using the prediction correlation coefficients (R P ), the root mean squared error of prediction (RMSEP), and the residual predictive deviation (RPD). The results showed that the loess (R P = 0.9721, RMSEP = 0.067 g/kg, RPD = 4.34) and calcium soil (R P = 0.9588, RMSEP = 0.094 g/kg, RPD = 3.89) obtained the best prediction accuracy after 95 °C drying. The detection results of black soil (R P = 0.9486, RMSEP = 0.22 g/kg, RPD = 2.82) after 80 °C drying were the optimum. In conclusion, drying temperature does have an obvious influence on the detection of soil nitrogen by near infrared sensors, and the suitable drying temperature for different soil types was of great significance in enhancing the detection accuracy.
12. Carbon and nitrogen in forest floor and mineral soil under six common European tree species
DEFF Research Database (Denmark)
Vesterdal, Lars; Schmidt, Inger K.; Callesen, Ingeborg
2007-01-01
The knowledge of tree species effects on soil C and N pools is scarce, particularly for European deciduous tree species. We studied forest floor and mineral soil carbon and nitrogen under six common European tree species in a common garden design replicated at six sites in Denmark. Three decades...... on forest floor C and N content was primarily attributed to large differences in turnover rates as indicated by fractional annual loss of forest floor C and N. The C/N ratio of foliar litterfall was a good indicator of forest floor C and N contents, fractional annual loss of forest floor C and N...
13. Evaluation of the symbiotic nitrogen fixation in soybean by labelling of soil organic matter
International Nuclear Information System (INIS)
Ruschel, A.P.; Freitas, J.R. de; Vose, P.B.
1982-01-01
An experiment was carried out using the isotopic dilution method to evaluate symbiotic nitrogen fixation in soybean grown in soil labelled with 15 N enriched organic matter. Symbiotic N 2 -fixed was 71-76% of total N in the plant. Non nodulated soybean utilized 56-59% N from organic matter and 40% from soil. Roots of nodulated plants had lower NdN 2 than aereal plant parts. The advantage of using labelled organic matter as compared with 15 N-fertilizer addition in evaluating N 2 -fixation is discussed. (Author) [pt
14. Transformations of N from the fertilizer applied to dark plastic soil under flooding conditions
International Nuclear Information System (INIS)
Lachataignerais B, E.; Aguilera, R.M.; Romero, R.M.; Sosa, J.L.
1993-01-01
The influence of flooding in dark plastic soil on the dynamics of amonification, nitrification of the contents of organic nitrogen, of the volatilization of the ammonia and other losses of nitrogen applied as enriched urea at 10 at of 15N , by means of laboratory experiments, using isotopic techniques have been studied. It has been observed that the interchangeable nitrogen from the fertilizer reached approximately a 75% of the one applied a week later, thus diminishing quickly up to values below the 20% seven weeks later
15. The analysis of soil cores polluted with certain metals using the Box-Cox transformation
International Nuclear Information System (INIS)
Meloun, Milan; Sanka, Milan; Nemec, Pavel; Kritkova, Sona; Kupka, Karel
2005-01-01
To define the soil properties for a given area or country including the level of pollution, soil survey and inventory programs are essential tools. Soil data transformations enable the expression of the original data on a new scale, more suitable for data analysis. In the computer-aided interactive analysis of large data files of soil characteristics containing outliers, the diagnostic plots of the exploratory data analysis (EDA) often find that the sample distribution is systematically skewed or reject sample homogeneity. Under such circumstances the original data should be transformed. The Box-Cox transformation improves sample symmetry and stabilizes spread. The logarithmic plot of a profile likelihood function enables the optimum transformation parameter to be found. Here, a proposed procedure for data transformation in univariate data analysis is illustrated on a determination of cadmium content in the plough zone of agricultural soils. A typical soil pollution survey concerns the determination of the elements Be (16 544 values available), Cd (40 317 values), Co (22 176 values), Cr (40 318 values), Hg (32 344 values), Ni (34 989 values), Pb (40 344 values), V (20 373 values) and Zn (36 123 values) in large samples. - A new procedure of statistical analysis, with exploratory data diagnostics and Box-Cox transformation was used
16. The analysis of soil cores polluted with certain metals using the Box-Cox transformation
Energy Technology Data Exchange (ETDEWEB)
Meloun, Milan [Department of Analytical Chemistry, University of Pardubice, CZ532 10 Pardubice (Czech Republic)]. E-mail: [email protected]; Sanka, Milan [Central Institute for Supervisiting and Testing in Agriculture Division of Agrochemistry, Soil and Plant Nutrition, Hroznova 2, CZ656 06 Brno - Pisarky (Czech Republic); Nemec, Pavel [Central Institute for Supervisiting and Testing in Agriculture Division of Agrochemistry, Soil and Plant Nutrition, Hroznova 2, CZ656 06 Brno - Pisarky (Czech Republic)]. E-mail: [email protected]; Kritkova, Sona [Department of Analytical Chemistry, University of Pardubice, CZ532 10 Pardubice (Czech Republic); Kupka, Karel [Trilobyte Statistical Software Ltd., CZ530 02 Pardubice (Czech Republic)]. E-mail: [email protected]
2005-09-15
To define the soil properties for a given area or country including the level of pollution, soil survey and inventory programs are essential tools. Soil data transformations enable the expression of the original data on a new scale, more suitable for data analysis. In the computer-aided interactive analysis of large data files of soil characteristics containing outliers, the diagnostic plots of the exploratory data analysis (EDA) often find that the sample distribution is systematically skewed or reject sample homogeneity. Under such circumstances the original data should be transformed. The Box-Cox transformation improves sample symmetry and stabilizes spread. The logarithmic plot of a profile likelihood function enables the optimum transformation parameter to be found. Here, a proposed procedure for data transformation in univariate data analysis is illustrated on a determination of cadmium content in the plough zone of agricultural soils. A typical soil pollution survey concerns the determination of the elements Be (16 544 values available), Cd (40 317 values), Co (22 176 values), Cr (40 318 values), Hg (32 344 values), Ni (34 989 values), Pb (40 344 values), V (20 373 values) and Zn (36 123 values) in large samples. - A new procedure of statistical analysis, with exploratory data diagnostics and Box-Cox transformation was used.
17. Sulphur and nitrogen supply - soil acidification and the absorption of nutrients in plants; Svovel og nitrogentilfoersel - jordforsuring og plantenes naeringstilgang
Energy Technology Data Exchange (ETDEWEB)
Abrahamsen, G
1996-01-01
Ecologically, soil is of the greatest interest as a growth medium for plants, and which affects the quality of ground water and surface water. In this connection, the paper looks upon how the increased deposition of sulphur, nitrogen and hydrogen ions affect the quality of soil as a growth medium for plants. Topics cover: Interaction between soil and plants, effects of acid rain in soil, and the effects of acid rain on plants. 11 refs., 1 tab.
18. The effect of hydraulic lift on organic matter decomposition, soil nitrogen cycling, and nitrogen acquisition by a grass species.
Science.gov (United States)
Armas, Cristina; Kim, John H; Bleby, Timothy M; Jackson, Robert B
2012-01-01
Hydraulic lift (HL) is the passive movement of water through plant roots, driven by gradients in water potential. The greater soil-water availability resulting from HL may in principle lead to higher plant nutrient uptake, but the evidence for this hypothesis is not universally supported by current experiments. We grew a grass species common in North America in two-layer pots with three treatments: (1) the lower layer watered, the upper one unwatered (HL), (2) both layers watered (W), and (3) the lower layer watered, the upper one unwatered, but with continuous light 24 h a day to limit HL (no-HL). We inserted ingrowth cores filled with enriched-nitrogen organic matter ((15)N-OM) in the upper layer and tested whether decomposition, mineralization and uptake of (15)N were higher in plants performing HL than in plants without HL. Soils in the upper layer were significantly wetter in the HL treatment than in the no-HL treatment. Decomposition rates were similar in the W and HL treatments and lower in no-HL. On average, the concentration of NH(4)(+)-N in ingrowth cores was highest in the W treatment, and NO(3)(-)-N concentrations were highest in the no-HL treatment, with HL having intermediate values for both, suggesting differential mineralization of organic N among treatments. Aboveground biomass, leaf (15)N contents and the (15)N uptake in aboveground tissues were higher in W and HL than in no-HL, indicating higher nutrient uptake and improved N status of plants performing HL. However, there were no differences in total root nitrogen content or (15)N uptake by roots, indicating that HL affected plant allocation of acquired N to photosynthetic tissues. Our evidence for the role of HL in organic matter decomposition and nutrient cycling suggests that HL could have positive effects on plant nutrient dynamics and nutrient turnover.
19. Soil Carbon and Nitrogen Stock as Affected by Agricultural Wastes in a Typic Haplusult of Owerri, Southeastern Nigeria
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Stanley Uchenna Onwudike
2016-07-01
Full Text Available We evaluated the effect of saw dust ash (SDA and poultry droppings (PD on soil physico-chemical properties, soil carbon and nitrogen stock and their effects on the growth and yield of okra (Abelmoshus esculentus on a typic haplusult in Owerri, Imo State Southeastern Nigeria. The experiment was a factorial experiment consisted of saw dust ash applied at the rates of 0, 5 and 10 t/ha and poultry droppings applied at the rates of 0, 5 and 10 t/ha. The treatments were laid out in a randomized complete block design and replicated four times. Results showed that plots amended with 10 t/ha PD + 10 t/ha SDA significantly reduced soil bulk density from 1.37 – 1.07 g/cm3, increased soil total porosity from 48.4 – 59.7% and the percentage of soil weight that is water (soil gravimetric moisture content was increased by 68.4%. There were significant improvements on soil chemical properties with plots amended with 10 t/ha PD + 10 t/ha SDA recording the highest values on soil organic carbon, soil total nitrogen and exchangeable bases. Plots amended with 10 t/ha PD + 10 t/ha SDA significantly increased soil carbon stock by 24% and soil nitrogen stock by 49.5% more than other treatments. There was significant increase in the growth of okra when compared to the un-amended soil with application of 10 t/ha PD + 10 t/ha SDA increasing the fresh okra pod yield by 78.5%. Significant positive correlation existed between SCS and organic carbon (r = 0.6128, exchangeable Mg (r= 0.5035, total nitrogen (r = 0.6167 and soil pH (r = 0.5221. SNS correlated positively with organic carbon (r = 0.5834, total nitrogen (r= 0.6101 and soil pH (r = 5150. Therefore applications of these agro-wastes are effective in improving soil properties, increasing soil carbon and nitrogen stock. From the results of the work, application of 10 t/ha PD + 10 t/ha SDA which was the treatment combination that improved soil properties and growth performances of okra than other treatments studied is
20. Effect of Phosphorous and Potassium Fertilization on Nitrogen Utilized by wheat Grown in Saline Soil Amended with Organic Manures
International Nuclear Information System (INIS)
Soliman, S.M.; Gadalla, A.M.; Kotb, E.A.; Mostafa, S.M.A.; Mansour, M.M.F.
2008-01-01
This study was carried out on poor saline soil located at Wad Ras Sudr, South Saini Governorate, and suffers from shortage of water resources. Therefore, we aimed to utilize this soil as well as the saline ground water for plant production. Organic fertilizers such as green manure(GM) or poultry manure(PM) can be used as nutrient sources, where it improves the physical, chemical and biological properties of the soil. Economically, the yield improvement and nutrient supply will reflect the potential use of such organic materials. Also, phosphorus and/or potassium supplementation separately or in combination with green or poultry manures improved the growth of wheat plants under such adverse condition of salinity. Application of 15 N technique indicated that labeled nitrogen added as ammonium sulphate (AS) to investigate and discrimination between the different N sources i.e. nitrogen derived from fertilizer (Ndff) and nitrogen derived from soil (Ndfs) as well as nitrogen use efficiency (FUE %)
1. Microbial transformations of nitrogen, sulfur and iron dictate vegetation composition in wetlands: a review
Directory of Open Access Journals (Sweden)
Leon P.M. Lamers
2012-04-01
Full Text Available The majority of studies on rhizospheric interactions between microbial communities and vegetation focus on pathogens, mycorrhizal symbiosis, and/or carbon transformations. Although the biogeochemical transformations of nitrogen (N, sulfur (S and iron (Fe have profound effects on plants, these effects have received far less attention. Firstly, all three elements are plant nutrients, and microbial activity significantly changes their mobility and availability. Secondly, microbial oxidation with oxygen supplied by radial oxygen loss (ROL from roots in wetlands causes acidification, while reduction using alternative electron acceptors leads to generation of alkalinity, affecting pH in the rhizosphere and hence plant composition. Thirdly, reduced species of all three elements may become phytotoxic. In addition, Fe cycling is tightly linked to that of S and phosphorus (P. As water level fluctuations are very common in wetlands, rapid changes in the availability of oxygen and alternative terminal electron acceptors will result in strong changes in the prevalent microbial redox reactions, with significant effects on plant growth. Depending on geological and hydrological settings, these interacting microbial transformations change the conditions and resource availability for plants, which are strong drivers of vegetation development and composition by changing relative competitive strengths. Conversely, microbial composition is strongly driven by vegetation composition. Therefore, the combination of micro- and macroecological knowledge is essential to understand the biogeochemical and biological key factors driving heterogeneity and total (i.e., micro-macro community composition at different spatial and temporal scales. As N and S inputs have drastically increased due to anthropogenic forcing and Fe inputs have decreased at a global scale, this combined approach has become even more urgent.
2. Effects of nitrogen fertilizer application and solar radiation on the growth response of sorghum [Sorghum bicolor] seedlings to soil moisture
International Nuclear Information System (INIS)
Sumi, A.; Katayama, T.C.
2000-01-01
The effects of nitrogen fertilizer application and solar radiation on the growth response to soil moisture were examined in sorghum seedlings grown in culture boxes. The effects of soil moisture (f) and amount of nitrogen fertilizer application (g) on the increment of total dry matter weight of sorghum seedling (ΔW) were represented satisfactorily by the following reciprocal equation, 1/ΔW = A/(f - f 0 ) + B(g + g 0 )/(f - f 0 ) + C/[(f - f 0 ) (g + g 0 )] + D/(g + g 0 ) + E, where f 0 and g 0 were the uppermost value of unavailable soil moisture and the amount of nitrogen supplied from soil and seeds. A, B, C, D and E were coefficients. The effects of soil moisture (f) and solar radiation (S) on ΔW were expressed approximately by the following reciprocal equation, 1/ΔW = A/(S - S 0 ) + B/(f - f 0 ) + C(f - f 0 ) + D, where S 0 was the daily compensation point. These results indicated that the effects of solar radiation and soil moisture are additive, but the interaction between soil moisture and nitrogen fertilizer is not negligible. The transpiration efficiency was unaffected by soil moisture, nitrogen fertilizer and solar radiation
3. Effect of nitrogen, potassium and lime on soil and manganese availability and uptake by bean
International Nuclear Information System (INIS)
Muraoka, T.; Nascimento Filho, V.F. do; Salvador, J.O.
1982-01-01
A pot experiment was conducted to assess the effect of nitrogen, potassium and lime on the availability of soil Zn and Mn and the absorption of these elements by bean (Phaseolus vulgaris, L.). The TE (Terra Roxa Estruturada) soil, used in this experiment, had been uniformily labelled with 65 Zn and 54 Mn and incubated prior to the seeding. The nitrogen favoured the absorption of manganese and zinc, tripling the manganese content in the plant and increasing by 2.5 fold the Zn content. The potassium also increased significantly the manganese uptake, but did not affect the zinc uptake. In the case of the Zn, however, the effect continued, though with less intensity. The lime alone reduced by almost 5 times the Mn content in the plant and by 50% the Zn content. Based on the results of the soil analysis (pH, CaCl 2 O.5M extractable Mn and EDTA + CaCl 2 extractable Zn) and on the 65 Zn and 54 Mn specific activities, it is suggested that the effets of nitrogen and potassium could be, partly, of synergic nature and that of the lime, due, also partly, to Ca-Mn and Ca-Zn antagonism in the plant. (Author) [pt
4. Smog nitrogen and the rapid acidification of forest soil, San Bernardino Mountains, southern California.
Science.gov (United States)
Wood, Yvonne A; Fenn, Mark; Meixner, Thomas; Shouse, Peter J; Breiner, Joan; Allen, Edith; Wu, Laosheng
2007-03-21
We report the rapid acidification of forest soils in the San Bernardino Mountains of southern California. After 30 years, soil to a depth of 25 cm has decreased from a pH (measured in 0.01 M CaCl2) of 4.8 to 3.1. At the 50-cm depth, it has changed from a pH of 4.8 to 4.2. We attribute this rapid change in soil reactivity to very high rates of anthropogenic atmospheric nitrogen (N) added to the soil surface (72 kg ha(-1) year(-1)) from wet, dry, and fog deposition under a Mediterranean climate. Our research suggests that a soil textural discontinuity, related to a buried ancient landsurface, contributes to this rapid acidification by controlling the spatial and temporal movement of precipitation into the landsurface. As a result, the depth to which dissolved anthropogenic N as nitrate (NO3) is leached early in the winter wet season is limited to within the top approximately 130 cm of soil where it accumulates and increases soil acidity.
5. Available nitrogen is the key factor influencing soil microbial functional gene diversity in tropical rainforest.
Science.gov (United States)
Cong, Jing; Liu, Xueduan; Lu, Hui; Xu, Han; Li, Yide; Deng, Ye; Li, Diqiang; Zhang, Yuguang
2015-08-20
Tropical rainforests cover over 50% of all known plant and animal species and provide a variety of key resources and ecosystem services to humans, largely mediated by metabolic activities of soil microbial communities. A deep analysis of soil microbial communities and their roles in ecological processes would improve our understanding on biogeochemical elemental cycles. However, soil microbial functional gene diversity in tropical rainforests and causative factors remain unclear. GeoChip, contained almost all of the key functional genes related to biogeochemical cycles, could be used as a specific and sensitive tool for studying microbial gene diversity and metabolic potential. In this study, soil microbial functional gene diversity in tropical rainforest was analyzed by using GeoChip technology. Gene categories detected in the tropical rainforest soils were related to different biogeochemical processes, such as carbon (C), nitrogen (N) and phosphorus (P) cycling. The relative abundance of genes related to C and P cycling detected mostly derived from the cultured bacteria. C degradation gene categories for substrates ranging from labile C to recalcitrant C were all detected, and gene abundances involved in many recalcitrant C degradation gene categories were significantly (P rainforest. Soil available N could be the key factor in shaping the soil microbial functional gene structure and metabolic potential.
6. Smog Nitrogen and the Rapid Acidification of Forest Soil, San Bernardino Mountains, Southern California
Directory of Open Access Journals (Sweden)
Yvonne A. Wood
2007-01-01
Full Text Available We report the rapid acidification of forest soils in the San Bernardino Mountains of southern California. After 30 years, soil to a depth of 25 cm has decreased from a pH (measured in 0.01 M CaCl2 of 4.8 to 3.1. At the 50-cm depth, it has changed from a pH of 4.8 to 4.2. We attribute this rapid change in soil reactivity to very high rates of anthropogenic atmospheric nitrogen (N added to the soil surface (72 kg ha–1 year–1 from wet, dry, and fog deposition under a Mediterranean climate. Our research suggests that a soil textural discontinuity, related to a buried ancient landsurface, contributes to this rapid acidification by controlling the spatial and temporal movement of precipitation into the landsurface. As a result, the depth to which dissolved anthropogenic N as nitrate (NO3 is leached early in the winter wet season is limited to within the top ~130 cm of soil where it accumulates and increases soil acidity.
7. Nitrogen and phosphorus resorption in a neotropical rain forest of a nutrient-rich soil.
Science.gov (United States)
Martínez-Sánchez, José Luis
2005-01-01
In tropical forests with nutrient-rich soil tree's nutrient resorption from senesced leaves has not always been observed to be low. Perhaps this lack of consistence is partly owing to the nutrient resorption methods used. The aim of the study was to analyse N and P resorption proficiency from tropical rain forest trees in a nutrient-rich soil. It was hypothesised that trees would exhibit low nutrient resorption in a nutrient-rich soil. The soil concentrations of total N and extractable P, among other physical and chemical characteristics, were analysed in 30 samples in the soil surface (10 cm) of three undisturbed forest plots at 'Estaci6n de Biologia Los Tuxtlas' on the east coast of Mexico (18 degrees 34' - 18 degrees 36' N, 95 degrees 04' - 95 degrees 09' W). N and P resorption proficiency were determined from senescing leaves in 11 dominant tree species. Nitrogen was analysed by microkjeldahl digestion with sulphuric acid and distilled with boric acid, and phosphorus was analysed by digestion with nitric acid and perchloric acid. Soil was rich in total N (0.50%, n = 30) and extractable P (4.11 microg g(-1) n = 30). As expected, trees showed incomplete N (1.13%, n = 11) and P (0.11%, n = 1) resorption. With a more accurate method of nutrient resorption assessment, it is possible to prove that a forest community with a nutrient-rich soil can have low levels of N and P resorption.
8. Below the disappearing marshes of an urban estuary: historic nitrogen trends and soil structure
Science.gov (United States)
Wigand, Cathleen; Roman, Charles T.; Davey, Earl; Stolt, Mark; Johnson, Roxanne; Hanson, Alana; Watson, Elizabeth B.; Moran, S. Bradley; Cahoon, Donald R.; Lynch, James C.; Rafferty, Patricia
2014-01-01
Marshes in the urban Jamaica Bay Estuary, New York, USA are disappearing at an average rate of 13 ha/yr, and multiple stressors (e.g., wastewater inputs, dredging activities, groundwater removal, and global warming) may be contributing to marsh losses. Among these stressors, wastewater nutrients are suspected to be an important contributing cause of marsh deterioration. We used census data, radiometric dating, stable nitrogen isotopes, and soil surveys to examine the temporal relationships between human population growth and soil nitrogen; and we evaluated soil structure with computer-aided tomography, surface elevation and sediment accretion trends, carbon dioxide emissions, and soil shear strength to examine differences among disappearing (Black Bank and Big Egg) and stable marshes (JoCo). Radiometric dating and nitrogen isotope analyses suggested a rapid increase in human wastewater nutrients beginning in the late 1840s, and a tapering off beginning in the 1930s when wastewater treatment plants (WWTPs) were first installed. Current WWTPs nutrient loads to Jamaica Bay are approximately 13 995 kg N/d and 2767 kg P/d. At Black Bank, the biomass and abundance of roots and rhizomes and percentage of organic matter on soil were significantly lower, rhizomes larger in diameter, carbon dioxide emission rates and peat particle density significantly greater, and soil strength significantly lower compared to the stable JoCo Marsh, suggesting Black Bank has elevated decomposition rates, more decomposed peat, and highly waterlogged peat. Despite these differences, the rates of accretion and surface elevation change were similar for both marshes, and the rates of elevation change approximated the long term relative rate of sea level rise estimated from tide gauge data at nearby Sandy Hook, New Jersey. We hypothesize that Black Bank marsh kept pace with sea level rise by the accretion of material on the marsh surface, and the maintenance of soil volume through production of
9. Mineralogical impact on long-term patterns of soil nitrogen and phosphorus enzyme activities
Science.gov (United States)
Mikutta, Robert; Turner, Stephanie; Meyer-Stüve, Sandra; Guggenberger, Georg; Dohrmann, Reiner; Schippers, Axel
2014-05-01
Soil chronosequences provide a unique opportunity to study microbial activity over time in mineralogical diverse soils of different ages. The main objective of this study was to test the effect of mineralogical properties, nutrient and organic matter availability over whole soil pro-files on the abundance and activity of the microbial communities. We focused on microbio-logical processes involved in nitrogen and phosphorus cycling at the 120,000-year Franz Josef soil chronosequence. Microbial abundances (microbial biomass and total cell counts) and enzyme activities (protease, urease, aminopeptidase, and phosphatase) were determined and related to nutrient contents and mineralogical soil properties. Both, microbial abundances and enzyme activities decreased with soil depth at all sites. In the organic layers, microbial biomass and the activities of N-hydrolyzing enzymes showed their maximum at the intermediate-aged sites, corresponding to a high aboveground biomass. In contrast, the phosphatase activity increased with site age. The activities of N-hydrolyzing enzymes were positively correlated with total carbon and nitrogen contents, whereas the phosphatase activity was negatively correlated with the phosphorus content. In the mineral soil, the enzyme activities were generally low, thus reflecting the presence of strongly sorbing minerals. Sub-strate-normalized enzyme activities correlated negatively to clay content as well as poorly crystalline Al and Fe oxyhydroxides, supporting the view that the evolution of reactive sec-ondary mineral phases alters the activity of the microbial communities by constraining sub-strate availability. Our data suggest a strong mineralogical influence on nutrient cycling par-ticularly in subsoil environments.
10. Recycling soil nitrate nitrogen by amending agricultural lands with oily food waste.
Science.gov (United States)
Rashid, M T; Voroney, R P
2003-01-01
With current agricultural practices the amounts of fertilizer N applied are frequently more than the amounts removed by the crop. Excessive N application may result in short-term accumulation of nitrate nitrogen (NO3-N) in soil, which can easily be leached from the root zone and into the ground water. A management practice suggested for conserving accumulated NO3-N is the application of oily food waste (FOG; fat + oil + greases) to agricultural soils. A two-year field study (1995-1996 and 1996-1997) was conducted at Elora Research Center (43 degrees 38' N, 80 degrees W; 346 m above mean sea level), University of Guelph, Ontario, Canada to determine the effect of FOG application in fall and spring on soil NO3-N contents and apparent N immobilization-mineralization of soil N in the 0- to 60-cm soil layer. The experiment was planned under a randomized complete block design with four replications. An unamended control and a reference treatment [winter wheat (Triticum aestivum L.) cover crop] were included in the experiment to compare the effects of fall and spring treatment of oily food waste on soil NO3-N contents and apparent N immobilization-mineralization. Oily food waste application at 10 Mg ha(-1) in the fall decreased soil NO3-N by immobilization and conserved 47 to 56 kg NO3-N ha(-1), which would otherwise be subject to leaching. Nitrogen immobilized due to FOG application in the fall was subsequently remineralized by the time of fertilizer N sidedress, whereas no net mineralization was observed in spring-amended plots at the same time.
11. ORGANIC CARBON AND TOTAL NITROGEN IN THE DENSIMETRIC FRACTIONS OF ORGANIC MATTER UNDER DIFFERENT SOIL MANAGEMEN
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MARCELO RIBEIRO VILELA PRADO
2016-01-01
Full Text Available The evaluation of land use and management by the measurement of soil organic matter and its fractions has gained attention since it helps in the understanding of the dynamics of their contribution to soil productivity, especially in tropical environments. This study was conducted in the municipality of Colorado do Oeste, state of Rondônia, Brazil and its aim was to determinethe quantity of organic carbon and total nitrogen in the light and heavy fractions of organic matter in the surface layers of a typic hapludalf under different land use systems: Native Forest: open evergreen forest, reference environment; Agroforestry System 1: teak (Tectona grandis LF and kudzu (Pueraria montana; Agroforestry System 2: coffee (Coffea canephora, marandu palisade grass (Brachiaria brizantha cv. Marandu, “pinho cuiabano” (Parkia multijuga, teak and kudzu.; Agroforestry System 3: teak and cocoa (Theobroma cacao; Silvopasture System: teak, cocoa and marandu palisade grass; and Extensive Grazing System: marandu palisade grass. The experimental design was a randomized block in split-split plots (use systems versus soil layers of 0-0.05 and 0.05-0.10 m with three replications. The results showed that relative to Native Forest, the Agroforestry System 2 had equal- and greater amounts of organic carbon and total nitrogen respectively (light and heavy fractions in the soil organic matter, with the light fraction being responsible for storage of approximately 45% and 70% of the organic carbon and total nitrogen, respectively. Therefore, the light densimetric fraction proved to be useful in the early identification of the general decline of the soil organic matter in the land use systems evaluated.
12. Impact of elevated precipitation, nitrogen deposition and warming on soil respiration in a temperate desert
Science.gov (United States)
Yue, Ping; Cui, Xiaoqing; Gong, Yanming; Li, Kaihui; Goulding, Keith; Liu, Xuejun
2018-04-01
Soil respiration (Rs) is the most important source of carbon dioxide emissions from soil to atmosphere. However, it is unclear what the interactive response of Rs would be to environmental changes such as elevated precipitation, nitrogen (N) deposition and warming, especially in unique temperate desert ecosystems. To investigate this an in situ field experiment was conducted in the Gurbantunggut Desert, northwest China, from September 2014 to October 2016. The results showed that precipitation and N deposition significantly increased Rs, but warming decreased Rs, except in extreme precipitation events, which was mainly through its impact on the variation of soil moisture at 5 cm depth. In addition, the interactive response of Rs to combinations of the factors was much less than that of any single-factor, and the main response was a positive effect, except for the response from the interaction of increased precipitation and high N deposition (60 kg N ha-1 yr-1). Although Rs was found to show a unimodal change pattern with the variation of soil moisture, soil temperature and soil NH4+-N content, and it was significantly positively correlated to soil dissolved organic carbon (DOC) and pH, a structural equation model found that soil temperature was the most important controlling factor. Those results indicated that Rs was mainly interactively controlled by the soil multi-environmental factors and soil nutrients, and was very sensitive to elevated precipitation, N deposition and warming. However, the interactions of multiple factors largely reduced between-year variation of Rs more than any single-factor, suggesting that the carbon cycle in temperate deserts could be profoundly influenced by positive carbon-climate feedback.
13. Farm, land, and soil nitrogen budgets for agriculture in Europe calculated with CAPRI
International Nuclear Information System (INIS)
Leip, Adrian; Britz, Wolfgang; Weiss, Franz; Vries, Wim de
2011-01-01
We calculated farm, land, and soil N-budgets for countries in Europe and the EU27 as a whole using the agro-economic model CAPRI. For EU27, N-surplus is 55 kg N ha -1 yr -1 in a soil budget and 65 kg N 2 O-N ha -1 yr -1 and 67 kg N ha -1 yr -1 in land and farm budgets, respectively. NUE is 31% for the farm budget, 60% for the land budget and 63% for the soil budget. NS values are mainly related to the excretion (farm budget) and application (soil and land budget) of manure per hectare of total agricultural land. On the other hand, NUE is best explained by the specialization of the agricultural system toward animal production (farm NUE) or the share of imported feedstuff (soil NUE). Total N input, intensive farming, and the specialization to animal production are found to be the main drivers for a high NS and low NUE. - Highlights: → Farm, land and soil N-budgets are important tools to characterize agricultural systems. → Farm N Use Efficiency (NUE) is lower than soil NUE; farm nitrogen surplus is higher. → On EU27 average, farm NUE is 31%, soil NUE is 63%, N surplus is 55-67 kg N ha -1 yr -1 . → Soil NUE is best explained by the share of imported feedstuff. → Intensive farming and specialization to animal production cause a high NS and low NUE. - Consistent calculations of farm, land and soil N-budgets for agriculture in Europe are presented and discussed at the national level and for EU27.
14. Soil Microbial Responses to Elevated CO2 and O3 in a Nitrogen-Aggrading Agroecosystem
Science.gov (United States)
Cheng, Lei; Booker, Fitzgerald L.; Burkey, Kent O.; Tu, Cong; Shew, H. David; Rufty, Thomas W.; Fiscus, Edwin L.; Deforest, Jared L.; Hu, Shuijin
2011-01-01
Climate change factors such as elevated atmospheric carbon dioxide (CO2) and ozone (O3) can exert significant impacts on soil microbes and the ecosystem level processes they mediate. However, the underlying mechanisms by which soil microbes respond to these environmental changes remain poorly understood. The prevailing hypothesis, which states that CO2- or O3-induced changes in carbon (C) availability dominate microbial responses, is primarily based on results from nitrogen (N)-limiting forests and grasslands. It remains largely unexplored how soil microbes respond to elevated CO2 and O3 in N-rich or N-aggrading systems, which severely hinders our ability to predict the long-term soil C dynamics in agroecosystems. Using a long-term field study conducted in a no-till wheat-soybean rotation system with open-top chambers, we showed that elevated CO2 but not O3 had a potent influence on soil microbes. Elevated CO2 (1.5×ambient) significantly increased, while O3 (1.4×ambient) reduced, aboveground (and presumably belowground) plant residue C and N inputs to soil. However, only elevated CO2 significantly affected soil microbial biomass, activities (namely heterotrophic respiration) and community composition. The enhancement of microbial biomass and activities by elevated CO2 largely occurred in the third and fourth years of the experiment and coincided with increased soil N availability, likely due to CO2-stimulation of symbiotic N2 fixation in soybean. Fungal biomass and the fungi∶bacteria ratio decreased under both ambient and elevated CO2 by the third year and also coincided with increased soil N availability; but they were significantly higher under elevated than ambient CO2. These results suggest that more attention should be directed towards assessing the impact of N availability on microbial activities and decomposition in projections of soil organic C balance in N-rich systems under future CO2 scenarios. PMID:21731722
15. Characterization of free nitrogen fixing bacteria of the genus Azotobacter in organic vegetable-grown Colombian soils
NARCIS (Netherlands)
Jiménez Avella, Diego; Montaña, José Salvador; Martínez, María Mercedes
With the purpose of isolating and characterizing free nitrogen fixing bacteria (FNFB) of the genus Azotobacter, soil samples were collected randomly from different vegetable organic cultures with neutral pH in different zones of Boyacá-Colombia. Isolations were done in selective free nitrogen
16. Forest calcium depletion and biotic retention along a soil nitrogen gradient
Science.gov (United States)
Perakis, Steven S.; Sinkhorn, Emily R.; Catricala, Christina; Bullen, Thomas D.; Fitzpatrick, John A.; Hynicka, Justin D.; Cromack, Kermit
2013-01-01
High nitrogen (N) accumulation in terrestrial ecosystems can shift patterns of nutrient limitation and deficiency beyond N toward other nutrients, most notably phosphorus (P) and base cations (calcium [Ca], magnesium [Mg], and potassium [K]). We examined how naturally high N accumulation from a legacy of symbiotic N fixation shaped P and base cation cycling across a gradient of nine temperate conifer forests in the Oregon Coast Range. We were particularly interested in whether long-term legacies of symbiotic N fixation promoted coupled N and organic P accumulation in soils, and whether biotic demands by non-fixing vegetation could conserve ecosystem base cations as N accumulated. Total soil N (0–100 cm) pools increased nearly threefold across the N gradient, leading to increased nitrate leaching, declines in soil pH from 5.8 to 4.2, 10-fold declines in soil exchangeable Ca, Mg, and K, and increased mobilization of aluminum. These results suggest that long-term N enrichment had acidified soils and depleted much of the readily weatherable base cation pool. Soil organic P increased with both soil N and C across the gradient, but soil inorganic P, biomass P, and P leaching loss did not vary with N, implying that historic symbiotic N fixation promoted soil organic P accumulation and P sufficiency for non-fixers. Even though soil pools of Ca, Mg, and K all declined as soil N increased, only Ca declined in biomass pools, suggesting the emergence of Ca deficiency at high N. Biotic conservation and tight recycling of Ca increased in response to whole-ecosystem Ca depletion, as indicated by preferential accumulation of Ca in biomass and surface soil. Our findings support a hierarchical model of coupled N–Ca cycling under long-term soil N enrichment, whereby ecosystem-level N saturation and nitrate leaching deplete readily available soil Ca, stimulating biotic Ca conservation as overall supply diminishes. We conclude that a legacy of biological N fixation can increase N
17. Nitrogen fertilization has a stronger effect on soil nitrogen-fixing bacterial communities than elevated atmospheric CO2.
Science.gov (United States)
Berthrong, Sean T; Yeager, Chris M; Gallegos-Graves, Laverne; Steven, Blaire; Eichorst, Stephanie A; Jackson, Robert B; Kuske, Cheryl R
2014-05-01
Biological nitrogen fixation is the primary supply of N to most ecosystems, yet there is considerable uncertainty about how N-fixing bacteria will respond to global change factors such as increasing atmospheric CO2 and N deposition. Using the nifH gene as a molecular marker, we studied how the community structure of N-fixing soil bacteria from temperate pine, aspen, and sweet gum stands and a brackish tidal marsh responded to multiyear elevated CO2 conditions. We also examined how N availability, specifically, N fertilization, interacted with elevated CO2 to affect these communities in the temperate pine forest. Based on data from Sanger sequencing and quantitative PCR, the soil nifH composition in the three forest systems was dominated by species in the Geobacteraceae and, to a lesser extent, Alphaproteobacteria. The N-fixing-bacterial-community structure was subtly altered after 10 or more years of elevated atmospheric CO2, and the observed shifts differed in each biome. In the pine forest, N fertilization had a stronger effect on nifH community structure than elevated CO2 and suppressed the diversity and abundance of N-fixing bacteria under elevated atmospheric CO2 conditions. These results indicate that N-fixing bacteria have complex, interacting responses that will be important for understanding ecosystem productivity in a changing climate.
18. The method for determination of parameters of the phenomenological continual model of soil organic matter transformation
Directory of Open Access Journals (Sweden)
S. I. Bartsev
2015-06-01
Full Text Available A possible method for experimental determination of parameters of the previously proposed continual mathematical model of soil organic matter transformation is theoretically considered in this paper. The previously proposed by the authors continual model of soil organic matter transformation, based on using the rate of matter transformation as a continual scale of its recalcitrance, describes the transformation process phenomenologically without going into detail of microbiological mechanisms of transformation. Thereby simplicity of the model is achieved. The model is represented in form of one differential equation in firstorder partial derivatives, which has an analytical solution in elementary functions. The model equation contains a small number of empirical parameters which generally characterize environmental conditions where the matter transformation process occurs and initial properties of the plant litter. Given the values of these parameters, it is possible to calculate dynamics of soil organic matter stocks and its distribution over transformation rate. In the present study, possible approaches for determination of the model parameters are considered and a simple method of their experimental measurement is proposed. An experiment of an incubation of chemically homogeneous samples in soil and multiple sequential measurement of the sample mass loss with time is proposed. An equation of time dynamics of mass loss of incubated homogeneous sample is derived from the basic assumption of the presented soil organic matter transformation model. Thus, fitting by the least squares method the parameters of sample mass loss curve calculated according the proposed mass loss dynamics equation allows to determine the parameters of the general equation of soil organic transformation model.
19. Soil properties and not inputs control carbon : nitrogen : phosphorus ratios in cropped soils in the long term
Science.gov (United States)
Frossard, Emmanuel; Buchmann, Nina; Bünemann, Else K.; Kiba, Delwende I.; Lompo, François; Oberson, Astrid; Tamburini, Federica; Traoré, Ouakoltio Y. A.
2016-02-01
Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies have explicitly considered the effects of agricultural management practices on the soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long term. Thus, we analysed the C, N, and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK (bio-Dynamic, bio-Organic, and "Konventionell") cropping system trial (Switzerland). In each of these trials, there was a large range of C, N, and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P, and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure, and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at
20. Soil nitrogen dynamics within profiles of a managed moist temperate forest chronosequence consistent with long-term harvesting-induced losses
Science.gov (United States)
Kellman, Lisa; Kumar, Sanjeev; Diochon, Amanda
2014-07-01
This study investigates whether clear-cut forest harvesting leads to alterations in the decadal-scale biogeochemical nitrogen (N) cycles of moist temperate forest ecosystems. Using a harvested temperate red spruce (Picea rubens Sarg.) forest chronosequence in Nova Scotia, Canada, representing 80 year old postharvest conditions, alongside a reference old-growth (125+ year old) site with no documented history of disturbance, we examine harvesting-related changes in soil N pools and fluxes. Specifically, we quantify soil N storage with depth and age across the forest chronosequence, examine changes in physical fractions and δ15N of soil N through depth and time, and quantify gross soil N transformation rates through depth and time using a 15N isotope dilution technique. Our findings point to a large loss of total N in the soil pool, particularly within the deep soil (>20 cm) and organomineral fractions. A pulse of available mineralized N (as ammonium) was observed following harvesting (mean residence time (MRT) > 6 days), but its MRT dropped to estimates that suggest soil N may not reaccrue for almost a century following this disturbance.
1. Soil Fauna Alter the Effects of Litter Composition on Nitrogen Cycling in a Mineral Soil
Science.gov (United States)
Plant chemical composition and the soil community are known to influence litter and soil organic matter decomposition. Although these two factors are likely to interact, their mechanisms and outcomes of interaction are not well understood. Studies of their interactive effects are...
2. Crop residue decomposition, residual soil organic matter and nitrogen mineralization in arable soils with contrasting textures
NARCIS (Netherlands)
Matus, F.J.
1994-01-01
To evaluate the significance of cropping, soil texture and soil structure for the decomposition of 14C- and 15N-labelled crop residues, a study was conducted in a sand and a
3. The use of N{sup 15} for studying the mechanism of transformation in the soil and plant
Energy Technology Data Exchange (ETDEWEB)
Alchater, M S [King Faisal University - Faculty of Agriculture and Food Science - Department of Soil and Water Al-Hassa, (Saudi Arabia)
1995-10-01
This research pertains to the study of the mechanism of transformation of added N 15 in the soil and plant in an attempt to determine the competition between microbial biomass and the plant for the use of N fertilizer in the form of (N 15 H 4)2 So 4. Additional amounts of barley straw were added as a source of energy. The study led to determining the real utilization coefficient of the canopy and the root system which amounted to 79% of N 15 added alone. Whereas it amounted to the treatments in which barley straw was added to N 15. Furthermore, there was a decrease in the amount of organic N 15 in the form of Gamma-amine as compared with other forms of organic N which also decreased to lesser degree. The results also indicated that the important N in the immobilization of nitrogen, as observed in previous field trials. Nitrogen balance and the contribution of soil N to plant nutrition were also calculated. 2 figs., 5 tabs.
4. [Ecological stoichiometry of soil carbon, nitrogen and phosphorus within soil aggregates in tea plantations with different ages].
Science.gov (United States)
Li, Wei; Zheng, Zi-cheng; Li, Ting-xuan
2015-01-01
This study selected 4 tea plantations with different ages (12-15, 20-22, 30-33 and >50 year-old) located in Ya' an, Sichuan Province, China to investigate the distribution patterns of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) , and to examine the ecological stoichiometric characteristics of C, N and P within soil aggregates. The results showed that the coefficients of variation of SOC, TN and TP were 17.5%, 16.3% and 9.4%, respectively in the 0-20 cm soil layer and were 24.0%, 21.0% and 9.2%, respectively in the 20-40 cm soil layer. The spatial variation of TP was lower than that of SOC and TN but there were significant positive correlations among them. SOC and TN were distributed in the small-size aggregates and both of them had the greatest values in the >50 year-old tea plantation, however, the distribution of TP was relatively uniform among aggregates and ages. The coefficients of variation of C/N, C/P, and N/P were 9.4%, 14.0% and 14.9%, respectively in the 0-20 cm soil layer and were 7.4%, 24.9% and 21.8%, respectively in the 20-40 cm soil layer. Variation of C/N was lower than that of C/P and N/P. Averaged C/P and N/P values in the small-size aggregates were higher than in aggregates of other sizes, and the maximum values were in the >50 year-old plantation. C/N, C/P and N/P had good indication for soil organic carbon storage.
5. Evaluation of wastewater nitrogen transformation in a natural wetland (Ulaanbaatar, Mongolia) using dual-isotope analysis of nitrate
International Nuclear Information System (INIS)
Itoh, Masayuki; Takemon, Yasuhiro; Makabe, Akiko; Yoshimizu, Chikage; Kohzu, Ayato; Ohte, Nobuhito; Tumurskh, Dashzeveg; Tayasu, Ichiro; Yoshida, Naohiro; Nagata, Toshi
2011-01-01
The Tuul River, which provides water for the daily needs of many residents of Ulaanbaatar, Mongolia, has been increasingly polluted by wastewater from the city's sewage treatment plant. Information on water movement and the transformation of water-borne materials is required to alleviate the deterioration of water quality. We conducted a synoptic survey of general water movement, water quality including inorganic nitrogen concentrations, and isotopic composition of nitrogen (δ 15 N-NO 3 - , δ 18 O-NO 3 - , and δ 15 N-NH 4 + ) and water (δ 18 O-H 2 O) in a wetland area that receives wastewater before it enters the Tuul River. We sampled surface water, groundwater, and spring water along the two major water routes in the wetland that flow from the drain of the sewage treatment plant to the Tuul River: a continuous tributary and a discontinuous tributary. The continuous tributary had high ammonium (NH 4 + ) concentrations and nearly stable δ 15 N-NH 4 + , δ 15 N-NO 3 - , and δ 18 O-NO 3 - concentrations throughout its length, indicating that nitrogen transformation (i.e., nitrification and denitrification) during transit was small. In contrast, NH 4 + concentrations decreased along the discontinuous tributary and nitrate (NO 3 - ) concentrations were low at many points. Values of δ 15 N-NH 4 + , δ 15 N-NO 3 - , and δ 18 O-NO 3 - increased with flow along the discontinuous route. Our results indicate that nitrification and denitrification contribute to nitrogen removal in the wetland area along the discontinuous tributary with slow water transport. Differences in hydrological pathways and the velocity of wastewater transport through the wetland area greatly affect the extent of nitrogen removal. - Research Highlights: → Dual-isotope analysis of nitrate was used to assess wastewater nitrogen status. → Wetland that receives the wastewater contributed to nitrogen removal. → Differences in hydrological pathways greatly affect the extent of nitrogen removal.
6. Nitrogen dynamics in soils cultivated with maize and fertilized with pig slurry
Directory of Open Access Journals (Sweden)
Maria Emília Borges Alves
2012-04-01
Full Text Available The proper disposal of pig manure is of great importance because, when mishandled, it can contaminate water resources. This study aimed to evaluate the nitrogen dynamics in a Cerrado Oxisol and its absorption, over time, by a maize crop managed with pig slurry associated with mineral fertilization (N P K. The study was conducted at a private farm, in the region of Sete Lagoas, Minas Gerais, Brazil. The maize crop was able to recover 62% of the mineral nitrogen that entered the soil-plant system, while 9% leached as nitrate and, to a lesser amount, as ammonium. The maximum average content of nitrate and ammonium of 92 kg ha-1 and 43 kg ha-1, respectively, was observed in the 0 to 0.3 m soil layer during the early crop development stage. A minimum content of 5.8 kg ha-1 of nitrate and 9.0 kg ha-1 of ammonium, respectively, was measured at the end of the cycle. In addition, the nitrate content at that soil layer, at the end of the maize cycle, remained below the values measured at the native Cerrado, indicating that the agricultural use of the land poses no additional risk to the nitrate accumulation and leaching into the soil profile.
7. Higher molecular weight dissolved organic nitrogen turnover as affected by soil management history
DEFF Research Database (Denmark)
Lønne Enggrob, Kirsten
of different management histories on the turnover of high Mw DON. Further, we distinguished between several classes of high Mw DON, i.e., 1-10 kDa and >10 kDa. 3. Materials and methods With the use of micro-lysimeters, the turnover of triple-labeled (15N, 14C and 13C) high Mw DON was studied in a sandy soil......High molecular weight dissolved organic nitrogen turnover as affected by soil management history *Kirsten Lønne Enggrob,1 Lars Elsgaard,1 and Jim Rasmussen1 1Aarhus University, Dept. of Agroecology, Foulum, Denmark 1. Introduction Dissolved organic nitrogen (DON) play an important role in soil N...... are presented for 14CO2 evolution during 14 days of incubation. 4. Results and conclusion Results showed that the turnover rate of high Mw DON was dependent on both the Mw size of DON and on the soil liming history. Evidence showing where in the DON Mw sizes the bottleneck lies will be presented....
8. The analysis of soil cores polluted with certain metals using the Box-Cox transformation.
Science.gov (United States)
Meloun, Milan; Sánka, Milan; Nemec, Pavel; Krítková, Sona; Kupka, Karel
2005-09-01
To define the soil properties for a given area or country including the level of pollution, soil survey and inventory programs are essential tools. Soil data transformations enable the expression of the original data on a new scale, more suitable for data analysis. In the computer-aided interactive analysis of large data files of soil characteristics containing outliers, the diagnostic plots of the exploratory data analysis (EDA) often find that the sample distribution is systematically skewed or reject sample homogeneity. Under such circumstances the original data should be transformed. The Box-Cox transformation improves sample symmetry and stabilizes spread. The logarithmic plot of a profile likelihood function enables the optimum transformation parameter to be found. Here, a proposed procedure for data transformation in univariate data analysis is illustrated on a determination of cadmium content in the plough zone of agricultural soils. A typical soil pollution survey concerns the determination of the elements Be (16 544 values available), Cd (40 317 values), Co (22 176 values), Cr (40 318 values), Hg (32 344 values), Ni (34 989 values), Pb (40 344 values), V (20 373 values) and Zn (36 123 values) in large samples.
9. The influence of wildfire severity on soil char composition and nitrogen dynamics
Science.gov (United States)
Rhoades, Charles; Fegel, Timothy; Chow, Alex; Tsai, Kuo-Pei; Norman, John, III; Kelly, Eugene
2017-04-01
Forest fires cause lasting ecological changes and alter the biogeochemical processes that control stream water quality. Decreased plant nutrient uptake is the mechanism often held responsible for lasting post-fire shifts in nutrient supply and demand, though other upland and in-stream factors also likely contribute to elevated stream nutrient losses. Soil heating, for example, creates pyrogenic carbon (C) and char layers that influence C and nitrogen (N) cycling. Char layer composition and persistence vary across burned landscapes and are influenced first by fire behavior through the temperature and duration of combustion and then by post-fire erosion. To evaluate the link between soil char and stream C and N export we studied areas burned by the 2002 Hayman Fire, the largest wildfire in Colorado, USA history. We compared soil C and N pools and processes across ecotones that included 1) unburned forests, 2) areas with moderate and 3) high wildfire severity. We analyzed 1-2 cm thick charred organic layers that remain visible 15 years after the fire, underlying mineral soils, and soluble leachate from both layers. Unburned soils released more dissolved organic C and N (DOC and DON) from organic and mineral soil layers than burned soils. The composition of DOC leachate characterized by UV-fluorescence, emission-excitation matrices (EEMs) and Fluorescence Regional Integration (FRI) found similarity between burned and unburned soils, underscoring a common organic matter source. Humic and fulvic acid-like fractions, contained in regions V and III of the FRI model, comprised the majority of the fluorescing DOM in both unburned and char layers. Similarity between two EEMs indices (Fluorescence and Freshness), further denote that unburned soils and char layers originate from the same source and are consistent with visual evidence char layers contain significant amounts of unaltered OM. However, the EEMs humification index (HIX) and compositional analysis with pyrolysis GCMS
10. Atmospheric Nitrogen Deposition and the Properties of Soils in Forests of Vologda Region
Science.gov (United States)
Kudrevatykh, I. Yu.; Ivashchenko, K. V.; Ananyeva, N. D.; Ivanishcheva, E. A.
2018-02-01
Twenty plots (20 m2 each) were selected in coniferous and mixed forests of the industrial Vologda district and the Vytegra district without developed industries in Vologda region. In March, snow cores corresponding to the snow cover depth were taken on these plots. In August, soil samples from the 0- to 20-cm layer of litter-free soddy-podzolic soil (Albic Retisol (Ochric)) were taken on the same plots in August. The content of mineral nitrogen (Nmin), including its ammonium (NH+ 4) and nitrate (NO- 3) forms, was determined in the snow (meltwater) and soil. The contents of total organic carbon, total nitrogen, and elements (Al, Ca); pH; particle size distribution; and microbiological parameters―carbon of microbial biomass (Cmic) and microbial respiration (MR)―were determined in the soil. The ratio MR/Cmic = qCO2 (specific respiration of microbial biomass, or soil microbial metabolic quotient) was calculated. The content of Nmic in meltwater of two districts was 1.7 mg/L on the average (1.5 and 0.3 mg/L for the NH+ 4 and NO- 3 forms, respectively). The annual atmospheric deposition was 0.6-8.9 kg Nmin/ha, the value of which in the Vologda district was higher than in the Vytegra district by 40%. Reliable correlations were found between atmospheric NH+ 4 depositions and Cmic (-0.45), between NH+ 4 and qCO2 (0.56), between atmospheric NO- 3 depositions and the soil NO- 3 (-0.45), and between NO- 3 and qCO2 (-0.58). The content of atmospheric Nmin depositions correlated with the ratios C/N (-0.46) and Al/Ca (-0.52) in the soil. In forests with the high input of atmospheric nitrogen (>2.0 kg NH+ 4/(ha yr) and >6.4 kg Nmin/(ha yr)), a tendency of decreasing Cmic, C/N, and Al/Ca, as well as increasing qCO2, was revealed, which could be indicative of deterioration in the functioning of microbial community and the chemical properties of the soil.
11. Effects of Nitrogen and Water on Soil Enzyme Activity and Soil Microbial Biomass in Stipa baicalensis Steppe,Inner Mongolia of North China
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WANG Jie
2014-06-01
Full Text Available In this paper, eight nitrogen treatments were applied at 0 g·m -2(N0, 1.5 g·m -2(N15, 3.0 g·m -2(N30, 5.0 g·m -2(N50, 10.0 g·m -2(N100, 15.0 g·m -2(N150, 20.0 g·m -2(N200, 30.0 g·m -2(N300 as NH 4 NO 3 and adding water to simulate summer rainfall of 100 mm, the interactive experiment was set to explore the effects of nitrogen and water addition in Stipa baicalensis steppe on soil nutrients, enzyme activities and soil microbial biomass. The results showed that the nitrogen and water addition changed soil physico-chemical factors obviously, the content of soil total organic carbon, total nitrogen, nitrate nitrogen and ammonium nitrogen increased along with the increasing of application rate of nitrogen, on the contrary, the soil pH value had decreasing trend. Appropriate application of nitrogen could enhance the activity of urease and catalase but decreased the activity of polyphenol oxidase. Nitrogen and water addition had significant effect on soil microbial biomass C and N. Higher level of N fertilizer significantly reduced microbial biomass C, and the microbial biomass N was on the rise with the application rate of nitrogen. The addition of water could slow the inhibition of nitrogen to microorganism and increase the microbial biomass C and N. A closed relationship existed in soil nutrient, activities of soil enzyme and soil microbial biomass C and N. The significantly positive correlation existed between total N, organic C, nitrate N and catalase, significantly negative correlation between nitrate N, ammonium N, total N and polyphenol oxidase. Microbial biomass N was significantly positive correlated with total N, nitrate N, ammonium N, catalase, phosphatase, and was negative correlated with polyphenol oxidase. Microbial biomass C was significantly positive correlated with polyphenol oxidase, and was negative correlated with catalase.
12. Nutrient amendment does not increase mineralisation of sequestered carbon during incubation of a nitrogen limited mangrove soil
KAUST Repository
Keuskamp, Joost A.
2013-02-01
Mangrove forests are sites of intense carbon and nutrient cycling, which result in soil carbon sequestration on a global scale. Currently, mangrove forests receive increasing quantities of exogenous nutrients due to coastal development. The present paper quantifies the effects of nutrient loading on microbial growth rates and the mineralisation of soil organic carbon (SOC) in two mangrove soils contrasting in carbon content. An increase in SOC mineralisation rates would lead to the loss of historically sequestered carbon and an enhanced CO2 release from these mangrove soils.In an incubation experiment we enriched soils from Avicennia and Rhizophora mangrove forests bordering the Red Sea with different combinations of nitrogen, phosphorus and glucose to mimic the effects of wastewater influx. We measured microbial growth rates as well as carbon mineralisation rates in the natural situation and after enrichment. The results show that microbial growth is energy limited in both soils, with nitrogen as a secondary limitation. Nitrogen amendment increased the rate at which labile organic carbon was decomposed, while it decreased SOC mineralisation rates. Such an inhibitory effect on SOC mineralisation was not found for phosphorus enrichment.Our data confirm the negative effect of nitrogen enrichment on the mineralisation of recalcitrant carbon compounds found in other systems. Based on our results it is not to be expected that nutrient enrichment by itself will cause degradation of historically sequestered soil organic carbon in nitrogen limited mangrove forests. © 2012 Elsevier Ltd.
13. [Distribution characteristics and erosion risk of nitrogen and phosphorus in soils of Zhuangmu town in Lake Wabuhu basin].
Science.gov (United States)
Li, Ru-Zhong; Zou, Yang; Xu, Jing-Jing; Ding, Gui-Zhen
2014-03-01
To understand the loss risk of soil erosion in the Zhuangmu town in Lake Wabuhu watershed, concentration and spatial distribution of nitrogen and phosphorus in 162 surface soil samples collected from the farmlands in ten administrative villages of the town were investigated. The risk assessment was conducted by using the nitrogen and phosphorus index method after speciation analysis of soil nitrogen and phosphorus. Based on ArcGIS technology, the spatial interpolation of total nitrogen (TN), total phosphorus (TP), and bioavailable nitrogen and phosphorus contents as well as nitrogen and phosphorus index values were performed by means of Kriging interpolation. The results show that, generally, average contents of TN and TP were obtained at 1.67 g x kg(-1) and 0.71 g x kg(-1), respectively. And the mean concentration of bioavailable nitrogen and phosphorus were estimated at 0.26 g x kg(-1) and 0.33 g x kg(-1), accounting for 14.93% and 47.30% of TN and TP contents, respectively. Spatially, the samples with high concentration of TN were mostly from Houji, Yangwan and Liuqian villages, whereas the samples sites with higher contents of TP located in Houji, Yangwan and Zaolin villages. The mean values of nitrogen index (NI) and phosphorus index (PI) for the whole town are 2.11 and 2.13, respectively. According to the numeric size of NI and PI, ten villages ranged in the order of Yangwan > Zhuangmu > Xueqiao > Liuqian > Lizhuang > Jinqiao > Zaolin > Zhangwei > Houji > Xugang village. In general, the soil nitrogen loss is dominated by low and medium risks in the Zhuangmu town, and high risk sporadically appears in local area of the Yangwan village. Like the nitrogen, soil phosphorus loss risk also gives priority to low, and above medium risk concentrates in the Yangwan village as well.
14. Elevational Variation in Soil Amino Acid and Inorganic Nitrogen Concentrations in Taibai Mountain, China.
Directory of Open Access Journals (Sweden)
Xiaochuang Cao
Full Text Available Amino acids are important sources of soil organic nitrogen (N, which is essential for plant nutrition, but detailed information about which amino acids predominant and whether amino acid composition varies with elevation is lacking. In this study, we hypothesized that the concentrations of amino acids in soil would increase and their composition would vary along the elevational gradient of Taibai Mountain, as plant-derived organic matter accumulated and N mineralization and microbial immobilization of amino acids slowed with reduced soil temperature. Results showed that the concentrations of soil extractable total N, extractable organic N and amino acids significantly increased with elevation due to the accumulation of soil organic matter and the greater N content. Soil extractable organic N concentration was significantly greater than that of the extractable inorganic N (NO3--N + NH4+-N. On average, soil adsorbed amino acid concentration was approximately 5-fold greater than that of the free amino acids, which indicates that adsorbed amino acids extracted with the strong salt solution likely represent a potential source for the replenishment of free amino acids. We found no appreciable evidence to suggest that amino acids with simple molecular structure were dominant at low elevations, whereas amino acids with high molecular weight and complex aromatic structure dominated the high elevations. Across the elevational gradient, the amino acid pool was dominated by alanine, aspartic acid, glycine, glutamic acid, histidine, serine and threonine. These seven amino acids accounted for approximately 68.9% of the total hydrolyzable amino acid pool. The proportions of isoleucine, tyrosine and methionine varied with elevation, while soil major amino acid composition (including alanine, arginine, aspartic acid, glycine, histidine, leucine, phenylalanine, serine, threonine and valine did not vary appreciably with elevation (p>0.10. The compositional
15. Post-fire redistribution of soil carbon and nitrogen at a grassland-shrubland ecotone
Science.gov (United States)
Wang, Guan; Li, Junran; Ravi, Sujith; Dukes, David; Gonzales, Howell B.; Sankey, Joel B.
2018-01-01
The rapid conversion of grasslands into shrublands has been observed in many arid and semiarid regions worldwide. Studies have shown that fire can provide certain forms of reversibility for shrub-grass transition due to resource homogenization and shrub mortality, especially in the early stages of shrub encroachment. Field-level post-fire soil resource redistribution has rarely been tested. Here we used prescribed fire in a shrubland-grassland transition zone in the northern Chihuahuan Desert to test the hypothesis that fire facilitates the remobilization of nutrient-enriched soil from shrub microsites to grass and bare microsites and thereby reduces the spatial heterogeneity of soil resources. Results show that the shrub microsites had the lowest water content compared to grass and bare microsites after fire, even when rain events occurred. Significant differences of total soil carbon (TC) and total soil nitrogen (TN) among the three microsites disappeared one year after the fire. The spatial autocorrelation distance increased from 1~2 m, approximately the mean size of an individual shrub canopy, to over 5 m one year after the fire for TC and TN. Patches of high soil C and N decomposed one year after the prescribed fire. Overall, fire stimulates the transfer of soil C and N from shrub microsites to nutrient-depleted grass and bare microsites. Such a redistribution of soil C and N, coupled with the reduced soil water content under the shrub canopies, suggests that fire might influence the competition between shrubs and grasses, leading to a higher grass, compared to shrub, coverage in this ecotone.
16. Estimating annual soil carbon loss in agricultural peatland soils using a nitrogen budget approach.
Science.gov (United States)
Kirk, Emilie R; van Kessel, Chris; Horwath, William R; Linquist, Bruce A
2015-01-01
Around the world, peatland degradation and soil subsidence is occurring where these soils have been converted to agriculture. Since initial drainage in the mid-1800s, continuous farming of such soils in the California Sacramento-San Joaquin Delta (the Delta) has led to subsidence of up to 8 meters in places, primarily due to soil organic matter (SOM) oxidation and physical compaction. Rice (Oryza sativa) production has been proposed as an alternative cropping system to limit SOM oxidation. Preliminary research on these soils revealed high N uptake by rice in N fertilizer omission plots, which we hypothesized was the result of SOM oxidation releasing N. Testing this hypothesis, we developed a novel N budgeting approach to assess annual soil C and N loss based on plant N uptake and fallow season N mineralization. Through field experiments examining N dynamics during growing season and winter fallow periods, a complete annual N budget was developed. Soil C loss was calculated from SOM-N mineralization using the soil C:N ratio. Surface water and crop residue were negligible in the total N uptake budget (3 - 4 % combined). Shallow groundwater contributed 24 - 33 %, likely representing subsurface SOM-N mineralization. Assuming 6 and 25 kg N ha-1 from atmospheric deposition and biological N2 fixation, respectively, our results suggest 77 - 81 % of plant N uptake (129 - 149 kg N ha-1) was supplied by SOM mineralization. Considering a range of N uptake efficiency from 50 - 70 %, estimated net C loss ranged from 1149 - 2473 kg C ha-1. These findings suggest that rice systems, as currently managed, reduce the rate of C loss from organic delta soils relative to other agricultural practices.
17. Estimating annual soil carbon loss in agricultural peatland soils using a nitrogen budget approach.
Directory of Open Access Journals (Sweden)
Emilie R Kirk
Full Text Available Around the world, peatland degradation and soil subsidence is occurring where these soils have been converted to agriculture. Since initial drainage in the mid-1800s, continuous farming of such soils in the California Sacramento-San Joaquin Delta (the Delta has led to subsidence of up to 8 meters in places, primarily due to soil organic matter (SOM oxidation and physical compaction. Rice (Oryza sativa production has been proposed as an alternative cropping system to limit SOM oxidation. Preliminary research on these soils revealed high N uptake by rice in N fertilizer omission plots, which we hypothesized was the result of SOM oxidation releasing N. Testing this hypothesis, we developed a novel N budgeting approach to assess annual soil C and N loss based on plant N uptake and fallow season N mineralization. Through field experiments examining N dynamics during growing season and winter fallow periods, a complete annual N budget was developed. Soil C loss was calculated from SOM-N mineralization using the soil C:N ratio. Surface water and crop residue were negligible in the total N uptake budget (3 - 4 % combined. Shallow groundwater contributed 24 - 33 %, likely representing subsurface SOM-N mineralization. Assuming 6 and 25 kg N ha-1 from atmospheric deposition and biological N2 fixation, respectively, our results suggest 77 - 81 % of plant N uptake (129 - 149 kg N ha-1 was supplied by SOM mineralization. Considering a range of N uptake efficiency from 50 - 70 %, estimated net C loss ranged from 1149 - 2473 kg C ha-1. These findings suggest that rice systems, as currently managed, reduce the rate of C loss from organic delta soils relative to other agricultural practices.
18. Use of Nitrogen-15 Isotope Method in Soils and Ground Water to Determine Potential Nitrogen Sources Affecting a Municipal Water Supply in Kansas, USA
Science.gov (United States)
Townsend, M. A.; Macko, S. A.
2004-12-01
Nitrate-N concentrations have increased to greater than 10 mg/L in a municipal water supply in western Kansas from 1995 to 2002. A study was done by the Kansas Geological Survey using the nitrogen-15 natural abundance isotope method to determine potential sources for the increasing nitrate concentrations. Preliminary results of the isotope analyses on water samples suggest that animal waste and/or denitrification enrichment has affected the water supply. Soil samples from areas near the wells that were not treated with manure show a general increase of nitrogen-15 signature (+9 to +15 \\permil) to a depth of 5 m. Soils are silt loams with measurable carbonate (0.8 to 2 % by weight) in the profile, which may permit volatilization enrichment to occur in the soil profile. Wells in the area range from 11 to 20 m in alluvial deposits with depth to water at approximately 9 m). Nitrate-N values range from 8 to 26 mg/L. Nitrogen-15 values range from (+17 to +28 \\permil) with no obvious source of animal waste near the well sites. There are potential nearby long-term sources of animal waste - an abandoned sewage treatment plant and an agricultural testing farm. One well has a reducing chemistry with a nitrate value of 0.9 mg/L and a nitrogen-15 value of +17 \\permil suggesting that alluvial sediment variation also has an impact on the water quality in the study area. The other wells show values of nitrate and nitrogen-15 that are much greater than the associated soils. The use of nitrogen-15 alone permited limited evaluation of sources of nitrate to ground water particularly in areas with carbonate in the soils. Use of oxygen-18 on nitrate will permit the delineation of the processes affecting the nitrogen in the soil profile and determination of the probable sources and the processes that have affected the nitrogen in the ground water. Final results of the nitrogen-15 and oxygen-18 analyses will be presented.
19. Effects of organic matter removal and soil compaction on fifth-year mineral soil carbon and nitrogen contents for sites across the United States and Canada
Science.gov (United States)
Felipe G. Sanchez; Allan E. Tiarks; J. Marty Kranabetter; Deborah S. Page-Dumroese; Robert F. Powers; Paul T. Sanborn; William K. Chapman
2006-01-01
This study describes the main treatment effects of organic matter removal and compaction and a split-plot effect of competition control on mineral soil carbon (C) and nitrogen (N) pools. Treatment effects on soil C and N pools are discussed for 19 sites across five locations (British Columbia, Northern Rocky Mountains, Pacific Southwest, and Atlantic and Gulf coasts)...
20. [Accumulation of soil organic carbon and total nitrogen in Pinus yunnanensis forests at different age stages].
Science.gov (United States)
Miao, Juan; Zhou, Chuan-Yan; Li, Shi-Jie; Yan, Jun-Hua
2014-03-01
Taking three Pinus yunnanensis forests at different ages (19, 28 and 45 a) in Panxian County of Guizhou Province as test objects, we investigated vertical distributions and accumulation rates of soil organic carbon (SOC) and total nitrogen (TN), as well as their relationships with soil bulk density. For the three forests at different age stages, SOC and TN changed consistently along the soil profile, declining with the soil depth. Both SOC and TN storage increased with the forest age. The SOC and TN storage amounts were 96.24, 121.65 and 148.13 t x hm(-2), and 10.76, 12.96 and 13.08 t x hm(-2) for the forest stands with 19 a, 28 a and 45 a, respectively. SOC had a significant positive correlation with soil TN, while both of them had a significant negative relationship with the soil bulk density. The accumulation rates of both SOC and TN storage at different growth periods were different, and the rate in the period from age 19 to 28 was higher than in the period from age 28 to 45.
1. Understanding spatial heterogeneity in soil carbon and nitrogen cycling in regenerating tropical dry forests
Science.gov (United States)
Waring, B. G.; Powers, J. S.; Branco, S.; Adams, R.; Schilling, E.
2015-12-01
Tropical dry forests (TDFs) currently store significant amounts of carbon in their biomass and soils, but these highly seasonal ecosystems may be uniquely sensitive to altered climates. The ability to quantitatively predict C cycling in TDFs under global change is constrained by tremendous spatial heterogeneity in soil parent material, land-use history, and plant community composition. To explore this variation, we examined soil carbon and nitrogen dynamics in 18 permanent plots spanning orthogonal gradients of stand age and soil fertility. Soil C and N pools, microbial biomass, and microbial extracellular enzyme activities were most variable at small (m2) spatial scales. However, the ratio of organic vs. inorganic N cycling was consistently higher in forest stands dominated by slow-growing, evergreen trees that associate with ectomycorrhizal fungi. Similarly, although bulk litter stocks and turnover rates varied greatly among plots, litter decomposition tended to be slower in ectomycorrhizae-dominated stands. Soil N cycling tended to be more conservative in older plots, although the relationship between stand age and element cycling was weak. Our results emphasize that microscale processes, particularly interactions between mycorrhizal fungi and free-living decomposers, are important controls on ecosystem-scale element cycling.
2. Soil Minerals: AN Overlooked Mediator of Plant-Microbe Competition for Organic Nitrogen in the Rhizosphere
Science.gov (United States)
Grandy, S.; Jilling, A.; Keiluweit, M.
2016-12-01
Recent research on the rate limiting steps in soil nitrogen (N) availability have shifted in focus from mineralization to soil organic matter (SOM) depolymerization. To that end, Schimel and Bennett (2004) argued that together with enzymatic breakdown of polymers to monomers, microsite processes and plant-microbial competition collectively drive N cycling. Here we present new conceptual models arguing that while depolymerization is a critical first step, mineral-organic associations may ultimately regulate the provisioning of bioavailable organic N, especially in the rhizosphere. Mineral-associated organic matter (MAOM) is a rich reservoir for N in soils and often holds 5-7x more N than particulate or labile fractions. However, MAOM is considered largely unavailable to plants as a source of N due to the physicochemical forces on mineral surfaces that stabilize organic matter. We argue that in rhizosphere hotspots, MAOM is in fact a potentially mineralizable and important source of nitrogen for plants. Several biochemical strategies enable plants and microbes to compete with mineral-organic interactions and effectively access MAOM. In particular, root-deposited low molecular weight compounds in the form of root exudates facilitate the biotic and abiotic destabilization and subsequent bioavailability of MAOM. We believe that the competitive balance between the potential fates of assimilable organic N — bound to mineral surfaces or dissolved and available for assimilation — depends on the specific interaction between and properties of the clay, soil solution, mineral-bound organic matter, and microbial community. For this reason, the plant-soil-MAOM interplay is enhanced in rhizosphere hotspots relative to non-rhizosphere environments, and likely strongly regulates plant-microbe competition for N. If these hypotheses are true, we need to reconsider potential soil N cycle responses to changes in climate and land use intensity, focusing on the processes by which
3. Effects of phosphorus and nitrogen additions on tropical soil microbial activity in the context of experimental warming
Science.gov (United States)
Foley, M.; Nottingham, A.; Turner, B. L.
2017-12-01
Soil warming is generally predicted to increase microbial mineralization rates and accelerate soil C losses which could establish a positive feedback to climatic warming. Tropical rain forests account for a third of global soil C, yet the responseto of tropical soil C a warming climate remains poorly understood. Despite predictions of soil C losses, decomposition of soil organic matter (SOM) in tropical soils may be constrained by several factors including microbial nutrient deficiencies. We performed an incubation experiment in conjunction with an in-situ soil warming experiment in a lowland tropical forest on Barro Colorado Island, Panama, to measure microbial response to two key nutrient additions in shallow (0-10cm) and deep (50-100 cm) soils. We compared the response of lowland tropical soils to montane tropical soils, predicting that lowland soils would display the strongest response to phosphorus additions. Soils were treated with either carbon alone (C), nitrogen (CN), phosphorus (CP) or nitrogen and phosphorus combined (CNP). Carbon dioxide (CO2) production was measured by NaOH capture and titrimetric analysis for 10 days. Cumulative CO2 production in montane soils increased significantly with all additions, suggesting these soils are characterized by a general microbial nutrient deficiency. The cumulative amount of C respired in deep soils from the lowland site increased significantly with CP and CNP additions, suggesting that microbial processes in deep lowland tropical soils are phosphorus-limited. These results support the current understanding that lowland tropical forests are growing on highly weathered, phosphorus-deplete soils, and provide novel insight that deep tropical SOM may be stabilized by a lack of biologically-available phosphorus. Further, this data suggests tropical soil C losses under elevated temperature may be limited by a strong microbial phosphorus deficiency.
4. Fire Frequency and Vegetation Composition Influence Soil Nitrogen Cycling and Base Cations in an Oak Savanna Ecosystem
Science.gov (United States)
McLauchlan, K. K.; Nelson, D. M.; Perakis, S.; Marcotte, A. L.
2017-12-01
Fire frequency is crucial for maintaining savannas in the transition between forests and grasslands. In general, increasing fire frequency has two effects: it increases herbaceous plant cover more than woody plant cover, and it lowers soil organic matter stocks. These effects have been demonstrated at a long-term prescribed fire experiment in an oak savanna ecosystem at Cedar Creek Ecosystem Science Reserve, Minnesota, U.S.A. The fire experiment began in 1964 and oak savannas are burned at various frequencies ranging from every year to not at all. This has led to changes in vegetation ranging from almost 100% grassland to 100% oak forest. Additionally, nitrogen stocks almost doubled in the sites that were not burned, as it accumulated in the trees, leaf litter, and soil. We addressed additional soil changes taking place at this experiment by asking the question: How have fire and oak-grass balance affected soil nutrients, specifically nitrogen and base cations? Surface soils were collected from 12 plots on the oak savanna burn experiment. Soils were collected in increments to 100 cm depth, from under grass-dominated vegetation and from under tree-dominated vegetation. We non-destructively estimated soil base cations by measuring elemental concentrations of dried soil subsamples with a handheld x-ray fluorescence analyzer. We also measured carbon and nitrogen concentrations and isotopic composition of the soil samples. Soils in plots with high fire frequency had higher concentrations of calcium than soils in unburned plots (low fire frequency). Similar trends were seen for soil potassium, magnesium, and phosphorus concentrations. In contrast, soils in plots with high fire frequency had dramatically lowered nitrogen cycling rates and stocks across the oak savanna. The contrast between the responses of different nutrients to changing fire frequency has important implications for the consequences of fire and tree-grass composition on nutrient cycling dynamics.
5. Influence of composted dairy manure and perennial forage on soil carbon and nitrogen fractions during transition into organic management
Science.gov (United States)
Composted dairy manure (CDM) is among the management practices used in transitioning from a conventional to an organic agricultural system. The objectives of this study are to evaluate the impact of several organic nitrogen (N) sources on: (i) soil organic C (SOC) and soil total N (STN) content; (ii...
6. Nitrogen dynamics in the soil-plant system under deficit and partial root-zone drying irrigation strategies in potatoes
DEFF Research Database (Denmark)
Shahnazari, Ali; Ahmadi, Seyed Hamid; Lærke, Poul Erik
2008-01-01
Experiments were conducted in lysimeters with sandy soil under an automatic rain-out shelter to study the effects of subsurface drip irrigation treatments, full irrigation (FI), deficit irrigation (DI) and partial root-zone drying (PRD), on nitrogen (N) dynamics in the soil-plant system of potatoes...
7. Responsiveness of soil nitrogen fractions and bacterial communities to afforestation in the Loess Hilly Region (LHR) of China
Science.gov (United States)
Ren, Chengjie; Sun, Pingsheng; Kang, Di; Zhao, Fazhu; Feng, Yongzhong; Ren, Guangxin; Han, Xinhui; Yang, Gaihe
2016-06-01
In the present paper, we investigated the effects of afforestation on nitrogen fractions and microbial communities. A total of 24 soil samples were collected from farmland (FL) and three afforested lands, namely Robinia pseudoacacia L (RP), Caragana korshinskii Kom (CK), and abandoned land (AL), which have been arable for the past 40 years. Quantitative PCR and Illumina sequencing of 16S rRNA genes were used to analyze soil bacterial abundance, diversity, and composition. Additionally, soil nitrogen (N) stocks and fractions were estimated. The results showed that soil N stock, N fractions, and bacterial abundance and diversity increased following afforestation. Proteobacteria, Acidobacteria, and Actinobacteria were the dominant phyla of soil bacterial compositions. Overall, soil bacterial compositions generally changed from Actinobacteria (Acidobacteria)-dominant to Proteobacteria-dominant following afforestation. Soil N fractions, especially for dissolved organic nitrogen (DON), were significantly correlated with most bacterial groups and bacterial diversity, while potential competitive interactions between Proteobacteria (order Rhizobiales) and Cyanobacteria were suggested. In contrast, nitrate nitrogen (NO3--N) influenced soil bacterial compositions less than other N fractions. Therefore, the present study demonstrated that bacterial diversity and specific species respond to farmland-to-forest conversion and hence have the potential to affect N dynamic processes in the Loess Plateau.
8. Nitrogen mineralization in forestry-drained peatland soils in the Stołowe Mountains National Park (Central Sudetes Mts
Directory of Open Access Journals (Sweden)
Glina Bartłomiej
2016-06-01
Full Text Available The aim of this work was to determine the intensity of nitrogen mineralization in forestry drained ombrotrophic peatland soils in the Stołowe Mountains National Park, SW Poland. Additionally discussion about the shallow organic soils classification according to Polish Soil Classification (2011 is presented. For the study three research transects were established on forestry drained ombrotrophic peatlands in the Stołowe Mountains. Each of the transect consisted of four (site A and B or five (site C sampling plots. Sampling was conducted in the year 2012. The soil samples for the basic soil properties analysis were sampled in April, whereas undisturbed soil samples were collected in stainless steel rings (100 cm3 every 10 cm in April (spring, July (summer and October (autumn to show the seasonal dynamics of nitrogen mineralization. Statistical analysis showed that the content of N-NH4 was mainly determined by actual soil moisture and precipitation rate, whereas the content of N-NO3 was positively correlated with air temperature. Among investigated peatlands the highest concentrations of mineral nitrogen forms was observed in the Długie Mokradło bog, situated on the Skalniak Plateau-summit. Additionally, the results obtained showed that implementation of new subtype: shallow fibric peat soils (in Polish: gleby torfowe fibrowe płytkie within the type of peat soils (in polish: gleby torfowe should be considered during developing of the next update of Polish Soil Classification.
9. Nano-scale investigation of the association of microbial nitrogen residues with iron (hydr)oxides in a forest soil O-horizon
Science.gov (United States)
Keiluweit, Marco; Bougoure, Jeremy J.; Zeglin, Lydia H.; Myrold, David D.; Weber, Peter K.; Pett-Ridge, Jennifer; Kleber, Markus; Nico, Peter S.
2012-10-01
Amino sugars in fungal cell walls (such as chitin) represent an important source of nitrogen (N) in many forest soil ecosystems. Despite the importance of this material in soil nitrogen cycling, comparatively little is known about abiotic and biotic controls on and the timescale of its turnover. Part of the reason for this lack of information is the inaccessibility of these materials to classic bulk extraction methods. To address this issue, we used advanced visualization tools to examine transformation pathways of chitin-rich fungal cell wall residues as they interact with microorganisms, soil organic matter and mineral surfaces. Our goal was to document initial micro-scale dynamics of the incorporation of 13C- and 15N-labeled chitin into fungi-dominated microenvironments in O-horizons of old-growth forest soils. At the end of a 3-week incubation experiment, high-resolution secondary ion mass spectrometry imaging of hyphae-associated soil microstructures revealed a preferential association of 15N with Fe-rich particles. Synchrotron-based scanning transmission X-ray spectromicroscopy (STXM/NEXAFS) of the same samples showed that thin organic coatings on these soil microstructures are enriched in aliphatic C and amide N on Fe (hydr)oxides, suggesting a concentration of microbial lipids and proteins on these surfaces. A possible explanation for the results of our micro-scale investigation of chemical and spatial patterns is that amide N from chitinous fungal cell walls was assimilated by hyphae-associated bacteria, resynthesized into proteinaceous amide N, and subsequently concentrated onto Fe (hydr)oxide surfaces. If confirmed in other soil ecosystems, such rapid association of microbial N with hydroxylated Fe oxide surfaces may have important implications for mechanistic models of microbial cycling of C and N.
10. Effect of vegetation types on soil arbuscular mycorrhizal fungi and nitrogen-fixing bacterial communities in a karst region.
Science.gov (United States)
Liang, Yueming; Pan, Fujing; He, Xunyang; Chen, Xiangbi; Su, Yirong
2016-09-01
Arbuscular mycorrhizal (AM) fungi and nitrogen-fixing bacteria play important roles in plant growth and recovery in degraded ecosystems. The desertification in karst regions has become more severe in recent decades. Evaluation of the fungal and bacterial diversity of such regions during vegetation restoration is required for effective protection and restoration in these regions. Therefore, we analyzed relationships among AM fungi and nitrogen-fixing bacteria abundances, plant species diversity, and soil properties in four typical ecosystems of vegetation restoration (tussock (TK), shrub (SB), secondary forest (SF), and primary forest (PF)) in a karst region of southwest China. Abundance of AM fungi and nitrogen-fixing bacteria, plant species diversity, and soil nutrient levels increased from the tussock to the primary forest. The AM fungus, nitrogen-fixing bacterium, and plant community composition differed significantly between vegetation types (p fungi and nitrogen-fixing bacteria, respectively. Available phosphorus, total nitrogen, and soil organic carbon levels and plant richness were positively correlated with the abundance of AM fungi and nitrogen-fixing bacteria (p fungi and nitrogen-fixing bacteria increased from the tussock to the primary forest and highlight the essentiality of these communities for vegetation restoration.
11. Bermudagrass Management in the Southern Piedmont U.S. IV. Soil Surface Nitrogen Pools
Directory of Open Access Journals (Sweden)
Alan J. Franzluebbers
2001-01-01
Full Text Available The fate of nitrogen (N applied in forage-based agricultural systems is important for understanding the long-term production and environmental impacts of a particular management strategy. We evaluated the
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https://support.nutbourne.com/hc/en-us/articles/201720067-Mapping-a-network-drive
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# Mapping a network drive
If you are unsure about approaching this issue please call our helpdesk as you can irreversibly damage your PC if you are not careful
Before mapping a network drive, it is essential to know the file path for the network resource / Folder you wish to map. The file path will be in the following format:
\\server\share name
Although there is a slight variation in theme and appearance, the process of mapping a network drive is essentially the same on Windows XP/Windows Vista/Windows 7. In order to map a network drive, follow the instructions below.
- Access the start menu in the bottom left hand corner of your screen.
- From the start menu, right click on the computer/my computer option and select map network drive.
- You will now be presented with a new window.
- For the field named drive, select the letter you wish to map the resource to.
- For the field named folder, enter the file path of the Folder you wish to map, an example of the format of the file path is detailed in bold above.
- Now click Finish.
The folder will now be mapped as a network drive.
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http://math.stackexchange.com/questions/54611/a-relation-r-such-that-r-cup-r-1-is-not-an-equivalence-relation/54614
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# A relation $R$ such that $R\cup R^{-1}$ is not an equivalence relation
I have a homework assignment to find a Relation $R$ over $A = \{1,2,3\}$ where $R\cup {{R}^{-1}}$ is not an equivalence relation (transitive, reflexive and symmetrical).
$R$ must be Transitive and Reflexive (${{I}_{A}}\subseteq R$)
Any clue anyone? I just am unable to find an example
Thanks
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If $I_A\subseteq R$, then you are guaranteed that $R$ is reflexive; however, you are not guaranteed that $R$ is transitive. – Arturo Magidin Jul 30 '11 at 16:28
@Arturo I meant that there is a restriction on your selected R and that restriction is it must be Transitive and Reflexive – Jason Jul 30 '11 at 16:51
Okay; it wasn't clear, because the parenthetical comment "$I_A\subseteq R$" looks like the justification for "$R$ must be transitive and reflexive". – Arturo Magidin Jul 30 '11 at 17:20
Nha, I'm just translating from my language so I was not sure of the term in English so I added it just to be sure. – Jason Jul 30 '11 at 17:26
Yes, I see what it was you tried to say: it was just the justification for the final clause, not for the entire sentence. It just seemed like it was a justification for the entire sentence. – Arturo Magidin Jul 30 '11 at 17:44
Given that you are assuming that $R$ is reflexive, the only thing that can fail for $R\cup R^{-1}$ to be an equivalence relation is transitivity: you should verify that since $I_A\subseteq R$, then $I_A\subseteq R\cup R^{-1}$; and that $R\cup R^{-1}$ is symmetric for every relation $R$. So the only possible pitfall lies in transitivity.
Now, you are assuming that $R$ itself is transitive. So, how can transitivity fail? Say you have $(a,b),(b,c)\in R\cup R^{-1}$; if $(a,b),(b,c)\in R$, then since we are assuming $R$ is transitive, then $(a,c)\in R\subseteq R\cup R^{-1}$. If $(a,b),(b,c)\in R^{-1}$, then $(c,b),(b,a)\in R$, and again by transitivity we conclude $(c,a)\in R$, hence $(a,c)\in R^{-1}\subseteq R\cup R^{-1}$.
So what's left? What happens if $(a,b)\in R$, and $(b,c)\in R^{-1}$, but we do not have $(a,b)\in R^{-1}$ nor $(b,c)\in R$? Can you construct such an example? What will happen then?
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Thanks I did manage to narrow it to the Transitive property but could not find an example for some reason :) – Jason Jul 30 '11 at 16:49
One sometimes helpful way to approach questions like this, if you can't find a counterexample, is simply to try and prove the opposite: that is, prove that $R\cup R^{-1}$ is an equivalence relation. Well, it's obviously reflexive; it's also obviously symmetric, because anything in $R$ will have its inverse in $R^{-1}$. So transitivity must be where it breaks down.
Suppose there are two relations a~b and b~c in $R\cup R^{-1}$ whose product a~c is not in $R\cup R^{-1}$. (You might also write these relations (a,b), etc.) It's easy to see that a, b and c must all be distinct elements, so in fact, we might as well choose 1~2, 2~3 and 1~3: we want the first two to be in $R\cup R^{-1}$, but not the third.
As $R$ is transitive, we can't have both 1~2 and 2~3 in $R$. Likewise they can't both be in $R^{-1}$ (otherwise, flip them over to $R$ and use transitivity there). So one of them must be in $R$ and one in $R^{-1}$. Taking $R$ and $R^{-1}$ to be minimal relations containing 1~2 and 2~3 respectively works as a counterexample.
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http://mymathforum.com/advanced-statistics/337068-standard-normal-distribution.html
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My Math Forum Standard Normal Distribution
November 2nd, 2016, 05:11 PM #1 Newbie Joined: Oct 2016 From: Earth Posts: 16 Thanks: 0 Standard Normal Distribution $Z$ ~ $N$(0,1) How to show that $Z\stackrel{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$)? Also how to show that only the standard normal distribution satisfies these 2 properties? In other words, if you have $Z\overset{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$), then $Z$ ~ $N$(0,1). To show that $Z\stackrel{d}{=} -Z$: I know that distribution of $Z$ is $F(z) = \frac{1}{2} + \phi(z)$, where $\phi(z) = \int_{0}^{z} e^{\frac{-t^2}{2}} dt$. Also $\phi(-z)=\phi(z)$. $P(-Z < z) = P(Z > -z) = 1 - P(Z < -z) = 1 - (\frac{1}{2} + \phi(-z)) = 1 - (\frac{1}{2} - \phi(z)) = \frac{1}{2} + \phi(z) = P(Z < z)$. Hence $Z\stackrel{d}{=} -Z$. To show that $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$): $P(\frac{Z^2}{2} < z) = P(-\sqrt{2z} < Z < \sqrt{2z}) = 2\phi(\sqrt{2z})$. Now, this is where I am stuck. How do I continue to get gamma($\frac{1}{2}$)? Also how to show if you have $Z\overset{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$), then $Z$ ~ $N$(0,1)?
November 3rd, 2016, 05:02 AM #2 Newbie Joined: Oct 2016 From: Earth Posts: 16 Thanks: 0 I am surprised that is no edit button. Anyway, I have corrected some typos. $Z$ ~ $N$(0,1) How to show that $Z\stackrel{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$)? Also how to show that only the standard normal distribution satisfies these 2 properties? In other words, if you have $Z\overset{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$), then $Z$ ~ $N$(0,1). To show that $Z\stackrel{d}{=} -Z$: I know that distribution of $Z$ is $F(z) = \frac{1}{2} + \phi(z)$, where $\phi(z) = \frac{1}{\sqrt{2\pi}}\int_{0}^{z} e^{\frac{-t^2}{2}} dt$. Also $\phi(-z)=\phi(z)$. $P(-Z < z) = P(Z > -z) = 1 - P(Z < -z) = 1 - (\frac{1}{2} + \phi(-z)) = 1 - (\frac{1}{2} - \phi(z)) = \frac{1}{2} + \phi(z) = P(Z < z)$. Hence $Z\stackrel{d}{=} -Z$. To show that $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$): $P(\frac{Z^2}{2} < z) = P(-\sqrt{2z} < Z < \sqrt{2z}) = 2\phi(\sqrt{2z})$. Now, this is where I am stuck. How do I continue to get gamma($\frac{1}{2}$)? Also how to show if you have $Z\overset{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$), then $Z$ ~ $N$(0,1)?
November 3rd, 2016, 07:06 PM #3 Newbie Joined: Oct 2016 From: Earth Posts: 16 Thanks: 0 Ok, differentiating $2\phi(\sqrt{2z})$ with respect to $z$ gives me $\frac{e^{-z}}{\sqrt{\pi}\sqrt{z}} = \frac{z^{\frac{1}{2}-1}e^{-z}}{\Gamma(\frac{1}{2})}$ which is the probability density function of gamma$(\frac{1}{2}, 1)$. Hence, I believe I have solved it. Now, if someone could help me with the reverse direction, I would greatly appreciate it.
November 3rd, 2016, 11:27 PM #4 Newbie Joined: Oct 2016 From: Earth Posts: 16 Thanks: 0 Corrected more typos: $Z$ ~ $N$(0,1) How to show that $Z\stackrel{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$)? Also how to show that only the standard normal distribution satisfies these 2 properties? In other words, if you have $Z\overset{d}{=} -Z$ and $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$), then $Z$ ~ $N$(0,1). To show that $Z\stackrel{d}{=} -Z$: I know that distribution of $Z$ is $F(z) = \frac{1}{2} + \phi(z)$, where $\phi(z) = \int_{0}^{z} e^{\frac{-t^2}{2}} dt$. Also $\phi(-z)=-\phi(z)$. $P(-Z < z) = P(Z > -z) = 1 - P(Z < -z) = 1 - (\frac{1}{2} + \phi(-z)) = 1 - (\frac{1}{2} - \phi(z)) = \frac{1}{2} + \phi(z) = P(Z < z)$. Hence $Z\stackrel{d}{=} -Z$. To show that $\frac{Z^2}{2}$ ~ gamma($\frac{1}{2}$): $P(\frac{Z^2}{2} < z) = P(-\sqrt{2z} < Z < \sqrt{2z}) = 2\phi(\sqrt{2z})$. Differentiating $2\phi(\sqrt{2z})$ with respect to $z$ gives me $\frac{e^{-z}}{\sqrt{\pi}\sqrt{z}} = \frac{z^{\frac{1}{2}-1}e^{-z}}{\Gamma(\frac{1}{2})}$ which is the probability density function of gamma$(\frac{1}{2}, 1)$. I would greatly appreciate it if somebody could help me with the reverse direction. Last edited by geniusacamel; November 3rd, 2016 at 11:32 PM.
November 3rd, 2016, 11:37 PM #5 Senior Member Joined: Sep 2015 From: USA Posts: 2,430 Thanks: 1315 neat problem. Ok you have a random variable $U$ which is distributed as $\Gamma\left(\dfrac 1 2 , 1\right) = \dfrac{e^{-u}}{\sqrt{\pi u}}$ now $Z = \sqrt{2U}$ \$F_Z(z) = P[Z < z] = P[\sqrt{2U}
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https://verify-training.com/lms/course/index.php?categoryid=15
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### Online Electrical Theory 4 Hours WA2020-035
###### 4 HOURS OF CEU CREDIT IN THE INDUSTRY KNOWLEDGE CATEGORY TOWARD JOURNEY RENEWAL
• Based on the Ferm's Formulas Calculations and Charts ®, Book and other Electrical Theory sources
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http://indico.cern.ch/event/175269/
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# Physics at the AD/PS/SPS (3/4)
## by Augusto Ceccucci (CERN)
Europe/Zurich
6-2-024 - BE Auditorium Meyrin (CERN)
### 6-2-024 - BE Auditorium Meyrin
#### CERN
120
Show room on map
Description Lecture 3: Flavour and Neutrinos The CERN SPS provides kaon and neutrino beams which are unique in the world. The lecture will describe the flavour and neutrino research conducted with these beams. The flavour programme is centered around the study of kaons. It includes a broad spectrum of topics such as CP-Violation, the precise determination of quark-mixing parameters, lepton universality and very rare decays. The CNGS neutrino beam enables to perform long baseline neutrino oscillation experiments with unique features such as the tau lepton appearance. Slides Video in CDS From the same series 1 2 4
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https://techwhiff.com/learn/let-sn-be-a-symmetric-one-dimensional-random-walk/106141
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# Let Sn be a symmetric one-dimensional random walk with respect to the standard filtration {Fi} i...
###### Question:
Let Sn be a symmetric one-dimensional random walk with respect to the standard filtration {Fi} i >= 0. Show that Mn= S2n - n is a martingale.
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##### Find the range of ? f(x) = |x| + 3
f(x) = |x| + 3...
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http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.563692
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Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.563692
Title: Measurement of the G double-polarisation observable in positive pion photoproduction
Author: McAndrew, Josephine
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2012
Availability of Full Text:
Access from EThOS: Full text unavailable from EThOS. Please try the link below. Access from Institution:
Abstract:
Establishing the resonance spectrum of the nucleon with accuracy would provide important new information about the dynamics and degrees of freedom of its constituents. The spectrum and properties of nucleon resonances are a fundamental test of the emerging predictions from Lattice QCD calculations and will guide re finements to QCD-based phenomenological models. Pion photoproduction is an excellent tool to study the nucleon resonance spectrum, as this channel is expected to couple strongly to most resonances. The new generation of measurements for this reaction, of which the measurement presented in this thesis forms a crucial part, will provide a great improvement in the quality of available experimental data. For the photoproduction process in particular, the use of photon beams and targets with high degrees of polarisation, coupled with large acceptance particle detectors is essential for disentangling the spectrum of excited states. There are many nucleon resonances predicted by recent Lattice QCD calculations and by phenomenological nucleon models which are only observed inconsistently by different analyses of the same experimental data or which are not observed at all. It is of upmost importance to establish if this means that the resonances do not exist in nature, reflecting inappropriate degrees of freedom in the theoretical description of the nucleon or if the current experimental measurements have not been sensitive enough. As such, there is a current world effort at modern tagged photon facilities to measure the \complete set" of photoproduction observables necessary to fully constrain the partial wave analyses used to extract the experimental excitation spectrum from the data. This thesis will present the first detailed measurement to date of positive pion photoproduction in the 730-2300 MeV photon energy (1400-2280 MeV centre-of-mass energy) region with a linearly polarised photon beam and a longitudinally polarised proton target with a close-to-complete angular coverage in detection of the reaction products. This unique set up allows for the extraction of the double-polarisation observable, G. The data were taken as part of the g9 experiment at the Thomas Jefferson National Accelerator Facility in Virginia, using a tagged, polarised photon beam and the Frozen Proton Spin Target, FROST, in conjunction with the CEBAF Large Acceptance Spectrometer, CLAS. The results of the study presented here are compared to the sparse existing data set for the G double-polarisation observable along with the current solutions of the the three main partial wave analyses: MAID, SAID and Bonn-Gatchina. Some agreement is obtained with the expectations of these PWA at lower energies, while disagreement at higher energies is clearly evident. This is the energy region where many of the missing resonances are expected to lie. Once incorporated into the MAID, SAID and Bonn-Gatchina models, these new data will provide an important contribution to constraining the amplitudes and therefore the resonance spectrum and properties of the nucleon. The new data will form a central part of the world effort to accurately establish the nucleon excitation spectrum for the first time by achieving the first complete measurement of experimental observables in meson photoproduction.
Supervisor: Watts, Daniel. ; Woods, Philip. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.563692 DOI: Not available
Keywords: polorisation observables ; hadron spectroscopy ; proton ; photoproduction
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https://math.stackexchange.com/questions/1256841/when-is-6-a-square-in-zp
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# When is 6 a square in Zp
To find when $6$ is a square I divided $6$ in to $2$ and $3$ by The Legendre symbol.
$$\frac{6}{p} = \frac{2}{p} \times \frac{3}{p}$$
I know that we can multiply the cases of when $2$ and are squares because then it is (1)(1) by Legendre.
$2$ is a square when $p \equiv 1 \pmod{8}$
$3$ is a square when $p \equiv 1 \pmod{12}$
so $6$ is a square when $p \equiv 1 \pmod {24}$ ($96$, but the $lcm(8,12)= 24$)
but how do I find the cases when $2$ and $3$ are both NOT squares? because then $6$ would be a square then as well, $(-1)(-1) = 1$ by Legendre.
Note that $2$ is a square mod $p$ when $p = 1$ or $p = 7\pmod{8}$, and is not a square when $p = 3$ or $p = 5 \pmod{8}$.
Similarly, using reciprocity we have that $3$ is a square mod $p$ when $p = 1$ or $p = 11 \pmod{12}$ and is not a square when $p = 5$ or $p = 7\pmod{12}$.
This information should be enough to determine what happens for each congruence class mod $24$.
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https://chemistry.stackexchange.com/questions/60621/how-can-a-molecular-orbital-with-a-nodal-plane-still-be-considered-bonding
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# How can a molecular orbital with a nodal plane still be considered “bonding”?
Explain how a molecular orbital can have a nodal plane and still be a bonding molecular orbital.
I understand the concept of how nodal planes are formed and how they have a probability of 0 when trying to find an electron in the nodal plane, but I don't understand how it can be considered a bond especially since these nodal planes are usually called "anti-bonding". This question itself seems contradictory and I'm having a hard time trying to understand how this is possible.
The number of nodal planes isn't the determining factor. Yes, having more nodal planes increase the energy of the orbital, but you need to consider the fact that some MOs (specifically the anti bonding ones) are raised in energy. Overall, the total energy of the orbitals is the same as before, so you stabilize some and destabilize others. Take a look at the MOs and you can see that the there's two bonding MOs with one nodal plane perpendicular to the plane of the benzene with $E_{1}$ symmetry. Likewise, there's a pair of MOs with two nodal planes that with $E_{1}$ symmetry that are anti-bonding. These pairs happened to be correlated in that the increase in energy of the anti-bonding orbitals is essentially matched by the stabilization of the bonding orbitals.
An intuitive way of looking at this is that when you have many atoms to consider, there will be multiple bonding/antibonding interactions between atoms. Whether the MO is overall bonding or antibonding will depend on the sum of these interactions. This is rather simplified, but using the example of benzene again, we can examine the three bonding π MOs:
MO 1 (the lowest-energy π MO) has one nodal plane in the plane of the ring. However, because this isn't a plane separating two constituent atomic orbitals (the p orbitals), this nodal plane doesn't tell us anything about bonding/antibonding properties of the MO. Indeed, this nodal plane only arises because the building blocks – the p-orbitals – have a node in their centre. The interactions between different p-orbitals are all bonding in nature, because the shaded (positive) lobes of each p-orbital are overlapping with the shaded lobes of their neighbours (and vice versa for the unshaded lobes).
MO 2 has a nodal plane between p-orbitals, which suggests the presence of antibonding character. That is true: there are two major antibonding interactions, one between the top-left and top-right carbons, and one between the bottom-left and bottom-right carbons. (The middle-left and middle-right carbons are too far apart). However, there are also multiple bonding interactions: the three carbons on the left, for example, are all interacting with each other in a bonding fashion. Overall, this MO is bonding, although not quite "as bonding" as MO 1.
Likewise, MO 3 has antibonding interactions between the top-left and bottom-left carbons (for example). It also has bonding interactions between the top-left and top-right carbons. However, the antibonding interactions are occurring over a greater distance than the bonding interactions. Consequently, they are weaker than the bonding interactions, and again we have a case of net bonding.
• I'm not sure if Hückel theory is rigorous enough to invoke, but in that theory the coefficients are also different, which is why even though MO3 has "fewer bonding" orbitals, it can still be degenerate with MO2. This can be intuitively depicted by varying the sizes of the orbitals. Page 5 in the following link shows this: ocw.mit.edu/courses/chemistry/5-61-physical-chemistry-fall-2007/… – Blaise Jan 24 '19 at 2:53
• I wish one would separate the concept of bonding/ anti-bonding interactions from energy considerations. There are probably examples where an 'overall bonding' MO is anti-bonding with respect to one bond, which will be elongated due to that fact. After all these considerations led to the believe that the HOMO of CO is anti-bonding, which cannot be supported by any kind of theory. There is one universal truth: All molecular orbitals have nodal surfaces. Within every MO there are bonding and/or anti-bonding interactions. – Martin - マーチン Jan 25 '19 at 18:13
• @Blaise Symmetry alone dictates that MO2 and 3 depicted above are degenerate (and any linear combinations thereof). Hückel's calculations show that in a very simple and accurate way. – Martin - マーチン Jan 25 '19 at 18:18
• @Martin-マーチン in Huckel theory, any interaction between atom $i$ and $j\neq i$ leads to a contribution of $2\beta_{ij}c_ic_j$ to the energy $E = \mathbf{c^THc}$; so AFAIK I think it is fair enough to link bonding ($c_ic_j > 0$) interactions to a decrease in energy and antibonding ($c_ic_j < 0$) interactions to an increase (since $\beta_{ij} < 0$). The way I'm seeing it (correct me if I'm wrong), the problem is linking this to the overall bonding/antibonding character of an MO. For benzene it is simple, because every p-orbital has the same value of $\alpha$; so for the MO if $E < \alpha$ [...] – orthocresol Jan 25 '19 at 19:54
• [...] we can say it is bonding, and if $E > \alpha$ it is antibonding. In the absence of any interactions between pairs of AOs (which corresponds to turning every off-diagonal element $\beta_{ij}$ to zero), every MO simply has the energy $\alpha$, so any form of bonding interactions will bring the energy below $\alpha$. Thus we regain the qualitative and rather simplified picture in my answer. For CO we don't have the privilege of all $\alpha_i$ being the same, and consequently I don't know if this kind of approach remains valid. – orthocresol Jan 25 '19 at 19:57
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http://mathhelpforum.com/calculus/24925-fourier-transform.html
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# Math Help - Fourier Transform
1. ## Fourier Transform
ImageShack - Hosting :: questionyw0.jpg
I was asked to find the fourier transform of x(n). Could someone explain whats happening in this answer?
Thanks
2. Originally Posted by hammer
ImageShack - Hosting :: questionyw0.jpg
I was asked to find the fourier transform of x(n). Could someone explain whats happening in this answer?
Thanks
I presume the problem is in simplifying $X(\omega)$?
$X(\omega) = \sum_{n = -4}^{\infty} \left ( \frac{1}{4} \right )^ne^{-j \omega n}$
Define $m = n + 4$. Then
$X(\omega) = \sum_{n = -4}^{\infty} \left ( \frac{1}{4} \right )^ne^{-j \omega n} = \sum_{m = 0}^{\infty} \left ( \frac{1}{4} \right )^{m - 4}e^{-j \omega (m - 4)}$
$= \sum_{m = 0}^{\infty} \left ( \frac{1}{4} \right )^m \cdot \left ( \frac{1}{4} \right )^{-4}e^{-j \omega m }e^{-(-4)j \omega }$
So
$X(\omega) = \sum_{m = 0}^{\infty} \left ( \frac{1}{4} \right )^m e^{-j \omega m }4^4e^{4j \omega }$
Now, note that the last two factors are independent of m:
$X(\omega) = 4^4e^{4j \omega } \cdot \sum_{m = 0}^{\infty} \left ( \frac{1}{4} \right )^m e^{-j \omega m }$
Note also that the summation is the summation of an infinite geometric series. The sum of any geometric series is
$\sum_{m = 0}^{\infty} ar^m = \frac{a}{1 - r}$
Thus
$\sum_{m = 0}^{\infty} \left ( \frac{1}{4} \right )^m e^{-j \omega m } = \sum_{m = 0}^{\infty} \left ( \frac{e^{-j \omega}}{4} \right )^m = \frac{1}{1 - \frac{e^{-j \omega}}{4}}$
So finally we get:
$X(\omega) = 4^4e^{4j \omega } \cdot \frac{1}{1 - \frac{e^{-j \omega}}{4}}$
$X(\omega) = \frac{4^4e^{4j \omega }}{1 - \frac{e^{-j \omega}}{4}}$
-Dan
3. Originally Posted by hammer
ImageShack - Hosting :: questionyw0.jpg
I was asked to find the fourier transform of x(n). Could someone explain whats happening in this answer?
Thanks
This is a Discrete Fourier Transform, $X(\omega)$ (on the second line) is the transform of $x(n)$
by definition of the DFT (and that $u(n)=0$ for $n<0$, and $1$ otherwise).
The rest is just simplification using the sum of a geometric series formula.
ZB
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https://ajitjadhav.wordpress.com/2015/09/27/the-bhatnagar-prizes-2015/
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# The Bhatnagar prizes 2015
The Bhatnagar prizes [^] for 2015 have been announced [(.PDF) ^]. The selections seem to be, as usual, the “safe” ones. So there can’t be much to comment on, on that count.
So, let me try to squeeze out something interesting and relevant from that bit of the news.
As far as I am concerned, the first interesting bit is this: I “know”—i.e. have run into and exchanged a few words with—one of the awardees. Exactly once, at a conference. The fellow in question is Dr. Mandar Deshmukh (2015, Physical Sciences). From the presentation he made at that conference, it was quite clear (at least to me) that he was doing some neat science. While making his presentation, he had assumed that informal and abstract air which by now has become typical for the relatively younger IIT Bombay graduates. I do like this change in them. Earlier, i.e. in my times and earlier, they used to be far too arrogant, pompous, or self-assuming. Even in their informal presentations. Important to me, Deshmukh carried the same air of informality (of a kind of friendliness, almost) during the in-person chat that I had with him on the side-lines during the buffet lunch. Why, he even casually asked me (as others) to “drop by [his] lab and have a look at the equipment any time,” adding that it was “interesting,” with a glint in his eye. Hmmm… Turns out that he has continued doing “interesting” things. (This conference was in 2009 or 2010.) As far as I am concerned, this selection seems quite right. So, congratulations, Dr. Deshmukh!
The second interesting bit is that Deshmukh was the second person present at that conference with who I had chatted during lunch and who eventually got the Bhatnagar award. The first person was Dr. Umesh Waghmare. (Yet another younger IIT Bombay alumnus.)
To go on to the third interesting bit, let me note that it was not a very “official” kind of a conference. It was just a symposium arranged to honor Professor Dilip Kanhere, on the occasion of his retirement as a Professor of Physics in the (now S. P.) University of Pune. There were no brownie points to be scored from this conference; people got together only out of respect for the retiring professor—and of course, out of the love of the research topics. Important to note: People had dropped by from as far places as the USA, Germany, Sweden, etc. (I came to know Prof. Kanhere through Web searches; he had just founded the Center for Modeling and Simulation; I was interesting in anything combining computation and physics. I approached him; he allowed me to attend his classes and generally roam around in the CMS for a while.)
So, the interesting bit is the knack that Prof. Kanhere evidently has to gather together some talented (and/or interesting) people. [I don’t mean to refer to me here.] I don’t know why not every professor succeeds doing that. But some professors do have this knack. Talented folks somehow “smell” such people and almost as if “by default” gather around them. Consider Kanhere’s PhD students (or research associates), and compare them to any randomly selected PhD from any department at the S. P. University of Pune during the same time; Kanhere’s students (and associates) stand out. The current director of CMS, Anjali Kshirsagar, is his PhD student; many others have had post-docs at good institutes abroad, which, incidentally, is a good benchmark for Indian universities (other than the IIXs). This point is important.
Even while working within the “parameters” of this third-class university (I mean the S. P. University of Pune), Kanhere managed to inculcate the right kind of intellectual spirit, and culture in his group, why, even some simple manners and rules of etiquette that researchers from the first-world almost always follow, and a normal guy in the S. P. University of Pune is blissfully (or more likely: arrogantly) unaware of. (Ditto for almost any other Indian university.) At least as far as I am concerned, if I know that if someone has been a student or post-doc with Prof. Kanhere, I immediately know that my emails will not only be read but also replied—and more important, its contents would be thought about before the reply is made (and perhaps also afterwards). It’s something like the atmosphere at iMechanica that Prof. Zhigang Suo has managed to create and maintain. How do some professors succeed doing such a thing regardless of the environment surrounding them? [Compare other blogging fora and iMechanica, on this count: the overall and general civility of the interaction present at iMechanica, combined with the informality. The fact that iMechanica is based at Harvard must have helped to a great extent, but this one factor alone doesn’t explain the outcome.]
So, how is a better atmosphere created? I have no idea. But the point especially relevant to us Indians is: it requires almost no money, almost no hard-work. (Well at least, not the futilely draining kind of a hard-work). And yet, only a few professors ever manage to accomplish that. It’s not everyone’s cup of tea. [As a professor myself, I am too new to know if I could manage to do that. But my point is: I would like to at least try.]
There is a value in such things. Kanhere’s students (and the people who had gathered for his retirement symposium) happened to be more or less the only people who (i) did not laugh at me when I said I am trying to derive a new view of QM, (ii) did not advise me to go read text-books within the first 5 minutes of my mentioning my published paper (or in the first email (if at all a reply came forth)), and (iii) did not try to avoid me the next time we ran into each other. Indeed, as far as the in-person interaction goes, the only people who have ever thoughtfully and informally commented on my QM ideas were Kanhere’s students. One of his students (then a professor himself) emphasized the complex number nature of the $\Psi$ wave-function, and also brought home the fact that the name random variable is a misnomer, it actually being a function. Another student of his (again himself a professor) emphasized the conjugate nature of energy and time, not just of the momentum and position; see John Baez’ coverage here [^]. He also pointed out quantum chemistry to me; I didn’t know about it (“just substitute $it$ in place of $t$; you will get it”). This, while people were busy saying to me that they won’t read a paper if it was about QM and written in MS Word, and that I should send the paper to a journal. (If they themselves couldn’t bother to even read the paper, why would they think that a journal could accept it? Blank-out. As far as they were concerned, the fact was that I myself had approached them, and so in that very act, I myself had put them in a higher, advising, position; they would therefore be generous in dispensing advice; the matter ended there as far as they were concerned.)
Reading the post in the plain, it’s impossible to convey what value mere “emphases” can be, because the issues are so generally well known. The point is: within the context of that particular discussion, within the context of that particular cluster of ideas, it’s just this one word emphasis that really gives you the clue. … It’s been more than five years since these comments, and I still marvel at how they got me out of my conceptual difficult spots with these off-hand but thoughtful remarks. (Their clarifications and even casually expressed emphases continue to help me, including during my recent-most brain-storming that I noted just yesterday in the previous post.) Why would only Kanhere’s students do that, despite the individual differences between them?
Thus, to use a cliche, some people manage to bring people together in such a way that 1 and 1 does not become 2; it becomes 11. How do they manage to do that? I have no idea.
How was it that Bohr managed to attract so many talented people to his institute? It is especially relevant to point out to Indians that this “institute,” when it was founded, had only one professor—Bohr himself—and a couple of other support staff. The visitors (like Heisenberg) would be lodged in a top-floor “room” (one having a low slanted roof), in the same building. Why, even as recently as in the late 1990s, the “University Department” at Utrecht had a faculty strength of less than 10—that’s roughly the time when Professor Gerard ‘t Hooft got his Nobel. The “Department” was that small; yet he would manage to attract talented folks from all over the world, i.e., even before the time that he got his Nobel. Sommerfeld had this same knack; look at the list of the PhDs he graduated and the post-docs he nurtured. For an example of the more recent times and from the US, look at the list of John Wheeler’s PhD students and post-docs: Richard Feynman and Kip Thorne count among his PhD students. Kip Thorne himself has been attracting an incredibly large pool of PhD students, post-docs and research associates.
Why do some people succeed attracting talent? Are there any lessons we can draw and learn? Let us not focus only on the Nobel laureates. Really speaking, winners of the Nobel prizes, or their mentors, do not make for a good, fitting example for us Indians. It cannot. Precisely because the achievement in question is so great, the difference in the perceived levels so large, that we Indians actually end up doing is to silently dismiss such instances away without any actual consideration. We cannot draw any lessons from them, for the simple reason that the very possibility of building the super-high-end intellectual hubs is completely surreal to us. [And, our friends and kins in the USA, esp. those in the San Francisco Bay Area, specialize in continually reminding us of the impossibility.]
So, let’s lower our bar a bit. I don’t mind doing that. But lowering the bar doesn’t mean we stop attempting. We can—and must—ask: is it possible to replicate, say, Professor Kanhere’s success, even if Wheeler’s example would be completely surreal to us? Is it possible to create an environment in which a prior PhD failure, esp. the one in engineering (and that too from a US university) runs into a physics professor, and says something using some stupid halting words which effectively convey: he wants to reformulate the foundations of QM. He says that, and still the physics professor doesn’t laugh it away right then and there? Is it possible to create this kind of an environment? Not just at an IIX, but also within the lowly S. P. University of Pune? Yes, it is possible; it has happened. … Is it possible that future Bhatnagar recipients flock together for what basically is just a “send-off” function of a non-IIX professor? Yes, it is possible; it has happened.
And, if such things are possible, then, the next question is: what precisely does it take to make it happen? to replicate it? I would like to know.
Over to you all.
[And, in the meanwhile, congratulations to the fresh Bhatnagar awardees once again, esp. Dr. Deshmukh.]
A Song I Like:
(Hindi) “yeh dil aur un ki nigahon ke saaye”
Music: Jaidev
Lyrics: Jan Nisar Akhtar
Singer: Lata Mangeshkar
[E&OE]
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https://socratic.org/questions/what-s-the-equation-of-a-line-with-slope-2-passing-through-3-5
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Algebra
Topics
# What's the equation of a line with Slope=2,passing through (3,5)?
Mar 16, 2018
$y = 2 x - 1$
#### Explanation:
$\text{the equation of a line in "color(blue)"slope-intercept form}$ is.
•color(white)(x)y=mx+b
$\text{where m is the slope and b the y-intercept}$
$\text{here } m = 2$
$\Rightarrow y = 2 x + b \leftarrow \textcolor{b l u e}{\text{is the partial equation}}$
$\text{to find b substitute "(3,5)" into the partial equation}$
$5 = 6 + b \Rightarrow b = 5 - 6 = - 1$
$\Rightarrow y = 2 x - 1 \leftarrow \textcolor{red}{\text{in slope-intercept form}}$
##### Impact of this question
5966 views around the world
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https://phys.libretexts.org/Bookshelves/Electricity_and_Magnetism/Book%3A_Electromagnetics_I_(Ellingson)/05%3A_Electrostatics/5.16%3A_Potential_Field_Within_a_Parallel_Plate_Capacitor
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$$\require{cancel}$$
# 5.16: Potential Field Within a Parallel Plate Capacitor
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This section presents a simple example that demonstrates the use of Laplace’s Equation (Section 5.15) to determine the potential field in a source free region. The example, shown in Figure $$\PageIndex{1}$$, pertains to an important structure in electromagnetic theory – the parallel plate capacitor. Here we are concerned only with the potential field $$V({\bf r})$$ between the plates of the capacitor; you do not need to be familiar with capacitance or capacitors to follow this section (although you’re welcome to look ahead to Section 5.22 for a preview, if desired). What is recommended before beginning is a review of the battery-charged capacitor experiment discussed in Section 2.2. In this section you’ll see a rigorous derivation of what we figured out in an informal way in that section.
Figure $$\PageIndex{1}$$: A parallel plate capacitor, as a demonstration of the use of Laplace's Equation.
The parallel-plate capacitor in Figure $$\PageIndex{1}$$ consists of two perfectly-conducting circular disks separated by a distance $$d$$ by a spacer material having permittivity $$\epsilon$$. There is no charge present in the spacer material, so Laplace’s Equation applies. That equation is (Section 5.15): $\nabla^2 V = 0 ~~\mbox{(source-free region)} \label{m0068_eLaplace}$ Let $$V_C$$ be the potential difference between the plates, which would also be the potential difference across the terminals of the capacitor. The radius $$a$$ of the plates is larger than $$d$$ by enough that we may neglect what is going on at at the edges of the plates – more on this will be said as we work the problem. Under this assumption, what is the electric potential field $$V({\bf r})$$ between the plates?
This problem has cylindrical symmetry, so it makes sense to continue to use cylindrical coordinates with the $$z$$ axis being perpendicular to the plates. Equation \ref{m0068_eLaplace} in cylindrical coordinates is:
$\left[ \frac{1}{\rho} \frac{\partial}{\partial \rho} \left( \rho \frac{\partial}{\partial \rho} \right) + \frac{1}{\rho^2} \frac{\partial^2}{\partial \phi^2} + \frac{\partial^2}{\partial z^2} \right] V = 0$
or perhaps a little more clearly written as follows:
$\frac{1}{\rho} \frac{\partial }{\partial \rho} \left( \rho \frac{\partial V}{\partial \rho} \right) + \frac{1}{\rho^2} \frac{\partial^2 V}{\partial \phi^2} + \frac{\partial^2 V}{\partial z^2} = 0$
Since the problem has radial symmetry, $$\partial V/\partial \phi = 0$$. Since $$d \ll a$$, we expect the fields to be approximately constant with $$\rho$$ until we get close to the edge of the plates. Therefore, we assume $$\partial V/\partial \rho$$ is negligible and can be taken to be zero. Thus, we are left with $\frac{\partial^2 V}{\partial z^2} \approx 0 ~~ \mbox{for \rho \ll a} \label{m0068_eDE}$
The general solution to Equation \ref{m0068_eDE} is obtained simply by integrating both sides twice, yielding
$V(z) = c_1 z + c_2 \label{m0068_eVAC}$
where $$c_1$$ and $$c_2$$ are constants that must be consistent with the boundary conditions. Thus, we must develop appropriate boundary conditions. Let the node voltage at the negative ($$z=0$$) terminal be $$V_{-}$$. Then the voltage at the positive ($$z=+d$$) terminal is $$V_{-}+V_C$$. Therefore: These are the relevant boundary conditions. Substituting $$V(z=0) = V_{-}$$ into Equation \ref{m0068_eVAC} yields $$c_2 = V_{-}$$. Substituting $$V(z=+d) = V_{-}+V_C$$ into Equation \ref{m0068_eVAC} yields $$c_1 = V_C/d$$. Thus, the answer to the problem is
$V(z) \approx \frac{V_C}{d} z + V_{-} ~~ \mbox{for \rho \ll a} \label{eEP-PEPP1}$
Note that the above result is dimensionally correct and confirms that the potential deep inside a “thin” parallel plate capacitor changes linearly with distance between the plates.
Further, you should find that application of the equation $${\bf E} = - \nabla V$$ (Section 5.14) to the solution above yields the expected result for the electric field intensity: $${\bf E} \approx -\hat{\bf z}V_C/d$$. This is precisely the result that we arrived at (without the aid of Laplace’s Equation) in Section 2.2.
A reasonable question to ask at this point would be, what about the potential field close to the edge of the plates, or, for that matter, beyond the plates? The field in this region is referred to as a fringing field. For the fringing field, $$\partial V/ \partial \rho$$ is no longer negligible and must be taken into account. In addition, it is necessary to modify the boundary conditions to account for the outside surfaces of the plates (that is, the sides of the plates that face away from the dielectric) and to account for the effect of the boundary between the spacer material and free space. These issues make the problem much more difficult. When an accurate calculation of a fringing field is necessary, it is common to resort to a numerical solution of Laplace’s Equation. Fortunately, accurate calculation of fringing fields is usually not required in practical engineering applications.
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https://projecteuclid.org/search_result?type=index&q.a.author=Juncheng%20Wei
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### Infinite-time blow-up for the 3-dimensional energy-critical heat equation
del Pino, Manuel, Musso, Monica, and Wei, Juncheng
Analysis & PDE Volume 13, Number 1 (2020), 215-274.
Journal article
### On higher-dimensional singularities for the fractional Yamabe problem: A nonlocal Mazzeo–Pacard program
Ao, Weiwei, Chan, Hardy, DelaTorre, Azahara, Fontelos, Marco A., González, María del Mar, and Wei, Juncheng
Duke Mathematical Journal Volume 168, Number 17 (15 November 2019), 3297-3411.
Journal article
### Classification of blow-up limits for the sinh-Gordon equation
Jevnikar, Aleks, Wei, Juncheng, and Yang, Wen
Differential and Integral Equations Volume 31, Number 9/10 (September/October 2018), 657-684.
Journal article
### Nonlocal $s$-minimal surfaces and Lawson cones
Dávila, Juan, del Pino, Manuel, and Wei, Juncheng
Journal of Differential Geometry Volume 109, Number 1 (May 2018), 111-175.
Journal article
### Existence theorems of the fractional Yamabe problem
Kim, Seunghyeok, Musso, Monica, and Wei, Juncheng
Analysis & PDE Volume 11, Number 1 (2018), 75-113.
Journal article
### On rank-2 Toda systems with arbitrary singularities: local mass and new estimates
Lin, Chang-Shou, Wei, Jun-cheng, Yang, Wen, and Zhang, Lei
Analysis & PDE Volume 11, Number 4 (2018), 873-898.
Journal article
### Uniqueness and nondegeneracy of sign-changing radial solutions to an almost critical elliptic problem
Ao, Weiwei, Wei, Juncheng, and Yao, Wei
Advances in Differential Equations Volume 21, Number 11/12 (November/December 2016), 1049-1084.
Journal article
### Serrin’s overdetermined problem and constant mean curvature surfaces
Del Pino, Manuel, Pacard, Frank, and Wei, Juncheng
Duke Mathematical Journal Volume 164, Number 14 (1 November 2015), 2643-2722.
Journal article
### Classification of blowup limits for $\mathrm{SU}(3)$ singular Toda systems
Lin, Chang-Shou, Wei, Jun-cheng, and Zhang, Lei
Analysis & PDE Volume 8, Number 4 (2015), 807-837.
Journal article
### A pointwise inequality for the fourth-order Lane–Emden equation
Fazly, Mostafa, Wei, Jun-cheng, and Xu, Xingwang
Analysis & PDE Volume 8, Number 7 (2015), 1541-1563.
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http://math.stackexchange.com/questions/12769/convergence-of-sequences
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# Convergence of Sequences
Let $a_n$ be a sequence in $\mathbb{R}$, $\phi: \mathbb{N} \rightarrow \mathbb{N}$ a monotonically increasing function with $\phi (0)=0$. Show that
$\sum _{n=0}^{\infty } a_n$ converges $\Rightarrow \sum _{i=0}^{\infty } {(\sum _{j=\phi (i)}^{\phi (i+1)-1 }a_{j})}$ converges.
My notes: Can you use that ${(\sum _{j=\phi (i)}^{\phi (i+1)-1 }a_{j})}$ has to be a cauchy sequence and can be as small as you want? Certainly it will be smaller than $a_n$ for all $n$ bigger than some $N_e$
-
## 2 Answers
I suppose you meant $\phi$ is strictly increasing, otherwise the inner sum could be an empty sum.
Let $b_i=\sum_{j=\phi(i)}^{\phi(i+1)-1} a_j$. For any $\epsilon >0$, you can find $N$ such that $$|a_j+\cdots +a_{j+k}|<\epsilon$$ for all $j\ge N, k>0$. Let $I$ be such that $\phi(I)\ge N$. Then for all $i\ge I$ you have $$|b_i+\cdots +b_{i+k}|<\epsilon$$ for all $k>0$. This proves that your series is Cauchy and hence converges.
-
When you take a fixed N you get
$\sum _{i=0} ^{N} \sum _{j=\phi(i)} ^{\phi(i+1)-1} a_j = \sum_{j=0}^{j=\phi(N+1)-1} a_j$
so basically the new sequence (meaning the partial summations) is a subsequence of the original one.
-
If that step u wrote is true, I agree that the task is solved. However, it appears to me that the right sum is smaller. How can you change the index? – Listing Dec 2 '10 at 17:48
Think of the original sequence, when you add parentheses in some places. The function $\phi$ just tell you where you added them. The left sum is just adding first the elements in the parentheses and then add it to the total sum, while the right sum "forgets" the parentheses . – Prometheus Dec 2 '10 at 17:54
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https://www.techwhiff.com/learn/2-consider-the-following-equilibrium-cu2aq-pale/355796
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# 2. Consider the following equilibrium: Cu2+(aq) pale blue + 4NH3(aq) +[Cu(NH3)4]2+ (aq) colorless deep purple Would...
###### Question:
2. Consider the following equilibrium: Cu2+(aq) pale blue + 4NH3(aq) +[Cu(NH3)4]2+ (aq) colorless deep purple Would you expect to see an increase, no change, or a decrease in the purple color when: (a) the temperature of the system is increased (the reaction is endothermic). (b) a catalyst is added. (c) more aqueous NH3 is added to the equilibrium. (d) the pressure is increased. NaOH(aq) is added to the system, resulting in the precipitation of Cu(OH)2(s). _(1) (f) the volume of the system is increased.
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https://lists.w3.org/Archives/Public/w3c-wai-ig/2018JanMar/0045.html
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# Re: Math ML - Math expression
From: Michael A. Peters <[email protected]>
Date: Tue, 16 Jan 2018 12:11:43 -0800
Message-ID: <[email protected]>
It has been a long time since I have used MathML but I seem to recall
that there were two variants of MathML - the standard variant that most
people used and a variant intended to make it easier for people reading
the code to see what the expressions were. I seem to remember that LaTeX
to MathML converters (e.g. MathJax) only did the former and not the latter.
Since some browsers seem to have dropped raw MathML support maybe
MathJax and related technology need to be updated to make sure the
changed) LaTeX math notation is one of the more common ways math authors
create mathematical equations for visual typesetting.
It has literally been a decade since I last needed to use MathML so I'm
really out of touch on where it has gone. I do remember MathML syntax
itself was so confusing I personally just always did it in LaTeX and
used htlatex (I think that is what it was called) and just copied the
generated MathML to HTML (and it most certainly wasn't very accessible)
Hopefully its easier now, I'll be reading some of the posts. Hopefully
modern tools for doing it aren't based around Windows like a lot of
accessibility tools are.
On 01/16/2018 07:25 AM, sirisha gubba wrote:
> Thank you all for giving me your inputs on making math equations accessible.
>
> Siri
>
> On Sat, Jan 13, 2018 at 9:20 PM, sirisha gubba <[email protected]
> <mailto:[email protected]>> wrote:
>
> Can someone help me to find a tool to make math formulas accessible?
> When researched I found some tools on W3C site
> (https://www.w3.org/wiki/Math_Tools#Browsers
> <https://www.w3.org/wiki/Math_Tools#Browsers>) but don't know what
> to choose.
> If anyone has experience in this area can you please guide me?
>
> Thanks,
> Siri
>
>
Received on Tuesday, 16 January 2018 20:12:09 UTC
This archive was generated by hypermail 2.3.1 : Tuesday, 16 January 2018 20:12:10 UTC
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https://arxiv-export-lb.library.cornell.edu/abs/2103.04920v1
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hep-th
(what is this?)
# Title: Closed string deformations in open string field theory II: superstring
Abstract: This is the second paper of a series of three. We construct effective open-closed superstring couplings by classically integrating out massive fields from open superstring field theories coupled to an elementary gauge invariant tadpole proportional to an on-shell closed string state in both large and small Hilbert spaces, in the NS sector. This source term is well known in the WZW formulation and by explicitly performing a novel large Hilbert space perturbation theory we are able to characterize the first orders of the vacuum shift solution, its obstructions and the non-trivial open-closed effective couplings in closed form. With the aim of getting all order results, we also construct a new observable in the $A_\infty$ theory in the small Hilbert space which correctly provides a gauge invariant coupling to physical closed strings and which descends from the WZW open-closed coupling upon partial gauge fixing and field redefinition. Armed with this new $A_\infty$ observable we use tensor co-algebra techniques to efficiently package the whole perturbation theory necessary for computing the effective action and we give all order results for the open-closed effective couplings in the small Hilbert space.
Comments: 35 pages, no figures Subjects: High Energy Physics - Theory (hep-th) Cite as: arXiv:2103.04920 [hep-th] (or arXiv:2103.04920v1 [hep-th] for this version)
## Submission history
From: Carlo Maccaferri [view email]
[v1] Mon, 8 Mar 2021 17:32:09 GMT (31kb)
[v2] Mon, 13 Sep 2021 21:53:04 GMT (34kb)
Link back to: arXiv, form interface, contact.
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https://mdbootstrap.com/education/html/chapter-1-lesson-10/
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# HTML file paths
HTML File Paths
A file path describes the location of a file in a web site's folder structure.
File paths are used when linking to external files like:
• Web pages
• Images
• Style sheets
• JavaScripts
Examples:
Path Description
<img src="picture.jpg"> picture.jpg is located in the same folder as the current page
<img src="images/picture.jpg"> picture.jpg is located in the images folder in the current folder
<img src="/images/picture.jpg"> picture.jpg is located in the images folder at the root of the current web
<img src="../picture.jpg"> picture.jpg is located in the folder one level up from the current folder
Absolute File Paths
An absolute file path is the full URL to an internet file:
``````
<img src="https://mdbootstrap.com/img/logo/mdb192x192.jpg" alt="MDB Logo">
``````
Relative File Paths
A relative file path points to a file relative to the current page.
In this example, the file path points to a file in the images folder located at the root of the current web:
``````
<img src="/images/mdb192x192.jpg" alt="MDB Logo">
``````
In this example, the file path points to a file in the images folder located in the current folder:
``````
<img src="images/mdb192x192.jpg" alt="MDB Logo">
``````
In this example, the file path points to a file in the images folder located in the folder one level above the current folder:
``````
<img src="../images/mdb192x192.jpg" alt="MDB Logo">
``````
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http://tex.stackexchange.com/users/21441/ptech?tab=activity
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# Ptech
less info
reputation
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bio website location age member for 2 years, 1 month seen Jun 13 '13 at 6:34 profile views 5
# 55 Actions
Apr14 awarded Popular Question Mar1 awarded Tumbleweed Feb24 accepted Hyperref font selection problem with babel and french Feb22 comment Hyperref font selection problem with babel and french @LionelMANSUY no, installation is good and french loaded normally. Feb22 revised Hyperref font selection problem with babel and french edited tags Feb22 comment Hyperref font selection problem with babel and french @egreg Thanks, and I still don't know what to do with french and fontselection in forms. Feb22 revised Hyperref font selection problem with babel and french edited title Feb22 comment Hyperref font selection problem with babel and french Strange, tried again and it worked, maybe it saved wrongly because `! Package babel Error: You haven't loaded the option french yet. See the babel package documentation for explanation. Type H for immediate help. ... l.23 \select@language{french}` when I delete a language and recompile. And french broke font selection, yes. Feb22 comment Hyperref font selection problem with babel and french `\usepackage[english,russian]{babel}` or `\usepackage[russian,english]{babel}` Feb22 comment Hyperref font selection problem with babel and french Not only french, when I add one more lang to babel this textfont format function not works. Feb22 revised Hyperref font selection problem with babel and french added 116 characters in body; edited tags; edited title Feb22 awarded Custodian Feb22 reviewed Approve Hyperref font selection problem with babel and french Feb22 revised Hyperref font selection problem with babel and french added 796 characters in body Feb22 comment Hyperref font selection problem with babel and french Yes, I have this font installed. Feb22 asked Hyperref font selection problem with babel and french Feb21 revised Is it possible to replace empty space in form with dots? added 239 characters in body Feb20 revised Is it possible to replace empty space in form with dots? added 120 characters in body Feb20 comment Is it possible to replace empty space in form with dots? No, you don't understand. There is already \dotfill in text. I want to fill form with dots AFTER someone enters info. Feb20 revised Is it possible to replace empty space in form with dots? added 237 characters in body
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https://www.physicsforums.com/threads/derivatives-of-ln-of-summation.9968/
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Derivatives of ln of summation
1. Nov 30, 2003
mmwave
Summations and calculus gives me fits so please verify my results on these 2 issues:
1. Z = summation ( exp ( - B*E(s)) ) where the sum is over s
d/dB of ln(Z) = d/dB (ln (exp(-BEo) + exp(-BE1) + ... exp(-BEn))
= (exp(-BEo) + exp(-BE1) + ... exp(-BEn))^-1 +
(-E0*exp(-BEo) + -E1*exp(-BE1) + ... -En*exp(-BEn))
= summation ( E(s) * exp(-B*E(s)) / summation ( exp(-B*E(s))
which is also the average value of E when Prob(E(si)) = exp(-BE(si))
2. does d/dT of exp( -E/kT) = -E/k * exp(-E/kT) * -(1/T^2) =
E/k* 1/T^2 * exp(-E/kT) ?
If you're curious, these come up in Boltzmann statistics in thermal physics.
2. Nov 30, 2003
Ambitwistor
Looks fine to me.
3. Nov 16, 2011
Physcello
Hi, where did the last term come from in 2nd question?
Also i want to ask what is d/d(ni)[summation(ni*ln(ni))]? i:from 1 to r.
ni is n sub indice i
Similar Discussions: Derivatives of ln of summation
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https://socratic.org/questions/how-do-you-prove-cos-x-pi-6-sin-x-pi-6
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Trigonometry
Topics
# How do you prove Cos(x+pi/6)-sin(x+pi/6)?
Jan 17, 2017
$= \frac{\sqrt{3}}{2} \cos x - \frac{1}{2} \sin x - \frac{\sqrt{3}}{2} \sin x - \frac{1}{2} \cos x$
#### Explanation:
Use the formulas: $\cos \left(A + B\right) = \cos A \cos B - \sin A \sin B$ and
$\sin \left(A + B\right) = \sin A \cos B + \cos A \sin B$
$\cos \left(x + \frac{\pi}{6}\right) - \sin \left(x + \frac{\pi}{6}\right) = \left[\cos x \cos \left(\frac{\pi}{6}\right) - \sin x \sin \left(\frac{\pi}{6}\right)\right] - \left[\sin x \cos \left(\frac{\pi}{6}\right) + \cos x \sin \left(\frac{\pi}{6}\right)\right]$
$= \left[\cos x \left(\frac{\sqrt{3}}{2}\right) - \sin x \left(\frac{1}{2}\right)\right] - \left[\sin x \left(\frac{\sqrt{3}}{2}\right) + \cos x \sin \left(\frac{\pi}{6}\right)\right]$
$= \frac{\sqrt{3}}{2} \cos x - \frac{1}{2} \sin x - \frac{\sqrt{3}}{2} \sin x - \frac{1}{2} \cos x$
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https://socratic.org/questions/a-triangle-has-corners-at-3-2-6-7-and-5-8-what-is-the-radius-of-the-triangle-s-i
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Geometry
Questions Topics
# A triangle has corners at (3 , 2 ), (6 ,7 ), and (5 ,8 ). What is the radius of the triangle's inscribed circle?
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Feb 19, 2018
#### Answer:
The radius of the circle is 0.581
#### Explanation:
We determine the coordinates of the center of inscribed circle by investigation of the intersection of the angular bisectors.
Let,$A \equiv \left(3 , 2\right) , B \equiv \left(6 , 7\right) , \mathmr{and} C \equiv \left(5 , 8\right)$represent the vertices of the triangle ABC
Angular bisector atA:
A-=(3,2) B-=(6,7) C-=(5,8)
Slope of line AB is ${m}_{A B} = \frac{7 - 2}{6 - 3} = \frac{5}{3}$
Slope of line AB is ${m}_{A C} = \frac{8 - 2}{5 - 3} = \frac{6}{2} = 3$
Let the slope of the bisector be m
$\frac{m - \frac{5}{3}}{1 + m \times \frac{5}{3}} = \frac{3 - m}{1 + 3 \times m}$
$= \frac{3 m - 5}{3 + 5 m} = \frac{3 - m}{1 + 3 m}$
Cross multiplying
$\left(1 + 3 m\right) \left(3 m - 5\right) = \left(3 - m\right) \left(3 + 5 m\right)$
$3 m - 5 + 9 {m}^{2} - 15 m = 9 - 3 m + 15 m - 5 {m}^{2}$
$9 {m}^{2} + 5 {m}^{2} + 3 m - 15 m + 3 m - 15 m - 5 - 9 = 0$
$14 {m}^{2} - 24 m - 14 = 0$
Dividing by 14
${m}^{2} - \frac{12}{7} m - 1 = 0$
$m = 2.17 , m = - 0.46$
Equation of the bisector through A(3,2) is
$\frac{y - 2}{x - 3} = 2.17$
Simplifying
$y - 2 = 2.17 \left(x - 3\right)$
$y - 2 = 2.17 x - 6.51$
$y = 2.17 x - 4.51$
Angular bisector atB:
A-=(3,2)
B-=(6,7)
C-=(5,8)
Slope of line AB is ${m}_{A B} = \frac{7 - 2}{6 - 3} = \frac{5}{3}$
Slope of line BC is ${m}_{B C} = \frac{8 - 7}{5 - 6} = \frac{1}{-} 1 = - 1$
Let the slope of the bisector be m
$\frac{m - \frac{5}{3}}{1 + m \times \frac{5}{3}} = \frac{- 1 - m}{1 + \left(- 1\right) \times m}$
$= \frac{3 m - 5}{3 + 5 m} = \frac{- 1 - m}{1 - m}$
Cross multiplying
$\left(1 - m\right) \left(3 m - 5\right) = \left(- 1 - m\right) \left(3 + 5 m\right)$
$3 m - 5 - 3 {m}^{2} + 5 m = - 3 - 5 m - 3 m - 5 {m}^{2}$
$5 {m}^{2} - 3 {m}^{2} + 5 m + 3 m + 5 m + 3 m + 3 - 5 = 0$
$2 {m}^{2} + 16 m - 2 = 0$
Dividing by 2
${m}^{2} + 8 m - 1 = 0$
$m = 0.12 , m = - 8.12$
Equation of the bisector through B(6,7) is
$\frac{y - 7}{x - 6} = 0.12$
Simplifying
$y - 7 = 0.12 \left(x - 6\right)$
$y - 7 = 0.12 x - 0.75$
$y = 0.12 x + 6.25$
The lines $y = 2.17 x - 4.51$ and $y = 0.12 x + 6.25$ intersect at the center of the incircle
Equating rhs
$2.17 x - 4.51 = 0.12 x + 6.25$
$2.17 x - 0.12 x = 6.25 + 4.51$
$2.05 x = 10.76$
$x = \frac{10.76}{2.05}$
$x = 5.25$
$y = 2.17 x - 4.51$
$y = 2.17 \times 5.25 - 4.51$
$y = 11.39 - 4.51$
$y = 6.88$
$y = 0.12 x + 6.25$
$y = 0.12 \times 5.25 + 6.25 = 0.63 + 6.25$
$y = 6.88$
Verified
The coordinates of the centre of incircle is
$O \equiv \left(5.25 , 6.88\right)$
Slope of line AB
${m}_{A B} = \frac{5}{3}$
Point A is $A \equiv \left(3 , 2\right)$
Equation of the line AB is
$\frac{y - 2}{x - 3} = \frac{5}{3}$
$3 \left(y - 2\right) = 5 \left(x - 3\right)$
$3 y - 6 = 5 x - 15$
$5 x - 3 y + 6 - 15 = 0$
$5 x - 3 y - 9 = 0$
Center is $O \equiv \left(5.25 , 6.88\right)$
Tangent is $5 x - 3 y - 9 = 0$
The distance from O to the line AB is
given by
$| \frac{5 \times 5.25 - 3 \times 6.88 - 9}{\sqrt{{5}^{2} + {\left(- 3\right)}^{2}}} | = | \frac{- 3.39}{5.83} | = 0.581$
The radius of the circle is 0.581
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## anonymous 3 years ago Write the following value in standard notation. 4.25 x 10^6 425,000 4,250,000 425,610 425,000,000 Delete Cancel Submit
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@jazy
2. anonymous
• 3 years ago
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Is it 4.25 x 10^6
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• 3 years ago
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@SWAG
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• 3 years ago
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Yeah
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$4.25 \times 10^6=4250000$
6. anonymous
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10^6 = 10 * 10 * 10 * 10 * 10 * 10 = 1,000,000 1,000,000 * 4.25 = 4,250,000
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So is it A or B?
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4,250,000
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SWAG
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https://sciendo.com/article/10.2478/amns.2021.2.00219
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Journal Details
Format
Journal
eISSN
2444-8656
First Published
01 Jan 2016
Publication timeframe
2 times per year
Languages
English
Open Access
# Secure transmission of simultaneous wireless information and power transfer system for Internet of things
###### Accepted: 30 May 2022
Journal Details
Format
Journal
eISSN
2444-8656
First Published
01 Jan 2016
Publication timeframe
2 times per year
Languages
English
Introduction
As one of the core factors of 5G technology, the Internet of things (IoT) has a broad application prospect. IoT devices are generally powered by batteries but the battery capacity is limited, which restricts the working life of the whole network. Therefore, prolonging the working life of power supply is one of the urgent problems to be solved in the application of IoT, which can reduce the maintenance cost. Due to the excellent broadcasting characteristics of radio signals, simultaneous wireless information and power transfer (SWIPT) can transmit both information and energy, and provide users with stable power supply [13]. No matter how large the network develops, ensuring the information security of the system is always one of the eternal themes. Wireless channel has the characteristics of openness, which will lead to the leakage of user information in the SWIPT system. It is one of the research hotspots in the industry to ensure the secure transmission of information via SWIPT system. As an important supplement to high-level encryption technology, PLS technology has developed rapidly in recent years; it can ensure the communication security of the system with simple calculation [47], which provides a reference for solving the problem of information leakage in SWIPT system.
According to the different working principles, the SWIPT system can be divided into two types: one is TS-SWIPT which is easy to implement and has attracted extensive attention in the industry, and the other is PS-SWIPT [3]. In this paper, the physical layer security in this type of system is mainly studied. Jiahao [8] considers a scenario including a single antenna IR and multiple single antenna ERs, where ER is regarded as a potential eavesdropper. Through the optimal design of the scheme, the IR can be protected from eavesdropping when meeting the ER energy constraint. In other works the secure transmission scheme when multiple ERs jointly eavesdrop on IR is studied [9, 10]. Zuxiang and Lenan [11] expand the number of IR and ER antennas, and obtain good results by designing different transmit beams. The secrecy rate of IR can be maximised when the ER energy constraint is satisfied and the energy gain of ER can be maximised when the IR secrecy rate constraint is satisfied [11]. Considering the channel state of the transmitter, a robust transmit beam is designed by Aiqun and Guyye [12] and Zaishuang et al. [13] to reduce the impact of estimation error on security performance. Shiqiang et al. [14], Chu et al. [15] and Yiling and Pengcheng [16] introduced artificial noise and jointly transmitted beams to optimise the scheme, which can not only ensure the energy gain of ER, but also ensure the communication safety of IR [1416]. The research on PLS technology in SWIPT has just begun, and the related work is very limited.
This paper proposes an ‘information-energy’ dynamic switching opportunistic secure transmission scheme. First, a randomly distributed TS-SWIPT network including three factors of multi-cell, multi-user and multiple eavesdropper is established, which assumes that the user adopts a time-domain switching receiver that collects energy in a nonlinear model. Then, combined with the time-varying wireless channel, a dynamic information energy switching transmission scheme based on signal-to-interference noise ratio (SINR) threshold is proposed. If the signal-to-noise ratio (SNR) of the receiving end is higher than the preset threshold, private information will be transmitted to it, otherwise public information will be transmitted. Finally, the energy and information transmission performance of the scheme are comprehensively analysed.
System model
The SWIPT network mainly includes three parts: (1) several RC, (2) a large number of ECU and (3) PE. To make the working hours of IoT devices longer, the RC uses the specific time slot of the downlink to transmit energy for it. RC transmits private information such as control signaling to equipment in other time slots of downlink. Each RC can transmit energy and information to multiple ECUs at the same time. PE attempts to intercept private information between RC and ECU. It is assumed that each RC is configured with Mr antennas, and each ECU and PE is configured with a single antenna [17]. The hardware of the receiving end for IoT is usually relatively simple, so this paper adopts the TS receiver with low complexity. When the user switches to EH mode, it uses RF to DC circuit to convert the energy carried by RF signal into DC power storage. Consistent with the practical application, this paper uses NLM to simulate the energy conversion relationship of the circuit, and the relationship is shown in Eqs (1)–(4) as follows: $Pout=ψX−Y$ $ψ=M1+e−a(Pin−b)$ $X=eab1+eab$ $Y=Meab$ where M represents the maximum power that can be output in the circuit, and a and b represent parameters only related to the hardware circuit.
Combined with the working characteristics of the TS receiver, to avoid interference between users, this paper considers that RCt communicates with multiple access users in the way of time division multiple access. To make the analysis easier, assume that the number of access users of RCt is k, and number them according to the distance from each user to RCt. The schematic diagram of downlink TDMA communication model is shown in Figure 1.
As can be seen in Figure 1, the downlink cycle length is βT. Each downlink cycle is divided into k time slots on average, and the i-th downlink time slot is allocated to user i. Considering the low energy gain of users in non-exclusive time slots, a certain energy transmission interval is allocated in their exclusive time slots to ensure their energy gain. In fact, RG cannot strictly control user behaviour, and the information transmission in the system will be eavesdropped not only by external users, but also by internal users.
Opportunistic transmission scheme
The existing research shows that there will be no receiver that can make use of both the content and energy of the signal in practice. According to working principles, SWIPT system can be divided into TS type and PS type, so the SWIPT system can also be divided into two types, and the physical layer security characteristics of the two types of systems are different.
In this paper, the TS receiver whose operation is relatively simple is selected, so only the TS receiver is briefly introduced here. The receiver only needs to switch back and forth between the two circuits to receive energy and information at the same time. The working principle of the TS receiver is shown in Figure 2. Each receiver consists of two parts, the information processing module and the energy acquisition module, but only one module is in working state at any time.
It is assumed that all channels in this paper consider the influence of two factors at the same time: large-scale and small-scale fading. The model of large-scale fading is the standard path loss model, while the small-scale fading follows Rayleigh block fading. The channel vector is expressed as hx–α, where h represents the small-scale fading vector, and the channel hn corresponding to each antenna follows an independent and the same complex Gaussian random distribution; ∥x∥ represents the Euclidean distance between the two sides of the communication; and α indicates the path loss coefficient.
In the SWIPT system, the security requirements of WIT and WPT are completely different. WIT needs to ensure that the transmitted information is not eavesdropped, while WPT only relies on RF signals to carry energy without ensuring its security. TS-SWIPT system can realise both information transmission and energy transmission. In the traditional scheme, the downlink cycle is fixedly divided into two continuous intervals by the transmitter. In the actual scenario, the wireless channel is random. According to the traditional scheme, it cannot meet the different requirements of WIT and WPT in terms of reliability and security.
The core idea of the scheme is to divide the exclusive time slot of each user into several sub time slots. The interval with better channel quality is used to transmit information with higher security requirements, and the rest time is used to complete energy transmission with lower security requirements. Taking Ui as an example, the proposed scheme is compared with the traditional scheme. This scheme no longer limits the WIT and WPT to two independent and continuous intervals, respectively, but distributes them to different positions on the user’s exclusive time slot.
The quality of wireless signal is uneven due to its variable characteristics, so the sender needs to estimate the channel to obtain the real-time channel state. The quality of the channel is a relative standard and there is no clear definition, the threshold needs to be set to complete the discrimination. If the received SNR of the target user is used as the standard to evaluate the channel quality, the RC can also introduce it to switch the information transmission and energy transmission. The difference and connection between the traditional scheme and the scheme in this paper are shown in Figure 3.
It can be seen from Figure 4 that the scheme can solve the problems existing in the traditional scheme and the flow of the scheme is as shown in Figure 4. Compared with the traditional design, this scheme can realise the inherent allocation mode of WIT and WPT. This scheme selects the time slot with better legal channel quality to transmit private information, which increases the difference between two channels, so as to ensure the security of information transmission in SWPIT for IoT.
Performance analysis
Next, we need to analyse the performance of the proposed scheme which is mainly divided into two parts: information transmission performance and energy transmission performance. This section mainly analyses the performance of the transmission scheme proposed in the previous section. Because the wireless channel has a characteristic, that is, it is independent of each other on each sub time slot, when describing the average performance of the whole time slot, $tid$ can be considered as a whole. Assuming that the transmission power is Pr and the maximum ratio transmission strategy is adopted, the received SNR is as shown in Eqs (5) and (6): $yi(t)=Pr‖Li,r‖hiwi+ni(t)$ $SNRi=Pr‖hid‖2‖Li,r‖−αδ2$
Based on the proposed scheme, a special method is adopted to determine the content of the transmitted signal on the current sub time slot. By comparing the preset switching threshold with the real-time received SNR of the target user, the content of the transmitted signal on the current sub time slot is determined. When the SNR is lower than the switching threshold, the transmitting end switches to the energy transmission mode. Power transfer probability (PTP) can be expressed as a complementary function of transmission probability. When the energy transmission is turned on, the public signal is selected to complete the energy transmission, so there is no need to pay too much attention to its security and confidentiality. This paper only considers the energy income of internal users as the evaluation index of energy transmission performance. In the TDMA access mode, the scheme proposed in this paper enables internal users to collect energy in their own time slot and other user time slots.
Information transmission performance
This section focuses on three factors to investigate information transmission: (1) reliability, (2) security and (3) delay. When the receiving rate of the target user is lower than the target communication rate, the user cannot decode the information completely and correctly. At this time, transmission is interrupted, and the probability of this event is connection out probability (COP), which is taken as the evaluation index of reliability in this paper. When the receiving rate of the eavesdropper is higher than the redundancy rate, the eavesdropper can decode some confidential information. At this time, the transmission is safely interrupted, and the probability of this event is the security outage probability (SOP), which is taken as the evaluation index of safety in this paper. Since the scheme may cause a certain delay in information transmission, the information transmission probability (ITP) is taken as the evaluation index of delay and the higher the ITP is, the lower the delay.
To represent the impact of reliability, security and delay on comprehensive performance better, the definition of STP is proposed, which represents the total amount of data transmitted from private information to target users within a specified time. To obtain the STP of downlink and describe the comprehensive security performance of transmission, ITP, COP and SOP need to be solved.
Besides the target users, there are two kinds of non-target users who attempt to eavesdrop on the information, so the security of transmission is very important. However, considering the nature and behavioural characteristics of internal users, they will not conspire with external eavesdroppers to eavesdrop, so it is necessary for at least one eavesdropper to decode successfully to cause security interruption.
It is clear in this paper that although both internal users and eavesdroppers may have potential eavesdropping behaviours, there are essential differences in the nature of the two users. In addition, the energy characteristics of internal users determine that their eavesdropping behaviours have probability characteristics, which needs to be analysed differently from those of external eavesdroppers. Because the internal users themselves have the need of uplink communication, their primary goal is to collect energy to ensure their uplink transmission outside their own communication time slots. In other words, only when sufficient energy is collected can internal users become eavesdroppers out of curiosity to intercept the information of other users, without eavesdropping on information at any cost. Therefore, to analyse the security threats brought by internal users, we need to first analyse their curiosity.
On this basis, the eavesdropping behaviour of internal users in the system is considered. Although both internal users and eavesdroppers may have potential eavesdropping behaviour, the nature of their users is essentially different, and the energy characteristics of internal users determine the probability characteristics of their eavesdropping behaviour, which needs to be analysed differently from external eavesdroppers. Only when sufficient energy is collected can internal users be transformed into eavesdroppers out of curiosity to intercept the information of other users, rather than eavesdropping at any cost. To analyse the security threats brought by internal users to the system, we need to analyse their curiosity first.
Take Uj as an example to analyse the curiosity of internal users. First, the energy gain of the user in the whole downlink cycle is calculated, and then two energy thresholds are set according to the characteristics of the actual system. Based on the threshold, the probability that the user turns into an eavesdropper, that is, the probability of curiosity (PC) of the user is calculated.
Energy transmission performance
When the SNR is lower than the switching threshold, the transmitting end switches to the energy transmission mode. PTP can be expressed as a complementary function of transmission probability. When the energy transmission is turned on, the public signal is selected to complete the energy transmission, so there is no need to pay too much attention to its security and confidentiality. In this section, only the energy income of internal users is considered as the evaluation index of energy transmission performance. In the TDMA access mode, the transmission scheme proposed in this chapter enables internal users to complete energy collection in their own time slot and other user time slots.
Performance optimisation
When the value of switching threshold is relatively large and the RC transmits energy in most time slots, the IOT equipment has enough time to collect energy. If the received SINR in the real wireless environment is greater than the switching threshold, it indicates that the legal channel quality is good, the information transmission has high reliability and security and the equipment switches to the information transmission mode. However, due to the large SNR threshold, the downlink channel quality from RC to IOT equipment cannot meet the requirements of the equipment and cannot transmit private information, so there are few time slots used to transmit information. When the switching threshold is small, it can also be analysed according to the above statement. To make the performance of the system reach an optimal state, it is necessary to optimise the system and change its switching threshold.
When the handover threshold is optimised, there are two requirements to be met. One is that the energy constraints need to be met, and the other is that the reliability and safety of the system need to be met. On the premise that the two requirements are met, we should find ways to improve the comprehensive performance of the system. In other words, the system should be optimised through two aspects: to take some methods to improve the reliability of WIT, and to take methods to improve the security of STP. At the same time, two aspects should be considered: one is to consider the stability and efficiency of energy transmission, and the other is to take into account the reliability and security of information transmission.
From the previous analysis, it can be seen that the impact of switching threshold on information transmission and energy transmission performance is very significant. Therefore, to achieve the best performance of the system, the optimal design of switching threshold is very important. This paper mainly focuses on the security performance of information transmission, but the energy gain of users will affect the performance of uplink transmission, which is also very critical. Therefore, when optimising the handoff threshold, this paper takes the energy income of the user as the influence factor and multiplies it by the optimisation weight. The optimisation problem can be expressed by Eqs (7) and (8) as follows: $maxγiϖidl=ρξiΘ+(1−ρ)EiΘ$ $$\matrix{ {\mathop {\max }\limits_{{\gamma _i}} \quad \varpi _i^{dl} = \rho \xi _i^{\rm{\Theta }} + (1 - \rho )E_i^{\rm{\Theta }}} \cr }$$ $s.t.pcoi≤κ,psoi≤μ,γi≥0$ $$\matrix{ {s.t.\quad p_{co}^i \le \kappa ,p_{so}^i \le \mu ,{\gamma _i} \ge 0} \cr }$$
Constraints are reflected in the independent requirements of the system for the reliability and security of information transmission. To obtain the optimal solution of the above problems, inequality Eq. (9) holds as follows: $dϖidl(γi)dγi=0,d2ϖidl(γi)d2γi=0$
Based on obtaining the optimal solution, the influence of constraints on the feasible region of the problem needs to be considered. Combined with the monotonicity analysis results of COP and SOP above, it can be seen that both COP and SOP are monotonic decreasing functions of γi. The feasible region of the problem can be further reduced by finding the switching threshold that makes the equality sign of the constraint tenable. The final switching threshold can be determined by Eq. (10) as follows: $γiΔ={γi,γi≥ψiψi,else$ $$\gamma _i^{\rm{\Delta }} = \left\{ {\matrix{ {{\gamma _i},{\gamma _i} \ge {\psi _i}} \hfill \cr {{\psi _i},else} \hfill \cr } } \right.$$
Conclusion
In this paper, an opportunistic transmission scheme is proposed in the TS-SWIPT system. First, a model considering three factors of multi-cell, multi-user and multiple eavesdropper is established which assumes that the user adopts a time-domain switching receiver which collects energy in a nonlinear model. Then, combined with the time-varying wireless channel, a dynamic information energy switching transmission scheme based on SINR threshold is proposed. Finally, the energy and information transmission performance of the scheme are comprehensively analysed.
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Recommended articles from Trend MD
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https://ece.uwaterloo.ca/~agurfink/stqam.w21/syllabus
|
Lectures
2:30-3:50PM Tuesday, Wednesday, https://twitch.tv/profarie
1:00-2:20PM Tuesday, Wednesday, https://twitch.tv/profarie
By request
Instructor
Prof. Arie Gurfinkel, Office: HOME, first . last AT uwaterloo.ca, Office Hours: by appointment online
Nham Le
Textbook
No required textbook. Lecture slides, lecture notes, and reading material will be provided.
Course Description and Main Topics
This course will provide an introduction to software testing and quality assurance techniques. The students will learn a wide spectrum of techniques and tools that can be used to improve and evaluate software quality ranging from mature testing methodologies to cutting edge automated verification algorithms. Topics to be covered include: coverage criteria (graph, data-flow, and logic coverage), symbolic execution (static, dynamic, concolic), constraint solving (SMT), inductive invariants, automatic deductive verification, automatic invariant synthesis, and Software Model Checking.
The course will include programming assignments in Java/C/Python. Background in Compilers and Logic is useful, but is not required.
• Assignments: 35%
• Assignment 1: 10%
• Fuzz Battle: %5
• Assignment 2: 10%
• Assignment 3: 10%
• Quizzes: 20%
• Quiz 1: 10%
• Quiz 2: 10%
• Final Exam: 25%
• Project: 20%
All assignments, quizzes, and tests will be returned online.
All quizzes and tests are take home, open book, closed internet. Each online test will be time limited and must be completed within 3 days. That is, you can pick the best time to take the test, but once you start, you have to finish within the given time limit.
You must pass at least the two written tests and pass the assignments to pass the course. The final grade is computed using the following formula:
Project
There are three choices of projects. All three are available to undergraduate students (ECE453/CS447). The last two are available to both undergraduate and graduate students (CS647). Projects can be done in groups of 2. You must declare your project by the end of Week 8. All projects must be approved by the instructor.
The exact project deliverables depend on the project chosen. All projects must include approximately a 10 page report. The length of the report depends on the amount of code involved in the project (i.e., more code means shorter report).
Project (choice 0) (U only)
In the assignments, you will be implementing a symbolic execution engine and a verification engine for a small imperative language. The project is to implement additional advanced features for the language. Details of potential features will be available on Week 6.
Implement at least two features from the list in the symbolic execution engine for wlang
Features
• Concolic execution in EXE-style.
• Concolic execution in DART-style.
• A different exploration strategy. Potential choices are Depth First Search, Breadth First Search, A* Search, etc.
• Symbolic state merging. For example, following this post. TL;DR: symbolic states can be merged together by taking disjunction of their path conditions. Merging symbolic states reduces the number of symbolic states generated, at the expense of complicated path condition.
• Use incremental solving mode of Z3. During symbolic execution many similar queries are solved over and over again. Performance of symbolic execution can be improved by using incremental solving abilities of SMT solver that allow adding (and withdrawing) constraints between multiple calls. Details on available incremental interfaces are here. There are at least two different incremental solving interfaces (Scopes and Assumptions). Using each one counts for one implementation.
• Add support for bit-precise symbolic execution using the theory of bit-vectors.
• Implement verification condition generation using Weakest Pre-Condition. We will cover this in class in Week 10. Here is a link to the slides.
• Extend wlang with functions. This requires adding functions to the parser. We can help with that. This is a significant feature that counts for two. Extend the language to allow for functions specifications (requires and ensures from Dafny that we will cover in class).
• Extend wlang with references. A reference is a variable that is allocated on the heap. This requires changing the parser. We can help with that. This is a significant feature that counts for two.
Deliverables
• Code for the features. If the project is done in groups, request us to create a group repository for you. All code is to be submitted into the group repository (if the project is done in a group), or in your course repository (if the project is done independently)
• Test cases. You have to achieve complete statement and branch coverage for all the new code that you have written.
• Report. An approximately 10 page report (can be 9, can be 15, cannot be 5) describing the design decisions for your implementation, any theoretical foundations of your implementation, and your testing strategy. Report is to be submitted in PDF. Suggested style is LNCS. An Overleaf template is here. If you insist on using MS-WORD, a template is available here.
Project (choice 1) (U/G)
Throughout the course, we will learn of several verification techniques including fuzzing, symbolic execution, and deductive verification. In this project, you have to propose a program or an algorithm to verify with one of the techniques that we have studied in the course. The complexity of the artifact being verified will depend on the verification technique involved. The more complex the verification technique the simpler the artifact being verified can be.
Details
This project requires approval of the instructor. Talk to me. Sooner the better. Deadline is Week 10.
Deliverables
• Code and any other artifacts you produce. If the project is done in groups, request us to create a group repository for you. All code is to be submitted into the group repository (if the project is done in a group), or in your course repository (if the project is done independently)
• Report. An approximately 10 page report (can be 9, can be 15, cannot be 5) describing your experience, any theoretical foundations, any design decisions, and implementation that you had to do. Report is to be submitted in PDF. Suggested style is LNCS. An Overleaf template is here. If you insist on using MS-WORD, a template is available here.
Project (choice 2) (U/G)
Quality assurance and automated verification are active areas of research. In this project, you will conduct an independent study into a topic that is closely related to the material of the course but is not explicitly covered. The study must include reading at least two scientific papers. The outcome of the project can be an implementation of new technique or a report on the topic studied.
Details
This project requires approval of the instructor. Talk to me. Sooner the better. Deadline is Week 10.
Deliverables
• Report. An approximately 15 page report (can be 14, can be 20, cannot be 10) critically reviewing the paper that you have selected. Your review must be critical and in-depth. Simply repeating the papers verbatim is not sufficient. You must show that you have learned and understood something new. This can be done by contrasting different techniques, creating new examples, and, potentially, implementing the techniques. If your report involves implementation, the page limit of the report can be reduced. Report is to be submitted in PDF. Suggested style is LNCS. An Overleaf template is here. If you insist on using MS-WORD, a template is available here.
Course Policies
By registering for this class, students agree to the following class policies:
Independent work. All work turned in will be that of the individual student unless stated otherwise. Violations would result in zero credit to all students concerned. Policy 71 will be followed for any discovered cases of plagiarism.
Lateness. You have 2 days of lateness to use on assignment submissions throughout the term. Each day you hand in an assignment late consumes one of the days of lateness. If you consume all of your late days, assignments that are still late will get 0 marks. You can only hand in an assignment up to the time all assignments are returned. Missed assignments get 0 marks. For example, you may hand in A1 two days late and A2 on time, or you can hand in A1 one day late and A2 one day late.
Missed Quizzes. If you miss a quiz, you will receive 0 marks for the quiz. If you have a legitimate reason (at the discretion of the instructor) that you cannot take quiz, and obtain permission from the instructor a week in advance, the percentage for the quiz may be shifted to the final. No alternative quiz time will be provided.
University Policies
Academic Integrity. In order to maintain a culture of academic integrity, members of the University of Waterloo community are expected to promote honesty, trust, fairness, respect and responsibility. [Check http://www.uwaterloo.ca/academicintegrity for more information.]
Grievance. A student who believes that a decision affecting some aspect of his/her university life has been unfair or unreasonable may have grounds for initiating a grievance. Read Policy 70, Student Petitions and Grievances, Section 4, http://www.adm.uwaterloo.ca/infosec/Policies/policy70.htm. When in doubt please be certain to contact the departments administrative assistant who will provide further assistance.
Discipline. A student is expected to know what constitutes academic integrity [check http://www.uwaterloo.ca/academicintegrity] to avoid committing an academic offense, and to take responsibility for his/her actions. A student who is unsure whether an action constitutes an offense, or who needs help in learning how to avoid offenses (e.g., plagiarism, cheating) or about rules for group work/collaboration should seek guidance from the course instructor, academic advisor, or the undergraduate Associate Dean. For information on categories of offenses and types of penalties, students should refer to Policy 71, Student Discipline, http:://www.adm.uwaterloo.ca/infosec/Policies/policy71.htm. For typical penalties check Guidelines for the Assessment of Penalties, http://www.adm.uwaterloo.ca/infosec/guidelines/penaltyguidelines.htm.
Appeals. A decision made or penalty imposed under Policy 70 (Student Petitions and Grievances) (other than a petition) or Policy 71 (Student Discipline) may be appealed if there is a ground. A student who believes he/she has a ground for an appeal should refer to Policy 72 (Student Appeals) http://www.adm.uwaterloo.ca/infosec/Policies/policy72.htm.
Note for Students with Disabilities. The AccessAbility Services, located in Needles Hall, Room 1132, collaborates with all academic departments to arrange appropriate accommodations for students with disabilities without compromising the academic integrity of the curriculum. If you require academic accommodations to lessen the impact of your disability, please register with the AccessAbility Services at the beginning of each academic term.
Territorial Acknowledgement. The University of Waterloo acknowledges that much of our work takes place on the traditional territory of the Neutral, Anishinaabeg and Haudenosaunee peoples. Our main campus is situated on the Haldimand Tract, the land promised to the Six Nations that includes six miles on each side of the Grand River.
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|
https://melusine.eu.org/syracuse/pstricks/pst-solides3d/bonus/spirale_en_detail_eng.tex
|
# spirale_en_detail_eng.tex
\documentclass[fleqn]{article}
\usepackage{amsmath,amssymb}
\usepackage{pst-rubans}
\usepackage[a4paper]{geometry}
\begin{document}
\parindent=0pt
\parskip4pt
\section*{The Mathematical Details for using a Helix as a Spring \dots}
In Figure 1 you see a cylindrical spring (shape of a helix) with 10 windings, with
an equilibrium position height $h_0$. The equilibrium position radius is $r_0=\frac{d_0}{2}$.
In Figure 2 the spring is stretched -- its new height is $h_1$ and its new radius is $r_1 = \frac{d_1}{2}$.
\textbf{Questions}
\begin{itemize}
\item What's the length of the spring?
\item Now that the spring has a fixed length, what is the radius $r_1(h_0,\,r_0,\,h_1)$?
\end{itemize}
\psset{lightsrc=30 5 5,SphericalCoor,viewpoint=50 45 0,Decran=50,dZ=0.2,resolution=180}
\begin{pspicture}(-3,-5)(3,7)
\psframe(-1.5,-3.5)(1.5,7)
\psSolid[object=cylindre,r=1.2,h=0.2,ngrid=1 36](0,0,6)%
\pshelices[incolor=gray!75,R=0.5,h=6,hue=0.2 0.5,grid,RotY=180,spires=10,dZ=0.1](0,0,6)
\psPoint(0,1,6){O1}
\psPoint(0,1,0){O}
\pcline[linecolor=blue]{<->}(O1)(O)
\Aput{$h_0$}
\psSolid[object=cylindre,r=0.7,h=1,ngrid=4 36,fillcolor=blue](0,0,-1)
\psPoint(0,0,0){E1}
\psdot(E1)
\pnode(-0.5,3){I1}
\pnode(0.5,3){I2}
\psline[arrowsize=0.2]{<->}(I1)(I2)
\uput[l](I1){$d_0$}
\rput(0,-4){Figure 1}
\end{pspicture}
\begin{pspicture}(-3,-5)(3,7)
\psframe(-1.5,-3.5)(1.5,7)
\psSolid[object=cylindre,r=1.2,h=0.2,ngrid=1 36](0,0,6)%
\pshelices[incolor=gray!75,R=0.4,h=7,hue=0.2 0.5,grid,RotY=180,spires=10,dZ=0.1](0,0,6)
\psPoint(0,1,6){O1}
\psPoint(0,1,-1){O}
\pcline[linecolor=blue]{<->}(O1)(O)
\Aput{$h_1$}
\pnode(-0.4,2.5){I1}
\pnode(0.4,2.5){I2}
\psline[arrowsize=0.2]{<->}(I1)(I2)
\uput[l](I1){$d_1$}
\psSolid[object=cylindre,r=0.7,h=1,ngrid=4 36,fillcolor=blue](0,0,-2)
\psPoint(0,0,-1){E1}
\psdot(E1)
\psPoint(0,0,-1.5){E2}
\psPoint(0,0,-3){E3}
\psline[arrowsize=0.2,linecolor=red]{->}(E2)(E3)
\rput(0,-4){Figure 2}
\end{pspicture}
\textbf{Assumptions}
For simplicity, we assume that all windings are equidistant apart (the cylindrical spiral keeps the shape of a helix) and we ignore any physical properties of a 'solid' helix, e.~g. thickness of the helix line, mass of the spring, material, temperature, elasticity, torsion, etc., etc., and, of course, etc.
\newpage
\textbf{Calculations}
Let $z_0$ be the \textit{height} of one single winding, so $h_0 = n z_0$ is the \textit{total height} of a spring with $n$ windings.
\begin{pspicture}(-3,-1)(1,4)
\psset{lightsrc=10 -20 50,SphericalCoor,viewpoint=50 -20 20,Decran=50,unit=1}
\deffunction[algebraic]{helice}(t){2.6*cos(t)}{2.6*sin(t)}{0.4*t}
\psSolid[object=cylindre,r=2.6,h=3.3,action=draw,ngrid=6 36]%
\psSolid[object=courbe,
linecolor=blue,
linewidth=0.1,
resolution=360,
function=helice]%
\begin{pspicture}(-3,-1)(5,4)
\psline(0,0)(7,0)
\psline(0,0)(0,3.5)
\psline[linecolor=blue](7,0)(0,3.5)
\uput[-90](3.5,0){$2\pi r_0$}
\uput[180](0,1.75){$z_0$}
\uput[0](3.5,1.85){$l_0$}
\end{pspicture}
\textbf{A little trick:}
Roll the cylinder on the plane and trace the helix onto the plane. Thus the helix turns into a straight line. Drawing a right-angled triangle and using the Pythagorean Theorem (where the one cathetus is
the height $z_0$, the other cathetus is the circumference $2 \pi r_0$ of the cylinder and the hypotenuse is the length $l_0$ of the one winding) we can simply calculate the length of one winding.
The \textit{length of one single winding} is
\begin{equation}
l_0 = \sqrt{z_0^2 + 4\pi^2r_0^2}\label{l0}
\end{equation}
This gives the \textit{total length} of the spring
\begin{equation*}
L_0 = n l_0
\end{equation*}
Now we stretch the spring and calculate all that for Figure 2.
Let $z_1$ be the \textit{height} of one single winding, so $h_1 = n z_1$ is the \textit{total height} of the stretched spring with $n$ windings.
The \textit{length of one single winding} is
\begin{equation}
l_1 = \sqrt{z_1^2 + 4\pi^2r_1^2}\label{l1}
\end{equation}
This gives the \textit{total length} of the stretched spring
\begin{equation*}
L_1 = n l_1
\end{equation*}
Now that this is the same spring, the length is constant: $L_0=L_1$.
Equating \eqref{l0} and \eqref{l1} and solving for $r_1^2$, we get,
\begin{equation*}
r_1^2 = \frac{1}{4\pi^2n^2}h_0^2 - \frac{1}{4\pi^2n^2}h_1^2 + r_0^2
\end{equation*}
\newpage
\textbf{Setting up the oscillation}
Coordinate setup: The $h$-axis points downwards and the origin $h=0$ is defined as top of the spring.
Now let the spring do a harmonic oscillation with an \textit{amplitude}
$\hat{h} < h_0$ and let the oscillation start from the \textit{equilibrium
position} $h_0$ downwards with an \textit{angular frequency} $\omega = \frac{2\pi}{T}$ where $T$ is the \textit{period of oscillation}.
\begin{equation*}
h_1(t) = h_0 + \hat{h} \cdot \sin(\omega t)= h_0[1 + \frac{\hat{h}}{h_0}\sin(\omega t)]
\end{equation*}
This gives after some basic arithmetic
\begin{align*}
r_1(t) &= \sqrt{\frac{1}{4\pi^2n^2}h_0^2\{1 - [1 + \frac{\hat{h}}{h_0}\sin(\omega t)]^2\} + r_0^2}\\
&= \sqrt{r_0^2 - \frac{\hat{h}h_0}{4\pi^2n^2}\sin(\omega t)[2 + \frac{\hat{h}}{h_0}\sin(\omega t)] }
\end{align*}
\textbf{Results}
The more windings a spring has, the less $r_1(t)$ differs from $r_0$.
Now let's discuss the following two intervals of time
\begin{itemize}
\item $]0;\frac{T}{2}[$ -- enlarging the spring $l_1(t) > l_0$
\begin{equation*}
\end{equation*}
\item $]\frac{T}{2};T[$ -- shortening the spring $l_1(t) < l_0$
\begin{equation*}
\end{equation*}
\end{itemize}
Now if you calculate \textit{by hand} some explicit examples
choosing the variables $h_0,\,r_0,\,\hat{h}$, you will see that the
needed, when the stretching of the spring gets large. However that
disturbs the harmony of the oscillation and catapults the spring out
of its Hookian limitations -- these won't be the conditions for a
preferred harmonic oscillation. So there is no big error to set: $r_1(t) \approx r_0$
\newpage
\textbf{Example}
Here you see some excerpts of a harmonic oscillation ($n=10,\,h_0=5,\,r_0=1,5,\,\hat{h}=2$) including the \textit{radius correction} and there is no visible change for $r_1(t)$.
\psset{lightsrc=30 5 5,SphericalCoor,viewpoint=50 45 0,Decran=50,resolution=180}
\multido{\i=0+90}{5}{%
\begin{pspicture}(-1.35,-5)(1.35,7)
\pstVerb{%
/amplitude \i\space sin 0.4 mul 1 add 5 mul def
/radius \i\space sin 0.4 mul 1 add 2 exp neg 1 add 25 mul 4 div pi 2 exp div 100 div 1.5 2 exp add 0.5 exp def
}
\psframe(-1.4,-3.5)(1.4,7)
\psSolid[object=cylindre,r=1.2,h=0.2,ngrid=1 36](0,0,6)%
\psdot(E1)
\rput(0,-4){$t=\dfrac{\i}{360}T$}
\end{pspicture}
\textbf{The source code}
\footnotesize
\begin{verbatim}
\psset{lightsrc=30 5 5,SphericalCoor,viewpoint=50 45 0,Decran=50,resolution=180}
\multido{\i=0+90}{5}{%
\begin{pspicture}(-1.35,-5)(1.35,7)
\pstVerb{%
/amplitude \i\space sin 0.4 mul 1 add 5 mul def
/radius \i\space sin 0.4 mul 1 add 2 exp neg 1 add 25 mul 4 div pi 2 exp div 100 div 1.5 2 exp add 0.5 exp def
}
\psframe(-1.4,-3.5)(1.4,7)
\psSolid[object=cylindre,r=1.2,h=0.2,ngrid=1 36](0,0,6)
\rput(0,-4){$t=\dfrac{\i}{360}T$}
|
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|
https://questions.examside.com/past-years/jee/question/suppose-that-the-angular-velocity-of-rotation-of-earth-is-in-jee-main-physics-units-and-measurements-weuagzjktao9iewt
|
1
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
Suppose that the angular velocity of rotation of earth is increased. Then, as a consequence :
A
Weight of the object, everywhere on the earth, will increase.
B
Weight of the object, everywhere on the earth, will decrease.
C
There will be no change in weight anywhere on the earth.
D
Except at poles, weight of the object on the earth will decrease.
2
JEE Main 2018 (Offline)
+4
-1
A particle is moving in a circular path of radius $$a$$ under the action of an attractive potential $$U = - {k \over {2{r^2}}}$$ Its total energy is:
A
$$- {3 \over 2}{k \over {{a^2}}}$$
B
Zero
C
$$- {k \over {4{a^2}}}$$
D
$${k \over {2{a^2}}}$$
3
JEE Main 2018 (Offline)
+4
-1
A particle is moving with a uniform speed in a circular orbit of radius R in a central force inversely proportional to the nth power of R. If the period of rotation of the particle is T, then :
A
T $$\propto$$ Rn/2
B
T $$\propto$$ R3/2 for any n
C
T $$\propto$$ Rn/2 +1
D
T $$\propto$$ R(n+1)/2
4
JEE Main 2018 (Online) 15th April Morning Slot
+4
-1
A body of mass m is moving in a circular orbit of radius R about a planet of mass M. At some instant, it splits into two equal masses. The first mass moves in a circular orbit of radius $${R \over 2},$$ and the other mass, in a circular orbit of radius $${3R \over 2}$$. The difference between the final and initial total energies is :
A
$$- {{GMm} \over {2R}}$$
B
$$+ {{GMm} \over {6R}}$$
C
$${{GMm} \over {2R}}$$
D
$$- {{GMm} \over {6R}}$$
JEE Main Subjects
Physics
Mechanics
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Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
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EXAM MAP
Joint Entrance Examination
|
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|
https://nigerianscholars.com/past-questions/geography/question/270130/
|
Home » » Quartz, feldspar and mica are three principal minerals that can easily be seen i...
# Quartz, feldspar and mica are three principal minerals that can easily be seen i...
### Question
Quartz, feldspar and mica are three principal minerals that can easily be seen in?
A) basalt
B) coal
C) granite
D) limestone
|
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|
https://mathematica.stackexchange.com/questions/176883/solving-integro-differential-equation-with-boundary-condition-at-infinity?noredirect=1
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# Solving integro-differential equation with boundary condition at infinity
I wish to solve a differential equation that contains a hard-to-evaluate integral and to plot the solution in a range at least $r\in(0,10)$. The equation comes from a Hartree equation (Schroedinger equation). The solution must satisfy the boundary condition $u[\infty]=1$ but I don't know how to tell Mathematica to consider this constraint.
eps = 10^-5;
end = 12;
a = -74.04252664070837;
b = 208.01432471151327;
d = -65.08706834153939;
A = 1.56692098226;
gamma = 1;
chi = 9.697836405827061;
kst=6.03474; (* actually i don't know this value exactly this is the best up to now*)
j[x_, r_] = 2 A^2 r x
g0[x_, r_] = a + b/2 + 3 d/4 + A^2 (b + d) (x^2 + r^2) + d A^4 ((x^2 + r^2)^2 + 4 x^2 r^2)
g1[x_, r_] = j[x, r] (b + 2 d) + 4 d A^4 r x (r^2 + x^2)
f[x_] = x/Sqrt[x^2 + 2]
FNB[r_] := NIntegrate[(x^3/(2 + x^2) E^(-A^2 (r^2 + x^2)) (g0[x, r] BesselI[0, j[x, r]] -g1[x, r] BesselI[1, j[x, r]])), {x, 0, Infinity}]
Plot[FNB[r], {r, 0, 5}]
eqnNB = u''[r] + u'[r]/r - u[r]/r^2 + u[r] - chi*(u[r])^(5) - 2 (Pi)^(3/2)/A u[r] FNB[r] == 0;
SolNB = NDSolve[{eqnNB, u[eps] == 0, u'[eps] == kst}, {u}, {r, eps, end}];
R[r_] = u[r] /. SolNB;
PlotNB = Plot[R[r]^2, {r, eps, end}]
FNB2[r_] := NIntegrate[(x R[x]^2 E^(-A^2 (r^2 + x^2)) (g0[x, r] BesselI[0, j[x, r]] - g1[x, r] BesselI[1, j[x, r]])), {x, 0, Infinity}];
eqnNB2 = u''[r] + u'[r]/r - u[r]/r^2 + u[r] - chi*(u[r])^(5) - 2 (Pi)^(3/2)/A u[r] FNB2[r] == 0;
SolNB2 = NDSolve[{eqnNB, u[eps] == 0, u'[eps] == kst}, {u}, {r, eps,end}];
R2[r_] = u[r] /. SolNB2;
PlotNB2 = Plot[R2[r]^2, {r, eps, end}]
I tried to compute the integral FNB[r] at first with a trial function f[x] similar to the solution I want to get, so that the value of the integral doesn't change so much. The problem is that the solution I get from the first iteration doesn't satisfy the boundary condition (this is quite obvious since I didn't tell Mathematica to satisfy it...), and also I don't get any solution from the second iteration when I try to compute the integral FNB[r] with the previously found solution.
• Your code doesn't seem to meet your description, where's the iteration? Also, where's the definition of rst and yst? – xzczd Jul 8 '18 at 4:12
• @xzczd sorry, I've edited the code. The iteration is just another NDsolve to find the solution using the integral FNB2[r] computed using the solution found in the first iteraction SolNB – edinorog Jul 8 '18 at 9:47
• So the original FNB is NIntegrate[(x u[x]^2 E^(-A^2 (r^2 + x^2)) (g0[x, r] BesselI[0, j[x, r]] - g1[x, r] BesselI[1, j[x, r]])), {x, 0, Infinity}], right? – xzczd Jul 8 '18 at 10:27
• Yes, but at first I used a trial function x/Sqrt[x^2+2] to find the solution in the first iteration for NDsolve, otherwise it told me that the equation was delayed. I think it's a good compromise. – edinorog Jul 8 '18 at 10:30
• The asymptotic limit of the equation is u[r] - chi*u[r]^5 - (2 Pi)^(3/2)/A u[r] FNB[r] == 0. Hence, the asymptotic solution is approximately, ((1 - FNB[12] (2 Pi)^(3/2)/A)/chi)^.25, which is 2.13479, not 1 as in the article you cited. Until this discrepancy is resolved, there is no point to trying to solve the complete equation. – bbgodfrey Jul 8 '18 at 16:52
An iterative solution to the integro-differential equation, as requested by the OP, appears reasonable. Begin with
Off[InterpolatingFunction::dmval]
eps = 10^-5;
end = 12;
a = Rationalize[-74.04252664070837, 0];
b = Rationalize[ 208.01432471151327, 0];
d = Rationalize[-65.08706834153939, 0];
A = Rationalize[1.56692098226, 0];
chi = Rationalize[ 9.697836405827061, 0];
j[x_, r_] = 2 A^2 r x;
g0[x_, r_] = a + b/2 + 3 d/4 + A^2 (b + d) (x^2 + r^2) +
d A^4 ((x^2 + r^2)^2 + 4 x^2 r^2);
g1[x_, r_] = j[x, r] (b + 2 d) + 4 d A^4 r x (r^2 + x^2);
The first approximation to the integral is computed as
f[x_] = x/Sqrt[x^2 + 1/2];
FNB = Interpolation@Rationalize[Table[{r, E^(-A^2 (r^2 ))
NIntegrate[(x f[x]^2 E^(-A^2 ( x^2)) (g0[x, r] BesselI[0, j[x, r]] -
g1[x, r] BesselI[1, j[x, r]])), {x, 0, 30}]}, {r, 0, end, .1}], 0];
Note that all numerical quantities are rationalized, because subsequent NDSolve computations require high WorkingPrecision. (High WorkingPrecison is necessary, because this is a separatrix computation, which is extremely sensitive to initial conditions.) Note also that the initial guess for u[r], namely f[x_] = x/Sqrt[x^2 + 1/2], differs slightly from the initial guess in the question, because I felt that it would be a better first approximation, and it appears to be. Now, solve the resulting ODE for the next approximation to u[r], following the procedure described here.
eqnNB = u''[r] + u'[r]/r - u[r]/r^2 + u[r] - chi*(u[r])^(5) -
2 (Pi)^(3/2)/A u[r] FNB[r] == 0;
sp = ParametricNDSolveValue[{eqnNB, u[eps] == 0, u'[eps] == up0,
WhenEvent[u[r] > 12/10, {bool = 1, "StopIntegration"}],
WhenEvent[{u[r] < 8/10, u[r] < 0}, {bool = 0, "StopIntegration"}]},
u, {r, eps, end + 1}, {up0, wp0}, WorkingPrecision -> wp0,
Method -> "StiffnessSwitching",
Method -> {"ParametricSensitivity" -> None}, MaxSteps -> 100000];
bl = 1; bu = 10; imax = 200; wp = 75;
Row[{ProgressIndicator[Dynamic[ip], {0, imax}], " ",
ProgressIndicator[Dynamic[rm], {0, end}]}]
Do[bool = -1; bmiddle = (bl + bu)/2; s = sp[bmiddle, wp];
rm = s["Domain"][[1, 2]]; If[bool == 0, bl = bmiddle, bu = bmiddle];
ip = i; If[bool == -1, Return[]], {i, imax}] // AbsoluteTiming
N[bmiddle, wp]
Plot[{s[r], f[r]}, {r, eps, Min[rm, end]}, PlotRange -> All, AxesLabel -> {r, u},
ImageSize -> Large, LabelStyle -> {Black, Bold, Medium}]
The original guess, f[r] agrees well with the new approximation, s[r], for r > 3. Now, substitute s into the integral.
FNB1 = Interpolation@Rationalize[Table[{r, E^(-A^2 (r^2 ))
NIntegrate[(x Piecewise[{{s[x], eps < x < end}}, f[x]]^2 E^(-A^2 ( x^2))
(g0[x, r] BesselI[0, j[x, r]] - g1[x, r] BesselI[1, j[x, r]])),
{x, 0, 30}]}, {r, 0, end, .1}], 0];
and employ NDSolve as before to obtain the next approximation.
eqnNB1 = u''[r] + u'[r]/r - u[r]/r^2 + u[r] - chi*(u[r])^(5) -
2 (Pi)^(3/2)/A u[r] FNB1[r] == 0;
sp = ParametricNDSolveValue[{eqnNB1, u[eps] == 0, u'[eps] == up0,
WhenEvent[u[r] > 12/10, {bool = 1, "StopIntegration"}],
WhenEvent[{u[r] < 8/10, u[r] < 0}, {bool = 0, "StopIntegration"}]},
u, {r, eps, end + 1}, {up0, wp0}, WorkingPrecision -> wp0,
Method -> "StiffnessSwitching",
Method -> {"ParametricSensitivity" -> None}, MaxSteps -> 100000];
bl = 1; bu = 10; imax = 200; wp = 75;
Row[{ProgressIndicator[Dynamic[ip], {0, imax}], " ",
ProgressIndicator[Dynamic[rm], {0, end}]}]
Do[bool = -1; bmiddle = (bl + bu)/2; s1 = sp[bmiddle, wp];
rm = s1["Domain"][[1, 2]]; If[bool == 0, bl = bmiddle, bu = bmiddle];
ip = i; If[bool == -1, Return[]], {i, imax}] // AbsoluteTiming
N[bmiddle, wp]
Plot[{s1[r], s[r], f[r]}, {r, eps, Min[rm, end]}, PlotRange -> All,
AxesLabel -> {r, u}, ImageSize -> Large, LabelStyle -> {Black, Bold, Medium}]
This process can be iterated to obtain progressively more accurate approximations. Each iteration took about 15 minutes on my PC.
Addendum: Converged Iterative Solution
Good convergence can be achieved with the following code (with constants defined above).
s[0][x_] = x/Sqrt[x^2 + 1/4];
FNB[0] = Interpolation@Rationalize[Table[{r,
E^(-A^2 (r^2 )) NIntegrate[(x s[0][x]^2 E^(-A^2 x^2)
(g0[x, r] BesselI[0, j[x, r]] - g1[x, r] BesselI[1, j[x, r]])),
{x, 0, 20}]}, {r, 0, end, .1}], 0];
mmin = 1; mmax = 20; imax = 200; wp = 75;
Row[{Dynamic[m], " ", ProgressIndicator[Dynamic[ip], {0, imax}],
" ", ProgressIndicator[Dynamic[rm], {0, end}]}]
Do[eqnNB = u''[r] + u'[r]/r - u[r]/r^2 + u[r] - chi*(u[r])^(5) -
2 (Pi)^(3/2)/A u[r] (FNB[m - 1][r] + FNB[Max[m - 2, 0]][r])/2 == 0;
sp = ParametricNDSolveValue[{eqnNB, u[eps] == 0, u'[eps] == up0,
WhenEvent[u[r] > 11/10, {bool = 1, "StopIntegration"}],
WhenEvent[{u[r] < 9/10, u[r] < 0}, {bool = 0, "StopIntegration"}]}, u,
{r, eps, end + 1}, {up0, wp0}, WorkingPrecision -> wp0,
Method -> "StiffnessSwitching",
Method -> {"ParametricSensitivity" -> None}, MaxSteps -> 100000];
bl = 1; bu = 10;
Do[bool = -1; bmiddle = (bl + bu)/2; st = sp[bmiddle, wp]; rm = st["Domain"][[1, 2]];
If[bool == 0, bl = bmiddle, bu = bmiddle]; ip = i;
If[bool == -1, Return[]], {i, imax}];
s[m] = st; N[bmiddle, wp];
FNB[m] = Interpolation@Rationalize[Table[{r,
E^(-A^2 (r^2 )) NIntegrate[(x Piecewise[{{s[m][x], eps < x < end}},
s[0][x]]^2 E^(-A^2 ( x^2)) (g0[x, r] BesselI[0, j[x, r]] -
g1[x, r] BesselI[1, j[x, r]])), {x, 0, 30}]}, {r, 0, end, .1}], 0];,
{m, mmin, mmax}]
Plot[Evaluate@Table[s[m][r], {m, mmax - 5, mmax}], {r, eps, end},
PlotRange -> All, AxesLabel -> {r, u}, ImageSize -> Large,
LabelStyle -> {Black, Bold, Medium}]
Plot[Evaluate@Table[FNB[m][r], {m, mmax - 5, mmax}], {r, 0, end},
PlotRange -> All, AxesLabel -> {r, "FNB"}, ImageSize -> Large,
LabelStyle -> {Black, Bold, Medium}]
Convergence is very good for both the solution, u, and the integral, FNB. (The slight irregularity in FNBat large r is due to a slight boundary condition mismatch, which I shall fix as time permits.) The only significant difference in the revised code used here is that (FNB[m - 1][r] + FNB[Max[m - 2, 0]][r])/2 replaces FNB[m - 1][r] in eqnNB to improve numerical stability. Note that this computation required 6 hours on my pc. However, mmax was excessively large to assure convergence, and mmax == 14 could have been run in 4 hours.
Explanation of using WhenEvent
Integrating an ODE long distances along a separatrix is difficult, because the numerical solution can depart rapidly from the true solution due to small errors in the initial condition. One method of improving the accuracy of the initial conditions is to choose initial guesses (bl and bu in the answer above) that bracket the unknown true initial condition, and then systematically reducing the uncertainty in the initial guesses by doing calculations with initial conditions that bifurcate the distance between the guesses. So, it is necessary to stop a calculation when it obviously is departing from the separatrix, and to note whether the trial calculation is departing above or below. In the answer above, the separatrix is expected to be near 1, except at small r. So, {9/10, 11/10} are expected to bracket the separatrix, and WhenEvent is used to stop the calculation, when the solution moves from inside to outside that range. (Merely being outside that range does not stop the calculation, which is why I check for u < 0 to catch cases in which the solution never reaches the desired range in the first place.) For a solution asymptotically approaching 2, use {18/10, 22/10} or something of that sort. Setting these limits may take some experimentation. Ideally, the range selected should bracket the desired solution with only a modest margin of error, because a large margin of error means that more computer time is required to detect when a particular computation is leaving the expected range.
• Thanks a lot. I only don't really understand how to perform iterations. I simply repeated the part of your code from the definition of sp to the Plot with the substitutions sp→sp1,s→s1,eqnNB→eqnbNB1 ,FNB→FNB1 and rm→rm1 but now NDSolve solves the eqn just up to 0.3. What's the problem? Can you show me how you menage to perform the iterations? Simply I'm new to Mathematica and I don't understand that much your code. – edinorog Jul 9 '18 at 10:49
• @AleLenoci I have changed the initial values of bl and bu and made a few other changes to make the code more robust. – bbgodfrey Jul 9 '18 at 16:22
• Now using your code I can't get the right solution. Moreover I still don't understand how to perform the iteration and get your final plot...Could you please post the complete working code? thanks for the efforts – edinorog Jul 9 '18 at 17:03
• Thanks for the update @bbgodfrey. This method can work also for other similas ODEs or the parameters you set are all specific for this case? – edinorog Jul 9 '18 at 18:32
• @AleLenoci This method should work for similar ODEs. – bbgodfrey Jul 9 '18 at 19:13
We can not take the eps too small, because there is a stop because of the divergence of the solution. Empirically, I picked up eps = 0.005. Then there is a solution, but it is not like expected - it's a function similar to Bessel's function.
eps = 5*10^-3;end = 12;
a = 1.9123;
b = -28.9815;
d = 1;
A = 1.6;
gamma = 1;
chi = 3.5;
j[x_, r_] := 2 A^2 r x
g0[x_, r_] :=
a + b/2 + 3 d/4 + A^2 (b + d) (x^2 + r^2) +
d A^4 ((x^2 + r^2)^2 + 4 x^2 r^2)
g1[x_, r_] := j[x, r] (b + 2 d) + 4 d A^4 r x (r^2 + x^2)
U[0][x_] := x/Sqrt[x^2 + 2]
q[x_] := U[0][x]^2
FNB2 = Interpolation[
Table[{r,
NIntegrate[(q[x]*x*
Exp[-A^2 (r^2 + x^2)] (g0[x, r] BesselI[0, j[x, r]] -
g1[x, r] BesselI[1, j[x, r]])), {x, 0, Infinity}]}, {r, eps,
end, .005}]];
U[1] = NDSolveValue[{u''[r] + u'[r]/r - u[r]/r^2 + u[r] -
chi*(u[r])^(5) - (2 Pi)^(3/2)/A u[r]*FNB2[r] == 0,
u'[eps] == 1.1, u[eps] == 0}, u, {r, eps, end}]
{Plot[U[1][r], {r, eps, end}, PlotRange -> All],
Plot[FNB2[r], {r, eps, end}, PlotRange -> All]}
• thanks for the effort but as you said the solution doesn't fit boundary condition at infinity which is the key problem . I know from a paper that the solution should approach to 1 to infinity by a few dumped oscillations within the interval $(0,12)$. – edinorog Jul 8 '18 at 14:58
• Can you name the article (paper) or give a link? – Alex Trounev Jul 8 '18 at 15:46
• Sure, look here damtp.cam.ac.uk/user/ngb23/publications/nls2.pdf. It's Eq.22, look at the plot below where's plotted u[r]^2 – edinorog Jul 8 '18 at 16:19
• There is a difference between your equation and the equation (22). I made a change to the equation in my message, but the solution to the equation did not change qualitatively. – Alex Trounev Jul 9 '18 at 4:42
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https://www.ijcai.org/proceedings/2017/356
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# Joint Capped Norms Minimization for Robust Matrix Recovery
## Feiping Nie, Zhouyuan Huo, Heng Huang
Proceedings of the Twenty-Sixth International Joint Conference on Artificial Intelligence
Main track. Pages 2557-2563. https://doi.org/10.24963/ijcai.2017/356
The low-rank matrix recovery is an important machine learning research topic with various scientific applications. Most existing low-rank matrix recovery methods relax the rank minimization problem via the trace norm minimization. However, such a relaxation makes the solution seriously deviate from the original one. Meanwhile, most matrix recovery methods minimize the squared prediction errors on the observed entries, which is sensitive to outliers. In this paper, we propose a new robust matrix recovery model to address the above two challenges. The joint capped trace norm and capped $\ell_1$-norm are used to tightly approximate the rank minimization and enhance the robustness to outliers. The evaluation experiments are performed on both synthetic data and real world applications in collaborative filtering and social network link prediction. All empirical results show our new method outperforms the existing matrix recovery methods.
Keywords:
Machine Learning: Data Mining
Machine Learning: Learning Preferences or Rankings
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https://aviation.stackexchange.com/questions/25362/relationship-between-aircraft-thrust-and-jet-exhaust-velocity
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# Relationship Between Aircraft Thrust and Jet Exhaust Velocity? [closed]
What is the relationship between aircraft thrust and jet exhaust velocity & thrust and mass flow.
Actually, my question is how to reduce or decrease jet noise without decreasing the thrust ?
## closed as unclear what you're asking by FreeMan, Federico♦, fooot♦, mins, Ralph JFeb 18 '16 at 19:48
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.
• Welcome. You have two different questions, which are both broad. You should split your post into two different ones with appropriate titles and detail with type of engines your are asking for. There are already answers on the site, please explain what is missing, to get better answers, e.g. Why does the Boeing 787 engine nacelle exhaust have such an unusual shape? – mins Feb 18 '16 at 7:45
• And, you question appears to be essentially a duplicate of your last one. It would fit with the flow of SE much better to have edited your original question, which would spawn a series of comments helping you refine it to get it reopened. – FreeMan Feb 18 '16 at 13:58
• Though this post is a duplicate of the original, it does have an answer, as opposed to the (closed) original. Perhaps this question aught to be left open. – J Walters Feb 18 '16 at 15:38
$T$ = $\dot{m}_{e} v_{e} - \dot{m}_{o} v_{o} - (P_{e} - P_{o}) A_{e}$
where, $\dot{m}$ is the mass flow rate $v$ is the velocity, $P$ is the pressure and $A$ is the (exhaust) area. The subscripts 'o' and 'e' denote the freestream and exhaust values respectively.
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https://socratic.org/questions/a-high-school-athlete-runs-1-00-10-2-m-in-12-20-s-what-is-the-velocity-in-m-s-an
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Physics
Topics
# A high school athlete runs 1.00 * 10^2 m in 12.20 s. What is the velocity in m/s and km/h?
Jul 6, 2016
$8.20 m {s}^{-} 1$ (3sf) and $29.5 k m {h}^{-} 1$ (3sf)
#### Explanation:
In order to calculate the velocity we need both the distance travelled and the time taken to travel that distance. In this case we have both, I will start by converting the $1.00$ x ${10}^{2}$ into standard form which is $100$m
So $v = \frac{d}{t}$
$d = 100 m$ & $t = 12.20 s$
Substitute both these values into the equation:
$v = \frac{d}{t} = \frac{100 m}{12.20 s} = 8.20 m {s}^{-} 1$
I like to keep the units in the calculation to make working the units of velocity out easier.
Now we know the velocity in $m {s}^{-} 1$. To calculate the speed in $k m {h}^{-} 1$ we need to convert both the $m$ & $s$, this can be done in multiple ways. However we know that $1000 m$ = $1 k m$ and $1$hour = $3600$seconds.
Therefore we need to multiply our answer by: $\frac{1000 m}{3600 s}$ So...
$v = 8.20 m {s}^{-} 1$ x$3.6 = 29.5 k m {h}^{-} 1$
Note: I retained the non-rounded value in the calculator through the calculations, this will improve your accuracy and avoid rounding error.
##### Impact of this question
5467 views around the world
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http://electronics.stackexchange.com/questions/111844/question-about-current-output-of-a-dc-dc-stepdown-converter
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# Question about current output of a DC-DC stepdown converter
If we have a solar panel of 5V and we want to keep voltage on the output to 3V, what current we are getting on the output? The same as in the input? Or a different one?
-
$P_{out} = P_{in} \cdot 80\%$
$3I_{out} = 5I_{in} \cdot 0.8$
$I_{out} = 1.33I_{in}$
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https://scicomp.stackexchange.com/questions/31205/incorporating-a-potential-barrier-in-a-wave-packet-simulation-fourier-transform
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Incorporating a potential barrier in a wave-packet simulation (Fourier Transform method)
I'm trying to simulate the scattering of a wave-packet at a potential barrier in Python. I'm using a Fourier Transform method (not sure if its the same as the Split-Step method), where I apply Fourier Transform on my initial wavepacket (plane wave in a gaussian envelope) to get the wavefunction in momentum-space: $$\phi(k) = \int^{\infty}_{-\infty} \psi(x) e^{ikx} dx$$ I then calculate the dispersion term, $$\omega$$, at each $$k$$ value, $$\omega = \frac{\hbar k^2}{2m}$$. I can then incorporate the time-evolution operator $$e^{-i\omega t}$$. This allows me to obtain $$\psi(x)$$ at a given time:
$$\psi(x,t) = \int^{\infty}_{-\infty} \phi(k) e^{-ikx}e^{-i\omega t}$$ which I achieve through an Inverse Fourier Transform of $$\phi(k)e^{-i\omega t}$$.
My wavepacket moves as expected, but I am now trying to incorporate a potential barrier. To start, I am trying to get my wave-packet to reflect off of a barrier (like a particle in a box).
I'm a bit unsure of how to implement this into my code. This problem is usually described by having both a incoming and reflected wave in the region before the barrier, so I have implemented a 'reflected' wave-packet which is simply a mirror image of the initial wave-packet with its amplitudes reversed. This can be manipulated to simulate the wave reflecting off the barrier but I'm wondering if there is a more trivial solution.
Questions:
• Is there a way to incorpate reflection/transmission at a barrier using my method of propagating the wave-packet?
• I've seen this problem solved using a finite difference method to solve the Schrodinger equation instead, is there an advantage of using that method?
• I think that you need to find the wavefunctions for your potential barrier. Then do a convolution with your spectrum. – nicoguaro Mar 9 at 15:42
• So define a function for my potential barrier, Fourier Transform it and then convolve with my wavepacket in k-space? Thanks for the suggestion! – FeelsToWaltz Mar 13 at 11:34
The neat thing about Fourier codes is that you can achieve very high order derivatives and if you are describing physics which is about waves, then the trigonometric base functions are a good choice. You also have a reasonably fast transform in $$\mathcal O(n\log(n)$$.
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http://www.ck12.org/book/CK-12-Physics---Intermediate/section/14.0/
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<img src="https://d5nxst8fruw4z.cloudfront.net/atrk.gif?account=iA1Pi1a8Dy00ym" style="display:none" height="1" width="1" alt="" />
# Chapter 14: Thermodynamics
Difficulty Level: At Grade Created by: CK-12
Chapter Outline
### Chapter Summary
1. The ideal gas law states \begin{align*}PV=nRT\end{align*} where \begin{align*}P\end{align*} is pressure, \begin{align*}V\end{align*} is volume, \begin{align*}n\end{align*} is the number of moles of substance, \begin{align*}R\end{align*} is the universal gas constant and \begin{align*}T\end{align*} is temperature.
2. Thermodynamics is the study of processes in which energy is transferred by heat and work.
3. In an isothermal process, temperature is constant
4. In an isochoric process, volume is constant
5. In an isobaric process, pressure is constant
6. In an adiabatic process, no heat flows into or out of the system
7. The first law of thermodynamics: The change in the internal energy of a closed system is equal to the heat into (or out of) a system plus the work done on the system (or by the system).
\begin{align*}\Delta U=Q+W,\Delta U\end{align*} is the change in internal energy of the system, \begin{align*}Q\end{align*} is the heat, and \begin{align*}W\end{align*} the work.
8. The second law of thermodynamics describes the direction in which physical phenomena can occur.
Statements describing the second law:
a. Heat can flow spontaneously from hot to cold but never from cold to hot.
b. No heat machine is 100% efficient.
The most general statement of the second law:
For all natural processes, the total entropy of a system increases.
9. The efficiency of an actual heat engine can be expressed as
\begin{align*}e=\left(1-\frac{Q_L}{Q_H}\right) \times 100 \end{align*}
The high temperature thermal energy is \begin{align*}Q_H\end{align*} and the low temperature thermal energy is \begin{align*}Q_L\end{align*}.
10. The efficiency of a Carnot engine can be expressed as
\begin{align*}e=\left(1-\frac{T_L}{T_H}\right) \times 100 \end{align*}
The high operating temperature of the Carnot engine is \begin{align*}T_H\end{align*} and the low operating temperature of the Carnot engine \begin{align*}T_L\end{align*}.
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https://shiyuzhao.wordpress.com/2011/04/13/image-points-and-image-lines-two-point-of-view/
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In a previous post, I talked about the image points and image lines. In this post, I will talk about how to interpret the image geometry which is different from the geometry we learned before.
• Point of view I: good, easy
Let an image point with coordinates $(x,y)$. A line passing the point is
$ax+by+c=0$
Hence we denote $m=[x,y,1]^T$ as an image point and $l=[a,b,c]^T$ as an image line. Then we know:
a) a point is on a line iff $l^Tm=0$
b) the line passing two points is $l=m_1\times m_2$
c) the intersection point of two lines is $m\sim l_1 \times l_2$
Remark: This point of view is quite easy. No need to care what happens outside the image plane.
• Point of view II: a 3D interseption
Image point: The formula of the normalized image plane is $z=1$. So the 3D coordinates of a point $(x,y)$ on the image plane is $[x,y,1]^T$.
Image Line: A line in the image plane can be treated as the intersection line between a plane $\pi$ passing through the origin and plane $z=1$. Note any plane $\pi$ passing through the origin is uniquely determined by its norm vector $l$. Hence any vector
$l\Rightarrow \pi \Rightarrow$ intersect with plane $z=1\Rightarrow$ an image line
Any points $m$ on the image line must have $l^Tm=0$ since $l$ is orthogonal to all vectors in the plane $\pi$
Remark: here we interpret them in 3D camera reference frame.
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https://www.physicsforums.com/threads/on-numerical-calculation-of-lift-force-via-potential-flow.99089/
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# On numerical calculation of Lift Force via Potential Flow
1. Nov 8, 2005
### Clausius2
Imagine:
I want to compute numerically a POTENTIAL STEADY and INCOMPRESSIBLE flow over an airfoil. The set up of the problem is:
$$\nabla^2\phi=0$$
$$\nabla\phi \cdot \overline{n}\big)_{x=surface}=0$$ no normal velocity component on the airfoil surface.
$$\nabla \phi=\overline{U_\infty}$$ as $$x\rightarrow\infty$$ external flow at large distances.
The three main questions which arise are the next:
i) Is it possible to obtain an steady solution of this stuff?
ii) Am I going to obtain any Lift force?. Why?
Thanx for participating in this discussion.
Can you offer guidance or do you also need help?
Draft saved Draft deleted
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https://askpunters.com/n75jhsk/8711c8-selenic-acid-uses
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Is oxidized to selenic acid by strong oxidizing agents. Its structure is similar to that of the Sulphurous acid . It is an oxoacid of selenium, and its structure is more accurately described as (HO)2SeO2. Uses. Alternative procedures use copper sulfate and phosphoric acid instead. Selenious Acid Injection, USP is a sterile, non-pyrogenic, clear, colorless solution intended for use as a trace element and additive to intravenous solutions for parenteral nutrition. $$SeO_2+H_2O_2\rightarrow H_2SeO_4$$ Serves as an oxidizing agent. Each mL contains 60 mcg selenium present as 98 mcg of selenious acid and Water for Injection q.s. Oxidizes many organic substances. It is a colorless compound. Selenic acid is the inorganic compound with the formula H2SeO4. The major use is in protecting and changing the color of steel, especially steel parts on firearms. Reacts exothermically with many reducing agents including hydroiodic acid, sulfurous acid, sodium hyposulfite, hydroxylamine salts, hydrazine salts, hypophosphorous acid, phosphorous acid [Merck]. Selenic acid is a strong dibasic acid with the formula H 2 SeO 4.It can be manufactured by oxidising selenium compounds in lower oxidation states. The so-called cold-bluing process uses selenous acid, copper(II) nitrate, and nitric acid to change the color of the steel from silver-grey to blue-grey or black. He Selenious acid Is an inorganic compound of formula H 2 SW 3 Which stands out for being the main oxacid of selenium (the other is selenic acid). The compound is prepared by dissolving selenium oxide in hot water and then allowed to cool. One of the methods includes oxidising selenium dioxide with hydrogen peroxide. Although it has few uses, its derivative sodium selenate is used in the production of glass and animal feeds.
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https://worldwidescience.org/topicpages/r/ross+sea+drift.html
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#### Sample records for ross sea drift
1. Victoria Land, Ross Sea, and Ross Ice Shelf, Antarctica
Science.gov (United States)
2002-01-01
On December 19, 2001, MODIS acquired data that produced this image of Antarctica's Victoria Land, Ross Ice Shelf, and the Ross Sea. The coastline that runs up and down along the left side of the image denotes where Victoria Land (left) meets the Ross Ice Shelf (right). The Ross Ice Shelf is the world's largest floating body of ice, approximately the same size as France. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC
2. Variability and Trends in Sea Ice Extent and Ice Production in the Ross Sea
Science.gov (United States)
Comiso, Josefino; Kwok, Ronald; Martin, Seelye; Gordon, Arnold L.
2011-01-01
Salt release during sea ice formation in the Ross Sea coastal regions is regarded as a primary forcing for the regional generation of Antarctic Bottom Water. Passive microwave data from November 1978 through 2008 are used to examine the detailed seasonal and interannual characteristics of the sea ice cover of the Ross Sea and the adjacent Bellingshausen and Amundsen seas. For this period the sea ice extent in the Ross Sea shows the greatest increase of all the Antarctic seas. Variability in the ice cover in these regions is linked to changes in the Southern Annular Mode and secondarily to the Antarctic Circumpolar Wave. Over the Ross Sea shelf, analysis of sea ice drift data from 1992 to 2008 yields a positive rate of increase in the net ice export of about 30,000 sq km/yr. For a characteristic ice thickness of 0.6 m, this yields a volume transport of about 20 cu km/yr, which is almost identical, within error bars, to our estimate of the trend in ice production. The increase in brine rejection in the Ross Shelf Polynya associated with the estimated increase with the ice production, however, is not consistent with the reported Ross Sea salinity decrease. The locally generated sea ice enhancement of Ross Sea salinity may be offset by an increase of relatively low salinity of the water advected into the region from the Amundsen Sea, a consequence of increased precipitation and regional glacial ice melt.
3. The South Pole and the Ross Sea
Science.gov (United States)
2002-01-01
This image shows a rare clear view of the South Pole (lower right) and the Ross Sea, Antarctica. The Sea-viewing Wide Field-of-view Sensor (SeaWiFS) acquired the scene on December 26, 2001. The geographic South Pole is located in the center of Antarctica, at an altitude of 2,900 meters (9,300 feet). It rests on a continent-wide ice sheet that is 2,870 m thick, with the underlying bedrock only 30 m (98 feet) above sea level. The ice underlying the South Pole is as much as 140,000 years old, and is currently accumulating at about 82 cm (32 inches) per year. Roughly 2,500 km (1,550 miles) away is the green water of the Ross Sea, which indicates the presence of large numbers of phytoplankton. This is a highly productive part of the world's oceans. Also note the ice gathered around McMurdo Sound, seen toward the lefthand shoreline of the Ross Sea, at the edge of the Ross Ice Shelf. According to National Science Foundation researchers, this ice is making it difficult for penguins to reach their food supply. Separating the continental Antarctic ice sheet from the Ross Sea are the Queen Maud Mountains and the Ross Ice Shelf. Image courtesy the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE
4. Phenolic compounds in Ross Sea water
Science.gov (United States)
Zangrando, Roberta; Barbaro, Elena; Gambaro, Andrea; Barbante, Carlo; Corami, Fabiana; Kehrwald, Natalie; Capodaglio, Gabriele
2016-04-01
Phenolic compounds are semi-volatile organic compounds produced during biomass burning and lignin degradation in water. In atmospheric and paleoclimatic ice cores studies, these compounds are used as biomarkers of wood combustion and supply information on the type of combusted biomass. Phenolic compounds are therefore indicators of paleoclimatic interest. Recent studies of Antarctic aerosols highlighted that phenolic compounds in Antarctica are not exclusively attributable to biomass burning but also derive from marine sources. In order to study the marine contribution to aerosols we developed an analytical method to determine the concentration of vanillic acid, vanillin, p-coumaric acid, syringic acid, isovanillic acid, homovanillic acid, syringaldehyde, acetosyringone and acetovanillone present in dissolved and particle phases in Sea Ross waters using HPLC-MS/MS. The analytical method was validated and used to quantify phenolic compounds in 28 sea water samples collected during a 2012 Ross Sea R/V cruise. The observed compounds were vanillic acid, vanillin, acetovanillone and p-coumaric acid with concentrations in the ng/L range. Higher concentrations of analytes were present in the dissolved phase than in the particle phase. Sample concentrations were greatest in the coastal, surficial and less saline Ross Sea waters near Victoria Land.
5. Early Winter Sea Ice Dynamics in the Ross Sea from In Situ and Satellite Observations
Science.gov (United States)
Maksym, T.; Ackley, S. F.; Stammerjohn, S. E.; Tison, J. L.; Hoeppner, K.
2017-12-01
The Ross Sea sea ice cover is one of the few regions of the cryosphere that have been expanding in recent decades. However, 2017 saw a significantly delayed autumn ice advance and record low early winter sea ice extent. Understanding the causes and impacts of this variability has been hampered by a lack of in situ observations. A winter cruise into the Ross Sea in April-June 2017 provided some of the only in situ winter observations of sea ice processes in this region in almost 20 years. We present a first look at data from arrays of drifting buoys deployed in the ice pack and outflow from these polynyas, supplemented by a suite of high-resolution synthetic aperture radar (SAR) data. Additional observations included high-resolution sonar imagery of ice deformation features from an autonomous underwater vehicle, shipboard visual observations of sea ice properties, and in situ measurements of snow and thickness and structural properties. These data show that the delay in ice advance led to a thin, highly dynamic sea ice pack, with substantial ice production and export from the Ross Ice Shelf and Terra Nova Bay polynyas. Despite these high rates of ice production, the pack ice remained thin due to rapid export and northward drift. Compared to the only prior winter observations made in 1995 and 1998, the ice was thinner, with less ridging and snow cover, reflecting a younger ice cover. Granular ice was less prevalent than in these prior cruises, particularly in the outer pack, likely due to less snow ice formation and less pancake ice formation at the advancing ice edge. Despite rapid basal ice growth, the buoy data suggest that deformation may be the dominant mechanism for sea ice thickening in the pack once an initial ice cover forms.
6. Western Ross Sea continental slope gravity currents
Science.gov (United States)
Gordon, Arnold L.; Orsi, Alejandro H.; Muench, Robin; Huber, Bruce A.; Zambianchi, Enrico; Visbeck, Martin
2009-06-01
Antarctic Bottom Water of the world ocean is derived from dense Shelf Water that is carried downslope by gravity currents at specific sites along the Antarctic margins. Data gathered by the AnSlope and CLIMA programs reveal the presence of energetic gravity currents that are formed over the western continental slope of the Ross Sea when High Salinity Shelf Water exits the shelf through Drygalski Trough. Joides Trough, immediately to the east, offers an additional escape route for less saline Shelf Water, while the Glomar Challenger Trough still farther east is a major pathway for export of the once supercooled low-salinity Ice Shelf Water that forms under the Ross Ice Shelf. The Drygalski Trough gravity currents increase in thickness from ˜100 to ˜400 m on proceeding downslope from ˜600 m (the shelf break) to 1200 m (upper slope) sea floor depth, while turning sharply to the west in response to the Coriolis force during their descent. The mean current pathway trends ˜35° downslope from isobaths. Benthic-layer current and thickness are correlated with the bottom water salinity, which exerts the primary control over the benthic-layer density. A 1-year time series of bottom-water current and hydrographic properties obtained on the slope near the 1000 m isobath indicates episodic pulses of Shelf Water export through Drygalski Trough. These cold (34.75) pulses correlate with strong downslope bottom flow. Extreme examples occurred during austral summer/fall 2003, comprising concentrated High Salinity Shelf Water (-1.9 °C; 34.79) and approaching 1.5 m s -1 at descent angles as large as ˜60° relative to the isobaths. Such events were most common during November-May, consistent with a northward shift in position of the dense Shelf Water during austral summer. The coldest, saltiest bottom water was measured from mid-April to mid-May 2003. The summer/fall export of High Salinity Shelf Water observed in 2004 was less than that seen in 2003. This difference, if real
7. The Ross Sea Dipole - temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years
Science.gov (United States)
Bertler, Nancy A. N.; Conway, Howard; Dahl-Jensen, Dorthe; Emanuelsson, Daniel B.; Winstrup, Mai; Vallelonga, Paul T.; Lee, James E.; Brook, Ed J.; Severinghaus, Jeffrey P.; Fudge, Taylor J.; Keller, Elizabeth D.; Baisden, W. Troy; Hindmarsh, Richard C. A.; Neff, Peter D.; Blunier, Thomas; Edwards, Ross; Mayewski, Paul A.; Kipfstuhl, Sepp; Buizert, Christo; Canessa, Silvia; Dadic, Ruzica; Kjær, Helle A.; Kurbatov, Andrei; Zhang, Dongqi; Waddington, Edwin D.; Baccolo, Giovanni; Beers, Thomas; Brightley, Hannah J.; Carter, Lionel; Clemens-Sewall, David; Ciobanu, Viorela G.; Delmonte, Barbara; Eling, Lukas; Ellis, Aja; Ganesh, Shruthi; Golledge, Nicholas R.; Haines, Skylar; Handley, Michael; Hawley, Robert L.; Hogan, Chad M.; Johnson, Katelyn M.; Korotkikh, Elena; Lowry, Daniel P.; Mandeno, Darcy; McKay, Robert M.; Menking, James A.; Naish, Timothy R.; Noerling, Caroline; Ollive, Agathe; Orsi, Anaïs; Proemse, Bernadette C.; Pyne, Alexander R.; Pyne, Rebecca L.; Renwick, James; Scherer, Reed P.; Semper, Stefanie; Simonsen, Marius; Sneed, Sharon B.; Steig, Eric J.; Tuohy, Andrea; Ulayottil Venugopal, Abhijith; Valero-Delgado, Fernando; Venkatesh, Janani; Wang, Feitang; Wang, Shimeng; Winski, Dominic A.; Winton, V. Holly L.; Whiteford, Arran; Xiao, Cunde; Yang, Jiao; Zhang, Xin
2018-02-01
High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE) ice core. Comparison of this record with climate reanalysis data for the 1979-2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons), with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.
8. The Ross Sea Dipole – temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years
Directory of Open Access Journals (Sweden)
N. A. N. Bertler
2018-02-01
Full Text Available High-resolution, well-dated climate archives provide an opportunity to investigate the dynamic interactions of climate patterns relevant for future projections. Here, we present data from a new, annually dated ice core record from the eastern Ross Sea, named the Roosevelt Island Climate Evolution (RICE ice core. Comparison of this record with climate reanalysis data for the 1979–2012 interval shows that RICE reliably captures temperature and snow precipitation variability in the region. Trends over the past 2700 years in RICE are shown to be distinct from those in West Antarctica and the western Ross Sea captured by other ice cores. For most of this interval, the eastern Ross Sea was warming (or showing isotopic enrichment for other reasons, with increased snow accumulation and perhaps decreased sea ice concentration. However, West Antarctica cooled and the western Ross Sea showed no significant isotope temperature trend. This pattern here is referred to as the Ross Sea Dipole. Notably, during the Little Ice Age, West Antarctica and the western Ross Sea experienced colder than average temperatures, while the eastern Ross Sea underwent a period of warming or increased isotopic enrichment. From the 17th century onwards, this dipole relationship changed. All three regions show current warming, with snow accumulation declining in West Antarctica and the eastern Ross Sea but increasing in the western Ross Sea. We interpret this pattern as reflecting an increase in sea ice in the eastern Ross Sea with perhaps the establishment of a modern Roosevelt Island polynya as a local moisture source for RICE.
9. Ross sea ice motion, area flux, and deformation
Science.gov (United States)
kwok, Ron
2005-01-01
The sea ice motion, area export, and deformation of the Ross Sea ice cover are examined with satellite passive microwave and RADARSAT observations. The record of high-resolution synthetic aperture radar (SAR) data, from 1998 and 2000, allows the estimation of the variability of ice deformation at the small scale (10 km) and to assess the quality of the longer record of passive microwave ice motion. Daily and subdaily deformation fields and RADARSAT imagery highlight the variability of motion and deformation in the Ross Sea. With the passive microwave ice motion, the area export at a flux gate positioned between Cape Adare and Land Bay is estimated. Between 1992 and 2003, a positive trend can be seen in the winter (March-November) ice area flux that has a mean of 990 x 103 km2 and ranges from a low of 600 x 103 km2 in 1992 to a peak of 1600 x 103 km2 in 2001. In the mean, the southern Ross Sea produces almost twice its own area of sea ice during the winter. Cross-gate sea level pressure (SLP) gradients explain 60% of the variance in the ice area flux. A positive trend in this gradient, from reanalysis products, suggests a 'spinup' of the Ross Sea Gyre over the past 12 yr. In both the NCEP-NCAR and ERA-40 surface pressure fields, longer-term trends in this gradient and mean SLP between 1979 and 2002 are explored along with positive anomalies in the monthly cross-gate SLP gradient associated with the positive phase of the Southern Hemisphere annular mode and the extrapolar Southern Oscillation.
10. Climatology and decadal variability of the Ross Sea shelf waters
Directory of Open Access Journals (Sweden)
A. Russo
2011-06-01
Full Text Available The World Ocean Database 2001 data located in the Ross Sea (named WOD01 and containing data in this region since 1928 are merged with recent data collected by the Italian expeditions (CLIMA dataset in the period November 1994-February 2004 in the same area. From this extended dataset, austral summer climatologies of the main Ross Sea subsurface, intermediate and bottom water masses: High Salinity Shelf Water (HSSW, Low Salinity Shelf Water (LSSW, Ice Shelf Water (ISW and Modified Circumpolar Deep Water (MCDW have been drawn. The comparison between the WOD01_1994 climatologies (a subset of the WOD01 dataset until April 1994 and the CLIMA ones for the period 1994/95-2003/04 showed significant changes occurred during the decade. The freshening of the Ross Sea shelf waters which occurred during the period 1960-2000, was confirmed by our analysis in all the main water masses, even though with a spatially varying intensity. Relevant variations were found for the MCDW masses, which appeared to reduce their presence and to deepen; this can be ascribed to the very limited freshening of the MCDW core, which allowed an increased density with respect to the surrounding waters. Variations in the MCDW properties and extension could have relevant consequences, e.g. a decreased Ross Ice Shelf basal melting or a reduced supply of nutrients, and may also be indicative of a reduced thermohaline circulation within the Ross Sea. Shelf Waters (SW having neutral density γn > 28.7 Kg m-3, which contribute to form the densest Antarctic Bottom Waters (AABW, showed a large volumetric decrease in the 1994/95-2003/04 decade, most likely as a consequence of the SW freshening.
11. Active and Passive Microwave Determination of the Circulation and Characteristics of Weddell and Ross Sea Ice
Science.gov (United States)
Drinkwater, Mark R.; Liu, Xiang
2000-01-01
A combination of satellite microwave data sets are used in conjunction with ECMWF (Medium Range Weather Forecasts) and NCEP (National Center for Environment Prediction) meteorological analysis fields to investigate seasonal variability in the circulation and sea-ice dynamics of the Weddell and Ross Seas. Results of sea-ice tracking using SSM/I (Special Sensor Microwave Imager), Scatterometer and SAR images are combined with in-situ data derived from Argos buoys and GPS drifters to validate observed drift patterns. Seasonal 3-month climatologies of ice motion and drift speed variance illustrate the response of the sea-ice system to seasonal forcing. A melt-detection algorithm is used to track the onset of seasonal melt, and to determine the extent and duration of atmospherically-led surface melting during austral summer. Results show that wind-driven drift regulates the seasonal distribution and characteristics of sea-ice and the intensity of the cyclonic Gyre circulation in these two regions.
12. Distribution of Ra-226 in the Ross Sea, Antarctica
International Nuclear Information System (INIS)
Bettoli, M.G.; Cantelli, L.; Queirazza, G.; Roveri, M.; Tositti, L.; Tubertini, O.; Valcher, S.
1996-01-01
An improved procedure for the determination of Rn-222 and Ra-226 in seawater developed for easier on-board operations is presented. Data on the radioactive disequilibrium between the mentioned radionuclides as directly determined in the field can be greatly helpful in the study of the gas-exchange processes at the air-sea interface, especially as far as the Antarctic Ocean is concerned. The method employed has been preliminary tested in laboratory on a set of seawater samples collected in the Ross Sea and Ra-226 data collected are discussed and compared to literature data. (UK)
13. Rossing
International Nuclear Information System (INIS)
Anon.
1979-01-01
Rossing is a uranium mine in the heart of the Namib desert in South West Africa (Namibia). Interms of the material recovered from the huge open pit, it is the largest uranium mine in the world. This article gives a short history of the development of this mine
14. Note On The Ross Sea Shelf Water Downflow Processes (antarctica)
Science.gov (United States)
Bergamasco, A.; Defendi, V.; Spezie, G.; Budillon, G.; Carniel, S.
In the framework of the CLIMA Project of the Italian National Program for Research in Antarctica, three different experimental data sets were acquired along the continental shelf break; two of them (in 1997 and 2001) close to Cape Adare, the 1998 one in the middle of the Ross Sea (i.e. 75 S, 177 W). The investigations were chosen in order to explore the downslope flow of the bottom waters produced in the Ross Sea, namely the High Salinity Shelf Water (HSSW, the densest water mass of the southern ocean coming from its formation site in the polynya region in Terra Nova bay), and the Ice Shelf Water (ISW, originated below the Ross Ice Shelf and outflowing northward). Both bottom waters spill over the shelf edge and mix with the Circumpolar Deep Water (CDW) contributing to the formation of the Antarctic Bottom Waters (AABW). Interpreting temperature, salinity and density maps in terms of cascading processes, both HSSW and ISW overflows are evidenced during, respectively, 1997 and 1998. During the 2001 acquisition there is no presence of HSSW along the shelf break, nevertheless distribution captures the evidence of a downslope flow process.
15. Late Quaternary climatic changes in the Ross Sea area, Antarctica
International Nuclear Information System (INIS)
Brambati, A.; Melis, R.; Quaia, T.; Salvi, G.
2002-01-01
Ten cores from the Ross Sea continental margin were investigated to detect Late Quaternary climatic changes. Two main climatic cycles over the last 300,000 yr (isotope stages 1-8) were recognised in cores from the continental slope, whereas minor fluctuations over the last 30,000 yr were found in cores from the continental shelf. The occurrence of calcareous taxa within the Last Glacial interval and their subsequent disappearance reveal a general raising of the CCD during the last climatic cycle. In addition, periodical trends of c. 400, c. 700, and c. 1400 yr determined on calcareous foraminifers from sediments of the Joides Basin, indicate fluctuations of the Ross Ice Shelf between 15 and 30 ka BP. (author). 24 refs., 5 figs
16. Downslope flow across the Ross Sea shelf break (Antarctica)
Science.gov (United States)
Bergamasco, A.; Budillon, G.; Carniel, S.; Defendi, V.; Meloni, R.; Paschini, E.; Sclavo, M.; Spezie, G.
2003-12-01
The analysis of some high-resolution hydrological data sets acquired during the 1997, 1998, 2001 and 2003 austral summers across the Ross Sea continental shelf break are here presented. The main focus of these cruises carried out in the framework of the Italian National Antarctic Program was the investigation of the downslope flow of the dense waters originated inside the Ross Sea. Such dense waters, flow near the bottom and, reaching the continental shelf break, ventilate the deep ocean. Two Antarctic continental shelf mechanisms can originate dense and deep waters. The former mechanism involves the formation, along the Victoria Land coasts, of a dense and saline water mass, the High Salinity Shelf Water (HSSW). The HSSW formation is linked to the rejection of salt into the water column as sea ice freezes, especially during winter, in the polynya areas, where the ice is continuously pushed offshore by the strong katabatic winds. The latter one is responsible of the formation of a supercold water mass, the Ice Shelf Water (ISW). The salt supplied by the HSSW recirculated below the Ross Ice Shelf, the latent heat of melting and the heat sink provided by the Ross Ice Shelf give rise to plumes of ISW, characterized by temperatures below the sea-surface freezing point. The dense shelf waters migrate to the continental shelf-break, spill over the shelf edge and descend the continental slope as a shelf-break gravity current, subject to friction and possibly enhanced by topographic channelling. Friction, in particular, breaks the constraint of potential vorticity conservation, counteracting the geostrophic tendency for along slope flow. The density-driven downslope motion or cascading entrains ambient water, namely the lower layer of the CDW, reaches a depth where density is the same and spreads off-slope. In fact, the cascading event is inhibited by friction without entrainment. The downslope processes are important for the ocean and climate system because they play a
17. Strontium isotopic study of sediment from the Ross Sea
International Nuclear Information System (INIS)
Kovach, J.; Faure, G.
1977-01-01
A preliminary report summarizing the results of a study of the strontium-87/strontium-86 ratios and of the rubidium and strontium concentrations of the fine-grained (less than 150 microns) noncarbonate fractions of sediment samples from core E32-25 raised from a depth of 327 fathoms in the Ross Sea at 78 0 31.0'S 164 0 24.7'W was presented. The strontium-87/strontium-86 ratios of the samples analyzed range from 0.7119 to 0.7220. Rubidium and strontium concentrations range, respectively, from 126 to 164 parts per million and from 113 to 174 parts per million. The observed strontium-87/strontium-86 ratios and strontium concentrations in sediment samples from core E32-25 fit a hyperbolic curve. These ratios can be used to estimate the concentrations of volcanogenic detritus in the sediment samples. The results of this study provide additional baseline data for anticipated future studies of sediment cores to be recovered from beneath the Ross Ice Shelf by the Ross Ice Shelf Project. 1 figure
18. The Satellite Passive-Microwave Record of Sea Ice in the Ross Sea Since Late 1978
Science.gov (United States)
Parkinson, Claire L.
2009-01-01
Satellites have provided us with a remarkable ability to monitor many aspects of the globe day-in and day-out and sea ice is one of numerous variables that by now have quite substantial satellite records. Passive-microwave data have been particularly valuable in sea ice monitoring, with a record that extends back to August 1987 on daily basis (for most of the period), to November 1970 on a less complete basis (again for most of the period), and to December 1972 on a less complete basis. For the period since November 1970, Ross Sea sea ice imagery is available at spatial resolution of approximately 25 km. This allows good depictions of the seasonal advance and retreat of the ice cover each year, along with its marked interannual variability. The Ross Sea ice extent typically reaches a minimum of approximately 0.7 x 10(exp 6) square kilometers in February, rising to a maximum of approximately 4.0 x 10(exp 6) square kilometers in September, with much variability among years for both those numbers. The Ross Sea images show clearly the day-by-day activity greatly from year to year. Animations of the data help to highlight the dynamic nature of the Ross Sea ice cover. The satellite data also allow calculation of trends in the ice cover over the period of the satellite record. Using linear least-squares fits, the Ross Sea ice extent increased at an average rate of 12,600 plus or minus 1,800 square kilometers per year between November 1978 and December 2007, with every month exhibiting increased ice extent and the rates of increase ranging from a low of 7,500 plus or minus 5,000 square kilometers per year for the February ice extents to a high of 20,300 plus or minus 6,100 kilometers per year for the October ice extents. On a yearly average basis, for 1979-2007 the Ross Sea ice extent increased at a rate of 4.8 plus or minus 1.6 % per decade. Placing the Ross Sea in the context of the Southern Ocean as a whole, over the November 1978-December 2007 period the Ross Sea had
19. Does temperature structure phytoplankton community composition in the Ross Sea, Antarctica?
Science.gov (United States)
The Ross Sea polynya experiences one of the largest phytoplankton blooms in the Southern Ocean. Energy flow potential within the Ross Sea food web is primarily set by diatoms and prymnesiophytes, the latter dominated by Phaeocystis antarctica. We investigated physical, chemical,...
20. Observing the seasonal cycle of the upper ocean in the Ross Sea, Antarctica, with autonomous profiling floats
Science.gov (United States)
Porter, D. F.; Springer, S. R.; Padman, L.; Fricker, H. A.; Bell, R. E.
2017-12-01
The upper layers of the Southern Ocean where it meets the Antarctic ice sheet undergoes a large seasonal cycle controlled by surface radiation and by freshwater fluxes, both of which are strongly influenced by sea ice. In regions where seasonal sea ice and icebergs limit use of ice-tethered profilers and conventional moorings, autonomous profiling floats can sample the upper ocean. The deployment of seven Apex floats (by sea) and six ALAMO floats (by air) provides unique upper ocean hydrographic data in the Ross Sea close to the Ross Ice Shelf front. A novel choice of mission parameters - setting parking depth deeper than the seabed - limits their drift, allowing us to deploy the floats close to the ice shelf front, while sea ice avoidance algorithms allow the floats to to sample through winter under sea ice. Hydrographic profiles show the detailed development of the seasonal mixed layer close to the Ross front, and interannual variability of the seasonal mixed layer and deeper water masses on the central Ross Sea continental shelf. After the sea ice breakup in spring, a warm and fresh surface mixed layer develops, further warming and deepening throughout the summer. The mixed layer deepens, with maximum temperatures exceeding 0ºC in mid-February. By March, the surface energy budget becomes negative and sea ice begins to form, creating a cold, saline and dense surface layer. Once these processes overcome the stable summer stratification, convection erodes the surface mixed layer, mixing some heat downwards to deeper layers. There is considerable interannual variability in the evolution and strength of the surface mixed layer: summers with shorter ice-free periods result in a cooler and shallower surface mixed layer, which accumulates less heat than the summers with longer ice-free periods. Early ice breakup occurred in all floats in 2016/17 summer, enhancing the absorbed solar flux leading to a warmer surface mixed layer. Together, these unique measurements from
1. High-Resolution Body Wave Tomography of the Ross Sea Embayment, Antarctica
Science.gov (United States)
White-Gaynor, A.; Nyblade, A.; Wiens, D. A.; Aster, R. C.; Gerstoft, P.; Bromirski, P. D.; Stephen, R. A.
2017-12-01
The West Antarctic Rift System (WARS) is one of the least understood continental rift system on the planet. The 1000 km wide WARS includes the Ross Sea Embayment between Marie Byrd Land and the Transantarctic Mountains (TAMS). Active volcanism on Ross Island continues to challenge our understanding of the generally quiescent rift system. Previous regional-scale body wave tomographic investigations have identified areas of low seismic wave speeds to 200 km depth beneath Ross Island. However, the spatial extent of the low velocity structure across the entirety of the WARS remains poorly constrained due to the insufficient resolution of upper mantle structure under the Ross Sea Embayment away from Ross Island. We utilize teleseismic P wave observations recorded on the RIS/DRIS network, which consists of 34 seismometers deployed across the Ross Ice Shelf, along with data from nearby POLENET and TAMSEIS stations to better resolve this region. Relative P wave travel time residuals from 1300 teleseismic events, obtained using a multichannel cross-correlation method, have been inverted for a seismic velocity model of the upper mantle throughout the Ross Sea Embayment. Our results suggest that the low wave speed structure under Ross Island extends roughly halfway across the Embayment and south along the Transantarctic Mountains. This observation is consistent with a two-phase rifting history for the WARS in which broad, late Cretaceous rifting between Marie Byrd Land and the TAMS transitioned to more focused rifting along the TAMS margin in the Cenozoic.
2. Multichannel Seismic Reflection Data - SCAR - Ross Sea - 1987, SDLS CD-ROM vol 13
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data recorded during the 1987 field season in the Ross Sea, Antarctica, by SEVMORGEOLOGIA, RUSSIA. The...
3. Multichannel Seismic Reflection Data - SCAR - Ross Sea - 1980, SDLS, CD-ROM vol 4
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data from seven lines recorded during 1980 in the Ross Sea, Antarctica, by the Bundesanstalt fur...
4. Multichannel Seismic Reflection Data - SCAR - Ross Sea - 1980, SDLS CD-ROM vol 3
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data from four lines recorded during 1980 in the Ross Sea, Antarctica, by the Bundesanstalt fur...
5. Multichannel Seismic Reflection Data - SCAR, Ross Sea - 1982-1983, CD-ROM vol 9
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data from fourteen lines recorded during 1982 in the Ross Sea and Wilkes Island, Antarctica, by the...
6. Multichannel Seismic Reflection Data - SCAR - Ross Sea - 1989, SDLS CD-ROM vol 14
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data recorded during 1989 field season in the Ross Sea, Antarctica, by the SEVMORGEOLOGIA, RUSSIS. The...
7. Multichannel Seismic Reflection Data - SCAR - Ross Sea 1980, SDLS, CD-ROM vol 5
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data from eleven lines recorded during 1980 in the Ross Sea, Antarctica, by the Bundesanstalt fur...
8. Multichannel Seismic Reflection Data - SCAR - Ross Sea 1982, SDLS CD-ROM vol 12
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data from seven lines recorded during 1982 in the Ross Sea, Antarctica, by the Institut Francais du...
9. Multichannel Seismic Reflection Data - SCAR - Ross Sea 1987-1988, SDLS CD-ROM vol 2
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — These data are stacked multichannel marine seismic reflection data from six lines recorded during 1988 in the Ross Sea, Antarctica, by the Bundesanstalt fur...
10. Polynyas and Ice Production Evolution in the Ross Sea (PIPERS)
Science.gov (United States)
Ackley, S. F.
2017-12-01
One focus of the PIPERS cruise into the Ross Sea ice cover during April-June 2017 was the Terra Nova Bay (TNB) polynya where joint measurements of air-ice-ocean wave interaction were conducted over twelve days. In Terra Nova Bay, measurements were made in three katabatic wind events each with sustained winds over 35 ms-1 and air temperatures below -15C. Near shore, intense wave fields with wave amplitudes of over 2m and 7-9 sec periods built and large amounts of frazil ice crystals grew. The frazil ice gathered initially into short and narrow plumes that eventually were added laterally to create longer and wider streaks or bands. Breaking waves within these wider streaks were dampened which appeared to enhance the development of pancake ice. Eventually, the open water areas between the streaks sealed off, developing a complete ice cover of 100 percent concentration (80-90 percent pancakes, 20-10 percent frazil) over a wide front (30km). The pancakes continued to grow in diameter and thickness as waves alternately contracted and expanded the ice cover, with the thicker larger floes further diminishing the wave field and lateral motion between pancakes until the initial pancake ice growth ceased. The equilibrium thickness of the ice was 20-30cm in the pancake ice. While the waves had died off however, katabatic wind velocities were sustained and resulted in a wide area of concentrated, rafted, pancake ice that was rapidly advected downstream until the end of the katabatic event. High resolution TerraSar-X radar satellite imagery showed the length of the ice area produced in one single event extended over 300km or ten times the length of the open water area during one polynya event. The TNB polynya is therefore an "ice factory" where frazil ice is manufactured into pancake ice floes that are then pushed out of the assembly area and advected, rafted (and occasionally piled up into "dragon skin" ice), until the katabatic wind dies off at the coastal source.
11. First stage of INTRAMAP: INtegrated Transantarctic Mountains and Ross Sea Area Magnetic Anomaly Project
Directory of Open Access Journals (Sweden)
1999-06-01
Full Text Available INTRAMAP (INtegrated Transantarctic Mountains and Ross Sea Area Magnetic Anomaly Project is an international effort to merge the magnetic data acquired throughout the "Ross Sea Antarctic Sector" (south of 60°S between 135°-255°E including the Transantarctic Mountains (TAM, the Ross Sea, Marie Byrd Land, and the Pacific coast, and also to begin the compilation efforts for new data over the Wilkes Basin. This project is a component of the continental scale Antarctic Digital Magnetic Anomaly Project (ADMAP. The first stage of INTRAMAP addresses the analysis and merging of GITARA (1991-1994 and GANOVEX (1984 aeromagnetic surveys together with ground magnetic data (1984-1989. The combined data sets cover an area of approximately 30 km2 over Victoria Land and adjacent Ross Sea. Map and profile gridding were implemented to integrate the data sets. These approaches are studied for improving existing strategies to adopt for the whole magnetic compilation effort. The final microlevelled grid that we produce is a new tool for regional interpretation of the main tectonic and geologic features of this sector of Antarctica.
12. Sources of iron in the Ross Sea Polynya in early summer
NARCIS (Netherlands)
Gerringa, L. J. A.; Laan, P.; van Dijken, G. L.; van Haren, H.; De Baar, H. J. W.; Arrigo, K. R.; Alderkamp, A. -C.
2015-01-01
Dissolved Fe (DFe) was measured in the Ross Sea Polynya (RSP), Antarctica, during a GEOTRACES cruise between 20 December 2013 and 5 January 2014. DFe was measured over the full water column with special emphasis on samples near the seafloor. In the upper mixed layer, DFe was very low everywhere (
13. Distribution and ventilation of water masses in the western Ross Sea inferred from CFC measurements
Science.gov (United States)
Rivaro, Paola; Ianni, Carmela; Magi, Emanuele; Massolo, Serena; Budillon, Giorgio; Smethie, William M.
2015-03-01
During the CLIMA Project (R.V. Italica cruise PNRA XVI, January-February 2001), hydrographic and chlorofluorocarbons (CFCs) observations were obtained, particularly in the western Ross Sea. Their distribution demonstrated water mass structure and ventilation processes in the investigated areas. In the surface waters (AASW) the CFC saturation levels varied spatially: CFCs were undersaturated in all the areas (range from 80 to 90%), with the exception of few stations sampled near Ross Island. In particular, the Terra Nova Bay polynya, where high salinity shelf water (HSSW) is produced, was a low-saturated surface area (74%) with respect to CFCs. Throughout most of the shelf area, the presence of modified circumpolar deep water (MCDW) was reflected in a mid-depth CFC concentration minima. Beneath the MCDW, CFC concentrations generally increased in the shelf waters towards the seafloor. We estimated that the corresponding CFCs saturation level in the source water region for HSSW was about 68-70%. Waters with high CFC concentrations were detected in the western Ross Sea on the down slope side of the Drygalski Trough, indicating that AABW was being supplied to the deep Antarctic Basin. Estimates of ventilation ages depend strongly on the saturation levels. We calculated ventilation ages using the saturation level calibrated tracer ratio, CFC11/CFC12. We deduced a mean residence time of the shelf waters of about 6-7 years between the western Ross Sea source and the shelf break.
14. Physical, chemical, and biological data collected during two research cruises in the Ross Sea, Antarctica from December 2004 to January 2005 and October to November 2005 for Ross Sea Sulfur Dynamics study (NODC Accession 0117322)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — This dataset contains transect data from two research cruises to the Ross Sea, Antarctica, aboard the RV Nathaniel B. Palmer (NBP) in December 2004 to January 2005...
15. On the outflow of dense water from the Weddell and Ross Seas in OCCAM model
Directory of Open Access Journals (Sweden)
R. Kerr
2012-06-01
Full Text Available We describe the seasonal and interannual variability of volume transports in the Weddell and Ross Seas using the 1/12° 20-yr simulation of the OCCAM global ocean general circulation model. The average simulated full-depth cumulative volume transports were 28.5 ± 2.9 Sv (1 Sv ≡ 106 m3 s−1 and 13.4 ± 5.2 Sv, across the main export regions of the Weddell and Ross Seas, respectively. The values of mean outflow of Antarctic Bottom Water (AABW (defined by neutral density γn ≥ 28.27 kg m−3 from the Weddell and Ross Seas of 10.6 ± 3.1 Sv and 0.5 ± 0.7 Sv, respectively, agree with the range reported in historical observational studies. The export of Weddell Sea dense water in OCCAM is primarily determined by the strength of the Weddell Gyre. Variability in AABW export is predominantly at periods of ~1 yr and 2–4 yr.
16. Temperature, salinity and oxygen data collected from the Oden in the Amundsen and Ross Seas, 2010 - 2011 (NCEI Accession 0104260)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Data were collected to investigate the physical oceanography of the Amundsen and Ross Seas. Funded under the following projects: Physical Oceanography of the...
17. Neoglacial Antarctic sea-ice expansion driven by mid-Holocene retreat of the Ross Ice Shelf.
Science.gov (United States)
Bendle, J. A.; Newton, K.; Mckay, R. M.; Crosta, X.; Etourneau, J.; Anya, A. B.; Seki, O.; Golledge, N. R.; Bertler, N. A. N.; Willmott, V.; Schouten, S.; Riesselman, C. R.; Masse, G.; Dunbar, R. B.
2017-12-01
Recent decades have seen expanding Antarctic sea-ice coverage, coeval with thinning West Antarctic Ice Sheet (WAIS) ice shelves and the rapid freshening of surface and bottom waters along the Antarctic margin. The mid-Holocene Neoglacial transition represents the last comparable baseline shift in sea-ice behaviour. The drivers and feedbacks involved in both the recent and Holocene events are poorly understood and characterised by large proxy-model mismatches. We present new records of compound specific fatty acid isotope analyses (δ2H-FA), highly-branched isoprenoid alkenes (HBIs) TEX86L temperatures, grain-size, mass accumulations rates (MARs) and image analyses from a 171m Holocene sediment sequence from Site U1357 (IODP leg 318). In combination with published records we reconstruct Holocene changes in glacial meltwater, sedimentary inputs and sea-ice. The early Holocene (11 to 10 ka) is characterised by large fluctuations in inputs of deglacial meltwater and sediments and seismic evidence of downlapping material from the south, suggesting a dominating influence from glacial retreat of the local outlet glaciers. From 10 to 8 ka there is decreasing meltwater inputs, an onlapping drift and advection of material from the east. After ca. 8 ka positively correlated δ2H-FA and MARs infer that pulses of glacial melt correlate to stronger easterly currents, driving erosion of material from upstream banks and that the Ross Ice Shelf (RIS) becomes a major influence. A large mid-Holocene meltwater pulse (preceded by warming TEX86L temperatures) is evident between ca. 6 to 4.5 ka, culminating in a rapid and permanent increase in sea-ice from 4.5 ka. This is coeval with cosmogenic nuclide evidence for a rapid thinning of the Antarctic ice sheet during the mid-Holocene (Hein et al., 2016). We suggest this represents a final major pulse of deglaciation from the Ross Ice Shelf, which initiates the Neoglacial, driving cool surface waters along the coast and greater sea
18. Sea Ice Drift Monitoring in the Bohai Sea Based on GF4 Satellite
Science.gov (United States)
Zhao, Y.; Wei, P.; Zhu, H.; Xing, B.
2018-04-01
The Bohai Sea is the inland sea with the highest latitude in China. In winter, the phenomenon of freezing occurs in the Bohai Sea due to frequent cold wave influx. According to historical records, there have been three serious ice packs in the Bohai Sea in the past 50 years which caused heavy losses to our economy. Therefore, it is of great significance to monitor the drift of sea ice and sea ice in the Bohai Sea. The GF4 image has the advantages of short imaging time and high spatial resolution. Based on the GF4 satellite images, the three methods of SIFT (Scale invariant feature - the transform and Scale invariant feature transform), MCC (maximum cross-correlation method) and sift combined with MCC are used to monitor sea ice drift and calculate the speed and direction of sea ice drift, the three calculation results are compared and analyzed by using expert interpretation and historical statistical data to carry out remote sensing monitoring of sea ice drift results. The experimental results show that the experimental results of the three methods are in accordance with expert interpretation and historical statistics. Therefore, the GF4 remote sensing satellite images have the ability to monitor sea ice drift and can be used for drift monitoring of sea ice in the Bohai Sea.
19. On the dense water spreading off the Ross Sea shelf (Southern Ocean)
Science.gov (United States)
Budillon, G.; Gremes Cordero, S.; Salusti, E.
2002-07-01
In this study, current meter and hydrological data obtained during the X Italian Expedition in the Ross Sea (CLIMA Project) are analyzed. Our data show a nice agreement with previous data referring to the water masses present in this area and their dynamics. Here, they are used to further analyze the mixing and deepening processes of Deep Ice Shelf Water (DISW) over the northern shelf break of the Ross Sea. In more detail, our work is focused on the elementary mechanisms that are the most efficient in removing dense water from the shelf: either classical mixing effects or density currents that interact with some topographic irregularity in order to drop to deeper levels, or also the variability of the Antarctic Circumpolar Current (ACC) which, in its meandering, can push the dense water off the shelf, thus interrupting its geostrophic flow. We also discuss in detail the (partial) evidence of dramatic interactions of the dense water with bottom particulate, of geological or biological origin, thus generating impulsive or quasi-steady density-turbidity currents. This complex interaction allows one to consider bottom particular and dense water as a unique self-interacting system. In synthesis, this is a first tentative analysis of the effect of bottom particulate on the dense water dynamics in the Ross Sea.
20. Problems and Possible Solutions Concerning Radiocarbon Dating of Surface Marine Sediments, Ross Sea, Antarctica
Science.gov (United States)
Andrews, John T.; Domack, Eugene W.; Cunningham, Wendy L.; Leventer, Amy; Licht, Kathy J.; Jull, A. J. Timothy; DeMaster, David J.; Jennings, Anne E.
1999-09-01
Radiocarbon accelerator mass spectrometric (AMS) dates on the acid-insoluble fraction from 38 core tops from the western Ross Sea, Antarctica, are used to address these questions: (1) What are the apparent ages of sediments at or close to the present sediment/water interface? (2) Is there a statistically significant pattern to the spatial distribution of core top ages? and (3) Is there a "correction factor" that can be applied to these age determinations to obtain the best possible Holocene (downcore) chronologies? Ages of core top sediments range from 2000 to 21,000 14C yr B.P. Some "old" core top dates are from piston cores and probably represent the loss of sediment during the coring process, but some core top samples >6000 14C yr B.P. may represent little or no Holocene deposition. Four possible sources of variability in dates ≤6000 14C yr B.P. (n = 28) are associated with (1) different sample preparation methods, (2) different sediment recovery systems, (3) different geographic regions, and (4) within-sample lateral age variability. Statistical analysis on an a posteriori design indicates that geographic area is the major cause of variability; there is a difference in mean surface sediment age of nearly 2000 yr between sites in the western Ross Sea and sites east of Ross Bank in south-central Ross Sea. The systematic variability in surface age between areas may be attributed to: (a) variable sediment accumulation rates (SAR) (surface age is inversely related to SAR), (b) differences in the percentage of reworked (dead) carbon between each area, and/or (c) differences in the CO2 exchange between the ocean and the atmosphere.
1. Operational SAR-based sea ice drift monitoring over the Baltic Sea
Directory of Open Access Journals (Sweden)
J. Karvonen
2012-07-01
Full Text Available An algorithm for computing ice drift from pairs of synthetic aperture radar (SAR images covering a common area has been developed at FMI. The algorithm has been developed based on the C-band SAR data over the Baltic Sea. It is based on phase correlation in two scales (coarse and fine with some additional constraints. The algorithm has been running operationally in the Baltic Sea from the beginning of 2011, using Radarsat-1 ScanSAR wide mode and Envisat ASAR wide swath mode data. The resulting ice drift fields are publicly available as part of the MyOcean EC project. The SAR-based ice drift vectors have been compared to the drift vectors from drifter buoys in the Baltic Sea during the first operational season, and also these validation results are shown in this paper. Also some navigationally useful sea ice quantities, which can be derived from ice drift vector fields, are presented.
2. Distribution of total alkalinity and pH in the Ross Sea (Antarctica waters during austral summer 2008
Directory of Open Access Journals (Sweden)
Paola Rivaro
2014-10-01
Full Text Available Measurements of total alkalinity (AT and pH were made in the Ross Sea in January–February 2008 in order to characterize the carbonate system in the Ross Sea and to evaluate the variability associated with different water masses. The main water masses of the Ross Sea, Antarctic Surface Water, High Salinity Shelf Water (HSSW, Deep Ice Shelf Water, Circumpolar Deep Water (CDW and Antarctic Bottom Water, were identified on the basis of the physical and chemical data. In particular, the AT ranged between 2275 and 2374 µmol kg−1 with the lowest values in the surface waters (2275–2346 µmol kg−1, where the influence of the sea-ice melting and of the variability of the physical properties was significant. In the deep layers of the water column, the AT maxima were measured in correspondence to the preferential pathways of the spreading HSSW. The pH had variable values in the surface layer (7.890–8.033 with the highest values in Terra Nova Bay and Ross Sea polynyas. A low pH (7.969±0.025 traced the intrusion of the CDW in the Ross Sea shelf area. All samples revealed waters that were oversaturated with respect to both calcite and aragonite, but near corrosive levels of aragonite saturation state (Ω ca. 1.1–1.2 were associated with the entrainment of CDW over the slope. Aragonite undersaturation is of particular concern for the zooplankton species comprising to calcifying organisms such as pteropods. The partial pressure of CO2 at the sea surface was undersaturated with respect to the atmospheric value, particularly in Terra Nova Bay and the Ross Sea polynyas, but a large variability in the sea–air CO2 fluxes was observed associated with different responses in the strength of the biological and physical processes.
3. Climate change impacts on southern Ross Sea phytoplankton composition, productivity, and export
Science.gov (United States)
Kaufman, Daniel E.; Friedrichs, Marjorie A. M.; Smith, Walker O.; Hofmann, Eileen E.; Dinniman, Michael S.; Hemmings, John C. P.
2017-03-01
The Ross Sea, a highly productive region of the Southern Ocean, is expected to experience warming during the next century along with reduced summer sea ice concentrations and shallower mixed layers. This study investigates how these climatic changes may alter phytoplankton assemblage composition, primary productivity, and export. Glider measurements are used to force a one-dimensional biogeochemical model, which includes diatoms and both solitary and colonial forms of Phaeocystis antarctica. Model performance is evaluated with glider observations, and experiments are conducted using projections of physical drivers for mid-21st and late-21st century. These scenarios reveal a 5% increase in primary productivity by midcentury and 14% by late-century and a proportional increase in carbon export, which remains approximately 18% of primary production. In addition, scenario results indicate diatom biomass increases while P. antarctica biomass decreases in the first half of the 21st century. In the second half of the century, diatom biomass remains relatively constant and P. antarctica biomass increases. Additional scenarios examining the independent contributions of expected future changes (temperature, mixed layer depth, irradiance, and surface iron inputs from melting ice) demonstrate that earlier availability of low light due to reduction of sea ice early in the growing season is the primary driver of productivity increases over the next century; shallower mixed layer depths additionally contribute to changes of assemblage composition and export. This study further demonstrates how glider data can be effectively used to facilitate model development and simulation, and inform interpretation of biogeochemical observations in the context of climate change.Plain Language SummaryUnderstanding how the global ocean responds to climate change requires knowing the natural behavior of individual regions and anticipating how future changes will affect each region differently. It
4. The influence of the Amundsen Sea Low on the winds in the Ross Sea and surroundings: Insights from a synoptic climatology
Science.gov (United States)
Coggins, Jack H. J.; McDonald, Adrian J.
2015-03-01
The Amundsen Sea Low (ASL) is an area of climatologically low atmospheric pressure situated over the Southern Ocean. The depth and location of this feature have significant effects on winds, temperature, moisture transport, and sea ice in its vicinity. In this article, we quantify the modulating effect of this feature on winds over the Ross Sea and Ross Ice Shelf. We examine composites of surface winds sampled according to extrema in ASL depth, longitude, and latitude. We employ the output of a previously developed synoptic climatology to identify the explanatory synoptic-scale forcings. In autumn, winter, and spring (AWS) we find that the impact of the depth of the ASL is smaller than that of its location. The ASL moves eastward when it is deep, thereby reducing its influence on Ross Sea winds. When the ASL is northward, we find strongly enhanced southerly flows over the Ross Sea and Ice Shelf, forced by greater cyclonic activity in the north of the Ross Sea. In summer, we find increased cyclonic flow coinciding with a deeper ASL, despite the ASL being located in the Bellingshausen Sea at this time. The responses to the ASL longitude and latitude are profoundly different to those in AWS, suggesting that relationships are strongly dependent on the varying seasonal location of the low. We examine two metrics of the ASL depth and identify that the absolute mean sea level pressure (MSLP) has a more widespread response than that of the relative MSLP.
5. Diet and trophic niche of Antarctic silverfish Pleuragramma antarcticum in the Ross Sea, Antarctica.
Science.gov (United States)
Pinkerton, M H; Forman, J; Bury, S J; Brown, J; Horn, P; O'Driscoll, R L
2013-01-01
The diet of Antarctic silverfish Pleuragramma antarcticum was evaluated by examining stomach contents of specimens collected in the Ross Sea (71°-77° S; 165°-180° E) in January to March 2008. Pleuragramma antarcticum (50-236 mm standard length, L(S)) and prey items were analysed for stable-isotopic composition of carbon and nitrogen. According to index of relative importance (I(RI) ), which incorporates frequency of occurrence, mass and number of prey items, the most important prey items were copepods (81%I(RI) over all specimens), predominantly Metridia gerlachei and Paraeuchaeta sp., with krill and fishes having low I(RI) (2·2 and 5·6%I(RI) overall). According to mass of prey (M) in stomachs, however, fishes (P. antarcticum and myctophids) and krill dominated overall diet (48 and 22%M, respectively), with copepods being a relatively minor constituent of overall diet by mass (9·9%M). Piscivory by P. antarcticum occurred mainly in the extreme south-west of the region and near the continental slope. Krill identified to species level in P. antarcticum stomachs were predominantly Euphausia superba (14·1%M) with some Euphausia crystallophorias (4·8%M). Both DistLM modelling (PRIMER-permanova+) on stomach contents (by I(RI)) and stepwise generalized linear modelling on stable isotopes showed that L(S) and location were significant predictors of P. antarcticum diet. Postlarval P. antarcticum (50-89 mm L(S)) consumed exclusively copepods. Juvenile P. antarcticum (90-151 mm L(S)) consumed predominantly krill and copepods by mass (46 and 30%M, respectively). Small adult P. antarcticum (152-178 mm L(S)) consumed krill, fishes and copepods (37, 36 and 15%M, respectively). Large adult P. antarcticum (179-236 mm L(S)) consumed predominantly fishes and krill (55 and 17%M, respectively), especially in the north (near the Ross Sea slope) and in the SW Ross Sea. Amphipods were occasionally important prey items for P. antarcticum (western Ross Sea, 39%M). General
6. WHISPERS Project on the easternmost slope of the Ross Sea (Antarctica): preliminary results.
Science.gov (United States)
Olivo, E.; De Santis, L.; Bergamasco, A.; Colleoni, F.; Gales, J. A.; Florindo-Lopez, C.; Kim, S.; Kovacevic, V.; Rebesco, M.
2017-12-01
The advance and retreat of the West Antarctic Ice Sheet from the outer continental shelf and the oceanic circulation are the main causes of the depositional processes on the Ross Sea continental slope, at present time and during the most of the Cenozoic. Currently the Antarctic Bottom Water formation is directly linked to the relatively warm Circumpolar Deep Water that, encroaching the continental shelf, mixes with the colder Ross Sea Bottom Water. Detailed multibeam and geological surveys useful to locate and characterize peculiar morphological structures on the bottom are essential to study how the glacial and oceanographic processes interact with the seabed sediments. In the framework of the PNRA-WHISPERS project (XXXIIth Italian Antarctic expedition - January/March 2017), new multibeam bathymetric, sub-bottom chirp, were acquired from the easternmost margin of the Ross Sea, on the southeastern side of the Hayes Bank, usually covered by sea ice. We observed on the upper slope erosional features (incised gullies of likely glacial meltwater origin). A broad scar in the upper slope is characterized by an elongated SSW-NNE ridge (10 km long, 850-1200 m water depth, 2 km wide), that may be a remnants of previous glacial or debris flow deposits, eroded by meltwater outwash discharge at the beginning of grounding ice retreat and by RSBW cascading along the slope, as documented by Expandable Bathy-Thermograph and Acoustic Depth Current Profile data. Sub-bottom chirp profiles crossing this ridge show a very low amplitude reflective sea bed, supporting the hypothesis of its soft sediment nature, in good agreement with a very low acoustic velocity obtained by multichannel seismic data reprocessing. The occurrence of internal stratification on 2D multichannel seismic profiles would discount a gas-fluids related mud volcano origin. No sediment cores were collected, due to bad sea conditions and limited ship time, further data collection would be needed to fully understand
7. Ross Sea oceanographic data, 1983-1987 : USCGC Glacier, January-February 1983; USCGC Polar Sea, January-February 1984; USCGC Polar Star, February 1985; USCGC Polar Sea, February 1987 (NODC Accession 8900108)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and chemical data were collected using CTD casts from USCGC POLAR SEA and other platforms in the Ross Sea from 19 December 1976 to 06 February...
8. The Xanthophyceae and Chlorophyceae of the Western Ross Sea, Victoria Land, Antarctica and Macquarie Island collected under the direction of Prof. Dr. J. S. Zaneveld (1963—1967)
NARCIS (Netherlands)
Wagner, H.P.; Zaneveld, J.S.
1988-01-01
During the austral summer seasons of 1963-1964 and 1964-1965, and during the austral winter season of 1967 Prof. Dr. J.S. Zaneveld made collection expeditions to the western Ross Sea. In 1965 collections were also made from the U.S.C.G. icebreaker ‘Glacier’, around the western Ross Sea and around
9. Ross Sea Mollusca from the Latitudinal Gradient Program: R/V Italica 2004 Rauschert dredge samples
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Claudio Ghiglione
2013-10-01
Full Text Available Information regarding the molluscs in this dataset is based on the Rauschert dredge samples collected during the Latitudinal Gradient Program (LGP on board the R/V “Italica” in the Ross Sea (Antarctica in the austral summer 2004. A total of 18 epibenthic dredge deployments/samplings have been performed at four different locations at depths ranging from 84 to 515m by using a Rauschert dredge with a mesh size of 500µm. In total 8,359 specimens have been collected belonging to a total of 161 species. Considering this dataset in terms of occurrences, it corresponds to 505 discrete distributional records (incidence data. Of these, in order of abundance, 5,965 specimens were Gastropoda (accounting for 113 species, 1,323 were Bivalvia (accounting for 36 species, 949 were Aplacophora (accounting for 7 species, 74 specimens were Scaphopoda (3 species, 38 were Monoplacophora (1 species and, finally, 10 specimens were Polyplacophora (1 species. This data set represents the first large-scale survey of benthic micro-molluscs for the area and provides important information about the distribution of several species, which have been seldom or never recorded before in the Ross Sea. All vouchers are permanently stored at the Italian National Antarctic Museum (MNA, Section of Genoa, enabling future comparison and crosschecking. This material is also currently under study, from a molecular point of view, by the barcoding project “BAMBi” (PNRA 2010/A1.10.
10. Bacterivory by a Summer Assemblage of Nanoplankton in the Ross Sea, Antarctica: Mixotrophic Versus Heterotrophic Protists
Science.gov (United States)
Sanders, R. W.; Gast, R. J.
2016-02-01
Many protists traditionally described as phototrophic have recently been shown to have retained the primitive trait of phagotrophy, and thus function as mixotrophs. Mixotrophic nanoflagellates were identified in every sample examined from a summer cruise in the Ross Sea, Antarctica, where they often were more abundant than heterotrophic nanoflagellates that have previously been considered the major bacterivores in marine waters. Mixotrophs, identified by uptake of fluorescent tracers, comprised similar proportions (9-75%) of the total bacterivorous flagellates in summer as were previously determined for an earlier spring cruise in the Ross Sea. Protist diversity also was linked to functional bacterivores using a culture-independent method in which BrdU-labeled DNA of bacterial prey was incorporated into the DNA of eukaryotic grazers. Immunoprecipitation of the BrdU-labeld DNA was followed by high-throughput sequencing to identify a diverse group of bacterivores, including numerous uncultured eukaryotes. However, its utility for identification of mixotrophs was limited by the availability of sequences from known mixotrophs.
11. Trends in the breeding population and driving factors of Adélie penguin in the Ross Sea
Science.gov (United States)
He, H.; Li, X.; Cheng, X.
2017-12-01
12. Integrating terrestrial and marine records of the LGM in McMurdo Sound, Antarctica: implications for grounded ice expansion, ice flow, and deglaciation of the Ross Sea Embayment
Science.gov (United States)
Christ, A. J.; Marchant, D. R.
2017-12-01
During the LGM, grounded glacier ice filled the Ross Embayment and deposited glacial drift on volcanic islands and peninsulas in McMurdo Sound, as well as along coastal regions of the Transantarctic Mountains (TAM), including the McMurdo Dry Valleys and Royal Society Range. The flow geometry and retreat history of this ice remains debated, with contrasting views yielding divergent implications for both the fundamental cause of Antarctic ice expansion as well as the interaction and behavior of ice derived from East and West Antarctica during late Quaternary time. We present terrestrial geomorphologic evidence that enables the reconstruction of former ice elevations, ice-flow paths, and ice-marginal environments in McMurdo Sound. Radiocarbon dates of fossil algae interbedded with ice-marginal sediments provide a coherent timeline for local ice retreat. These data are integrated with marine-sediment records and multi-beam data to reconstruct late glacial dynamics of grounded ice in McMurdo Sound and the western Ross Sea. The combined dataset suggest a dominance of ice flow toward the TAM in McMurdo Sound during all phases of glaciation, with thick, grounded ice at or near its maximum extent between 19.6 and 12.3 calibrated thousands of years before present (cal. ka). Our data show no significant advance of locally derived ice from the TAM into McMurdo Sound, consistent with the assertion that Late Pleistocene expansion of grounded ice in McMurdo Sound, and throughout the wider Ross Embayment, occurs in response to lower eustatic sea level and the resulting advance of marine-based outlet glaciers and ice streams (and perhaps also reduced oceanic heat flux), rather than local increases in precipitation and ice accumulation. Finally, when combined with allied data across the wider Ross Embayment, which show that widespread deglaciation outside McMurdo Sound did not commence until 13.1 ka, the implication is that retreat of grounded glacier ice in the Ross Embayment did
13. South Polar Skua breeding populations in the Ross Sea assessed from demonstrated relationship with Adélie Penguin numbers
Science.gov (United States)
Wilson, Deborah J.; Lyver, Phil O'B.; Greene, Terry C.; Whitehead, Amy L.; Dugger, Catherine; Karl, Brian J.; Barringer, James R. F.; McGarry, Roger; Pollard, Annie M.; Ainley, David G.
2017-01-01
In the Ross Sea region, most South Polar Skuas (Stercorarius maccormicki) nest near Adélie Penguin (Pygoscelis adeliae) colonies, preying and scavenging on fish, penguins, and other carrion. To derive a relationship to predict skua numbers from better-quantified penguin numbers, we used distance sampling to estimate breeding skua numbers within 1000 m of 5 penguin nesting locations (Cape Crozier, Cape Royds, and 3 Cape Bird locations) on Ross Island in 3 consecutive years. Estimated numbers of skua breeding pairs were highest at Cape Crozier (270,000 penguin pairs; 1099 and 1347 skua pairs in 2 respective years) and lowest at Cape Royds (3000 penguin pairs; 45 skua pairs). The log–log linear relationship (R2 = 0.98) between pairs of skuas and penguins was highly significant, and most historical estimates of skua and penguin numbers in the Ross Sea were within 95 % prediction intervals of the regression. Applying our regression model to current Adélie Penguin colony sizes at 23 western Ross Sea locations predicted that 4635 pairs of skuas now breed within 1000 m of penguin colonies in the Ross Island metapopulation (including Beaufort Island) and northern Victoria Land. We estimate, using published skua estimates for elsewhere in Antarctica, that the Ross Sea South Polar Skua population comprises ~50 % of the world total, although this may be an overestimate because of incomplete data elsewhere. To improve predictions and enable measurement of future skua population change, we recommend additional South Polar Skua surveys using consistent distance-sampling methods at penguin colonies of a range of sizes.
14. Ross Sea Polynyas: Response of Ice Concentration Retrievals to Large Areas of Thin Ice
Science.gov (United States)
Kwok, R.; Comiso, J. C.; Martin, S.; Drucker, R.
2007-01-01
For a 3-month period between May and July of 2005, we examine the response of the Advanced Microwave Scanning Radiometer (AMSR-E) Enhanced NASA Team 2 (NT2) and AMSR-E Bootstrap (ABA) ice concentration algorithms to large areas of thin ice of the Ross Sea polynyas. Coincident Envisat Synthetic Aperture Radar (SAR) coverage of the region during this period offers a detailed look at the development of the polynyas within several hundred kilometers of the ice front. The high-resolution imagery and derived ice motion fields show bands of polynya ice, covering up to approximately 105 km(sup 2) of the Ross Sea, that are associated with wind-forced advection. In this study, ice thickness from AMSR-E 36 GHz polarization information serves as the basis for examination of the response. The quality of the thickness of newly formed sea ice (<10 cm) from AMSR-E is first assessed with thickness estimates derived from ice surface temperatures from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. The effect of large areas of thin ice in lowering the ice concentration estimates from both NT2/ABA approaches is clearly demonstrated. Results show relatively robust relationships between retrieved ice concentrations and thin ice thickness estimates that differ between the two algorithms. These relationships define the approximate spatial coincidence of ice concentration and thickness isopleths. Using the 83% (ABA) and 91% (NT2) isopleths as polynya boundaries, we show that the computed coverage compares well with that using the estimated 10-cm thickness contour. The thin ice response characterized here suggests that in regions with polynyas, the retrieval results could be used to provide useful geophysical information, namely thickness and coverage.
15. Assimilating bio-optical glider data during a phytoplankton bloom in the southern Ross Sea
Science.gov (United States)
Kaufman, Daniel E.; Friedrichs, Marjorie A. M.; Hemmings, John C. P.; Smith, Walker O., Jr.
2018-01-01
The Ross Sea is a region characterized by high primary productivity in comparison to other Antarctic coastal regions, and its productivity is marked by considerable variability both spatially (1-50 km) and temporally (days to weeks). This variability presents a challenge for inferring phytoplankton dynamics from observations that are limited in time or space, which is often the case due to logistical limitations of sampling. To better understand the spatiotemporal variability in Ross Sea phytoplankton dynamics and to determine how restricted sampling may skew dynamical interpretations, high-resolution bio-optical glider measurements were assimilated into a one-dimensional biogeochemical model adapted for the Ross Sea. The assimilation of data from the entire glider track using the micro-genetic and local search algorithms in the Marine Model Optimization Testbed improves the model-data fit by ˜ 50 %, generating rates of integrated primary production of 104 g C m-2 yr-1 and export at 200 m of 27 g C m-2 yr-1. Assimilating glider data from three different latitudinal bands and three different longitudinal bands results in minimal changes to the simulations, improves the model-data fit with respect to unassimilated data by ˜ 35 %, and confirms that analyzing these glider observations as a time series via a one-dimensional model is reasonable on these scales. Whereas assimilating the full glider data set produces well-constrained simulations, assimilating subsampled glider data at a frequency consistent with cruise-based sampling results in a wide range of primary production and export estimates. These estimates depend strongly on the timing of the assimilated observations, due to the presence of high mesoscale variability in this region. Assimilating surface glider data subsampled at a frequency consistent with available satellite-derived data results in 40 % lower carbon export, primarily resulting from optimized rates generating more slowly sinking diatoms. This
16. An examination of the role of colonial Phaeocystis antarctica in the microbial food web of the Ross Sea
Science.gov (United States)
The extensive buildup of phytoplankton biomass in the Ross Sea conflicts with the view that high rates of herbivory occur in all regions of the Southern Ocean. Nano- and microplanktonic consumers comprise a significant fraction of total plankton biomass; however, the importance o...
17. Influence of submarine morphology on bottom water flow across the western Ross Sea continental margin
Science.gov (United States)
Davey, F.J.; Jacobs, S.S.
2007-01-01
Multibeam sonar bathymetry documents a lack of significant channels crossing outer continental shelf and slope of the western Ross Sea. This indicates that movement of bottom water across the shelf break into the deep ocean in this area is mainly by laminar or sheet flow. Subtle, ~20 m deep and up to 1000 m wide channels extend down the continental slope, into tributary drainage patterns on the upper rise, and then major erosional submarine canyons. These down-slope channels may have been formed by episodic pulses of rapid down slope water flow, some recorded on bottom current meters, or by sub-ice melt water erosion from an icesheet grounded at the margin. Narrow, mostly linear furrows on the continental shelf thought to be caused by iceberg scouring are randomly oriented, have widths generally less than 400 m and depths less than 30m, and extend to water depths in excess of 600 m.
18. New data on Weddell seal (Leptonychotes weddellii colonies: A genetic analysis of a top predator from the Ross Sea, Antarctica.
Directory of Open Access Journals (Sweden)
Ighor Antunes Zappes
Full Text Available In this paper, we studied the genetic variability in Weddell seal from colonies in Terra Nova Bay and Wood Bay, both sites located in the Ross Sea area, Antarctica. Two mitochondrial genes and one nuclear gene, with different mutation rates, were sequenced to investigate the haplotype diversity of the colonies and to test for a possible recent expansion. Fifteen microsatellites were used to analyze their genetic structure. Sequenced genes and microsatellites were also used to estimate the effective population size of the studied colonies and the Ross Sea seal population. The Ross Sea has a high density population of Weddel seals, with an estimated effective number of 50,000 females, and 1,341 individuals for the sampling area, possibly due to its high primary production. The colonies showed high diversity (Hd > 0.90 and many exclusive haplotypes (> 75%, likely a consequence of the surprisingly high site fidelity of Weddell seals, despite the proximity of the colonies. Nevertheless, there was low microsatellite differentiation between colonies, suggesting that they are part of a single larger population. Their expansion seemed to have started during the last glacial cycle (around 58,000 years ago, indicating that the Ross Sea seal populations have been present in the area for long time, probably due to the lack of hunting by humans and terrestrial predation. As a top predator, the role of Weddell seals in the Ross Sea ecology is crucial, and its demographic dynamics should be monitored to follow the future changes of such an important ecosystem.
19. Temporal variability of the Circumpolar Deep Water inflow onto the Ross Sea continental shelf
Science.gov (United States)
Castagno, Pasquale; Falco, Pierpaolo; Dinniman, Michael S.; Spezie, Giancarlo; Budillon, Giorgio
2017-02-01
The intrusion of Circumpolar Deep Water (CDW) is the primary source of heat, salt and nutrients onto Antarctica's continental shelves and plays a major role in the shelf physical and biological processes. Different studies have analyzed the processes responsible for the transport of CDW across the Ross Sea shelf break, but until now, there are no continuous observations that investigate the timing of the intrusions. Also, few works have focused on the effect of the tides that control these intrusions. In the Ross Sea, the CDW intrudes onto the shelf in several locations, but mostly along the troughs. We use hydrographic observations and a mooring placed on the outer shelf in the middle of the Drygalski Trough in order to characterize the spatial and temporal variability of CDW inflow onto the shelf. Our data span from 2004 to the beginning of 2014. In the Drygalski Trough, the CDW enters as a 150 m thick layer between 250 and 400 m, and moves upward towards the south. At the mooring location, about 50 km from the shelf break, two main CDW cores can be observed: one on the east side of the trough spreading along the west slope of Mawson Bank from about 200 m to the bottom and the other one in the central-west side from 200 m to about 350 m depth. A signature of this lighter and relatively warm water is detected by the instruments on the mooring at bottom of the Drygalski Trough. High frequency periodic CDW intrusion at the bottom of the trough is related to the diurnal and spring/neap tidal cycles. At lower frequency, a seasonal variability of the CDW intrusion is noticed. A strong inflow of CDW is observed every year at the end of December, while the CDW inflow is at its seasonal minimum during the beginning of the austral fall. In addition an interannual variability is also evident. A change of the CDW intrusion before and after 2010 is observed.
20. The nepheloid bottom layer and water masses at the shelf break of the western Ross Sea
Science.gov (United States)
Capello, Marco; Budillon, Giorgio; Cutroneo, Laura; Tucci, Sergio
2009-06-01
In the austral summers of 2000/2001 and 2002/2003 the Italian CLIMA Project carried out two oceanographic cruises along the northwestern margin of the Ross Sea, where the Antarctic Bottom Water forms. Here there is an interaction between the water masses on the sea floor of the outer shelf and slope with a consequent evolution of benthic nepheloid layers and an increase in total particulate matter. We observed three different situations: (a) the presence of triads (bottom structures characterized by a concomitant jump in turbidity, temperature, and salinity data) and high re-suspension phenomena related to the presence of the Circumpolar Deep Water and its mixing with cold, salty shelf waters associated with gravity currents; (b) the absence of triads with high re-suspension, implying that when the gravity currents are no longer active the benthic nepheloid layer may persist until the suspended particles settle to the sea floor, suggesting that the turbidity data can be used to study recent gravity current events; and (c) the absence of turbidity and sediment re-suspension phenomena supports the theory that a steady situation had been re-established and the current interaction no longer occurred or had finished sometime before.
1. Modeling the drift of objects floating in the sea
Science.gov (United States)
Nof, D.; Girihagama, L. N.
2016-02-01
The question how buoyant objects drift and where are they ultimately washed ashore must have troubled humans since the beginning of civilization. A good summary of the observational aspect of the problem is given in Ebbesmeyer (2015) and the references given therein. It includes the journey of shoes originally housed in containers that were accidently swept from the deck of cargo ships to the ocean as well as the famous world war two case of a corpse released by the British Counter Intelligence agency near the Spanish Coast. Of practical modern importance is the question how did the flaperon, belonging to the Malaysian Airplane lost last year (supposedly over the Indian Ocean near Western Australia), travelled almost across the entire Indian Ocean in just 15 months (corresponding to the very high speed of six centimeters per-second, about three times the speed of most ocean currents away from boundaries). Traditionally, it has been thought that three processes affect the drift-ocean currents, surface waves and wind. Of these, the last two are usually regarded as small. The waves effect (Stokes drift) is nonlinear and is probably indeed very small in most cases because the amplitudes are small. It is not so easy to estimate the wind effect and we will argue here that it is not necessarily small though it is obviously close to zero in some cases. The wind speed is typically two orders of magnitude faster than the water (meters per second compared to centimeters per second) and the stress is proportional to the square of the wind speed implying that the wind is important even if only a very small portion of the object protrudes above the sea-level. It is argued that wind, rather than ocean current dominated the drift of both the WWII corpse and the modern day flaperon.
2. The paradox of a long grounding during West Antarctic Ice Sheet retreat in Ross Sea.
Science.gov (United States)
Bart, Philip J; Krogmeier, Benjamin J; Bart, Manon P; Tulaczyk, Slawek
2017-04-28
Marine geological data show that the West Antarctic Ice Sheet (WAIS) advanced to the eastern Ross Sea shelf edge during the Last Glacial Maximum (LGM) and eventually retreated ~1000 km to the current grounding-line position on the inner shelf. During the early deglacial, the WAIS deposited a voluminous stack of overlapping grounding zone wedges (GZWs) on the outer shelf of the Whales Deep Basin. The large sediment volume of the GZW cluster suggests that the grounding-line position of the paleo-Bindschadler Ice Stream was relatively stationary for a significant time interval. We used an upper bound estimate of paleo-sediment flux to investigate the lower bound duration over which the ice stream would have deposited sediment to account for the GZW volume. Our calculations show that the cluster represents more than three millennia of ice-stream sedimentation. This long duration grounding was probably facilitated by rapid GZW growth. The subsequent punctuated large-distance (~200 km) grounding-line retreat may have been a highly non-linear ice sheet response to relatively continuous external forcing such as gradual climate warming or sea-level rise. These findings indicate that reliable predictions of future WAIS retreat may require incorporation of realistic calculations of sediment erosion, transport and deposition.
3. Iron Fertilization of the Southern Ocean: Regional Simulation and Analysis of C-Sequestration in the Ross Sea
Energy Technology Data Exchange (ETDEWEB)
Kevin Arrigo
2012-03-13
A modified version of the dynamic 3-dimensional mesoscale Coupled Ice, Atmosphere, and Ocean model (CIAO) of the Ross Sea ecosystem has been used to simulate the impact of environmental perturbations upon primary production and biogenic CO2 uptake. The Ross Sea supports two taxonomically, and spatially distinct phytoplankton populations; the haptophyte Phaeocystis antarctica and diatoms. Nutrient utilization ratios predict that P. antarctica and diatoms will be driven to nitrate and phosphate limitation, respectively. Model and field data have confirmed that the Ross Sea is iron limited with only two-thirds of the macronutrients consumed by the phytoplankton by the end of the growing season. In this study, the CIAO model was improved to simulate a third macronutrient (phosphate), dissolved organic carbon, air-sea gas exchange, and the carbonate system. This enabled us to effectively model pCO2 and subsequently oceanic CO2 uptake via gas exchange, allowing investigations into the affect of alleviating iron limitation on both pCO2 and nutrient drawdown.
4. Seeking an optimal algorithm for a new satellite-based Sea Ice Drift Climate Data Record : Motivations, plans and initial results from the ESA CCI Sea Ice project
DEFF Research Database (Denmark)
Lavergne, T.; Dybkjær, Gorm; Girard-Ardhuin, Fanny
The Sea Ice Essential Climate Variable (ECV) as defined by GCOS pertains of both sea ice concentration, thickness, and drift. Now in its second phase, the ESA CCI Sea Ice project is conducting the necessary research efforts to address sea ice drift.Accurate estimates of sea ice drift direction an...... in the final product. This contribution reviews the motivation for the work, the plans for sea ice drift algorithms intercomparison and selection, and early results from our activity....
5. Oceanographic mechanisms and penguin population increases during the Little Ice Age in the southern Ross Sea, Antarctica
Science.gov (United States)
Yang, Lianjiao; Sun, Liguang; Emslie, Steven D.; Xie, Zhouqing; Huang, Tao; Gao, Yuesong; Yang, Wenqing; Chu, Zhuding; Wang, Yuhong
2018-01-01
The Adélie penguin is a well-known indicator for climate and environmental changes. Exploring how large-scale climate variability affects penguin ecology in the past is essential for understanding the responses of Southern Ocean ecosystems to future global change. Using ornithogenic sediments at Cape Bird, Ross Island, Antarctica, we inferred relative population changes of Adélie penguins in the southern Ross Sea over the past 500 yr, and observed an increase in penguin populations during the Little Ice Age (LIA; 1500-1850 AD). We used cadmium content in ancient penguin guano as a proxy of ocean upwelling and identified a close linkage between penguin dynamics and atmospheric circulation and oceanic conditions. During the cold period of ∼1600-1825 AD, a deepened Amundsen Sea Low (ASL) led to stronger winds, intensified ocean upwelling, enlarged Ross Sea and McMurdo Sound polynyas, and thus higher food abundance and penguin populations. We propose a mechanism linking Antarctic marine ecology and atmospheric/oceanic dynamics which can help explain and predict responses of Antarctic high latitudes ecosystems to climate change.
6. Influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the Ross Sea, Antarctica
Science.gov (United States)
Dinniman, Michael S.; Klinck, John M.; Smith, Walker O.
2007-11-01
Satellite imagery shows that there was substantial variability in the sea ice extent in the Ross Sea during 2001-2003. Much of this variability is thought to be due to several large icebergs that moved through the area during that period. The effects of these changes in sea ice on circulation and water mass distributions are investigated with a numerical general circulation model. It would be difficult to simulate the highly variable sea ice from 2001 to 2003 with a dynamic sea ice model since much of the variability was due to the floating icebergs. Here, sea ice concentration is specified from satellite observations. To examine the effects of changes in sea ice due to iceberg C-19, simulations were performed using either climatological ice concentrations or the observed ice for that period. The heat balance around the Ross Sea Polynya (RSP) shows that the dominant term in the surface heat budget is the net exchange with the atmosphere, but advection of oceanic warm water is also important. The area average annual basal melt rate beneath the Ross Ice Shelf is reduced by 12% in the observed sea ice simulation. The observed sea ice simulation also creates more High-Salinity Shelf Water. Another simulation was performed with observed sea ice and a fixed iceberg representing B-15A. There is reduced advection of warm surface water during summer from the RSP into McMurdo Sound due to B-15A, but a much stronger reduction is due to the late opening of the RSP in early 2003 because of C-19.
7. Modelling study of mesoscale cyclogenesis over Ross Sea, Antarctica, on February 18, 1988
Energy Technology Data Exchange (ETDEWEB)
Stortini, M.; Morelli, S.; Marchesi, S. [Modena e Reggio Emilia Univ., Modena (Italy). Dipt. di Scienze dell' Ingegneria, Sez. Osservatorio Geofisico
2000-04-01
This paper examines the development of a summer event of mesoscale cyclogenesis off the coast of Victoria Land in the presence of katabatic winds, by means of numerical simulations. These refer to the period from 00 UTC 17 February to 00 UTC 19 February 1988 and were performed using the hydrostatic ETA (1993 version) limited area model with resolution 55 km x 55 km x 17 levels. The ETA model reproduces katabatic winds from Terra Nova Bay and a trough on the southwestern Ross Sea. A cyclonic vortex is simulated in the trough, even though it is weaker than the one present in the analysis initialized by the European Center for Medium Range Weather Forecast (Reading, United Kingdom). Idealized simulations with varied surface conditions were also performed. In particular, an ice-covered ocean acts to weaken the atmospheric phenomena, while a no-mountain simulation emphasizes the influence of the orography and the cold winds from the coast of Victoria Land on the mesocyclonic activity.
8. Multiscale Observation System for Sea Ice Drift and Deformation
Science.gov (United States)
Lensu, M.; Haapala, J. J.; Heiler, I.; Karvonen, J.; Suominen, M.
2011-12-01
The drift and deformation of sea ice cover is most commonly followed from successive SAR images. The time interval between the images is seldom less than one day which provides rather crude approximation of the motion fields as ice can move tens of kilometers per day. This is particulary so from the viewpoint of operative services, seeking to provide real time information for ice navigating ships and other end users, as leads are closed and opened or ridge fields created in time scales of one hour or less. The ice forecast models are in a need of better temporal resolution for ice motion data as well. We present experiences from a multiscale monitoring system set up to the Bay of Bothnia, the northernmost basin of the Baltic Sea. The basin generates difficult ice conditions every winter while the ports are kept open with the help of an icebreaker fleet. The key addition to SAR imagery is the use of coastal radars for the monitoring of coastal ice fields. An independent server is used to tap the radar signal and process it to suit ice monitoring purposes. This is done without interfering the basic use of the radars, the ship traffic monitoring. About 20 images per minute are captured and sent to the headquarters for motion field extraction, website animation and distribution. This provides very detailed real time picture of the ice movement and deformation within 20 km range. The real time movements are followed in addition with ice drifter arrays, and using AIS ship identification data, from which the translation of ship cannels due to ice drift can be found out. To the operative setup is associated an extensive research effort that uses the data for ice drift model enhancement. The Baltic ice models seek to forecast conditions relevant to ship traffic, especilly hazardous ones like severe ice compression. The main missing link here is downscaling, or the relation of local scale ice dynamics and kinematics to the ice model scale behaviour. The data flow when
9. Radionuclides in ornithogenic sediments as evidence for recent warming in the Ross Sea region, Antarctica
Energy Technology Data Exchange (ETDEWEB)
Nie, Yaguang [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Key Laboratory of Environmental Toxicology and Pollution Control Technology of Anhui Province, Hefei, Anhui 230031 (China); Xu, Liqiang [School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, Anhui 230009 (China); Liu, Xiaodong, E-mail: [email protected] [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Emslie, Steven D. [Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 S. College Road, Wilmington, NC 28403 (United States)
2016-07-01
Radionuclides including {sup 210}Pb, {sup 226}Ra and {sup 137}Cs were analyzed in eight ornithogenic sediment profiles from McMurdo Sound, Ross Sea region, East Antarctica. Equilibration between {sup 210}Pb and {sup 226}Ra were reached in all eight profiles, enabling the determination of chronology within the past two centuries through the Constant Rate of Supply (CRS) model. Calculated fluxes of both {sup 210}Pb and {sup 137}Cs varied drastically among four of the profiles (MB4, MB6, CC and CL2), probably due to differences in their sedimentary environments. In addition, we found the flux data exhibiting a clear decreasing gradient in accordance with their average deposition rate, which was in turn related to the specific location of the profiles. We believe this phenomenon may correspond to global warming of the last century, since warming-induced surface runoff would bring more inflow water and detritus to the coring sites, thus enhancing the difference among the profiles. To verify this hypothesis, the deposition rate against age of the sediments was calculated based on their determined chronology, which showed ascending trends in all four profiles. The significant increase in deposition rates over the last century is probably attributable to recent warming, implying a potential utilization of radionuclides as environmental indicators in this region. - Highlights: • {sup 210}Pb, {sup 226}Ra and {sup 137}Cs were measured in ornithogenic sediment profiles. • Chronology within 200 years was determined through Constant Rate of Supply model. • Calculated nuclide fluxes decreased with average deposition rate and locations. • Deposition rate over time indicated warming which caused the flux gradient.
10. Cenozoic Tectonic Characteristics in the Adare Basin, West Ross Sea: Evidence From Seismic Profiles
Science.gov (United States)
Zhang, Q.; Gao, J.; Ding, W.
2017-12-01
Based on the geophysical data obtained from the Adare Basin and its adjacent areas, West Ross Sea, the authors employed the frequency wave-number filtering technique to recover the newly processed dataset with high signal noise ratio and complete seismic event which highly contributes to reveal more detailed deep-seated geological structures than previously thought. The structural features and magmatism of the study area in Cenozoic were classified and analyzed. Combined with glaciation, the associated sedimentary facies were summarized systematically. The authors' analysis revealed that, at 16 Ma, under the influence of the thermal effect caused by residual magmatism and asymmetric spreading of Adare Basin in the initial period, surrounding areas of two flanks of the Adare trough were characterized by uplift folds and tilted uplift zone, respectively. The small-scale uplift fold zone was characterized by nearly upright faults and folds and was located in the southern part of the eastern flank, whereas the tilted uplift zone dominated in the corresponding district of western flank that reached the continental margin. By utilizing the contact relationship between igneous rocks and surrounding rocks, igneous rocks can be divided into two periods: early-stage and late Cenozoic igneous rocks. The early-stage rocks are generally located dispersedly in the tilted uplift zone and the age is poorly known. It is suggested that they were related to the residual magmatism. On the other hand, the spatial distribution of Late Cenozoic igneous rocks, formed not earlier 5.5 Ma, was extensive and scattered, almost covering the whole study area, which indicates that they might be unrelated to the rifting in space and time, instead they were affected by decompression melting of the mantle because of the large-scale deglaciation since Pliocene.
11. Summer Distribution of Co2 Partial Pressure In The Ross Sea, Antarctica, and Relations With Biological Activity
Science.gov (United States)
Sandrini, S.; Tositti, L.; Tubertini, O.; Ceradini, S.; Palucci, A.; Barbini, R.; Fantoni, R.; Colao, F.; Ferrari, G. M.
The oceans play a key role in the processes responsible for global climate changes, in fact the oceanic uptake of anthropogenic atmospheric carbon dioxide is estimated to be 17-39The Southern Ocean and Antarctic marginal seas are considered to absorb up to half of this fraction. The Ross Sea, during the summer pack-ice melting, expe- riences rapid seasonal outgrowths, giving rise to phytoplankton blooms, especially in polynya areas near the coast line. This has a direct influence on pCO2 concentration in surface water, and hence on CO2 fluxes between ocean and atmosphere. Both the Ross Sea and the Southern Ocean transect between New Zealand and Antarctica are sys- tematically investigated during Italian Antarctic oceanographic campaigns onboard of the R/V Italica. During the XVI expedition, which took place in January and Febru- ary 2001, simultaneous measurements of surface pCO2 and Chlorophyll-a by laser remote-sensing apparatus were collected. Chlorophyll-a and pCO2 showed a general anticorrelation along the cruise. The survey has revealed the presence of high produc- tive regions in the polynya and close to the ice edge. The linear regression analysis of the chl-a vs pCO2 values improved our knowledge of the time evolution of the phyto- planktonic growth, independently measured by means of the laser yield, thus allowing for discrimination between different initial and final blooms in the Antarctic Ross Sea. The results obtained are here presented and discussed. They confirm the importance of biological production in the net absorption of atmospheric CO2 in continental shelf zones.
12. Preserved Crevasse Casts in the Whales Deep Basin, eastern Ross Sea
Science.gov (United States)
Bart, P. J.; Tulaczyk, S. M.
2017-12-01
A recent seismic stratigraphic study showed that the large bathymetric saddle in the Whales Deep Basin in eastern Ross Sea is a compound grounding zone wedge (CGZW). The basin was occupied by the paleo Bindschadler Ice Stream when grounded ice advanced to the outer continental shelf during the last glacial maximum (LGM). The CGZW is composed of at least seven overlapping GZWs. The crest of the bathymetric saddle corresponds to the grounding zone of GZW7, i.e., the seventh GZW. The north face of the saddle is essentially equivalent to the GZW7 foreset and the south side of the saddle is the GZW7 topset, i.e., the seafloor surface to which the paleo Bindschadler Ice Stream was grounded. The GZW7 topset is mantled by a series of relatively small-amplitude, but very long, ridges with low sinuosity. These ridges were previously imaged by Mosola and Anderson (2006). Here we show a larger-area multibeam survey that was acquired in 2015 during expedition NBP1502B. The larger-area multibeam survey shows that the ridges have amplitudes ranging from 2 to 11 m above grade and have an overall northeast-southwest orientation over an area of at least 500 km2 on the central and western flank of Whales Deep Basin middle continental shelf in water depths ranging from 500 to 550 m. The ridges have spacing that mostly range between 1 and 2 km. The longest ridges are observed to be 40 km. The ridges in the center of the trough have flatter tops than those in the shallower water on the flank of Houtz Bank. In our ongoing investigation of these interesting features, we hypothesize that the ridges formed below a rapidly flowing ice stream as it thinned and was decoupling from the bed towards the end of GZW7 deposition. High ice deformation rates accompanying this process caused the development of large basal crevasses or ice shelf rifts that reached the seafloor. Subglacial till was scraped and collected into lower parts of these crevasses/rifts. Chronologic data indicates that these
13. Predicting responses of the Adélie penguin population of Edmonson Point to future sea ice changes in the Ross Sea
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Tosca eBallerini
2015-02-01
Full Text Available Atmosphere-Ocean General Circulation Models (AOGCMs predict changes in the sea ice environment and in atmospheric precipitations over larger areas of Antarctica. These changes are expected to affect the population dynamics of seabirds and marine mammals, but the extent of this influence is not clear. We investigated the future population trajectories of the colony of Adélie penguins at Edmonson Point, in the Ross Sea, from 2010 to 2100. To do so, we incorporated the relationship between sea ice and demographic parameters of the studied colony into a matrix population model. Specifically, we used sea ice projections from AOGCMs and a proxy for snowfall precipitation. Simulations of population persistence under future climate change scenarios showed that a reduction in sea ice extent and an increase in precipitation events during the breeding season will drive the population to extinction. However, the population growth rate estimated by the model was lower than the population growth rate observed during the last decades, suggesting that recruits from other colonies maintain the observed population dynamics at Edmonson Point. This local ‘rescue’ effect is consistent with a metapopulation dynamic for Adélie penguins in the Ross Sea, in which neighboring colonies might exhibit contrasting population trends and different density-dependent effects. In the hypothesis that connectivity with larger source colonies or that local recruitment would decrease, the sink colony at Edmonson Point is predicted to disappear.
14. Recording and processing procedures for multi-channel seismic-reflection data collected in the western Ross Sea, Antarctica
Science.gov (United States)
Dadisman, Shawn V.; Ryan, Holly F.; Mann, Dennis M.
1987-01-01
During 1984, over 2300 km of multichannel seismic-reflection data were recorded by the U.S. Geological Survey in the western Ross Sea and Iselin Bank regions. A temporary loss and sinking of the streamer led to increasing the streamer tow depth to 20 m, which resulted in some attenuation of frequencies in the 30-50 Hz range but no significant difference in resolution of the stacked data. Severe water bottom multiples were encountered and removed by dip-filtering, weighted stacking, and severe post-NMO muting.
15. One new genus and three new species of deep-sea nematodes (Nematoda: Microlaimidae) from the Southwest Pacific Ocean and Ross Sea.
Science.gov (United States)
Leduc, Daniel
2016-02-11
New deep-sea nematodes of the family Microlaimidae are described from the Southwest Pacific Ocean and Ross Sea. Microlaimus korari n. sp. is characterised by annulated cuticle with longitudinal bars, round amphideal aperture slightly smaller than the cryptospiral amphideal fovea, spacious and heavily cuticularised buccal cavity with large dorsal tooth and right subventral tooth situated anteriorly relative to left subventral tooth, slender spicules 4.4 cloacal body diameters long, and gubernaculum 1.2 cloacal body diameters long with laterally curved distal end and swollen proximal end. Bolbolaimus tongaensis n. sp. is characterised by annulated cuticle with longitudinal bars, oval amphideal aperture and cryptocircular amphideal fovea situated between cephalic setae and only partially surrounded by cuticle annulations, and short spicules cuticularised along dorsal edge and at proximal end and with swollen portion near proximal end. Maragnopsia n. gen. is characterised by a minute, non-cuticularised mouth cavity without teeth, an elongated posterior pharyngeal bulb more than twice as long as it is wide, a single outstretched testis, and a conico-cylindrical tail 13-16 anal body diameters long. A list of all 83 valid Microlaimus species is provided. The present study provides the first microlaimid species records from deep-sea habitats (> 200 m depth) in the Southwest Pacific and Ross Sea. The presence of M. korari n. sp. on both the continental slope of New Zealand and Ross Sea abyssal plain suggests that this species has a wide geographical and depth distribution. However, molecular analyses will be required to confirm the identity of these two geographically disparate populations.
16. Effect of penguin and seal excrement on mercury distribution in sediments from the Ross Sea region, East Antarctica.
Science.gov (United States)
Nie, Yaguang; Liu, Xiaodong; Sun, Liguang; Emslie, Steven D
2012-09-01
Total mercury (Hg) concentration and several other geochemical parameters were determined for five sediment profiles from the Antarctic Ross Sea region. Our data exhibit significant positive correlations between Hg concentration and total organic carbon (TOC) content in all profiles, suggesting the predominant role of organic matter (OM) as a Hg carrier. The OM in the sediments originates primarily from penguin guano and algae. High Hg content in guano and a positive correlation between Hg and a guano bio-element (phosphorus, P) in the ornithogenic sediment profiles (MB6, BI and CC) indicate that Hg was strongly influenced by guano input. The bottom sediments of MB6 with seal hairs contain relatively high Hg. This increase is attributed to the input of seal excrement, suggesting that sedimentary Hg may be an effective trophic-level indicator from seals to penguins. The enrichment factor (EF) for Hg was calculated and the results indicated apparent Hg enrichment in the sediment profiles from the Ross Sea region caused by bio-vectors such as penguins and seals. Compared with typical sediments from other sites in Antarctica and the SQGs (sediment quality guidelines), the total amount of Hg in our study area is still not considered to be adversely high. Copyright © 2012 Elsevier B.V. All rights reserved.
17. Contrasting Photo-physiological Responses of the Haptophyte Phaeocystis Antarctica and the Diatom Pseudonitzschia sp. in the Ross Sea (Antarctica
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Sasha Tozzi
2017-05-01
Full Text Available The Antarctic is a unique environment in which substantial variations in irradiance occur over a number of time scales, and as a result phytoplankton need to acclimate and adapt to these changes. We conducted field and laboratory manipulations in the Ross Sea, Antarctica to examine photophysiological differences between Phaeocystis antarctica and Pseudonitzschia sp. a diatom that commonly occurrs in the Ross Sea, since these are the two functional groups that dominate abundance and productivity. Both exhibited reduced quantum yields due to high irradiances. P. antarctica, a haptophyte, displays a distinct photophysiological response to irradiance when compared to diatoms. P. antarctica showed a rapid recovery from high light exposure, as indicated by the rapid return to initial, high quantum yields, in contrast to diatoms, which responded more slowly. Absorption cross sections were high in both forms, but those in P. antarctica were significantly higher. Both organisms recovered within 24 h to initial quantum yields, suggesting that high irradiance exposure does not have a permanent effect on these organisms. Among all micronutrient additions (iron, cobalt, zinc and vitamin B12, only iron additions resulted in rapid impacts on quantum yields. Iron limitation also can result in reduced photosynthetic efficiency. Understanding these photophysiologial responses and the impact of oceanographic conditions provides constraints on modeling efforts of photosynthesis and primary productivity in the Antarctic.
18. Lithology and chronology of ice-sheet fluctuations (magnetic susceptibility of cores from the western Ross Sea)
Science.gov (United States)
Jennings, Anne E.
1993-01-01
The goals of the marine geology part of WAIS include reconstructing the chronology and areal extent of ice-sheet fluctuations and understanding the climatic and oceanographic influences on ice-sheet history. As an initial step toward attaining these goals, down-core volume magnetic susceptibility (MS) logs of piston cores from three N-S transects in the western Ross Sea are compared. The core transects are within separate petrographic provinces based on analyses of till composition. The provinces are thought to reflect the previous locations of ice streams on the shelf during the last glaciation. Magnetic susceptibility is a function of magnetic mineral composition, sediment texture, and sediment density. It is applied in the western Ross Sea for two purposes: (1) to determine whether MS data differentiates the three transects (i.e., flow lines), and thus can be used to make paleodrainage reconstructions of the late Wisconsinan ice sheet; and (2) to determine whether the MS data can aid in distinguishing basal till diamictons from diamictons of glacial-marine origin and thus, aid paleoenvironmental interpretations. A comparison of the combined data of cores in each transect is presented.
19. Porifera collection of the Italian National Antarctic Museum (MNA, with an updated checklist from Terra Nova Bay (Ross Sea
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Claudio Ghiglione
2018-05-01
Full Text Available This new dataset presents occurrence data for Porifera collected in the Ross Sea, mainly in the Terra Nova Bay area, and curated at the Italian National Antarctic Museum (MNA, section of Genoa. Specimens were collected in 331 different sampling stations at depths ranging from 17 to 1,100 meters in the framework of 17 different Italian Antarctic expeditions funded by the Italian National Antarctic Research Program (PNRA. A total of 807 specimens, belonging to 144 morphospecies (i.e., 95 taxa identified at species level and 49 classified at least at the genus level is included in the dataset. Nearly half (45% of the species reported here correspond to species already known for Terra Nova Bay. Out of the remaining 55% previously unknown records, under a third (~29% were classified at the species level, while over a quarter (~26% were ascribed to the genus level only and these would require further study. All vouchers are permanently curated at the MNA and are available for study to the scientific community. A 3D model of an uncommon species from the Ross Sea, i.e. Tethyopsis brondstedi (Burton, 1929, is also presented and will be made available for outreach purposes.
20. Trends in the breeding population of Adelie penguins in the Ross Sea, 1981-2012: a coincidence of climate and resource extraction effects.
Directory of Open Access Journals (Sweden)
Phil O'B Lyver
Full Text Available Measurements of the size of Adélie penguin (Pygoscelis adeliae colonies of the southern Ross Sea are among the longest biologic time series in the Antarctic. We present an assessment of recent annual variation and trends in abundance and growth rates of these colonies, adding to the published record not updated for more than two decades. High angle oblique aerial photographic surveys of colonies were acquired and penguins counted for the breeding seasons 1981-2012. In the last four years the numbers of Adélie penguins in the Ross and Beaufort Island colonies (southern Ross Sea metapopulation reached their highest levels since aerial counts began in 1981. Results indicated that 855,625 pairs of Adélie penguins established breeding territories in the western Ross Sea, with just over a quarter (28% of those in the southern portion, constituting a semi-isolated metapopulation (three colonies on Ross Island, one on nearby Beaufort Island. The southern population had a negative per capita growth rate of -0.019 during 1981-2000, followed by a positive per capita growth rate of 0.067 for 2001-2012. Colony growth rates for this metapopulation showed striking synchrony through time, indicating that large-scale factors influenced their annual growth. In contrast to the increased colony sizes in the southern population, the patterns of change among colonies of the northern Ross Sea were difficult to characterize. Trends were similar to southern colonies until the mid-1990s, after which the signal was lost owing to significantly reduced frequency of surveys. Both climate factors and recovery of whale populations likely played roles in the trends among southern colonies until 2000, after which depletion of another trophic competitor, the Antarctic toothfish (Dissostichus mawsoni, may explain the sharp increasing trend evident since then.
1. Trends in the Breeding Population of Adélie Penguins in the Ross Sea, 1981–2012: A Coincidence of Climate and Resource Extraction Effects
Science.gov (United States)
Lyver, Phil O’B.; Barron, Mandy; Barton, Kerry J.; Ainley, David G.; Pollard, Annie; Gordon, Shulamit; McNeill, Stephen; Ballard, Grant; Wilson, Peter R.
2014-01-01
Measurements of the size of Adélie penguin (Pygoscelis adeliae) colonies of the southern Ross Sea are among the longest biologic time series in the Antarctic. We present an assessment of recent annual variation and trends in abundance and growth rates of these colonies, adding to the published record not updated for more than two decades. High angle oblique aerial photographic surveys of colonies were acquired and penguins counted for the breeding seasons 1981–2012. In the last four years the numbers of Adélie penguins in the Ross and Beaufort Island colonies (southern Ross Sea metapopulation) reached their highest levels since aerial counts began in 1981. Results indicated that 855,625 pairs of Adélie penguins established breeding territories in the western Ross Sea, with just over a quarter (28%) of those in the southern portion, constituting a semi-isolated metapopulation (three colonies on Ross Island, one on nearby Beaufort Island). The southern population had a negative per capita growth rate of −0.019 during 1981–2000, followed by a positive per capita growth rate of 0.067 for 2001–2012. Colony growth rates for this metapopulation showed striking synchrony through time, indicating that large-scale factors influenced their annual growth. In contrast to the increased colony sizes in the southern population, the patterns of change among colonies of the northern Ross Sea were difficult to characterize. Trends were similar to southern colonies until the mid-1990s, after which the signal was lost owing to significantly reduced frequency of surveys. Both climate factors and recovery of whale populations likely played roles in the trends among southern colonies until 2000, after which depletion of another trophic competitor, the Antarctic toothfish (Dissostichus mawsoni), may explain the sharp increasing trend evident since then. PMID:24621601
2. Increased Arctic sea ice drift alters adult female polar bear movements and energetics.
Science.gov (United States)
Durner, George M; Douglas, David C; Albeke, Shannon E; Whiteman, John P; Amstrup, Steven C; Richardson, Evan; Wilson, Ryan R; Ben-David, Merav
2017-09-01
Recent reductions in thickness and extent have increased drift rates of Arctic sea ice. Increased ice drift could significantly affect the movements and the energy balance of polar bears (Ursus maritimus) which forage, nearly exclusively, on this substrate. We used radio-tracking and ice drift data to quantify the influence of increased drift on bear movements, and we modeled the consequences for energy demands of adult females in the Beaufort and Chukchi seas during two periods with different sea ice characteristics. Westward and northward drift of the sea ice used by polar bears in both regions increased between 1987-1998 and 1999-2013. To remain within their home ranges, polar bears responded to the higher westward ice drift with greater eastward movements, while their movements north in the spring and south in fall were frequently aided by ice motion. To compensate for more rapid westward ice drift in recent years, polar bears covered greater daily distances either by increasing their time spent active (7.6%-9.6%) or by increasing their travel speed (8.5%-8.9%). This increased their calculated annual energy expenditure by 1.8%-3.6% (depending on region and reproductive status), a cost that could be met by capturing an additional 1-3 seals/year. Polar bears selected similar habitats in both periods, indicating that faster drift did not alter habitat preferences. Compounding reduced foraging opportunities that result from habitat loss; changes in ice drift, and associated activity increases, likely exacerbate the physiological stress experienced by polar bears in a warming Arctic. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.
3. Assimilating bio-optical glider data during a phytoplankton bloom in the southern Ross Sea
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D. E. Kaufman
2018-01-01
Full Text Available The Ross Sea is a region characterized by high primary productivity in comparison to other Antarctic coastal regions, and its productivity is marked by considerable variability both spatially (1–50 km and temporally (days to weeks. This variability presents a challenge for inferring phytoplankton dynamics from observations that are limited in time or space, which is often the case due to logistical limitations of sampling. To better understand the spatiotemporal variability in Ross Sea phytoplankton dynamics and to determine how restricted sampling may skew dynamical interpretations, high-resolution bio-optical glider measurements were assimilated into a one-dimensional biogeochemical model adapted for the Ross Sea. The assimilation of data from the entire glider track using the micro-genetic and local search algorithms in the Marine Model Optimization Testbed improves the model–data fit by ∼ 50 %, generating rates of integrated primary production of 104 g C m−2 yr−1 and export at 200 m of 27 g C m−2 yr−1. Assimilating glider data from three different latitudinal bands and three different longitudinal bands results in minimal changes to the simulations, improves the model–data fit with respect to unassimilated data by ∼ 35 %, and confirms that analyzing these glider observations as a time series via a one-dimensional model is reasonable on these scales. Whereas assimilating the full glider data set produces well-constrained simulations, assimilating subsampled glider data at a frequency consistent with cruise-based sampling results in a wide range of primary production and export estimates. These estimates depend strongly on the timing of the assimilated observations, due to the presence of high mesoscale variability in this region. Assimilating surface glider data subsampled at a frequency consistent with available satellite-derived data results in 40 % lower carbon export, primarily
4. Crustose corallinaceous algae (Rhodophyta) of the New Zealand and United States scientific expedition to the Ross Sea, Balleny Islands, and Macquarie Ridge, 1965
NARCIS (Netherlands)
Zaneveld, Jacques S.; Sanford, Robert B.
1980-01-01
Fourteen taxa of crustose Corallinaceae are described from a collection of marine algae picked up in Antarctic and sub-Antarctic waters along a Ross Sea — Balleny Islands — Macquarie Island traject aboard the USS Glacier in 1965. Three of these taxa are newly described, i.e. Lithothamnium
5. Electromagnetic backscattering from one-dimensional drifting fractal sea surface II: Electromagnetic backscattering model
International Nuclear Information System (INIS)
Xie Tao; Zhao Shang-Zhuo; Fang He; Yu Wen-Jin; He Yi-Jun; Perrie, William
2016-01-01
Sea surface current has a significant influence on electromagnetic (EM) backscattering signals and may constitute a dominant synthetic aperture radar (SAR) imaging mechanism. An effective EM backscattering model for a one-dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant influence on EM backscattering signals from the sea surface. The normalized radar cross section (NRCS) discrepancies between the model for a coupled wave-current fractal sea surface and the model for an uncoupled fractal sea surface increase with the increase of incidence angle, as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the wave can weaken the EM backscattering signal intensity, while the EM backscattering signal is intensified by ocean currents propagating oppositely to the wave direction. The model presented in this paper can be used to study the SAR imaging mechanism for a drifting sea surface. (paper)
6. Increase in penguin populations during the Little Ice Age in the Ross Sea, Antarctica.
Science.gov (United States)
Hu, Qi-Hou; Sun, Li-Guang; Xie, Zhou-Qing; Emslie, Steven D; Liu, Xiao-Dong
2013-01-01
Penguins are an important seabird species in Antarctica and are sensitive to climate and environmental changes. Previous studies indicated that penguin populations increased when the climate became warmer and decreased when it became colder in the maritime Antarctic. Here we determined organic markers in a sediment profile collected at Cape Bird, Ross Island, high Antarctic, and reconstructed the history of Adélie penguin colonies at this location over the past 700 years. The region transformed from a seal to a penguin habitat when the Little Ice Age (LIA; 1500-1800 AD) began. Penguins then became the dominant species. Penguin populations were the highest during ca. 1490 to 1670 AD, a cold period, which is contrary to previous results in other regions much farther north. Different responses to climate change may occur at low latitudes and high latitudes in the Antarctic, even if for same species.
7. Intra-seasonal variation in foraging behavior among Adélie penguins (Pygocelis adeliae) breeding at Cape Hallett, Ross Sea, Antarctica
Science.gov (United States)
Lyver, P.O.B.; MacLeod, C.J.; Ballard, G.; Karl, B.J.; Barton, K.J.; Adams, J.; Ainley, D.G.; Wilson, P.R.
2011-01-01
We investigated intra-seasonal variation in foraging behavior of chick-rearing Adélie penguins, Pygoscelis adeliae, during two consecutive summers at Cape Hallett, northwestern Ross Sea. Although foraging behavior of this species has been extensively studied throughout the broad continental shelf region of the Ross Sea, this is the first study to report foraging behaviors and habitat affiliations among birds occupying continental slope waters. Continental slope habitat supports the greatest abundances of this species throughout its range, but we lack information about how intra-specific competition for prey might affect foraging and at-sea distribution and how these attributes compare with previous Ross Sea studies. Foraging trips increased in both distance and duration as breeding advanced from guard to crèche stage, but foraging dive depth, dive rates, and vertical dive distances travelled per hour decreased. Consistent with previous studies within slope habitats elsewhere in Antarctic waters, Antarctic krill (Euphausia superba) dominated chick meal composition, but fish increased four-fold from guard to crèche stages. Foraging-, focal-, and core areas all doubled during the crèche stage as individuals shifted distribution in a southeasterly direction away from the coast while simultaneously becoming more widely dispersed (i.e., less spatial overlap among individuals). Intra-specific competition for prey among Adélie penguins appears to influence foraging behavior of this species, even in food webs dominated by Antarctic krill.
8. Western Ross Sea and McMurdo Sound Ice Forecasting Guide.
Science.gov (United States)
1975-06-01
areal ice distribution and follow the sane historical proqression of pack disintergration . This technique assumes that environmental conditions...30-day) are based on historical ice data which cxnbine averaae disintergration rates as well as averace wind and current drift. Iong-range wind...original 2 to 3 okta area and its new cnfiguration remains the same, the products of ocnoentrations and widths at the verifying time must equal the
9. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 05 February 1992 to 28 February 1992 (NODC Accession 0000888)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE. Data were collected from 05...
10. Temperature profile and nutrients data collected using bottle casts from the NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 16 December 1995 to 13 January 1996 (NODC Accession 0000889)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the NATHANIEL B. PALMER. Data were collected from...
11. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 08 October 1996 to 06 November 1996 (NODC Accession 0000894)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from POLAR DUKE. Data were collected from 08 October...
12. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 08 April 1997 to 05 May 1997 (NODC Accession 0000897)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...
13. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 06 September 1996 to 12 September 1996 (NODC Accession 0000890)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from POLAR DUKE. Data were collected from 06 September...
14. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE and NATHANIEL B. PALMER in the Ross Sea and Southern Oceans from 10 November 1997 to 12 December 1997 (NODC Accession 0000898)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE and NATHANIEL B. PALMER. Data were...
15. Temperature profile and nutrients data collected using bottle casts from the POLAR DUKE in the Ross Sea and Southern Oceans from 13 November 1996 to 26 November 1996 (NODC Accession 0000895)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Temperature profile and nutrients data were collected using bottle casts in the Ross Sea and Southern Oceans from the POLAR DUKE. Data were collected from 13...
16. Drift data of the sea-gravity meter (SL-2) installed on the R/V Hakurei-maru; Hakureimaru senjo jurokei (SL-2) no drift ni tsuite
Energy Technology Data Exchange (ETDEWEB)
Joshima, M [Geological Survey of Japan, Tsukuba (Japan); Ishihara, T [Japan National Oil Corp., Tokyo (Japan)
1996-05-01
This paper reports a rapid change in the drift of a sea-gravity meter SL-2 after 1987 and after its modification in 1993. In order to confirm the accuracy of the sea-gravity meter of the Hakurei-maru, changes in the lapse of time were summarized on the relative gravity value at the Funabashi base and on the drift rate in each voyage. The drift rates in the case of departing from and returning to Funabashi base were all less than 0.1mgal/day except the first year of 1987, which was presumably due to the growing stability of the gravimeter. The drift value of 1992 was 0.05mgal/day, producing an error of only 2mgal without drift compensation at the end of a 40 day voyage. The gravimeter after the total renewal of the control part in 1993 produced a large drift in the direction opposite to the conventional drift. The cause of these phenomena was supposed to be some kind of change in the spring property during the gap of one year; this large drift seemed to be settling down after the elapse of approximately one year. 4 refs., 8 figs., 2 tabs.
17. Influence of Ross Sea Bottom Water changes on the warming and freshening of the Antarctic Bottom Water in the Australian-Antarctic Basin
Directory of Open Access Journals (Sweden)
2012-07-01
Full Text Available Changes to the properties of Antarctic Bottom Water in the Australian-Antarctic Basin (AA-AABW between the 1990s and 2000s are documented using data from the WOCE Hydrographic Program (WHP and repeated hydrographic surveys. Strong cooling and freshening are observed on isopycnal layers denser than γn = 28.30 kg m−3. Changes in the average salinity and potential temperature below this isopycnal correspond to a basin-wide warming of 1300 ± 200 GW and freshening of 24 ± 3 Gt year−1. Recent changes to dense shelf water in the source regions in the Ross Sea and George V Land can explain the freshening of AA-AABW but not its extensive warming. An alternative mechanism for this warming is a decrease in the supply of AABW from the Ross Sea (RSBW. Hydrographic profiles between the western Ross Sea and George V Land (171–158° E were analyzed with a simple advective-diffusive model to assess the causes of the observed changes. The model suggests that the warming of RSBW observed between the 1970s and 2000s can be explained by a 21 ± 23% reduction in RSBW transport and the enhancement of the vertical diffusion of heat resulting from a 30 ± 7% weakening of the abyssal stratification. The documented freshening of Ross Sea dense shelf water leads to a reduction in both salinity and density stratification. Therefore the direct freshening of RSBW at its source also produces an indirect warming of the RSBW. A simple box model suggests that the changes in RSBW properties and volume transport (a decrease of 6.7% is assumed between the year 1995 and 2005 can explain 51 ± 6% of the warming and 84 ± 10% of the freshening observed in AA-AABW.
18. Dissolved rare earth elements in the central-western sector of the Ross Sea, Southern Ocean: Geochemical tracing of seawater masses.
Science.gov (United States)
Turetta, Clara; Barbaro, Elena; Capodaglio, Gabriele; Barbante, Carlo
2017-09-01
The present essay contributes to the existing literature on rare earth elements (REEs) in the southern hemisphere by presenting the first data, to our knowledge, on the vertical profiles of dissolved REEs in 71 samples collected in the central-western sector of the Ross Sea (Southern Ocean-SO). The REEs were measured in the water samples collected during the 2002-2003 and 2005-2006 austral summers. 4 samples were collected and analysed in the framework of a test experiment, as part of the WISSARD Project (Whillans Ice Stream Subglacial Access Research Drilling). Our results show significant differences between the REE patterns of the main water masses present in the SO: we could observe specific signature in the High Salinity Shelf Water (HSSW), Ice Shelf Water (ISW) and Low Salinity Shelf Water (LSSW). A significant increase in Terbium (Tb) concentration was observed in the HSSW and ISW, the two principal water masses contributing to the formation of Antarctic Bottom Water (AABW) in the Ross Sea area, and in LSSW. Some of the HSSW samples show enrichment in Neodymium (Nd). Dissolved REE could therefore be used as tracers to understand the deep circulation of the SO (Pacific sector). We hypothesize that: (I) the characteristic dissolved REE pattern may derive from the composition of source area and from the hydrothermal activity of the central-western area of the Ross Sea; (II) the Tb anomaly observed in the AABW on the South Australian platform could be partially explained by the contribution of AABW generated in the Ross Sea region. Copyright © 2017 Elsevier Ltd. All rights reserved.
19. Ice formation and growth shape bacterial community structure in Baltic Sea drift ice.
Science.gov (United States)
Eronen-Rasimus, Eeva; Lyra, Christina; Rintala, Janne-Markus; Jürgens, Klaus; Ikonen, Vilma; Kaartokallio, Hermanni
2015-02-01
Drift ice, open water and under-ice water bacterial communities covering several developmental stages from open water to thick ice were studied in the northern Baltic Sea. The bacterial communities were assessed with 16S rRNA gene terminal-restriction fragment length polymorphism and cloning, together with bacterial abundance and production measurements. In the early stages, open water and pancake ice were dominated by Alphaproteobacteria and Actinobacteria, which are common bacterial groups in Baltic Sea wintertime surface waters. The pancake ice bacterial communities were similar to the open-water communities, suggesting that the parent water determines the sea-ice bacterial community in the early stages of sea-ice formation. In consolidated young and thick ice, the bacterial communities were significantly different from water bacterial communities as well as from each other, indicating community development in Baltic Sea drift ice along with ice-type changes. The thick ice was dominated by typical sea-ice genera from classes Flavobacteria and Gammaproteobacteria, similar to those in polar sea-ice bacterial communities. Since the thick ice bacterial community was remarkably different from that of the parent seawater, results indicate that thick ice bacterial communities were recruited from the rarer members of the seawater bacterial community. © FEMS 2014. All rights reserved. For permissions, please e-mail: [email protected].
20. Dissolved inorganic carbon, alkalinity, temperature, salinity and other variables collected from discrete sample and profile observations using CTD, bottle and other instruments from the JAMES CLARK ROSS in the North Greenland Sea and Norwegian Sea from 1996-07-20 to 1996-08-22 (NODC Accession 0113757)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0113757 includes chemical, discrete sample, physical and profile data collected from JAMES CLARK ROSS in the North Greenland Sea and Norwegian Sea...
1. Chemical evidence of the changes of the Antarctic Bottom Water ventilation in the western Ross Sea between 1997 and 2003
Science.gov (United States)
Rivaro, Paola; Massolo, Serena; Bergamasco, Andrea; Castagno, Pasquale; Budillon, Giorgio
2010-05-01
Data from three Italian CLIMA project cruises between 1997 and 2003 were used to obtain sections of the hydrographic and chemical properties of the main water masses across the shelf break off Cape Adare (western Ross Sea, Antarctica). Dissolved oxygen, nitrate and phosphate data were combined on the basis of the Redfield ratio to obtain the quasi-conservative tracers NO (9[NO 3]+[O 2]), PO (135[PO 4]+[O 2]) and phosphate star PO4* ( PO4*=[PO 4]+[O 2]/175-1.95). In 1997 and 2003 the presence of the High Salinity Shelf Water at the bottom depth near the sill was traced by both physical and chemical measurements. In 2001 the Modified Shelf Water, characterized by warmer temperature and by a lower dissolved oxygen content than High Salinity Shelf Water, was observed at the shelf edge. The distribution of the chemical tracers together with the hydrographic observations showed recently formed Antarctic Bottom Water on the continental slope during all of the cruises. These observations were confirmed by the extended optimum multiparameter analysis. The calculated thickness of the new Antarctic Bottom Water, as well as the tracer content, were variable in time and in space. The estimated volume of the new Antarctic Bottom Water and the export of dissolved oxygen and nutrient associated with the overflowing water were different over the examined period. In particular, a lower (˜55%) export was evidenced in 2001 compared to 1997.
2. Rossing uranium
International Nuclear Information System (INIS)
Anon.
1979-01-01
In this article the geology of the deposits of the Rossing uranium mine in Namibia is discussed. The planning of the open-pit mining, the blasting, drilling, handling and the equipment used for these processes are described
3. Alf Ross
DEFF Research Database (Denmark)
Ryberg, Jesper
En (overvejende) ny generation af akademikere møder og prøver Ross' tanker om emner som retfærdighed, demokrati, statsforfatningsret, ytringsfrihed, straf, erkendelsesteori, etik, logik, fri vilje og sygdom.......En (overvejende) ny generation af akademikere møder og prøver Ross' tanker om emner som retfærdighed, demokrati, statsforfatningsret, ytringsfrihed, straf, erkendelsesteori, etik, logik, fri vilje og sygdom....
4. Oceanic fronts in the Sargasso Sea control the early life and drift of Atlantic eels
DEFF Research Database (Denmark)
Munk, Peter; Hansen, Michael Møller; Maas, Gregory E.
2010-01-01
Anguillid freshwater eels show remarkable life histories. In the Atlantic, the European eel (Anguilla anguilla) and American eel (Anguilla rostrata) undertake extensive migrations to spawn in the oceanic Sargasso Sea, and subsequently the offspring drift to foraging areas in Europe and North......, during a field expedition to the eel spawning sites in the Sargasso Sea, we carried out a wide range of dedicated bio-physical studies across areas of eel larval distribution. Our findings suggest a key role of oceanic frontal processes, retaining eel larvae within a zone of enhanced feeding conditions...
5. Summer Epiphytic Diatoms from Terra Nova Bay and Cape Evans (Ross Sea, Antarctica) - A Synthesis and Final Conclusions
Science.gov (United States)
Majewska, Roksana; Convey, Peter; De Stefano, Mario
2016-01-01
Despite recent advances in polar marine biology and related fields, many aspects of the ecological interactions that are crucial for the functioning of Antarctic shallow water habitats remain poorly understood. Although epiphytic diatoms play an essential role in the Antarctic marine food web, basic information regarding their ecology, biodiversity and biogeography is largely unavailable. Here, we synthesise studies on Ross Sea epiphytic diatoms collected during 11 summer Antarctic expeditions between the years 1989/90 and 2011/12, presenting a full list of diatom taxa associated with three macroalgal species (Iridaea cordata, Phyllophora antarctica, and Plocamium cartilagineum) and their epiphytic sessile fauna. Diatom communities found during the three summer months at various depths and sampling stations differed significantly in terms of species composition, growth form structure and abundances. Densities ranged from 21 to >8000 cells mm-2, and were significantly higher on the surface of epiphytic micro-fauna than on any of the macroalgal species examined. Generally, host organisms characterized by higher morphological heterogeneity (sessile microfauna, ramified Plocamium) supported richer diatom communities than those with more uniform surfaces (Iridaea). Differences between epiphytic communities associated with different macroalgae were reflected better in species composition than in growth form structure. The latter changed significantly with season, which was related strongly to the changing ice conditions. A general trend towards an increasing number of erect forms in deeper waters and tube-dwelling diatoms in the shallowest sites (2–5 m) was also observed. This study explores further important and largely previously unknown aspects of relationships and interactions between Antarctic epiphytic diatoms and their micro- and macro-environments. PMID:27078637
6. Shifts in Ross Sea food web structure as indicated by δ15N and δ13C values of fossil Antarctic seals
Science.gov (United States)
Leopold, A.; Brault, E.; McMahon, K.
2013-12-01
As climate change continues to mount, there is a growing need for understanding its effects on biological-physical interactions of marine ecosystems. Assessing the effects of anthropogenic activities on the coastal marine ecosystem involves understanding the underlying mechanisms driving these changes as well as establishing baselines of the natural system. Preliminary findings have indicated shifts in bulk carbon (C) and nitrogen (N) isotopic values of southern elephant seal (Mirounga leonina) samples, collected in the Dry Valleys of Antarctica in the Ross Sea region, over approximately the last 7,000 years. These shifts could result from 1) seals changing their foraging location and/or diet over this time, 2) climate change-induced shifts in the biogeochemistry at the base of the food web, or 3) some combination of both processes. We explored the patterns of long-term change in Ross Sea food web structure by examining the stable isotope values of three top predators in this system, Weddell seals (Leptonychotes weddellii), leopard seals (Hydrurga leptonyx), and crabeater seals (Lobodon carcinophagus). Fossil seal samples were collected in the Dry Valleys during the austral summer of 2012/13 and then analyzed for bulk C and N isotopes via an elemental analyzer/isotope-ratio mass spectrometer (EA/IRMS). Our initial findings indicate that C isotopic values of fossil seal samples from Weddell, leopard, and crabeater seals were more enriched than isotopic values of modern seals of the same species (e.g., δ13C = -22.79 × 0.92 ‰ and -26.71 × 0.50 ‰ for fossil and modern crabeater seals, respectively). Given the relatively consistent diet of crabeater seals, these findings suggest a shift in baseline food web structure occurred over the last 10,000 years, either through changes in foraging location or local shifts in biogeochemistry. For all species, N isotopic values are widely variable (e.g., 7.28 to 16.0 δ15N ‰ for the Weddell seal), which may be a result of
7. Marc Ross
Marc Ross. Articles written in Pramana – Journal of Physics. Volume 69 Issue 6 December 2007 pp 1147-1150 Machine Detector Interface. A laser-wire system for the International Linear Collider · Nicolas Delerue Sudhir Dixit Fred Gannaway David Howell Myriam Qurshi Grahame Blair Stewart Boogert Gary Boorman ...
8. Rossing update
International Nuclear Information System (INIS)
Griebel, E.G.
2000-01-01
Rossing Uranium, along with the rest of the industry, has been undergoing major changes to adjust to the increasingly competitive uranium market in the 1990's. This paper will outline the developments during the 1990's at the mine, as well as current projects. Rossing has successfully managed the transition through a phase of very low production in the first half of the 1990's, and is now operating at 70% of capacity. During this phase the mine was also able to implement tailings and water management strategies which have reduced fresh water requirements to historical lows, whilst preserving process performance despite cessation of iron oxide supplies. Capital investment in mining equipment, a pre-screening facility in the Fine Crushing plant, and currently an ore sorting pilot plant have been made to enhance Rossing's ability to lower costs further. Rossing is in the middle of a business improvement programme aimed at cutting unit costs in excess of 20%, whilst continuing to improve safety, health and environmental performance. Key focus areas of this programme are maintenance strategy, equipment and plant utilisation and people development. (author)
9. Scaling aspects of the sea-ice-drift dynamics and pack fracture
Directory of Open Access Journals (Sweden)
A. Chmel
2007-05-01
Full Text Available A study of the sea-ice dynamics in the periods of time prior to and during the cycles of basin-wide fragmentation of the ice cover in the Arctic Ocean is presented. The fractal geometry of the ice-sheets limited by leads and ridges was assessed using the satellite images, while the data on the correlated sea-ice motion were obtained in the research stations "North Pole 32" and "North Pole 33" established on the ice pack. The revealed decrease of the fractal dimension as a result of large-scale fragmentation is consistent with the localization of the fracture process (leads propagation. At the same time, the scaling properties of the distribution of amplitudes of ice-fields accelerations were insensitive to the event of sea-ice fragmentation. The temporal distribution of the accelerations was scale-invariant during "quiet" periods of sea-ice drift but disordered in the period of mechanical perturbation. The period of decorrelated (in time ice-field motion during the important fracture event was interpreted as an inter-level transition in the hierarchic dynamical system. The mechanism of the long-range correlations in the sea-ice cover, including the fracture process, is suggested to be in relation with the self-organized oscillation dynamics inherent in the ice pack.
10. The Sinking and Spreading of The Antarctic Deep Ice Shelf Water In The Ross Sea Studied By In Situ Observaions and Numerical Modeling
Science.gov (United States)
Rubino, A.; Budillon, G.; Pierini, S.; Spezie, G.
The sinking and spreading of the Deep Ice Shelf Water (DISW) in the Ross Sea are analyzed using in situ observations and the results of a nonlinear, reduced-gravity, frontal layered numerical "plume" model which is able to simulate the motion of a bottom-arrested current over realistic topography. The model is forced by prescribing the thickness of the DISW vein as well as its density structure at the southern model boundary. The ambient temperature and salinity are imposed using hydrographic data acquired by the Italian PNRA-CLIMA project. In the model water of the quiescent ambient ocean is allowed to entrain in the active deep layer due to a simple param- eterization of turbulent mixing. The importance of forcing the model with a realistic ambient density is demonstrated by carrying out a numerical simulation in which the bottom active layer is forced using an idealized ambient density. In a more realis- tic simulation the path and the density structure of the DISW vein flowing over the Challenger Basin are obtained and are found to be in good agreement with data. The evolution of the deep current beyond the continental shelf is also simulated. It provides useful information on the water flow and mixing in a region of the Ross Sea where the paucity of experimental data does not allow for a detailed description of the deep ocean dynamics.
11. A seasonal study of dissolved cobalt in the Ross Sea, Antarctica: micronutrient behavior, absence of scavenging, and relationships with Zn, Cd, and P
Directory of Open Access Journals (Sweden)
M. A. Saito
2010-12-01
Full Text Available We report the distribution of cobalt (Co in the Ross Sea polynya during austral summer 2005–2006 and the following austral spring 2006. The vertical distribution of total dissolved Co (dCo was similar to soluble reactive phosphate (PO43−, with dCo and PO43− showing a significant correlation throughout the water column (r2 = 0.87, 164 samples. A strong seasonal signal for dCo was observed, with most spring samples having concentrations ranging from ~45–85 pM, whereas summer dCo values were depleted below these levels by biological activity. Surface transect data from the summer cruise revealed concentrations at the low range of this seasonal variability (~30 pM dCo, with concentrations as low as 20 pM observed in some regions where PO43− was depleted to ~0.1 μM. Both complexed Co, defined as the fraction of dCo bound by strong organic ligands, and labile Co, defined as the fraction of dCo not bound by these ligands, were typically observed in significant concentrations throughout the water column. This contrasts the depletion of labile Co observed in the euphotic zone of other ocean regions, suggesting a much higher bioavailability for Co in the Ross Sea. An ecological stoichiometry of 37.6 μmol Co:mol−1 PO43− calculated from dissolved concentrations was similar to values observed in the subarctic Pacific, but approximately tenfold lower than values in the Eastern Tropical Pacific and Equatorial Atlantic. The ecological stoichiometries for dissolved Co and Zn suggest a greater overall use of Zn relative to Co in the shallow waters of the Ross Sea, with a Co:PO43−/Zn:PO43− ratio of 1:17. Comparison of these observed stoichiometries with values estimated in culture studies suggests that Zn is a key micronutrient that likely influences phytoplankton diversity in the Ross
12. Variability of scaling time series in the Arctic sea-ice drift dynamics
Directory of Open Access Journals (Sweden)
A. Chmel
2010-02-01
Full Text Available The motion of an individual ice floe in the Arctic Ocean was monitored at the Russian research station North Pole 35 established on the ice pack in 2008. The ice floe speed (V was found to be correlated with wind speed (v in main features, such as the positions of maxima and minima of V and v. However, the fine structure of the V-variation cannot be explained by the wind forcing alone. There were periods of time when the floe drift was affected by the interactions of ice floes between each other or by the periodical forcing due to either the Coriolis inertia effect or the tidal activity. These data were compared with the "waiting times" statistics that are the distributions of time intervals between subsequent, sufficiently strong changes in the kinetic energy of drifting ice floe. These distributions were measured in several time windows differing in the average wind speed and wind direction, and/or in the mechanical state of the ice pack. The distribution functions N (t>τ, where N is the number of successive events of energy change separated by the time interval t that exceeds τ, constructed in different time windows demonstrate fractal or a multifractal nature of the time series during motion in the consolidated ice pack but were truly random when the ice floe drifted in the highly fragmented sea ice. The latter result shows the existence of a relationship between the long-range mechanical interactions in the pack and long-term memory (time scaling behaviour of the sea-ice motion.
13. Drift in salinity data from Argo profiling floats in the Sea of Japan
Digital Repository Service at National Institute of Oceanography (India)
Pankajakshan, T.; Bajish, C.C.; Behera, S.; Gopalakrishna, V.V.
In drift analysis of salinity sensors, one major problem is the difficulty in delineating sensor drift from water mass changes. In the present study, a new method is proposed for finding sensor drift that is free from water mass changes...
14. Iron-oxide Magnetic, Morphologic, and Compositional Tracers of Sediment Provenance and Ice Sheet Extent in the ANDRILL AND-1B Drill Core, Ross Sea, Antarctica (Invited)
Science.gov (United States)
Brachfeld, S. A.; Pinzon, J.; Darley, J. S.; Sagnotti, L.; Kuhn, G.; Florindo, F.; Wilson, G. S.; Ohneiser, C.; Monien, D.; Joseph, L. H.
2013-12-01
The first drilling season of the Antarctic Drilling Program (ANDRILL) recovered a 13.57 million year Miocene through Pleistocene record of paleoclimate change (core AND-1B) within the Ross Sea. The magnetic mineral assemblage records the varying contributions of biological productivity, changing sediment sources, the emergence of volcanic centers, and post-depositional diagenesis. Characterization of bedrock samples from the McMurdo Volcanic Group (MVG) and Transantarctic Mountain (TAM) lithologic units allows us to construct fingerprints for the major source rocks bordering the Ross Sea, and identify their signatures within the AND-1B sediment. Key parameters that can be traced from source rock to sediment for the MVG-derived sediment include a 100-200 C order-disorder transition, titanomaghemite grains with homogenous textures but with substantial Al and Mg content, Fe-spinels with substantial Al, Cr, Mg, and Ti content, and titanomagnetite host grains with 1-3 swarms of ilmenite lamellae (both with variable amounts of oxidation). Distinctive signatures in TAM lithologies include low S-ratios in Koettlitz Group gneisses and Fe-sulfides with magnetite intergrowths in Byrd Glacier basement samples. The Cambrian Granite Harbor Intrusive Complex is characterized by coarse, homogeneous Mn-bearing ilmenite and nearly pure magnetite. The Jurassic dolerites and basalts of the Ferrar Group contain pseudo single domain to stable single domain-sized Fe-oxides with low-Ti content and homogeneous textures. Cu-Fe sulfides are also present in the Ferrar Group. Diamictites in the Pliocene-Pleistocene section of the AND-1B drill core contains Fe-oxide assemblages with MVG-type rock magnetic and textural characteristics, while the Miocene diamictites contain TAM-type signatures. These observations can be explained by increased ice flow from the west during the Miocene and/or the absence of MVG volcanic centers, which had not yet reached a significant size. During the Pliocene and
15. Climate drift of AMOC, North Atlantic salinity and arctic sea ice in CFSv2 decadal predictions
Science.gov (United States)
Huang, Bohua; Zhu, Jieshun; Marx, Lawrence; Wu, Xingren; Kumar, Arun; Hu, Zeng-Zhen; Balmaseda, Magdalena A.; Zhang, Shaoqing; Lu, Jian; Schneider, Edwin K.; Kinter, James L., III
2015-01-01
There are potential advantages to extending operational seasonal forecast models to predict decadal variability but major efforts are required to assess the model fidelity for this task. In this study, we examine the North Atlantic climate simulated by the NCEP Climate Forecast System, version 2 (CFSv2), using a set of ensemble decadal hindcasts and several 30-year simulations initialized from realistic ocean-atmosphere states. It is found that a substantial climate drift occurs in the first few years of the CFSv2 hindcasts, which represents a major systematic bias and may seriously affect the model's fidelity for decadal prediction. In particular, it is noted that a major reduction of the upper ocean salinity in the northern North Atlantic weakens the Atlantic meridional overturning circulation (AMOC) significantly. This freshening is likely caused by the excessive freshwater transport from the Arctic Ocean and weakened subtropical water transport by the North Atlantic Current. A potential source of the excessive freshwater is the quick melting of sea ice, which also causes unrealistically thin ice cover in the Arctic Ocean. Our sensitivity experiments with adjusted sea ice albedo parameters produce a sustainable ice cover with realistic thickness distribution. It also leads to a moderate increase of the AMOC strength. This study suggests that a realistic freshwater balance, including a proper sea ice feedback, is crucial for simulating the North Atlantic climate and its variability.
16. Evidence of calcium carbonates in coastal (Talos Dome and Ross Sea area) East Antarctica snow and firn: Environmental and climatic implications
Science.gov (United States)
Sala, M.; Delmonte, B.; Frezzotti, M.; Proposito, M.; Scarchilli, C.; Maggi, V.; Artioli, G.; Dapiaggi, M.; Marino, F.; Ricci, P. C.; De Giudici, G.
2008-07-01
Micrometre-sized aeolian dust particles stored in Antarctic firn and ice layers are a useful tool for reconstructing climate and environmental changes in the past. The mineral content, particle concentration and chemical composition of modern dust in firn cores from the peripherycal dome (Talos Dome) and coastal area of East Antarctica (Ross Sea sector) were investigated. During analyses there was a considerable decrease in microparticle concentrations within a few hours of ice sample melting, accompanied by a systematic increase in the concentration of calcium ions (Ca 2+) in solution. Based on mineralogical phase analyses, which reveal the presence of anhydrous and hydrous calcium carbonates such as calcite (CaCO 3), monohydrocalcite (CaCO 3·H 2O) and ikaite (CaCO 3·6H 2O, hexahydrate calcium carbonate), the observed variations in concentrations are ascribed to the partial dissolution of the carbonate content of samples. Soluble carbonate compounds are thus primary aerosols included into the samples along with insoluble aluminosilicate minerals. We hypothesize hydrous carbonates may derive from the sea ice surface, where ikaite typically forms at the early stages of sea ice formation. Back trajectory calculations show that favourable events for air mass advection from the sea ice surface to Talos Dome are rare but likely to occur.
17. Variations in the drift of larval cod ( Gadus morhua L.) in the Baltic Sea : combining field observations and modelling
DEFF Research Database (Denmark)
Voss, R.; Hinrichsen, H.H.; St. John, Michael
1999-01-01
Coupled three-dimensional (3-D) physical oceanographic modelling and field sampling programmes were carried out in May 1988 and August 1991 to investigate the potential drift of larval cod (Gadus morhua L.) in the Bornholm Basin of the Baltic Sea. The goals were to predict the transport of cod...... larvae, thus aiding the identification of physical processes influencing larval retention/dispersal. Numerical simulations were performed using a 3-D eddy-resolving baroclinic model based on the Bryan-Cox-Semtner code adapted for the Baltic Sea. Within the Bornholm Basin, the model was initialized...... for the time periods considered. Larval drift was simulated either by incorporation of passive drifters, or as the initial horizontal distribution of larvae implemented into the model. Drift model simulations of larval transport agreed relatively well with field observations. The influence of variations...
18. Partial pressure (or fugacity) of carbon dioxide, salinity and other variables collected from underway - surface observations using Barometric pressure sensor, Carbon dioxide (CO2) gas analyzer and other instruments from the JAMES CLARK ROSS in the Arctic Ocean, Barents Sea and others from 2012-11-15 to 2013-08-16 (NODC Accession 0115256)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — NODC Accession 0115256 includes chemical, meteorological, physical and underway - surface data collected from JAMES CLARK ROSS in the Arctic Ocean, Barents Sea,...
19. Measuring currents, ice drift, and waves from space: the Sea surface KInematics Multiscale monitoring (SKIM) concept
Science.gov (United States)
Ardhuin, Fabrice; Aksenov, Yevgueny; Benetazzo, Alvise; Bertino, Laurent; Brandt, Peter; Caubet, Eric; Chapron, Bertrand; Collard, Fabrice; Cravatte, Sophie; Delouis, Jean-Marc; Dias, Frederic; Dibarboure, Gérald; Gaultier, Lucile; Johannessen, Johnny; Korosov, Anton; Manucharyan, Georgy; Menemenlis, Dimitris; Menendez, Melisa; Monnier, Goulven; Mouche, Alexis; Nouguier, Frédéric; Nurser, George; Rampal, Pierre; Reniers, Ad; Rodriguez, Ernesto; Stopa, Justin; Tison, Céline; Ubelmann, Clément; van Sebille, Erik; Xie, Jiping
2018-05-01
We propose a satellite mission that uses a near-nadir Ka-band Doppler radar to measure surface currents, ice drift and ocean waves at spatial scales of 40 km and more, with snapshots at least every day for latitudes 75 to 82°, and every few days for other latitudes. The use of incidence angles of 6 and 12° allows for measurement of the directional wave spectrum, which yields accurate corrections of the wave-induced bias in the current measurements. The instrument's design, an algorithm for current vector retrieval and the expected mission performance are presented here. The instrument proposed can reveal features of tropical ocean and marginal ice zone (MIZ) dynamics that are inaccessible to other measurement systems, and providing global monitoring of the ocean mesoscale that surpasses the capability of today's nadir altimeters. Measuring ocean wave properties has many applications, including examining wave-current interactions, air-sea fluxes, the transport and convergence of marine plastic debris and assessment of marine and coastal hazards.
20. Measuring currents, ice drift, and waves from space: the Sea surface KInematics Multiscale monitoring (SKIM concept
Directory of Open Access Journals (Sweden)
F. Ardhuin
2018-05-01
Full Text Available We propose a satellite mission that uses a near-nadir Ka-band Doppler radar to measure surface currents, ice drift and ocean waves at spatial scales of 40 km and more, with snapshots at least every day for latitudes 75 to 82°, and every few days for other latitudes. The use of incidence angles of 6 and 12° allows for measurement of the directional wave spectrum, which yields accurate corrections of the wave-induced bias in the current measurements. The instrument's design, an algorithm for current vector retrieval and the expected mission performance are presented here. The instrument proposed can reveal features of tropical ocean and marginal ice zone (MIZ dynamics that are inaccessible to other measurement systems, and providing global monitoring of the ocean mesoscale that surpasses the capability of today's nadir altimeters. Measuring ocean wave properties has many applications, including examining wave–current interactions, air–sea fluxes, the transport and convergence of marine plastic debris and assessment of marine and coastal hazards.
1. Observation of Drifting Icebergs and Sea Ice from Space by TerraSAR-X and TanDEM-X
Science.gov (United States)
Won, Joong-Sun
2017-04-01
Detection and monitoring drifting icebergs and sea ice is of interest across wide range of Arctic and Antarctic coastal studies such as security of navigation, climatic impact, geological impact, etc. It is not easy to discriminate drifting ices from stationary ones, and to measure their drifting speeds. There is a potential to use space-borne SAR for this purpose, but it is difficult to precisely measure because the drift velocity is usually very slow. In this study, we investigate two approaches for discriminating drifting ices on the sea from surrounding static ones and for measuring their range velocity. The first method is to utilize the quad-pol TerraSAR-X which adopts dual receive antenna (DRA), and the second one is to examine the potential use of TanDEM-X bistatic along-track interferometry (ATI). To utilize DRA mode quad-pol SAR as ATI, it is necessary to remove the phase difference of scattering centers between transmitted H- and V-pol signals. By assume that the individual scattering center of returned signal does not change for a few inter-pulse periods, it is possible to measure the Doppler frequency induced by motion through measuring slow-time (or azimuth time) Doppler phase derivative of co-pol or cross-pol pairs. Results applied to TerraSAR-X quad-pol data over the Cape Columbia in the Arctic Ocean are to be presented and discussed. It was successful to detect and measure drift sea ice that was flowing away from the antenna with a velocity of about 0.37 m/s (or 1.4 km/h) to 0.67 m/s (or 2.4 km/h) while neighboring ones were static. A more sophisticated approach would be a bistatic ATI which exploits a long along-track baseline for observation of slowly moving ground objects. TanDEM-X bistatic ATI pairs are examined, which were acquired at an Antarctic coast. The ATI interferograms show an innovative capability of TanDEM-X/TerraSAR-X constellation. An along-track baseline of a few hundred meters is superior to a few meter baseline of DRA mode ATI
2. Seasonal variation of air-sea CO2 fluxes in the Terra Nova Bay of the Ross Sea, Antarctica, based on year-round pCO2 observations
Science.gov (United States)
Zappa, C. J.; Rhee, T. S.; Kwon, Y. S.; Choi, T.; Yang, E. J.; Kim, J.
2017-12-01
The polar oceans are rapidly changing in response to climate variability. In particular, augmented inflow of glacial melt water and shrinking sea-ice extent impacts the polar coastal oceans, which may in turn shift the biogeochemistry into an unprecedented paradigm not experienced previously. Nonetheless, most research in the polar oceans is limited to the summer season. Here, we present the first direct observations of ocean and atmospheric pCO2 measured near the coast of Terra Nova Bay in the Ross Sea, Antarctica, ongoing since February, 2015 at Jang Bogo Station. The coastal area is covered by landfast sea-ice from spring to fall while continually exposed to the atmosphere during summer season only. The pCO2 in seawater swung from 120 matm in February to 425 matm in early October. Although sea-ice still covers the coastal area, pCO2 already started decreasing after reaching the peak in October. In November, the pCO2 suddenly dropped as much as 100 matm in a week. This decrease of pCO2 continued until late February when the sea-ice concentration was minimal. With growing sea ice, the pCO2 increased logarithmically reaching the atmospheric concentration in June/July, depending on the year, and continued to increase until October. Daily mean air-sea CO2 flux in the coastal area widely varied from -70 mmol m-2 d-1 to 20 mmol m-2 d-1. Based on these observations of pCO2 in Terra Nova Bay, the annual uptake of CO2 is 8 g C m-2, estimated using the fraction of sea-ice concentration estimated from AMSR2 microwave emission imagery. Extrapolating to all polynyas surrounding Antarctica, we expect the annual uptake of 8 Tg C in the atmosphere. This is comparable to the amount of CO2 degassed into the atmosphere south of the Antarctic Polar Front (62°S).
3. Ross og demokratiet
DEFF Research Database (Denmark)
Svensson, Palle
2006-01-01
En kritisk analyse af Alf Ross' teori om demokrati på grundlag af Roberty A. Dahl's begrebsapparat.......En kritisk analyse af Alf Ross' teori om demokrati på grundlag af Roberty A. Dahl's begrebsapparat....
4. Ross - for altid?
DEFF Research Database (Denmark)
Blume, Peter Erik
2011-01-01
Med baggrund i Jens Ewalds bog om Alf Ross omtaler artiklen en række de problemstillinger, som bogen behandler, samt vurderer den betydning, Ross har haft og måske fortsat har. Afslutningsvis betones den juridiske biografis betydning.......Med baggrund i Jens Ewalds bog om Alf Ross omtaler artiklen en række de problemstillinger, som bogen behandler, samt vurderer den betydning, Ross har haft og måske fortsat har. Afslutningsvis betones den juridiske biografis betydning....
5. Persistent organic pollutants (POPs) in the atmosphere of coastal areas of the Ross Sea, Antarctica: Indications for long-term downward trends.
Science.gov (United States)
Pozo, Karla; Martellini, Tania; Corsolini, Simonetta; Harner, Tom; Estellano, Victor; Kukučka, Petr; Mulder, Marie D; Lammel, Gerhard; Cincinelli, Alessandra
2017-07-01
Passive air samplers were used to evaluate long-term trends and spatial distribution of trace organic compounds in Antarctica. Duplicate PUF disk samplers were deployed at six automatic weather stations in the coastal area of the Ross sea (East Antarctica), between December 2010 and January 2011, during the XXVI Italian Scientific Research Expedition. Among the investigated persistent organic compounds, Hexachlorobenzene was the most abundant, with air concentrations ranging from 0.8 to 50 pg m -3 . In general, the following decreasing concentration order was found for the air samples analyzed: HCB > PeCB > PCBs > DDTs > HCHs. While HCB concentrations were in the same range as those reported in the atmosphere of other Antarctic sampling areas and did not show a decline, HCHs and DDTs levels were lower or similar to those determined one or two decades ago. In general, the very low concentrations reflected the pristine state of the East Antarctica air. Backward trajectories indicated the prevalence of air masses coming from the Antarctic continent. Local contamination and volatilization from ice were suggested as potential sources for the presence of persistent organic pollutants in the atmosphere. Copyright © 2017 Elsevier Ltd. All rights reserved.
6. Fractionation distribution and preliminary ecological risk assessment of As, Hg and Cd in ornithogenic sediments from the Ross Sea region, East Antarctica
Energy Technology Data Exchange (ETDEWEB)
Lou, Chuangneng [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Liu, Xiaodong, E-mail: [email protected] [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Nie, Yaguang [Institute of Polar Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 (China); Emslie, Steven D. [Department of Biology and Marine Biology, University of North Carolina Wilmington, 601S. College Road, Wilmington, NC 28403 (United States)
2015-12-15
To evaluate mobility of toxic elements and their potential ecological risk caused by seabird biovectors, the fractionation distributions of arsenic (As), mercury (Hg) and cadmium (Cd) were investigated in three ornithogenic sediment profiles from the Ross Sea region, East Antarctica. The results show residual As holds a dominant position, and Hg mainly derives from residual, organic matter-bound and humic acid-bound fractions, indicating weak mobility of As and Hg. However, exchangeable Cd occupies a considerable proportion in studied samples, suggesting Cd has strong mobility. The preliminary evaluation of Sediment Quality Guidelines (SGQs) shows adverse biological effects may occur occasionally for As and Cd, and rarely for Hg. Using Risk Assessment Code (RAC), the ecological risk is assessed at moderate, low and very high for As, Hg and Cd pollution, respectively. Organic matter derived from guano is the main factor controlling the mobility of Hg and Cd through adsorption and complexation. - Highlights: • Residual As holds a dominant position in ornithogenic sediments. • Hg mainly derives from residual, organic matter-bound and humic acid-bound fractions. • Exchangeable Cd occupies a considerable proportion in ornithogenic sediments. • TOC is the main factor controlling the mobility of Hg and Cd in studied sediments.
7. Rift-drift transition in the Dangerous Grounds, South China Sea
Science.gov (United States)
Peng, Xi; Shen, Chuanbo; Mei, Lianfu; Zhao, Zhigang; Xie, Xiaojun
2018-04-01
The South China Sea (SCS) has a long record of rifting before and after subsequent seafloor spreading, affecting the wide continent of the Dangerous Grounds, and its scissor-shape opening manner results in the rifting structures that vary along this margin. Some 2000 km of regional multichannel seismic data combined with borehole and dredge data are interpreted to analyze the multistage rifting process, structural architecture and dynamic evolution across the entire Dangerous Grounds. Key sequence boundaries above the Cenozoic basement are identified and classified into the breakup unconformity and the rift end unconformity, which consist of the rift-related unconformities. Reflector T70 in the east of the Dangerous Grounds represents the breakup unconformity, which is likely corresponding to the spreading of the East Subbasin. T60 formed on the top of carbonate platform is time equivalent to the spreading of the Southwest Subbasin, marking the breakup unconformity of the central Dangerous Grounds. The termination of the spreading of the SCS is manifested by the rift end unconformity of T50 in the southwest and the final rift occurring in the northwest of the Dangerous Grounds is postponed to the rift end unconformity of T40. On the basis of the stratigraphic and structural analysis, distinct segments in the structural architecture of the syn-rift units and the ages of rift-drift transition show obvious change from the proximal zone to the distal zone. Three domains, which are the Reed Bank-Palawan Rift domain, the Dangerous Grounds Central Detachment domain and Nam Con Son Exhumation domain, reflect the propagation of the margin rifting developed initially by grabens formed by high angle faults, then large half-grabens controlled by listric faults and detachments and finally rotated fault blocks in the hyper-extended upper crust associated with missing lower crust or exhumed mantle revealing a migration and stepwise rifting process in the south margin of the SCS.
8. Basic epidemiological data on metazoan parasites of notothenioid fish off James Ross Island (Prince Gustav Channel, Weddell Sea), Antarctica
Czech Academy of Sciences Publication Activity Database
Nezhybová, Veronika; Mašová, Š.
2015-01-01
Roč. 5, č. 1 (2015), s. 44-54 ISSN 1805-0689 R&D Projects: GA ČR(CZ) GBP505/12/G112 Institutional support: RVO:68081766 Keywords : Host * Notothenioid fish * Parasites * Prince Gustav Channel * Weddell Sea Subject RIV: EG - Zoology
9. Some Results on Sea Ice Rheology for the Seasonal Ice Zone, Obtained from the Deformation Field of Sea Ice Drift Pattern
Science.gov (United States)
Toyota, T.; Kimura, N.
2017-12-01
Sea ice rheology which relates sea ice stress to the large-scale deformation of the ice cover has been a big issue to numerical sea ice modelling. At present the treatment of internal stress within sea ice area is based mostly on the rheology formulated by Hibler (1979), where the whole sea ice area behaves like an isotropic and plastic matter under the ordinary stress with the yield curve given by an ellipse with an aspect ratio (e) of 2, irrespective of sea ice area and horizontal resolution of the model. However, this formulation was initially developed to reproduce the seasonal variation of the perennial ice in the Arctic Ocean. As for its applicability to the seasonal ice zones (SIZ), where various types of sea ice are present, it still needs validation from observational data. In this study, the validity of this rheology was examined for the Sea of Okhotsk ice, typical of the SIZ, based on the AMSR-derived ice drift pattern in comparison with the result obtained for the Beaufort Sea. To examine the dependence on a horizontal scale, the coastal radar data operated near the Hokkaido coast, Japan, were also used. Ice drift pattern was obtained by a maximum cross-correlation method with grid spacings of 37.5 km from the 89 GHz brightness temperature of AMSR-E for the entire Sea of Okhotsk and the Beaufort Sea and 1.3 km from the coastal radar for the near-shore Sea of Okhotsk. The validity of this rheology was investigated from a standpoint of work rate done by deformation field, following the theory of Rothrock (1975). In analysis, the relative rates of convergence were compared between theory and observation to check the shape of yield curve, and the strain ellipse at each grid cell was estimated to see the horizontal variation of deformation field. The result shows that the ellipse of e=1.7-2.0 as the yield curve represents the observed relative conversion rates well for all the ice areas. Since this result corresponds with the yield criterion by Tresca and
10. Observing Physical and Biological Drivers of pH and O2 in a Seasonal Ice Zone in the Ross Sea Using Profiling Float Data
Science.gov (United States)
Briggs, E.; Martz, T. R.; Talley, L. D.; Mazloff, M. R.
2015-12-01
Ice cover has strong influence over gas exchange, vertical stability, and biological production which are critical to understanding the Southern Ocean's central role in oceanic biogeochemical cycling and heat and carbon uptake under a changing climate. However the relative influence of physical versus biological processes in this hard-to-study region is poorly understood due to limited observations. Here we present new findings from a profiling float equipped with biogeochemical sensors in the seasonal ice zone of the Ross Sea capturing, for the first time, under-ice pH profile data over a two year timespan from 2014 to the present. The relative influence of physical (e.g. vertical mixing and air-sea gas exchange) and biological (e.g. production and respiration) drivers of pH and O2 within the mixed layer are explored during the phases of ice formation, ice cover, and ice melt over the two seasonal cycles. During the austral fall just prior to and during ice formation, O2 increases as expected due to surface-layer undersaturation and enhanced gas exchange. A small increase in pH is also observed during this phase, but without a biological signal in accompanying profiling float chlorophyll data, which goes against common reasoning from both a biological and physical standpoint. During the phase of ice cover, gas exchange is inhibited and a clear respiration signal is observed in pH and O2 data from which respiration rates are calculated. In the austral spring, ice melt gives rise to substantial ice edge phytoplankton blooms indicated by O2 supersaturation and corresponding increase in pH and large chlorophyll signal. The influence of the duration of ice cover and mixed layer depth on the magnitude of the ice edge blooms is explored between the two seasonal cycles.
11. Constraining the dynamic response of subcontinental lithospheric mantle to rifting using Re-Os model ages in the Western Ross Sea, Antarctica
Science.gov (United States)
Doherty, C.; Class, C.; Goldstein, S. L.; Shirey, S. B.; Martin, A. P.; Cooper, A. F.; Berg, J. H.; Gamble, J. A.
2012-12-01
In order to understand the dynamic response of the subcontinental lithospheric mantle (SCLM) to rifting, it is important to be able to distinguish the geochemical signatures of SCLM vs. asthenosphere. Recent work demonstrates that unradiogenic Os isotope ratios can indicate old depletion events in the convecting upper mantle (e.g. Rudnick & Walker, 2009), and allow us to make these distinctions. Thus, if SCLM can be traced across a rifted margin, its fate during rifting can be established. The Western Ross Sea provides favorable conditions to test the dynamic response of SCLM to rifting. Re-Os measurements from 8 locations extending from the rift shoulder to 200 km into the rift basin reveal 187Os/188Os ranging from 0.1056 at Foster Crater on the shoulder, to 0.1265 on Ross Island within the rift. While individual sample model ages vary widely throughout the margin, 'aluminochron' ages (Reisberg & Lorand, 1995) reveal a narrower range of lithospheric stabilization ages. Franklin Island and Sulfur Cones show a range of Re-depletion ages (603-1522 Ma and 436-1497 Ma) but aluminochrons yield Paleoproterozoic stabilization ages of 1680 Ma and 1789 Ma, respectively. These ages coincide with U-Pb zircon ages from Transantarctic Mountain (TAM) crustal rocks, in support of SCLM stabilization at the time of crust formation along the central TAM. The Paleoproterozoic stabilization age recorded at Franklin Island is especially significant, since it lies 200km off of the rift shoulder. The similar ages beneath the rift shoulder and within the rift suggests stretched SCLM reaches into the rift and thus precludes replacement by asthenospheric mantle. The persistence of thinned Paleoproterozoic SCLM into the rifted zone in WARS suggests that it represents a 'type I' margin of Huismans and Beaumont (2011), which is characterized by crustal breakup before loss of lithospheric mantle. The Archean Re-depletion age of 3.2 Ga observed on the rift shoulder suggests that cratonic
12. Geodynamic modelling of the rift-drift transition: Application to the Red Sea
Science.gov (United States)
Fierro, E.; Schettino, A.; Capitanio, F. A.; Ranalli, G.
2017-12-01
The onset of oceanic accretion after a rifting phase is generally accompanied by an initial fast pulse of spreading in the case of volcanic margins, such that the effective spreading rate exceeds the relative far-field velocity between the two plates for a short time interval. This pulse has been attributed to edge-driven convention (EDC), although our numerical modelling shows that the shear stress at the base of the lithosphere cannot exceed 1 MPa. In general, we have developed a 2D numerical model of the mantle instabilities during the rifting phase, in order to determine the geodynamic conditions at the rift-drift transition. The model was tested using Underworld II software, variable rheological parameters, and temperature and stress-dependent viscosity. Our results show an increase of strain rates at the top of the lithosphere with the lithosphere thickness as well as with the initial width of the margin up to 300 km. Beyond this value, the influence of the initial rift width can be neglected. An interesting outcome of the numerical model is the existence of an axial zone characterized by higher strain rates, which is flanked by two low-strain stripes. As a consequence, the model suggests the existence of an area of syn-rift compression within the rift valley. Regarding the post-rift phase, we propose that at the onset of a seafloor spreading, a phase of transient creep allows the release of the strain energy accumulated in the mantle lithosphere during the rifting phase, through anelastic relaxation. Then, the conjugated margins would be subject to post-rift contraction and eventually to tectonic inversion of the rift structures. To explore the tenability of this model, we introduce an anelastic component in the lithosphere rheology, assuming both the classical linear Kelvin-Voigt rheology and a non-linear Kelvin model. The non-linear model predicts viable relaxation times ( 1-2Myrs) to explain the post-rift tectonic inversion observed along the Arabian
13. Phylogeography and genetic structure of Hibiscus tiliaceus--speciation of a pantropical plant with sea-drifted seeds.
Science.gov (United States)
Takayama, Koji; Kajita, Tadashi; Murata, Jin; Tateishi, Yoichi
2006-09-01
Phylogenetic relationships and the spatial genetic structure of a pantropical plant with sea-drifted seeds, Hibiscus tiliaceus L., and its allied species were investigated. The combined distribution range of these species is over almost the entire littoral area of the tropics worldwide, which might result from the dispersal of their sea-drifted seeds and from recurrent speciation in local populations. A phylogenetic tree constructed using the nucleotide sequences of a c. 7500-bp portion of chloroplast DNA suggested the possibility that recurrent speciation from H. tiliaceus has given rise to all of its allied species. Three major sequence haplotypes of H. tiliaceus had wide and overlapping distributions throughout the Pacific, Atlantic and Indian Ocean regions. This distribution pattern was also confirmed by PCR-SSCP (polymerase chain reaction amplification with single-strand conformation polymorphism) and PCR-SSP (PCR amplification with sequence specific primers) analyses performed on more than 1100 samples from 65 populations worldwide. Statistical analysis using F(ST) and analysis of molecular variance did not show significant genetic differentiation among the H. tiliaceus populations in the three oceanic regions. The results reported here suggested substantial gene flow occurred between populations in the different oceanic regions due to sea-drifted seeds. A strong genetic difference between the Pacific and Atlantic populations of Hibiscus pernambucensis Arruda was observed, which indicates that gene flow in this species between the two regions has been prevented. The wide and dominant distribution of a haplotype shared by H. pernambucensis and H. tiliaceus in the Atlantic region suggests significant introgression between the two species in this region.
14. Poly-brominated diphenyl-ethers (PBDEs) and other persistent organic pollutants in blood of penguins from the Ross Sea (Antarctica)
Energy Technology Data Exchange (ETDEWEB)
Corsolini, S.; Ademollo, N.; Mariottini, M.; Focardi, S. [Universita degli Studi di Siena, Siena (Italy)
2004-09-15
Polychlorobiphenyls (PCBs), hexachlorobenzene (HCB), polybrominated diphenyl ethers (PBDEs) and dichlorodiphenyl-dichloro ethane (pp'-DDE) including its isomers and metabolites are known as POPs very well. POPs are particularly hazardous to wildlife not only because they are toxic but because they are persistent and distributed on global scale. Polybrominated diphenyl ethers (PBDEs) are a class of POPs used worldwide as flame retardants with an increasing trend in the market demand (67.4 ktons in 2001), but with some restrictions in their usage in Europe. PBDEs are hydrophobic, highly soluble in lipids, resistant to biodegradation and have similar behavior to polychlorinated biphenyls (PCBs) in aquatic and terrestrial ecosystems. Their bioaccumulation and biomagnification properties, as well their global increasing presence, have already been reported by many authors. PBDEs have been detected in remote Arctic regions10 that seem to be their final sink. PBDEs show acute toxicity and a prolonged exposure can affect the function of thyroid and cause neurodevelopmental disorders and estrogenic and hepatic effects. Furthermore, a synergic effect with dioxin-like compounds or other POPs cannot be excluded. The two aims of this study are: (1) to evaluate accumulation levels and patterns of PCBs, PBDEs and chlorinated pesticides in blood samples of the Adelie penguin, Pygoscelis adeliae, the Emperor penguin, Aptenodytes forsteri and the South Polar skua, Cataracta maccormicki from three sites in the Ross Sea (Antarctica); (2) to assess the suitability of blood for the detection of POP residues in supposedly low contaminated organisms that live in protected/ecologically sensitive areas.
15. Method to characterize directional changes in Arctic sea ice drift and associated deformation due to synoptic atmospheric variations using Lagrangian dispersion statistics
Directory of Open Access Journals (Sweden)
J. V. Lukovich
2017-07-01
Full Text Available A framework is developed to assess the directional changes in sea ice drift paths and associated deformation processes in response to atmospheric forcing. The framework is based on Lagrangian statistical analyses leveraging particle dispersion theory which tells us whether ice drift is in a subdiffusive, diffusive, ballistic, or superdiffusive dynamical regime using single-particle (absolute dispersion statistics. In terms of sea ice deformation, the framework uses two- and three-particle dispersion to characterize along- and across-shear transport as well as differential kinematic parameters. The approach is tested with GPS beacons deployed in triplets on sea ice in the southern Beaufort Sea at varying distances from the coastline in fall of 2009 with eight individual events characterized. One transition in particular follows the sea level pressure (SLP high on 8 October in 2009 while the sea ice drift was in a superdiffusive dynamic regime. In this case, the dispersion scaling exponent (which is a slope between single-particle absolute dispersion of sea ice drift and elapsed time changed from superdiffusive (α ∼ 3 to ballistic (α ∼ 2 as the SLP was rounding its maximum pressure value. Following this shift between regimes, there was a loss in synchronicity between sea ice drift and atmospheric motion patterns. While this is only one case study, the outcomes suggest similar studies be conducted on more buoy arrays to test momentum transfer linkages between storms and sea ice responses as a function of dispersion regime states using scaling exponents. The tools and framework developed in this study provide a unique characterization technique to evaluate these states with respect to sea ice processes in general. Application of these techniques can aid ice hazard assessments and weather forecasting in support of marine transportation and indigenous use of near-shore Arctic areas.
16. A method for assessing the physical recovery of Antarctic desert pavements following human-induced disturbances: a case study in the Ross Sea region of Antarctica.
Science.gov (United States)
O'Neill, Tanya A; Balks, Megan R; López-Martínez, Jerónimo; McWhirter, Judi L
2012-12-15
With increasing visitor numbers an understanding of the impacts of human activities in Antarctic terrestrial environments has become important. The objective of this study was to develop a means for assessing recovery of the ground surface desert pavement following physical disturbance. A set of 11 criteria were identified to assess desert pavement recovery. Assessed criteria were: embeddedness of surface clasts; impressions of removed clasts; degree of clast surface weathering; % overturned clasts; salt on underside of clasts; development of salt coatings; armouring per m(2); colour contrast; evidence of subsidence/melt out; accumulation of salt on cut surfaces; and evidence of patterned ground development. Recovery criteria were assigned a severity/extent rating on a scale from zero to four, zero being highly disturbed, and four being undisturbed. A relative % recovery for each criteria was calculated for each site by comparison with a nearby undisturbed control area, and an overall Mean Recovery Index (MRI) was assigned to each pavement surface. To test the method, 54 sites in the Ross Sea region of Antarctica were investigated including areas disturbed by: bulldozer scraping for road-fill, contouring for infrastructure, geotechnical investigations, and experimental treading trial sites. Disturbances had occurred at timescales ranging from one week to 50 years prior to assessment. The extent of desert pavement recovery at the sites investigated in this study was higher than anticipated. Fifty of the 54 sites investigated were in an intermediate, or higher, stage of desert pavement recovery, 30 sites were in an advanced stage of recovery, and four sites were indistinguishable from adjacent control sites (MRI = 100%). It was found that active surfaces, such as the gravel beach deposits at the Greenpeace World Park Base site at Cape Evans, the aeolian sand deposits at Bull Pass, and the alluvial fan deposits of the Loop Moraine field campsite, recovered relatively
17. Ross Ice Shelf, Antarctic Ice and Clouds
Science.gov (United States)
1991-01-01
In this view of Antarctic ice and clouds, (56.5S, 152.0W), the Ross Ice Shelf of Antarctica is almost totally clear, showing stress cracks in the ice surface caused by wind and tidal drift. Clouds on the eastern edge of the picture are associated with an Antarctic cyclone. Winds stirred up these storms have been known to reach hurricane force.
18. Stable Isotopic signatures of Adélie penguin remains provide long-term paleodietary records in Northern Victoria Land (Ross Sea, Antarctica)
Science.gov (United States)
Lorenzini, Sandra; Baroni, Carlo; Fallick, Anthony Edward; Baneschi, Ilaria; Salvatore, Maria Cristina; Zanchetta, Giovanni; Dallai, Luigi
2010-05-01
The stable isotopes geochemistry of carbon and nitrogen provides a powerful tools for investigating in animal dietary patterns and shifts during the past. The signature of C and N isotopes provide direct information about the diet of an individual and its dietary patterns, especially when the dietary sources consist of prey from different trophic levels (i.e. different C and N isotopic composition) (DeNiro and Epstein 1978, Minawaga and Wada 1984, Koch et al. 1994, Hobson 1995). By analyzing the isotopic composition of penguin remains, we present a new detailed Adélie penguin (Pygoscelis adeliae) paleodietary record for the area of Terra Nova Bay (Victoria Land, Ross Sea). Adélie penguins primarily feed on fish (mainly the silverfish Pleuragramma antarcticum) and krill (Euphausia superba, Euphausia cristallorophias) (Ainley 2002, Lorenzini et al. 2009) that belonging to two different trophic levels. Consequently, they are characterized by different isotopic signatures. Specifically, we analyzed 13C/12C and 15N/14N ratios of more than one thousand of modern and fossil Adélie penguin eggshell and guano samples collected from ornithogenic soils (penguin guano-formed) dated back to ≈7,200 years BP (Baroni and Orombelli 1994, Lambert et al. 2002, Baroni and Hall 2004, Hall et al. 2006). The expanded database of stable isotope values obtained from Adélie penguin remains define a detailed paleodietary record with an excellent temporal continuity over all the investigated time period. Our data indicate a significant dietary shift between fish and krill, with a gradual decrease from past to present time in the proportion of fish compared to krill in Adélie penguin diet. From 7200 yrs BP to 2000 yrs BP, δ13C and δ15N values indicate fish as the most eaten prey. The dietary contribution of lower-trophic prey in penguin diet started becoming evident not earlier than 2000 yrs BP, when the δ13C values reveal a mixed diet based on fish and krill consumption. Modern
19. Luminescence dating of paleolake deltas and glacial deposits in Garwood Valley, Antarctica: Implications for climate, Ross ice sheet dynamics, and paleolake duration
Science.gov (United States)
Levy, Joseph S.; Rittenour, Tammy M.; Fountain, Andrew G.; O'Connor, Jim E.
2017-01-01
The formation of perched deltas and other lacustrine deposits in the McMurdo Dry Valleys of Antarctica is widely considered to be evidence of valley-filling lakes dammed by the grounded Ross Sea ice sheet during the local Last Glacial Maximum, with lake drainage interpreted as a record of grounding line retreat. We used luminescence dating to determine the age of paleolake deltas and glacial tills in Garwood Valley, a coastal dry valley that opens to the Ross Sea. Luminescence ages are stratigraphically consistent with radiocarbon results from algal mats within the same delta deposits but suggest radiocarbon dates from lacustrine carbonates may overestimate deposit ages by thousands of years. Results suggest that late Holocene delta deposition into paleolake Howard in Garwood Valley persisted until ca. 3.5 ka. This is significantly younger than the date when grounded ice is thought to have retreated from the Ross Sea. Our evidence suggests that the local, stranded ice-cored till topography in Garwood Valley, rather than regional ice-sheet dynamics, may have controlled lake levels for some McMurdo Dry Valleys paleolakes. Age control from the supraglacial Ross Sea drift suggests grounding and up-valley advance of the Ross Sea ice sheet into Garwood valley during marine oxygen isotope stage (MIS) 4 (71–78 ka) and the local Last Glacial Maximum (9–10 ka). This work demonstrates the power of combining luminescence dating with existing radiocarbon data sets to improve understanding of the relationships among paleolake formation, glacial position, and stream discharge in response to climate change.
20. Ross og erkendelsesteorien
DEFF Research Database (Denmark)
Holtermann, Jakob von Holderstein
2006-01-01
Et argument for at den logiske positivismes notoriske problemer ikke - som almindeligt antaget - har gjort Alf Ross' retsfilosofi forældet. Mere konkret påvises det at Ross i virkeligheden passer bedre sammen med den empiriske erkendelsesteori der har rejst sig på den logiske positivismes ruiner....
1. The roles of MCDW and deep water iron supply in sustaining a recurrent phytoplankton bloom on central Pennell Bank (Ross Sea)
Science.gov (United States)
Kustka, Adam B.; Kohut, Josh T.; White, Angelicque E.; Lam, Phoebe J.; Milligan, Allen J.; Dinniman, Michael S.; Mack, Stefanie; Hunter, Elias; Hiscock, Michael R.; Smith, Walker O.; Measures, Chris I.
2015-11-01
During January-February 2011 standing stocks of phytoplankton (chl a) in the Pennell Bank region of the Ross Sea were variable over 10-100 km spatial scales. One area of elevated chl a on central Pennell Bank (CPB) appeared to be a recurrent mid-summer feature. The western flank (WF) of Pennell Bank had pronounced signatures of Modified Circumpolar Deep Water (MCDW). We evaluated the spatial extent of Fe limitation and net primary production and tested whether MCDW may provide elevated amounts of Fe to the CPB region, through a combination of in situ measurements, shipboard incubations and a horizontally resolved physical model. Regional fluxes of dissolved Fe from deep to surface waters were compared to calculated Fe demands. Low in situ variable to maximum fluorescence (Fv/Fm; 0.24-0.37) and surface water dissolved Fe concentrations (~0.12-0.21 nM) were suggestive of widespread limitation, corroborated by the consistent responses (Fv/Fm, growth, and nutrient removal ratios) of incubation treatments to Fe addition. MCDW from the WF region had lower dissolved Fe concentrations than that measured in CDW (Circumpolar Deep Water), which suggests on-shelf modification with Fe deplete surface waters and is consistent with the lack of stimulation due to incubation amendments with filtered MCDW. Model results and empirical data suggest MCDW from the WF region is further modified and mixed en route to the CPB region, leading to both the erosion of the canonical MCDW signature and an elevated dissolved Fe inventory of CPB region deep water. This suggests the addition of Fe possibly via diagenesis, as suggested by Marsay et al. (2014). Calculated deep water supply rates to the surface waters of CPB were ~0.18-0.43 m d-1, while calculated rates at the WF or northern Pennell Bank (NPB) regions were negative. The CPB populations exhibited ~4.5-fold higher net production rates compared to those in the WF and NPB regions and required 520-3200 nmol Fe m-2 d-1. The modeled vertical
2. Melt Origin Across a Rifted Continental Margin: A Case for Subduction-related Metasomatic Agents in the Lithospheric Source of Alkaline Basalt, Northwest Ross Sea, Antarctica
Science.gov (United States)
Panter, K. S.; Castillo, P.; Krans, S. R.; Deering, C. D.; McIntosh, W. C.; Valley, J. W.; Kitajima, K.; Kyle, P. R.; Hart, S. R.; Blusztajn, J.
2017-12-01
Alkaline magmatism within the West Antarctic rift system in the NW Ross Sea (NWRS) includes a chain of shield volcanoes extending 260 km along the coast, numerous seamounts located on the continental shelf and hundreds more within the oceanic Adare Basin. Dating and geochemistry confirm that the seamounts are Pliocene‒Pleistocene in age and petrogenetically akin to the mostly Miocene volcanism on the continent as well as to a much broader region of alkaline volcanism that altogether encompasses areas of West Antarctica, Zealandia and Australia. All of these regions were contiguous prior to Gondwana breakup at 100 Ma, suggesting that the magmatism is interrelated. Mafic alkaline magmas (> 6 wt.% MgO) erupted across the transition from continent to ocean in the NWRS show a remarkable systematic increase in Si-undersaturation, P2O5, Sr, Zr, Nb and light rare earth element (LREE) concentrations, LREE/HREE and Nb/Y ratios. Radiogenic isotopes also vary with Nd and Pb ratios increasing and Sr ratios decreasing ocean-ward. The variations are not explained by crustal contamination or by changes in degree of mantle partial melting but are likely a function of the thickness and age of mantle lithosphere. The isotopic signature of the most Si-undersaturated and incompatible element enriched basalts best represent the composition of the sub-lithospheric source with low 87Sr/86Sr (≤ 0.7030) and δ18Oolivine (≤ 5.0 ‰), high 143Nd/144Nd ( 0.5130) and 206Pb/204Pb (≥ 20) ratios. The isotopic endmember' is derived from recycled material and was transferred to the lithospheric mantle by small degree melts to form amphibole-rich metasomes. Later melting of the metasomes produced silica-undersaturated liquids that reacted with the surrounding peridotite. This reaction occurred to a greater extent as the melt traversed through thicker and older lithosphere continent-ward. Ancient or more recent ( 550‒100 Ma) subduction along the margin of Gondwana supplied the recycled
3. The role of pelagic-benthic coupling in structuring littoral benthic communities at Terra Nova Bay (Ross Sea and in the Straits of Magellan
Directory of Open Access Journals (Sweden)
Riccardo Cattaneo-Vietti
1999-12-01
Full Text Available In Antarctic and peri-Antarctic regions, benthic communities are persistent in time and show high biomass and large numbers of individuals, mainly consisting of suspension and deposit feeders. In fact, apart from recruitment, the major factor structuring these communities is the high flow of organic matter from the pelagic domain to the bottom, representing an important energy source for the benthic organisms. The aim of this paper is to review, compile and compare the data from earlier investigations in Terra Nova Bay (Ross Sea and the Straits of Magellan, in order to come to a more general conclusion about the role of the pelagic-benthic coupling in structuring littoral benthic communities in southern coastal areas. Few measurements of flux rates and the biochemical composition of the sinking particles occurring in Antarctic and peri-Antarctic shallow waters are available, but a compilation of our own data and others allows a comparison of these two systems. The different environmental conditions between Antarctica and the Straits of Magellan lead to differences in the origin of the particulate organic matter and in its biochemical composition, and consequently in the coupling between pelagic and benthic domains. At Terra Nova Bay the summer particulate matter shows a high labile fraction of a good food value: its flux has been evaluated at about 0.67 g m-2d-1. Conversely, the Straits of Magellan show multi-structured ecosystems where the quality and quantity of the organic matter flux towards the bottom change according to the local geomorphology and current dynamics. Moreover, the three-dimensional assemblages of suspension-feeders, so common in Antarctic shallow waters, seem to be absent in the Magellan area. In particular sponges, gorgonarians and bryozoans play a secondary role inside the Straits of Magellan, where polychaetes (60% and molluscs (9-10% are dominant on soft bottoms, and where they reach high values in density and biomass
4. Ontogenetic development of migration: Lagrangian drift trajectories suggest a new paradigm for sea turtles
DEFF Research Database (Denmark)
Hays, Graeme C.; Fossette, Sabrina; Katselidis, Kostas A.
2010-01-01
Long distance migration occurs in a wide variety of taxa including birds, insects, fishes, mammals and reptiles. Here, we provide evidence for a new paradigm for the determinants of migration destination. As adults, sea turtles show fidelity to their natal nesting areas and then at the end...... dispersion that would be experienced by hatchlings. Hence, the prevailing oceanography around nesting areas may be crucial to the selection of foraging sites used by adult sea turtles. This environmental forcing may allow the rapid evolution of new migration destinations if ocean currents alter with climate...
5. Red to Mediterranean Sea bioinvasion: natural drift through the Suez Canal, or anthropogenic transport?
Science.gov (United States)
Shefer, Sigal; Abelson, Avigdor; Mokady, Ofer; Geffen, Eli
2004-08-01
The biota of the eastern basin of the Mediterranean Sea has experienced dramatic changes in the last decades, in part as a result of the massive invasion of Red Sea species. The mechanism generally hypothesized for the 'Red-to-Med' invasion is that of natural dispersal through the Suez Canal. To date, however, this hypothesis has not been tested. This study examines the mode of invasion, using as a model the mussel Brachidontes pharaonis, an acclaimed 'Lessepsian migrant' that thrives along the eastern Mediterranean coast. Our findings reveal two distinct lineages of haplotypes, and five possible explanations are discussed for this observation. We show that the genetic exchange among the Mediterranean, Gulf of Suez and the northern Red Sea is sufficiently large to counteract the build up of sequential genetic structure. Nevertheless, these basins are rich in unique haplotypes of unknown origin. We propose that it is historic secondary contact, an ongoing anthropogenic transport or both processes, that participate in driving the population dynamics of B. pharaonis in the Mediterranean and northern Red Sea. Copyright 2004 Blackwell Publishing Ltd
6. Particulate matter and plankton dynamics in the Ross Sea Polynya of Terra Nova Bay during the Austral Summer 1997/98
Science.gov (United States)
Fonda Umani, S.; Accornero, A.; Budillon, G.; Capello, M.; Tucci, S.; Cabrini, M.; Del Negro, P.; Monti, M.; De Vittor, C.
2002-07-01
The structure and variability of the plankton community and the distribution and composition of suspended particulate matter, were investigated in the polynya of Terra Nova Bay (western Ross Sea) during the austral summer 1997/1998, with the ultimate objective of understanding the trophic control of carbon export from the upper water column. Sampling was conducted along a transect parallel to the shore, near the retreating ice edge at the beginning of December, closer to the coast at the beginning of February, and more offshore in late February. Hydrological casts and water sampling were performed at several depths to measure total particulate matter (TPM), particulate organic carbon (POC), biogenic silica (BSi), chlorophyll a (Chl a) and phaeopigment (Phaeo) concentrations. Subsamples were taken for counting autotrophic and heterotrophic pico- and nanoplankton and to assess the abundance and composition of microphyto- and microzooplankton. Statistical analysis identified two major groups of samples: the first included the most coastal surface samples of early December, characterized by the prevalence of autotrophic nanoplankton biomass; the second included all the remaining samples and was dominated by microphytoplankton. With regard to the relation of the plankton community composition to the biogenic suspended and sinking material, we identified the succession of three distinct periods. In early December Phaeocystis dominated the plankton assemblage in the well-mixed water column, while at the retreating ice-edge a bloom of small diatoms (ND) was developing in the lens of superficial diluted water. Concentrations of biogenic particulates were generally low and confined to the uppermost layer. The very low downward fluxes, the near absence of faecal pellets and the high Chl a/Phaeo ratios suggested that the herbivorous food web was not established yet or, at least, was not working efficiently. In early February the superficial pycnocline and the increased water
7. Bottom water production variability in the Ross Sea slope during the Late-Pleistocene-Holocene as revealed by benthic foraminifera and sediment geochemistry
Science.gov (United States)
Asioli, A.; Langone, L.; Tateo, F.; Giannossi, M. L.; Giglio, F.; Summa, V.; Piva, A.; Ridente, D.; Trincardi, F.
2009-04-01
The Antarctic area produces bottom waters that ventilate the vast majority of the deep basins in the rest of the world ocean. The rate of formation in the source area and the strength of these cold bottom waters affect their flow toward the equator and are key factors affecting the Global Thermohaline Circulation during modern and past climate conditions. We present the results of a multidisciplinary study carried out on a core collected in 2377m of water depth on the slope off the Drygalski Basin (Ross Sea), along the modern path of the bottom waters. The goal of this research is to detect a qualitative signal of possible changes in the rate of bottom water production during the Late Pleistocene-Holocene by integrating micropaleontological and geochemical proxies. The micropaleontological signal is represented by the quantitative and qualitative variations of the agglutinated benthic foraminifera assemblages, while the amount of TOC, nitrogen, δ13C, δ15N, biogenic silica, CaCO3 in the sediment, along with the bulk rock mineralogy, provide information on the paleoproductivity and allow reconstruction of changes in the paleocirculation. The chronology is supported by 14C AMS datings on organic matter. Although this study is still in progress, the results obtained allow the following observations: 1) the Holocene sequence includes a major turnover around 8-8.5 calib kyr BP, leading to reduced nutrient utilization, probably reflecting an increased nutrient supply induced by an enhanced Upper Circumpolar Deep Water upwelling; 2) within this general context, the total concentration of benthic foraminifera preserved in the fossil component records millennial scale cycles of variable amplitude after 8.5 calib kyr BP and to present time. This oscillatory trend is paralleled by other parameters, such as the magnetic susceptibility, the dry density, the sheet silicates and the δ15N; 3) minima in foraminifera concentration reflect relatively increased dissolution, weaker
8. Larval growth and drift pattern and the separation of herring spawning groups in the North Sea
DEFF Research Database (Denmark)
Munk, Peter; Christensen, Villy
1990-01-01
Data from two internationally co-ordinated survey programmes are used in an attempt to display the events in the early life that took place during the 'recovery period' of the North Sea herring stock, 1979-1986. During the period, an increasing importance of the spawning grounds off Buchan and off...... Yorkshire is evident from distributions of newly hatched herring larvae. The dramatic changes in relative importance of spawning grounds are traced in the data on both late larvae (6 months old) and juveniles (18 months old). The onset of extended spawning off Buchan and off Yorkshire was followed...... in the relative contributions from spawning grounds apparently influence the overall spatial distribution as well as size composition of larval and juvenile North Sea herring. The findings indicate that groups of larvae retain, to a large extent, separate distributions until metamorphosis, and point to larval...
9. Numerical modelling of edge-driven convection during rift-to-drift transition: application to the Red Sea
Science.gov (United States)
Fierro, Elisa; Capitanio, Fabio A.; Schettino, Antonio; Morena Salerno, V.
2017-04-01
We use numerical modeling to investigate the coupling of mantle instabilities and surface tectonics along lithospheric steps developing during rifting. We address whether edge driven convection (EDC) beneath rifted continental margins and shear flow during rift-drift transition can play a role in the observed post-rift compressive tectonic evolution of the divergent continental margins along the Red Sea. We run a series of 2D simulations to examine the relationship between the maximum compression and key geometrical parameters of the step beneath continental margins, such as the step height due to lithosphere thickness variation and the width of the margins, and test the effect of rheology varying temperature- and stress-dependent viscosity in the lithosphere and asthenosphere. The development of instabilities is initially illustrated as a function of these parameters, to show the controls on the lithosphere strain distribution and magnitude. We then address the transient evolution of the instabilities to characterize their duration. In an additional suite of models, we address the development of EDC during plate motions, thus accounting for the mantle shearing due to spreading. Our results show an increase of strain with the step height as well as with the margin width up to 200 km. After this value the influence of ridge margin can be neglected. Strain rates are, then, quantified for a range of laboratory-constrained constitutive laws for mantle and lithosphere forming minerals. These models propose a viable mechanism to explain the post-rift tectonic inversion observed along the Arabian continental margin and the episodic ultra-fast sea floor spreading in the central Red Sea, where the role of EDC has been invoked.
10. First High-Resolution Record of Late Quaternary Environmental Changes in the Amundsen Sea, West Antarctica, Revealed by Multi-proxy Analysis of Drift Sediments
Science.gov (United States)
Horrocks, J.; Ó Cofaigh, C.; Lloyd, J. M.; Hillenbrand, C. D.; Kuhn, G.; Smith, J.; Ehrmann, W. U.; Esper, O.
2015-12-01
The Amundsen Sea sector of the West Antarctic Ice Sheet (WAIS) is experiencing rapid mass loss and there is a pressing need to place the contemporary ice-sheet changes into a longer term context. The continental rise in this region is characterised by large sediment mounds that are shaped by westward flowing bottom currents and that resemble contouritic drifts existing offshore from the Antarctic Peninsula. Similar to the Antarctic Peninsula drifts, marine sediment cores from the poorly studied sediment mounds in the Amundsen Sea have the potential to provide reliable records of dynamical ice-sheet behaviour in West Antarctica and palaeoceanographic changes in the Southern Ocean during the Late Quaternary that can be reconstructed from their terrestrial, biogenic and authigenic components. Here we use multi-proxy data from three sediment cores recovered from two of the Amundsen Sea mounds to present the first high-resolution study of environmental changes on this part of the West Antarctic continental margin over the glacial-interglacial cycles of the Late Quaternary. Age constraints for the records are derived from biostratigraphy, AMS 14C dates and lithostratigraphy. We focus on the investigation of processes for drift formation, thereby using grain size and sortable silt data to reconstruct changes in bottom current speed and to identify episodes of current winnowing. Data on geochemical and mineralogical sediment composition and physical properties are used to infer both changes in terrigenous sediment supply in response to the advance and retreat of the WAIS across the Amundsen Sea shelf and changes in biological productivity that are mainly controlled by the duration of annual sea-ice coverage. We compare our data sets from the Amundsen Sea mounds to those from the well-studied Antarctic Peninsula drifts, thereby highlighting similarities and discrepancies in depositional processes and climatically-driven environmental changes.
11. Late Quaternary palaeoenvironmental reconstruction of sediment drift accumulation in the Malta Graben (central Mediterranean Sea)
Science.gov (United States)
Ferraro, Serena; Sulli, Attilio; Di Stefano, Enrico; Giaramita, Luigi; Incarbona, Alessandro; Graham Mortyn, P.; Sprovieri, Mario; Sprovieri, Rodolfo; Tonielli, Renato; Vallefuoco, Mattia; Zizzo, Elisabetta; Tranchida, Giorgio
2018-06-01
The Malta Graben is a deep tectonic depression in the Sicily Channel, bounded by NW-SE normal faults and filled by thick Pliocene-Quaternary deposits. A previous analysis of a giant piston core (LC09) from the Malta Graben had revealed a wide range of sedimentary features (carbonate turbidites, bioturbated mud and scours), although the chronostratigraphic constraint of the stacking pattern has remained elusive. After establishing a reliable chronological framework based on seven radiocarbon dates for a shorter core from the Malta Graben (ANSIC03-735), a down-core analysis of planktonic foraminifer and coccolith abundance, stable isotopes and sediment grain size was carried out. Since the last glacial maximum, palaeoenvironmental conditions (surface fertility and deep chlorophyll maximum during the last glacial and the Younger Dryas; warm and oligotrophic water masses, with a deep nutricline and intense winter mixing during the Holocene) as well as selected calcareous plankton taxa trends and peaks seem to be similar to those reported for other central and western Mediterranean sites, possibly in spite of a unique response of these areas to late Quaternary climatic fluctuations. Four distinct layers, each tens of centimetres thick, are barren of foraminifers but not of coccoliths. Morphobathymetric data as well as new high-resolution and high-penetration seismic profiles show that prolonged contouritic activity has persisted on the western side of the Malta Graben. It is thus likely that layers barren of foraminifers are due to the overflow of fine-grained (clayey) material beyond drift channel dikes.
12. Late Quaternary palaeoenvironmental reconstruction of sediment drift accumulation in the Malta Graben (central Mediterranean Sea)
Science.gov (United States)
Ferraro, Serena; Sulli, Attilio; Di Stefano, Enrico; Giaramita, Luigi; Incarbona, Alessandro; Graham Mortyn, P.; Sprovieri, Mario; Sprovieri, Rodolfo; Tonielli, Renato; Vallefuoco, Mattia; Zizzo, Elisabetta; Tranchida, Giorgio
2018-03-01
The Malta Graben is a deep tectonic depression in the Sicily Channel, bounded by NW-SE normal faults and filled by thick Pliocene-Quaternary deposits. A previous analysis of a giant piston core (LC09) from the Malta Graben had revealed a wide range of sedimentary features (carbonate turbidites, bioturbated mud and scours), although the chronostratigraphic constraint of the stacking pattern has remained elusive. After establishing a reliable chronological framework based on seven radiocarbon dates for a shorter core from the Malta Graben (ANSIC03-735), a down-core analysis of planktonic foraminifer and coccolith abundance, stable isotopes and sediment grain size was carried out. Since the last glacial maximum, palaeoenvironmental conditions (surface fertility and deep chlorophyll maximum during the last glacial and the Younger Dryas; warm and oligotrophic water masses, with a deep nutricline and intense winter mixing during the Holocene) as well as selected calcareous plankton taxa trends and peaks seem to be similar to those reported for other central and western Mediterranean sites, possibly in spite of a unique response of these areas to late Quaternary climatic fluctuations. Four distinct layers, each tens of centimetres thick, are barren of foraminifers but not of coccoliths. Morphobathymetric data as well as new high-resolution and high-penetration seismic profiles show that prolonged contouritic activity has persisted on the western side of the Malta Graben. It is thus likely that layers barren of foraminifers are due to the overflow of fine-grained (clayey) material beyond drift channel dikes.
13. Barents Sea field test of herder to thicken oil for in-situ burning in drift ice
International Nuclear Information System (INIS)
Buist, I.; Potter, S.; Sorstrom, S.E.
2009-01-01
Thick oil slicks are the key to effective in situ burning. Pack ice can enable in situ burning by keeping slicks thick. Oil spills in drift ice conditions can rapidly spread and become too thin to ignite. The application of chemical surface-active agents known as oil herders are commonly used in open waters to clean and contain oil slicks. Herders result in the formation of a monolayer of surfactants on the water surface and reduce the surface tension on the surrounding water considerably. When the surfactant monolayer reaches the edge of a thin oil slick, it changes the balance of interfacial forces acting on the slick edge and allows the interfacial tensions to contract the oil into thicker layers. This study examined the use of chemical herding agents to thicken oil spills in broken ice to allow them to be ignited and burned in situ. Two meso-scale field burn tests were conducted in May 2008 with crude oil slicks of about 0.1 and 0.7 m 3 in open drift ice off Svalbard in the Barents Sea. Prior to the field experiments, 2 series of small laboratory tests were conducted using Heidrun and Statfjord crudes to determine the ability of the U.S. Navy herding agent to contract slicks of the oil. In the first field experiment involving 102 litres of fresh Heidrun, the slick was unexpectedly carried by currents to a nearby ice edge where the oil was ignited and burned. Approximately 80 per cent of the oil was consumed in the burn. In the second field experiment involving 630 litres of fresh Heidrun, the free-drifting oil was allowed to spread for 15 minutes until it was much too thin to ignite. When the herding agent was applied, the slick contracted and thickened for about 10 minutes and was then ignited using a gelled gas igniter. A 9-minute long burn consumed about 90 per cent of the oil. 9 refs., 5 tabs., 34 figs.
14. Square-wave anodic-stripping voltammetric determination of Cd, Pb, and Cu in a hydrofluoric acid solution of siliceous spicules of marine sponges (from the Ligurian Sea, Italy, and the Ross Sea, Antarctica)
Energy Technology Data Exchange (ETDEWEB)
Truzzi, C.; Annibaldi, A.; Illuminati, S.; Bassotti, E.; Scarponi, G. [Polytechnic University of Marche, Ancona (Italy). Department of Marine Science
2008-09-15
Square-wave anodic-stripping voltammetry (SWASV) was set up and optimized for simultaneous determination of cadmium, lead, and copper in siliceous spicules of marine sponges, directly in the hydrofluoric acid solution ({proportional_to}0.55 mol L{sup -1} HF, pH {proportional_to}1.9). A thin mercury-film electrode (TMFE) plated on to an HF-resistant epoxy-impregnated graphite rotating-disc support was used. The optimum experimental conditions, evaluated also in terms of the signal-to-noise ratio, were as follows: deposition potential -1100 mV vs. Ag/AgCl, KCl 3 mol L{sup -1}, deposition time 3-10 min, electrode rotation 3000 rpm, SW scan from -1100 mV to +100 mV, SW pulse amplitude 25 mV, frequency 100 Hz, {delta}E{sub step} 8 mV, t{sub step} 100 ms, t{sub wait} 60 ms, t{sub delay} 2 ms, t{sub meas} 3 ms. Under these conditions the metal peak potentials were Cd -654{+-}1 mV, Pb -458 {+-} 1 mV, Cu -198{+-}1 mV. The electrochemical behaviour was reversible for Pb, quasi-reversible for Cd, and kinetically controlled (possibly following chemical reaction) for Cu. The linearity of the response with concentration was verified up to {proportional_to}4 {mu}g L{sup -1} for Cd and Pb and {proportional_to}20 {mu}g L{sup -1} for Cu. The detection limits were 5.8 ng L{sup -1}, 3.6 ng L{sup -1}, and 4.3 ng L{sup -1} for Cd, Pb, and Cu, respectively, with t{sub d}=5 min. The method was applied for determination of the metals in spicules of two specimens of marine sponges (Demosponges) from the Portofino natural reserve (Ligurian Sea, Italy, Petrosia ficiformis) and Terra Nova Bay (Ross Sea, Antarctica, Sphaerotylus antarcticus). The metal contents varied from tens of ng g{sup -1} to {proportional_to}1 {mu}g g{sup -1}, depending on the metal considered and with significant differences between the two sponge species. (orig.)
15. Relative influences of the metocean forcings on the drifting ice pack and estimation of internal ice stress gradients in the Labrador Sea
Science.gov (United States)
Turnbull, I. D.; Torbati, R. Z.; Taylor, R. S.
2017-07-01
Understanding the relative influences of the metocean forcings on the drift of sea ice floes is a crucial component to the overall characterization of an ice environment and to developing an understanding of the factors controlling the ice dynamics. In addition, estimating the magnitude of the internal stress gradients on drifting sea ice floes generated by surrounding ice cover is important for modeling operations, informing the design of offshore structures and vessels in ice environments, and for the proper calibration of Discrete Element Models (DEM) of fields of drifting ice floes. In the spring of 2015 and 2016, four sea ice floes offshore Makkovik, Labrador were tagged with satellite-linked ice tracking buoys along with one satellite-linked weather station on each floe to transmit wind speed and direction. Twenty satellite-linked Lagrangian surface ocean current tracking buoys were also deployed in the open water adjacent to the targeted ice floes. In this paper, the dynamics of the four ice floes are explored in terms of the relative proportions which were forced by the wind, current, sea surface topography, Coriolis, and internal stress gradients. The internal ice stress gradients are calculated as residuals between the observed accelerations of the floes as measured by the tracking buoys and the sums of the other metocean forcings. Results show that internal ice stress gradients accounted for up to 50% of the observed forcing on the floes, and may have reached up to around 0.19 kPa.
16. The Rossing file
International Nuclear Information System (INIS)
Roberts, A.
1980-01-01
The subject is discussed under the headings: the issues; Rio Tinto-Zinc; Namibia; the United Nations Decree No. 1; enter RTZ; signing the contracts; Namibia's response -SWAPO; the Rossing Mine; workers' voice. It is argued that the uranium mining operations are illegal. The wages, working conditions and living standards of the workers are criticized. (U.K.)
17. Rossing reaps training benefits
Energy Technology Data Exchange (ETDEWEB)
1982-06-17
A training program for unskilled operators at the Rossing Uranium Mine provides on avenue for a number of Namibians to become skilled workers without doing an apprenticeship and despite a lack of basic education. The Patterson plan has worked well so far for the purpose. A cadet scheme for leadership and trust foundation for scholarship have also been implemented.
18. Rossing uranium 1979
International Nuclear Information System (INIS)
Anon.
1979-01-01
This report describes the activities and organization of the Rossing uranium mine in South West Africa. The development of the mine during the last six years is described as well as the geology of the uranium deposits and aspects of the mining operations. The manpower structure and training possibilities for personnel are described
19. Rossing reaps training benefits
International Nuclear Information System (INIS)
Anon.
1982-01-01
A training program for unskilled operators at the Rossing Uranium Mine provides on avenue for a number of Namibians to become skilled workers without doing an apprenticeship and despite a lack of basic education. The Patterson plan has worked well so far for the purpose. A cadet scheme for leadership and trust foundation for scholarship have also been implemented
20. Upper ocean currents and sea surface temperatures (SST) from Satellite-tracked drifting buoys (drifters) as part of the Global Drifter Program for Hawaii region 1980/02/01 - 2009/03/31 (NODC Accession 0063296)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Satellite-tracked drifting buoys ("drifters") collect measurements of upper ocean currents and sea surface temperatures (SST) around the world as part of the Global...
1. Water temperature, ocean currents, and others in Ross Sea from 1998-02-12 to 2011-11-12 (NCEI Accession 0164025)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — This data set consists of physical parameters of sea water (temperature, salinity, current speed and direction) measured at specific depths on a mooring in the Terra...
2. Rifting-to-drifting transition of the South China Sea: Moho reflection characteristics in continental-ocean transition zone
Science.gov (United States)
Wen, Y.; Li, C.
2017-12-01
Dispute remains on the process of continental rifting to subsequent seafloor spreading in the South China Sea (SCS). Several crust-scale multi-channel seismic reflection profiles acquired in the continent-ocean transition zone (COT) of the SCS provide a detailed overview of Moho and deep crustal reflectors and give key information on rifting-to-drifting transition of the area. Moho has strong but discontinuous seismic reflection in COT. These discontinuities are mainly located in the landward side of continent-ocean boundary (COB), and may own to upwelling of lower crustal materials during initial continental extension, leading to numerous volcanic edifices and volcanic ridges. The continental crust in COT shows discontinuous Moho reflections at 11-8.5 s in two-way travel time (twtt), and thins from 18-20.5 km under the uppermost slope to 6-7 km under the lower slope, assuming an average crustal velocity of 6.0 km/s. The oceanic crust has Moho reflections of moderate to high continuity mostly at 1.8-2.2 s twtt below the top of the igneous basement, which means that the crustal thickness excluding sediment layer in COT is 5.4-6.6 km. Subhorizontal Moho reflections are often abruptly interrupted by large seaward dipping normal faults in southern COT but are more continuous compared with the fluctuant and very discontinuous Moho reflections in northern COT. The thickness of thinned continental crust (4.2-4.8 km) is smaller than that of oceanic crust (5.4-6.0 km) near southern COB, indicating that the continental crust has experienced a long period of rifting before seafloor spreading started. The smaller width of northern COT (0-40 km) than in southern COT (0-60 km), and thinner continental crust in southern COT, all indicate that the continental margin rifting and extension was asymmetric. The COT width in the SCS is narrower than that found in other magma-poor continental margins, indicating a swift transition from the final stage of rifting to the inception of
3. Gene flow and population subdivision in a pantropical plant with sea-drifted seeds Hibiscus tiliaceus and its allied species: evidence from microsatellite analyses.
Science.gov (United States)
Takayama, Koji; Tateishi, Yoichi; Murata, Jin; Kajita, Tadashi
2008-06-01
The genetic differentiation and structure of Hibiscus tiliaceus, a pantropical plant with sea-drifted seeds, and four allied species were studied using six microsatellite markers. A low level of genetic differentiation was observed among H. tiliaceus populations in the Pacific and Indian Ocean regions, similar to the results of a previous chloroplast DNA (cpDNA) study. Frequent gene flow by long-distance seed dispersal is responsible for species integration of H. tiliaceus in the wide distribution range. On the other hand, highly differentiated populations of H. tiliaceus were detected in West Africa, as well as of Hibiscus pernambucensis in southern Brazil. In the former populations, the African continent may be a geographical barrier that prevents gene flow by sea-drifted seeds. In the latter populations, although there are no known land barriers, the bifurcating South Equatorial Current at the north-eastern horn of Brazil can be a potential barrier to gene flow and may promote the genetic differentiation of these populations. Our results also suggest clear species segregation between H. tiliaceus and H. pernambucensis, which confirms the introgression scenario between these two species that was suggested by a previous cpDNA study. Our results also provide good evidence for recent transatlantic long-distance seed dispersal by sea current. Despite the distinct geographical structure observed in the cpDNA haplotypes, a low level of genetic differentiation was found between Pacific and Atlantic populations of H. pernambucensis, which could be caused by transisthmian gene flow.
4. Bandura, Ross, and Ross: Observational Learning and the Bobo Doll
Science.gov (United States)
Artino, Anthony R., Jr.
2007-01-01
Since the publication of their seminal article entitled, "Transmission of Aggression Through Imitation of Aggressive Models" (Bandura, Ross, & Ross, 1961), the work of Albert Bandura and his co-authors has had an immeasurable impact on the field of psychology, in general, and educational psychology, more specifically. The purpose of this report is…
5. Uranium extraction at Rossing
International Nuclear Information System (INIS)
Kesler, S.B.; Fahrbach, D.O.E.
1982-01-01
Rossing Uranium Ltd. operates a large open pit uranium mine and extraction plant at a remote site in the Namib desert. Production started at the plant in 1978. A ferric leach process was introduced later, and the new leach plant began commissioning in October 1981. The process has proved to be reliable and easily controlled. Ferric iron is supplied through recovery from the acid plant calcine, and levels can be maintained above the design levels. Leach extractions were increased more than expected when this process was adopted, and the throughput has been considerably reduced, allowing cost savings in mining and milling
6. Rossing set for great future
International Nuclear Information System (INIS)
Anon.
1978-01-01
Rio Tinto's Rossing open pit operation - the world's largest uranium mine - has had difficult birth pangs. The teething troubles which beset the mine are examined, together with the mining and extraction methods employed. Rossing's enlightened ideas on the labour question are also covered
7. Observation of hydro-acoustic signal from the Balleny Islands, Ross Sea, Antarctic: Seasonal ice activities and earthquakes from Pacific-Antarctic ridge
Science.gov (United States)
Hong, J. K.; Kang, S. G.; Dziak, R. P.; Park, Y.; Lau, T. K. A.; Haxel, J.; Matsumoto, H.
2017-12-01
From January 2015 to March 2016, five hydrophone moorings were deployed near the Balleny Islands to obtain the long-term hydroacoustic record as a collaborative effort between the NOAA/Pacific Marine Environmental Laboratory and the Korea Polar Research Institute. The goal of this hydro-acoustic project is to understand seasonal sea-ice activities and identify potential underwater volcanic sources within the Balleny seamounts. All five of the hydrophone moorings were recovered in March 2016, however only three of them recorded 14 months of continuous, broadband (1 kHz sample rate) hydro-acoustic data successfully. In spite of coordinating problem by partial recovery, recorded data contain valuable information for seasonal sea-ice activities and earthquakes from Pacific-Antarctic Ridge. We analyzed events from ice-quakes and earthquakes statistically. The number of ice-quakes is maximum in the austral summer while minimum in the austral winter which shows a clear seasonal pattern consistent with freeze-thaw cycles. Comparing with global earthquakes catalogue, number of earthquake events are correlated well with the catalogue. Because the austral winter is more calm by ice-quakes, however, we can detect more earthquakes in this season.
8. Combined effects of hydrographic structure and iron and copper availability on the phytoplankton growth in Terra Nova Bay Polynya (Ross Sea, Antarctica)
Science.gov (United States)
Rivaro, Paola; Luisa Abelmoschi, Maria; Grotti, Marco; Ianni, Carmela; Magi, Emanuele; Margiotta, Francesca; Massolo, Serena; Saggiomo, Vincenzo
2012-04-01
Surface water (CLIMA) Project of the Programma Nazionale di Ricerca in Antartide activities. Dissolved oxygen, nutrients, phytoplankton pigments and concentration and complexation of dissolved trace metals were determined. Experimental data were elaborated by Principal Component Analysis (PCA). As a result of solar heating and freshwater inputs from melting sea-ice, the water column was strongly stratified with an Upper Mixed Layer 4-16 m deep. The integrated Chl a in the layer 0-100 m ranged from 60 mg m-2 to 235 mg m-2, with a mean value of 138 mg m-2. The pigment analysis showed that diatoms dominated the phytoplankton assemblage. Major nutrients were generally high, with the lowest concentration at the surface and they were never fully depleted. The Si:N drawdown ratio was close to the expected value of 1 for Fe-replete diatoms. We evaluated both the total and the labile dissolved fraction of Fe and Cu. The labile fraction was operationally defined by employing the chelating resin Chelex-100, which retains free and loosely bound trace metal species. The total dissolved Fe ranged from 0.48 to 3.02 nM, while the total dissolved Cu from 3.68 to 6.84 nM. The dissolved labile Fe ranged from below the detection limit (0.15 nM) to 1.22 nM, and the dissolved labile Cu from 0.31 to 1.59 nM, respectively. The labile fractions measured at 20 m were significantly lower than values in 40-100 m samples. As two stations were re-sampled 5 days later, we evaluated the short-term variability of the physical and biogeochemical properties. In particular, in a re-sampled station at 20 m, the total dissolved Fe increased and the total dissolved Cu decreased, while their labile fraction was relatively steady. As a result of the increase in total Fe, the percentage of the labile Fe decreased. An increase of the Si:N, Si:P and Si:FUCO ratios was measured also in the re-sampled station. On this basis, we speculated that a switch from a Fe-replete to a Fe-deplete condition was occurring.
9. Regional Changes in the Sea Ice Cover and Ice Production in the Antarctic
Science.gov (United States)
Comiso, Josefino C.
2011-01-01
Coastal polynyas around the Antarctic continent have been regarded as sea ice factories because of high ice production rates in these regions. The observation of a positive trend in the extent of Antarctic sea ice during the satellite era has been intriguing in light of the observed rapid decline of the ice extent in the Arctic. The results of analysis of the time series of passive microwave data indicate large regional variability with the trends being strongly positive in the Ross Sea, strongly negative in the Bellingshausen/Amundsen Seas and close to zero in the other regions. The atmospheric circulation in the Antarctic is controlled mainly by the Southern Annular Mode (SAM) and the marginal ice zone around the continent shows an alternating pattern of advance and retreat suggesting the presence of a propagating wave (called Antarctic Circumpolar Wave) around the circumpolar region. The results of analysis of the passive microwave data suggest that the positive trend in the Antarctic sea ice cover could be caused primarily by enhanced ice production in the Ross Sea that may be associated with more persistent and larger coastal polynyas in the region. Over the Ross Sea shelf, analysis of sea ice drift data from 1992 to 2008 yields a positive rate-of-increase in the net ice export of about 30,000 km2 per year. For a characteristic ice thickness of 0.6 m, this yields a volume transport of about 20 km3/year, which is almost identical, within error bars, to our estimate of the trend in ice production. In addition to the possibility of changes in SAM, modeling studies have also indicated that the ozone hole may have a role in that it causes the deepening of the lows in the western Antarctic region thereby causing strong winds to occur offthe Ross-ice shelf.
10. MR diagnostics after Ross procedure
International Nuclear Information System (INIS)
Steffens, J.C.; Link, J.; Harringer, W.; Haverich, A.; Heller, M.
1996-01-01
Purpose: To determine the ability of MRI to diagnose morphological and functional changes in patients after Ross procedure. Material and methods: During one year, 5 patients after Ross procedure were studied by MRI. T 1 -weighted spin-echo sequences in different orientations as well as cine sequences and a VENC-sequence were used. Results: In all patients the morphology including the postoperative changes could be visualised by MRI. The cine sequences provided functional information on valvular and ventricular function. VENC-MR yielded an exact quantification of the regurgitant fraction. Conclusion: MRI is capable of providing all important diagnostic information in patients after Ross procedure such as valvular and ventricular function and valvular and outflow tract morphology in a single examination. (orig.) [de
11. Estimation of annual heat flux balance at the sea surface from sst (NOAA-satellite and ships drift data off southeast Brazil
Directory of Open Access Journals (Sweden)
Yoshimine Ikeda
1985-01-01
Full Text Available The objective of this work is to study the possibility of estimating the heat flux balance at the sea surface from GOSSTCOMP (Global Ocean Sea Surface Temperature Computation developed by NOAA/NESS, USA, and sea surface current data based from ships drift information obtained from Pilot Charts, published by the Diretoria de Hidrografia e Navegação (DHN, Brazilian Navy. The annual mean value of the heat flux balance at the sea surface off southeast Brazil for 1977, is estimated from data on the balance between the heat transported by the currents and that transported by eddy diffusion for each volume defined as 2º x 2º (Lat. x Long. square with a constant depth equivalent to an oceanic mixed layer, 100 m thick. Results show several oceanic areas where there are net flows of heat from atmosphere towards the sea surface. In front of Rio de Janeiro the heat flow was downward and up to 70 ly day-1 and is probably related to the upwellirug phenomenon normally occurring in that area. Another coastal area between Lat. 25ºS to 28ºS indicated an downward flow up to 50 ly day-1; and for an area south of Lat. 27ºS, Long. 040ºW - 048ºW an downward flow up to 200 ly day-1, where the transfer was probably due to the cold water of a nortward flux from the Falkland (Malvinas Current. Results also show several oceanic areas where net flows of heat (of about -100 ly day-1 were toward the atmosphere. In the oceanic areas Lat. 19ºS - 23ºS and Lat. 24ºS - 30ºS, the flows were probably due to the warm water of a southward flux of the Brazil Current. The resulting fluxes from the warm waters of the Brazil Current when compared with those from warm waters of the Gulf Stream and Kuroshio, indicate that the Gulf Stream carries about 3.3 times and the Kuroshio 1.7 times more heat than the Brazil Current. These values agree with those of data available on the heat fluxes of the above mentioned Currents calculated by different methods (Budyko, 1974.
12. Pontic shad (Alosa immaculata migrating upstream the Danube river and larval drift downstream to the Black Sea in 2016
Directory of Open Access Journals (Sweden)
NĂSTASE Aurel
2018-05-01
Full Text Available The genus Alosa is present only in the northern hemisphere of the earth with four species living in North America and others five in Europe, from which Pontic shad (Alosa immaculata is subject of present study. Migration of shad depends of the environmental drivers such as increasing spring water temperature and river flooding. In 2016, both factors favoured an earlier start of shad migration in February with peak of spawning run in April, and ended in mid of May. Afterwards the size of catches and market demands no longer motivated fishermen to fish and sell Pontic shads. The 2016 catch of 386 t fitted in the multiannual 10-11 years cyclical catches. Reproduction success was estimated by Larval Abundance Index (LAI standardized as Catch per Unit Effort (CPUE by number of larvae per 100 m3 filtered water volume. Relative abundance of drifting larvae in 2016 compared with other 6 previously years showed that average LAI varied widely (2-1,252 larvae per 100 m3 with an average of 84 larvae/100 m3 which was ranked in regular reproductive success.
13. Stokes drift
Science.gov (United States)
van den Bremer, T. S.; Breivik, Ø.
2017-12-01
14. Ross Ice Shelf airstream driven by polar vortex cyclone
Science.gov (United States)
Schultz, Colin
2012-07-01
The powerful air and ocean currents that flow in and above the Southern Ocean, circling in the Southern Hemisphere's high latitudes, form a barrier to mixing between Antarctica and the rest of the planet. Particularly during the austral winter, strong westerly winds isolate the Antarctic continent from heat, energy, and mass exchange, bolstering the scale of the annual polar ozone depletion and driving the continent's record-breaking low temperatures. Pushing through this wall of high winds, the Ross Ice Shelf airstream (RAS) is responsible for a sizable amount of mass and energy exchange from the Antarctic inland areas to lower latitudes. Sitting due south of New Zealand, the roughly 470,000-square-kilometer Ross Ice Shelf is the continent's largest ice shelf and a hub of activity for Antarctic research. A highly variable lower atmospheric air current, RAS draws air from the inland Antarctic Plateau over the Ross Ice Shelf and past the Ross Sea. Drawing on modeled wind patterns for 2001-2005, Seefeldt and Cassano identify the primary drivers of RAS.
15. Reducing Pesticide Drift
Science.gov (United States)
Provides information about pesticide spray drift, including problems associated with drift, managing risks from drift and the voluntary Drift Reduction Technology program that seeks to reduce spray drift through improved spray equipment design.
16. Drift chamber
International Nuclear Information System (INIS)
Inagaki, Yosuke
1977-01-01
Drift chamber is becoming an important detector in high energy physics as a precision and fast position detector because of its high spatial resolution and count-rate. The basic principle is that it utilizes the drift at constant speed of electrons ionized along the tracks of charged particles towards the anode wire in the nearly uniform electric field. The method of measuring drift time includes the analog and digital ones. This report describes about the construction of and the application of electric field to the drift chamber, mathematical analysis on the electric field and equipotential curve, derivation of spatial resolution and the factor for its determination, and selection of gas to be used. The performance test of the chamber was carried out using a small test chamber, the collimated β source of Sr-90, and 500 MeV/C electron beam from the 1.3 GeV electron synchrotron in the Institute of Nuclear Study, University of Tokyo. Most chambers to date adopted one dimensional read-out, but it is very advantageous if the two dimensional read-out is feasible with one chamber when the resolution in that direction is low. The typical methods of delay line and charge division for two dimensional read-out are described. The development of digital read-out system is underway, which can process the signal of a large scale drift chamber at high speed. (Wakatsuki, Y.)
17. Surface drift prediction in the Adriatic Sea using hyper-ensemble statistics on atmospheric, ocean and wave models: Uncertainties and probability distribution areas
Science.gov (United States)
Rixen, M.; Ferreira-Coelho, E.; Signell, R.
2008-01-01
Despite numerous and regular improvements in underlying models, surface drift prediction in the ocean remains a challenging task because of our yet limited understanding of all processes involved. Hence, deterministic approaches to the problem are often limited by empirical assumptions on underlying physics. Multi-model hyper-ensemble forecasts, which exploit the power of an optimal local combination of available information including ocean, atmospheric and wave models, may show superior forecasting skills when compared to individual models because they allow for local correction and/or bias removal. In this work, we explore in greater detail the potential and limitations of the hyper-ensemble method in the Adriatic Sea, using a comprehensive surface drifter database. The performance of the hyper-ensembles and the individual models are discussed by analyzing associated uncertainties and probability distribution maps. Results suggest that the stochastic method may reduce position errors significantly for 12 to 72??h forecasts and hence compete with pure deterministic approaches. ?? 2007 NATO Undersea Research Centre (NURC).
18. Operation of a Hovercraft Scientific Platform Over Sea Ice in the Arctic Ocean Transpolar Drift (81 - 85N): The FRAM-2012 Experience
Science.gov (United States)
Hall, J. K.; Kristoffersen, Y.
2013-12-01
We have tested the feasibility of hovercraft travel through predominantly first year ice of the Transpolar Drift between 81°N - 85°N north of Svalbard. With 2-9 ridges per kilometer, our hovercraft (Griffon TD2000 Mark II), with an effective hover height of about 0.5 m, had to travel a distance 1.3 times the great circle distance between the point of origin and the final destination. Instantaneous speeds were mostly 5-7 knots. Two weeks later icebreaker Oden completed the same transit under conditions with no significant pressure in the ice at a speed mostly 1 knot higher than the hovercraft and travelled 1.2 times the great circle distance. The hovercraft spent 25 days monitoring micro-earthquake activity of the Arctic Mid-Ocean Ridge at a section of the spreading center where no seismicity has been recorded by the global seismograph network. More than ten small earthquake events per day were recorded. Visibility appears to be the most critical factor to hovercraft travel in polar pack ice. Improved control of hovercraft motion would substantially increase the potential usefulness of hovercraft in the sea ice environment. University of Bergen graduate student Gaute Hope emplacing one of the hydrophones in the triangular array used to locate small earthquakes over the Gakkel Ridge rift valley around 85N during FRAM-2012. The research hovercraft R/H SABVABAA is in the background.
19. Influence of Meteorological Regimes on Cloud Microphysics Over Ross Island, Antarctica
Science.gov (United States)
Glennon, C.; Wang, S. H.; Scott, R. C.; Bromwich, D. H.; Lubin, D.
2017-12-01
The Antarctic provides a sharp contrast in cloud microphysics from the high Arctic, due to orographic lifting and resulting strong vertical motions induced by mountain ranges and other varying terrain on several spatial scales. The Atmospheric Radiation Measurement (ARM) West Antarctic Radiation Experiment (AWARE) deployed advanced cloud remote sensing equipment to Ross Island, Antarctica, from December 2015 until January 2016. This equipment included scanning and zenith radars operating in the Ka and X bands, a high spectral resolution lidar (HSRL), and a polarized micropulse lidar (MPL). A major AWARE objective is to provide state-of-the-art data for improving cloud microphysical parameterizations in climate models. To further this objective we have organized and classified the local Ross Island meteorology into distinct regimes using k-means clustering on ERA-Interim reanalysis data. We identify synoptic categories producing unique regimes of cloud cover and cloud microphysical properties over Ross Island. Each day of observations can then be associated with a specific meteorological regime, thus assisting modelers with identifying case studies. High-resolution (1 km) weather forecasts from the Antarctic Mesoscale Prediction System (AMPS) are sorted into these categories. AMPS-simulated anomalies of cloud fraction, near-surface air temperature, and vertical velocity at 500-mb are composited and compared with ground-based radar and lidar-derived cloud properties to identify mesoscale meteorological processes driving Antarctic cloud formation. Synoptic lows over the Ross and Amundsen Seas drive anomalously warm conditions at Ross Island by injecting marine air masses inland over the West Antarctic Ice Sheet (WAIS). This results in ice and mixed-phase orographic cloud systems arriving at Ross Island from the south to southeast along the Transantarctic Mountains. In contrast, blocking over the Amundsen Sea region brings classical liquid-dominated mixed-phase and
20. Short-term changes in particulate fluxes measured by drifting sediment traps during end summer oligotrophic regime in the NW Mediterranean Sea
Directory of Open Access Journals (Sweden)
J. C. Marty
2009-05-01
Full Text Available Short-term changes in the flux of particulate matter were determined in the central north western Mediterranean Sea (near DYFAMED site using drifting sediment traps at 200 m depth in the course of the DYNAPROC 2 cruise (14 September–17 October 2004. In this period of marked water column stratification, POC fluxes varied by an order of magnitude, in the range of 0.03–0.29 mgC m−2 h−1 over the month and showed very rapid and high variations. Particulate carbon export represented less than 5% of integrated primary production, suggesting that phytoplankton production was essentially sustained by internal recycling of organic matter and retained within the photic zone. While PON and POP fluxes paralleled one another, the elemental ratios POC/PON and POC/POP, varied widely over short-term periods. Values of these ratios generally higher than the conventional Redfield ratio, together with the very low chlorophyll a flux recorded in the traps (mean 0.017 μg m−2 h−1, and the high phaeopigment and acyl lipid hydrolysis metabolite concentrations of the settling material, indicated that the organic matter reaching 200 m depth was reworked (by grazing, fecal pellets production, degradation and that algal sinking, dominated by nano- and picoplankton, made a small contribution to the downward flux. Over time, the relative abundance of individual lipid classes in organic matter (OM changed from glycolipids-dominated to neutral (wax esters, triacylglycerols and phospholipids-dominated, suggesting ecosystem maturation as well as rapid and continual exchanges between dissolved, suspended and sinking pools. Our most striking result was documenting the rapid change in fluxes of the various measured parameters. In the situation encountered here, with dominant regenerated production, a decrease of fluxes was noticed during windy periods (possibly through reduction of grazing. But fluxes increased as soon as calm
1. Estimating flexural rigidity and load magnitude required for formation of Ross Island flexure moat
Science.gov (United States)
Jha, S.; Harry, D. L.; Wenman, C. P.
2017-12-01
Lithospheric flexural subsidence around Ross Island in West Antarctica led to formation of the Ross Island flexure moat. This subsidence was caused by two major volcanic phases on Ross Island. The first phase saw the first surficial expression of Ross Island and volcanism at Mt. Bird to the north of Ross Island, which lasted from 5.2 - 2.9 Ma. The second phase lasted from 1.78 Ma to present and is comprised of eruptions from Mt. Terror to the east, Mt. Erebus to the west and Hut Point Peninsula (HPP) to the south of Ross Island. Flexural subsidence of the lithosphere due to volcanism on Ross Island led to formation of a sedimentary moat around the island, which is preserved in stratigraphy imaged on seismic reflection profiles. We identified 5 unconformities (from deepest upward Ri, RMU1, RMU2, RMU3, RMU4) in the seismic surveys which correspond to flexural subsidence episodes around Ross Island since early Pliocene. Ri (4.4 Ma) lies near the bottom of the flexural moat and RMU4 near the seafloor and top of the moat fill. These unconformities were used to make isopach maps to constrain flexure modeling of the area. Isopach maps show circular or semi-circular flexure basins around Ross Island which is approximated using a continuous plate, point load flexure model. We used Ri - sea floor isopach to constrain flexure models for 5 profiles centered on 4 volcanic centers and trending radially out of Ross Island. Flexure models along two profiles beginning on Mt. Bird and one profile off HPP show a flexural rigidity range of 1.47 - 6.44 x 1018 Nm with load center of mass on Mt. Bird and on HPP, respectively. A similar model along a profile initiating on Mt. Terror, passing through Mt Erebus and extending west of Ross Island across the moat, yielded a higher flexural rigidity estimate of 2.03 x 1019 Nm with load centered at Mt. Erebus. A flexure model to the north east of Ross Island along a profile beginning at Mt Terror and trending north, provide the highest flexural
2. Changing Roots : Remodelling after the Ross Operation
NARCIS (Netherlands)
A. Mookhoek (Aart)
2016-01-01
textabstractThe Ross operation is a surgical intervention in which a diseased aortic valve is replaced by the pulmonary valve of the same patient. A donor valve replaces the pulmonary valve. In this thesis, several key unanswered clinical questions are explored. Early mortality after the Ross
3. Noncommutative Blackwell-Ross martingale inequality
Science.gov (United States)
We establish a noncommutative Blackwell-Ross inequality for supermartingales under a suitable condition which generalizes Khan’s work to the noncommutative setting. We then employ it to deduce an Azuma-type inequality.
4. Prevention measures for avoiding unexpected drifting of marine component in recovery equipment of significant metals from sea water. Positioning and monitoring system for marine component and improvement of its positioning accuracy
Energy Technology Data Exchange (ETDEWEB)
Tamada, Masao; Kasai, Noboru; Seko, Noriaki; Hasegawa, Shin; Takeda, Hayato; Katakai, Akio; Sugo, Takanobu [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment; Kawabata, Yukiya [Ebara Reseach Co., Ltd., Fujisawa, Kanagawa (Japan); Onuma, Kenji [Mitsubishi Materials Corp., Tokyo (Japan)
2001-11-01
Positioning and monitoring system for marine component in recovery equipment of significant metals from seawater with adsorbent was designed and assembled to avoid unexpected drifting accident. This system which was set on float part of the marine component obtains the positioning data from GPS satellites and sends them to Takasaki and Mutsu establishments through satellite communication. In both establishments, the position data were shown in computer displays. As characteristic test for 20 days in the real sea, 262 data were obtained every 2 hours. The twice of the distance root mean square (2DRMS) was 223.7 m. To improve this performance, three new functions were added to the present firmware. There are to raise positioning resolutions in longitude and latitude from 0.001 to 0.00001 degree, to remove the reflection of GPS signal from sea surface, and to average remaining three positioning data after maximum and minimum data were omitted from continuous five positioning data. The improved system shows the 2DRMS positioning of 15.5 m. This performance is enough to prevent marine component from its drifting accident. (author)
5. WATER TEMPERATURE and Other Data from DRIFTING PLATFORM From Chukchi Sea - NW Coast of Alaska from 1981-12-19 to 1982-01-01 (NODC Accession 8500079)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — The data were collected by Flow Industries, Inc. under contract number 03-78-B01-61 to NOAA . The data are primarily from drifting ice buoys and were collected in...
6. STS-110 Crew Interview: Jerry Ross
Science.gov (United States)
2002-01-01
STS-110 Mission Specialist Jerry Ross is seen during this preflight interview, where he gives a quick overview of the mission before answering questions about his inspiration to become an astronaut and his career path. Ross outlines his role in the mission in general, and specifically during the docking and extravehicular activities (EVAs). He describes the payload (S0 Truss and Mobile Transporter) and the dry run installation of the S0 truss that will take place the day before the EVA for the actual installation. Ross discusses the planned EVAs in detail and outlines what supplies will be left for the resident crew of the International Space Station (ISS). He ends with his thoughts on the most valuable aspect of the ISS.
7. Full production approaching at Rossing Uranium
International Nuclear Information System (INIS)
Anon.
1978-01-01
The Rossing uranium mine, in South West Africa's Namib Desert, is an extraordinary operation by any standards. The open pit mining operation; the highly complex metallurgical plant that, unlike those at mines in South Africa extracts the uranium as far as the uranium oxide or yellowcake product; the back-up services; and the team of people who run Rossing were all seen in action on a recent visit by Coal Gold and Base Minerals. This article examines the geology, the initial exploration and the open pit
8. Seaweed Competition: Ulva Sp. has the Potential to Produce the Betaine Lipid Diacylglyceryl-O-4’-(N,N,N,-Trimethyl) Homoserine (DGTS) in Order to Replace Phosphatidylcholine (PC) Under Phosphate-Limiting Conditions in the P-Limited Dutch Wadden Sea and Outcompete an Aggressive Non-Indigenous Gracilaria vermiculophylla Red Drift Algae Out of this Unique Unesco World Heritage Coastal Area
NARCIS (Netherlands)
Ginneken, van V.J.T.; Gittenberger, A.; Rensing, M.; Vries, de E.; Peeters, E.T.H.M.; Verheij, E.
2017-01-01
The present study tested in the Western Dutch Wadden Sea (WDW) UNESCO World Heritage Site why an on a global scale the aggressive non-indigenous red drift alga Gracilaria vermiculophylla didn’t succeed to overgrow the WDC. In such a multifaceted complex ecosystem like the dynamic WDC it seems like
9. Death age, seasonality, taphonomy and colonization of seal carcasses from Ulu Peninsula, James Ross Island, Antarctic Peninsula
Czech Academy of Sciences Publication Activity Database
Nývlt, D.; Nývltová Fišáková, Miriam; Barták, M.; Stachoň, Z.; Pavel, V.; Mlčoch, B.; Láska, K.
2016-01-01
Roč. 28, č. 1 (2016), s. 3-16 ISSN 0954-1020 Institutional support: RVO:68081758 Keywords : James Ross Island * preservation state * Prince Gustav Channel * sea ice * seal behaviour Subject RIV: EH - Ecology, Behaviour Impact factor: 1.461, year: 2016
10. 36 CFR 7.69 - Ross Lake National Recreation Area.
Science.gov (United States)
2010-07-01
... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Ross Lake National Recreation... INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.69 Ross Lake National Recreation Area... snowmobiles the following locations within the Ross Lake National Recreation Area: (1) State Highway 20, that...
11. The surface climatology of the Ross Ice Shelf Antarctica.
Science.gov (United States)
Costanza, Carol A; Lazzara, Matthew A; Keller, Linda M; Cassano, John J
2016-12-01
The University of Wisconsin-Madison Antarctic Automatic Weather Station (AWS) project has been making meteorological surface observations on the Ross Ice Shelf (RIS) for approximately 30 years. This network offers the most continuous set of routine measurements of surface meteorological variables in this region. The Ross Island area is excluded from this study. The surface climate of the RIS is described using the AWS measurements. Temperature, pressure, and wind data are analysed on daily, monthly, seasonal, and annual time periods for 13 AWS across the RIS. The AWS are separated into three representative regions - central, coastal, and the area along the Transantarctic Mountains - in order to describe specific characteristics of sections of the RIS. The climatology describes general characteristics of the region and significant changes over time. The central AWS experiences the coldest mean temperature, and the lowest resultant wind speed. These AWSs also experience the coldest potential temperatures with a minimum of 209.3 K at Gill AWS. The AWS along the Transantarctic Mountains experiences the warmest mean temperature, the highest mean sea-level pressure, and the highest mean resultant wind speed. Finally, the coastal AWS experiences the lowest mean pressure. Climate indices (MEI, SAM, and SAO) are compared to temperature and pressure data of four of the AWS with the longest observation periods, and significant correlation is found for most AWS in sea-level pressure and temperature. This climatology study highlights characteristics that influence the climate of the RIS, and the challenges of maintaining a long-term Antarctic AWS network. Results from this effort are essential for the broader Antarctic meteorology community for future research.
12. Coastal-change and glaciological map of the Ross Island area, Antarctica
Science.gov (United States)
Ferrigno, Jane G.; Foley, Kevin M.; Swithinbank, Charles; Williams, Richard S.
2010-01-01
Reduction in the area and volume of Earth?s two polar ice sheets is intricately linked to changes in global climate and to the resulting rise in sea level. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council. On the basis of these recommendations, the U.S. Geological Survey used its archive of satellite images to document changes in the cryospheric coastline of Antarctica and analyze the glaciological features of the coastal regions. The Ross Island area map is bounded by long 141? E. and 175? E. and by lat 76? S. and 81? S. The map covers the part of southern Victoria Land that includes the northwestern Ross Ice Shelf, the McMurdo Ice Shelf, part of the polar plateau and Transantarctic Mountains, the McMurdo Dry Valleys, northernmost Shackleton Coast, Hillary Coast, the southern part of Scott Coast, and Ross Island. Little noticeable change has occurred in the ice fronts on the map, so the focus is on glaciological features. In the western part of the map area, the polar plateau of East Antarctica, once thought to be a featureless region, has subtle wavelike surface forms (megadunes) and flow traces of glaciers that originate far inland and extend to the coast or into the Ross Ice Shelf. There are numerous outlet glaciers. Glaciers drain into the McMurdo Dry Valleys, through the Transantarctic Mountains into the Ross Sea, or into the Ross Ice Shelf. Byrd Glacier is the largest. West of the Transantarctic Mountains are areas of blue ice, readily identifiable on Landsat images, that have been determined to be prime areas for finding meteorites. Three subglacial lakes have been identified in the map area. Because McMurdo Station, the main U.S. scientific research station in Antarctica, is located on Ross Island in the map area, many of these and other features in the area have been studied extensively. The paper version of this map is
13. Drift chamber detectors
International Nuclear Information System (INIS)
Duran, I.; Martinez Laso, L.
1989-01-01
A review of High Energy Physics detectors based on drift chambers is presented. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysied, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author)
14. Drift Chambers detectors
International Nuclear Information System (INIS)
Duran, I.; Martinez laso, L.
1989-01-01
We present here a review of High Energy Physics detectors based on drift chambers. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysed, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author) 115 refs
15. Sir Ronald Ross and the Malarial Parasite
1997-08-20
Aug 20, 1997 ... In 1857, a General in the Indian Army, Sir C C G Ross and his wife Matilda .... generally low-caste Indians who required a fee before drinking the water and ... nary demand being made upon their systems, as by fatigue, chill,.
16. Sir Ronald Ross and the Malarial Parasite
Home; Journals; Resonance – Journal of Science Education; Volume 11; Issue 7. Sir Ronald Ross and the Malarial Parasite - Discovery of its Route - From Man to Mosquito and Back. Shobhona Sharma. General Article Volume 11 Issue 7 July 2006 pp 4-13 ...
17. Original monitoring of desert dust in African air masses transported over the Mediterranean Sea by quasi-Lagrangian drifting balloons and sounding balloons during the summer 2013 ChArMEx field campaign
Science.gov (United States)
Dulac, F.; Renard, J. B.; Durand, P.; Denjean, C.; Bourgeois, Q.; Vignelles, D.; Jeannot, M.; Mallet, M.; Verdier, N.
2017-12-01
This study focuses on in situ balloon-borne measurements of mineral dust from summer regional field campaigns in the western Mediterranean basin performed in the framework of ChArMEx (the Chemistry and Aerosol Mediterranean Experiment; see special issue https://www.atmos-chem-phys.net/special_issue334.html). Due to long-range transport from Africa, the lower troposphere over this regional sea is subject to high levels of desert dust with a maximum during the long dry and sunny Mediterranean summer season. Based on developments of boundary-layer pressurized balloons (BLPBs) and of a dedicated optical particle counter named LOAC (Light Optical Aerosol Counter/sizer), we were able to perform original quasi-Lagrangian monitoring of desert dust aerosols over the sea. The strategy combined classical sounding balloons and drifting BLPBs to document both the vertical distribution and long-range transport. A total of 27 LOAC flights were successfully conducted from Minorca Isl. (Spain) or Levant Isl. (France), during 4 Saharan dust transport events, including 10 flights with BLPBs at drifting altitudes between 2.0 and 3.3 km above sea level. The longest flight exceeded 700 km and lasted more than 25 h. Numerous tests and validations of LOAC measurements were performed to qualify the instrument, including comparisons with concurrent airborne measurements, sounding balloons, and remote sensing measurements with an AERONET sun-photometer, and a ground-based and the CALIOP lidar systems. Aerosol optical depths in the balloon vicinity did not exceed about 0.4 but the presence of turbid dust layers was confirmed thanks to dual scattering angle measurements by LOAC allowing the identification of dust particles. LOAC data could generally be fitted by a 3-mode lognormal distribution at roughly 0.2, 4 and 30 µm in modal diameter. Up to about 10-4 dust particles larger than 40 µm per cm3 are reported and no significant evolution of the size distribution was observed during the
18. Comparison of the Ross/Ross-Konno aortic root in children before and after the age of 18 months.
Science.gov (United States)
Lo Rito, Mauro; Davies, Ben; Brawn, William J; Jones, Timothy J; Khan, Natasha; Stickley, John; Barron, David J
2014-09-01
Evaluation of long-term results after the Ross/Ross-Konno operation in patients Ross/Ross-Konno operation (1991-2011). Data were obtained from hospital records and follow-up was 100% complete. Between January 1991 and December 2011, 140 patients underwent the Ross/Ross-Konno operation and 22 patients were Ross operation and 8 patients a Ross-Konno operation. Presentation at surgery was aortic valve stenosis in 13, regurgitation in 7 and mixed disease in 2. Only 4 patients (18%) had no surgery prior to Ross/Ross-Konno, and among the others the previous most frequent operation was aortic valvotomy (55%). There were 3 early deaths, all in high-risk cases with poor preoperative left ventricular function. At discharge there was no neoaortic regurgitation in 10, trivial in 4 and mild in 5. The median follow-up is 10.8 years (range 0.96-21). There was 1 late death due to progressive ventricular dysfunction 2.4 years after Ross-Konno and mitral valve replacement. Survival for patients 18-months patients (P Ross/Ross-Konno can be invaluable in the younger age group but not without risk in the setting of ventricular dysfunction. Long-term performance of the neoaortic valve is significantly better than in older children, which is related to maintenance of normal root dimensions compared with progressive dilatation in patients undergoing Ross/Ross-Konno at older ages. © The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
19. Modelling sea ice formation in the Terra Nova Bay polynya
Science.gov (United States)
Sansiviero, M.; Morales Maqueda, M. Á.; Fusco, G.; Aulicino, G.; Flocco, D.; Budillon, G.
2017-02-01
Antarctic sea ice is constantly exported from the shore by strong near surface winds that open leads and large polynyas in the pack ice. The latter, known as wind-driven polynyas, are responsible for significant water mass modification due to the high salt flux into the ocean associated with enhanced ice growth. In this article, we focus on the wind-driven Terra Nova Bay (TNB) polynya, in the western Ross Sea. Brine rejected during sea ice formation processes that occur in the TNB polynya densifies the water column leading to the formation of the most characteristic water mass of the Ross Sea, the High Salinity Shelf Water (HSSW). This water mass, in turn, takes part in the formation of Antarctic Bottom Water (AABW), the densest water mass of the world ocean, which plays a major role in the global meridional overturning circulation, thus affecting the global climate system. A simple coupled sea ice-ocean model has been developed to simulate the seasonal cycle of sea ice formation and export within a polynya. The sea ice model accounts for both thermal and mechanical ice processes. The oceanic circulation is described by a one-and-a-half layer, reduced gravity model. The domain resolution is 1 km × 1 km, which is sufficient to represent the salient features of the coastline geometry, notably the Drygalski Ice Tongue. The model is forced by a combination of Era Interim reanalysis and in-situ data from automatic weather stations, and also by a climatological oceanic dataset developed from in situ hydrographic observations. The sensitivity of the polynya to the atmospheric forcing is well reproduced by the model when atmospheric in situ measurements are combined with reanalysis data. Merging the two datasets allows us to capture in detail the strength and the spatial distribution of the katabatic winds that often drive the opening of the polynya. The model resolves fairly accurately the sea ice drift and sea ice production rates in the TNB polynya, leading to
20. Tidal Modulation of Ice-shelf Flow: a Viscous Model of the Ross Ice Shelf
Science.gov (United States)
Brunt, Kelly M.; MacAyeal, Douglas R.
2014-01-01
Three stations near the calving front of the Ross Ice Shelf, Antarctica, recorded GPS data through a full spring-neap tidal cycle in November 2005. The data revealed a diurnal horizontal motion that varied both along and transverse to the long-term average velocity direction, similar to tidal signals observed in other ice shelves and ice streams. Based on its periodicity, it was hypothesized that the signal represents a flow response of the Ross Ice Shelf to the diurnal tides of the Ross Sea. To assess the influence of the tide on the ice-shelf motion, two hypotheses were developed. The first addressed the direct response of the ice shelf to tidal forcing, such as forces due to sea-surface slopes or forces due to sub-ice-shelf currents. The second involved the indirect response of ice-shelf flow to the tidal signals observed in the ice streams that source the ice shelf. A finite-element model, based on viscous creep flow, was developed to test these hypotheses, but succeeded only in falsifying both hypotheses, i.e. showing that direct tidal effects produce too small a response, and indirect tidal effects produce a response that is not smooth in time. This nullification suggests that a combination of viscous and elastic deformation is required to explain the observations.
1. Characteristics and processing of seismic data collected on thick, floating ice: Results from the Ross Ice Shelf, Antarctica
Science.gov (United States)
Beaudoin, Bruce C.; ten Brink, Uri S.; Stern, Tim A.
1992-01-01
Coincident reflection and refraction data, collected in the austral summer of 1988/89 by Stanford University and the Geophysical Division of the Department of Scientific and Industrial Research, New Zealand, imaged the crust beneath the Ross Ice Shelf, Antarctica. The Ross Ice Shelf is a unique acquisition environment for seismic reflection profiling because of its thick, floating ice cover. The ice shelf velocity structure is multilayered with a high velocity‐gradient firn layer constituting the upper 50 to 100 m. This near surface firn layer influences the data character by amplifying and frequency modulating the incoming wavefield. In addition, the ice‐water column introduces pervasive, high energy seafloor, intra‐ice, and intra‐water multiples that have moveout velocities similar to the expected subseafloor primary velocities. Successful removal of these high energy multiples relies on predictive deconvolution, inverse velocity stack filtering, and frequency filtering. Removal of the multiples reveals a faulted, sedimentary wedge which is truncated at or near the seafloor. Beneath this wedge the reflection character is diffractive to a two‐way traveltime of ∼7.2 s. At this time, a prominent reflection is evident on the southeast end of the reflection profile. This reflection is interpreted as Moho indicating that the crust is ∼21-km thick beneath the profile. These results provide seismic evidence that the extensional features observed in the Ross Sea region of the Ross Embayment extend beneath the Ross Ice Shelf.
2. STS-88 Crew Interview: Jerry Ross
Science.gov (United States)
1998-01-01
Jerry Ross discusses the seven-day mission that will be highlighted by the mating of the U.S.-built Node 1 station element to the Functional Energy Block (FGB) which will already be in orbit, and two spacewalks to connect power and data transmission cables between the Node and the FGB. Node 1 will be the first Space Station hardware delivered by the Space Shuttle. He also disscusses the assembly sequence. The crew will conduct a series of rendezvous maneuvers similar to those conducted on other Shuttle missions to reach the orbiting FGB. Once the two elements are docked, Ross and Newman will conduct two scheduled spacewalks to connect power and data cables between the Node, PMAs and the FGB. The day following the spacewalks, Endeavour will undock from the two components, completing the first Space Station assembly mission.
3. Dike/Drift Interactions
Energy Technology Data Exchange (ETDEWEB)
E. Gaffiney
2004-11-23
This report presents and documents the model components and analyses that represent potential processes associated with propagation of a magma-filled crack (dike) migrating upward toward the surface, intersection of the dike with repository drifts, flow of magma in the drifts, and post-magma emplacement effects on repository performance. The processes that describe upward migration of a dike and magma flow down the drift are referred to as the dike intrusion submodel. The post-magma emplacement processes are referred to as the post-intrusion submodel. Collectively, these submodels are referred to as a conceptual model for dike/drift interaction. The model components and analyses of the dike/drift interaction conceptual model provide the technical basis for assessing the potential impacts of an igneous intrusion on repository performance, including those features, events, and processes (FEPs) related to dike/drift interaction (Section 6.1).
4. Dike/Drift Interactions
International Nuclear Information System (INIS)
Gaffiney, E.
2004-01-01
This report presents and documents the model components and analyses that represent potential processes associated with propagation of a magma-filled crack (dike) migrating upward toward the surface, intersection of the dike with repository drifts, flow of magma in the drifts, and post-magma emplacement effects on repository performance. The processes that describe upward migration of a dike and magma flow down the drift are referred to as the dike intrusion submodel. The post-magma emplacement processes are referred to as the post-intrusion submodel. Collectively, these submodels are referred to as a conceptual model for dike/drift interaction. The model components and analyses of the dike/drift interaction conceptual model provide the technical basis for assessing the potential impacts of an igneous intrusion on repository performance, including those features, events, and processes (FEPs) related to dike/drift interaction (Section 6.1)
5. The Drift Burst Hypothesis
OpenAIRE
Christensen, Kim; Oomen, Roel; Renò, Roberto
2016-01-01
The Drift Burst Hypothesis postulates the existence of short-lived locally explosive trends in the price paths of financial assets. The recent US equity and Treasury flash crashes can be viewed as two high profile manifestations of such dynamics, but we argue that drift bursts of varying magnitude are an expected and regular occurrence in financial markets that can arise through established mechanisms such as feedback trading. At a theoretical level, we show how to build drift bursts into the...
6. Rectangular drift tube characteristics
International Nuclear Information System (INIS)
Denisov, D.S.; Musienko, Yu.V.
1985-01-01
Results on the study of the characteristics of a 50 x 100 mm aluminium drift tube are presented. The tube was filled with argon-methane and argon-isobutane mixtures. With 16 per cent methane concentration the largest deviation from a linear relation between the drift time and the drift path over 50 mm is less than 2 mm. The tube filled with argon-isobutane mixture is capable of operating in a limited streamer mode
7. Dike/Drift Interactions
Energy Technology Data Exchange (ETDEWEB)
E.S. Gaffney
2003-10-08
This report documents the model of events associated with a potential intrusion of magma from a volcanic dike into a drift or drifts in the Yucca Mountain Nuclear Waste Repository. The following topics are included in this report: (1) A discussion of dike propagation, which provides the basis for describing the path that a representative dike, or swarm of dikes, would follow during an event. (2) A discussion of magma flow, which evaluates the interaction at the junction of the propagating dike with the drift and the movement of magmatic products into and down drifts and, potentially, through a drift to the surface by way of access drift or a secondary dike opened up along the drift. (3) A discussion of gas flow and conductive cooling of a magma-filled drift, describing how an adjacent drift that has not been intersected by a dike could be affected by post-intrusion phenomena. Note that a gas flow analysis is also addressed in ''Igneous Intrusion Impacts on Waste Form and Waste Packages'' (BSC 2003 [DIRS 161810]), and those results are consistent with the results presented in this report.
8. Dike/Drift Interactions
International Nuclear Information System (INIS)
E.S. Gaffney
2003-01-01
This report documents the model of events associated with a potential intrusion of magma from a volcanic dike into a drift or drifts in the Yucca Mountain Nuclear Waste Repository. The following topics are included in this report: (1) A discussion of dike propagation, which provides the basis for describing the path that a representative dike, or swarm of dikes, would follow during an event. (2) A discussion of magma flow, which evaluates the interaction at the junction of the propagating dike with the drift and the movement of magmatic products into and down drifts and, potentially, through a drift to the surface by way of access drift or a secondary dike opened up along the drift. (3) A discussion of gas flow and conductive cooling of a magma-filled drift, describing how an adjacent drift that has not been intersected by a dike could be affected by post-intrusion phenomena. Note that a gas flow analysis is also addressed in ''Igneous Intrusion Impacts on Waste Form and Waste Packages'' (BSC 2003 [DIRS 161810]), and those results are consistent with the results presented in this report
Energy Technology Data Exchange (ETDEWEB)
Dwayne C. Kicker
2001-09-28
A statistical description of the probable block sizes formed by fractures around the emplacement drifts has been developed for each of the lithologic units of the repository host horizon. A range of drift orientations with the drift azimuth varied in 15{sup o} increments has been considered in the static analysis. For the quasi-static seismic analysis, and the time-dependent and thermal effects analysis, two drift orientations have been considered: a drift azimuth of 105{sup o} and the current emplacement drift azimuth of 75{sup o}. The change in drift profile resulting from progressive deterioration of the emplacement drifts has been assessed both with and without backfill. Drift profiles have been determined for four different time increments, including static (i.e., upon excavation), 200 years, 2,000 years, and 10,000 years. The effect of seismic events on rock fall has been analyzed. Block size distributions and drift profiles have been determined for three seismic levels, including a 1,000-year event, a 5,000-year event, and a 10,000-year event. Data developed in this modeling and analysis activity have been entered into the TDMS (DTN: MO0109RDDAAMRR.003). The following conclusions have resulted from this drift degradation analysis: (1) The available fracture data are suitable for supporting a detailed key block analysis of the repository host horizon rock mass. The available data from the north-south Main Drift and the east-west Cross Drift provide a sufficient representative fracture sample of the repository emplacement drift horizon. However, the Tptpln fracture data are only available from a relatively small section of the Cross Drift, resulting in a smaller fracture sample size compared to the other lithologic units. This results in a lower degree of confidence that the key block data based on the Tptpln data set is actually representative of the overall Tptpln key block population. (2) The seismic effect on the rock fall size distribution for all events
10. Ross Versus Non-Ross Aortic Valve Replacement in Children: A 22-Year Single Institution Comparison of Outcomes.
Science.gov (United States)
Brown, John W; Patel, Parth M; Ivy Lin, Jiuann-Huey; Habib, Asma S; Rodefeld, Mark D; Turrentine, Mark W
2016-05-01
The Ross aortic valve replacement (AVR) has been the AVR of choice for children at our center since 1993. Absence or inadequate quality of the pulmonary valve or, less commonly, family or surgeon preference caused us to select an alternative AVR prosthesis for some children. This review compares the outcomes of 42 children who received a non-Ross AVR with 115 children undergoing Ross root replacement at our institution during the most recent 22 years. A retrospective chart review of the 42 pediatric non-Ross AVRs was compared with 115 Ross AVRs. The mean age at AVR was 11.0 ± 6.5 years (range, 1 month to 18 years) for the non-Ross and 11.4 ± 5.5 years (range, 6 weeks to 18 years) for the Ross groups. Follow-up was 7.8 ± 6.2 years for the Ross group and 8.7 ± 6.5 years for the non-Ross group. The Ross AVR technique was modified in 2000; these modifications were applied to 72 patients (63%) of the total Ross AVR group. All-cause early and late mortality of the non-Ross AVR group was 17% compared with 4% for the Ross cohort (p = 0.017). The actuarial survival rate at 20 years for the non-Ross AVR group was 81% compared with 94% for the Ross group (p = 0.018). Reintervention rate was 29% (12/38) in the non-Ross group and 28% (32/115) in the entire Ross group (60% [26/43] before 2000, and 8% [6/72] after 2000). Thromboemboli, bleeding, and endocarditis occurred in 2.4%, 1.4%, and 10% in the non-Ross group compared with 0.9%, 2.6%, and 1.7% in the Ross AVR group (p = 0.46, 0.01, and 0.02), respectively. Patients in the non-Ross group had a significantly higher recurrent or persistent aortic valve gradient (>20 mm Hg) than did patients in the Ross group at most recent follow-up (p Ross AVR than with other types of AVR prostheses. The Ross AVR remains the treatment of choice for children who have an adequate pulmonary valve. Reoperation for Ross root dilatation, regurgitation, or both (only 6% since our modifications in 2000) has markedly reduced the main drawbacks
11. An electrodeless drift chamber
International Nuclear Information System (INIS)
Allison, J.; Barlow, R.J.; Bowdery, C.K.; Duerdoth, I.; Rowe, P.G.
1982-01-01
We describe a chamber in which the drift field is controlled by the deposition of electrostatic charge on an insulating surface. The chamber operates with good efficiency and precision for observed drift distances of up to 45 cm, promises to be extremely robust and adaptable and offers a very cheap way of making particle detectors. (orig.)
12. Modeling concept drift
DEFF Research Database (Denmark)
Borchani, Hanen; Martinez, Ana Maria; Masegosa, Andrés R.
2015-01-01
An often used approach for detecting and adapting to concept drift when doing classification is to treat the data as i.i.d. and use changes in classification accuracy as an indication of concept drift. In this paper, we take a different perspective and propose a framework, based on probabilistic ...... data set from a Spanish bank....
13. Time dependent drift Hamiltonian
International Nuclear Information System (INIS)
Boozer, A.H.
1982-04-01
The motion of individual charged particles in a given magnetic and an electric fields is discussed. An idea of a guiding center distribution function f is introduced. The guiding center distribution function is connected to the asymptotic Hamiltonian through the drift kinetic equation. The general non-stochastic magnetic field can be written in a contravariant and a covariant forms. The drift Hamiltonian is proposed, and the canonical gyroradius is presented. The proposed drift Hamiltonian agrees with Alfven's drift velocity to lowest non-vanishing order in the gyroradius. The relation between the exact, time dependent equations of motion and the guiding center equation is clarified by a Lagrangian analysis. The deduced Lagrangian represents the drift motion. (Kato, T.)
14. Seismology on drifting icebergs: Catching earthquakes, tsunamis, swell, and iceberg music
Science.gov (United States)
Okal, E. A.; Macayeal, D. R.
2006-12-01
For the past 3 years, we have operated seismometers on large icebergs either parked or drifting in the Ross Sea, with an additional station at Nascent, where the next section of the Ross Ice Shelf is expected to calf. Apart from their primary goal of studying in situ tremor generated inside the ice, presumed to arise during collisions and fragmentation, our stations have functioned as teleseismic observatories, despite a noisy environment in the 20-100 mHz frequency band, corresponding to the free bobbing and rolling of the icebergs. As expected, both P and Rayleigh waves from distant earthquakes are recorded on the vertical channels as unperturbed ground motion, with acceptable values of energy flux (P) or magnitude (Rayleigh); however, due to noise level at mantle periods, only Rayleigh waves from the largest events (Sumatra 2004; Nias 2005) could be quantified meaningfully. T waves from distant earthquakes along the EPR can be recorded, but the acoustic-to-seismic transition at the ice boundary is less effcient than at typical island stations. The 2004 Sumatra tsunami was recorded on all 3 components at the 3 stations; the inferred amplitudes (about 15 cm vertical and 1.3 m horizontal, peak-to-peak) are in general agreement with global simulations, and suggest that the bergs rode the tsunami without intrinsic deformation; a small tsunami is also detected for the Macquarie earthquake of 23 Dec. 2004. Our stations regularly recorded long wavetrains in the 40-60 mHz range, dispersed under the deep-water approximation, and corresponding to sea swell propagating across the entire ocean from major storms in the Northern and Equatorial Pacific. In the case of a major depression in the Gulf of Alaska in Late October 2005, recorded on the ice 6 days later, Iceberg B-15A underwent at the same time a severe fragmentation, leading to legitimate speculation on the role of storm waves in triggering its break-up. Finally, our stations recorded a large number of local signals
15. Abstraction of Drift Seepage
International Nuclear Information System (INIS)
J.T. Birkholzer
2004-01-01
This model report documents the abstraction of drift seepage, conducted to provide seepage-relevant parameters and their probability distributions for use in Total System Performance Assessment for License Application (TSPA-LA). Drift seepage refers to the flow of liquid water into waste emplacement drifts. Water that seeps into drifts may contact waste packages and potentially mobilize radionuclides, and may result in advective transport of radionuclides through breached waste packages [''Risk Information to Support Prioritization of Performance Assessment Models'' (BSC 2003 [DIRS 168796], Section 3.3.2)]. The unsaturated rock layers overlying and hosting the repository form a natural barrier that reduces the amount of water entering emplacement drifts by natural subsurface processes. For example, drift seepage is limited by the capillary barrier forming at the drift crown, which decreases or even eliminates water flow from the unsaturated fractured rock into the drift. During the first few hundred years after waste emplacement, when above-boiling rock temperatures will develop as a result of heat generated by the decay of the radioactive waste, vaporization of percolation water is an additional factor limiting seepage. Estimating the effectiveness of these natural barrier capabilities and predicting the amount of seepage into drifts is an important aspect of assessing the performance of the repository. The TSPA-LA therefore includes a seepage component that calculates the amount of seepage into drifts [''Total System Performance Assessment (TSPA) Model/Analysis for the License Application'' (BSC 2004 [DIRS 168504], Section 6.3.3.1)]. The TSPA-LA calculation is performed with a probabilistic approach that accounts for the spatial and temporal variability and inherent uncertainty of seepage-relevant properties and processes. Results are used for subsequent TSPA-LA components that may handle, for example, waste package corrosion or radionuclide transport
International Nuclear Information System (INIS)
G.H. Nieder-Westermann
2005-01-01
The outputs from the drift degradation analysis support scientific analyses, models, and design calculations, including the following: (1) Abstraction of Drift Seepage; (2) Seismic Consequence Abstraction; (3) Structural Stability of a Drip Shield Under Quasi-Static Pressure; and (4) Drip Shield Structural Response to Rock Fall. This report has been developed in accordance with ''Technical Work Plan for: Regulatory Integration Modeling of Drift Degradation, Waste Package and Drip Shield Vibratory Motion and Seismic Consequences'' (BSC 2004 [DIRS 171520]). The drift degradation analysis includes the development and validation of rockfall models that approximate phenomenon associated with various components of rock mass behavior anticipated within the repository horizon. Two drift degradation rockfall models have been developed: the rockfall model for nonlithophysal rock and the rockfall model for lithophysal rock. These models reflect the two distinct types of tuffaceous rock at Yucca Mountain. The output of this modeling and analysis activity documents the expected drift deterioration for drifts constructed in accordance with the repository layout configuration (BSC 2004 [DIRS 172801])
17. Approximate Stokes Drift Profiles in Deep Water
Science.gov (United States)
Breivik, Øyvind; Janssen, Peter A. E. M.; Bidlot, Jean-Raymond
2014-09-01
A deep-water approximation to the Stokes drift velocity profile is explored as an alternative to the monochromatic profile. The alternative profile investigated relies on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons with parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profile gives a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. The alternative profile comes at no added numerical cost compared to the monochromatic profile.
18. Elisabeth Kubler-Ross as a Religious Leader.
Science.gov (United States)
Klass, Dennis; Hutch, Richard A.
1986-01-01
Considers Elisabeth Kubler-Ross as a charismatic religious leader and examines the feminine quality of her message and leadership style. An examination of the prospects for an enduring cultural innovation based on Kubler-Ross's work concludes that her leadership does not conform to conditions necessary for institutionalization of her charismatic…
19. Success: Richard Dyer on Diana Ross [and Beyond
NARCIS (Netherlands)
Kooijman, J.
2016-01-01
In June 1982, film scholar Richard Dyer published a two-page essay on African-American star Diana Ross in the journal Marxism Today. Part of Dyer’s essay focuses on the American conception of success and specifically on how Ross is one of the few black artists who has been "allowed" to be such a
20. Histomorphometry of the esophagus of adult ross broilers | Mobini ...
African Journals Online (AJOL)
The purpose of this study was to determine the histomorphometrical variations of esophagus at different regions in Ross broilers. Twenty four apparently healthy adult Ross broilers (12 females and 12 males), aged from 7 to 9 weeks, were used. Tissue samples were taken from middle parts of cervical and thoracic regions of ...
1. Collisional drift fluids and drift waves
International Nuclear Information System (INIS)
Pfirsch, D.; Correa-Restrepo, D.
1995-05-01
The usual theoretical description of drift-wave turbulence (considered to be one possible cause of anomalous transport in a plasma), e.g. the Hasegawa-Wakatani theory, makes use of various approximations, the effect of which is extremely difficult to assess. This concerns in particular the conservation laws for energy and momentum. The latter is important as concerns charge separation and resulting electric fields which are possibly related to the L-H transition. Energy conservation is crucial for the stability behaviour; it will be discussed via an example. New collisional multispecies drift-fluid equations were derived by a new method which yields in a transparent way conservation of energy and total angular momentum, and the law for energy dissipation. Both electrostatic and electromagnetic field variations are considered. The method is based primarily on a Lagrangian for dissipationless fluids in drift approximation with isotropic pressures. The dissipative terms are introduced by adding corresponding terms to the ideal equations of motion and of the pressures. The equations of motion, of course, no longer result from a Lagrangian via Hamilton's principle. Their relation to the ideal equations imply, however, also a relation to the ideal Lagrangian of which one can take advantage. Instead of introducing heat conduction one can also assume isothermal behaviour, e.g. T ν (x)=const. Assumptions of this kind are often made in the literature. The new method of introducing dissipation is not restricted to the present kind of theories; it can equally well be applied to theories such as multi-fluid theories without using the drift approximation of the present paper. Linear instability is investigated via energy considerations and the implications of taking ohmic resistivity into account are discussed. (orig./WL)
2. World in the drift-ice; Ryuhyo no sekai
Energy Technology Data Exchange (ETDEWEB)
Aota, M. [Hokkaido Univ., Hokkaido (Japan)
1999-06-07
What freezes in the sea in the circumference in our country is only Sea of Okhotsk. What will be the drift-ice for the people who live in this beach? The distress by the drift-ice often occurred. The drift-ice spoils tearing, shell in the pickpocket in respect of the fishing gear in respect of destruction and kelp. The boat was landed, when the drift-ice came, the fisherman came out, and it went to the labor. The seafood processing field becomes also the closure condition. The drift-ice was a white demon for people of the beach, and it was a troublesome person. In the meantime, the drift-ice soothes the wave, and it becomes a natural float breakwater, the coast is kept, and the salt damage does be held. There is some that it is faced the sea off beach cleaning. People of the seashore in Okohtsk live with the drift-ice with merits and both demerit sideses. (NEDO)
3. Major adverse cardiac and cerebrovascular events after the ross procedure: A report from the german-dutch ross registry
NARCIS (Netherlands)
H. Sievers (Hans Hinrich); U. Stierle (Ulrich); E.I. Charitos (Efstratios); T. Hanke; M. Misfeld (Martin); J.F.M. Bechtel (Matthias); A. Gorski (Armin); U.F. Franke (Ulrich); B. Graf (Bernhard); D.R. Robinson (Derek); A.J.J.C. Bogers (Ad); A. Dodge-Khatami (Ali); J.O. Boehm (Juergen); J.G. Rein (Joachim); C.A. Botha (Cornelius); R. Lange (Rüdiger); J. Hoerer (Juergen); A. Moritz (Anton); T. Wahlers (Thorsten); M. Breuer (Martin); K. Ferrari-Kuehne (Katharina); R. Hetzer (Roland); M. Huebler (Michael); G. Ziemer (Gerhard); J.J.M. Takkenberg (Hanneke); W. Hemmer
2010-01-01
textabstractBackground-: The purpose of the study is to report major cardiac and cerebrovascular events after the Ross procedure in the large adult and pediatric population of the German-Dutch Ross registry. These data could provide an additional basis for discussions among physicians and a source
4. Drift Scale THM Model
International Nuclear Information System (INIS)
Rutqvist, J.
2004-01-01
This model report documents the drift scale coupled thermal-hydrological-mechanical (THM) processes model development and presents simulations of the THM behavior in fractured rock close to emplacement drifts. The modeling and analyses are used to evaluate the impact of THM processes on permeability and flow in the near-field of the emplacement drifts. The results from this report are used to assess the importance of THM processes on seepage and support in the model reports ''Seepage Model for PA Including Drift Collapse'' and ''Abstraction of Drift Seepage'', and to support arguments for exclusion of features, events, and processes (FEPs) in the analysis reports ''Features, Events, and Processes in Unsaturated Zone Flow and Transport and Features, Events, and Processes: Disruptive Events''. The total system performance assessment (TSPA) calculations do not use any output from this report. Specifically, the coupled THM process model is applied to simulate the impact of THM processes on hydrologic properties (permeability and capillary strength) and flow in the near-field rock around a heat-releasing emplacement drift. The heat generated by the decay of radioactive waste results in elevated rock temperatures for thousands of years after waste emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, resulting in water redistribution and altered flow paths. These temperatures will also cause thermal expansion of the rock, with the potential of opening or closing fractures and thus changing fracture permeability in the near-field. Understanding the THM coupled processes is important for the performance of the repository because the thermally induced permeability changes potentially effect the magnitude and spatial distribution of percolation flux in the vicinity of the drift, and hence the seepage of water into the drift. This is important because a sufficient amount of water must be available within a
International Nuclear Information System (INIS)
D. Kicker
2004-01-01
Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal stress. (3) The DRKBA
Energy Technology Data Exchange (ETDEWEB)
D. Kicker
2004-09-16
Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal
7. Spiral silicon drift detectors
International Nuclear Information System (INIS)
Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Lutz, G.; Kemmer, J.; Prechtel, U.; Ziemann, T.
1988-01-01
An advanced large area silicon photodiode (and x-ray detector), called Spiral Drift Detector, was designed, produced and tested. The Spiral Detector belongs to the family of silicon drift detectors and is an improvement of the well known Cylindrical Drift Detector. In both detectors, signal electrons created in silicon by fast charged particles or photons are drifting toward a practically point-like collection anode. The capacitance of the anode is therefore kept at the minimum (0.1pF). The concentric rings of the cylindrical detector are replaced by a continuous spiral in the new detector. The spiral geometry detector design leads to a decrease of the detector leakage current. In the spiral detector all electrons generated at the silicon-silicon oxide interface are collected on a guard sink rather than contributing to the detector leakage current. The decrease of the leakage current reduces the parallel noise of the detector. This decrease of the leakage current and the very small capacities of the detector anode with a capacitively matched preamplifier may improve the energy resolution of Spiral Drift Detectors operating at room temperature down to about 50 electrons rms. This resolution is in the range attainable at present only by cooled semiconductor detectors. 5 refs., 10 figs
8. The Paediatric Cardiology Hall of Fame – Donald Nixon Ross.
Science.gov (United States)
Somerville, Jane
2015-10-01
Donald Nixon Ross, FRCS (4 October 1922 to 7 July 2014) was a South African-born British cardiothoracic surgeon, who developed the pulmonary autograft, known as the Ross procedure, for the treatment of aortic valve disease, and also performed the first heart transplant in the United Kingdom in 1968. This paper, written by Jane Somerville, Professor of Cardiology [Retired], Imperial College London, London, United Kingdom, provides the personal recollections about Donald Ross from Jane Somerville, and thus provides a unique snapshot of cardiac surgical history.
International Nuclear Information System (INIS)
Rawlings, K.J.
1987-01-01
The conditions under which the energy resolution of a radial semiconductor drift chamber based detector system becomes dominated by the step noise from the detector dark current have been investigated. To minimise the drift chamber dark current attention should be paid to carrier generation at Si/SiO 2 interfaces. This consideration conflicts with the desire to reduce the signal risetime: a higher drift field for shorter signal pulses requires a larger area of SiO 2 . Calculations for the single shaping and pseudo Gaussian passive filters indicate that for the same degree of signal risetime sensitivity in a system dominated by the step noise from the detector dark current, the pseudo Gaussian filter gives only a 3% improvement in signal/noise and 12% improvement in rate capability compared with the single shaper performance. (orig.)
10. Nonlinear drift tearing mode
International Nuclear Information System (INIS)
Zelenyj, L.M.; Kuznetsova, M.M.
1989-01-01
Nonlinear study of magnetic perturbation development under single-mode conditions in collision-free plasma in configurations with the magnetic field shear is investigated. Results are obtained with regard of transverse component of electrical field and its effect on ion dynamics within wide range of ion Larmor radius value and values of magnetic field shear. Increments of nonlinear drift tearing mode are obtained and it is shown that excitation drastic conditions of even linearly stable modes are possible. Mechanism of instability nonlinear stabilization is considered and the value of magnetic island at the saturation threshold is estimeted. Energy of nonlinear drift tearing mode is discussed
11. The Drift Burst Hypothesis
DEFF Research Database (Denmark)
Christensen, Kim; Oomen, Roel; Renò, Roberto
are an expected and regular occurrence in financial markets that can arise through established mechanisms such as feedback trading. At a theoretical level, we show how to build drift bursts into the continuous-time Itô semi-martingale model in such a way that the fundamental arbitrage-free property is preserved......, currencies and commodities. We find that the majority of identified drift bursts are accompanied by strong price reversals and these can therefore be regarded as “flash crashes” that span brief periods of severe market disruption without any material longer term price impacts....
12. The Ross Procedure in Pediatric Patients: A 20-Year Experience of Ross Procedure in a Single Institution.
Science.gov (United States)
Yoon, Dong Woog; Yang, Ji-Hyuk; Jun, Tae-Gook; Park, Pyo Won
2017-08-01
The Ross/Ross-Konno procedure is considered a good option for irreparable aortic valve disease in pediatric patients because of its hemodynamic performance and potential for growth of the pulmonary autograft. This study is a review of the long-term results of our 20-year experience with the Ross and Ross-Konno operations in a single institution. Between June 1995 and January 2016, 16 consecutive patients (mean age, 6.0±5.9 years; range, 16 days to 17.4 years) underwent either a Ross operation (n=9) or a Ross-Konno operation (n=7). The study included 12 males and 4 females, with a median follow-up period of 47 months (range, 6 to 256 months). There were no cases of in-hospital or late mortality. Six reoperations were performed in 5 patients. Four patients underwent right ventricular-pulmonary artery (RV-PA) conduit replacement. Two patients underwent concomitant replacement of the pulmonary autograft and RV-PA conduit 10 years and 8 years after the Ross operation, respectively. The rate of freedom from adverse outcomes of the pulmonary autograft was 88% and 70% at 5 and 10 years, respectively. The rate of freedom from valve-related reoperations was 79% and 63% at 5 and 10 years, respectively. Pulmonary autografts demonstrated good durability with low mortality. The Ross/Ross-Konno procedure is a good option that can be performed safely in pediatric patients with aortic valve disease, even in a small-volume center.
13. Changes on the ice plain of Ice Stream B and Ross Ice Shelf
Science.gov (United States)
Shabtaie, Sion
1993-01-01
During the 1970's and 1980's, nearly 200 stations from which accurate, three dimensional position fixes have been obtained from TRANSIT satellites were occupied throughout the Ross Ice Shelf. We have transformed the elevations obtained by satellite altimetry to the same geodetic datum, and then applied a second transformation to reduce the geodetic heights to elevations above mean sea level using the GEM-10C geoidal height. On the IGY Ross Ice Shelf traverse between Oct. 1957 and Feb. 1958, an accurate method of barometric altimetry was used on a loop around the ice shelf that was directly tied to the sea at both ends of the travel route, thus providing absolute elevations. Comparisons of the two sets of data at 32 station pairs on floating ice show a mean difference of 0 +/- 1 m. The elevation data were also compared with theoretical values of elevations for a hydrostatically floating ice shelf. The mean difference between theoretical and measured values of elevations is -2 +/- 1 m.
14. ROSS Skills, Knowledge, and Abilities Training Evaluation. Gaps and Recommendations
Energy Technology Data Exchange (ETDEWEB)
Ala, Maureen [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gruidl, Jeremiah [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Buddemeier, Brooke [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-09-30
This document describes the development of the ROSS SKAs, the cross-mapping of the SKAs to the available training, identifies gaps in the SKA and training, and provides recommendations to address those gaps.
15. Minevikupärandit Häädemeestelt / Eevi Ross
Index Scriptorium Estoniae
Ross, Eevi, 1938-
2012-01-01
Raamatututvustus: Minevikupärandit Häädemeestelt : valimik korrespondentide murdetekste. VIII / Eesti Teaduste Akadeemia Emakeele Selts ; kogunud Marta Mäesalu ; koostanud ja toimetanud: Helju Kaal, Eevi Ross. Tallinn : Emakeele Selts, 2012
16. Ross Ice Drainage System (RIDS) Glaciochemical Analysis, Version 1
Data.gov (United States)
National Aeronautics and Space Administration — The Ross Ice Drainage System (RIDS) project provides a high-resolution record of atmospheric chemical deposition taken from several ice cores and snow pits located...
17. DVD Review: "The Silver Fez" Directed by Lloyd Ross (2009 ...
African Journals Online (AJOL)
Abstract. Producer: Lloyd Ross, Joelle Chesselet. Sound design: Warrick Sony. Cast: Abubakar Davids, Mogamat Zain Benjamin. Approx. 87 min. Distributor: IRIS. ZAR 129.99. Journal of the Musical Arts in Africa, Volume 9 2012, 89–91 ...
18. The Ross II procedure: pulmonary autograft in the mitral position.
Science.gov (United States)
Athanasiou, Thanos; Cherian, Ashok; Ross, Donald
2004-10-01
The surgical management of mitral valve disease in women of childbearing age, young patients, and children with congenital mitral valve defects is made difficult by the prospect of lifelong anticoagulation. We suggest the use of a pulmonary autograft in the mitral position (Ross II procedure) as an alternative surgical technique. We present a review of the literature, historical perspectives, indications, selection criteria, and surgical technique for the Ross II procedure. Our literature search identified 14 studies that reported results from the Ross II operation. Performed in 103 patients, the overall in-hospital mortality was 7 (6.7%), with a late mortality of 10 (9%). Although further research is needed, current evidence suggests the Ross II operation is a valuable alternative in low-risk young patients where valve durability and the complication rate from other procedures is unsatisfactory and anticoagulation not ideal.
19. Ocean modelling aspects for drift applications
Science.gov (United States)
Stephane, L.; Pierre, D.
2010-12-01
Nowadays, many authorities in charge of rescue-at-sea operations lean on operational oceanography products to outline research perimeters. Moreover, current fields estimated with sophisticated ocean forecasting systems can be used as input data for oil spill/ adrift object fate models. This emphasises the necessity of an accurate sea state forecast, with a mastered level of reliability. This work focuses on several problems inherent to drift modeling, dealing in the first place with the efficiency of the oceanic current field representation. As we want to discriminate the relevance of a particular physical process or modeling option, the idea is to generate series of current fields of different characteristics and then qualify them in term of drift prediction efficiency. Benchmarked drift scenarios were set up from real surface drifters data, collected in the Mediterranean sea and off the coasts of Angola. The time and space scales that we are interested in are about 72 hr forecasts (typical timescale communicated in case of crisis), for distance errors that we hope about a few dozen of km around the forecast (acceptable for reconnaissance by aircrafts) For the ocean prediction, we used some regional oceanic configurations based on the NEMO 2.3 code, nested into Mercator 1/12° operational system. Drift forecasts were computed offline with Mothy (Météo France oil spill modeling system) and Ariane (B. Blanke, 1997), a Lagrangian diagnostic tool. We were particularly interested in the importance of the horizontal resolution, vertical mixing schemes, and any processes that may impact the surface layer. The aim of the study is to ultimately point at the most suitable set of parameters for drift forecast use inside operational oceanic systems. We are also motivated in assessing the relevancy of ensemble forecasts regarding determinist predictions. Several tests showed that mis-described observed trajectories can finally be modelled statistically by using uncertainties
20. Tapping with intentional drift
NARCIS (Netherlands)
Vardy, A.N.; Daffertshofer, A.; Beek, P.J.
2009-01-01
When tapping a desired frequency, subjects tend to drift away from this target frequency. This compromises the estimate of the correlation between inter-tap intervals (ITIs) as predicted by the two-level model of Wing and Kristofferson which consists of an internal timer ('clock') and motor delays.
1. The KLOE drift chamber
International Nuclear Information System (INIS)
Ferrari, A.
2002-01-01
The design and construction of the large drift chamber of the KLOE experiment is presented. The track reconstruction is described, together with the calibration method and the monitoring systems. The stability of operation and the performance are studied with samples of e + e - , K S K L and K + K - events
2. High resolution drift chambers
International Nuclear Information System (INIS)
Va'vra, J.
1985-07-01
High precision drift chambers capable of achieving less than or equal to 50 μm resolutions are discussed. In particular, we compare so called cool and hot gases, various charge collection geometries, several timing techniques and we also discuss some systematic problems. We also present what we would consider an ''ultimate'' design of the vertex chamber. 50 refs., 36 figs., 6 tabs
3. Argus drift chamber
Energy Technology Data Exchange (ETDEWEB)
Danilov, M; Nagovizin, V; Hasemann, H; Michel, E; Schmidt-Parzefall, W; Wurth, R; Kim, P
1983-11-15
The ARGUS detector came into operation at the DORIS-II e/sup +/s/sup -/ storage ring at the end of 1982. Its two meter long drift chamber contains 5940 sense and 24588 field wires organized in uniform 18x18.8 mm/sup 2/ drift cells filling the whole volume. These cells form 36 layers, 18 of which provide stereo views. Each sense wire is equipped with a single hit TDC and ADC for coordinate and dE/dx measurements. The chamber is operated with propane to improve momentum and dE/dx resolution. The drift chamber design and initial performance are presented. With a very crude space-time relation approximation and without all the necessary corrections applied a spatial resolution of about 200 ..mu..m was obtained for half of the drift cell volume. Further corrections should improve this result. An intrinsic dE/dx resolution of 4.2% and an actual resolution of 5% were obtained for cosmic muons and also for Bhabha scattered electrons. An actual dE/dx resolution of 5.6% was obtained for pions from e/sup +/e/sup -/ annihilation data with almost no track selection. A relativistic rise of 30% was observed in good agreement with theory. The long-term stability is still to be investigated.
4. Inland drift sand landscapes
NARCIS (Netherlands)
Fanta, J.; Siepel, H.
2010-01-01
Man has had a complex relationship with inland drift sands through the ages. For some centuries these landscapes were seen as a threat to society, especially agriculture and housing. At present we conserve these landscapes as important Natura 2000 priority habitats. In this book you may find these
5. Guiding center drift equations
International Nuclear Information System (INIS)
Boozer, A.H.
1979-03-01
The quations for particle guiding center drift orbits are given in a new magnetic coordinate system. This form of the equations not only separates the fast motion along the lines from the slow motion across, but also requires less information about the magnetic field than many other formulations of the problem
6. IN DRIFT CORROSION PRODUCTS
Energy Technology Data Exchange (ETDEWEB)
D.M. Jolley
1999-12-02
As directed by a written development plan (CRWMS M&O 1999a), a conceptual model for steel and corrosion products in the engineered barrier system (EBS) is to be developed. The purpose of this conceptual model is to assist Performance Assessment Operations (PAO) and its Engineered Barrier Performance Department in modeling the geochemical environment within a repository drift, thus allowing PAO to provide a more detailed and complete in-drift geochemical model abstraction and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near-Field Environment (NFE) Revision 2 (NRC 1999). This document provides the conceptual framework for the in-drift corrosion products sub-model to be used in subsequent PAO analyses including the EBS physical and chemical model abstraction effort. This model has been developed to serve as a basis for the in-drift geochemical analyses performed by PAO. However, the concepts discussed within this report may also apply to some near and far-field geochemical processes and may have conceptual application within the unsaturated zone (UZ) and saturated zone (SZ) transport modeling efforts.
7. STS-74 M.S. Jerry L. Ross suits up
Science.gov (United States)
1995-01-01
Spaceflight veteran Jerry L. Ross, Mission Specialist 2 on Shuttle Mission STS-74, is assisted by a suit technician as he finishes getting into his launch/entry suit in the Operations and Checkout Building. Ross and four fellow astronauts will depart shortly for Launch Pad 39A, where the Space Shuttle Atlantis awaits a second liftoff attempt during a seven-minute window scheduled to open at approximately 7:30 a.m. EST, Nov. 12.
8. Remote sensing of sea ice: advances during the DAMOCLES project
Directory of Open Access Journals (Sweden)
G. Heygster
2012-12-01
Full Text Available In the Arctic, global warming is particularly pronounced so that we need to monitor its development continuously. On the other hand, the vast and hostile conditions make in situ observation difficult, so that available satellite observations should be exploited in the best possible way to extract geophysical information. Here, we give a résumé of the sea ice remote sensing efforts of the European Union's (EU project DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies. In order to better understand the seasonal variation of the microwave emission of sea ice observed from space, the monthly variations of the microwave emissivity of first-year and multi-year sea ice have been derived for the frequencies of the microwave imagers like AMSR-E (Advanced Microwave Scanning Radiometer on EOS and sounding frequencies of AMSU (Advanced Microwave Sounding Unit, and have been used to develop an optimal estimation method to retrieve sea ice and atmospheric parameters simultaneously. In addition, a sea ice microwave emissivity model has been used together with a thermodynamic model to establish relations between the emissivities from 6 GHz to 50 GHz. At the latter frequency, the emissivity is needed for assimilation into atmospheric circulation models, but is more difficult to observe directly. The size of the snow grains on top of the sea ice influences both its albedo and the microwave emission. A method to determine the effective size of the snow grains from observations in the visible range (MODIS is developed and demonstrated in an application on the Ross ice shelf. The bidirectional reflectivity distribution function (BRDF of snow, which is an essential input parameter to the retrieval, has been measured in situ on Svalbard during the DAMOCLES campaign, and a BRDF model assuming aspherical particles is developed. Sea ice drift and deformation is derived from satellite observations with the scatterometer
9. Dike Propagation Near Drifts
International Nuclear Information System (INIS)
2002-01-01
The purpose of this Analysis and Model Report (AMR) supporting the Site Recommendation/License Application (SR/LA) for the Yucca Mountain Project is the development of elementary analyses of the interactions of a hypothetical dike with a repository drift (i.e., tunnel) and with the drift contents at the potential Yucca Mountain repository. This effort is intended to support the analysis of disruptive events for Total System Performance Assessment (TSPA). This AMR supports the Process Model Report (PMR) on disruptive events (CRWMS M and O 2000a). This purpose is documented in the development plan (DP) ''Coordinate Modeling of Dike Propagation Near Drifts Consequences for TSPA-SR/LA'' (CRWMS M and O 2000b). Evaluation of that Development Plan and the work to be conducted to prepare Interim Change Notice (ICN) 1 of this report, which now includes the design option of ''Open'' drifts, indicated that no revision to that DP was needed. These analyses are intended to provide reasonable bounds for a number of expected effects: (1) Temperature changes to the waste package from exposure to magma; (2) The gas flow available to degrade waste containers during the intrusion; (3) Movement of the waste package as it is displaced by the gas, pyroclasts and magma from the intruding dike (the number of packages damaged); (4) Movement of the backfill (Backfill is treated here as a design option); (5) The nature of the mechanics of the dike/drift interaction. These analyses serve two objectives: to provide preliminary analyses needed to support evaluation of the consequences of an intrusive event and to provide a basis for addressing some of the concerns of the Nuclear Regulatory Commission (NRC) expressed in the Igneous Activity Issue Resolution Status Report
10. Duality of Ross Ice Shelf systems: crustal boundary, ice sheet processes and ocean circulation from ROSETTA-Ice surveys
Science.gov (United States)
Tinto, K. J.; Siddoway, C. S.; Padman, L.; Fricker, H. A.; Das, I.; Porter, D. F.; Springer, S. R.; Siegfried, M. R.; Caratori Tontini, F.; Bell, R. E.
2017-12-01
Bathymetry beneath Antarctic ice shelves controls sub-ice-shelf ocean circulation and has a major influence on the stability and dynamics of the ice sheets. Beneath the Ross Ice Shelf, the sea-floor bathymetry is a product of both tectonics and glacial processes, and is influenced by the processes it controls. New aerogeophysical surveys have revealed a fundamental crustal boundary bisecting the Ross Ice Shelf and imparting a duality to the Ross Ice Shelf systems, encompassing bathymetry, ocean circulation and ice flow history. The ROSETTA-Ice surveys were designed to increase the resolution of Ross Ice Shelf mapping from the 55 km RIGGS survey of the 1970s to a 10 km survey grid, flown over three years from New York Air National Guard LC130s. Radar, LiDAR, gravity and magnetic instruments provide a top to bottom profile of the ice shelf and the underlying seafloor, with 20 km resolution achieved in the first two survey seasons (2015 and 2016). ALAMO ocean-profiling floats deployed in the 2016 season are measuring the temperature and salinity of water entering and exiting the sub-ice water cavity. A significant east-west contrast in the character of the magnetic and gravity fields reveals that the lithospheric boundary between East and West Antarctica exists not at the base of the Transantarctic Mountains (TAM), as previously thought, but 300 km further east. The newly-identified boundary spatially coincides with the southward extension of the Central High, a rib of shallow basement identified in the Ross Sea. The East Antarctic side is characterized by lower amplitude magnetic anomalies and denser TAM-type lithosphere compared to the West Antarctic side. The crustal structure imparts a fundamental duality on the overlying ice and ocean, with deeper bathymetry and thinner ice on the East Antarctic side creating a larger sub-ice cavity for ocean circulation. The West Antarctic side has a shallower seabed, more restricted ocean access and a more complex history of
11. Dynamics of the Ross-Stirling engine
Energy Technology Data Exchange (ETDEWEB)
Doige, A G; Walker, G
1986-01-01
A computer model has been developed for the simulation of the dynamic loading in a Stirling engine having a Ross linkage as the drive mechanism. The model is based on a complete theoretical formulation of the dynamics of the system. The masses and moments of inertia of all moving components have been included in the model. The computer program can be used for determining the effect of changes in many design parameters on the geometry, velocities, accelerations, dynamic loading and reactions at all pin connections and engine-mount locations. In this paper, emphasis is given to assessing the general characteristics of the reaction forces at the pin connections and to the reduction of overall engine shaking forces by simple balancing methods. The most heavily loaded element in the engine is the pin connecting the crank and the yoke. The force at that location is a combination of a static load produced by gas pressure in the cylinders and a combined inertia load for the whole engine which increases with the square of the rotational speed. 6 refs., 12 figs., 2 tabs.
12. Style drift in private equity
NARCIS (Netherlands)
Cumming, D.; Fleming, G.; Schwienbacher, A.
2009-01-01
We introduce the concept of style drift to private equity investment. We present theory and evidence pertaining to style drifts in terms of a fund manager's stated focus on particular stages of entrepreneurial development. We develop a model that derives conditions under which style drifts are less
13. Diogene pictorial drift chamber
International Nuclear Information System (INIS)
Gosset, J.
1984-01-01
A pictorial drift chamber, called DIOGENE, has been installed at Saturne in order to study central collisions of high energy heavy ions. It has been adapted from the JADE internal detector, with two major differences to be taken into account. First, the center-of-mass of these collisions is not identical to the laboratory reference frame. Second, the energy loss and the momentum ranges of the particles to be detected are different from the ones in JADE. It was also tried to keep the cost as small as possible, hence the choice of minimum size and minimum number of sensitive wires. Moreover the wire planes are shifted from the beam axis: this trick helps very much to quickly reject the bad tracks caused by the ambiguity of measuring drift distances (positive or negative) through times (always positive)
14. Drift-Diffusion Equation
Directory of Open Access Journals (Sweden)
K. Banoo
1998-01-01
equation in the discrete momentum space. This is shown to be similar to the conventional drift-diffusion equation except that it is a more rigorous solution to the Boltzmann equation because the current and carrier densities are resolved into M×1 vectors, where M is the number of modes in the discrete momentum space. The mobility and diffusion coefficient become M×M matrices which connect the M momentum space modes. This approach is demonstrated by simulating electron transport in bulk silicon.
15. Negative Drift in Populations
DEFF Research Database (Denmark)
Lehre, Per Kristian
2011-01-01
An important step in gaining a better understanding of the stochastic dynamics of evolving populations, is the development of appropriate analytical tools. We present a new drift theorem for populations that allows properties of their long-term behaviour, e.g. the runtime of evolutionary algorithms......, to be derived from simple conditions on the one-step behaviour of their variation operators and selection mechanisms....
16. Consistent guiding center drift theories
International Nuclear Information System (INIS)
Wimmel, H.K.
1982-04-01
Various guiding-center drift theories are presented that are optimized in respect of consistency. They satisfy exact energy conservation theorems (in time-independent fields), Liouville's theorems, and appropriate power balance equations. A theoretical framework is given that allows direct and exact derivation of associated drift-kinetic equations from the respective guiding-center drift-orbit theories. These drift-kinetic equations are listed. Northrop's non-optimized theory is discussed for reference, and internal consistency relations of G.C. drift theories are presented. (orig.)
17. Laboratory Course on Drift Chambers
International Nuclear Information System (INIS)
Garcia-Ferreira, Ix-B.; Garcia-Herrera, J.; Villasenor, L.
2006-01-01
Drift chambers play an important role in particle physics experiments as tracking detectors. We started this laboratory course with a brief review of the theoretical background and then moved on to the the experimental setup which consisted of a single-sided, single-cell drift chamber. We also used a plastic scintillator paddle, standard P-10 gas mixture (90% Ar, 10% CH4) and a collimated 90Sr source. During the laboratory session the students performend measurements of the following quantities: a) drift velocities and their variations as function of the drift field; b) gas gains and c) diffusion of electrons as they drifted in the gas
18. Rapid Holocene thinning of outlet glaciers followed by readvance in the western Ross Embayment, Antarctica
Science.gov (United States)
Jones, R. S.; Whitmore, R.; Mackintosh, A.; Norton, K. P.; Eaves, S.; Stutz, J.
2017-12-01
Investigating Antarctic deglaciation following the LGM provides an opportunity to better understand patterns, mechanisms and drivers of ice sheet retreat. In the Ross Sea sector, geomorphic features preserved on the seafloor indicate that streaming East Antarctic outlet glaciers once extended >100 km offshore of South Victoria Land prior to back-stepping towards their modern configurations. In order to adequately interpret the style and causes of this retreat, the timing and magnitude of corresponding ice thickness change is required. We present new constraints on ice surface lowering from Mawson Glacier, an outlet of the East Antarctic Ice Sheet that flows into the western Ross Sea. Surface-exposure (10Be) ages from samples collected in elevation transects above the modern ice surface reveal that rapid thinning occurred at 5-8 ka, broadly coeval with new ages of grounding-line retreat at 6 ka and rapid thinning recorded at nearby Mackay Glacier at 7 ka. Our data also show that a moraine formed near to the modern ice margin of Mawson Glacier at 0.8 ka, which, together with historical observations, indicates that glaciers in this region readvanced during the last thousand years. We argue that 1) the accelerated thinning of outlet glaciers was driven by local grounding-line retreat through overdeepened basins during the early-mid Holocene, and 2) the glaciers subsequently readvanced, possibly linked to late Holocene sea-ice expansion, before retreating to their current positions. Our work demonstrates that these outlet glaciers were closely coupled to environmental and topography-induced perturbations near their termini throughout the Holocene.
19. Adaptive Online Sequential ELM for Concept Drift Tackling
Directory of Open Access Journals (Sweden)
Arif Budiman
2016-01-01
Full Text Available A machine learning method needs to adapt to over time changes in the environment. Such changes are known as concept drift. In this paper, we propose concept drift tackling method as an enhancement of Online Sequential Extreme Learning Machine (OS-ELM and Constructive Enhancement OS-ELM (CEOS-ELM by adding adaptive capability for classification and regression problem. The scheme is named as adaptive OS-ELM (AOS-ELM. It is a single classifier scheme that works well to handle real drift, virtual drift, and hybrid drift. The AOS-ELM also works well for sudden drift and recurrent context change type. The scheme is a simple unified method implemented in simple lines of code. We evaluated AOS-ELM on regression and classification problem by using concept drift public data set (SEA and STAGGER and other public data sets such as MNIST, USPS, and IDS. Experiments show that our method gives higher kappa value compared to the multiclassifier ELM ensemble. Even though AOS-ELM in practice does not need hidden nodes increase, we address some issues related to the increasing of the hidden nodes such as error condition and rank values. We propose taking the rank of the pseudoinverse matrix as an indicator parameter to detect “underfitting” condition.
20. Radiological Operations Support Specialist (ROSS) Pilot Course Summary and Recommendations
Energy Technology Data Exchange (ETDEWEB)
Alai, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Askin, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Buddemeier, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wogan, L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Doshi, P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tai, L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-09-30
1. Radiological Operations Support Specialist (ROSS) Pilot Course Summary and Recommendations
International Nuclear Information System (INIS)
Alai, M.; Askin, A.; Buddemeier, B.; Wogan, L.; Doshi, P.; Tai, L.
2016-01-01
2. Does the Homograft for RVOT Reconstruction in Ross: Patients Fare Better than for Non-Ross Patients? A Single-Center Experience.
Science.gov (United States)
Ruzmetov, Mark; Geiss, Dale M; Shah, Jitendra J; Fortuna, Randall S; Welke, Karl F
2015-07-01
In patients undergoing the Ross procedure, the right ventricular outflow tract (RVOT) conduit is inserted in an orthotopic position rather than in the more heterotopic position used in the repair of complex congenital RVOT obstruction. The study aim was to compare the authors' institutional mid-term experience of large-sized homografts (>19 mm) in patients with Ross and non-Ross RVOT reconstructions. The outcome was reviewed of all homografts implanted for Ross (n = 72) or non-Ross (n = 64) RVOT reconstruction at a single center between 1993 and 2012. Echocardiographic data were reviewed to evaluate valve performance. Homograft dysfunction was defined as RVOT obstruction with peak echo-Doppler gradient >40 mmHg and/or grade >III/IV conduit valve regurgitation. Homograft failure was defined as the need for conduit replacement or catheter or surgical reintervention. The age, body weight, conduit diameter and previous surgery were significantly higher in patients with Ross compared to the non-Ross group (p = 0.002, 0.003 and Ross, n = 17; non-Ross, n = 18). The data acquired showed actuarial survival, freedom from conduit dysfunction and conduit failure to be similar in both cohorts. Freedom from any type of reoperation was worse for the Ross group (58%) than for the non-Ross group (72%) (p = 0.05). During the first 15 years after Ross or non-Ross pulmonary homograft implantation, the survival rate, freedom from failure and dysfunction, and RVOT gradient were statistically similar. Freedom from any type of reoperation was significantly higher in the non-Ross group, however.
3. Multi-Decadal Averages of Basal Melt for Ross Ice Shelf, Antarctica Using Airborne Observations
Science.gov (United States)
Das, I.; Bell, R. E.; Tinto, K. J.; Frearson, N.; Kingslake, J.; Padman, L.; Siddoway, C. S.; Fricker, H. A.
2017-12-01
Changes in ice shelf mass balance are key to the long term stability of the Antarctic Ice Sheet. Although the most extensive ice shelf mass loss currently is occurring in the Amundsen Sea sector of West Antarctica, many other ice shelves experience changes in thickness on time scales from annual to ice age cycles. Here, we focus on the Ross Ice Shelf. An 18-year record (1994-2012) of satellite radar altimetry shows substantial variability in Ross Ice Shelf height on interannual time scales, complicating detection of potential long-term climate-change signals in the mass budget of this ice shelf. Variability of radar signal penetration into the ice-shelf surface snow and firn layers further complicates assessment of mass changes. We investigate Ross Ice Shelf mass balance using aerogeophysical data from the ROSETTA-Ice surveys using IcePod. We use two ice-penetrating radars; a 2 GHz unit that images fine-structure in the upper 400 m of the ice surface and a 360 MHz radar to identify the ice shelf base. We have identified internal layers that are continuous along flow from the grounding line to the ice shelf front. Based on layer continuity, we conclude that these layers must be the horizons between the continental ice of the outlet glaciers and snow accumulation once the ice is afloat. We use the Lagrangian change in thickness of these layers, after correcting for strain rates derived using modern day InSAR velocities, to estimate multidecadal averaged basal melt rates. This method provides a novel way to quantify basal melt, avoiding the confounding impacts of spatial and short-timescale variability in surface accumulation and firn densification processes. Our estimates show elevated basal melt rates (> -1m/yr) around Byrd and Mullock glaciers within 100 km from the ice shelf front. We also compare modern InSAR velocity derived strain rates with estimates from the comprehensive ground-based RIGGS observations during 1973-1978 to estimate the potential magnitude of
4. Antarctic sea ice increase consistent with intrinsic variability of the Amundsen Sea Low
Science.gov (United States)
Turner, John; Hosking, J. Scott; Marshall, Gareth J.; Phillips, Tony; Bracegirdle, Thomas J.
2016-04-01
We investigate the relationship between atmospheric circulation variability and the recent trends in Antarctic sea ice extent (SIE) using Coupled Model Intercomparison Project Phase 5 (CMIP5) atmospheric data, ECMWF Interim reanalysis fields and passive microwave satellite data processed with the Bootstrap version 2 algorithm. Over 1979-2013 the annual mean total Antarctic SIE increased at a rate of 195 × 103 km2 dec-1 (1.6 % dec-1), p 4.0 % dec-1) has been in the Ross Sea sector. Off West Antarctica there is a high correlation between trends in SIE and trends in the near-surface winds. The Ross Sea SIE seasonal trends are positive throughout the year, but largest in spring. The stronger meridional flow over the Ross Sea has been driven by a deepening of the Amundsen Sea Low (ASL). Pre-industrial control and historical simulations from CMIP5 indicate that the observed deepening of the ASL and stronger southerly flow over the Ross Sea are within the bounds of modeled intrinsic variability. The spring trend would need to continue for another 11 years for it to fall outside the 2 standard deviation range seen in 90 % of the simulations.
5. Drifting black aurorae?
International Nuclear Information System (INIS)
Schoute-Vanneck, H.; Scourfield, M.W.J.; Nielsen, E.
1990-01-01
Characteristics of eastward drifting forms, previously described in the literature as black aurorae, have been identified in low-light level TV camera data. The TV field of view was within the field of view of STARE and that of an all-sky camera. On the basis of these observations the authors propose that these auroral forms are a manifestation of folds or waves on the borders of auroral bands propagating along the dark regions between neighboring auroral bands. Conditions under which the folds or waves occur are compatible with their formation by the Kelvin-Helmholtz electrostatic instability
6. ABSTRACTION OF DRIFT SEEPAGE
International Nuclear Information System (INIS)
Wilson, Michael L.
2001-01-01
Drift seepage refers to flow of liquid water into repository emplacement drifts, where it can potentially contribute to degradation of the engineered systems and release and transport of radionuclides within the drifts. Because of these important effects, seepage into emplacement drifts is listed as a ''principal factor for the postclosure safety case'' in the screening criteria for grading of data in Attachment 1 of AP-3.15Q, Rev. 2, ''Managing Technical Product Inputs''. Abstraction refers to distillation of the essential components of a process model into a form suitable for use in total-system performance assessment (TSPA). Thus, the purpose of this analysis/model is to put the information generated by the seepage process modeling in a form appropriate for use in the TSPA for the Site Recommendation. This report also supports the Unsaturated-Zone Flow and Transport Process Model Report. The scope of the work is discussed below. This analysis/model is governed by the ''Technical Work Plan for Unsaturated Zone Flow and Transport Process Model Report'' (CRWMS MandO 2000a). Details of this activity are in Addendum A of the technical work plan. The original Work Direction and Planning Document is included as Attachment 7 of Addendum A. Note that the Work Direction and Planning Document contains tasks identified for both Performance Assessment Operations (PAO) and Natural Environment Program Operations (NEPO). Only the PAO tasks are documented here. The planning for the NEPO activities is now in Addendum D of the same technical work plan and the work is documented in a separate report (CRWMS MandO 2000b). The Project has been reorganized since the document was written. The responsible organizations in the new structure are the Performance Assessment Department and the Unsaturated Zone Department, respectively. The work plan for the seepage abstraction calls for determining an appropriate abstraction methodology, determining uncertainties in seepage, and providing
7. Drift velocity monitoring of the CMS muon drift chambers
CERN Document Server
Sonnenschein, Lars
2010-01-01
The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented.
8. Rossing - uranium changes the face of the Namib
International Nuclear Information System (INIS)
Anon.
1981-01-01
Rossing is not only an important source of uranium for industrial countries, but a large revenue-earner. It is injecting money into the economy. For efficiency, personnel and equipment had to be comfortably established. The Rossing orebody is the largest known deposit of uranium occuring in granite. Over one million ton of ore and waste are removed weekly. By the use of scintillometer readings the ore is blended to give a constant feed to the mill. Modern developments are used to optimise the mining operation. Radioactivity will be always present and is therefore regulary measured. The best working environment are always ensured
9. The CLEO III drift chamber
CERN Document Server
Peterson, D; Briere, R A; Chen, G; Cronin-Hennessy, D; Csorna, S; Dickson, M; Dombrowski, S V; Ecklund, K M; Lyon, A; Marka, S; Meyer, T O; Patterson, J R; Sadoff, A; Thies, P; Thorndike, E H; Urner, D
2002-01-01
The CLEO group at the Cornell Electron Storage Ring has constructed and commissioned a new central drift chamber. With 9796 cells arranged in 47 layers ranging in radius from 13.2 to 79 cm, the new drift chamber has a smaller outer radius and fewer wires than the drift chamber it replaces, but allows the CLEO tracking system to have improved momentum resolution. Reduced scattering material in the chamber gas and in the inner skin separating the drift chamber from the silicon vertex detector provides a reduction of the multiple scattering component of the momentum resolution and an extension of the usable measurement length into the silicon. Momentum resolution is further improved through quality control in wire positioning and symmetry of the electric fields in the drift cells which have provided a reduction in the spatial resolution to 88 mu m (averaged over the full drift range).
10. Electronics for proportional drift tubes
International Nuclear Information System (INIS)
Fremont, G.; Friend, B.; Mess, K.H.; Schmidt-Parzefall, W.; Tarle, J.C.; Verweij, H.; CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration); Geske, K.; Riege, H.; Schuett, J.; CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration); Semenov, Y.; CERN-Hamburg-Amsterdam-Rome-Moscow Collaboration)
1980-01-01
An electronic system for the read-out of a large number of proportional drift tubes (16,000) has been designed. This system measures deposited charge and drift-time of the charge of a particle traversing a proportional drift tube. A second event can be accepted during the read-out of the system. Up to 40 typical events can be collected and buffered before a data transfer to a computer is necessary. (orig.)
International Nuclear Information System (INIS)
Houseworth, J.
2004-01-01
The purpose of this model report is to document the drift scale radionuclide transport model, taking into account the effects of emplacement drifts on flow and transport in the vicinity of the drift, which are not captured in the mountain-scale unsaturated zone (UZ) flow and transport models ''UZ Flow Models and Submodels'' (BSC 2004 [DIRS 169861]), ''Radionuclide Transport Models Under Ambient Conditions'' (BSC 2004 [DIRS 164500]), and ''Particle Tracking Model and Abstraction of Transport Process'' (BSC 2004 [DIRS 170041]). The drift scale radionuclide transport model is intended to be used as an alternative model for comparison with the engineered barrier system (EBS) radionuclide transport model ''EBS Radionuclide Transport Abstraction'' (BSC 2004 [DIRS 169868]). For that purpose, two alternative models have been developed for drift-scale radionuclide transport. One of the alternative models is a dual continuum flow and transport model called the drift shadow model. The effects of variations in the flow field and fracture-matrix interaction in the vicinity of a waste emplacement drift are investigated through sensitivity studies using the drift shadow model (Houseworth et al. 2003 [DIRS 164394]). In this model, the flow is significantly perturbed (reduced) beneath the waste emplacement drifts. However, comparisons of transport in this perturbed flow field with transport in an unperturbed flow field show similar results if the transport is initiated in the rock matrix. This has led to a second alternative model, called the fracture-matrix partitioning model, that focuses on the partitioning of radionuclide transport between the fractures and matrix upon exiting the waste emplacement drift. The fracture-matrix partitioning model computes the partitioning, between fractures and matrix, of diffusive radionuclide transport from the invert (for drifts without seepage) into the rock water. The invert is the structure constructed in a drift to provide the floor of the
12. 75 FR 32802 - Certificate of Alternative Compliance for the Offshore Supply Vessel ROSS CANDIES
Science.gov (United States)
2010-06-09
... Compliance for the Offshore Supply Vessel ROSS CANDIES AGENCY: Coast Guard, DHS. ACTION: Notice. SUMMARY: The... vessel ROSS CANDIES as required by 33 U.S.C. 1605(c) and 33 CFR 81.18. DATES: The Certificate of... the offshore supply vessel ROSS CANDIES, O.N. 1222260. Full compliance with 72 COLREGS [[Page 32803...
13. 77 FR 56859 - Federal Register Notification of Redesignation of Potential Wilderness as Wilderness, Ross Lake...
Science.gov (United States)
2012-09-14
... Register Notification of Redesignation of Potential Wilderness as Wilderness, Ross Lake National Recreation..., Ross Lake National Recreation Area, and Lake Chelan National Recreation Area as the Stephen Mather... acres of potential wilderness within Ross Lake National Recreation Area, including approximately 1,667...
14. Setting the scientistic cat among the humanist pigeons Don Ross ...
African Journals Online (AJOL)
implications of cognitive science and economics for each other. Ross makes neoclassical economics central to the unification of the behavioural sciences, and defends its fundamental health against its critics. He locates the source of the empirical and conceptual problems besetting neoclassical economics in the mistaken ...
15. R. E. van der Ross (1921–2017)
African Journals Online (AJOL)
19 Mrt. 2018 ... Sedert sy jeug het Richard Ernest van der Ross. (1921–2017) 'n belangrike rol in die breë Kaapse ge- meenskap gespeel. Hy het hom onderskei as 'n anti- apartheidsaktivis, 'n opvoedkundige, 'n geskied- skrywer en openbare intellektueel, 'n vakbondmens,. 'n gemeenskapsbouer, 'n maatskappydirekteur ...
16. Ross Ice Shelf and the Queen Maude Mounains, Antarctica
Science.gov (United States)
1991-01-01
Part of the Ross Ice Shelf and the Queen Maude Mounains of Antarctica (55.5N, 178.0W) are in the background of this scene, oriented toward the south. Low stratocumulus clouds are predominant throughout most of the scene.
17. A Hydrographic Survey of the Scotia Sea, 15 March 1999 to 22 April 1999 (NODC Accession 0000861)
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — CTD and chemical data were collected using CTD and bottle casts in the Drake Passage and Scotia Sea from the JAMES CLARK ROSS. Data were collected from 15 March 1999...
18. Outcomes of Reintervention on the Autograft After Ross Procedure.
Science.gov (United States)
Kumar, S Ram; Bansal, Neeraj; Wells, Winfield J; Starnes, Vaughn A
2016-11-01
After a Ross procedure, a small subset of patients requires reintervention for autograft dilatation or valve insufficiency. We sought to determine the indications, nature, and outcomes of autograft reinterventions in the left ventricular outflow tract after a Ross procedure. We retrospectively reviewed the charts of 316 consecutive patients, age 4 days to 70 years, who underwent a Ross procedure at our institution. Of these, 47 patients (15%) required autograft reintervention during a median follow-up of 8.2 years. Forty-seven patients, median age 26 years (interquartile range [IQR], 14.4 to 44.8 years), 32 (68%) men, required autograft reintervention a median 5.5 years (IQR, 1.8 to 9.4 years) after a Ross procedure. In 47% (22 of 47 patients), the autograft valve could be salvaged (15 valve-sparing aortic replacements, 7 valve repairs). The remaining 53% underwent replacement of the root (10 mechanical, 5 homograft) or valve alone (7 mechanical, 3 bioprosthetic). Twenty patients presented without autograft root dilatation 1 year (IQR, 0.5 to 2.9 years) after Ross. Fifteen of them (75%) required valve replacement. The 27 patients who demonstrated root dilatation presented 6.9 years (IQR, 4.5 to 9.7 years; p Ross, and 17 (63%) of these valves could be spared (p = 0.01). There was no surgical mortality and 5 (11%) major morbidity events. Patients were followed up for 4.9 years (IQR, 2.1 to 7 years) after left ventricular outflow tract reintervention. For patients whose autograft valve could be spared, 3-, 5-, and 8-year freedom from valve replacement was 92%, 86%, and 86%, respectively. At last follow-up, only 1 patient had greater than mild aortic insufficiency, and all but 1 had normal ejection fraction. Autograft reintervention after a Ross appears to follow a bimodal distribution. Patients with primary autograft leaflet problems tend to present early without root dilatation and frequently require valve replacement. The autograft valve can be salvaged in the
19. Progress in semiconductor drift detectors
International Nuclear Information System (INIS)
Rehak, P.; Walton, J.; Gatti, E.
1985-01-01
Progress in testing semiconductor drift detectors is reported. Generally better position and energy resolutions were obtained than resolutions published previously. The improvement is mostly due to new electronics better matched to different detectors. It is shown that semiconductor drift detectors are becoming versatile and reliable detectors for position and energy measurements
20. CTF Void Drift Validation Study
Energy Technology Data Exchange (ETDEWEB)
Salko, Robert K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gosdin, Chris [Pennsylvania State Univ., University Park, PA (United States); Avramova, Maria N. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Gergar, Marcus [Pennsylvania State Univ., University Park, PA (United States)
2015-10-26
This milestone report is a summary of work performed in support of expansion of the validation and verification (V&V) matrix for the thermal-hydraulic subchannel code, CTF. The focus of this study is on validating the void drift modeling capabilities of CTF and verifying the supporting models that impact the void drift phenomenon. CTF uses a simple turbulent-diffusion approximation to model lateral cross-flow due to turbulent mixing and void drift. The void drift component of the model is based on the Lahey and Moody model. The models are a function of two-phase mass, momentum, and energy distribution in the system; therefore, it is necessary to correctly model the ow distribution in rod bundle geometry as a first step to correctly calculating the void distribution due to void drift.
1. Alibaba's strategic drift
OpenAIRE
Kim, Young-Chan; Chen, Pi-Chi
2016-01-01
It is fundamental in both a theoretical and practical sense, to analyse the strategies of successful e-businesses who were formulated and operated alongside incumbent competitors. Thus, there have been an array of strategic arguments concerning the rapidly-burgeoning virtual powerhouse Alibaba, who amidst a sea of fortified competitors, found their ground to become one of the most prominent e-businesses of the decade. At the commencing stages, Alibaba lacked a specific strategic goal, aside f...
2. Drifting oscillations in axion monodromy
Energy Technology Data Exchange (ETDEWEB)
Flauger, Raphael [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); McAllister, Liam [Department of Physics, Cornell University, Ithaca, NY 14853 (United States); Silverstein, Eva [Stanford Institute for Theoretical Physics, Stanford University, Stanford, CA 94305 (United States); Westphal, Alexander, E-mail: [email protected], E-mail: [email protected], E-mail: [email protected], E-mail: [email protected] [Theory Group, Deutsches Elektronen-Synchrotron DESY, D-22603 Hamburg (Germany)
2017-10-01
We study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effects of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. We use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.
3. Drifting oscillations in axion monodromy
International Nuclear Information System (INIS)
Flauger, Raphael; Westphal, Alexander
2014-12-01
We study the pattern of oscillations in the primordial power spectrum in axion monodromy inflation, accounting for drifts in the oscillation period that can be important for comparing to cosmological data. In these models the potential energy has a monomial form over a super-Planckian field range, with superimposed modulations whose size is model-dependent. The amplitude and frequency of the modulations are set by the expectation values of moduli fields. We show that during the course of inflation, the diminishing energy density can induce slow adjustments of the moduli, changing the modulations. We provide templates capturing the effects of drifting moduli, as well as drifts arising in effective field theory models based on softly broken discrete shift symmetries, and we estimate the precision required to detect a drifting period. A non-drifting template suffices over a wide range of parameters, but for the highest frequencies of interest, or for sufficiently strong drift, it is necessary to include parameters characterizing the change in frequency over the e-folds visible in the CMB. We use these templates to perform a preliminary search for drifting oscillations in a part of the parameter space in the Planck nominal mission data.
4. Isad ja tütred, isad ja pojad / Jüri Ross, Kristine Ross, Fjodor Berman ...[jt.] ; üles kirjutanud Jaana Liigand
Index Scriptorium Estoniae
2011-01-01
Büroomaailma juht Jüri Ross ja turundusdirektor Kristine Ross, BLRT Grupi omanik Fjodor Berman ja BLRT Grupi tütarfirma Refonda tegevdirektor Mark Berman, Saaremaa Laevakompanii ja paljude firmade omanik Vjatšeslav Leedo ja Mosaiigi kohviku omanik Katrin Leedo ärist, juhtimisest ja omavahelistest suhetest
5. Drift chamber data readout system
International Nuclear Information System (INIS)
1980-01-01
An electronic system for processing drift chamber signals is described. The system consists of 4-channel fast amplifier-discriminators of low threshold, 16-channel time-expanders transforming 0.5 μs time intervals to 10 μs and a 9-bit time-to-digital converter (TDC) recording up to 16 expanded time intervals. If the average track multiplicity is small, TDC is capable to process signals from 4 time-expanders (i.e., 64 drift gaps). In order to record multiple tracks per drift gap discriminator outputs can be connected to a number of time-expander channels. The fast clear input enables the system to be cleared within 0.5 μs. Efficient readout from TDC is facilated by reading only those channels which contain non-zero data (9 bits - drift time; 6 bits - wire number)
6. Drift tubes of Linac 2
CERN Multimedia
Photographic Service
1977-01-01
Being redied for installation, those at the right are for tank 1, those on the left for tank 2. Contrary to Linac 1, which had drift-tubes supported on stems, here the tubes are suspended, for better mechanical stability.
7. Validation of Robotic Surgery Simulator (RoSS).
Science.gov (United States)
Kesavadas, Thenkurussi; Stegemann, Andrew; Sathyaseelan, Gughan; Chowriappa, Ashirwad; Srimathveeravalli, Govindarajan; Seixas-Mikelus, Stéfanie; Chandrasekhar, Rameella; Wilding, Gregory; Guru, Khurshid
2011-01-01
Recent growth of daVinci Robotic Surgical System as a minimally invasive surgery tool has led to a call for better training of future surgeons. In this paper, a new virtual reality simulator, called RoSS is presented. Initial results from two studies - face and content validity, are very encouraging. 90% of the cohort of expert robotic surgeons felt that the simulator was excellent or somewhat close to the touch and feel of the daVinci console. Content validity of the simulator received 90% approval in some cases. These studies demonstrate that RoSS has the potential of becoming an important training tool for the daVinci surgical robot.
8. The Externally Supported Ross Operation: Early Outcomes and Intermediate Follow-Up.
Science.gov (United States)
Jacobsen, Roni M; Earing, Michael G; Hill, Garick D; Barnes, Michael; Mitchell, Michael E; Woods, Ronald K; Tweddell, James S
2015-08-01
The externally supported Ross (supported Ross), consisting of a Dacron (DuPont, Wilmington, DE) graft to support the neoaortic root, has been used in adolescent and adult patients to prevent neoaortic dilatation. Outcomes after the supported Ross technique were compared with the Ross procedure using the standard aortic root replacement technique (standard Ross). This was a retrospective analysis of 36 adolescent and young adult patients who underwent the Ross procedure between 1992 and 2013. The outcomes of supported Ross procedures in 26 patients were compared with the Ross procedure in 10 patients. End points included survival, neoaortic root dilatation, development of neoaortic regurgitation, and the need for reintervention. The median age at operation was 14 years (range, 11 to 31 years), and indications for the operation were mixed lesions (47%), followed by aortic regurgitation (42%) and stenosis (11%). There were no early deaths. The mean follow-up was 2.2 years (range, 1 to 11 years). At the 1-year (p = 0.01) and 3-year (p Ross cohort had a smaller neoaortic root z-score. Neither cohort had a large number of patients with significant neoaortic regurgitation, with 1 patient in the supported cohort compared with 3 patients in the standard cohort. Overall, 4 patients (40%) in the standard Ross cohort had required reintervention, including 3 directed at the neoaortic root. One patient in the supported Ross cohort required early reintervention for revision of the right coronary artery. At intermediate follow-up, patients who underwent the supported Ross technique were less likely to have neoaortic root dilatation compared with patients who underwent a standard Ross procedure. Further studies are needed to evaluate the long-term durability of this technique, particularly in regards to the development of significant aortic regurgitation, the rate of reintervention, and application to younger and smaller patients. Copyright © 2015 The Society of Thoracic Surgeons
9. Suspended sediment drift and dispersion at Hibernia
International Nuclear Information System (INIS)
Tedford, T.; Drozdowski, A.; Hannah, C.G.
2003-01-01
Surface water waves and near-bottom currents around the Hibernia oil production platform on the Grand Banks of Newfoundland were examined to determine how the different seasons affect changes in wave magnitude and directions of water currents. Wave observations revealed a strong correlation with seasons, with the larger waves occurring in fall and early winter. There was no obvious seasonality in the size or direction of currents. The benthic boundary layer transport (BBLT) model was used to predict the drift and dispersion pathways of suspended drilling muds discharged from the Hibernia platform. The 2-year study from March 1998 to May 2000 involved 5-day BBLT model simulations covering the complete period of current meter deployment. The study focused on the sensitivity of the drift and dispersion to variability in the physical environment and uncertainty in the bottom stress calculation and particle settling velocity. The BBLT model incorporates a stress dependent particle settling velocity that includes the main features of the flocculations of drill mud fines under marine conditions. The study provides a better understanding of how drill mud concentration levels can change with variations in waves, currents, and bottom stress. It was determined that drift is generally oriented along the northwest/southeast axis, with a typical magnitude of 0.8 cm/sec for the fast settling velocity and 3.1 cm/sec for the slow settling velocity. It was concluded that near-surface or mid-depth discharges of drilling mud in the summer may not reach the sea floor. 17 refs., 13 tabs., 36 figs
10. On nonlinear periodic drift waves
International Nuclear Information System (INIS)
Kauschke, U.; Schlueter, H.
1990-09-01
Nonlinear periodic drift waves are investigated on the basis of a simple perturbation scheme for both the amplitude and inverse frequency. The coefficients for the generation of the forced harmonics are derived, a nonlinear dispersion relation is suggested and a criterion for the onset of the modulational instability is obtained. The results are compared with the ones obtained with the help of a standard KBM-treatment. Moreover cnoidal drift waves are suggested and compared to an experimental observation. (orig.)
11. The OPAL vertex drift chamber
International Nuclear Information System (INIS)
Carter, J.R.; Elcombe, P.A.; Hill, J.C.; Roach, C.M.; Armitage, J.C.; Carnegie, R.K.; Estabrooks, P.; Hemingway, R.; Karlen, D.; McPherson, A.; Pinfold, J.; Roney, J.M.; Routenburg, P.; Waterhouse, J.; Hargrove, C.K.; Klem, D.; Oakham, F.G.; Carter, A.A.; Jones, R.W.L.; Lasota, M.M.B.; Lloyd, S.L.; Pritchard, T.W.; Wyatt, T.R.
1990-01-01
A high precision vertex drift chamber has been installed in the OPAL experiment at LEP. The design of the chamber and the associated readout electronics is described. The performance of the system has been studied using cosmic ray muons and the results of these studies are presented. A space resolution of 50 μm in the drift direction is obtained using the OPAL central detector gas mixture at 4 bar. (orig.)
12. Generalized drift-flux correlation
International Nuclear Information System (INIS)
Takeuchi, K.; Young, M.Y.; Hochreiter, L.E.
1991-01-01
A one-dimensional drift-flux model with five conservation equations is frequently employed in major computer codes, such as TRAC-PD2, and in simulator codes. In this method, the relative velocity between liquid and vapor phases, or slip ratio, is given by correlations, rather than by direct solution of the phasic momentum equations, as in the case of the two-fluid model used in TRAC-PF1. The correlations for churn-turbulent bubbly flow and slug flow regimes were given in terms of drift velocities by Zuber and Findlay. For the annular flow regime, the drift velocity correlations were developed by Ishii et al., using interphasic force balances. Another approach is to define the drift velocity so that flooding and liquid hold-up conditions are properly simulated, as reported here. The generalized correlation is used to reanalyze the MB-2 test data for two-phase flow in a large-diameter pipe. The results are applied to the generalized drift flux velocity, whose relationship to the other correlations is discussed. Finally, the generalized drift flux correlation is implemented in TRAC-PD2. Flow reversal from countercurrent to cocurrent flow is computed in small-diameter U-shaped tubes and is compared with the flooding curve
13. Ross-Stirling engines: Variations on a theme
Energy Technology Data Exchange (ETDEWEB)
Walker, G; Fauvel, R
1986-01-01
A new mechanism called the Ross linkage offers the prospect for compact, lightweight, long-lived, relatively low-cost, Stirling engines with excellent prospects for early commercial developed for various applications. Ross-Stirling engines are unusually compact, with installation envelope about one-third of conventional engines, piston side forces are virtually eliminated facilitating the use of dry lubricated or close tolerance, gas lubricated seals and the linkage geometry automatically favors the large bore/short ratios preferred for Stirling engines. The linkage is simple to make with few moving parts so that cost is relatively low. Various potential or actual embodiments of Ross-Stirling engines are reviewed including Stirling-Stirling gas-fired heat pumps, multicylinder power systems and cryocoolers. The system has sufficient flexibility to readily accommodate widely disparate piston stroke and cylinder diameters. Most work has been done so far with two-piston Stirling engines but the same linkage may be adopted for piston-displacer Stirling engines. 6 refs., 10 figs.
14. The Drifting Star
Science.gov (United States)
2008-04-01
By studying in great detail the 'ringing' of a planet-harbouring star, a team of astronomers using ESO's 3.6-m telescope have shown that it must have drifted away from the metal-rich Hyades cluster. This discovery has implications for theories of star and planet formation, and for the dynamics of our Milky Way. ESO PR Photo 09a/08 ESO PR Photo 09a/08 Iota Horologii The yellow-orange star Iota Horologii, located 56 light-years away towards the southern Horologium ("The Clock") constellation, belongs to the so-called "Hyades stream", a large number of stars that move in the same direction. Previously, astronomers using an ESO telescope had shown that the star harbours a planet, more than 2 times as large as Jupiter and orbiting in 320 days (ESO 12/99). But until now, all studies were unable to pinpoint the exact characteristics of the star, and hence to understand its origin. A team of astronomers, led by Sylvie Vauclair from the University of Toulouse, France, therefore decided to use the technique of 'asteroseismology' to unlock the star's secrets. "In the same way as geologists monitor how seismic waves generated by earthquakes propagate through the Earth and learn about the inner structure of our planet, it is possible to study sound waves running through a star, which forms a sort of large, spherical bell," says Vauclair. The 'ringing' from this giant musical instrument provides astronomers with plenty of information about the physical conditions in the star's interior. And to 'listen to the music', the astronomers used one of the best instruments available. The observations were conducted in November 2006 during 8 consecutive nights with the state-of-the-art HARPS spectrograph mounted on the ESO 3.6-m telescope at La Silla. Up to 25 'notes' could be identified in the unique dataset, most of them corresponding to waves having a period of about 6.5 minutes. These observations allowed the astronomers to obtain a very precise portrait of Iota Horologii: its
15. Characteristic parameters of drift chambers calculation
International Nuclear Information System (INIS)
Duran, I.; Martinez-Laso, L.
1989-01-01
We present here the methods we used to analyse the characteristic parameters of drift chambers. The algorithms to calculate the electric potential in any point for any drift chamber geometry are presented. We include the description of the programs used to calculate the electric field, the drift paths, the drift velocity and the drift time. The results and the errors are discussed. (Author) 7 refs
16. In-Drift Microbial Communities
Energy Technology Data Exchange (ETDEWEB)
D. Jolley
2000-11-09
As directed by written work direction (CRWMS M and O 1999f), Performance Assessment (PA) developed a model for microbial communities in the engineered barrier system (EBS) as documented here. The purpose of this model is to assist Performance Assessment and its Engineered Barrier Performance Section in modeling the geochemical environment within a potential repository drift for TSPA-SR/LA, thus allowing PA to provide a more detailed and complete near-field geochemical model and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). This model and its predecessor (the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document, CRWMS M and O 1998a) was developed to respond to the applicable KTIs. Additionally, because of the previous development of the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a), the M and O was effectively able to resolve a previous KTI concern regarding the effects of microbial processes on seepage and flow (NRC 1998). This document supercedes the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a). This document provides the conceptual framework of the revised in-drift microbial communities model to be used in subsequent performance assessment (PA) analyses.
17. In-Drift Microbial Communities
International Nuclear Information System (INIS)
Jolley, D.
2000-01-01
As directed by written work direction (CRWMS M and O 1999f), Performance Assessment (PA) developed a model for microbial communities in the engineered barrier system (EBS) as documented here. The purpose of this model is to assist Performance Assessment and its Engineered Barrier Performance Section in modeling the geochemical environment within a potential repository drift for TSPA-SR/LA, thus allowing PA to provide a more detailed and complete near-field geochemical model and to answer the key technical issues (KTI) raised in the NRC Issue Resolution Status Report (IRSR) for the Evolution of the Near Field Environment (NFE) Revision 2 (NRC 1999). This model and its predecessor (the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document, CRWMS M and O 1998a) was developed to respond to the applicable KTIs. Additionally, because of the previous development of the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a), the M and O was effectively able to resolve a previous KTI concern regarding the effects of microbial processes on seepage and flow (NRC 1998). This document supercedes the in-drift microbial communities model as documented in Chapter 4 of the TSPA-VA Technical Basis Document (CRWMS M and O 1998a). This document provides the conceptual framework of the revised in-drift microbial communities model to be used in subsequent performance assessment (PA) analyses
18. Drift tubes of Linac 2
CERN Multimedia
CERN PhotoLab
1977-01-01
With the advent of the 800 MeV PS Booster in 1972, the original injector of the PS, a 50 MeV Alvarez-type proton linac, had reached its limits, in terms of intensity and stability. In 1973 one therefore decided to build a new linac (Linac 2), also with a drift-tube Alvarez structure and an energy of 50 MeV. It had a new Cockcroft-Walton preinjector with 750 keV, instead of the previous one with 500 keV. Linac 2 was put into service in 1980. The old Linac 1 was then used for the study of, and later operation with, various types of ions. This picture shows Linac 2 drift-tubes, suspended on stems coming from the top, in contrast to Linac 1, where the drift-tubes stood on stems coming from the bottom.
19. Predicting public sector accountability : From agency drift to forum drift
NARCIS (Netherlands)
2015-01-01
Principal-agent theory has been the dominant theory at the heart of public sector accountability research. The notion of the potentially drifting agent-such as independent public agencies, opaque transnational institutions, or recalcitrant street-level bureaucrats-has been the guiding paradigm in
20. Collisional drift fluid equations and implications for drift waves
International Nuclear Information System (INIS)
Pfirsch, Dieter; Correa-Restrepo, Dario
1996-01-01
The usual theoretical description of drift-wave turbulence (considered to be one possible cause of anomalous transport in a plasma), e.g. the Hasegawa-Wakatani theory, makes use of various approximations, the effects of which are extremely difficult to assess. This concerns in particular the conservation laws for energy and momentum. The latter law is important in relation to charge separation and the resulting electric fields, which are possibly related to the L-H transition. Energy conservation is crucial to the stability behaviour, it will be discussed by means of an example. New collisional multi-species drift-fluid equations were derived by a new method which yields, in a transparent way, conservation of energy and total angular momentum and the law for energy dissipation. Both electrostatic and electromagnetic field variations are considered. The only restriction involved is the validity of the drift approximation; in particular, there are no assumptions restricting the geometry of the system. The method is based primarily on a Lagrangian for dissipationless fluids in the drift approximation with isotropic pressures. The dissipative terms are introduced by adding corresponding terms to the ideal equations of motion and of the pressures. The equations of motion, of course, no longer result from a Lagrangian via Hamilton's principle. However, their relation to the ideal equations also implies a relation to the ideal Lagrangian, which can be used to advantage. Instead of introducing heat conduction one can also assume isothermal behaviour, e.g. T v (x) = constant. Assumptions of this kind are often made in the literature. The new method of introducing dissipation is not restricted to the present kind of theory; it can equally well be applied to theories such as multi-fluid theories without using the drift approximation of the present paper. (author)
1. Understanding Ice Shelf Basal Melting Using Convergent ICEPOD Data Sets: ROSETTA-Ice Study of Ross Ice Shelf
Science.gov (United States)
Bell, R. E.; Frearson, N.; Tinto, K. J.; Das, I.; Fricker, H. A.; Siddoway, C. S.; Padman, L.
2017-12-01
The future stability of the ice shelves surrounding Antarctica will be susceptible to increases in both surface and basal melt as the atmosphere and ocean warm. The ROSETTA-Ice program is targeted at using the ICEPOD airborne technology to produce new constraints on Ross Ice Shelf, the underlying ocean, bathymetry, and geologic setting, using radar sounding, gravimetry and laser altimetry. This convergent approach to studying the ice-shelf and basal processes enables us to develop an understanding of the fundamental controls on ice-shelf evolution. This work leverages the stratigraphy of the ice shelf, which is detected as individual reflectors by the shallow-ice radar and is often associated with surface scour, form close to the grounding line or pinning points on the ice shelf. Surface accumulation on the ice shelf buries these reflectors as the ice flows towards the calving front. This distinctive stratigraphy can be traced across the ice shelf for the major East Antarctic outlet glaciers and West Antarctic ice streams. Changes in the ice thickness below these reflectors are a result of strain and basal melting and freezing. Correcting the estimated thickness changes for strain using RIGGS strain measurements, we can develop decadal-resolution flowline distributions of basal melt. Close to East Antarctica elevated melt-rates (>1 m/yr) are found 60-100 km from the calving front. On the West Antarctic side high melt rates primarily develop within 10 km of the calving front. The East Antarctic side of Ross Ice Shelf is dominated by melt driven by saline water masses that develop in Ross Sea polynyas, while the melting on the West Antarctic side next to Hayes Bank is associated with modified Continental Deep Water transported along the continental shelf. The two sides of Ross Ice Shelf experience differing basal melt in part due to the duality in the underlying geologic structure: the East Antarctic side consists of relatively dense crust, with low amplitude
2. Solar Drift-Pair Bursts
Science.gov (United States)
Stanislavsky, A.; Volvach, Ya.; Konovalenko, A.; Koval, A.
2017-08-01
In this paper a new sight on the study of solar bursts historically called drift pairs (DPs) is presented. Having a simple morphology on dynamic spectra of radio records (two short components separated in time, and often they are very similar) and discovered at the dawn of radio astronomy, their features remain unexplained totally up to now. Generally, the DPs are observed during the solar storms of type III bursts, but not every storm of type III bursts is linked with DPs. Detected by ground-based instruments at decameter and meter wavelengths, the DP bursts are limited in frequency bandwidth. They can drift from high frequencies to low ones and vice versa. Their frequency drift rate may be both lower and higher than typical rates of type III bursts at the same frequency range. The development of low-frequency radio telescopes and data processing provide additional possibilities in the research. In this context the fresh analysis of DPs, made from recent observations in the summer campaign of 2015, are just considered. Their study was implemented by updated tools of the UTR-2 radio telescope at 9-33 MHz. During 10-12 July of 2015, DPs forming the longest patterns on dynamic spectra are about 7% of the total number of recorded DPs. Their marvelous resemblance in frequency drift rates with the solar S-bursts is discussed.
3. Job satisfaction and preference drift.
NARCIS (Netherlands)
Maassen van den Brink, H.; Groot, W.J.N.
1999-01-01
Most empirical studies do not find that higher wages lead to more job satisfaction. In this paper we argue that the insignificant effect of wages on job satisfaction is due to preference drift. We adapt the standard ordered response model to allow for preference shifts. The empirical results support
4. Jimmy, Sinclair, and Jim: on the biographical trail of James Sinclair Ross Jimmy, Sinclair, and Jim: on the biographical trail of James Sinclair Ross
Directory of Open Access Journals (Sweden)
John J. O'Connor
2008-04-01
Full Text Available The deaths of Earle Birney and Robertson Davies late in 1995 reminded readers of Canadian literature that the old order—those writers born before the First World War—was quickly passing. Of the major figures born in the early years of this century (Birney, Davies, Callaghan, MacLennan, Ross, only Ross was still living at the beginning of 1996, albeit in very poor health in a nursing home in Vancouver. The deaths of Earle Birney and Robertson Davies late in 1995 reminded readers of Canadian literature that the old order—those writers born before the First World War—was quickly passing. Of the major figures born in the early years of this century (Birney, Davies, Callaghan, MacLennan, Ross, only Ross was still living at the beginning of 1996, albeit in very poor health in a nursing home in Vancouver.
5. Against Raising Hope of Raising the Dead: Contra Moody and Kubler-Ross.
Science.gov (United States)
Vicchio, Stephen J.; And Others
1979-01-01
Kubler-Ross and Moody have made assertions about survival after death. They argued that the subjects were not dead, but in the process of dying. An alternative explanation to this "glimpse of the afterlife" approach is offered. Other theological objections are raised to the Moody/Kubler-Ross approach. (Author)
6. Giving to Excellence: Generating Philanthropic Support for UK Higher Education. Ross-CASE Report 2016
Science.gov (United States)
Jain, Yashraj
2016-01-01
This report presents findings from the 2016 Ross-CASE Survey of Philanthropic Giving to Universities in UK. The project was conducted by CASE Europe and funded by HEFCE and the Ross-Group. This year's survey comes at a time of great change for the UK charity sector. The historical trend data of previous surveys will be invaluable in helping…
Science.gov (United States)
Stapleton, Paul
2006-01-01
Steven Ross's (2005) recent paper empirically measuring the efficacy of formative assessment compared to the summative variety found that the former produced positive effects on some aspects of language learning. In this critique, it is contended that Ross's study is flawed because his two groups of learners, one receiving summative assessment and…
8. 75 FR 69432 - Ross Bachofer v. Calpine Corporation; Notice of Complaint
Science.gov (United States)
2010-11-12
... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Docket No. EL11-3-000] Ross Bachofer v. Calpine Corporation; Notice of Complaint November 4, 2010. Take notice that on October 26, 2010, pursuant... Federal Power Act, 16 U.S.C. 2824c, Ross Bachofer (Complainant) filed a complaint against Calpine...
9. Mortimer Hills pegmatite uranium prospect: a Rossing-type uranium deposit in the Gascoyne Province
International Nuclear Information System (INIS)
Carter, J.D.
1984-01-01
A uraninite-bearing pegmatite of large dimensions in the Gascoyne Province is described. The pegmatite is compared with the Rossing uranium ore body of South West Africa and the two are shown to have common characteristics. Exploration recommendations for Rossing-type uranium mineralization in the Gascoyne Province are made
10. Approximate Stokes Drift Profiles and their use in Ocean Modelling
Science.gov (United States)
Breivik, Oyvind; Bidlot, Jea-Raymond; Janssen, Peter A. E. M.; Mogensen, Kristian
2016-04-01
Deep-water approximations to the Stokes drift velocity profile are explored as alternatives to the monochromatic profile. The alternative profiles investigated rely on the same two quantities required for the monochromatic profile, viz the Stokes transport and the surface Stokes drift velocity. Comparisons against parametric spectra and profiles under wave spectra from the ERA-Interim reanalysis and buoy observations reveal much better agreement than the monochromatic profile even for complex sea states. That the profiles give a closer match and a more correct shear has implications for ocean circulation models since the Coriolis-Stokes force depends on the magnitude and direction of the Stokes drift profile and Langmuir turbulence parameterizations depend sensitively on the shear of the profile. Of the two Stokes drift profiles explored here, the profile based on the Phillips spectrum is by far the best. In particular, the shear near the surface is almost identical to that influenced by the f-5 tail of spectral wave models. The NEMO general circulation ocean model was recently extended to incorporate the Stokes-Coriolis force along with two other wave-related effects. The ECWMF coupled atmosphere-wave-ocean ensemble forecast system now includes these wave effects in the ocean model component (NEMO).
11. Metocean input data for drift models applications: Loustic study
International Nuclear Information System (INIS)
Michon, P.; Bossart, C.; Cabioc'h, M.
1995-01-01
Real-time monitoring and crisis management of oil slicks or floating structures displacement require a good knowledge of local winds, waves and currents used as input data for operational drift models. Fortunately, thanks to world-wide and all-weather coverage, satellite measurements have recently enabled the introduction of new methods for the remote sensing of the marine environment. Within a French joint industry project, a procedure has been developed using basically satellite measurements combined to metocean models in order to provide marine operators' drift models with reliable wind, wave and current analyses and short term forecasts. Particularly, a model now allows the calculation of the drift current, under the joint action of wind and sea-state, thus radically improving the classical laws. This global procedure either directly uses satellite wind and waves measurements (if available on the study area) or indirectly, as calibration of metocean models results which are brought to the oil slick or floating structure location. The operational use of this procedure is reported here with an example of floating structure drift offshore from the Brittany coasts
12. STS-61B Astronaut Ross During ACCESS Extravehicular Activity
Science.gov (United States)
1985-01-01
The crew assigned to the STS-61B mission included Bryan D. O'Conner, pilot; Brewster H. Shaw, commander; Charles D. Walker, payload specialist; mission specialists Jerry L. Ross, Mary L. Cleave, and Sherwood C. Spring; and Rodolpho Neri Vela, payload specialist. Launched aboard the Space Shuttle Atlantis November 28, 1985 at 7:29:00 pm (EST), the STS-61B mission's primary payload included three communications satellites: MORELOS-B (Mexico); AUSSAT-2 (Australia); and SATCOM KU-2 (RCA Americom). Two experiments were conducted to test assembling erectable structures in space: EASE (Experimental Assembly of Structures in Extravehicular Activity), and ACCESS (Assembly Concept for Construction of Erectable Space Structure). In a joint venture between NASA/Langley Research Center in Hampton, VA and the Marshall Space Flight Center (MSFC), ACCESS and EASE were developed and demonstrated at MSFC's Neutral Buoyancy Simulator (NBS). In this STS-61B onboard photo, astronaut Ross was working on the ACCESS experiment during an Extravehicular Activity (EVA). The primary objective of this experiment was to test the ACCESS structural assembly concept for suitability as the framework for larger space structures and to identify ways to improve the productivity of space construction.
13. 78 FR 19330 - Supplemental Environmental Impact Statement for the Ross In-Situ Uranium Recovery Project in...
Science.gov (United States)
2013-03-29
... Ross In-Situ Uranium Recovery Project in Crook County, Wyoming AGENCY: Nuclear Regulatory Commission... Commission (NRC) for a new source materials license for the proposed Ross In-Situ Uranium Recovery (ISR) Project (Ross Project) proposed to be located in Crook County, Wyoming. The NRC is issuing for public...
14. 76 FR 41308 - Strata Energy, Inc., Ross In Situ Recovery Uranium Project, Crook County, WY; Notice of Materials...
Science.gov (United States)
2011-07-13
..., Inc., Ross In Situ Recovery Uranium Project, Crook County, WY; Notice of Materials License Application...-4737, or by e-mail to [email protected] . The Ross In Situ Recovery Uranium Project License... source and byproduct materials license at its Ross In Situ Recovery Uranium Project site located in Crook...
15. 78 FR 12357 - Brockway Mould, Inc., a Division of Ross International Ltd. Including Robert Lerch From BJR...
Science.gov (United States)
2013-02-22
... Division of Ross International Ltd. Including Robert Lerch From BJR Trucking, Brockport, PA; Amended..., applicable to workers and former workers of Brockway Mould, Inc., a division of Ross International Ltd... Brockway Mould, Inc., a division of Ross International Ltd., including Robert Lerch from BJR Trucking...
16. Drift Chambers detectors; Detectores de deriva
Energy Technology Data Exchange (ETDEWEB)
Duran, I; Martinez laso, L
1989-07-01
We present here a review of High Energy Physics detectors based on drift chambers. The ionization, drift diffusion, multiplication and detection principles are described. Most common drift media are analysed, and a classification of the detectors according to its geometry is done. Finally the standard read-out methods are displayed and the limits of the spatial resolution are discussed. (Author) 115 refs.
17. A Stokes drift approximation based on the Phillips spectrum
Science.gov (United States)
Breivik, Øyvind; Bidlot, Jean-Raymond; Janssen, Peter A. E. M.
2016-04-01
A new approximation to the Stokes drift velocity profile based on the exact solution for the Phillips spectrum is explored. The profile is compared with the monochromatic profile and the recently proposed exponential integral profile. ERA-Interim spectra and spectra from a wave buoy in the central North Sea are used to investigate the behavior of the profile. It is found that the new profile has a much stronger gradient near the surface and lower normalized deviation from the profile computed from the spectra. Based on estimates from two open-ocean locations, an average value has been estimated for a key parameter of the profile. Given this parameter, the profile can be computed from the same two parameters as the monochromatic profile, namely the transport and the surface Stokes drift velocity.
18. ATLAS Muon Drift Tube Electronics
Energy Technology Data Exchange (ETDEWEB)
Arai, Y [KEK, High Energy Accelerator Research Organisation, Tsukuba (Japan); Ball, B; Chapman, J W; Dai, T; Ferretti, C; Gregory, J [University of Michigan, Department of Physics, Ann Arbor, MI (United States); Beretta, M [INFN Laboratori Nazionali di Frascati, Frascati (Italy); Boterenbrood, H; Jansweijer, P P M [Nikhef National Institute for Subatomic Physics, Amsterdam (Netherlands); Brandenburg, G W; Fries, T; Costa, J Guimaraes da; Harder, S; Huth, J [Harvard University, Laboratory for Particle Physics and Cosmology, Cambridge, MA (United States); Ceradini, F [INFN Roma Tre and Universita Roma Tre, Dipartimento di Fisica, Roma (Italy); Hazen, E [Boston University, Physics Department, Boston, MA (United States); Kirsch, L E [Brandeis University, Department of Physics, Waltham, MA (United States); Koenig, A C [Radboud University Nijmegen/Nikhef, Dept. of Exp. High Energy Physics, Nijmegen (Netherlands); Lanza, A [INFN Pavia, Pavia (Italy); Mikenberg, G [Weizmann Institute of Science, Department of Particle Physics, Rehovot (Israel)], E-mail: [email protected] (and others)
2008-09-15
This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60 {mu}m, which corresponds to a momentum accuracy of about 10% at p{sub T}= 1 TeV. The design and performance of the MDT readout electronics as well as the electronics for controlling, monitoring and powering the detector will be discussed. These electronics have been extensively tested under simulated running conditions and have undergone radiation testing certifying them for more than 10 years of LHC operation. They are now installed on the ATLAS detector and are operating during cosmic ray commissioning runs.
19. ATLAS Muon Drift Tube Electronics
CERN Document Server
Arai, Y; Beretta, M; Boterenbrood, H; Brandenburg, G W; Ceradini, F; Chapman, J W; Dai, T; Ferretti, C; Fries, T; Gregory, J; Guimarães da Costa, J; Harder, S; Hazen, E; Huth, J; Jansweijer, P P M; Kirsch, L E; König, A C; Lanza, A; Mikenberg, G; Oliver, J; Posch, C; Richter, R; Riegler, W; Spiriti, E; Taylor, F E; Vermeulen, J; Wadsworth, B; Wijnen, T A M
2008-01-01
This paper describes the electronics used for the ATLAS monitored drift tube (MDT) chambers. These chambers are the main component of the precision tracking system in the ATLAS muon spectrometer. The MDT detector system consists of 1,150 chambers containing a total of 354,000 drift tubes. It is capable of measuring the sagitta of muon tracks to an accuracy of 60 microns, which corresponds to a momentum accuracy of about 10% at pT = 1 TeV. The design and performance of the MDT readout electronics as well as the electronics for controlling, monitoring and powering the detector will be discussed. These electronics have been extensively tested under simulated running conditions and have undergone radiation testing certifying them for more than 10 years of LHC operation. They are now installed on the ATLAS detector and are operating during cosmic ray commissioning runs.
20. A Pascalian lateral drift sensor
International Nuclear Information System (INIS)
Jansen, H.
2016-01-01
A novel concept of a layer-wise produced semiconductor sensor for precise particle tracking is proposed herein. In contrast to common semiconductor sensors, local regions with increased doping concentration deep in the bulk termed charge guides increase the lateral drift of free charges on their way to the read-out electrode. This lateral drift enables charge sharing independent of the incident position of the traversing particle. With a regular grid of charge guides the lateral charge distribution resembles a normalised Pascal's triangle for particles that are stopped in depths lower than the depth of the first layer of the charge guides. For minimum ionising particles a sum of binomial distributions describes the lateral charge distribution. This concept decouples the achievable sensor resolution from the pitch size as the characteristic length is replaced by the lateral distance of the charge guides.
1. A Pascalian lateral drift sensor
Energy Technology Data Exchange (ETDEWEB)
Jansen, H., E-mail: [email protected]
2016-09-21
A novel concept of a layer-wise produced semiconductor sensor for precise particle tracking is proposed herein. In contrast to common semiconductor sensors, local regions with increased doping concentration deep in the bulk termed charge guides increase the lateral drift of free charges on their way to the read-out electrode. This lateral drift enables charge sharing independent of the incident position of the traversing particle. With a regular grid of charge guides the lateral charge distribution resembles a normalised Pascal's triangle for particles that are stopped in depths lower than the depth of the first layer of the charge guides. For minimum ionising particles a sum of binomial distributions describes the lateral charge distribution. This concept decouples the achievable sensor resolution from the pitch size as the characteristic length is replaced by the lateral distance of the charge guides.
2. MPS II drift chamber system
International Nuclear Information System (INIS)
Platner, E.D.
1982-01-01
The MPS II detectors are narrow drift space chambers designed for high position resolution in a magnetic field and in a very high particle flux environment. Central to this implementation was the development of 3 multi-channel custom IC's and one multi-channel hybrid. The system is deadtimeless and requires no corrections on an anode-to-anode basis. Operational experience and relevance to ISABELLE detectors is discussed
3. Shear wall ultimate drift limits
International Nuclear Information System (INIS)
Duffey, T.A.; Goldman, A.; Farrar, C.R.
1994-04-01
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated
4. [A reappraisal of the works of Elisabeth Kubler-Ross].
Science.gov (United States)
Afonso, Selene Beviláqua Chaves; Minayo, Maria Cecília de Souza
2013-09-01
This article presents a reappraisal of part of the works of Elizabeth Kubler-Ross, one of the most quoted authors addressing the end of life process, mourning and dying. Her work has contributed to a clearer understanding of these issues by health professionals, families, religious and lay people who handle and/or experience mourning. She has also been the subject of controversy related to ethical issues and the scientific rigor of her work. The books analyzed in this article are: On death and dying (1969); Questions and answers on death and dying (1971); Living with death and dying (1981); On children and death(1983); On life after death (1991) and Life lessons (2000).
5. The Kubler-Ross model, physician distress, and performance reporting.
Science.gov (United States)
Smaldone, Marc C; Uzzo, Robert G
2013-07-01
Physician performance reporting has been proposed as an essential component of health-care reform, with the aim of improving quality by providing transparency and accountability. Despite strong evidence demonstrating regional variation in practice patterns and lack of evidence-based care, public outcomes reporting has been met with resistance from medical professionals. Application of the Kubler-Ross 'five stages of grief' model--a conceptual framework consisting of a series of emotional stages (denial, anger, bargaining, depression, and acceptance) inspired by work with terminally ill patients--could provide some insight into why physicians are reluctant to accept emerging quality-reporting mechanisms. Physician-led quality-improvement initiatives are vital to contemporary health-care reform efforts and applications in urology, as well as other medical disciplines, are currently being explored.
6. Ross E. Baker, DC: A Canadian chiropractic survivor.
Science.gov (United States)
Brown, Douglas M
2014-03-01
This paper is an historical biography of a fortunate man. It begins with a glimpse of Ross E. Baker's origins in south-western Ontario, watches him going to school and working in Hamilton before joining the Canadian Army and shipping off to Europe to fight in the Second World War. At War's end, the article picks up Dr. Baker as he comes home, starts a family, becomes a chiropractor and sustains a viable practice. Now in the twilight of life, the good doctor is last seen content with his retirement, spending days at his cottage property, reviewing his memoirs and reflecting on the tumult, terror and eventual triumph of the D-Day landing at Normandy.
7. Albert Ross Tilley: The legacy of a Canadian plastic surgeon.
Science.gov (United States)
Mowbrey, Kevin
2013-01-01
The present article chronicles the career of Dr Albert Ross Tilley, one of the most important Canadian plastic surgeons of the 20th century. Tilley is most well known for his innovations of burn management during World War II and his treatment of a group of burn patients known affectionately as the 'Guinea Pig Club'. In addition to the superb surgical skills he applied to the physical wounds of his patients, Tilley was also a pioneer of caring for the emotional and psychological afflictions suffered by many airmen of World War II. As one of the founding fathers of the Canadian Society of Plastic Surgeons, Tilley's work was instrumental in establishing the specialty and ensured its prosperity for years to come. Serving in the capacity of leader, educator and innovator, Tilley remains one of Canada's most decorated physicians, and his body of work encompasses contributions to the medical field that remain significant and beneficial to patient care to this day.
8. Sentinel-1 provides ice drift observations for Copernicus Marine Environment Monitoring Service (CMEMS)
DEFF Research Database (Denmark)
Toudal Pedersen, Leif; Saldo, Roberto
are matched every month in the processing system.The quality of the ice drift vectors are routinely verified against GPS locations of drift buoys and the RMS difference between the baseline product available through the Copernicus Marine Environment Monitoring Service data portal and GPS drifters is ~500......Sea ice drift information with an accuracy that allows also ice deformation (divergence, shear, vorticity) to be derived is being operationally generated in the Copernicus Marine Environment Monitoring Service (CMEMS).The method is based on 2-dimensional digital cross correlation where subsections......View project in 2007 when large volumes of ENVISAT ASAR images of the Polar regions became available during the International Polar Year. A dataset of daily ice drift vectors of the Polar Regions (North and South) is now available covering the time period from 2007 to the present time.In 2009 the processing...
9. Optimization of drift gases for accuracy in pressurized drift tubes
CERN Document Server
Kirchner, J J; Dinner, A R; Fidkowski, K J; Wyatt, J H
2001-01-01
Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the $E \\propto \\frac{1}{r}$ field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given.
10. Optimization of drift gases for accuracy in pressurized drift tubes
International Nuclear Information System (INIS)
Kirchner, J.J.; Becker, U.J.; Dinner, R.B.; Fidkowski, K.J.; Wyatt, J.H.
2001-01-01
Modern detectors such as ATLAS use pressurized drift tubes to minimize diffusion and achieve high coordinate accuracy. However, the coordinate accuracy depends on the exact knowledge of converting measured times into coordinates. Linear space-time relationships are best for reconstruction, but difficult to achieve in the E∝1/r field. Previous mixtures, which contained methane or other organic quenchers, are disfavored because of ageing problems. From our studies of nitrogen and carbon dioxide, two mixtures with only small deviations from linearity were determined and measured. Scaling laws for different pressures and magnetic fields are also given
11. Satellite-tracked drifting buoy observations in the south equatorial current in the Indian Ocean
Digital Repository Service at National Institute of Oceanography (India)
Shetye, S.R.; Michael, G.S.
two buoys moved north and the third moved south. Over the open sea regime the buoys moved with a speed of approximately 30 cm/s at an angle of about 35 degrees to the left of the wind. The overall tendencies seen in the buoy drift are similar to those...
12. Measurement of the positron-drift time relation of a high-pressure drift chamber
International Nuclear Information System (INIS)
Pruefert, W.
1989-04-01
As a test of its performance, the measurement of the drift time versus drift distance relation of a high pressure drift chamber using cosmic rays is described. Two multiwire proportional chambers, mounted above and below the detector, are used to define the track of the cosmic particle in the drift chamber. The drift chamber is read out by FADCs (Flash Analog to Digital Converter), and the drift time is determined from the FADC signals by the DOS- (Difference Of Samples) method. The measured drift time versus drift distance relation showed good agreement with the relation, which is expected from the spatial dependence of the electric field and the dependence of the drift velocity on this field. (orig.) [de
13. Pulse shape simulation for drift chambers with long drift paths
International Nuclear Information System (INIS)
Mayer, H.J.
1987-01-01
A detailed Monte Carlo program for the simulation of drift chamber pulse shapes is described. It has been applied to the case of a jet chamber with drift paths up to 24 cm. Results on pulse shapes and corresponding spatial and double hit resolution are discussed and compared to recent measurements of the OPAL central detector jet chamber full size prototype and to measurements of a small 20-wire prototype, which was designed to study the pulse shapes generated by tracks in a magnetic field. Simulated pulse shapes and spatial resolutions agree well with the experimental data. Clustering, saturation and wire crosstalk are shown to be necessary ingredients in the simulation. A deterioration in resolution due to the influence of crosstalk signals is correctly reproduced, as well as the cancellation of this effect by a hardwired first and second neighbour crosstalk compensation. The simulation correctly describes the asymmetry in spatial resolution observed for tracks with positive or negative inclination against the wire plane when a magnetic field is present. The effect of saturation on double hit resolution is found to be small. The magnetic field is predicted to improve the double hit resolution. (orig.)
14. Pulse shape simulation for drift chambers with long drift paths
Energy Technology Data Exchange (ETDEWEB)
Mayer, H J
1987-09-15
A detailed Monte Carlo program for the simulation of drift chamber pulse shapes is described. It has been applied to the case of a jet chamber with drift paths up to 24 cm. Results on pulse shapes and corresponding spatial and double hit resolution are discussed and compared to recent measurements of the OPAL central detector jet chamber full size prototype and to measurements of a small 20-wire prototype, which was designed to study the pulse shapes generated by tracks in a magnetic field. Simulated pulse shapes and spatial resolutions agree well with the experimental data. Clustering, saturation and wire crosstalk are shown to be necessary ingredients in the simulation. A deterioration in resolution due to the influence of crosstalk signals is correctly reproduced, as well as the cancellation of this effect by a hardwired first and second neighbour crosstalk compensation. The simulation correctly describes the asymmetry in spatial resolution observed for tracks with positive or negative inclination against the wire plane when a magnetic field is present. The effect of saturation on double hit resolution is found to be small. The magnetic field is predicted to improve the double hit resolution.
15. Drift waves in a stellarator
International Nuclear Information System (INIS)
Bhattacharjee, A.; Sedlak, J.E.; Similon, P.L.; Rosenbluth, M.N.; Ross, D.W.
1982-11-01
We investigate the eigenmode structure of drift waves in a straight stellarator using the ballooning mode formalism. The electrons are assumed to be adiabatic and the ions constitute a cold, magnetized fluid. The effective potential has an overall parabolic envelope but is modulated strongly by helical ripples along B. We have found two classes of solutions: those that are strongly localized in local helical wells, and those that are weakly localized and have broad spatial extent. The weakly localized modes decay spatially due to the existence of Mathieu resonances between the periods of the eigenfunction and the effective potential
16. Kinetic theory of drift waves
International Nuclear Information System (INIS)
1988-01-01
The linear stability of the electrostatic drift waves in slab geometry has been studied analytically and numerically. The effects of magnetic field with shear, of the finite Larmor radius, of an electron streaming, of a temperature gradient and of collisions have been retained. The analytical solution has been obtained using the matched asymptotic expansion technique, and an expression for the critical streaming parameter has been derived. Finally, assuming that the transport in the Reversed Field Pinches is dominated by this instability, a scaling law for the temperature in such machine is derived
17. Experimental work on drift chambers
International Nuclear Information System (INIS)
Alcaraz, J.; Duran, I.; Gonzalez, E.; Martinez-Laso, L.; Olmos, P.
1989-01-01
An experimental work made on drift chambers is described in two chapters. In the firt chapter we present the description of the experimental installation used, as well as some details on the data adquisition systems and the characteristics on three ways used for calibration proposes (cosmic muons, β radiation and test beam using SPS at CERN facilities). The second chapter describes the defferent prototypes studied. The experimental set up and the analysis are given. Some results are discussed. The magnetic field effect is also studied. (Author)
18. Drift vortices in continuous media
International Nuclear Information System (INIS)
Chernousenko, V.M.; Chernenko, I.V.; Chernyshenko, S.V.
1989-01-01
The work is devoted to investigation into the problems of large-scale cortex drift and generation in continuous media based on the solution of notably non-linear differential equations. Using the capability of the modern computer technique it is possible to consider a series of cases with regard to medium viscosity and its inhomogeneity and with regard to three-dimensional vortex nature. Based on the solutions obtained the large-scale steady-state vortex generation processes are considered. The results can be used when studying non-linear phenomena in plasma and processes of substance and energy transfer in non-equilibrium media. 16 refs.; 5 figs
19. Elisabeth Kubler-Ross and the Tradition of the Private Sphere: An Analysis of Symbols.
Science.gov (United States)
Klass, Dennis
1981-01-01
Shows how Kubler-Ross' schema functions as a symbol system. Analyzes the symbol "acceptance." Shows how that symbol is part of a strong American tradition of symbols of the private sphere. (Author/JAC)
20. Transcatheter Pulmonary Valve Replacement for Right Ventricular Outflow Tract Conduit Dysfunction After the Ross Procedure
DEFF Research Database (Denmark)
Gillespie, Matthew J; McElhinney, Doff B; Kreutzer, Jacqueline
2015-01-01
BACKGROUND: Right ventricular outflow tract (RVOT) conduit dysfunction is a limitation of the Ross procedure. Transcatheter pulmonary valve replacement (TPVR) could alter the impact of conduit dysfunction and the risk-benefit balance for the Ross procedure. METHODS: Retrospective review of databa......BACKGROUND: Right ventricular outflow tract (RVOT) conduit dysfunction is a limitation of the Ross procedure. Transcatheter pulmonary valve replacement (TPVR) could alter the impact of conduit dysfunction and the risk-benefit balance for the Ross procedure. METHODS: Retrospective review....... Of these, 56 (84%) received a Melody valve; in 5 of the 11 patients who did not, the implant was aborted due to concern for coronary artery compression, and 1 implanted patient required emergent surgery for left coronary compression. The RVOT gradient decreased from a median 38 mm Hg to 13.5 mm Hg (p
1. 76 FR 81962 - Final Environmental Impact Statement for General Management Plan, Ross Lake National Recreation...
Science.gov (United States)
2011-12-29
... soundscapes, and scenery through traditional outdoor activities. The NPS would actively manage to reduce... Ross Lake NRA in order to protect and enhance soundscapes and wilderness character, experience, and...
2. Long-term results of the Ross procedure in a population-based follow-up.
Science.gov (United States)
Kallio, Merja; Pihkala, Jaana; Sairanen, Heikki; Mattila, Ilkka
2015-05-01
The purpose of this study was to evaluate the long-term outcomes of the Ross procedure in a nationwide follow-up. This retrospective study involved all children treated with the Ross procedure in Finland between 1994 and 2009. The clinical records were reviewed for demographic and anatomical characteristics, Ross operation data, surgical history and status at the latest follow-up. The median follow-up time was 11.5 (range 2.4-19.2) years. Fifty-one patients underwent either the Ross (n = 37) or the Ross-Konno (n = 14) procedure at a median age of 4.8 (range 0.02-16.3) years, including 13 infants (Ross procedure was aortic valve stenosis, regurgitation or both, which was observed in 29, 24 and 47% of patients, respectively. The early mortality (before hospital discharge) rate was 10% (31% in infants) and the late mortality rate 6% (15% in infants). Higher mortality was discovered in patients treated with the Ross-Konno procedure (P = 0.001). The most common cause for reintervention was pulmonary homograft stenosis. The rate of freedom from right ventricular outflow tract reintervention was 98% at 5 years, 83% at 10 years and 59% at 15 years. The rate of freedom from autograft reintervention was 98% at 5 and 10 years, and 81% at 15 years. At the latest follow-up visit, mild-to-moderate aortic root dilatation was reported in 52% of patients, and 4 patients had undergone autograft-related reinterventions. Trivial autograft valve regurgitation was commonly seen, but only 1 patient developed severe autograft regurgitation requiring mechanical valve replacement 15.9 years after the Ross operation. The most common reason for reintervention after the Ross procedure in children is homograft stenosis. Aortic root dilatation and autograft valve regurgitation are relatively common but rarely lead to reinterventions before adulthood. Intraoperative complications and complex cardiac anatomy are associated with high mortality in infants undergoing the Ross-Konno procedure. In our
3. New Crustal Boundary Revealed Beneath the Ross Ice Shelf, Antarctica, through ROSETTA-Ice Integrated Aerogeophysics, Geology, and Ocean Research
Science.gov (United States)
Tinto, K. J.; Siddoway, C. S.; Bell, R. E.; Lockett, A.; Wilner, J.
2017-12-01
Now submerged within marine plateaus and rises bordering Antarctica, Australia and Zealandia, the East Gondwana accretionary margin was a belt of terranes and stitched by magmatic arcs, later stretched into continental ribbons separated by narrow elongate rifts. This crustal architecture is known from marine geophysical exploration and ocean drilling of the mid-latitude coastal plateaus and rises. A concealed sector of the former East Gondwana margin that underlies the Ross Ice Shelf (RIS), Antarctica, is the focus of ROSETTA-ICE, a new airborne data acquisition campaign that explores the crustal makeup, tectonic boundaries and seafloor bathymetry beneath RIS. Gravimeters and a magnetometer are deployed by LC130 aircraft surveying along E-W lines spaced at 10 km, and N-S tie lines at 55 km, connect 1970s points (RIGGS) for controls on ocean depth and gravity. The ROSETTA-ICE survey, 2/3 completed thus far, provides magnetic anomalies, Werner depth-to-basement solutions, a new gravity-based bathymetric model at 20-km resolution, and a new crustal density map tied to the 1970s data. Surprisingly, the data reveal that the major lithospheric boundary separating East and West Antarctica lies 300 km east of the Transantarctic Mountains, beneath the floating RIS. The East and West regions have contrasting geophysical characteristics and bathymetry, with relatively dense lithosphere, low amplitude magnetic anomalies, and deep bathymetry on the East Antarctica side, and high amplitude magnetic anomalies, lower overall density and shallower water depths on the West Antarctic side. The Central High, a basement structure cored at DSDP Site 270 and seismically imaged in the Ross Sea, continues beneath RIS as a faulted but coherent crustal ribbon coincident with the tectonic boundary. The continuity of Gondwana margin crustal architecture discovered beneath the West Antarctic Ice Sheet requires a revision of the existing tectonic framework. The sub-RIS narrow rift basins and
4. Drift-time measurement electronics
International Nuclear Information System (INIS)
Pernicka, M.
1978-01-01
The aim of the construction was to improve the time resolution without using the facility of time stretching, to have a fast read-out possibility, and to be still cheaper in price in comparison to other systems. A possibility was thus foreseen for using the firm Fairchild. These integrated circuits (IC) have, for example, a propagation delay of 0.75 ns for a gate. One can expect therefore less time jitter and less time difference between the different inputs. Furthermore this IC offers a greater flexibility and therefore the number of ICs decreases and distances become smaller. Working with clock frequencies up to 166.6 MHz is easily possible without running into timing problems. On the other hand, to make full use of the advantages of this IC, it was necessary to build the print as a multilayer. The only risk could be in the use of a completely new product. A further aim was to build for this system a second type of drift-time module with a short time range for measuring drift time and pulse length in rotated multiwire proportional chambers. A brief outline of the specifications of the different modules is given in table 1. (Auth.)
5. An effective drift correction for dynamical downscaling of decadal global climate predictions
Science.gov (United States)
Paeth, Heiko; Li, Jingmin; Pollinger, Felix; Müller, Wolfgang A.; Pohlmann, Holger; Feldmann, Hendrik; Panitz, Hans-Jürgen
2018-04-01
Initialized decadal climate predictions with coupled climate models are often marked by substantial climate drifts that emanate from a mismatch between the climatology of the coupled model system and the data set used for initialization. While such drifts may be easily removed from the prediction system when analyzing individual variables, a major problem prevails for multivariate issues and, especially, when the output of the global prediction system shall be used for dynamical downscaling. In this study, we present a statistical approach to remove climate drifts in a multivariate context and demonstrate the effect of this drift correction on regional climate model simulations over the Euro-Atlantic sector. The statistical approach is based on an empirical orthogonal function (EOF) analysis adapted to a very large data matrix. The climate drift emerges as a dramatic cooling trend in North Atlantic sea surface temperatures (SSTs) and is captured by the leading EOF of the multivariate output from the global prediction system, accounting for 7.7% of total variability. The SST cooling pattern also imposes drifts in various atmospheric variables and levels. The removal of the first EOF effectuates the drift correction while retaining other components of intra-annual, inter-annual and decadal variability. In the regional climate model, the multivariate drift correction of the input data removes the cooling trends in most western European land regions and systematically reduces the discrepancy between the output of the regional climate model and observational data. In contrast, removing the drift only in the SST field from the global model has hardly any positive effect on the regional climate model.
6. An optimal ross filter system for soft X-ray spectra measurement
International Nuclear Information System (INIS)
Huang Tianxuan; Zheng Zhijian; Sun Kexu; Jiang Shaoen
2000-01-01
A broadband Ross filter spectrometer is described for measuring soft X-ray radiation (0.1∼1.5 keV) emitted from laser plasma. It consists of a number of channels, each representing a Ross filter pair in conjunction with Al cathode X-ray diodes. An optimal channel has flat response within the sensitivity band, and minimal response outside it. The effect of some uncertainties on the accuracy of measurements is calculated
7. Limits on the Secular Drift of the TMI Calibration
Science.gov (United States)
Wilheit, T. T.; Farrar, S.; Jones, L.; Santos-Garcia, A.
2012-12-01
Data from the TRMM Microwave Imager (TMI) can be applied to the problem of determining the trend in oceanic precipitation over more than a decade. It is thus critical to know if the calibration of the instrument has any drift over this time scale. Recently a set of Windsat data with a self-consistent calibration covering July 2005 through June of 2006 and all of 2011 has become available. The mission of Windsat, determining the feasibility of measuring oceanic wind speed and direction, requires extraordinary attention to instrument calibration. With TRMM being in a low inclination orbit and Windsat in a near polar sun synchronous orbit, there are many observations coincident in space and nearly coincident in time. A data set has been assembled where the observations are averaged over 1 degree boxes of latitude and longitude and restricted to a maximum of 1 hour time difference. University of Central Florida (UCF) compares the two radiometers by computing radiances based on Global Data Assimilation System (GDAS) analyses for all channels of each radiometer for each box and computing double differences for corresponding channels. The algorithm is described in detail by Biswas et al., (2012). Texas A&M (TAMU) uses an independent implementation of GDAS-based algorithm and another where the radiances of Windsat are used to compute Sea Surface Temperature, Sea Surface Wind Speed, Precipitable Water and Cloud Liquid Water for each box. These are, in turn, used to compute the TMI radiances. These two algorithms have been described in detail by Wilheit (2012). Both teams apply stringent filters to the boxes to assure that the conditions are consistent with the model assumptions. Examination of both teams' results indicates that the drift is less than 0.04K over the 5 ½ year span for the 10 and 37 GHz channels of TMI. The 19 and 21 GHz channels have somewhat larger differences, but they are more influenced by atmospheric changes. Given the design of the instruments, it is
8. The large cylindrical drift chamber of TASSO
International Nuclear Information System (INIS)
Boerner, H.; Fischer, H.M.; Hartmann, H.; Loehr, B.; Wollstadt, M.; Fohrmann, R.; Schmueser, P.; Cassel, D.G.; Koetz, U.; Kowalski, H.
1980-03-01
We have built and operated a large cylindrical drift chamber for the TASSO experiment at the DESY storage ring, PETRA. The chamber has a length of 3.5 m, a diameter of 2.5 m, and a total of 2340 drift cells. The cells are arranged in 15 concentric layers such that tracks can be reconstructed in three dimensions. A spatial resolution of 220 μm has been achieved for tracks of normal incidence on the drift cells. (orig.)
9. Drift chamber tracking with neural networks
International Nuclear Information System (INIS)
Lindsey, C.S.; Denby, B.; Haggerty, H.
1992-10-01
We discuss drift chamber tracking with a commercial log VLSI neural network chip. Voltages proportional to the drift times in a 4-layer drift chamber were presented to the Intel ETANN chip. The network was trained to provide the intercept and slope of straight tracks traversing the chamber. The outputs were recorded and later compared off line to conventional track fits. Two types of network architectures were studied. Applications of neural network tracking to high energy physics detector triggers is discussed
10. Electron injection in semiconductor drift detectors
International Nuclear Information System (INIS)
Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Castoldi, A.; Vacchi, A.
1990-01-01
The paper reports the first successful results of a simple MOS structure to inject electrons at a given position in Silicon Drift Detectors. The structure allows on-line calibration of the drift velocity of electrons within the detector. The calibration is a practical method to trace the temperature dependence of the electron mobility. Several of these injection structures can be implemented in silicon drift detectors without additional steps in the fabrication process. 5 refs., 11 figs
11. Cooling tower drift: comprehensive case study
International Nuclear Information System (INIS)
Laulainen, N.S.; Ulanski, S.L.
1979-01-01
A comprehensive experiment to study drift from mechanical drift cooling towers was conducted during June 1978 at the PG and E Pittsburg Power Plant. The data from this study will be used for validation of drift deposition models. Preliminary results show the effects of tower geometry and orientation with respect to the wind and to single- or two-tower operation. The effect of decreasing relative humidity during a test run can also be seen
12. Improved Survival After the Ross Procedure Compared With Mechanical Aortic Valve Replacement.
Science.gov (United States)
Buratto, Edward; Shi, William Y; Wynne, Rochelle; Poh, Chin L; Larobina, Marco; O'Keefe, Michael; Goldblatt, John; Tatoulis, James; Skillington, Peter D
2018-03-27
It is unclear whether the Ross procedure offers superior survival compared with mechanical aortic valve replacement (AVR). This study evaluated experience and compared long-term survival between the Ross procedure and mechanical AVR. Between 1992 and 2016, a total of 392 Ross procedures were performed. These were compared with 1,928 isolated mechanical AVRs performed during the same time period as identified using the University of Melbourne and Australia and New Zealand Society of Cardiac and Thoracic Surgeons' Cardiac Surgery Databases. Only patients between 18 and 65 years of age were included. Propensity-score matching was performed for risk adjustment. Ross procedure patients were younger, and had fewer cardiovascular risk factors. The Ross procedure was associated with longer cardiopulmonary bypass and aortic cross-clamp times. Thirty-day mortality was similar (Ross, 0.3%; mechanical, 0.8%; p = 0.5). Ross procedure patients experienced superior unadjusted long-term survival at 20 years (Ross, 95%; mechanical, 68%; p mechanical, 84%; p = 0.018). In this Australian, propensity-score matched study, the Ross procedure was associated with better long-term survival compared with mechanical AVR. In younger patients, with a long life expectancy, the Ross procedure should be considered in centers with sufficient expertise. Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.
13. Quantifying fall migration of Ross's gulls (Rhodostethia rosea) past Point Barrow, Alaska
Science.gov (United States)
Uher-Koch, Brian D.; Davis, Shanti E.; Maftei, Mark; Gesmundo, Callie; Suydam, R.S.; Mallory, Mark L.
2014-01-01
The Ross's gull (Rhodostethia rosea) is a poorly known seabird of the circumpolar Arctic. The only place in the world where Ross's gulls are known to congregate is in the near-shore waters around Point Barrow, Alaska where they undertake an annual passage in late fall. Ross's gulls seen at Point Barrow are presumed to originate from nesting colonies in Siberia, but neither their origin nor their destination has been confirmed. Current estimates of the global population of Ross's gulls are based largely on expert opinion, and the only reliable population estimate is derived from extrapolations from previous counts conducted at Point Barrow, but these data are now over 25 years old. In order to update and clarify the status of this species in Alaska, our study quantified the timing, number, and flight direction of Ross's gulls passing Point Barrow in 2011. We recorded up to two-thirds of the estimated global population of Ross's gulls (≥ 27,000 individuals) over 39 days with numbers peaking on 16 October when we observed over 7,000 birds during a three-hour period.
14. Ross, macdonald, and a theory for the dynamics and control of mosquito-transmitted pathogens.
Science.gov (United States)
Smith, David L; Battle, Katherine E; Hay, Simon I; Barker, Christopher M; Scott, Thomas W; McKenzie, F Ellis
2012-01-01
Ronald Ross and George Macdonald are credited with developing a mathematical model of mosquito-borne pathogen transmission. A systematic historical review suggests that several mathematicians and scientists contributed to development of the Ross-Macdonald model over a period of 70 years. Ross developed two different mathematical models, Macdonald a third, and various "Ross-Macdonald" mathematical models exist. Ross-Macdonald models are best defined by a consensus set of assumptions. The mathematical model is just one part of a theory for the dynamics and control of mosquito-transmitted pathogens that also includes epidemiological and entomological concepts and metrics for measuring transmission. All the basic elements of the theory had fallen into place by the end of the Global Malaria Eradication Programme (GMEP, 1955-1969) with the concept of vectorial capacity, methods for measuring key components of transmission by mosquitoes, and a quantitative theory of vector control. The Ross-Macdonald theory has since played a central role in development of research on mosquito-borne pathogen transmission and the development of strategies for mosquito-borne disease prevention.
15. Fast non-explosive gases for drift chambers
International Nuclear Information System (INIS)
Green, D.; Haggerty, H.; Oshima, N.; Yamada, R.
1988-05-01
Typical gases which are stock at Fermilab are Ar:C 2 H 6 (50:50) and Ar:CO 2 (80:20). Argon:Ethane has the virtue of high gas gain and a saturated drift velocity. In fact, parametrizing the drift velocity as a function of electric field we find v/sub d/(E) = v/sub o/(1/minus/e/sup -E/E/o) with v/sub o/ ≅ 5.4 cm/μsec and E/sub o/ = 160 V/cm. However, safety considerations make this gas somewhat inconvenient. The addition of alcohol as quencher also raises the saturation field to, for example, E/sub o/ ≅ 500 V/cm for 1.5% added alcohol. This gas also tends to break up in a high-beam flux environment and leave carbon deposits. The addition of alcohol to avoid such aging often takes a unit cell out of saturation over its entire volume. Finally, for collider applications it is useful to exclude free protons from the gas in order to reduce the sensitivity to the sea of slow neutrons which are present in the collider environment. In contrast, Ar:CO 2 (80:20) is a gas with more moderate gas gain. The drift velocity at high field is v/sub d/(E > 1.5 kV/cm) ≅ 5.8 cm/μsec. For most field configurations this gas does not saturate, causing a long tail in the drift time distrubtion due to low field regions in the unit cell. The virtues of this gas mixture are that it is cheap, not flammable, and stable under high-beam flux. However as the Collider Upgrade progresses, we wish to find a gas which is faster than 5.0 cm/μsec since the time separation between collisions will at some point be less than drift time of 1μsec for drift distance of 5 cm. 3 refs., 5 figs
16. Geomorphology and drift potential of major aeolian sand deposits in Egypt
Science.gov (United States)
Hereher, Mohamed E.
2018-03-01
Aeolian sand deposits cover a significant area of the Egyptian deserts. They are mostly found in the Western Desert and Northern Sinai. In order to understand the distribution, pattern and forms of sand dunes in these dune fields it is crucial to analyze the wind regimes throughout the sandy deserts of the country. Therefore, a set of wind data acquired from twelve meteorological stations were processed in order to determine the drift potential (DP), the resultant drift potential (RDP) and the resultant drift direction (RDD) of sand in each dune field. The study showed that the significant aeolian sand deposits occur in low-energy wind environments with the dominance of linear and transverse dunes. Regions of high-energy wind environments occur in the south of the country and exhibit evidence of deflation rather than accumulation with the occurrence of migratory crescentic dunes. Analysis of the sand drift potentials and their directions help us to interpret the formation of major sand seas in Egypt. The pattern of sand drift potential/direction suggests that the sands in these seas might be inherited from exogenous sources.
17. Insect drift over the northern Arabian Sea in early summer
Digital Repository Service at National Institute of Oceanography (India)
Pathak, S.C.; Kulshrestha, V.; Choubey, A.K.; Parulekar, A.H.
,301 insects belonging to 8 different orders, 47 families and 173 species were trapped. Of these, Hymenoptera was represented by the largest number (1082), which was followed by Hemiptera (1586), Diptera (552), Coleoptera (51), Neuroptera (10), Trichoptera (03...
18. Construction update and drift velocity calibration for the CLAS drift chamber system
International Nuclear Information System (INIS)
Mestayer, M.D.; Barbosa, F.J.; Bonneau, P.; Burtin, E.; Christo, S.; Doolittle, G.; Dytman, S.A.; Gilfoyle, G.P.; Hyde-Wright, C.E.; Klein, A.; Kossov, M.V.; Kuhn, S.E.; Magahiz, R.; Miskimen, R.A.; Murphy, L.Y.; O'Meara, J.E.; Pyron, T.D.; Qin, L.; Raue, B.A.; Schumacher, R.A.; Tuzel, W.; Weinstein, L.B.; Yegneswaran, A.
1995-01-01
We briefly describe the drift chamber system for the CLAS detector at CEBAF, concentrating on the method which will be used to calibrate the drift velocity function. We identify key features of the function which should apply to any small-cell drift chamber geometry in which the cathode and anode surfaces are wires. Using these ideas, we describe a simple method to compensate for variations in the drift velocity function due to environmental changes. (orig.)
19. Construction update and drift velocity calibration for the CLAS drift chamber system
Energy Technology Data Exchange (ETDEWEB)
Mestayer, M.D. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Barbosa, F.J. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Bonneau, P. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Burtin, E. [University of South Carolina, Columbia, SC (United States); Christo, S. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Doolittle, G. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Dytman, S.A. [University of Pittsburg, Pittsburg, PA (United States); Gilfoyle, G.P. [University of Richmond, Richmond, VA (United States); Hyde-Wright, C.E. [Old Dominion University, Norfolk, VA (United States); Klein, A. [Old Dominion University, Norfolk, VA (United States); Kossov, M.V. [Christopher Newport University, Newport News, VA (United States); Kuhn, S.E. [Old Dominion University, Norfolk, VA (United States); Magahiz, R. [Carnegie-Mellon Univ., Pittsburgh, PA (United States); Miskimen, R.A. [University of Massachussetts, Amherst, MA (United States); Murphy, L.Y. [CE Saclay, Gif sur Yvette (France); OMeara, J.E. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Pyron, T.D. [Old Dominion University, Norfolk, VA (United States); Qin, L. [Old Dominion University, Norfolk, VA (United States); Raue, B.A. [Old Dominion University, Norfolk, VA (United States); Schumacher, R.A. [Carnegie-Mellon Univ., Pittsburgh, PA (United States); Tuzel, W. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Weinstein, L.B. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States); Yegneswaran, A. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States)
1995-12-11
We briefly describe the drift chamber system for the CLAS detector at CEBAF, concentrating on the method which will be used to calibrate the drift velocity function. We identify key features of the function which should apply to any small-cell drift chamber geometry in which the cathode and anode surfaces are wires. Using these ideas, we describe a simple method to compensate for variations in the drift velocity function due to environmental changes. (orig.).
20. Electron drift time in silicon drift detectors: A technique for high precision measurement of electron drift mobility
International Nuclear Information System (INIS)
Castoldi, A.; Rehak, P.
1995-01-01
This paper presents a precise absolute measurement of the drift velocity and mobility of electrons in high resistivity silicon at room temperature. The electron velocity is obtained from the differential measurement of the drift time of an electron cloud in a silicon drift detector. The main features of the transport scheme of this class of detectors are: the high uniformity of the electron motion, the transport of the signal electrons entirely contained in the high-purity bulk, the low noise timing due to the very small anode capacitance (typical value 100 fF), and the possibility to measure different drift distances, up to the wafer diameter, in the same semiconductor sample. These features make the silicon drift detector an optimal device for high precision measurements of carrier drift properties. The electron drift velocity and mobility in a 10 kΩ cm NTD n-type silicon wafer have been measured as a function of the electric field in the range of possible operation of a typical drift detector (167--633 V/cm). The electron ohmic mobility is found to be 1394 cm 2 /V s. The measurement precision is better than 1%. copyright 1995 American Institute of Physics
1. Uma releitura da obra de Elisabeth Kubler-Ross
Directory of Open Access Journals (Sweden)
Selene Beviláqua Chaves Afonso
2013-09-01
Full Text Available Este artigo apresenta uma releitura de parte da obra de Elizabeth Ross, uma das autoras mais citadas sobre a questão da terminalidade da vida, do luto e do morrer. Sua obra tem sido de grande contribuição tanto para os profissionais de saúde como para pais, mães, filhos, parentes, leigos e religiosos que vivenciam o luto. Também tem sido alvo de controvérsias relacionadas a questões éticas e quanto a seu rigor científico. Os livros aqui comentados são: On death and dying (Sobre A morte e o morrer, de 1969; Questions and answers on death and dying (Perguntas e respostas sobre a morte e o morrer, de 1971; Living with death and dying(Vivendo com a morte e os moribundos, de 1981; On children and death (Sobre as crianças e a morte, de 1983; On life after death (Sobre a vida depois da morte, de 1991 e Life lessons (Lições de vida, de 2000.
2. Crevasse detection with GPR across the Ross Ice Shelf, Antarctica
Science.gov (United States)
Delaney, A.; Arcone, S.
2005-12-01
We have used 400-MHz ground penetrating radar (GPR) to detect crevasses within a shear zone on the Ross Ice Shelf, Antarctica, to support traverse operations. The transducer was attached to a 6.5-m boom and pushed ahead of an enclosed tracked vehicle. Profile speeds of 4.8-11.3 km / hr allowed real-time crevasse image display and a quick, safe stop when required. Thirty-two crevasses were located with radar along the 4.8 km crossing. Generally, crevasse radar images were characterized by dipping reflections above the voids, high-amplitude reflections originating from ice layers at the base of the snow-bridges, and slanting, diffracting reflections from near-vertical crevasse walls. New cracks and narrow crevasses (back-filling with bulldozed snow, afforded an opportunity to ground-truth GPR interpretations by comparing void size and snow-bridge geometry with the radar images. While second and third season radar profiles collected along the identical flagged route confirmed stability of the filled crevasses, those profiles also identified several new cracks opened by ice extension. Our experiments demonstrate capability of high-frequency GPR in a cold-snow environment for both defining snow layers and locating voids.
3. Predictive modelling of Ross River virus notifications in southeastern Australia.
Science.gov (United States)
Cutcher, Z; Williamson, E; Lynch, S E; Rowe, S; Clothier, H J; Firestone, S M
2017-02-01
Ross River virus (RRV) is a mosquito-borne virus endemic to Australia. The disease, marked by arthritis, myalgia and rash, has a complex epidemiology involving several mosquito species and wildlife reservoirs. Outbreak years coincide with climatic conditions conducive to mosquito population growth. We developed regression models for human RRV notifications in the Mildura Local Government Area, Victoria, Australia with the objective of increasing understanding of the relationships in this complex system, providing trigger points for intervention and developing a forecast model. Surveillance, climatic, environmental and entomological data for the period July 2000-June 2011 were used for model training then forecasts were validated for July 2011-June 2015. Rainfall and vapour pressure were the key factors for forecasting RRV notifications. Validation of models showed they predicted RRV counts with an accuracy of 81%. Two major RRV mosquito vectors (Culex annulirostris and Aedes camptorhynchus) were important in the final estimation model at proximal lags. The findings of this analysis advance understanding of the drivers of RRV in temperate climatic zones and the models will inform public health agencies of periods of increased risk.
4. Ghost Stories: Review of Ross Gibson's The Summer Exercises
Directory of Open Access Journals (Sweden)
Deane Williams
2010-03-01
Full Text Available Back
in
1986,
Ross
Gibson
was
interviewed
in
Filmnews
by
Adrian
Martin
and
Tina
Kaufman
about
his
experimental
short
essay
film
Camera
Natura
(1984. Accompanying
that
interview
was
a
photo
of
Gibson
‘on
location’
for
his
film,
wearing
a
hat
not
unlike
the
one
that
features
on
the
cover
of
his
new
book
The
Summer
Exercises.
Back
then
I
understood
the
hat
to
be
an
explorer’s,
someone
like
Charles
Sturt,
someone
whose
willingness
to
learn
from
his
environment
had
impressed
Gibson
in
fashioning
his
own
history
of
Australian
landscape
imaging.
Now
the
hat
looks
like
a
detective’s
or,
rather,
Marcel
Duchamp’s
rendering
of
a
detective’s
hat:
on
display,
ready
for
our
re‐consideration.
5. Seepage Model for PA Including Drift Collapse
International Nuclear Information System (INIS)
Li, G.; Tsang, C.
2000-01-01
The purpose of this Analysis/Model Report (AMR) is to document the predictions and analysis performed using the Seepage Model for Performance Assessment (PA) and the Disturbed Drift Seepage Submodel for both the Topopah Spring middle nonlithophysal and lower lithophysal lithostratigraphic units at Yucca Mountain. These results will be used by PA to develop the probability distribution of water seepage into waste-emplacement drifts at Yucca Mountain, Nevada, as part of the evaluation of the long term performance of the potential repository. This AMR is in accordance with the ''Technical Work Plan for Unsaturated Zone (UZ) Flow and Transport Process Model Report'' (CRWMS M andO 2000 [153447]). This purpose is accomplished by performing numerical simulations with stochastic representations of hydrological properties, using the Seepage Model for PA, and evaluating the effects of an alternative drift geometry representing a partially collapsed drift using the Disturbed Drift Seepage Submodel. Seepage of water into waste-emplacement drifts is considered one of the principal factors having the greatest impact of long-term safety of the repository system (CRWMS M andO 2000 [153225], Table 4-1). This AMR supports the analysis and simulation that are used by PA to develop the probability distribution of water seepage into drift, and is therefore a model of primary (Level 1) importance (AP-3.15Q, ''Managing Technical Product Inputs''). The intended purpose of the Seepage Model for PA is to support: (1) PA; (2) Abstraction of Drift-Scale Seepage; and (3) Unsaturated Zone (UZ) Flow and Transport Process Model Report (PMR). Seepage into drifts is evaluated by applying numerical models with stochastic representations of hydrological properties and performing flow simulations with multiple realizations of the permeability field around the drift. The Seepage Model for PA uses the distribution of permeabilities derived from air injection testing in niches and in the cross drift to
6. Autoresonant control of drift waves
DEFF Research Database (Denmark)
Shagalov, A.G.; Rasmussen, Jens Juul; Naulin, Volker
2017-01-01
The control of nonlinear drift waves in a magnetized plasmas column has been investigated. The studies are based on the Hasegawa–Mima model, which is solved on a disk domain with radial inhomogeneity of the plasma density. The system is forced by a rotating potential with varying frequency defined...... on the boundary. To excite and control the waves we apply the autoresonant effect, taking place when the amplitude of the forcing exceeds a threshold value and the waves are phase-locked with the forcing. We demonstrate that the autoresonant approach is applicable for excitation of a range of steady nonlinear...... waves of the lowest azimuthal mode numbers and for controlling their amplitudes and phases. We also demonstrate the excitation of zonal flows (m = 0 modes), which are controlled via the forced modes....
7. Single wire drift chamber design
International Nuclear Information System (INIS)
Krider, J.
1987-01-01
This report summarizes the design and prototype tests of single wire drift chambers to be used in Fermilab test beam lines. The goal is to build simple, reliable detectors which require a minimum of electronics. Spatial resolution should match the 300 μm rms resolution of the 1 mm proportional chambers that they will replace. The detectors will be used in beams with particle rates up to 20 KHz. Single track efficiency should be at least 99%. The first application will be in the MT beamline, which has been designed for calibration of CDF detectors. A set of four x-y modules will be used to track and measure the momentum of beam particles
8. Drift effects in CANDU reactors
International Nuclear Information System (INIS)
Koclas, J.; Roy, R.; Marleau, G.
1993-01-01
The diffusion equation is an approximation to the transport equation which relies on the validity of Fick's law. Since this law is not explicitly integrated in the transport equation it can only be derived approximately using homogenization theories. However, such homogenization theories state that when the cell is not symmetric Fick's law breaks down due to the presence of an additional term to the neutron current, called the drift term. In fact, this term can be interpreted as a transport correction to Fick's law which tends to increase the neutron current in a direction opposite to that specified by the flux gradient. In this paper, we investigate how the presence of asymmetric liquid zone controllers will modify the flux distribution inside a CANDU core. 5 refs., 2 figs., 1 tab
9. Energy drift in reversible time integration
International Nuclear Information System (INIS)
McLachlan, R I; Perlmutter, M
2004-01-01
Energy drift is commonly observed in reversible integrations of systems of molecular dynamics. We show that this drift can be modelled as a diffusion and that the typical energy error after time T is O(√T). (letter to the editor)
10. TBV 361 RESOLUTION ANALYSIS: EMPLACEMENT DRIFT ORIENTATION
International Nuclear Information System (INIS)
Lin, M.; Kicker, D.C.; Sellers, M.D.
1999-01-01
The purpose of this To Be Verified/To Be Determined (TBX) resolution analysis is to release ''To Be Verified'' (TBV)-361 related to the emplacement drift orientation. The system design criterion in ''Subsurface Facility System Description Document'' (CRWMS M andO 1998a, p.9) specifies that the emplacement drift orientation relative to the dominant joint orientations should be at least 30 degrees. The specific objectives for this analysis include the following: (1) Collect and evaluate key block data developed for the repository host horizon rock mass. (2) Assess the dominant joint orientations based on available fracture data. (3) Document the maximum block size as a function of drift orientation. (4) Assess the applicability of the drift orientation/joint orientation offset criterion in the ''Subsurface Facility System Description Document'' (CRWMS M andO 1998a, p.9). (5) Consider the effects of seepage on drift orientation. (6) Verify that the viability assessment (VA) drift orientation complies with the drift orientation/joint orientation offset criterion, or provide justifications and make recommendations for modifying the VA emplacement drift layout. In addition to providing direct support to the System Description Document (SDD), the release of TBV-361 will provide support to the Repository Subsurface Design Department. The results from this activity may also provide data and information needs to support the MGR Requirements Department, the MGR Safety Assurance Department, and the Performance Assessment Organization
11. Silicon drift detectors, present and future prospects
Science.gov (United States)
Takahashi, J.; Bellwied, R.; Beuttenmuller, R.; Caines, H.; Chen, W.; Dyke, H.; Hoffmann, G. W.; Humanic, T.; Kotov, I.; Kuczewski, P.; Leonhardt, W.; Li, Z.; Lynn, D.; Minor, R.; Munhoz, M.; Ott, G.; Pandey, S. U.; Schambach, J.; Soja, R.; Sugarbaker, E.; Willson, R. M.
2001-04-01
Silicon drift detectors provide unambiguous two-dimensional position information for charged particle detection with a single detector layer. A large area silicon drift detector was developed for the inner tracking detector of the STAR experiment at RHIC. In this paper, we discuss the lessons learned and the future prospects of this technology.
12. FIELD INVESTIGATION OF THE DRIFT SHADOW
International Nuclear Information System (INIS)
G.W. Su; T.J. Kneafsey
2006-01-01
A drift shadow is an area immediately beneath an underground void that, in theory, will be relatively drier than the surrounding rock mass. Numerical and analytical models of water flow through unsaturated rock predict the existence of a drift shadow, but field tests confirming the existence of the drift shadow have yet to be performed. Proving the existence of drift shadows and understanding their hydrologic and transport characteristics could provide a better understanding of how contaminants move in the subsurface if released from waste emplacement drifts such as the proposed nuclear waste repository at Yucca Mountain, Nevada. We describe the field program that will be used to investigate the existence of a drift shadow--and the corresponding hydrological process at the Hazel-Atlas silica-sand mine located at the Black Diamond Mines Regional Preserve in Antioch, California. The location and configuration of this mine makes it an excellent site to observe and measure drift shadow characteristics. The mine is located in a porous sandstone unit of the Domengine formation, an approximately 230 meter thick series of interbedded Eocene-age shales, coals, and massive-bedded sandstones. The mining method used at the mine required the development of two parallel drifts, one above the other, driven along the strike of the mined sandstone stratum. This configuration provides the opportunity to introduce water into the rock mass in the upper drift and to observe and measure its flow around the underlying drift. The passive and active hydrologic tests to be performed are described. In the passive method, cores will be obtained in a radial pattern around a drift and will be sectioned and analyzed for in-situ water content using a gravimetric technique, as well as analyzed for chemistry. With the active hydrologic test, water will be introduced into the upper drift of the two parallel drifts and the flow of the water will be tracked as it passes near the bottom drift
13. Role of drifts in diffusive shock acceleration
International Nuclear Information System (INIS)
Decker, R.B.
1988-01-01
The role played by shock-associated drifts during the diffusive acceleration of charged particles at collisionless MHD shocks is evaluated. In the rest frame of the shock, the total energy gained by a particle is shown to result from two coupled acceleration mechanisms, the usual first-order Fermi mechanism and the drift mechanism. When averaged over a distribution of particles, the ratio of the drift-associated energy gain to the total energy is found to be independent of the total energy at a given theta1 (the angle between the shock normal and the unperturbed upstream magnetic field) in agreement with theoretical predictions. No evidence is found for drift-associated deceleration, suggesting that drifts always augment acceleration. 35 references
14. Drift reversal capability in helical systems
International Nuclear Information System (INIS)
Yokoyama, M.; Itoh, K.; Okamura, S.
2002-10-01
The maximum-J (J is the second adiabatic invariant) capability, i.e., the drift reversal capability, is examined in quasi-axisymmetric (QAS) stellarators and quasi-poloidally symmetric (QPS) stellarators as a possible mechanism for turbulent transport suppression. Due to the existence of non-axisymmetry of the magnetic field strength in QAS configurations, a local maximum of J is created to cause the drift reversal. The increase of magnetic shear in finite beta equilibria also has favorable effect in realizing the drift reversal. The radial variation of the uniform magnetic field component plays a crucial role for the drift reversal in a QPS configuration. Thus, the drift reversal capability and its external controllability are demonstrated for QAS and QPS stellarators, by which the impact of magnetic configuration on turbulent transport can be studied in experiments. (author)
15. Drift reversal capability in helical systems
International Nuclear Information System (INIS)
Yokoyama, M.; Itoh, K.; Okamura, S.; Matsuoka, K.; Nakajima, N.; Itoh, S.-I.; Neilson, G.H.; Zarnstorff, M.C.; Rewoldt, G.
2003-01-01
The maximum-J (J is the second adiabatic invariant) capability, i.e., the drift reversal capability, is examined in quasi-axisymmetric (QAS) stellarators and quasi-poloidally symmetric (QPS) stellarators as a possible mechanism for turbulent transport suppression. Due to the existence of non-axisymmetry of the magnetic field strength in QAS configurations, a local maximum of J is created to cause the drift reversal. The increase of magnetic shear in finite beta equilibria also has favorable effect in realizing the drift reversal. The radial variation of the uniform magnetic field component plays a crucial role for the drift reversal in a QPS configuration. Thus, the drift reversal capability and its external controllability are demonstrated for QAS and QPS stellarators, by which the impact of magnetic configuration on turbulent transport can be studied in experiments. (author)
16. Ground Control for Emplacement Drifts for LA
International Nuclear Information System (INIS)
Y. Sun
2004-01-01
The purpose of this calculation is to analyze the stability of repository emplacement drifts during the preclosure period, and to provide a final ground support method for emplacement drifts for the License Application (LA). The scope of the work includes determination of input parameter values and loads, selection of appropriate process and methods for the calculation, application of selected methods, such as empirical or analytical, to the calculation, development and execution of numerical models, and evaluation of results. Results from this calculation are limited to use for design of the emplacement drifts and the final ground support system installed in these drifts. The design of non-emplacement openings and their ground support systems is covered in the ''Ground Control for Non-Emplacement Drifts for LA'' (BSC 2004c)
17. Dissipative drift instability in dusty plasma
Directory of Open Access Journals (Sweden)
Nilakshi Das
2012-03-01
Full Text Available An investigation has been done on the very low-frequency electrostatic drift waves in a collisional dusty plasma. The dust density gradient is taken perpendicular to the magnetic field B0⃗, which causes the drift wave. In this case, low-frequency drift instabilities can be driven by E1⃗×B0⃗ and diamagnetic drifts, where E1⃗ is the perturbed electric field. Dust charge fluctuation is also taken into consideration for our study. The dust- neutral and ion-neutral collision terms have been included in equations of motion. It is seen that the low-frequency drift instability gets damped in such a system. Both dust charging and collision of plasma particles with the neutrals may be responsible for the damping of the wave. Both analytical and numerical techniques have been used while developing the theory.
18. Drift velocity and pressure monitoring of the CMS muon drift chambers
CERN Document Server
Sonnenschein, Lars
2011-01-01
The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers. The differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest drift velocity monitoring results are discussed.
19. Drift velocity and pressure monitoring of the CMS muon drift chambers
CERN Document Server
Sonnenschein, Lars
2010-01-01
The drift velocity in drift tubes of the CMS muon chambers is a key parameter for the muon track reconstruction and trigger. It needs to be monitored precisely in order to detect any deviation from its nominal value. A change in absolute pressure, a variation of the gas admixture or a contamination of the chamber gas by air affect the drift velocity. Furthermore, the temperature and magnetic field influence its value. First data, taken with a dedicated Velocity Drift Chamber (VDC) built by RWTH Aachen IIIA are presented. Another important parameter to be monitored is the pressure inside the muon drift tube chambers because the drift velocity depends on it. Furthermore the differential pressure must not exceed a certain value and the absolute pressure has to be kept slightly above ambient pressure to prevent air from entering into the muon drift tube chambers in case of a leak. Latest pressure monitoring results are discussed.
20. Field investigation of the drift shadow
International Nuclear Information System (INIS)
Su, Grace W.; Kneafsey, Timothy J.; Ghezzehei, Teamrat A.; Marshall, Brian D.; Cook, Paul J.
2005-01-01
A drift shadow is an area immediately beneath an underground void that, in theory, will be relatively drier than the surrounding rockmass. Numerical and analytical models of water flow through unsaturated rock predict the existence of a drift shadow, but field tests confirming its existence have yet to be performed. Proving the existence of drift shadows and understanding their hydrologic and transport characteristics could provide a better understanding of how contaminants move in the subsurface if released from waste emplacement drifts such as the proposed nuclear waste repository at Yucca Mountain, Nevada. We describe the field program that will be used to investigate the existence of a drift shadow and the corresponding hydrological process at the Hazel-Atlas silica-sandmine located at the Black Diamond Mines Regional Preserve in Antioch, California. The location and configuration of this mine makes it an excellent site to observe and measure drift shadow characteristics. The mine is located in a porous sandstone unit of the Domengine Formation, an approximately 230 meter thick series of interbedded Eocene-age shales, coals, and massive-bedded sandstones. The mining method used at the mine required the development of two parallel drifts, one above the other, driven along the strike of the mined sandstone stratum. This configuration provides the opportunity to introduce water into the rockmass in the upper drift and to observe and measure its flow around the underlying drift. The passive and active hydrologic tests to be performed are described. In the passive method, cores will be obtained in a radial pattern around a drift and will be sectioned and analyzed for in-situ water content and chemical constituents. With the active hydrologic test, water will be introduced into the upper drift of the two parallel drifts and the flow of the water will be tracked as it passes near the bottom drift. Tensiometers, electrical resistance probes, neutron probes, and ground
1. Clinical Outcomes Following the Ross Procedure in Adults: A 25-Year Longitudinal Study.
Science.gov (United States)
Martin, Elisabeth; Mohammadi, Siamak; Jacques, Frederic; Kalavrouziotis, Dimitri; Voisine, Pierre; Doyle, Daniel; Perron, Jean
2017-10-10
Very few reports of long-term outcomes of patients who underwent the Ross procedure have been published. The authors reviewed their 25-year experience with the Ross procedure with the aim of defining very-long-term survival and factors associated with Ross-related failure. Between January 1990 and December 2014, the Ross procedure was performed in 310 adults (mean age 40.8 years) at a single institution. All patients were prospectively added to a dedicated cardiac surgery registry. Complete post-operative clinical examination and history were obtained, and transthoracic echocardiography was performed according to a standardized protocol. There was no loss to follow-up. Median follow-up was 15.1 years and up to 25 years. Bicuspid aortic valve was diagnosed in 227 patients (73.2%), and the most common indication for surgery was aortic stenosis (n = 225 [72.6%]). Freedom from any Ross-related reintervention was 92.9% and 70.1% at 10 and 20 years, respectively. Independent risk factors for pulmonary autograft degeneration were pre-operative large aortic annulus (hazard ratio: 1.1; p = 0.01), pre-operative aortic insufficiency (hazard ratio: 2.7; p = 0.002), and concomitant replacement of the ascending aorta (hazard ratio: 7.7; p = 0.0003). There were 4 hospital deaths (1.3%), and overall survival at 10 and 20 years was 94.1% and 83.6%, respectively. Long-term survival was not significantly different in patients who required Ross-related reintervention (log-rank p = 0.70). However, compared with the general population, survival was significantly lower in patients following the Ross procedure when matched on age and sex (p Ross procedure was associated with excellent long-term valvular outcomes and survival, regardless of the need for reintervention. Adults presenting with aortic insufficiency or a dilated aortic annulus or ascending aorta were at greater risk for reintervention. Unlike previous reports, long-term survival was lower in Ross
2. Drift-modeling and monitoring comparisons
International Nuclear Information System (INIS)
Chen, N.C.J.; Hanna, S.R.
1977-01-01
Congress is looking into the conglomeration of nuclear reactors into energy centers of limited area. Drift from cooling towers can corrode and damage structures in the immediate vicinity of the towers, cause a public nuisance if located near parking lots or high-density traffic areas, and endanger local vegetation. The estimation of salt deposition has relied primarily on predictions from a variety of models, with very few direct measurements. One of the major efforts in our program is to evaluate the assumptions, limitations, and applicabilities of various analytical models for drift deposition prediction. Several drift deposition models are compared using a set of standard input conditions. The predicted maximum drift deposition differs by two orders of magnitude, and the downwind locations of the maximum differ by one order of magnitude. The discrepancies are attributed mainly to different assumptions in the models regarding the initial effective height of the droplets. Current programs in which drift characteristics at the tower mouth and drift deposition downwind of the tower are being measured are summarized. At the present time, drift deposition measurements, sufficiently comprehensive for model verifications, are unavailable. Hopefully, the Chalk Point Program will satisfy this need
3. Seepage into drifts with mechanical degradation
International Nuclear Information System (INIS)
Li, Guomin; Tsang, Chin-Fu
2002-01-01
Seepage into drifts in unsaturated tuff is an important issue for the long-term performance of the potential nuclear waste repository at Yucca Mountain, Nevada. Drifts in which waste packages will potentially be emplaced are subject to degradation in the form of rockfall from the drift ceiling induced by stress relief, seismic, or thermal effects. The objective of this study is to calculate seepage rates for various drift-degradation scenarios and for different values of percolation flux for the Topopah Spring middle nonlithophysal (Tptpmn) and the Topopah Spring lower lithophysal (Tptpll) units. Seepage calculations are conducted by (1) defining a heterogeneous permeability model on the drift scale that is consistent with field data, (2) selecting calibrated parameters associated with the Tptpmn and Tptpll units, and (3) simulating seepage on detailed degraded-drift profiles, which were obtained from a separate rock mechanics engineering analysis. The simulation results indicate (1) that the seepage threshold (i.e., the percolation flux at which seepage first occurs) is not significantly changed by drift degradation, and (2) the degradation-induced increase in seepage above the threshold is influenced more by the shape of the cavity created by rockfall than the rockfall volume
4. Nonlinear Gyrokinetic Theory With Polarization Drift
International Nuclear Information System (INIS)
Wang, L.; Hahm, T.S.
2010-01-01
A set of the electrostatic toroidal gyrokinetic Vlasov equation and the Poisson equation, which explicitly includes the polarization drift, is derived systematically by using Lie-transform method. The polarization drift is introduced in the gyrocenter equations of motion, and the corresponding polarization density is derived. Contrary to the wide-spread expectation, the inclusion of the polarization drift in the gyrocenter equations of motion does not affect the expression for the polarization density significantly. This is due to modification of the gyrocenter phase-space volume caused by the electrostatic potential [T. S. Hahm, Phys. Plasmas 3, 4658 (1996)].
5. Pixelated CdZnTe drift detectors
DEFF Research Database (Denmark)
Kuvvetli, Irfan; Budtz-Jørgensen, Carl
2005-01-01
A technique, the so-called Drift Strip Method (DSM), for improving the CdZnTe detector energy response to hard X-rays and gamma-rays was applied as a pixel geometry. First tests have confirmed that this detector type provides excellent energy resolution and imaging performance. We specifically...... report on the performance of 3 mm thick prototype CZT drift pixel detectors fabricated using material from eV-products. We discuss issues associated with detector module performance. Characterization results obtained from several prototype drift pixel detectors are presented. Results of position...
6. Computer controlled drifting of Si(Li) detectors
International Nuclear Information System (INIS)
Landis, D.A.; Wong, Y.K.; Walton, J.T.; Goulding, F.S.
1989-01-01
A relatively inexpensive computer-controlled system for performing the drift process used in fabricating Si(Li) detectors is described. The system employs a small computer to monitor the leakage current, applied voltage and temperature on eight individual drift stations. The associated computer program initializes the drift process, monitors the drift progress and then terminates the drift when an operator set drift time has elapsed. The improved control of the drift with this system has been well demonstrated over the past three years in the fabrication of a variety of Si(Li) detectors. A few representative system responses to detector behavior during the drift process are described
7. Unintended Positional Drift and Its Potential Solutions
DEFF Research Database (Denmark)
Nilsson, Niels Christian; Serafin, Stefania; Nordahl, Rolf
2013-01-01
many users unintentionally move forward while walking in place. We refer to this phenomenon accidental movement as Unintended Positional Drift. The poster presents evidence of the phenomenon's existence and subsequently discusses different design solutions which potentially could circumvent the problem....
8. CROSS DRIFT ALCOVE/NICHE UTILITIES ANALYSIS
International Nuclear Information System (INIS)
S. Goodin
1999-01-01
The purpose of this analysis is to provide the design basis and general arrangement requirements of the non-potable water, waste water, compressed air and ventilation (post excavation) utilities required in support of the Cross Drift alcoves and niches
9. Travelling fronts in stochastic Stokes’ drifts
KAUST Repository
Blanchet, Adrien; Dolbeault, Jean; Kowalczyk, Michał
2008-01-01
By analytical methods we study the large time properties of the solution of a simple one-dimensional model of stochastic Stokes' drift. Semi-explicit formulae allow us to characterize the behaviour of the solutions and compute global quantities
10. Self-shielding flex-circuit drift tube, drift tube assembly and method of making
Science.gov (United States)
Jones, David Alexander
2016-04-26
The present disclosure is directed to an ion mobility drift tube fabricated using flex-circuit technology in which every other drift electrode is on a different layer of the flex-circuit and each drift electrode partially overlaps the adjacent electrodes on the other layer. This results in a self-shielding effect where the drift electrodes themselves shield the interior of the drift tube from unwanted electro-magnetic noise. In addition, this drift tube can be manufactured with an integral flex-heater for temperature control. This design will significantly improve the noise immunity, size, weight, and power requirements of hand-held ion mobility systems such as those used for explosive detection.
11. Hemodynamic outcomes of the Ross procedure versus other aortic valve replacement: a systematic review and meta-analysis.
Science.gov (United States)
Um, Kevin J; McCLURE, Graham R; Belley-Cote, Emilie P; Gupta, Saurabh; Bouhout, Ismail; Lortie, Hugo; Alraddadi, Hatim; Alsagheir, Ali; Bossard, Matthias; McINTYRE, William F; Lengyel, Alexandra; Eikelboom, John W; Ouzounian, Maral; Chu, Michael W; Parry, Dominic; El-Hamamsy, Ismail; Whitlock, Richard P
2018-01-09
Life expectancy in young adults undergoing mechanical or bioprosthetic aortic valve replacement (AVR) may be reduced by up to 20 years compared to age matched controls. The Ross procedure is a durable, anticoagulation-sparing alternative. We performed a systematic review and meta-analysis to compare the valve hemodynamics of the Ross procedure versus other AVR. We searched Cochrane CENTRAL, MEDLINE and EMBASE from inception to February 2017 for randomized controlled trials (RCTs) and observational studies (n≥10 Ross). Independently and in duplicate, we performed title and abstract screening, full-text eligibility assessment, and data collection. We evaluated the risk of bias with the Cochrane and CLARITY tools, and the quality of evidence with the GRADE framework. We identified 2 RCTs and 13 observational studies that met eligibility criteria (n=1,412). In observational studies, the Ross procedure was associated with a lower mean aortic gradient at discharge (MD -9 mmHg, 95% CI [-13, -5], pRoss procedure was associated with a lower mean gradient at latest follow-up (MD -15 mmHg, 95% CI [-32, 2], p=0.08, I2=99%). The mean pulmonic gradient for the Ross procedure was 18.0 mmHg (95% CI [16, 20], pRoss procedure was associated with better aortic valve hemodynamics. Future studies should evaluate the impact of the Ross procedure on exercise capacity and quality of life.
12. Strange Attractors in Drift Wave Turbulence
International Nuclear Information System (INIS)
Lewandowski, J.L.V.
2003-01-01
A multi-grid part-in-cell algorithm for a shearless slab drift wave model with kinetic electrons is presented. The algorithm, which is based on an exact separation of adiabatic and nonadiabatic electron responses, is used to investigate the presence of strange attractors in drift wave turbulence. Although the simulation model has a large number of degrees of freedom, it is found that the strange attractor is low-dimensional and that it is strongly affected by dissipative (collisional) effects
13. SEEPAGE MODEL FOR PA INCLUDING DRIFT COLLAPSE
International Nuclear Information System (INIS)
C. Tsang
2004-01-01
The purpose of this report is to document the predictions and analyses performed using the seepage model for performance assessment (SMPA) for both the Topopah Spring middle nonlithophysal (Tptpmn) and lower lithophysal (Tptpll) lithostratigraphic units at Yucca Mountain, Nevada. Look-up tables of seepage flow rates into a drift (and their uncertainty) are generated by performing numerical simulations with the seepage model for many combinations of the three most important seepage-relevant parameters: the fracture permeability, the capillary-strength parameter 1/a, and the percolation flux. The percolation flux values chosen take into account flow focusing effects, which are evaluated based on a flow-focusing model. Moreover, multiple realizations of the underlying stochastic permeability field are conducted. Selected sensitivity studies are performed, including the effects of an alternative drift geometry representing a partially collapsed drift from an independent drift-degradation analysis (BSC 2004 [DIRS 166107]). The intended purpose of the seepage model is to provide results of drift-scale seepage rates under a series of parameters and scenarios in support of the Total System Performance Assessment for License Application (TSPA-LA). The SMPA is intended for the evaluation of drift-scale seepage rates under the full range of parameter values for three parameters found to be key (fracture permeability, the van Genuchten 1/a parameter, and percolation flux) and drift degradation shape scenarios in support of the TSPA-LA during the period of compliance for postclosure performance [Technical Work Plan for: Performance Assessment Unsaturated Zone (BSC 2002 [DIRS 160819], Section I-4-2-1)]. The flow-focusing model in the Topopah Spring welded (TSw) unit is intended to provide an estimate of flow focusing factors (FFFs) that (1) bridge the gap between the mountain-scale and drift-scale models, and (2) account for variability in local percolation flux due to
14. Ponderomotive modification of drift tearing modes
International Nuclear Information System (INIS)
Urquijo, G.; Singh, R.; Sen, A.
1997-01-01
The linear characteristics of drift tearing modes are investigated in the presence of a significant background of radio-frequency (RF) waves in the ion cyclotron range of frequencies. The ponderomotive force, arising from the radial gradients in the RF field energy, is found to significantly modify the inner layer solutions of the drift tearing modes. It can have a stabilizing influence, even at moderate RF powers, provided the field energy has a decreasing radial profile at the mode rational surface. (author)
15. Unstable universal drift eigenmodes in toroidal plasmas
International Nuclear Information System (INIS)
Cheng, C.Z.; Chen, L.
1980-01-01
The eigenmode equation describing ballooning collisionless drift instabilities is analyzed both analytically and numerically. A new branch of eigenmodes, which corresponds to quasi-bound states due to toroidal coupling effects such as ion delB drifts, is shown to be destabilized by electron Landau damping for typical tokamak parameters. This branch cannot be understood by the strong coupling approximation. However, the slab-like (Pearlstein--Berk-type) branch is found to remain stable and experience enhanced shear damping
16. Effects of Fault Displacement on Emplacement Drifts
International Nuclear Information System (INIS)
Duan, F.
2000-01-01
The purpose of this analysis is to evaluate potential effects of fault displacement on emplacement drifts, including drip shields and waste packages emplaced in emplacement drifts. The output from this analysis not only provides data for the evaluation of long-term drift stability but also supports the Engineered Barrier System (EBS) process model report (PMR) and Disruptive Events Report currently under development. The primary scope of this analysis includes (1) examining fault displacement effects in terms of induced stresses and displacements in the rock mass surrounding an emplacement drift and (2 ) predicting fault displacement effects on the drip shield and waste package. The magnitude of the fault displacement analyzed in this analysis bounds the mean fault displacement corresponding to an annual frequency of exceedance of 10 -5 adopted for the preclosure period of the repository and also supports the postclosure performance assessment. This analysis is performed following the development plan prepared for analyzing effects of fault displacement on emplacement drifts (CRWMS M and O 2000). The analysis will begin with the identification and preparation of requirements, criteria, and inputs. A literature survey on accommodating fault displacements encountered in underground structures such as buried oil and gas pipelines will be conducted. For a given fault displacement, the least favorable scenario in term of the spatial relation of a fault to an emplacement drift is chosen, and the analysis is then performed analytically. Based on the analysis results, conclusions are made regarding the effects and consequences of fault displacement on emplacement drifts. Specifically, the analysis will discuss loads which can be induced by fault displacement on emplacement drifts, drip shield and/or waste packages during the time period of postclosure
17. Drift waves in a weakly ionized plasma
DEFF Research Database (Denmark)
Popovic, M.; Melchior, H.
1968-01-01
A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated.......A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated....
18. Aortic Valve Replacement and the Ross Operation in Children and Young Adults.
Science.gov (United States)
Sharabiani, Mansour T A; Dorobantu, Dan M; Mahani, Alireza S; Turner, Mark; Peter Tometzki, Andrew J; Angelini, Gianni D; Parry, Andrew J; Caputo, Massimo; Stoica, Serban C
2016-06-21
19. Modeling the cod larvae drift in the Bornholm Basin in summer 1994
DEFF Research Database (Denmark)
Hinrichsen, H.H.; Lehmann, A.; St. John, Michael
1997-01-01
, initial fields of temperature, salinity and cod larvae concentration for the Bornholm Basin were constructed by objective analysis using observations taken during a research survey in early July, 1994. Outside the Bornholm Basin generalized hydrographic features of the Baltic Sea were utilized....... In general, most of the hydrographic features observed during the second research cruise are correctly simulated, with variations mainly attributed to the prescribed initial conditions outside the Bornholm Basin. Results from larval sampling during the second cruise could not entirely confirm the modeled......A combined 3-D physical oceanographic model and a field sampling program was performed in July and August 1994 to investigate the potential drift of larval Baltic cod from the center of spawning effort in the Bornholm Basin, Baltic Sea. The goal of this exercise was to predict the drift...
20. Calibration of the CMS Drift Tube Chambers and Measurement of the Drift Velocity with Cosmic Rays
CERN Document Server
2010-01-01
This paper describes the calibration procedure for the drift tubes of the CMS barrel muon system and reports the main results obtained with data collected during a high statistics cosmic ray data-taking period. The main goal of the calibration is to determine, for each drift cell, the minimum time delay for signals relative to the trigger, accounting for the drift velocity within the cell. The accuracy of the calibration procedure is influenced by the random arrival time of cosmic muons. A more refined analysis of the drift velocity was performed during the offline reconstruction phase, which takes into account this feature of cosmic ray events.
1. Drift pumice in the Indian and South Atlantic oceans
International Nuclear Information System (INIS)
Frick, C.; Kent, L.E.
1984-01-01
Sixty-three samples of drift pumice, collected at the coasts of South Africa, East Africa, Madagascar, Mauritius, the Cocos Islands, Australia, Indonesia, Brazil, Marion Island and Bouvet Island, were investigated petrographically and geochemically with a view to establishing the possible source areas. Geochemically five distinct groups could be distinguished and some could be liked to specific eruptions in the Indian, Atlantic and Pacific oceans. Group A pumice originated from a submarine eruption off Zavodovski Island in the South Sandwich Island Group in 1962. The pumice in Group B occurs mainly on the beaches bordering the Atlantic Ocean, and was found on the west coast of South Africa, on the sea floor south-west of South Africa, and in Brazil. The source of this group is unknown, but all the evidence indicates that it must have been from the Mid-Atlantic Ridge in the South Atlantic Ocean. The Group C pumice was found in the southern Indian Ocean, probably from the Mid-Indian Ridge. The fourth group originated from a submarine eruption along the Tonga Trench in the Pacific Ocean. Group E, which is by far the most homogeneous, includes samples from Australia, the Indian Ocean islands, East and South Africa and samples of the undisputed Krakatoan origin. Specimens from the Krakatoan eruption are still the most abundant type of drift pumice that can be found
2. Applicability of TASS/SMR using drift flux model for SMART LOCA analysis
Energy Technology Data Exchange (ETDEWEB)
Chung, Young-Jong, E-mail: [email protected]; Kim, Soo Hyung; Lee, Gyu Hyeung; Lee, Won Jae
2013-09-15
Highlights: • SMART plant and TASS/SMR code have been developed by KAERI. • TASS/SMR code adopts a drift flux model to consider relative velocity under two-phase condition. • Drift flux model in TASS/SMR is validated using separate effect test results. • Applicability of TASS/SMR using drift flux model for SMART LOCA analysis is confirmed. -- Abstract: Small reactors can apply to local power demands or remote areas. SMART, which can produce 90 MWe of electricity and 40,000 tons/day of sea-water desalination for a 100,000 population city, is a promising advanced integral type small reactor. The thermal hydraulic analysis code with a drift flux model, TASS/SMR, was developed for a conservative simulation of a small break loss of coolant accident in SMART. Taking into account SMART-specific inherent characteristics, the code adopts the Chexal–Lellouche correlation for a drift flux model. The capability of TASS/SMR code is validated using the results of the experimental data. The code predicts conservatively the void distribution compared with the experimental data. TASS/SMR calculation predicts reasonably major phenomena for the SBLOCA and is more conservative than or nearly the same as the results of the best estimated realistic system code, MARS. TASS/SMR code can be used for a SBLOCA analysis of SMART.
3. Applicability of TASS/SMR using drift flux model for SMART LOCA analysis
International Nuclear Information System (INIS)
Chung, Young-Jong; Kim, Soo Hyung; Lee, Gyu Hyeung; Lee, Won Jae
2013-01-01
Highlights: • SMART plant and TASS/SMR code have been developed by KAERI. • TASS/SMR code adopts a drift flux model to consider relative velocity under two-phase condition. • Drift flux model in TASS/SMR is validated using separate effect test results. • Applicability of TASS/SMR using drift flux model for SMART LOCA analysis is confirmed. -- Abstract: Small reactors can apply to local power demands or remote areas. SMART, which can produce 90 MWe of electricity and 40,000 tons/day of sea-water desalination for a 100,000 population city, is a promising advanced integral type small reactor. The thermal hydraulic analysis code with a drift flux model, TASS/SMR, was developed for a conservative simulation of a small break loss of coolant accident in SMART. Taking into account SMART-specific inherent characteristics, the code adopts the Chexal–Lellouche correlation for a drift flux model. The capability of TASS/SMR code is validated using the results of the experimental data. The code predicts conservatively the void distribution compared with the experimental data. TASS/SMR calculation predicts reasonably major phenomena for the SBLOCA and is more conservative than or nearly the same as the results of the best estimated realistic system code, MARS. TASS/SMR code can be used for a SBLOCA analysis of SMART
4. High summertime aerosol organic functional group concentrations from marine and seabird sources at Ross Island, Antarctica, during AWARE
Directory of Open Access Journals (Sweden)
J. Liu
2018-06-01
Full Text Available Observations of the organic components of the natural aerosol are scarce in Antarctica, which limits our understanding of natural aerosols and their connection to seasonal and spatial patterns of cloud albedo in the region. From November 2015 to December 2016, the ARM West Antarctic Radiation Experiment (AWARE measured submicron aerosol properties near McMurdo Station at the southern tip of Ross Island. Submicron organic mass (OM, particle number, and cloud condensation nuclei concentrations were higher in summer than other seasons. The measurements included a range of compositions and concentrations that likely reflected both local anthropogenic emissions and natural background sources. We isolated the natural organic components by separating a natural factor and a local combustion factor. The natural OM was 150 times higher in summer than in winter. The local anthropogenic emissions were not hygroscopic and had little contribution to the CCN concentrations. Natural sources that included marine sea spray and seabird emissions contributed 56 % OM in summer but only 3 % in winter. The natural OM had high hydroxyl group fraction (55 %, 6 % alkane, and 6 % amine group mass, consistent with marine organic composition. In addition, the Fourier transform infrared (FTIR spectra showed the natural sources of organic aerosol were characterized by amide group absorption, which may be from seabird populations. Carboxylic acid group contributions were high in summer and associated with natural sources, likely forming by secondary reactions.
5. Long-Term Outcomes of the Ross Procedure Versus Mechanical Aortic Valve Replacement: Propensity-Matched Cohort Study.
Science.gov (United States)
Mazine, Amine; David, Tirone E; Rao, Vivek; Hickey, Edward J; Christie, Shakira; Manlhiot, Cedric; Ouzounian, Maral
2016-08-23
The ideal aortic valve substitute in young and middle-aged adults remains unknown. We sought to compare the long-term outcomes of patients undergoing the Ross procedure and those receiving a mechanical aortic valve replacement (AVR). From 1990 to 2014, 258 patients underwent a Ross procedure and 1444 had a mechanical AVR at a single institution. Patients were matched into 208 pairs through the use of a propensity score. Mean age was 37.2±10.2 years, and 63% were male. Mean follow-up was 14.2±6.5 years. Overall survival was equivalent (Ross versus AVR: hazard ratio, 0.91, 95% confidence interval, 0.38-2.16; P=0.83), although freedom from cardiac- and valve-related mortality was improved in the Ross group (Ross versus AVR: hazard ratio, 0.22; 95% confidence interval, 0.034-0.86; P=0.03). Freedom from reintervention was equivalent after both procedures (Ross versus AVR: hazard ratio, 1.86; 95% confidence interval, 0.76-4.94; P=0.18). Long-term freedom from stroke or major bleeding was superior after the Ross procedure (Ross versus AVR: hazard ratio, 0.09; 95% confidence interval, 0.02-0.31; PRoss procedure and mechanical AVR. However, the Ross procedure was associated with improved freedom from cardiac- and valve-related mortality and a significant reduction in the incidence of stroke and major bleeding. In specialized centers, the Ross procedure represents an excellent option and should be considered for young and middle-aged adults undergoing AVR. © 2016 American Heart Association, Inc.
6. Estimates of Lagrangian particle transport by wave groups: forward transport by Stokes drift and backward transport by the return flow
Science.gov (United States)
van den Bremer, Ton S.; Taylor, Paul H.
2014-11-01
Although the literature has examined Stokes drift, the net Lagrangian transport by particles due to of surface gravity waves, in great detail, the motion of fluid particles transported by surface gravity wave groups has received considerably less attention. In practice nevertheless, the wave field on the open sea often has a group-like structure. The motion of particles is different, as particles at sufficient depth are transported backwards by the Eulerian return current that was first described by Longuet-Higgins & Stewart (1962) and forms an inseparable counterpart of Stokes drift for wave groups ensuring the (irrotational) mass balance holds. We use WKB theory to study the variation of the Lagrangian transport by the return current with depth distinguishing two-dimensional seas, three-dimensional seas, infinite depth and finite depth. We then provide dimensional estimates of the net horizontal Lagrangian transport by the Stokes drift on the one hand and the return flow on the other hand for realistic sea states in all four cases. Finally we propose a simple scaling relationship for the transition depth: the depth above which Lagrangian particles are transported forwards by the Stokes drift and below which such particles are transported backwards by the return current.
7. On the design and construction of drifting-mine test targets for sonar, radar and electro-optical detection experiments
NARCIS (Netherlands)
Dol, H.S.
2014-01-01
The timely detection of small hazardous objects at the sea surface, such as drifting mines, is challenging for ship-mounted sensor systems, both for underwater sensor systems like sonar and above-water sensor systems like radar and electro-optics (lidar, infrared/visual cameras). This is due to the
8. Coastal-Change and Glaciological Map of the Northern Ross Ice Shelf Area, Antarctica: 1962-2004
Science.gov (United States)
Ferrigno, Jane G.; Foley, Kevin M.; Swithinbank, Charles; Williams, Richard S.
2007-01-01
Changes in the area and volume of polar ice sheets are intricately linked to changes in global climate, and the resulting changes in sea level could severely impact the densely populated coastal regions on Earth. Melting of the West Antarctic part alone of the Antarctic ice sheet would cause a sea-level rise of approximately 6 meters (m). The potential sea-level rise after melting of the entire Antarctic ice sheet is estimated to be 65 m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). The mass balance (the net volumetric gain or loss) of the Antarctic ice sheet is highly complex, responding differently to different conditions in each region (Vaughan, 2005). In a review paper, Rignot and Thomas (2002) concluded that the West Antarctic ice sheet is probably becoming thinner overall; although it is thickening in the west, it is thinning in the north. Thomas and others (2004), on the basis of aircraft and satellite laser altimetry surveys, believe the thinning may be accelerating. Joughin and Tulaczyk (2002), on the basis of analysis of ice-flow velocities derived from synthetic aperture radar, concluded that most of the Ross ice streams (ice streams on the east side of the Ross Ice Shelf) have a positive mass balance, whereas Rignot and others (2004) infer even larger negative mass balance for glaciers flowing northward into the Amundsen Sea, a trend suggested by Swithinbank and others (2003a,b; 2004). The mass balance of the East Antarctic ice sheet is thought by Davis and others (2005) to be strongly positive on the basis of the change in satellite altimetry measurements made between 1992 and 2003. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council (1986), in subsequent recommendations by the Scientific Committee on Antarctic Research (SCAR) (1989, 1993), and by the National Science Foundation?s (1990) Division of Polar
9. Strong drifts effects on neoclassical transport
International Nuclear Information System (INIS)
Tessarotto, M.; Gregoratto, D.; White, R.B.
1996-01-01
It is well known that strong drifts play an important role in plasma equilibrium, stability and confinement A significant example concerns, in particular for tokamak plasmas, the case of strong toroidal differential rotation produced by E x B drift which is currently regarded as potentially important for its influence in equilibrium, stability and transport. In fact, theoretically, it has been found that shear flow can substantially affect the stability of microinstabilities as well modify substantially transport. Recent experimental observations of enhanced confinement and transport regimes in Tokamaks, show, however, evidence of the existence of strong drifts in the plasma core. These are produced not only by the radial electric field [which gives rise to the E x B drift], but also by density [N s ], temperature [T s ] and mass flow [V = ωRe var-phi , with e var-phi the toroidal unit vector, R the distance for the symmetry axis of the torus and ω being the toroidal angular rotation velocity] profiles which are suitably steep. This implies that, in a significant part of the plasma core, the relevant scale lengths of the gradients [of N s , T s , ω], i.e., respectively L N , L T and L ω can be as large as the radial scale length characterizing the banana orbits, L b . Interestingly enough, the transport estimates obtained appear close or even lower than the predictions based on the simplest neoclassical model. However, as is well known, the latter applies, in a strict sense only in the case of weak drifts and also ignoring even the contribution of shear flow related to strong E x B drift. Thus a fundamental problem appears the extension of neoclassical transport theory to include the effect of strong drifts in Tokamak confinement systems. The goal of this investigation is to develop a general formulation of neoclassical transport embodying such important feature
10. STS-37 Mission Specialist (MS) Ross during simulation in JSC's FB-SMS
Science.gov (United States)
1991-01-01
STS-37 Mission Specialist (MS) Jerry L. Ross 'borrows' the pilots station to rehearse some of his scheduled duties for his upcoming mission. He is on the flight deck of the fixed-based (FB) shuttle mission simulator (SMS) during this unsuited simulation. The SMS is part of JSC's Mission Simulation and Training Facility Bldg 5.
11. A Q-Methodological Study of the Kubler-Ross Stage Theory.
Science.gov (United States)
Metzger, Anne M.
1979-01-01
Investigated the correspondence between stage changes hypothesized by the Kubler-Ross theory and the perception of the course of illness by seriously ill patients and their spouses. Supported the use of Q-methodology as a research procedure for investigations of terminal illness. (Author)
12. 76 FR 77684 - Establishment of the Fort Ross-Seaview Viticultural Area
Science.gov (United States)
2011-12-14
...; Treasury decision. SUMMARY: This Treasury decision establishes the 27,500-acre Fort Ross-Seaview... may purchase. DATES: Effective Date: January 13, 2012. FOR FURTHER INFORMATION CONTACT: Elisabeth C... may purchase. Establishment of a viticultural area is neither an approval nor an endorsement by TTB of...
13. Two Case Histories, Ishbel Ross and Emma Bugbee: Women Journalists Ride the Rail with the Suffragettes.
Science.gov (United States)
Merrick, Beverly G.
The rise to prominence of the women's suffrage movement in the World War I years brought women reporters into U.S. newsrooms for the first time. In 1911 Emma Bugbee became the first woman hired as a "hard" news reporter for the "New York Tribune" (later the "Herald Tribune"). Ishbel Ross, author of "Ladies of the…
14. Why can rossing uranium mine keep mining even in low price conditions of uranium market
International Nuclear Information System (INIS)
Tan Chenglong
2004-01-01
Rossing uranium mine is the only operating uranium mine in the world where the uranium occurs in intrusive alaskite. In the past 10 years, uranium market regressed in the world, uranium production weakened, expenditures of capital for uranium exploration were insufficient. Uranium spot market price rapidly decreased from $111.8/kg U in late 1970's to$22.1/kg U in mid-1990's. Why can Rossing uranium mine mined with traditional underground and open pit operation can keep running even in low price conditions of uranium market? Augumenting research on the deposit, mineral and technology, decreasing production cost and improving selling strategy can not only maintain Rossing's uranium production at present, but also ensure sustainable development in the coming 15 years. Exploration of low-costed uranium deposits is very important. However, obvious economic benefits can be obtained, as Rossing uranium mine does, by augumenting geological-economical research on the known uranium deposits of hard-rock type and by using new techniques to improve the conventional techniques in the uranium mine development. (authors)
15. Assessing Competition with the Panzar-Rosse Model: The Role of Scale, Costs, and Equilibrium
NARCIS (Netherlands)
Bikker, J.A.|info:eu-repo/dai/nl/06912261X; Shaffer, S.; Spierdijk, L.
2009-01-01
The Panzar-Rosse test has been widely applied to assess competitive conduct, often in specifcations controlling for firm scale or using a price equation. We show that neither a price equation nor a scaled revenue function yields a valid measure for competitive conduct. Moreover, even an unscaled
16. A Helping Hand in the Frederick Community—Ross Smith | Poster
Science.gov (United States)
By day, Ross Smith is the compliance and security officer for Data Management Services, Inc., assigned to the National Cancer Institute (NCI) at Frederick. His role is to ensure the secure operation of in-house computer systems, servers, and network connections. But in his spare time, Smith is also a volunteer firefighter and emergency medical technician (EMT).
17. 76 FR 71082 - Strata Energy, Inc., Ross Uranium Recovery Project; New Source Material License Application...
Science.gov (United States)
2011-11-16
... NUCLEAR REGULATORY COMMISSION [Docket No. 40-9091; NRC-2011-0148] Strata Energy, Inc., Ross Uranium Recovery Project; New Source Material License Application; Notice of Intent To Prepare a... intent to prepare a supplemental environmental impact statement. SUMMARY: Strata Energy, Inc. (Strata...
18. Photographer: Digital Telepresence: Dr Murial Ross's Virtual Reality Application for Neuroscience
Science.gov (United States)
1995-01-01
Photographer: Digital Telepresence: Dr Murial Ross's Virtual Reality Application for Neuroscience Research Biocomputation. To study human disorders of balance and space motion sickness. Shown here is a 3D reconstruction of a nerve ending in inner ear, nature's wiring of balance organs.
19. Märten Ross sõnastas majanduskriisi õppetunnid / Argo Ideon
Index Scriptorium Estoniae
Ideon, Argo, 1966-
2011-01-01
Ajutiselt peaministri majandus- ja rahandusnõunikuna töötanud endine Eesti Panga asepresident Märten Ross kirjutas loetelu õppetundidest, mida Eesti majanduspoliitika peaks arvestama 2008.-2009. aasta kriisi põhjal. Rossi 10 punkti lühidalt. Rahandusminister Jürgen Ligi ning Eesti Panga rahapoliitika ja majandusuuringute osakonna asejuhataja Martin Lindpere arvamus
20. Ross In Situ Uranium Recovery Project NESHAP Subpart W Construction Approval
Science.gov (United States)
On May 5, 2015, EPA issued a Construction Approval under the National Emission Standards for Hazardous Air Pollutants (NESHAPs) at 40 CFR Part 61, subpart W, to Strata Energy, Inc., for their Ross In Situ Recovery (ISR) Uranium Project in Crook County, WY.
1. The place of theology in the modern university | Ross | Journal of ...
African Journals Online (AJOL)
The place of theology in the modern university. Kenneth R. Ross. Abstract. No Abstract. Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's · More about ...
2. Astronauts Ross and Helms at CAPCOM station during STS-61 simulations
Science.gov (United States)
1993-01-01
Astronauts Jerry L. Ross and Susan J. Helms are pictured at the Spacecraft Communicators console during joint integrated simulations for the STS-61 mission. Astronauts assigned to extravehicular activity (EVA) tasks with the Hubble Space Telescope (HST) were simultaneously rehearsing in a neutral buoyancy tank at the Marshall Space Flight Center (MSFC) in Alabama.
3. Transcatheter versus surgical valve replacement for a failed pulmonary homograft in the Ross population.
Science.gov (United States)
Alassas, Khadija; Mohty, Dania; Clavel, Marie Annick; Husain, Aysha; Hijji, Talal; Aljoufan, Mansour; Alhalees, Zohair; Fadel, Bahaa M
2018-04-01
Patients who undergo the Ross procedure are at increased risk of pulmonary valve (PV) homograft dysfunction. For those who require reintervention on the homograft, transcatheter PV replacement (tPVR) provides a less invasive therapeutic option than surgical PVR (sPVR). We examined the outcomes following tPVR versus sPVR in a cohort of patients who underwent the Ross procedure. We performed a retrospective analysis of Ross patients age ≥14 years who underwent tPVR (n = 47) or sPVR (n = 41) at our institution. The patients' clinical and echocardiographic data were reviewed. Baseline parameters, including demographic data and left ventricular and right ventricular (RV) systolic function, were similar in the 2 groups. The mean follow-up was 56 ± 24 months for the tPVR group and 89 ± 46 months for the sPVR group (P Ross patients who require reintervention on the PV homograft, both tPVR and sPVR provide low procedural mortality and comparable midterm outcome with no significant difference in mortality or PV reintervention. However, IE is more common following tPVR. A larger randomized study is needed to determine the role of each procedure in patient management. Copyright © 2017 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.
4. Report of the Dutch experience with the Ross procedure in 343 patients
NARCIS (Netherlands)
Takkenberg, J. J. M.; Dossche, K. M. E.; Hazekamp, M. G.; Nijveld, A.; Jansen, E. W. L.; Waterbolk, T. W.; Bogers, A. J. J. C.
2002-01-01
Limited information is available on outcome after autograft aortic valve replacement, in particular with respect to the durability of the autograft and of the allograft used to reconstruct the right ventricular outflow tract. A retrospective follow-up study of all patients who underwent a Ross
5. TEST OF THE CHEN-ROLL-ROSS MACROECONOMIC FACTOR MODEL: EVIDENCE FROM CROATIAN STOCK MARKET
Directory of Open Access Journals (Sweden)
Denis Dolinar
2015-12-01
Full Text Available This paper empirically examines the well-known Chen-Roll-Ross model on the Croatian stock market. Modifications of definitions of the Chen-Roll-Ross model variables showed as necessary because of doubtful availability and quality of input data needed. Namely, some macroeconomic and market variables are not available in the originally defined form or do not exist. In that sense this paper gives some alternative definitions for some model variables. Also, in order to improve statistical analysis, in this paper we have modified Fama-MacBeth technique in the way that second-pass regression was substituted with panel regression analysis. Based on the two-pass regression analysis of returns of 34 Croatian stocks on 4 macroeconomic variables during the seven-and-half-year observation period the following conclusion is made. In contrast to the results of Chen, Roll and Ross (1986 for the U.S. stock market, their model is not successful when describing a risk-return relation of Croatian stocks. Nevertheless, one observed version of the Chen-RollRoss model showed certain statistical significance. Namely, two risk factors in that version of the model were statistically significant: default premium, measured as risk premium for the corporate short-term bank loan financing, and term structure premium, measured on short-run basis.
6. MR imaging of right ventricular function after the Ross procedure for aortic valve replacement: initial experience
NARCIS (Netherlands)
Grotenhuis, Heynric B.; de Roos, Albert; Ottenkamp, Jaap; Schoof, Paul H.; Vliegen, Hubert W.; Kroft, Lucia J. M.
2008-01-01
PURPOSE: To prospectively assess right ventricular (RV) function after the Ross procedure by using magnetic resonance (MR) imaging. MATERIALS AND METHODS: The local ethics committee approved the study and informed consent was obtained from all participants prior to enrollment in the study. Seventeen
7. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica
Czech Academy of Sciences Publication Activity Database
Elster, Josef; Nedbalová, Linda; Vodrážka, R.; Láska, K.; Haloda, J.; Komárek, Jiří
2016-01-01
Roč. 13, č. 2 (2016), s. 535-549 ISSN 1726-4170 R&D Projects: GA MŠk ME 945 Institutional support: RVO:67985939 Keywords : James Ross Island * cyanobacteria * microalgae Subject RIV: EH - Ecology, Behaviour Impact factor: 3.851, year: 2016
8. 76 FR 22338 - Proposed Fort Ross-Seaview Viticultural Area; Comment Period Reopening
Science.gov (United States)
2011-04-21
... May 9, 2005, from all interested persons. In response to a request from a local wine industry member... the Fort Ross-Seaview viticultural area. Two local wine industry members supported the petition without qualification; a third industry member supported the viticultural area's establishment while...
9. Single nozzle spray drift measurements of drift reducing nozzles at two forward speeds
NARCIS (Netherlands)
Stallinga, H.; Zande, van de J.C.; Michielsen, J.G.P.; Velde, van P.
2016-01-01
In 2011‒2012 single nozzle field experiments were carried out to determine the effect of different flat fan spray nozzles of the spray drift reduction classes 50, 75, 90 and 95% on spray drift at two different forward speeds (7.2 km h-1 and 14.4 km h-1). Experiments were performed with a single
10. Optical drift effects in general relativity
Science.gov (United States)
Korzyński, Mikołaj; Kopiński, Jarosław
2018-03-01
We consider the question of determining the optical drift effects in general relativity, i.e. the rate of change of the apparent position, redshift, Jacobi matrix, angular distance and luminosity distance of a distant object as registered by an observer in an arbitrary spacetime. We present a fully relativistic and covariant approach, in which the problem is reduced to a hierarchy of ODE's solved along the line of sight. The 4-velocities and 4-accelerations of the observer and the emitter and the geometry of the spacetime along the line of sight constitute the input data. We build on the standard relativistic geometric optics formalism and extend it to include the time derivatives of the observables. In the process we obtain two general, non-perturbative relations: the first one between the gravitational lensing, represented by the Jacobi matrix, and the apparent position drift, also called the cosmic parallax, and the second one between the apparent position drift and the redshift drift. The applications of the results include the theoretical study of the drift effects of cosmological origin (so-called real-time cosmology) in numerical or exact Universe models.
11. Drift chamber performance in the field of a superconducting magnet: measurement of the drift angle
International Nuclear Information System (INIS)
Sanders, G.H.; Sherman, S.; McDonald, K.T.; Smith, A.J.S.; Thaler, J.J.
1977-01-01
Results are presented of the first measurements in a study of drift chamber performance in magnetic fields up to 6 tesla. The angle of the electron drift was measured as a function of electric and magnetic field intensity. It appears that even at the high fields of superconducting magnets (3 to 6 tesla) the drift angle induced by the Lorentz force can be corrected for with tilted electric drift fields and/or the use of Xenon gas. At 3 tesla a drift field tilted at 45 0 with a magnitude of 3.5 kV/cm should restore normal operating conditions. At 4 tesla, a 45 0 tilt field would have a magnitude 5 kV/cm
12. Long-term Evaluation of the Ross Procedure in Acute Infective Endocarditis.
Science.gov (United States)
Ratschiller, Thomas; Sames-Dolzer, Eva; Paulus, Patrick; Schimetta, Wolfgang; Müller, Hannes; Zierer, Andreas F; Mair, Rudolf
2017-10-05
Optimal valve substitute for young patients with aortic valve endocarditis remains controversial. Given its better resistance to infection, the Ross procedure is an attractive alternative to prosthetic valve replacement or homograft implantation. The objective of this study was to assess long-term outcomes of the Ross procedure in this indication. From January 1991 to April 2017, 190 patients underwent a Ross procedure at our institution. Acute endocarditis was the indication for operation in 19 patients, including 6 patients with a bicuspid aortic valve. The pulmonary autograft was implanted as freestanding root replacement in all patients. The clinical follow-up is 100% complete, with a mean of 12.0 ± 5.7 years. The mean age of the study population was 35.9 ± 11.5 years. Moderate or severe aortic regurgitation was present in 84.2% of the patients. Systemic embolization had occurred in 36.8% of the patients. The mean aortic cross-clamp time was 126 ± 24 minutes. The median length of stay on the intensive care unit was 1 day. Mortality at 30 days was 5.3% (1 patient with gastrointestinal bleeding). Echocardiography at hospital discharge documented no or trivial aortic regurgitation in all patients. No case of recurrent endocarditis affecting the autograft occurred. One patient (0.4% per patient-year) was reoperated 1.8 years after the Ross procedure for homograft endocarditis. Three patients (15.8%) were reoperated for autograft aneurysm. The Ross procedure is a safe and effective alternative to prosthetic valve replacement or homograft implantation in selected young patients with acute endocarditis with a low rate of recurrent infection. Copyright © 2017 Elsevier Inc. All rights reserved.
13. Valve-sparing root replacement for freestanding pulmonary autograft aneurysm after the Ross procedure.
Science.gov (United States)
Ratschiller, Thomas; Eva, Sames-Dolzer; Schimetta, Wolfgang; Paulus, Patrick; Müller, Hannes; Zierer, Andreas; Mair, Rudolf
2018-02-20
Autograft dilatation is the main long-term complication following the Ross procedure using the freestanding root replacement technique. We reviewed our 25-year experience with the Ross procedure with a special emphasis on valve-sparing reoperations. From 1991 to 2016, 153 patients (29.6 ± 16.6 years; 29.4% pediatric) underwent a Ross operation at our institution with implantation of the autograft as freestanding root replacement. The follow-up is 98.7% complete with a mean of 12.2 ± 5.5 years. Mortality at 30-days was 2.0%. Echocardiography documented no or trivial aortic regurgitation in 99.3% of the patients at discharge. Survival probability at 20 years was 85.4%. No case of autograft endocarditis occurred. Autograft deterioration rate was 2.01% per patient-year, and freedom from autograft reoperation was 75.3% at 15 years. A reoperation for autograft aneurysm was required in 35 patients (22.9%) at a mean interval of 11.1 ± 4.6 years after the Ross procedure. A valve-sparing root replacement was performed in 77% of patients, including 10 David and 17 Yacoub procedures with no early mortality. Three patients required prosthetic valve replacement within 2 years after a Yacoub operation. At latest follow-up, 92% of all surviving patients still carry the pulmonary autograft valve. Freedom from autograft valve replacement was 92.1% at 15 years. Using the David or Yacoub techniques, the autograft valve can be preserved in the majority of patients with root aneurysms after the Ross procedure. Reoperations can be performed with no early mortality, a good functional midterm result, and an acceptable reintervention rate. Copyright © 2018 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.
14. Spray particle drift mitigation using field corn (Zea mays L.) as a drift barrier.
Science.gov (United States)
Vieira, Bruno C; Butts, Thomas R; Rodrigues, Andre O; Golus, Jeffrey A; Schroeder, Kasey; Kruger, Greg R
2018-04-24
15. The Ross Operation in Children and Young Adults: 12-Year Results and Trends From the UK National Database.
Science.gov (United States)
Zebele, Carlo; Chivasso, Pierpaolo; Sedmakov, Christo; Angelini, Gianni; Caputo, Massimo; Parry, Andrew; Stoica, Serban
2014-07-01
To determine UK national trends and results of the Ross operation in relation to all aortic valve interventions. Examination of the UK Congenital Central Cardiac Audit Database for all aortic valve procedures performed between 2000 and 2011 in children (0-16 years) and young adults (16-30 years). A total of 2,206 aortic valve procedures were performed in children and 1,824 in young adults, the proportions in the two groups being: Ross operation (19% vs 15%, respectively), surgical valvoplasty (9.5% vs 4%), surgical valvotomy (9.5% vs 1%), aortic valve replacement (AVR; 11% vs 55%), aortic root replacement (4% vs 18%), and balloon valvoplasty (47% vs 7%). The 30-day and 1-year survival after Ross is 99.3% and 98.7%, respectively, in the last four years achieving 100%. In children, the proportion of balloon valvoplasty increased from an average of 43% in 2000 to 2006 to 53% in 2007 to 2011, whereas the Ross operation decreased from 22% to 16% (P Ross (P Ross operations performed. The year-on-year changes show a significant decreasing trend locally and nationally. Despite an excellent track record, the Ross operation is performed less frequently in the United Kingdom. This report is a first step in comparing treatment modalities at national level. © The Author(s) 2014.
16. The Ross procedure offers excellent survival compared with mechanical aortic valve replacement in a real-world setting.
Science.gov (United States)
Andreas, Martin; Wiedemann, Dominik; Seebacher, Gernot; Rath, Claus; Aref, Tandis; Rosenhek, Raphael; Heinze, Georg; Eigenbauer, Ernst; Simon, Paul; Ruetzler, Kurt; Hiesmayr, Joerg-Michael; Moritz, Anton; Laufer, Guenther; Kocher, Alfred
2014-09-01
The ideal prosthesis for young patients requiring aortic valve replacement has not been defined to date. Although the Ross procedure provides excellent survival, its application is still limited. We compared the long-term survival after the Ross procedure with mechanical aortic valve replacement. All consecutive Ross procedures and mechanical aortic valve replacements performed between 1991 and 2008 at a single centre were analysed. Only adult patients between 18 and 50 years of age were included in the study. Survival and valve-related complications were evaluated. Furthermore, survival was compared with the age- and sex-matched Austrian population. A total of 159 Ross patients and 173 mechanical valve patients were included. The cumulative survival for the Ross procedure was significantly better, with survival rates of 96, 94 and 93% at 5, 10 and 15 years, respectively, in comparison to 90, 84 and 75% (P Ross group but was significantly reduced in the mechanical valve group. In a real-world setting, the Ross procedure is associated with a long-term survival benefit in young adults in comparison to mechanical aortic valve replacement. © The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
17. P-type silicon drift detectors
International Nuclear Information System (INIS)
Walton, J.T.; Krieger, B.; Krofcheck, D.; O'Donnell, R.; Odyniec, G.; Partlan, M.D.; Wang, N.W.
1995-06-01
Preliminary results on 16 CM 2 , position-sensitive silicon drift detectors, fabricated for the first time on p-type silicon substrates, are presented. The detectors were designed, fabricated, and tested recently at LBL and show interesting properties which make them attractive for use in future physics experiments. A pulse count rate of approximately 8 x l0 6 s -1 is demonstrated by the p-type silicon drift detectors. This count rate estimate is derived by measuring simultaneous tracks produced by a laser and photolithographic mask collimator that generates double tracks separated by 50 μm to 1200 μm. A new method of using ion-implanted polysilicon to produce precise valued bias resistors on the silicon drift detectors is also discussed
18. Correcting sample drift using Fourier harmonics.
Science.gov (United States)
Bárcena-González, G; Guerrero-Lebrero, M P; Guerrero, E; Reyes, D F; Braza, V; Yañez, A; Nuñez-Moraleda, B; González, D; Galindo, P L
2018-07-01
During image acquisition of crystalline materials by high-resolution scanning transmission electron microscopy, the sample drift could lead to distortions and shears that hinder their quantitative analysis and characterization. In order to measure and correct this effect, several authors have proposed different methodologies making use of series of images. In this work, we introduce a methodology to determine the drift angle via Fourier analysis by using a single image based on the measurements between the angles of the second Fourier harmonics in different quadrants. Two different approaches, that are independent of the angle of acquisition of the image, are evaluated. In addition, our results demonstrate that the determination of the drift angle is more accurate by using the measurements of non-consecutive quadrants when the angle of acquisition is an odd multiple of 45°. Copyright © 2018 Elsevier Ltd. All rights reserved.
19. Mean Lagrangian drift in continental shelf waves
Science.gov (United States)
Drivdal, M.; Weber, J. E. H.
2012-04-01
The time- and depth-averaged mean drift induced by barotropic continental shelf waves (CSW's) is studied theoretically for idealized shelf topography by calculating the mean volume fluxes to second order in wave amplitude. The waves suffer weak spatial damping due to bottom friction, which leads to radiation stress forcing of the mean fluxes. In terms of the total wave energy density E¯ over the shelf region, the radiation stress tensor component S¯11 for CSW's is found to be different from that of shallow water surface waves in a non-rotating ocean. For CSW's, the ratio ¯S11/¯E depends strongly on the wave number. The mean Lagrangian flow forced by the radiation stress can be subdivided into a Stokes drift and a mean Eulerian drift current. The magnitude of the latter depends on the ratio between the radiation stress and the bottom stress acting on the mean flow. When the effect of bottom friction acts equally strong on the waves and the mean current, calculations for short CSW's show that the Stokes drift and the friction-dependent wave-induced mean Eulerian current varies approximately in anti-phase over the shelf, and that the latter is numerically the largest. For long CSW's they are approximately in phase. In both cases the mean Lagrangian current, which is responsible for the net particle drift, has its largest numerical value at the coast on the shallow part of the shelf. Enhancing the effect of bottom friction on the Eulerian mean flow, results in a general current speed reduction, as well as a change in spatial structure for long waves. Applying realistic physical parameters for the continental shelf west of Norway, calculations yield along-shelf mean drift velocities for short CSW's that may be important for the transport of biological material, neutral tracers, and underwater plumes of dissolved oil from deep water drilling accidents.
20. Experiencia a largo plazo con la operación de Ross en pacientes pediátricos
Directory of Open Access Journals (Sweden)
José M. Caffarena Calvar
2008-07-01
Conclusions: The Ross and Ross-Konno operations have changed the prognosis of pediatric patients with complex disease of the valve and aortic root. There is growth of the neo-aortic root in young patients. Sinotubular dilatation of the autograft with neoaortic valve insufficiency has been detected in patients with previously dilated aortic root when root replacement technique was performed. The best results are obtained in the younger andlower weight patients with complex left ventricular outflow obstruction without root dilatation. A close follow-up of patients with aortic root dilatation is mandatory to definitely validate the Ross procedure over aortic prosthesis.
1. Accurate computer simulation of a drift chamber
International Nuclear Information System (INIS)
Killian, T.J.
1980-01-01
A general purpose program for drift chamber studies is described. First the capacitance matrix is calculated using a Green's function technique. The matrix is used in a linear-least-squares fit to choose optimal operating voltages. Next the electric field is computed, and given knowledge of gas parameters and magnetic field environment, a family of electron trajectories is determined. These are finally used to make drift distance vs time curves which may be used directly by a track reconstruction program. Results are compared with data obtained from the cylindrical chamber in the Axial Field Magnet experiment at the CERN ISR
2. Drift estimation from a simple field theory
International Nuclear Information System (INIS)
Mendes, F. M.; Figueiredo, A.
2008-01-01
Given the outcome of a Wiener process, what can be said about the drift and diffusion coefficients? If the process is stationary, these coefficients are related to the mean and variance of the position displacements distribution. However, if either drift or diffusion are time-dependent, very little can be said unless some assumption about that dependency is made. In Bayesian statistics, this should be translated into some specific prior probability. We use Bayes rule to estimate these coefficients from a single trajectory. This defines a simple, and analytically tractable, field theory.
3. Ultra-low mass drift chambers
International Nuclear Information System (INIS)
Assiro, R.; Cappelli, L.; Cascella, M.; De Lorenzis, L.; Grancagnolo, F.; Ignatov, F.; L'Erario, A.; Maffezzoli, A.; Miccoli, A.; Onorato, G.; Perillo, M.; Piacentino, G.; Rella, S.; Rossetti, F.; Spedicato, M.; Tassielli, G.
2013-01-01
We present a novel low mass drift chamber concept, developed in order to fulfill the stringent requirements imposed by the experiments for extremely rare processes, which require high resolutions (order of 100–200 keV/c) for particle momenta in a range (50–100 MeV/c) totally dominated by the multiple scattering contribution. We describe a geometry optimization procedure and a new wiring strategy with a feed-through-less wire anchoring system developed and tested on a drift chamber prototype under completion at INFN-Lecce
4. Ultra-low mass drift chambers
Science.gov (United States)
Assiro, R.; Cappelli, L.; Cascella, M.; De Lorenzis, L.; Grancagnolo, F.; Ignatov, F.; L'Erario, A.; Maffezzoli, A.; Miccoli, A.; Onorato, G.; Perillo, M.; Piacentino, G.; Rella, S.; Rossetti, F.; Spedicato, M.; Tassielli, G.; Zavarise, G.
2013-08-01
We present a novel low mass drift chamber concept, developed in order to fulfill the stringent requirements imposed by the experiments for extremely rare processes, which require high resolutions (order of 100-200 keV/c) for particle momenta in a range (50-100 MeV/c) totally dominated by the multiple scattering contribution. We describe a geometry optimization procedure and a new wiring strategy with a feed-through-less wire anchoring system developed and tested on a drift chamber prototype under completion at INFN-Lecce .
5. Properties of low-pressure drift chambers
International Nuclear Information System (INIS)
Breskin, A.; Trautner, N.
1976-01-01
Drift chambers operated with methylal vapour or ethylene at pressures in the range of 10-110 torr are described. A systematic study of position resolution, pulse height and rise time shows that especially for ethylene they are strongly influenced by electron diffusion. Intrinsic position resolution was found to be at least as good as found at atmospheric pressure. A relative pulse height resolution of 10% was obtained with 5.5 MeV alpha-particles. A simple mathematical model which can describe the processes in the drift chamber is presented. (Auth.)
6. Silicon Drift Detectors development for position sensing
International Nuclear Information System (INIS)
Castoldi, A.; Guazzoni, C.; Hartmann, R.; Strueder, L.
2007-01-01
Novel Silicon Drift Detectors (SDDs) with multi-linear architecture specifically intended for 2D position sensing and imaging applications are presented and their achievable spatial, energy and time resolution are discussed. The capability of providing a fast timing of the interaction with nanosecond time resolution is a new available feature that allows operating the drift detector in continuous readout mode for coincidence imaging applications either with an external trigger or in self-timing. The application of SDDs with multi-linear architecture to Compton electrons' tracking within a single silicon layer and the achieved experimental results will be discussed
7. Nonlinear dynamics of resistive electrostatic drift waves
DEFF Research Database (Denmark)
Korsholm, Søren Bang; Michelsen, Poul; Pécseli, H.L.
1999-01-01
The evolution of weakly nonlinear electrostatic drift waves in an externally imposed strong homogeneous magnetic field is investigated numerically in three spatial dimensions. The analysis is based on a set of coupled, nonlinear equations, which are solved for an initial condition which is pertur......The evolution of weakly nonlinear electrostatic drift waves in an externally imposed strong homogeneous magnetic field is investigated numerically in three spatial dimensions. The analysis is based on a set of coupled, nonlinear equations, which are solved for an initial condition which...... polarity, i.e. a pair of electrostatic convective cells....
8. Accurate computer simulation of a drift chamber
CERN Document Server
Killian, T J
1980-01-01
The author describes a general purpose program for drift chamber studies. First the capacitance matrix is calculated using a Green's function technique. The matrix is used in a linear-least-squares fit to choose optimal operating voltages. Next the electric field is computed, and given knowledge of gas parameters and magnetic field environment, a family of electron trajectories is determined. These are finally used to make drift distance vs time curves which may be used directly by a track reconstruction program. The results are compared with data obtained from the cylindrical chamber in the Axial Field Magnet experiment at the CERN ISR. (1 refs).
9. Small-scale lacustrine drifts in Lake Champlain, Vermont
Science.gov (United States)
Manley, Patricia L.; Manley, T.O.; Hayo, Kathryn; Cronin, Thomas
2012-01-01
High resolution CHIRP (Compressed High Intensity Radar Pulse) seismic profiles reveal the presence of two lacustrine sediment drifts located in Lake Champlain's Juniper Deep. Both drifts are positive features composed of highly laminated sediments. Drift B sits on a basement high while Drift A is built on a trough-filling acoustically-transparent sediment unit inferred to be a mass-transport event. These drifts are oriented approximately north–south and are parallel to a steep ridge along the eastern shore of the basin. Drift A, located at the bottom of a structural trough, is classified as a confined, elongate drift that transitions northward to become a system of upslope asymmetric mudwaves. Drift B is perched atop a structural high to the west of Drift A and is classified as a detached elongate drift. Bottom current depositional control was investigated using Acoustic Doppler Current Profilers (ADCPs) located across Drift A. Sediment cores were taken at the crest and at the edges of the Drift A and were dated. Drift source, deposition, and evolution show that these drifts are formed by a water column shear with the highest deposition occurring along its crest and western flank and began developing circa 8700–8800 year BP.
10. A new variable transformation technique for the nonlinear drift vortex
International Nuclear Information System (INIS)
Orito, Kohtaro
1996-02-01
The dipole vortex solution of the Hasegawa-Mima equation describing the nonlinear drift wave is a stable solitary wave which is called the modon. The profile of the modon depends on the nonlinearity of the ExB drift. In order to investigate the nonlinear drift wave more accurately, the effect of the polarization drift needs to be considered. In case of containing the effect of the polarization drift the profile of the electrostatic potential is distorted in the direction perpendicular to the ExB drift. (author)
11. CLOUDS IN THE COLDEST BROWN DWARFS: FIRE SPECTROSCOPY OF ROSS 458C
International Nuclear Information System (INIS)
Burgasser, Adam J.; Simcoe, Robert A.; Bochanski, John J.; Saumon, Didier; Mamajek, Eric E.; McMurtry, Craig; Pipher, Judith L.; Forrest, William J.; Cushing, Michael C.; Marley, Mark S.
2010-01-01
Condensate clouds are a salient feature of L dwarf atmospheres, but have been assumed to play little role in shaping the spectra of the coldest T-type brown dwarfs. Here we report evidence of condensate opacity in the near-infrared spectrum of the brown dwarf candidate Ross 458C, obtained with the Folded-Port Infrared Echellette (FIRE) spectrograph at the Magellan Telescopes. These data verify the low-temperature nature of this source, indicating a T8 spectral classification, log 10 L bol /L sun = -5.62 ± 0.03, T eff = 650 ± 25 K, and a mass at or below the deuterium burning limit. The data also reveal enhanced emission at the K band associated with youth (low surface gravity) and supersolar metallicity, reflecting the properties of the Ross 458 system (age = 150-800 Myr, [Fe/H] = +0.2 to +0.3). We present fits of FIRE data for Ross 458C, the T9 dwarf ULAS J133553.45+113005.2, and the blue T7.5 dwarf SDSS J141624.08+134826.7B, to cloudless and cloudy spectral models from Saumon and Marley. For Ross 458C, we confirm a low surface gravity and supersolar metallicity, while the temperature differs depending on the presence (635 +25 -35 K) or absence (760 +70 -45 K) of cloud extinction. ULAS J1335+1130 and SDSS J1416+1348B have similar temperatures (595 +25 -45 K), but distinct surface gravities (log g = 4.0-4.5 cgs versus 5.0-5.5 cgs) and metallicities ([M/H] ∼ +0.2 versus -0.2). In all three cases, cloudy models provide better fits to the spectral data, significantly so for Ross 458C. These results indicate that clouds are an important opacity source in the spectra of young cold T dwarfs and should be considered when characterizing planetary-mass objects in young clusters and directly imaged exoplanets. The characteristics of Ross 458C suggest that it could itself be regarded as a planet, albeit one whose cosmogony does not conform with current planet formation theories.
12. Psychometric Consequences of Subpopulation Item Parameter Drift
Science.gov (United States)
Huggins-Manley, Anne Corinne
2017-01-01
This study defines subpopulation item parameter drift (SIPD) as a change in item parameters over time that is dependent on subpopulations of examinees, and hypothesizes that the presence of SIPD in anchor items is associated with bias and/or lack of invariance in three psychometric outcomes. Results show that SIPD in anchor items is associated…
13. Resistive drift wave turbulence and transport
International Nuclear Information System (INIS)
Wakatani, M.
1986-01-01
Our efforts for studying the properties of resistive drift wave turbulence by using model mode-coupling equations are shown. It may be related to the edge turbulence and the associated anomalous transport in tokamaks or in stellarator/heliotron. (author)
14. Effects of Drifting Macroalgae in Eelgrass Ecosystems
DEFF Research Database (Denmark)
Canal Vergés, Paula; Valdemarsen, Thomas Bruun; Kristensen, Erik
2010-01-01
and physical damage on eelgrass can occur when macroalgae are drifting as bedload. The ballistic effect of moving macroalgae on surface sediment was tested in the field as well as in a series of annular flume experiments, where simultaneous measurements of macroalgae transport and turbidity were measured...
15. EU law revisions and legislative drift
DEFF Research Database (Denmark)
Borghetto, Enrico; Mäder, Lars Kai
2014-01-01
in force in their original form for several years while others are revised soon after their enactment. What factors account for this variation? We empirically analyze the proposition that in the presence of ‘legislative drift,’ i.e. the intertemporal variation of decision-makers’ preferences, major...
16. Nonlinear radial propagation of drift wave turbulence
International Nuclear Information System (INIS)
Prakash, M.
1985-01-01
We study the linear and the nonlinear radial propagation of drift wave energy in an inhomogeneous plasma. The drift mode excited in such a plasma is dispersive in nature. The drift wave energy spreads out symmetrically along the direction of inhomogeneity with a finite group velocity. To study the effect of the nonlinear coupling on the propagation of energy in a collision free plasma, we solve the Hasegawa-Mima equation as a mixed initial boundary-value problem. The solutions of the linearized equation are used to check the reliability of our numerical calculations. Additional checks are also performed on the invariants of the system. Our results reveal that a pulse gets distorted as it propagates through the medium. The peak of the pulse propagates with a finite velocity that depends on the amplitude of the initial pulse. The polarity of propagation depends on the initial parameters of the pulse. We have also studied drift wave propagation in a resistive plasma. The Hasegawa-Wakatani equations are used to investigate this problem
17. Study and analysis of drift chamber parameters
International Nuclear Information System (INIS)
Martinez Laso, L.
1988-01-01
The present work deals mainly with drift chambers. In the first chapter a summary of drift chamber properties is presented. The information has been collected from the extensive bibliography available in this field. A very simple calculation procedure of drift chamber parameters has been developed and is presented in detail in the second chapter. Some prototypes have been made following two geometries (multidrift chamber and Z-chambers). Several installations have been used for test and calibration of these prototypes. A complete description of these installations is given in the third chapter. Cosmic rays, beta particles from a Ru106 radiactive source and a test beam in the WA (West Area) of SPS at CERN have been used for experimental purposes. The analysis and the results are described for the different setups. The experimental measurements have been used to produce a complete cell parametrization (position as function of drift time) and to obtain spatial resolution values (in the range of 200-250 um). Experimental results are in good agreement with numerical calculations. (Author)
18. Drift wave in pair-ion plasma
ion plasma are discussed. It is shown that the temperature and/or mass difference of both species could produce drift wave in a pair-ion plasma. The results are discussed in the context of the fullerene pair-ion plasma experiment.
19. Learning in the context of distribution drift
Science.gov (United States)
2017-05-09
Figure 3 shows a heatmap of the pairwise drift in the joint distribution on the Landsat-8 French land usage satellite data. This data represents 10 meter...listed under the List of Publications. 1. White, C., Using Big Data for Smarter Decision Making. 2011, BI Research: Ashland, Or. 2. Cook , S., et al
20. Comment on the drift mirror instability
Czech Academy of Sciences Publication Activity Database
Hellinger, Petr
2008-01-01
Roč. 15, č. 5 (2008), 054502/1-054502/2 ISSN 1070-664X R&D Projects: GA AV ČR IAA300420702 Institutional research plan: CEZ:AV0Z30420517 Keywords : drift mirror instability * linear theory Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.427, year: 2008
1. Sealed drift tube cosmic ray veto counters
International Nuclear Information System (INIS)
Rios, R.; Tatar, E.; Bacon, J.D.; Bowles, T.J.; Hill, R.; Green, J.A.; Hogan, G.E.; Ito, T.M.; Makela, M.; Morris, C.L.; Mortenson, R.; Pasukanics, F.E.; Ramsey, J.; Saunders, A.; Seestrom, S.J.; Sondheim, W.E.; Teasdale, W.; Saltus, M.; Back, H.O.; Cottrell, C.R.
2011-01-01
We describe a simple drift tube counter that has been used as a cosmic ray veto for the UCNA experiment, a first-ever measurement of the neutron beta-asymmetry using ultra-cold neutrons. These detectors provide an inexpensive alternative to more conventional scintillation detectors for large area cosmic ray anticoincidence detectors.
2. Learning drifting concepts with neural networks
NARCIS (Netherlands)
Biehl, Michael; Schwarze, Holm
1993-01-01
The learning of time-dependent concepts with a neural network is studied analytically and numerically. The linearly separable target rule is represented by an N-vector, whose time dependence is modelled by a random or deterministic drift process. A single-layer network is trained online using
3. Fine structure in fast drift storm bursts
International Nuclear Information System (INIS)
McConnell, D.; Ellis, G.R.A.
1981-01-01
Recent observations with high time resolution of fast drift storm (FDS) solar bursts are described. A new variety of FDS bursts characterised by intensity maxima regularly placed in the frequency domain is reported. Possible interpretations of this are mentioned and the implications of the short duration of FDS bursts are discussed. (orig.)
4. Astrometric studies of the regions BD + 17 degree 4946, BD -5 degree 3071, and Ross 730-1
International Nuclear Information System (INIS)
Russell, J.; Gatewood, G.
1975-01-01
Positions, proper motions, and absolute parallaxes were found for 46 stars in the regions of BD +17 degree4946, BD -5 degree3071, and Ross 730-1. BD +17 degree4946 showed some evidence of irregular variations in position and magnitude. The residuals for Ross 730-1 were used in a preliminary study to test for an appropriate weighting system; a weak weighting system was indicated. (auth)
5. Climate-driven ichthyoplankton drift model predicts growth of top predator young.
Science.gov (United States)
Myksvoll, Mari S; Erikstad, Kjell E; Barrett, Robert T; Sandvik, Hanno; Vikebø, Frode
2013-01-01
Climate variability influences seabird population dynamics in several ways including access to prey near colonies during the critical chick-rearing period. This study addresses breeding success in a Barents Sea colony of common guillemots Uria aalge where trophic conditions vary according to changes in the northward transport of warm Atlantic Water. A drift model was used to simulate interannual variations in transport of cod Gadus morhua larvae along the Norwegian coast towards their nursery grounds in the Barents Sea. The results showed that the arrival of cod larvae from southern spawning grounds had a major effect on the size of common guillemot chicks at fledging. Furthermore, the fraction of larvae from the south was positively correlated to the inflow of Atlantic Water into the Barents Sea thus clearly demonstrating the mechanisms by which climate-driven bottom-up processes influence interannual variations in reproductive success in a marine top predator.
6. Climate-driven ichthyoplankton drift model predicts growth of top predator young.
Directory of Open Access Journals (Sweden)
Mari S Myksvoll
Full Text Available Climate variability influences seabird population dynamics in several ways including access to prey near colonies during the critical chick-rearing period. This study addresses breeding success in a Barents Sea colony of common guillemots Uria aalge where trophic conditions vary according to changes in the northward transport of warm Atlantic Water. A drift model was used to simulate interannual variations in transport of cod Gadus morhua larvae along the Norwegian coast towards their nursery grounds in the Barents Sea. The results showed that the arrival of cod larvae from southern spawning grounds had a major effect on the size of common guillemot chicks at fledging. Furthermore, the fraction of larvae from the south was positively correlated to the inflow of Atlantic Water into the Barents Sea thus clearly demonstrating the mechanisms by which climate-driven bottom-up processes influence interannual variations in reproductive success in a marine top predator.
7. Competition and Concentration in Bangladeshi Banking Sector: An Application of Panzar-Rosse Model
Directory of Open Access Journals (Sweden)
Md. Anwar Hossain Repon
2016-01-01
Full Text Available The purpose of this paper is to investigate the market structure and degree of concentration of Bangladeshi banking industry. The study measured market concentration by using widely recognized measures like k-bank concentration ratio and Herfindahl-Hirchman Index (HHI. It evaluates market structure by applying Panzar-Rosse Model over 8 years period from 2006 to 2013. The result of concentration measures indicates a decreasing trend and low level of market concentration in Bangladeshi banking industry over the sample period. The panzer-Rosse “H-Statistic” suggests that banks in Bangladesh are operating under monopolistic competition. Present paper contributes to a burgeoning literature on banking competition that has evolved significantly over the past periods on a developing country perspective like Bangladesh.
8. A Battle of Words: "Dignity" and "Peace" in the Writings of Elisabeth Kübler-Ross.
Science.gov (United States)
Burnier, Daniel
2017-04-01
This article analyzes the writings of Elisabeth Kübler-Ross through the discursive lens of the phrase "dying with dignity." For her, the phrase meant allowing someone to die comfortably his/her own death. This phrase has to be understood in relationship with the final "stage of acceptance" of her model. Describing this key part of her well-known scientific output, she often used, in the early 1970s, the phrase "dying in peace and dignity." An evaluation of the evidence suggests that because the concept of dignity was co-opted by the pro-euthanasia movement during this decade, the language of dignity was little by little abandoned by her. In later years, only "peace" survived from her favorite expression. Although this concept of peace remains present to the end in all Kübler-Ross writings, the pro-euthanasia movement has also started to speak the language of peace.
9. Ross Terrill, The New Chinese Empire — and what it means for the United States
OpenAIRE
Eyraud, Henri
2007-01-01
Ross Terrill part du constat que la Chine est restée, jusqu'à maintenant, un empire sans contre-pouvoirs et répressif. Mao Zedong, Deng Xiaoping, Jiang Zemin et aujourd'hui Hu Jintao, chacun à leur manière et à leur époque, ont adapté, voire modernisé, les formes de pouvoir de l'empire millénaire. Pour l'auteur, la République populaire de Chine (RPC) a conservé une conception impériale d'elle-même et a réinventé l'autocratie millénaire. Ross Terrill est un observateur politique, mais aussi u...
10. STS-74 Mission Specialists McArther and Ross in OPF
Science.gov (United States)
1995-01-01
In Orbiter Processing Facility Bay 2, STS-74 Mission Specialist William 'Bill' McArthur Jr. (left) and Jerry L. Ross are reviewing the configuration of payload elements in the orbiter Atlantis' payload bay. Ross and McArthur are participating in the Crew Equipment Interface Test (CEIT), an opportunity for flight crew members to become familiar with the payload hardware they will be working with on-orbit. Located in Atlantis' payload bay are the Orbiter Docking System and the Docking Module, two pieces of flight hardware that will play a crucial role in the second docking of the Space Shuttle to the Russian Space Station Mir. STS-74 is currently targeted for an early November launch
11. Percutaneous valved stent repair of a failed homograft: implications for the Ross procedure.
Science.gov (United States)
Pretorius, Victor; Jones, Alan; Taylor, Dylan; Coe, Yashu; Ross, David B
2008-08-01
A case of percutaneous pulmonary valve implantation following a failed homograft in the pulmonary position is reported. A 16-year-old boy developed infective endocarditis of his pulmonary homograft, which was implanted four years earlier during a Ross procedure for congenital aortic stenosis. Following successful medical therapy, the boy was symptomatic due to pulmonary stenosis and regurgitation. A 22 mm Melody valve (Medtronic, USA) was successfully implanted percutaneously. His symptoms resolved and he was discharged home one day after the procedure. Echocardiography at the six-month follow-up demonstrated a normally functioning pulmonary valve. Percutaneous pulmonary valve replacement may make the Ross procedure a more attractive option for patients with aortic stenosis, particularly in the pediatric population.
12. Drift mechanism for energetic charged particles at shocks
International Nuclear Information System (INIS)
Webb, G.M.; Axford, W.I.; Terasawa, T.
1983-01-01
The energy changes of energetic charged particles at a plane shock due to the so-called drift mechanism are analyzed by using the ''adiabatic treatment.'' The analysis shows that for a fast MHD shock, particles lose energy owing to acceleration (curvature) drift in the magnetic field at the shock with the drift velocity being antiparallel to the electric field, and they gain energy owing to gradient drift parallel to the electric field. It is shown that particles with pitch angles aligned along the magnetic field which pass through the shock tend to lose energy owing to acceleration drift, whereas particles with pitch angles nonaligned to the magnetic field gain energy owing to gradient drift. Particles that are reflected by the shock always gain energy. Slow-mode shocks may be similarly analyzed, but in this case curvature drifts give rise to particle energy gains, and gradient drifts result in particle energy losses
13. Barber's Point, Oahu, Hawaii Drift Card Study 2002-2004
Data.gov (United States)
National Oceanic and Atmospheric Administration, Department of Commerce — Drift cards were be released from Barber's Point, Oahu, approximately once a month during the two year span to get an idea of the distribution of card drift under...
14. Electromagnetic drift modes in an inhomogeneous electron gas
DEFF Research Database (Denmark)
Shukla, P. K.; Pecseli, H. L.; Juul Rasmussen, Jens
1986-01-01
A pair of nonlinear equations is derived which describes the dynamics of the electromagnetic drift oscillations in a nonuniform magnetized electron gas. It is shown that the nonlinear electromagnetic drift modes can propagate in the form of dipole vortices...
15. A drift chamber constructed of aluminized mylar tubes
International Nuclear Information System (INIS)
Baringer, P.; Jung, C.; Ogren, H.O.; Rust, D.R.
1987-01-01
A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls. (orig.)
16. A drift chamber constructed of aluminized mylar tubes
Science.gov (United States)
Baringer, P.; Jung, C.; Ogren, H. O.; Rust, D. R.
1987-03-01
A thin reliable drift chamber has been constructed to be used near the interaction point of the PEP storage ring in the HRS detector. It is composed of individual drift tubes with aluminized mylar walls.
17. Ansel Adams's Eucalyptus Tree, Fort Ross: Nature, Photography, and the Search for California
OpenAIRE
2005-01-01
This article considers the image of California evoked in the unusual Ansel Adams photograph Eucalyptus Tree, Fort Ross, California (1969), a Polaroid Land image of the garrison fence and an aged eucalyptus tree. Considering the participation of Russian occupation, Australian cross-pollination, Carleton Watkins's early photographs of redwoods, automotive and tourist images in the creation of this distinctive California place, the article argues that to understand Ansel Adams's work, we must no...
18. Impact of pregnancy on autograft dilatation and aortic valve function following the Ross procedure.
Science.gov (United States)
Carvajal, Horacio G; Lindley, Kathryn J; Shah, Trupti; Brar, Anoop K; Barger, Philip M; Billadello, Joseph J; Eghtesady, Pirooz
2018-03-01
The effects of pregnancy on autograft dilatation and neoaortic valve function in patients with a Ross procedure have not been studied. We sought to evaluate the effect of pregnancy on autograft dilatation and valve function in these patients with the goal of determining whether pregnancy is safe after the Ross procedure. A retrospective chart review of female patients who underwent a Ross procedure was conducted. Medical records for 51 patients were reviewed. Among the 33 patients who met inclusion criteria, 11 became pregnant after surgery and 22 did not. Echocardiographic reports were used to record aortic root diameter and aortic insufficiency before, during, and after pregnancy. Patient's charts were reviewed for reinterventions and complications. Primary endpoints included reinterventions, aortic root dilation of ≥5 cm, aortic insufficiency degree ≥ moderate, and death. There were 18 pregnancies carried beyond 20 weeks in 11 patients. There was no significant difference in aortic root diameter between nulliparous patients and parous patients prior to their first pregnancy (3.53 ± 0.44 vs 3.57 ± 0.69 cm, P = .74). There was no significant change in aortic root diameter after first pregnancy (3.7 ± 0.4 cm, P = .056) although there was significant dilatation after the second (4.3 ± 0.7 cm, P = .009) and third (4.5 ± 0.7 cm, P = .009) pregnancies. Freedom from combined endpoints was significantly higher for patients in the pregnancy group than those in the nonpregnancy group (P = .002). Pregnancy was not associated with significantly increased adverse events in patients following the Ross procedure. Special care should be taken after the first pregnancy, as multiparity may lead to increased neoaortic dilatation. © 2017 Wiley Periodicals, Inc.
19. Drift-Scale THC Seepage Model
Energy Technology Data Exchange (ETDEWEB)
C.R. Bryan
2005-02-17
The purpose of this report (REV04) is to document the thermal-hydrologic-chemical (THC) seepage model, which simulates the composition of waters that could potentially seep into emplacement drifts, and the composition of the gas phase. The THC seepage model is processed and abstracted for use in the total system performance assessment (TSPA) for the license application (LA). This report has been developed in accordance with ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Post-Processing Analysis for THC Seepage) Report Integration'' (BSC 2005 [DIRS 172761]). The technical work plan (TWP) describes planning information pertaining to the technical scope, content, and management of this report. The plan for validation of the models documented in this report is given in Section 2.2.2, ''Model Validation for the DS THC Seepage Model,'' of the TWP. The TWP (Section 3.2.2) identifies Acceptance Criteria 1 to 4 for ''Quantity and Chemistry of Water Contacting Engineered Barriers and Waste Forms'' (NRC 2003 [DIRS 163274]) as being applicable to this report; however, in variance to the TWP, Acceptance Criterion 5 has also been determined to be applicable, and is addressed, along with the other Acceptance Criteria, in Section 4.2 of this report. Also, three FEPS not listed in the TWP (2.2.10.01.0A, 2.2.10.06.0A, and 2.2.11.02.0A) are partially addressed in this report, and have been added to the list of excluded FEPS in Table 6.1-2. This report has been developed in accordance with LP-SIII.10Q-BSC, ''Models''. This report documents the THC seepage model and a derivative used for validation, the Drift Scale Test (DST) THC submodel. The THC seepage model is a drift-scale process model for predicting the composition of gas and water that could enter waste emplacement drifts and the effects of mineral
20. Drift-Scale THC Seepage Model
International Nuclear Information System (INIS)
C.R. Bryan
2005-01-01
The purpose of this report (REV04) is to document the thermal-hydrologic-chemical (THC) seepage model, which simulates the composition of waters that could potentially seep into emplacement drifts, and the composition of the gas phase. The THC seepage model is processed and abstracted for use in the total system performance assessment (TSPA) for the license application (LA). This report has been developed in accordance with ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Post-Processing Analysis for THC Seepage) Report Integration'' (BSC 2005 [DIRS 172761]). The technical work plan (TWP) describes planning information pertaining to the technical scope, content, and management of this report. The plan for validation of the models documented in this report is given in Section 2.2.2, ''Model Validation for the DS THC Seepage Model,'' of the TWP. The TWP (Section 3.2.2) identifies Acceptance Criteria 1 to 4 for ''Quantity and Chemistry of Water Contacting Engineered Barriers and Waste Forms'' (NRC 2003 [DIRS 163274]) as being applicable to this report; however, in variance to the TWP, Acceptance Criterion 5 has also been determined to be applicable, and is addressed, along with the other Acceptance Criteria, in Section 4.2 of this report. Also, three FEPS not listed in the TWP (2.2.10.01.0A, 2.2.10.06.0A, and 2.2.11.02.0A) are partially addressed in this report, and have been added to the list of excluded FEPS in Table 6.1-2. This report has been developed in accordance with LP-SIII.10Q-BSC, ''Models''. This report documents the THC seepage model and a derivative used for validation, the Drift Scale Test (DST) THC submodel. The THC seepage model is a drift-scale process model for predicting the composition of gas and water that could enter waste emplacement drifts and the effects of mineral alteration on flow in rocks surrounding drifts. The DST THC submodel uses a drift
1. The Osservatorio Geofisico Sperimentale marine magnetic surveys in the Antarctic Seas
Directory of Open Access Journals (Sweden)
C. Zanolla
1999-06-01
Full Text Available About 40 000 km of marine magnetic and gradiometric data have been collected during eight geophysical surveys conducted since the Austral summer 1987/1988 in the circum-antarctic seas, by the research vessel OGS-Explora. For the most surveyed areas (Ross Sea, Southwestern Pacific Ocean, and Southern Scotia Sea, the analysis of the acquired data have contributed to clarify important aspects of their geological structure and tectonic evolution. The main scientific results, obtained combining other available geophysical data (multichannel seismic profiles and satellite-derived data, will be briefly illustrated.
2. Forced copulation results in few extrapair fertilizations in Ross's and lesser snow geese
Science.gov (United States)
Dunn, P.O.; Afton, A.D.; Gloutney, M.L.; Alisauskas, R.T.
1999-01-01
Extrapair paternity varies from 0 to over 70% of young among various populations of birds. Comparative studies have suggested that this variation is related to nesting density, breeding synchrony and the proportion of extrapair copulations. We used minisatellite DNA fingerprinting to examine levels of extrapair paternity in Ross's geese, Chen rossi, and lesser snow geese, C. caerulescens c. (hereafter snow geese) nesting in the largest known goose colony in the world. These geese have one of the highest known percentages of extrapair copulation (46-56% of all attempted copulations), and all of these appeared to be forced. Among all successful copulations, 33 and 38% were extrapair in Ross's and snow geese, respectively. Despite the high percentage of extrapair copulations, extrapair paternity was low in both Ross's and snow geese (2-5% of young). Extrapair paternity was not related to nest density in either species. However, in snow geese, extrapair paternity was more likely to occur in nests of females that nested asynchronously, either early or late in the season. This is one of a few reported examples of a negative relationship between extrapair paternity and breeding synchrony. Extrapair young also tended to come from eggs laid later in the clutch. Although forced extrapair copulations appear to be a relatively inefficient reproductive tactic for males, they may provide a reproductive advantage for some males.
3. Visioni vittoriane: il paesaggio fiorentino nelle opere di Janet Ross e Vernon Lee
Directory of Open Access Journals (Sweden)
Gabriele Corsani
2015-11-01
Full Text Available Fra l’ultimo scorcio dell’Ottocento e i primi decenni del Novecento Firenze e i suoi dintorni sono il soggetto privilegiato di una grande quantità di descrizioni, note di diario, racconti, opera di scrittori stranieri, in particolare inglesi, che si radicano nell’approdo elettivo di quei luoghi. Il testo presenta la traccia letteraria del paesaggio fiorentino nelle opere di Vernon Lee e Janet Ross, due tipiche rappresentanti di questa tendenza che hanno vissuto, attraverso vicende biografiche in qualche modo parallele, un’esperienza di intensa identificazione con il paesaggio fiorentino. Di Janet Ross, viene commentato Old Florence and Modern Tuscany, volume che raccoglie una serie di articoli pubblicati su alcune riviste inglesi e fornisce una efficace panoramica sull’interesse molto concreto di Janet Ross per il mondo rurale che la vede addirittura impegnata nella gestione della fattoria di Castagnolo, a Lastra a Signa. Più sfaccettato è il commento alle opere di Vernon Lee, di cui sono commentati passi da Vanitas. Polite Stories, Genius Loci, Hortus Vitae and Limbo, in virtù della maggiore ampiezza e complessità del suo mondo culturale. Ne sono cifra distintiva la associazione fra storia e realtà attraverso la dimensione del mistero, che risulta una delle chiavi di acccesso alla bellezza e alla vitalità del paesagggio e la capacità di cogliere il ritmo proprio dei luoghi e di entrare in reale sintonia con essi.
4. Preliminary results on the petrology and fluid inclusions of the Rossing uraniferous alaskites
International Nuclear Information System (INIS)
Cuney, M.
1980-01-01
Petrography, radioactivity distribution and fluid inclusions have been studied in three samples of the Rossing alaskites from the S.H. anomaly outside of the Rossing deposit. After the crystallization of the alaskitic magma which involved oligoclase, biotite, orthoclase and quartz, a deuteric alteration produced a quartz, microcline, albite, muscovite, calcite plus minus chlorite mineral association similar to those observed in several French uraniferous granites. Uranium redistribution occurred during this alteration. From fluid inclusions data, the pressure at the time of the intrusion is estimated to have been at least 6kbar for a temperature of 625 degrees Celsius. Reaction of the magma with the marbles of the Rossing formation led to the boiling of the magma by an increase in the CO 2 partial pressure as well as to its crystallization. Immiscibility between a dense saline (more than 30 per cent NaCl) and CO 2 -rich fluid is proposed to have occurred simultaneously or after the fluid oversaturation of the magma. Part of uraninite is formed at the magmatic stage, another part crystallized from the magmatic fluids in the biotite-rich selvages of the alaskites or in the uraninite-fluorite veins. Uraninite crystallization appears to be mainly controlled by the oxygen fugacity prevailing in the magma and in the surrounding rocks
5. Estimation of the banking sector competition in the CEE countries: The Panzar-Rosse approach
Directory of Open Access Journals (Sweden)
Arben Mustafa
2017-12-01
Full Text Available Competitive conditions in the banking sectors in the light of transition process in the Central and Eastern Europe countries (CEE has been subject of interest for researchers and policy-makers, especially upon entry of foreign banks and concentrated markets. In this paper the Panzar-Rosse approach is used to assess competition of banking sectors in CEE. By using General Method of Moments on the panel data for 300 banks for the period 1999-2009, empirical evidence indicates that banks operating in the CEE exert monopoly behaviour. From the methodological point of view, the findings suggest that using a price equation or controlling for total assets in a Panzar-Rosse approach produces upwards biased and invalid estimates of the H-statistic. Therefore, further support is provided for maintaining a reducedform revenue equation when estimating a Panzar-Rosse model. The findings also suggest that banks operating in the non-EU countries of the CEE region have exerted stronger market power compared to the banks operating in the EU countries of this region. Policy-makers should improve competitive conditions and general ‘enabling’ environment for the banking sectors, especially the non-EU countries of the CEE region, while balancing competition-stability trade-off.
6. Persistent organic pollutants in soils and sediments from James Ross Island, Antarctica
International Nuclear Information System (INIS)
Klanova, Jana; Matykiewiczova, Nina; Macka, Zdenek; Prosek, Pavel; Laska, Kamil; Klan, Petr
2008-01-01
Soil and sediment samples from James Ross Island were analyzed for their PCB, OCP and PAH contents. Soil concentrations ranged between 0.51 and 1.82 ng g -1 for seven indicator PCB congeners, between 0.49 and 1.34 ng g -1 for HCH congeners, between 0.51 and 3.68 ng g -1 for the sum of p,p'-DDT, DDE, and DDD, and between 34.9 and 171 ng g -1 for the sum of 16 EPA PAHs. Sediment levels from 0.32 to 0.83 ng g -1 were found for PCBs, from 0.14 to 0.76 ng g -1 for HCHs, from 0.19 to 1.15 ng g -1 for DDTs, and from 1.4 to 205 ng g -1 for PAHs. A prevalence of low-mass PAHs, less chlorinated PCBs, and more volatile chemicals indicates that the long-range atmospheric transport from populated areas of Africa, South America, and Australia is the most probable contamination source for the solid matrices in James Ross Island. - A survey of soil, sediment and air contamination in James Ross Island, Antarctica serves as a baseline study for evaluation of an anthropogenic impact of the new research facility
7. ASSESSMENT OF SEA ICE FREEBOARD AND THICKNESS IN MCMURDO SOUND, ANTARCTICA, DERIVED BY GROUND VALIDATED SATELLITE ALTIMETER DATA
Directory of Open Access Journals (Sweden)
D. Price
2012-07-01
Full Text Available This investigation employs the use of ICESat to derive freeboard measurements in McMurdo Sound in the western Ross Sea, Antarctica, for the time period 2003-2009. Methods closely follow those previously presented in the literature but are complemented by a good understanding of general sea ice characteristics in the study region from extensive temporal ground investigations but with limited spatial coverage. The aim of remote sensing applications in this area is to expand the good knowledge of sea ice characteristics within these limited areas to the wider McMurdo Sound and western Ross Sea region. The seven year Austral Spring (September, October, and November investigation is presented for sea ice freeboard alone. An interannual comparison of mean freeboard indicates an increase in multiyear sea ice freeboard from 1.08 m in 2003 to 1.15 m in 2009 with positive and negative variation in between. No significant trend was detected for first year sea ice freeboard. Further, an Envisat imagery investigation complements the freeboard assessment. The multiyear sea ice was observed to increase by 254 % of its original 2003 area, as firstyear sea ice persisted through the 2004 melt season into 2005. This maximum coverage then gradually diminished by 2009 to 20 % above the original 2003 value. The mid study period increase is likely attributed to the passage of iceberg B-15A minimising oceanic pressures and preventing sea ice breakout in the region.
8. Longevity of Emplacement Drift Ground Support Materials
International Nuclear Information System (INIS)
D.H.Tang
2001-01-01
The purpose of this analysis is to evaluate the factors affecting the longevity of emplacement drift ground support materials and to develop a basis for the selection of materials for ground support that will function throughout the preclosure period of a potential repository at Yucca Mountain. REV 01 ICN 01 of this analysis is developed in accordance with AP-3.10Q, Analyses and Models, Revision 2, ICN 4, and prepared in accordance with the Technical Work Plan for Subsurface Design Section FY 01 Work Activities (CRWMS M and O 2001a). The objective of this analysis is to update the previous analysis (CRWMS M and O 2000a) to account for related changes in the Ground Control System Description Document (CRWMS M and O 2000b), the Monitored Geologic Repository Project Description Document, which is included in the Requirements and Criteria for Implementing a Repository Design that can be Operated Over a Range of Thermal Modes (BSC 2001), input information, and in environmental conditions, and to provide updated information on candidate ground support materials. Candidate materials for ground support are carbon steel and cement grout. Steel is mainly used for steel sets, lagging, channel, rock bolts, and wire mesh. Cement grout is only considered in the case of grouted rock bolts. Candidate materials for the emplacement drift invert are carbon steel and granular natural material. Materials are evaluated for the repository emplacement drift environment based on the updated thermal loading condition and waste package design. The analysis consists of the following tasks: (1) Identify factors affecting the longevity of ground support materials for use in emplacement drifts. (2) Review existing documents concerning the behavior of candidate ground support materials during the preclosure period. (3) Evaluate impacts of temperature and radiation effects on mechanical and thermal properties of steel. Assess corrosion potential of steel at emplacement drift environment. (4
9. Parametric decay of lower hybrid wave into drift waves
International Nuclear Information System (INIS)
Sanuki, Heiji.
1976-12-01
A dispersion relation describing the parametric decay of a lower hybrid wave into an electrostatic drift wave and a drift Alfven wave is derived for an inhomogeneous magnetized plasma. Particularly the stimulated scattering of a drift Alfven wave in such a plasma was investigated in detail. The resonance backscattering instability is found to yield the minimum threshold. (auth.)
10. Passive appendages generate drift through symmetry breaking
Science.gov (United States)
Lācis, U.; Brosse, N.; Ingremeau, F.; Mazzino, A.; Lundell, F.; Kellay, H.; Bagheri, S.
2014-10-01
Plants and animals use plumes, barbs, tails, feathers, hairs and fins to aid locomotion. Many of these appendages are not actively controlled, instead they have to interact passively with the surrounding fluid to generate motion. Here, we use theory, experiments and numerical simulations to show that an object with a protrusion in a separated flow drifts sideways by exploiting a symmetry-breaking instability similar to the instability of an inverted pendulum. Our model explains why the straight position of an appendage in a fluid flow is unstable and how it stabilizes either to the left or right of the incoming flow direction. It is plausible that organisms with appendages in a separated flow use this newly discovered mechanism for locomotion; examples include the drift of plumed seeds without wind and the passive reorientation of motile animals.
11. Hole drift mobility in poly(hexylphenylsilane)
International Nuclear Information System (INIS)
Kunimi, Y.; Seki, S.; Tagawa, S.
2000-01-01
Poly(n-alkylphenylsilane)s in which n-alkyl were changed from methyl to octyl were polymerized. Hole transport properties of poly(alkyllphenylsilane)s were systematically studied by the DC time-of-flight (TOF) technique. While the hole drift mobility of poly(methylphenylsilane) increased monotonously in entire field, those of poly(hexylphenylsilane) and poly(octylphenylsilane) decreased with increase in the field strength. Temperature dependence of hole drift mobility in those polymers was small. On the basis of Baessler's disorder formalism the mobility was analyzed quantitatively to disserve complex contributions of charge transport. The analyzed results indicated that with increase in the length of n-alkyl side-groups, the energetic disorder of hopping sites became smaller and the disorder of distance between hopping sites became larger. These results were supported by the results obtained by UV absorption measurement and positron annihilation life-time spectroscopy measurement. (author)
12. Electromagnetic nonlinear gyrokinetics with polarization drift
International Nuclear Information System (INIS)
Duthoit, F.-X.; Hahm, T. S.; Wang, Lu
2014-01-01
A set of new nonlinear electromagnetic gyrokinetic Vlasov equation with polarization drift and gyrokinetic Maxwell equations is systematically derived by using the Lie-transform perturbation method in toroidal geometry. For the first time, we recover the drift-kinetic expression for parallel acceleration [R. M. Kulsrud, in Basic Plasma Physics, edited by A. A. Galeev and R. N. Sudan (North-Holland, Amsterdam, 1983)] from the nonlinear gyrokinetic equations, thereby bridging a gap between the two formulations. This formalism should be useful in addressing nonlinear ion Compton scattering of intermediate-mode-number toroidal Alfvén eigenmodes for which the polarization current nonlinearity [T. S. Hahm and L. Chen, Phys. Rev. Lett. 74, 266 (1995)] and the usual finite Larmor radius effects should compete
13. Clean industrial room for drift tube assembling
International Nuclear Information System (INIS)
Glonti, G.L.; Gongadze, A.L.; Evtukhovich, P.G.
2001-01-01
Description of a clean industrial room for assembly of drift tubes for the muon spectrometer of the ATLAS experiment is presented. High quality specifications on the detectors to be produced demanded creation of a workplace with stable temperature and humidity, as well as minimum quantity of dust in the room. Checking of parameters of intra-room air during long period of continuous work has confirmed correctness of the designed characteristics of the climatic system installed in the clean room. The room large volume (∼ 190 m 3 ), the powerful and flexible climatic system, and simplicity of service allow assembling of detectors with length up to 5 m. Subsequent checking of functionality of the assembled detectors has shown high quality of assembling (the amount of rejected tubes does not exceed 2%). It demonstrates conformity to the assembling quality requirements for mass production of drift chambers for the muon spectrometer. (author)
14. Clean Industrial Room for Drift Tube Assembling
CERN Document Server
Glonti, GL; Evtoukhovitch, P G; Kroa, G; Manz, A; Potrap, I N; Rihter, P; Stoletov, G D; Tskhadadze, E G; Chepurnov, V F; Chirkov, A V; Shelkov, G A
2001-01-01
Description of a clean industrial room for assembly of drift tubes for the muon spectrometer of the ATLAS experiment is presented. High quality specifications on the detectors to be produced demanded creation of a workplace with stable temperature and humidity, as well as minimum quantity of dust in the room. Checking of parameters of intra-room air during long period of continuous work has been confirmed correctness of the designed characteristics of the climatic system installed in the clean room. The room large volum (\\sim 190 m^3), the powerful and flexible climatic system, and simplicity of service allow assembling of detectors with length up to 5 m. Subsequent checking of functionality of the assembled detectors has shown high quality of assembling (the amount of rejected tubes does not exceed 2 %). It demonstrates conformity to the assembling quality requirements for mass production of drift chambers for the muon spectrometer.
15. Toroidal effects on drift wave turbulence
Energy Technology Data Exchange (ETDEWEB)
LeBrun, M.J.; Tajima, T.; Gray, M.G.; Furnish, G.; Horton, W.
1992-09-23
The universal drift instability and other drift instabilities driven by density and temperature gradients in a toroidal system are investigated in both linear and nonlinear regimes via particle simulation. Runs in toroidal and cylindrical geometry show dramatic differences in plasma behavior, primarily due to the toroidicity-induced coupling of rational surfaces through the poloidal mode number m. In the toroidal system studied, the eigenmodes are seen to possess (i) an elongated, nearly global radial extent (ii) a higher growth rate than in the corresponding cylindrical system, (iii) an eigenfrequency nearly constant with radius, (iv) a global temperature relaxation and enhancement of thermal heat conduction. Most importantly, the measured Xi shows an increase with radius and an absolute value on the order of that observed in experiment. On the basis of our observations, we argue that the increase in Xi with radius observed in experiment is caused by the global nature of heat convection in the presence of toroidicity-induced mode coupling.
16. Bottle appeal drifts across the Pacific
Science.gov (United States)
Ebbesmeyer, Curtis; Ingraham, W. James, Jr.; McKinnon, Richard; Okubo, Akira; Wang, Dong-Ping; Strickland, Richard; Willing, Peter
Pacific drift currents were used by a group of oceanographers to estimate the path of a drift bottle that was found on a beach of Barkley Sound in Vancouver Island by Richard Strickland on June 10, 1990. The Chinese rice wine bottle, which remained unopened until December 18, 1991, contained six leaflets, one appealing for the release of China's well-known dissident, Wei Jingsheng. The bottle was one of thousands set adrift as part of a propaganda effort from the islands of Quemoy and Matsu off mainland China shortly after Wei was sentenced in 1979 to 15 years in prison (see Figure 1 for locations). Wei was in poor health and still in prison when the bottle made its way across the Pacific Ocean.
17. The drift-flux correlation package MDS
International Nuclear Information System (INIS)
Hoeld, A.
2001-01-01
Based on the SONNENBURG drift-flux correlation, developed at GRS/Garching (Germany), a comprehensive drift-flux correlation package (MDS) has been established. Its aim is to support thermal-hydraulic mixture-fluid models, models being used for the simulation of the steady state and transient behaviour of characteristic thermal-hydraulic parameters of single- or two-phase fluids flowing along coolant channels of different types (being, e.g., parts of NPP-s, steam generators etc.). The characteristic properties of this package with respect to the behaviour at co- and counter-current flow, its inverse solutions needed for steady state simulations, its behaviour when approaching the lower or upper boundary of a two-phase region, its verification and behaviour with respect to other correlations will be discussed. An adequate driver code, MDSDRI, has been established too, allowing to test the package very thoroughly out of the complex thermal-hydraulic codes. (author)
18. Ionospheric drift measurements: Skymap points selection
Czech Academy of Sciences Publication Activity Database
Kouba, Daniel; Boška, Josef; Galkin, I. A.; Santolík, Ondřej; Šauli, Petra
2008-01-01
Roč. 43, č. 1 (2008), RS1S90/1-RS1S90/11 ISSN 0048-6604 R&D Projects: GA ČR GA205/06/1619; GA ČR GA205/06/1267; GA AV ČR IAA300420504 Grant - others:GA MŠk(CZ) OC 296; MIERS(XE) COST 296 Institutional research plan: CEZ:AV0Z30420517 Keywords : digisonde drift measurement * plasma drift * radio sounding * ionosphere * Doppler shift * skymap processing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.092, year: 2008 http://www.agu.org/pubs/crossref/2008/2007RS003633.shtml
19. Pulsar magnetic alignment. The drifting subpulses
International Nuclear Information System (INIS)
Jones, P.B.
1977-01-01
According to Ruderman and Sutherland (Ap.J.;196:51 (1975)) the subpulse drift observed in certain pulsars is a consequence of the circulation around the magnetic axis of electron-positron discharges occurring within an acceleration region near the polar cap. The predicted period of circulation P 3 is of the correct order of magnitude, but the sense of circulation and therefore the direction of subpulse drift is not consistent with indirect evidence, from observed integrated pulse widths, on the variation with pulsar age of the angle between the spin and magnetic axes. It is shown that this problem is resolved by a model of the acceleration electric field based on space charge limited ion flow. (author)
20. The drift-flux correlation package MDS
Energy Technology Data Exchange (ETDEWEB)
Hoeld, A. [Bernaysstr. 16A, Munich, F.R. (Germany)
2001-07-01
Based on the SONNENBURG drift-flux correlation, developed at GRS/Garching (Germany), a comprehensive drift-flux correlation package (MDS) has been established. Its aim is to support thermal-hydraulic mixture-fluid models, models being used for the simulation of the steady state and transient behaviour of characteristic thermal-hydraulic parameters of single- or two-phase fluids flowing along coolant channels of different types (being, e.g., parts of NPP-s, steam generators etc.). The characteristic properties of this package with respect to the behaviour at co- and counter-current flow, its inverse solutions needed for steady state simulations, its behaviour when approaching the lower or upper boundary of a two-phase region, its verification and behaviour with respect to other correlations will be discussed. An adequate driver code, MDSDRI, has been established too, allowing to test the package very thoroughly out of the complex thermal-hydraulic codes. (author)
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|
https://www.icts.res.in/people/gautam-bhattacharyya
|
PEOPLE Program Committee (Former)
Saha Institute of Nuclear Physics, Kolkata
Research Interests:
Gautam Bhattacharyya (b. 1966) is a particle phenomenologist. He got his Ph.D. from Calcutta University in 1993, and held postdoctoral positions at CERN, Geneva, Switzerland (1994-95) and INFN Pisa, Italy (1996-97) before joining Saha Institute of Nuclear Physics as a faculty in 1998.
Gautam's main area of research is Physics beyond the Standard Model'. He has worked extensively in the phenomenological aspects of Super symmetry and Extra Dimension and is currently investing most of his time in exploring the synergy between collider (mainly, LHC)' and flavor' physics. Of late, he has written an extensive review on different avenues of Electroweak Symmetry Breaking' by comparing and contrasting Super symmetric Higgs, Little Higgs, Holographic Higgs and Higgsless models.
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https://www.physicsforums.com/threads/translating-cumulative-rotations-into-pauli-operators.770177/
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# Translating cumulative rotations into Pauli operators
1. Sep 11, 2014
### Strilanc
I want to write a program that, given the tracked position of a cube being rotated, applies analogous operations to a single qubit.
The issue I'm running into is that, although operations correspond to rotations on the Bloch sphere, the mapping isn't one-to-one. So when I try to map back to operations, there are issues like... the path you take between two rotations affects the cumulative operation.
Is there a mapping from orientations/rotations to single qubit operations that is continuous, commutative, associative, and can reach all operations (up to a global phase factor)? Is there a particularly *simple* mapping?
What I'm using at the moment is [[c + s*z, s*(x - 1j*y)], [s*(x + 1j*y), c - s*z]] where <x,y,z> is the axis to rotate around to get from one orientation to the next, theta is how much to rotate, c is cos(theta), and s is i*sin(theta).
2. Sep 11, 2014
### DrDu
Well, rotations aren't commutative.
The matrix you are using is good and the parametrization in terms of axis and angle, too. However, the cos and sin terms should contain theta/2, not theta itself.
3. Sep 11, 2014
### Strilanc
Ah, commutativity isn't the property I want.
What I want is "different paths and discretizations between two orientations give the same net operation". So, I should be able to twirl the cube all kinds of crazy ways quickly and slowly while computing small deltas to keep the qubit matching it, but when I stop and return the cube to the starting orientation then the qubit should also be back at its starting value.
For example, I've noticed that if I just kind of wobble the cube's front face around the imaginary axis poking through it that the qubit does not also wobble: it drifts. A good example is that applying Y then Z then X gets the cube back in the same orientation, but adds a factor of -1 to the qubit's state. That factor is technically unobservable, but I want to visualize the qubit in an intuitive way and it *looks* like a big observable effect.
I've noticed that a factor of c+s on everything cancels out that -1, but not the wobbly-drift. I also tried purposefully canceling any rotations on |0> (but still allowing it to be negative). That worked quite well, but I don't think it will work if I try to use it in entangled multi-qubit systems because I'm not sure it's even linear.
4. Sep 11, 2014
### The_Duck
There is no continuous one-to-one mapping between SU(2) matrices (which represent the possible operations on a qubit) and rotations. The set of rotations is in one-to-one correspondence with the group of SO(3) matrices. But the Lie groups SU(2) and SO(3) are topologically distinct; for example SU(2) is simply connected while SO(3) is not. There is a continuous *two*-to-one mapping from SU(2) to SO(3), but not a continuous one-to-one mapping.
5. Sep 11, 2014
### Strilanc
What's the continuous two-to-one mapping? The one I already have? Is the two-to-one-ness just a factor of +-1?
6. Sep 11, 2014
### The_Duck
It's hard for me to read your notation, but the two-to-one mapping is given for example here: http://www.nyu.edu/classes/tuckerman/quant.mech/lectures/lecture_6/node4.html . It's two-to-one because the angle $\alpha$ can range from $0$ to $4 \pi$.
Yes, the two-to-one-ness is because of an overall factor of $\pm 1$. Say you pick an axis and consider a continuous family of rotations around that axis, ranging from an angle of $0$ to an angle of $2 \pi$. Then you ask what the corresponding continuous family of SU(2) matrices is. You will find that the corresponding family of SU(2) matrices starts with the identity matrix $1$ but ends, not at the identity matrix, but at $-1$.
7. Sep 11, 2014
### Strilanc
Yup, that's it. Basically just $I \cdot \cos{\frac{\theta}{2}} + i \hat{v} \vec{\sigma} \sin{\frac{\theta}{2}}$, with $\hat{v}$ being the axis and $\theta$ the angle and $\vec{\sigma}$ the vector of pauli matrices.
8. Sep 11, 2014
### DrDu
From what I understood you weren't interested in global phase factors (the -1 for a 2pi rotation) but in some mysterious wobbling?
9. Sep 11, 2014
### Strilanc
Well, because I'm trying to make a visualization, the interest is more in making the mapping visually simple. I didn't really communicate that well. Various properties are useful, with continuity being more important than a global phase factor slowly accumulating. But if I could also get rid of the phase factor, that's even better.
The "wobbling" refers to a motion I'm applying to the cube, which is being interpreted as operations that perturb the qubit by small amounts. The operations don't cancel out, despite the cube staying near and returning to the same orientation, and instead accumulate global phase. Apparently that's unavoidable, unless I want to sacrifice continuity.
For example, one way to ensure a phase factor didn't accumulate would be to get from orientation A to orientation B by always returning to a fixed orientation C in between. But this would introduce singularities where the qubit's state would flip wildly from small motions around a pole.
10. Sep 22, 2014
### Strilanc
I found a slight improvement, I think.
The mapping mentioned above, $I \cdot \cos{\frac{\theta}{2}} + i \hat{v} \vec{\sigma} \sin{\frac{\theta}{2}}$),is actually the one used to go from angle-axis rotations to quaternion rotations.
Pauli matrices are similar to quaternions, in that if you multiply each matrix by $i$ then you get something that squares to -1 and they commute in the same way that the quaternions i, j, and k do. However, because the mapping is going from rotations to quaternions and quaternions are imaginary-scaled Pauli matrices, the result is that a half X rotation is no longer just a logical NOT... it also gets a phase factor.
The simplest thing that could fix this was to just try to cancel the phase factor by multiplying by $e^{i \frac{\theta}{2}}$... and that works! In fact, it causes the expression to simplify quite a bit because half-angle identities come into play and get rid of the divisions inside the sine functions. The result is this mapping:
$\frac{(I + \hat{v} \vec{\sigma}) + e^{i \theta} (I - \hat{v} \vec{\sigma})}{2}$
Where $I$ is the identity matrix, $\vec{\sigma}$ is the vector of Pauli matrices, $\hat{v}$ is the axis to rotate around (being used to scale the matrices), and $\theta$ is how much to rotate around that axis.
That mapping gives the correct cumulative operations, although of course you can gain phase factors due to the fact that XYZ=i.
Similar Discussions: Translating cumulative rotations into Pauli operators
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https://gemseo.readthedocs.io/en/stable/examples/formulations/plot_doe_sobieski_mdf_example.html
|
# MDF-based DOE on the Sobieski SSBJ test case¶
from __future__ import division, unicode_literals
from matplotlib import pyplot as plt
from gemseo.api import configure_logger, create_discipline, create_scenario
from gemseo.problems.sobieski.core import SobieskiProblem
configure_logger()
Out:
<RootLogger root (INFO)>
## Instantiate the disciplines¶
First, we instantiate the four disciplines of the use case: SobieskiPropulsion, SobieskiAerodynamics, SobieskiMission and SobieskiStructure.
disciplines = create_discipline(
[
"SobieskiPropulsion",
"SobieskiAerodynamics",
"SobieskiMission",
"SobieskiStructure",
]
)
## Build, execute and post-process the scenario¶
Then, we build the scenario which links the disciplines with the formulation and the optimization algorithm. Here, we use the BiLevel formulation. We tell the scenario to minimize -y_4 instead of minimizing y_4 (range), which is the default option.
We need to define the design space.
design_space = SobieskiProblem().read_design_space()
### Instantiate the scenario¶
scenario = create_scenario(
disciplines,
formulation="MDF",
objective_name="y_4",
design_space=design_space,
maximize_objective=True,
scenario_type="DOE",
)
### Set the design constraints¶
for constraint in ["g_1", "g_2", "g_3"]:
### Execute the scenario¶
Use provided analytic derivatives
scenario.set_differentiation_method("user")
### Multiprocessing¶
It is possible to run a DOE in parallel using multiprocessing, in order to do this, we specify the number of processes to be used for the computation of the samples.
Warning
The multiprocessing option has some limitations on Windows. For Python versions < 3.7 and Numpy < 1.20.0, subprocesses may get hung randomly during execution. It is strongly recommended to update your environment to avoid this problem. The features MemoryFullCache and HDF5Cache are not available for multiprocessing on Windows. As an alternative, we recommend the method DOEScenario.set_optimization_history_backup().
n_processes = 4
We define the algorithm options. Here the criterion = center option of pyDOE centers the points within the sampling intervals.
algo_options = {
"criterion": "center",
# Evaluate gradient of the MDA
# with coupled adjoint
"eval_jac": True,
# Run in parallel on 4 processors
"n_processes": n_processes,
}
run_inputs = {"n_samples": 30, "algo": "lhs", "algo_options": algo_options}
Warning
When running a parallel DOE on Windows, the execution must be protected to avoid recursive calls:
if __name__ == "__main__":
scenario.execute(run_inputs)
Out:
INFO - 14:42:59:
INFO - 14:42:59: *** Start DOE Scenario execution ***
INFO - 14:42:59: DOEScenario
INFO - 14:42:59: Disciplines: SobieskiPropulsion SobieskiAerodynamics SobieskiMission SobieskiStructure
INFO - 14:42:59: MDOFormulation: MDF
INFO - 14:42:59: Algorithm: lhs
INFO - 14:42:59: Optimization problem:
INFO - 14:42:59: Minimize: -y_4(x_shared, x_1, x_2, x_3)
INFO - 14:42:59: With respect to: x_shared, x_1, x_2, x_3
INFO - 14:42:59: Subject to constraints:
INFO - 14:42:59: g_1(x_shared, x_1, x_2, x_3) <= 0.0
INFO - 14:42:59: g_2(x_shared, x_1, x_2, x_3) <= 0.0
INFO - 14:42:59: g_3(x_shared, x_1, x_2, x_3) <= 0.0
INFO - 14:42:59: DOE sampling: 0%| | 0/30 [00:00<?, ?it]
INFO - 14:42:59: Running DOE in parallel on n_processes = 4
INFO - 14:42:59: DOE sampling: 3%|▎ | 1/30 [00:00<00:00, 65.28 it/sec, obj=285]
INFO - 14:42:59: DOE sampling: 13%|█▎ | 4/30 [00:00<00:00, 45.71 it/sec, obj=344]
INFO - 14:42:59: DOE sampling: 17%|█▋ | 5/30 [00:00<00:00, 37.71 it/sec, obj=235]
INFO - 14:42:59: DOE sampling: 23%|██▎ | 7/30 [00:00<00:00, 32.63 it/sec, obj=429]
INFO - 14:43:00: DOE sampling: 30%|███ | 9/30 [00:01<00:00, 26.89 it/sec, obj=538]
INFO - 14:43:00: DOE sampling: 37%|███▋ | 11/30 [00:01<00:00, 23.43 it/sec, obj=306]
INFO - 14:43:00: DOE sampling: 43%|████▎ | 13/30 [00:01<00:00, 21.35 it/sec, obj=556]
INFO - 14:43:00: DOE sampling: 50%|█████ | 15/30 [00:01<00:00, 18.26 it/sec, obj=481]
INFO - 14:43:00: DOE sampling: 60%|██████ | 18/30 [00:01<00:00, 16.00 it/sec, obj=1.07e+3]
INFO - 14:43:01: DOE sampling: 67%|██████▋ | 20/30 [00:02<00:00, 14.87 it/sec, obj=602]
INFO - 14:43:01: DOE sampling: 73%|███████▎ | 22/30 [00:02<00:00, 13.32 it/sec, obj=1.18e+3]
INFO - 14:43:01: DOE sampling: 83%|████████▎ | 25/30 [00:02<00:00, 12.54 it/sec, obj=624]
INFO - 14:43:01: DOE sampling: 90%|█████████ | 27/30 [00:02<00:00, 11.37 it/sec, obj=606]
INFO - 14:43:01: DOE sampling: 97%|█████████▋| 29/30 [00:02<00:00, 10.88 it/sec, obj=485]
INFO - 14:43:01: DOE sampling: 100%|██████████| 30/30 [00:02<00:00, 10.66 it/sec, obj=405]
INFO - 14:43:01: Optimization result:
INFO - 14:43:01: Objective value = 485.49220045924955
INFO - 14:43:01: The result is feasible.
INFO - 14:43:01: Status: None
INFO - 14:43:01: Optimizer message: None
INFO - 14:43:01: Number of calls to the objective function by the optimizer: 30
INFO - 14:43:01: Constraints values:
INFO - 14:43:01: g_1 = [-0.11350951 -0.10812292 -0.1045109 -0.10204971 -0.10028641 -0.01838903
INFO - 14:43:01: -0.22161097]
INFO - 14:43:01: g_2 = -0.02400000000000002
INFO - 14:43:01: g_3 = [-0.33063157 -0.66936843 -0.73821755 -0.07789536]
INFO - 14:43:01: Design space:
INFO - 14:43:01: +----------+-------------+---------------------+-------------+-------+
INFO - 14:43:01: | name | lower_bound | value | upper_bound | type |
INFO - 14:43:01: +----------+-------------+---------------------+-------------+-------+
INFO - 14:43:01: | x_shared | 0.01 | 0.05400000000000001 | 0.09 | float |
INFO - 14:43:01: | x_shared | 30000 | 46500 | 60000 | float |
INFO - 14:43:01: | x_shared | 1.4 | 1.686666666666667 | 1.8 | float |
INFO - 14:43:01: | x_shared | 2.5 | 5.2 | 8.5 | float |
INFO - 14:43:01: | x_shared | 40 | 66.5 | 70 | float |
INFO - 14:43:01: | x_shared | 500 | 583.3333333333334 | 1500 | float |
INFO - 14:43:01: | x_1 | 0.1 | 0.185 | 0.4 | float |
INFO - 14:43:01: | x_1 | 0.75 | 0.9416666666666667 | 1.25 | float |
INFO - 14:43:01: | x_2 | 0.75 | 0.775 | 1.25 | float |
INFO - 14:43:01: | x_3 | 0.1 | 0.115 | 1 | float |
INFO - 14:43:01: +----------+-------------+---------------------+-------------+-------+
INFO - 14:43:01: *** DOE Scenario run terminated ***
Warning
On Windows, the progress bar may show duplicated instances during the initialization of each subprocess. In some cases it may also print the conclusion of an iteration ahead of another one that was concluded first. This is a consequence of the pickling process and does not affect the computations of the scenario.
### Plot the optimization history view¶
scenario.post_process("OptHistoryView", show=False, save=False)
Out:
<gemseo.post.opt_history_view.OptHistoryView object at 0x7f3b51f2afa0>
Tip
Each post-processing method requires different inputs and offers a variety of customization options. Use the API function get_post_processing_options_schema() to print a table with the attributes for any post-processing algo. Or refer to our dedicated page: Options for Post-processing algorithms.
### Plot the scatter matrix¶
scenario.post_process(
"ScatterPlotMatrix", show=False, save=False, variables_list=["y_4", "x_shared"]
)
Out:
<gemseo.post.scatter_mat.ScatterPlotMatrix object at 0x7f3b51dac610>
### Plot correlations¶
scenario.post_process("Correlations", show=False, save=False)
# Workaround for HTML rendering, instead of show=True
plt.show()
Out:
INFO - 14:43:04: Detected 10 correlations > 0.95
Total running time of the script: ( 0 minutes 6.263 seconds)
Gallery generated by Sphinx-Gallery
|
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|
http://mathhelpforum.com/calculus/63264-integration.html
|
1. ## Integration
Let $G(x)=\int_{0}^{x} f(x)dx$
The graph of f(x) is under the x axis from [-2,0]
Wouldn't the graph of G(x) be increasing on the interval of [-2,0] because
$G(x)=\int_{0}^{-2} f(x)dx=-\int_{-2}^{0} f(x) dx$ = -(-area)=positive area
But apparently the graph is decreasing on that interval. Can someone explain this to me? Thanks
2. Originally Posted by Linnus
Let $G(x)=\int_{0}^{x} f(x)dx$
The graph of f(x) is under the x axis from [-2,0]
Wouldn't the graph of G(x) be increasing on the interval of [-2,0] because
$G(x)=\int_{0}^{-2} f(x)dx=-\int_{-2}^{0} f(x) dx$ = -(-area)=positive area Mr F says: This is G(-2), NOT G(x).
But apparently the graph is decreasing on that interval. Can someone explain this to me? Thanks
Correct, it is indeed decreasing over the interval $-2 \leq x \leq 0$.
Consider:
$G(-2) = \int_{0}^{-2} f(x) \, dx = - \int^{0}_{-2} f(x) \, dx > 0$.
$G(-1) = \int_{0}^{-1} f(x) \, dx = - \int^{0}_{-1} f(x) \, dx > 0$.
But clearly G(-2) > G(-1) .......
3. Originally Posted by mr fantastic
Correct, it is indeed decreasing over the interval $-2 \leq x \leq 0$.
Consider:
$G(-2) = \int_{0}^{-2} f(x) \, dx = - \int^{0}_{-2} f(x) \, dx > 0$.
$G(-1) = \int_{0}^{-1} f(x) \, dx = - \int^{0}_{-1} f(x) \, dx > 0$.
But clearly G(-2) > G(-1) .......
Ah...that makes sense.
|
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|
https://brilliant.org/problems/huge-collision/
|
# Huge collision!
Three balls having masses $$2m$$, $$3m$$ and $$5m$$ having equal velocities $$v_0$$ collide with a block of wood of mass $$6m$$ which is at rest, in a perfectly elastic collision.
Now, this whole system of the balls and the block is moving with a velocity of $$v_1$$.
If the ratio $$\dfrac{v_0}{v_1}$$ is equal to $$\dfrac ab$$, where $$a$$ and $$b$$ are co-prime, find $$a+b$$.
×
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http://nrich.maths.org/7664/clue
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### Lunar Leaper
Gravity on the Moon is about 1/6th that on the Earth. A pole-vaulter 2 metres tall can clear a 5 metres pole on the Earth. How high a pole could he clear on the Moon?
### High Jumping
How high can a high jumper jump? How can a high jumper jump higher without jumping higher? Read on...
### Escape from Planet Earth
How fast would you have to throw a ball upwards so that it would never land?
# Slingshot
##### Stage: 5 Challenge Level:
If a projectile is fired at an angle of 45° to the horizontal then the initial speed of the projectile and the distance it travels is related by $d = \frac{v^2}{g}$.
Use the conservation of energy in order to find the speed of the stone. The energy stored in a strip which is extended by $\delta x$ is equal $E = \frac{k \delta x^2}{2}$.
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https://www.physicsforums.com/threads/easy-way-to-copy-files.36931/
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# Easy way to copy files?
1. ### aychamo
376
Easy way to copy files??
Hey guys
Is there an easy way to copy files in the method I'll mention in WinXP?
I have a folder, C:\MP3s that is arranged as:
C:\MP3s\Artist\Album\Songname.mp3
I keep a copy of this folder on my LAN, on F:\MP3s .. The problem is, say I add a few new songs in different albums, and I want to copy them over to the F:\MP3s, I can't find an easy way to do it.
If I just copy it over, my only option is to overwrite everything, which is *slow*. If I pick for it to not overwrite (and hit Shift-N to answer No to all), then it won't copy over anything because it treats the directories as files. I mean, say I have four songs currently in C:\MP3s\Beatles\Abbey Road\ (like I wouldn't have the whole album!), and I add a few more songs. If I try to copy the folder over from C:\MP3s, and I don't click on "Overwrite All", it won't copy the new songs from \Mp3s\Beatles\Abbey Road\ because it sees that I already have a Abbey Road folder, and doesn't check the files in it.
Is there a copy utility to "Synchronize" two network directories? Or to copy files that don't exist (and it does subdirectories, etc?) I played around with XCopy, but I couldn't find a set of command line arguments that suited me.
Any ideas? I appreciate it, and thank you.
2. ### Guybrush Threepwood
526
Total Commander has a very nice synchronize function
3. ### aychamo
376
Is TC free? :)
4. ### megashawn
505
why not just map the mp3 folder on the c drive as a network drive?
5. ### dduardo
1,918
Staff Emeritus
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https://www.physicsforums.com/threads/viscous-disc-paradox.843118/
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1. Nov 14, 2015
### snorkack
Which way does friction in a viscous disc operate?
Imagine a ring consisting of ringlets. First consider a case of a pair of nearby ringlets - in the same plane, both circular orbits.
If all particles of both ringlets are in circular orbits in the same plane, then they can never collide and therefore never exert any force. There is then zero temperature and zero viscosity.
Now suppose the viscosity is nonzero. What then?
By Third Law of Kepler, the inner ringlet should move faster.
Therefore, the inner ringlet should propel the outer ringlet ahead: the outer ringlet should expand and the inner one shrink.
But the problem is that the particles of rings, whether dust grains or gas molecules, are severally subject to Newton´s laws... and therefore also laws of Kepler. Including the Second.
While particles of inner ringlets are indeed faster than outer ringlet, they are so while they are in the inner ringlet, and do not meet outer ringlet.
The particles which can and do collide are those on elliptical orbit.
Considering two neighbouring circular ringlets and an elliptical ringlet tangent to both at its apsides.
The outer ringlet is slower than the inner, as per 3rd law - but the elliptical orbit at its apoapse is even slower, as per 2nd.
Therefore, the outer ringlet should be slowed down and shrink. And inner ringlet, by the same reasoning, should encounter the faster part of elliptical ringlet at periapse, speed up and expand.
So what´s the solution of the paradox? How should a viscous disc behave?
2. Nov 14, 2015
### my2cts
I guess a viscous disk rotating in a Newton potential by friction would convert kinetic energy into heat.
Thus it would heat up as its radius would shrink. Eventually it would be absorbed by the source of the Newton potential.
However I expect the matter to condense into clumps in which no friction occurs as long as it is in a circular orbital (no tidal forces).
I would also expect that the end result depends on how much matter is involved and on the size of the orbit.
This will also set the time scale of the evolution.
Of course it would be better to consult a text on planetary formation than to follow my guesses.
3. Nov 14, 2015
### Staff: Mentor
@my2cts: Angular momentum is conserved (neglecting relativistic effects like the angular momentum of radiated light), it won't fall in.
Angular momentum and energy scale with $L^2 \propto E^3$. Putting objects in different orbits together in a common orbit releases energy, pushing them apart would require energy. Therefore, your objects should get closer together.
Objects in different circular orbits will never collide, but you still get some interaction via gravity. It's not a simple "this is pushing this" however. See Saturn's rings for the complex interactions in such a disk.
4. Nov 14, 2015
### Chronos
Saturns rings are a good example. They are composed largely of water ice so any heating due to friction is not a major factor. The also orbit at a fairly leisurely pace the inside edge of the inner [C] ring has as orbital velocity of a little under 24 km/sec whereas the outside edge of the outer [A] ring has an orbital velocity of just over 16 km/sec. The ISS, by comparison circles the earth at a little less than 8 km/sec. The aggregate material that the rings are composed of vary in size, although not greatly. The smaller particle average less than a cm in size whereas the relatively rarer larger particle can be a meter or two across. It is beleived the larger variety are slowly broken apart or eventually migrate out beyond the rings. Orbital resonance with the moons of saturn are believed to protect the rings from any significant collapse or dispersal.
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https://nbviewer.jupyter.org/urls/www.numfys.net/media/notebooks/verlet_integration.ipynb
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Verlet Integration¶
Modules - Ordinary Differential Equations¶
Last edited: March 11th 2018
Can we solve Newton's second law $$m\frac{d^2}{dt^2}x(t)=F(x(t),t), \label{eq:1}$$ a second-order ODE, without resorting to Euler's method which re-casts the problem as two coupled, first-order ODEs?
Here, we employ the initial condition $x(t_0)=x_0$ and $v(t_0)=v_0$, and restrict our analysis to one dimension. Also, we assume for now that the force $F$ does not depend on the velocity $v$.
We can divide equation \eqref{eq:1} by the mass $m$ and write instead $$\frac{d^2}{dt^2}x(t)=a(x(t),t),$$ where $a(x,t)$ is the acceleration.
Example 1: $$\frac{d^2x}{dt^2}=-x+x^3+0.1\cos(t), \label{eq:2}$$ with the initial conditions $x(t_0)=0$ and $v(t_0)=0$.
In a fairly crude way, we now approximate the second derivative of $x(t)$ with respect to time, i.e. the acceleration, by \begin{aligned} \frac{d^2x}{dt^2}\bigg|_{t=t_n}=\frac{dv}{dt}\bigg|_{t=t_n}& \approx&\frac{v(t_n+h/2)-v(t_n-h/2)}{h} \\ &\approx&\frac{ \frac{x(t_n+h)-x(t_n)}{h} -\frac{x(t_n)-x(t_n-h)}{h} }{h}, \end{aligned} \label{eq:3} where we used the central difference approximation(s) $$\frac{dv}{dt}\bigg|_{t=t_n}\approx\frac{v(t_n+h/2)-v(t_n-h/2)}{h}$$ with $$v(t_n+h/2)\approx \frac{x(t_n+h)-x(t_n)}{h},\\ v(t_n-h/2)\approx \frac{x(t_n)-x(t_n-h)}{h}.$$
The above formulation follows the usual discretization $$t_n=t_0+n\cdot h~~~\mathrm{with}~~~n=0,1,2,3,...,N.$$ Again, this suggests the following abbreviation: $x_n=x(t_n)$.
With this in mind, substitution of expression \eqref{eq:3} into equation \eqref{eq:2} and subsequent multiplication by $h^2$ yields $$x_{n+1}-2x_n+x_{n-1}=h^2\left[-x_n+x_n^3+0.1\cos(t_n)\right],$$ where we evaluated equation \eqref{eq:2} at $t=t_n$. This results in the following recursive formulation of the solution $$x_{n+1}=2x_n-x_{n-1}+h^2\left[-x_n+x_n^3+0.1\cos(t_n)\right] \label{eq:4}$$ with $x_0=0$ and $v_0=0$.
Verlet Integration¶
More rigorously, one can derive the generalized version of the recursive formula \eqref{eq:4}, namely
$$\boxed{x_{n+1}=2x_n-x_{n-1}+h^2 a(x_n,t_n),} \label{eq:5}$$
by use of Taylor expansions about $x(t_n)$ (see Appendix). The Taylor-expansion method tells us that the local error we make in using the approximation \eqref{eq:5}, scales like $h^4$. This is, perhaps, surprisingly good.
The method \eqref{eq:5} is called Verlet integration. Often, it includes an acceleration term which does not depend explicitly on time: $a=a(x(t))$.
The remaining problem is now to use equation \eqref{eq:4} at $t=t_0$, i.e. at $n=0$, since we do not know the value of $x$ for $t<0$, in particular $x_{-1}$. Here, one can estimate the first value $x_1$ after the starting point $t_0$ by Taylor expansion of $x(t)$ at $t=t_0$: $$x_1=x_0+h v_0 + \frac{h^2}{2}a(x_0,t_0)+\mathcal{O}(h^3).$$ In our example, this becomes ($x_0=0$, $v_0=0$, $t_0=0$) $$x_1=x_0+h v_0 + \frac{h^2}{2}a(x_0,t_0)=\frac{h^2}{20}. \label{eq:6}$$ Thereafter, we can stick to the relation \eqref{eq:4} to find all other $x_n$.
(Note: The error of the approximation \eqref{eq:6} scales like $h^3$.)
Let's use \eqref{eq:4} and \eqref{eq:6} to solve \eqref{eq:2}:
In [2]:
%matplotlib inline
import numpy as np
import matplotlib.pyplot as plt
# Set common figure parameters
newparams = {'figure.figsize': (16, 6), 'axes.grid': True,
'lines.linewidth': 1.5, 'lines.linewidth': 2,
'font.size': 14}
plt.rcParams.update(newparams)
In [3]:
N = 100000 # number of steps
h = 0.001 # step size
t = np.zeros(N+1)
x = np.zeros(N+1)
# initial values
t_0 = 0
x_0 = 0
t[0] = t_0
x[0] = x_0
for n in range(N):
# Second grid point:
if n==0:
t[n+1] = h
x[n+1] = h**2/20.0
# Verlet integration
else:
t[n+1] = t[n] + h
x[n+1] = 2.0*x[n] - x[n-1] + h**2*(-x[n]+x[n]**3+0.1*np.cos(t[n]))
# Plot the solution
plt.plot(t,x)
plt.ylabel(r'$x(t)$')
plt.xlabel(r'$t$')
plt.grid();
Here we have chosen $h=0.001$ and $N=100\,000$, and so $t_N=100$. In the plot of $x(t)$, the discrete points have been connected by straight lines.
Question¶
What if the force, and hence the acceleration, also depends on the velocity $v$? In other words, let's look at $$\frac{d^2}{dt^2}x(t)=a(x(t),v(t),t),$$ with the initial conditions $x(t_0)=x_0$ and $v(t_0)=v_0$.
We approximate the left-hand side at $t=t_n$ just like before, and we approximate the right-hand side by $$a(x_n,v_n,t_n)\approx a\left( x_n, \frac{x_{n+1}-x_{n-1}}{2h}, t_n \right),$$ where we used a central difference approximation for $v_n$ again: $$\frac{dv}{dt}\bigg|_{t=t_n}\approx\frac{v(t_n+h)-v(t_n-h)}{2h}. \label{eq:7}$$
However, the error of the approximation \eqref{eq:7} scales like $h^2$, thereby reducing the overall accuracy of the method.
Again, we estimate $$x_1=x_0+h v_0 + \frac{h^2}{2}a(x_0,v_0,t_0).$$ Thereafter, we now use $$x_{n+1}=2x_n-x_{n-1}+h^2 a\left( x_n, \frac{x_{n+1}-x_{n-1}}{2h}, t_n \right) .$$ Note that we need to solve this equation for $x_{n+1}$ which is not always possible in analytical form, i.e. in closed form, if the problem is nonlinear.
Let us focus on a problem which is linear in $v$.
Example 2: $$\frac{d^2x}{dt^2}=-v-x^3$$ with the initial conditions $x_0=x(0)=10$ and $v_0=v(0)=0$. Using our above formalism, this reads in discretized form \begin{align*} x_{n+1}&=2x_n-x_{n-1}+h^2 \left( -\frac{x_{n+1}-x_{n-1}}{2h}-x_n^3 \right) \\ \Rightarrow x_{n+1}&=\frac{2x_n-(1-h/2)\,x_{n-1}-h^2 x_n^3}{1+h/2}. \end{align*} When combined with $x_0=10$ and $$x_1=x_0+h v_0 + \frac{h^2}{2}a(x_0,v_0,t_0)=10-500 h^2,$$ this determines the solution of the problem. This is implemented in the code below. In the code we choose $h=0.001$ and $N=3\,000$, and so $t_N=3.0$
In [4]:
N = 3000 # number of steps
h = 0.001 # step size
t = np.zeros(N+1)
x = np.zeros(N+1)
# initial values
t_0 = 0
x_0 = 10
t[0] = t_0
x[0] = x_0
for n in range(N):
# Second grid point:
if n==0:
t[n+1] = h
x[n+1]= 10.0-500.0*h**2
# Verlet integration
else:
t[n+1] = t[n] + h
x[n+1] = (2.0*x[n]-(1.0-h/2)*x[n-1]-h**2*x[n]**3)/(1+h/2.0)
# Plot the solution
plt.plot(t,x)
plt.ylabel(r'$x(t)$')
plt.xlabel(r'$t$')
plt.grid();
Summary¶
We have seen that there is more than one method (Euler's method) to solve ODEs. Verlet integration is often used to solve Newton's second law.
1. It provides higher accuracy than Euler's method.
2. It is more stable than Euler's method and
3. might require a nonlinear solve for $x_{n+1}$.
4. It can be extended in a straightforward manner to three-dimensional motion.
Appendix: Derivation of Verlet Formula with Taylor Series¶
Given the dynamics of $x(t)$ at $t=t_n$, let us approximate the values $x_{n-1}=x(t_n-h)$ and $x_{n+1}=x(t_n+h)$ by use of Taylor series at $x_{n}=x(t_n)$: \begin{eqnarray*} x(t_n-h)&=&x(t_n)+v(t_n) \cdot (-h)+\frac{a(t_n)}{2}\cdot (-h)^2+\frac{b(t_n)}{6}\cdot (-h)^3+\mathcal{O}(h^4), \\ x(t_n+h)&=&x(t_n)+v(t_n)\,h+\frac{a(t_n)}{2}h^2+\frac{b(t_n)}{6}h^3+\mathcal{O}(h^4), \end{eqnarray*} with \begin{align*} v(t_n)=\frac{dx}{dt}\bigg|_{t=t_n}, \quad a(t_n)=\frac{d^2x}{dt^2}\bigg|_{t=t_n}, \quad \text{and} \quad b(t_n)=\frac{d^3x}{dt^3}\bigg|_{t=t_n}. \end{align*} Adding these two equations and subsequent re-arranging of terms yields $$x(t_n+h)=2x(t_n)-x(t_n-h)+a(t_n)\,h^2+\mathcal{O}(h^4)$$ or, in different notation, $$x_{n+1}=2 x_n-x_{n-1}+h^2\,a(t_n)+\mathcal{O}(h^4).$$ This is our Verlet formula \eqref{eq:5} if we drop the higher-order terms $\mathcal{O}(h^4)$ and write $a(x(t_n),t_n)=a(x_n,t_n)$ instead of simply $a(t_n)$.
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http://jultika.oulu.fi/Record/nbnfi-fe2019091728578
|
Sorsa, A., Santa-aho, S., Wartiainen, J. et al. J Nondestruct Eval (2018) 37: 10. https://doi.org/10.1007/s10921-018-0463-7
### Effect of shot peening parameters to residual stress profiles and Barkhausen noise
Saved in:
Author: Sorsa, Aki1; Santa-aho, Suvi2; Wartiainen, Jukka3;
Organizations: 1Control Engineering, University of Oulu, Oulu, Finland
2Laboratory of Materials Science, Tampere University of Technology, Tampere, Finland
3Stresstech Oy, Vaajakoski, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 1.1 MB)
Language: English
Published: Springer Nature, 2018
Publish Date: 2019-09-17
Description:
# Abstract
The production of gear components includes numerous manufacturing operations which are carried out to ensure proper surface characteristics of components to deal with wear and fatigue. Surface shot peening is one way to increase the compressive residual stresses on the surface and thus ensure better wear and fatigue resistance. An experimental plan for shot peening was conducted to produce samples with varying surface characteristics. Residual stress profile and Barkhausen noise measurements were carried out for the samples. The objective of the study was to evaluate the interactions between the shot peening parameters studied, the residual stress profiles and the Barkhausen noise measurements. A multivariable regression analysis was applied for the task. Some remarkable correlations were found between the shot peening parameters, residual stress profile and Barkhausen noise features. The most important finding was that when the shot peening intensity was high enough, over 0.5 mmA, it dominated the shot peening coverage density parameter and thus no correlations could be gained. On the other hand, if the intensity parameter was lower than the limit of 0.5 mmA, the correlation between residual stress and Barkhausen noise measurements was remarkable. This means that the surface Barkhausen noise measurements could be used for the evaluation of the stress gradient in the shot peening process.
see all
Series: Journal of nondestructive evaluation
ISSN: 0195-9298
ISSN-E: 1573-4862
ISSN-L: 0195-9298
Volume: 37
Issue: 1
Article number: 10
DOI: 10.1007/s10921-018-0463-7
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http://mathhelpforum.com/algebra/98089-stumped-print.html
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# Stumped!
• August 14th 2009, 02:42 PM
epetrik
Stumped!
Teds Car Rental charges a fixed charge and so much per mile. Tara rented a car from Teds. She drove 150 miles and paid 65 dollars. Susan rented a car from Teds and drove 350 miles and paid 125 dollars. Determine a linear function that Teds uses for its charges.
• August 14th 2009, 03:55 PM
skeeter
Quote:
Originally Posted by epetrik
Teds Car Rental charges a fixed charge and so much per mile. Tara rented a car from Teds. She drove 150 miles and paid 65 dollars. Susan rented a car from Teds and drove 350 miles and paid 125 dollars. Determine a linear function that Teds uses for its charges.
two points ...
(150, 65)
(350, 125)
point-slope form ...
$y - y_1 = m(x - x_1)$
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http://tex.stackexchange.com/questions/144168/miktex-download-failure-toptesi-tar-lzma?answertab=active
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# MikTex Download Failure - toptesi.tar.lzma
I try to install Complete MiKTeX 2.9 But there is this:
Error: The operation could not be completed because the following file failed verification:
C:\...\mikTex\toptesi.tar.lzma
There is the same with the basic version.
How can I solve my problem?
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It seems you have downloaded the files to your hard disk and trying to install from there. Some files are corrupted. Try downloading again. – Harish Kumar Nov 10 '13 at 1:54
Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. – Harish Kumar Nov 10 '13 at 1:56
I try downloading again, but there is the same – Belochka Nov 10 '13 at 2:18
Try with a different MiKTeX repository … (and it would be nice, if you'd change your user name to a more expressive one). – Speravir Nov 10 '13 at 3:34
I tried with the different repositories, but there is also the same error – Belochka Nov 10 '13 at 11:41
## 1 Answer
Look up a different repository that lags behind a couple of days. Most of them have already copied the corrupted files (miktex-misc is also broken). The list of repositories has 188 entries, ftp.neowiz.com and elena.aut.ac.nz are the ones which have files dated older than 02-NOV-2013. The kiwi server worked for me.
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all the mirrors on the list have version 09-NOV-2013. I guess my only option is to wait until this is fixed? – John Peter Thompson Garcés Nov 10 '13 at 20:11
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https://www.physicsforums.com/threads/maxrecursion-workingprecision-error-in-mathematica-8.633842/
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# MaxRecursion(/WorkingPrecision?) Error in Mathematica 8
1. Sep 6, 2012
### muppet
I'm getting an error message that suggests my attempts to increase the variable MaxRecursion in NIntegrate aren't working.
I define
f[n_,b_]:=NIntegrate[q*BesselJ[0,q*b]*(-(2/(n (2+n) q^4))+(1-q^2)^(n/2) HeavisideTheta[1-q^2] ((2+n q^2)/(n (2+n) q^4)-Hypergeometric2F1[1,n/2,1+n/2,1-1/q^2]/(n q^2))),{q,0,Infinity},Method->"DoubleExponentialOscillatory",MaxRecursion->50,WorkingPrecision->30]
and upon trying to evaluate f[3,4] I get the message
NIntegrate::ncvb: NIntegrate failed to converge to prescribed accuracy after 9 recursive bisections in q near {q} = {1.00125749138406369739184946806}. NIntegrate obtained 0.030281897883550482023091537839230. and 1.0435410747245518126700650167430.*^-16 for the integral and error estimates. >>
9 being the default value of MaxRecursion.
Does anyone have any ideas why?
I'm also finding that when I try and
Plot[f[3,b],{b,0,1},WorkingPrecision->30]
I'm getting the message
NIntegrate::precw: The precision of the argument function (q BesselJ[0,0.0000204286 q] (-(2/(15 q^4))+(1-q^2)^(3/2) ((2+3 Power[<<2>>])/(15 q^4)-(-1+1/q^2+Power[<<2>>] ArcTanh[<<1>>])/((1+Times[<<2>>])^2 q^2)) HeavisideTheta[1-q^2])) is less than WorkingPrecision (30.`). >>
How do I fix this?
Can you offer guidance or do you also need help?
Draft saved Draft deleted
Similar Discussions: MaxRecursion(/WorkingPrecision?) Error in Mathematica 8
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http://math.stackexchange.com/questions/273129/has-this-example-something-to-do-with-vector-projection
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# Has this example something to do with vector projection?
Has this example something to do with vector projection?
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Can you please add a reference as to where you got this from? Regards – Amzoti Jan 8 '13 at 22:23
It is from this book. books.google.dk/… – Reader Jan 8 '13 at 22:25
Yes. The force $\textbf{F}$ can be given by $(\textbf{a} \bullet \hat{\textbf{b}}) \hat{\textbf{b}}$ where $\hat{\textbf{b}}$ is the unit vector in the direction of b. – Andrew D Jan 8 '13 at 22:26
## 1 Answer
I cannot access the link you provide to better understand the context of the problem.
But I'll venture to answer:
Yes, this example involves a vector projection:
Specifically, let $\bf{F}$ denote force, and $\hat{\bf{b}}$ denote the unit vector in the direction b. Then $$\bf{F} = (\bf{a} \bullet \hat{\bf{b}}) \hat{\bf{b}}.$$
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https://gamedev.stackexchange.com/questions/159657/weird-shader-behavior-on-different-devices
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# Weird shader behavior on different devices
I'm trying to combine an ordinary shader with a Single Distance Field shader (for fonts and scalable icons) into one shader program. The idea is simple - if uv.x is less than 1.0, it is drawn as usual, and if more than 1.0 then SDF is used (using GL_REPEAT uv.x and uv.x + 1.0 look similar)
precision mediump float;
precision mediump int;
uniform sampler2D u_texture;
varying vec4 v_color;
varying vec2 v_texCoords;
uniform float u_smoothing;
void main() {
// SDF
float distance = texture2D(u_texture, v_texCoords).a;
float alpha = smoothstep(0.5 - u_smoothing, 0.5 + u_smoothing, distance);
vec4 sdfColor = vec4(v_color.rgb, alpha * v_color.a);
// Regular
vec4 regularColor = v_color * texture2D(u_texture, v_texCoords);
// Making a choice
gl_FragColor = mix(regularColor, sdfColor, step(1.0, v_texCoords.x));
}
It works and looks fine on desktop and most of popular Android devices but not on Oneplus One, Xiaomi Redmi 4A and Moto G devices. This is how it must look like and how it actually looks on desktops and many other devices (Samsung S8, Xiaomi 3s, Pixel 2 etc.):
And this is how it looks like on Moto G, Oneplus One & some others:
I tried to find a problematic function, but without success. First I tried to use the usual condition instead of mix():
void main() {
// ...
// Making a choice
// gl_FragColor = mix(regularColor, sdfColor, step(1.0, v_texCoords.x));
if (v_texCoords.x < 1.0) {
gl_FragColor = regularColor;
} else {
gl_FragColor = sdfColor;
}
}
Nothing has changed - this shader works well on most devices and is still bad on some others. I decided that the problem lies in the calculation of sdfColor and changed fragment shader code a bit to check:
void main() {
// ...
// Making a choice
gl_FragColor = sdfColor; // Always using SDF
}
But this shader worked equally on all devices, which indicates that sdfColor is calculated correctly. This next screenshot was taken on Moto G:
Then I tried to differentiate the regions of textures with different colors:
void main() {
// ...
// Making a choice
if (v_texCoords.x < 1.0) {
gl_FragColor = regularColor;
gl_FragColor.r = 1.0; // Full red channel for regular texture regions without SDF (UV.x < 1.0)
} else {
gl_FragColor = sdfColor;
gl_FragColor.r = 0.0; // No red channel for SDF
}
}
On Moto G and other devices it looks as expected:
It seems to me that using mix() or conditions implicitly changes something else.
Update 1:
Using different precision qualifier (highp / lowp) or completely removing it didn't help and made no visual changes.
This bug starts to appear on desktop (OpenGL) if I add #version 100. Changing it to #version 110 or higher returns normal rendering.
When #version 100 is used on Android (OpenGL ES 2.0) it renders as if there were no #version qualifier at all (exactly the same as described in my question - on Nexus 5x it looks good, on Moto G it doesn't).
Using #version 300 es on Android (OpenGL ES 3.0, looks like it is supported Moto G 3rd) with respective changes to the code (uniform, varying, texture2D replaced by in, out, texture) doesn't fix the problem (good on Nexus, bad on Moto).
Precision qualifier was not used in both cases. Looks like #version does no effect to this problem on Android but makes it appear on desktop when set to 100 (is it OpenGL 1.0?...)
Update 2:
Writing v_texCoords.x to the separate float and using it in mix() fixes this bug but only for desktop when #version 100 is also used:
#version 100
uniform sampler2D u_texture;
varying vec4 v_color;
varying vec2 v_texCoords;
uniform float u_smoothing;
void main() {
float x = v_texCoords.x; // Writing to the separate float
// SDF
float distance = texture2D(u_texture, v_texCoords).a;
float alpha = smoothstep(0.5 - u_smoothing, 0.5 + u_smoothing, distance);
vec4 sdfColor = vec4(v_color.rgb, alpha * v_color.a);
// Regular
vec4 regularColor = v_color * texture2D(u_texture, v_texCoords);
// Making a choice
gl_FragColor = mix(regularColor, sdfColor, step(1.0, x)); // Using x instead of v_texCoords.x
}
It doesn't fix the problem on Moto G. Also when I move float x = v_texCoords.x; to the line right before gl_FragColor = ... the problem remains on desktop:
void main() {
// SDF
float distance = texture2D(u_texture, v_texCoords).a;
float alpha = smoothstep(0.5 - u_smoothing, 0.5 + u_smoothing, distance);
vec4 sdfColor = vec4(v_color.rgb, alpha * v_color.a);
// Regular
vec4 regularColor = v_color * texture2D(u_texture, v_texCoords);
// Making a choice
float x = v_texCoords.x; // Writing to the separate float, this time it doesn't fix the bug
gl_FragColor = mix(regularColor, sdfColor, step(1.0, x)); // Using x instead of v_texCoords.x
}
• I always calculated sdfColor in the same way. I did not replace it with anything else because it seemed to me that sdfColor is calculated correctly (when I used only sdfColor it worked well) – therainycat Jun 13 '18 at 9:41
• No, replacing mix() with condition doesn't fix the problem, it behaves exactly as with mix() – therainycat Jun 13 '18 at 9:50
• Oops, my bad, I have been misunderstanding the problem, sorry for wasting your time. – gan_ Jun 13 '18 at 9:51
• Do you actually have all those devices how did you manage to test this? Also you might want to try vulkan and see if you get the same issues. The shader wouldn't have to change, but the driver will be consuming SPIR-V instead of the actual shader code text, so its possible that there are driver implementation differences for EGL on those devices that cause this issue, if it worked the same everywhere on vulkan it would hint a problem with the implementation of EGL on those devices, or you are using undefined behavior. – opa Jun 13 '18 at 15:24
• also try using highp instead of mediump, or get rid of the precision qualifiers as recommended for more modern versions of OpenGL ES. Try lowp and see if you see any noticable difference as well and try doing the same for int. Maybe try making the code even simpler for the compiler by always assigning first before using members, its possible the GLSL compiler is bugged on those systems. Also you should probably specify the GLSL version with #version. – opa Jun 13 '18 at 15:34
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http://www.science20.com/crawler_superland/richard_feynmans_functional_integral_3_electromagnetism-95164
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This is the third part of a ten-part post on the foundation of our understanding of high energy physics, which is Richard Feynman's functional integral. The first two parts are Action and Multiple Molecules, and the following parts, which will appear at intervals of about a month, are Action for Fields, Radiation in an Oven, Matrix Multiplication, The Functional Integral, Gauge Invariance, Photons, and Interactions.
I'm hoping this blog will be fun and useful for everyone with an interest in science, so although I'll pop up a few formulae again, I'll still try to keep them friendly by explaining all the pieces, as in the first two parts of the post. Please feel free to ask a question in the Comments, if you think anything in the post is unclear.
The clue that led to the discovery of quantum mechanics, whose principles are summarized in Feynman's functional integral, came from the attempted application to electromagnetic radiation of discoveries about heat and temperature. We looked at those discoveries about heat and temperature in the second part of the post, and today I would like to show you how James Clerk Maxwell, just after the middle of the nineteenth century, was able to identify light as waves of oscillating electric and magnetic fields, and to calculate the speed of light from measurements of:
1. the force between parallel wires carrying electric currents;
2. the heat given off by a long thin wire carrying an electric current; and
3. the time integral of the temporary electric current that flows through a long thin wire, when a voltage is introduced between two parallel metal plates, close to each other but not touching, via that wire.
In addition to his work on the distribution of energy among the molecules in a gas, which we looked at in the second part of the post, Maxwell summarized the existing knowledge about electricity and magnetism into equations now called Maxwell's equations, and after identifying and correcting a logical inconsistency in these equations, he showed that they implied the possible existence of waves of oscillating electric and magnetic fields, whose speed of propagation would be equal within observational errors to the speed of light, which was roughly known from Olaf Romer's observation, made around 1676, of a 16 minute time lag between the motions of Jupiter's moons as seen from Earth on the far side of the Sun from Jupiter, and as seen from Earth on the same side of the Sun as Jupiter, together with the distance from the Earth to the Sun, which was roughly known from simultaneous observations of Mars in 1672 from opposite sides of the Atlantic by Giovanni Domenico Cassini and Jean Richer, and observations of the transit of Venus. The speed of light had also been measured in the laboratory by Hippolyte Fizeau in 1849, and more accurately by Léon Foucault in 1862. Maxwell therefore suggested that light was electromagnetic radiation, and that electromagnetic radiation of wavelengths outside the visible range, which from Thomas Young's experiments with double slits was known to comprise wavelengths between about metres for violet light and metres for red light, would also exist. This was the other part of the clue that led to the discovery of quantum mechanics and Feynman's functional integral.
In his writings around 600 BC, Thales of Miletus described how amber attracts light objects after it is rubbed. The Greek word for amber is elektron, which has been adapted to the English word electron, for the first of the elementary matter particles of the Standard Model to be discovered. Benjamin Franklin and Sir William Watson suggested in 1746 that the two types of static electricity, known as vitreous and resinous, corresponded to a surplus and a deficiency of a single "electrical fluid" present in all matter, whose total amount was conserved. Matter with a surplus of the fluid was referred to as "positively" charged, and matter with a deficiency of the fluid was referred to as "negatively" charged. Objects with the same sign of charge repelled each other, and objects with opposite sign of charge attracted each other. Around 1766, Joseph Priestley suggested that the strength of the force between electrostatic charges is inversely proportional to the square of the distance between them, and this was approximately experimentally verified in 1785 by Charles-Augustin de Coulomb, who also showed that the strength of the force between two charges is proportional to the product of the charges.
Most things in the everyday world have no net electric charge, because the charges of the positively and negatively charged particles they contain cancel out. In particular, a wire carrying an electric current usually has no net electric charge, because the charges of the moving particles that produce the current are cancelled by the opposite charges of particles that can vibrate about their average positions, but have no net movement in any direction.
Jean-Baptiste Biot and Félix Savart discovered in 1820 that a steady electric current in a long straight wire produces a magnetic field in the region around the wire, whose direction is at every point perpendicular to the plane defined by the point and the wire, and whose magnitude is proportional to the current in the wire, and inversely proportional to the distance of the point from the wire. André-Marie Ampère discovered in 1826 that this magnetic field produces a force between two long straight parallel wires carrying electric currents, such that the force is attractive if the currents are in the same direction and repulsive if the currents are in opposite directions, and the strength of the force is proportional to the product of the currents, and inversely proportional to the distance between the wires. Thus the force on either wire is proportional to the product of the current in that wire and the magnetic field produced at the position of that wire by the other wire, and the direction of the force is perpendicular both to the magnetic field and the direction of the current.
Ampère's law is used to define both the unit of electric current, which is called the amp, and the unit of electric charge, which is called the coulomb. The amp is defined to be the electric current which, flowing along each of two very long straight parallel thin wires one metre apart in a vacuum, produces a force of kilogram metres per second between them, per metre of their length. The coulomb is then defined to be the amount of moving electric charge which flows in one second through any cross-section of a wire carrying a current of one amp. Electric currents are often measured in practice by moving-coil ammeters, in which the deflection of the indicator needle is produced by letting the current flow through a movable coil suspended in the field of a permanent magnet, that has been calibrated against the magnetic field produced by a current-carrying wire.
Maxwell interpreted the force on a wire carrying an electric current in the presence of a magnetic field as being due to a force exerted by the magnetic field on the moving electric charge carriers in the wire, and defined the magnetic induction to be such that, in Cartesian coordinates, the force on a particle of electric charge moving with velocity in the magnetic field , is:
Here each index , , or can take values 1, 2, 3, corresponding to the directions in which the three Cartesian coordinates of spatial position increase. I explained the meaning of the symbol in the first part of the post, here. represents the collection of data that gives the value of the magnetic field in each coordinate direction at each position in space and each moment in time, so that if represents a position in space, the value of the magnetic field in coordinate direction , at position , and time , could be represented as or , for example. If represents the collection of data that gives the particle's position at each time , then . represents the collection of data that gives the force on the particle in each coordinate direction at each moment in time.
The symbol is an alternative form of the Greek letter epsilon. The expression is defined to be 1 if the values of , , and are 1, 2, 3 or 2, 3, 1 or 3, 1, 2; if the values of , , and are 2, 1, 3 or 3, 2, 1 or 1, 3, 2; and 0 if two or more of the indexes have the same value. Thus the value of changes by a factor if any pair of its indexes are swapped. A quantity that depends on two or more direction indexes is called a tensor, and a quantity whose value is multiplied by if two of its indexes of the same type are swapped is said to be "antisymmetric" in those indexes. Thus is an example of a totally antisymmetric tensor.
A quantity that depends on position and time is called a field, and a quantity that depends on one direction index is called a vector, so the magnetic induction is an example of a vector field. From the above equation, the unit of the magnetic induction is kilograms per second per coulomb.
Since no position or time dependence is displayed in the above equation, the quantities that depend on time are all understood to be evaluated at the same time, and the equation is understood to be valid for all values of that time. The magnetic field is understood to be evaluated at the position of the particle, and the summations over and are understood to go over all the values of and for which the expressions are defined. Thus if we explicitly displayed all the indexes and the ranges of the summations, the equation could be written:
Maxwell also interpreted the electrostatic force on an electrically charged particle in the presence of another electrically charged particle as being due to a force exerted by an electric field produced by the second particle, and defined the electric field strength to be such that, in the same notation as before, the force on a particle of electric charge in the electric field , is:
Thus the unit of the electric field strength is kilograms metres per second per coulomb, which can also be written as joules per metre per coulomb, since a joule, which is the international unit of energy, is one kilogram metre per second. The electric field strength is another example of a vector field.
Electric voltage is the electrical energy in joules per coulomb of electric charge. Thus if the electrostatic force can be derived from a potential energy by , as in the example for which we derived Newton's second law of motion from de Maupertuis's principle, then the electric field strength is related to by . I have written the potential energy here as instead of , to avoid confusing it with voltage. is the potential voltage, so the electric field strength is minus the gradient of the potential voltage, and the unit of electric field strength can also be expressed as volts per metre.
The voltage produced by a voltage source such as a battery can be measured absolutely by measuring the current that flows and the heat that is produced, when the terminals of the voltage source are connected through an electrical resistance. In all currently known electrical conductors at room temperature, an electric current flowing through the conductor quickly stops flowing due to frictional effects such as scattering of the moving charge carriers by the stationary charges in the material, unless the current is continually driven by a voltage difference between the ends of the conductor, that produces an electric field along the conductor. The work done by a voltage source of volts to move an electric charge of coulombs from one terminal of the voltage source to the other is joules, so if a current of amps coulombs per second is flowing, the work done by the voltage source per second is joules per second watts, since a watt, which is the international unit of power, is one joule per second. Thus the voltage produced by a voltage source can be measured absolutely by connecting the terminals of the voltage source by for example a long thin insulated copper wire that is coiled in a thermally insulated flask of water, and measuring the electric current and the rate at which the water temperature rises, since the specific heat capacity of water is known from measurements by James Joule to be about 4180 joules per kilogram per degree centigrade.
Maxwell summarized Coulomb's law for the electrostatic force between two stationary electric charges by the equation:
Here is a vector field called the electric displacement, whose relation to the electric field strength at a position depends on the material present at . has the same meaning as in the first part of the post, here, with now taken as , and now taken as . is the Greek letter rho, and represents the collection of data that gives the amount of electric charge per unit volume, at each spatial position and time . It is called the electric charge density. For each position and time , it is defined to be the amount of electric charge inside a small volume centred at , divided by , where the ratio is taken in the limit that tends to 0. A field that does not depend on any direction indexes is called a scalar field, so is an example of a scalar field. The units of are coulombs per metre, so the units of are coulombs per metre.
In most materials the electric displacement and the electric field strength are related by:
where is a number called the permittivity of the material. Although the same symbol is used for the permittivity and the antisymmetric tensor , I will always show the indices on , so that it can't be mistaken for the permittivity.
To check that the above equation summarizing Coulomb's law leads to the inverse square law for the electrostatic force between stationary point-like charges as measured by Coulomb, we'll calculate the electric field produced by a small electrically charged sphere. We'll choose the zero of each of the three Cartesian coordinates to be at the centre of the sphere, and represent the radius of the sphere by . The electric charge per unit volume, , might depend on position in the sphere, for example the charge might be concentrated in a thin layer just inside the surface of the sphere. We'll assume that , the value of at position , does not depend on the direction from to the centre of the sphere, although it might depend on the distance from to the centre of the sphere. The electric displacement at position will be directed along the straight line from to the centre of the sphere, so for , where is a quantity that depends on . From Leibniz's rule for the rate of change of a product, which we obtained in the first part of the post, here, we have:
And since only depends on through the dependence of on , we have:
The values of the components of other than are fixed throughout this formula, so their values don't need to be displayed. From this formula and the previous one:
Leibniz's rule for the rate of change of a product also gives us:
and since , it also gives us:
since, for example, , while . Thus
so from the previous formula,
Thus from Maxwell's equation summarizing Coulomb's law, above:
From Leibniz's rule for the rate of change of a product, we have:
where the final equality follows from the result we obtained in the second part of the post, here, with taken as 3 and taken as . Thus after multiplying the previous equation by , it can be written:
So from the result we found in the first part of the post, here, that the integral of the rate of change of a quantity is equal to the net change of that quantity, we find that for any two particular values and of :
The expression is the total electric charge in the region between distances and from the centre of the sphere, divided by the surface area of a sphere of radius 1, which I'll represent by . For the surface area of a sphere of radius is , since if we use angular coordinates such as latitude and longitude to specify position on the surface of the sphere, the distance moved as a result of a change of an angular coordinate is proportional to . Thus the contribution to the integral from the interval from to is aproximately times the total electric charge in the spherical shell between distances and from , since the volume of this shell is approximately , and the errors of these two approximations tend to 0 more rapidly than in proportion to as tends to 0.
Let's now assume that is finite throughout the sphere, and depends smoothly on as tends to 0. Then is finite as tends to 0, so:
Thus for greater than the radius of the charged sphere, we have:
where is the total electric charge of the sphere. Thus if is outside the sphere, then the electric displacement at is given by:
for . Thus the electric field strength in the region outside the sphere is given by:
where is the permittivity of the material in the region outside the sphere. So the force on a particle of electric charge at position outside the sphere is given by:
This is in agreement with Coulomb's law, since is a vector of length 1, that points along the line from the centre of the sphere to . The force is repulsive if and have the same sign, and attractive if they have opposite signs.
We'll calculate the surface area of a sphere of radius 1 by using the result we found in the second part of the post, here, that . We have:
We can also think of , , and as the Cartesian coordinates of a point in 3-dimensional Euclidean space. The distance from the point to the point is then . So from the discussion above, with taken as , the above triple integral is equal to , so we have:
The value of the expression is unaltered if we replace by , so we also have:
So from the result we found in the second part of the post, here:
Thus the force on a particle of electric charge at position outside the sphere is given by:
The permittivity of the vacuum is denoted by . The expression is the number that determines the overall strength of the electrostatic force between two stationary charges, so it plays the same role for the electrostatic force as Newton's constant plays for the gravitational force.
The value of the permittivity, , whose unit is joule metres per coulomb, or equivalently kilogram metre per second per coulomb, can be measured for a particular electrical insulator by placing a sample of the insulator between the plates of a parallel plate capacitor, which consists of two large parallel conducting plates separated by a thin layer of insulator, then connecting a known voltage source across the plates of the capacitor, and measuring the time integral of the resulting current that flows along the wires from the voltage source to the capacitor, until the current stops flowing. The current is the rate of change of the charge on a plate of the capacitor, so since the integral of the rate of change is the net change, as we found in the first part of the post, here, the time integral of the current is the total electric charge that ends up on a plate of the capacitor.
Once the current has stopped flowing, the voltage no longer changes along the wires from the terminals of the voltage source to the plates of the capacitor, so the entire voltage of the voltage source ends up between the plates of the capacitor. If the lengths of the sides of the capacitor plates are much larger than the distance between the plates, and the 1 and 2 coordinate directions are in the plane of the plates, then the electric field strength between the plates is , where is the voltage of the voltage source, and is the distance between the plates.
If the electric charge on a plate of the capacitor is and is uniformly distributed over the capacitor plate, and the area of each capacitor plate is , then by integrating Maxwell's equation across the thickness of a capacitor plate and noting that the electric field is 0 outside the plates, we find:
since the integral of across the thickness of a capacitor plate is equal to the difference of between the inner and outer faces of that capacitor plate, by the result we found in the first part of the post, here, that the integral of the rate of change of a quantity is equal to the net change of that quantity; and the integral of the electric charge per unit volume, , across the thickness of a capacitor plate is equal to the electric charge per unit area, , on the capacitor plate.
Thus since , , , and are all known, the value of for the electrical insulator between the capacitor plates is determined. From measurements of this type with a vacuum between the capacitor plates, the permittivity of a vacuum is found to be such that:
Maxwell summarized Ampère's law for the force between two parallel electric currents, as above, by the equation:
Here is a vector field called the electric current density. For each position , time , and value 1, 2, or 3 of the coordinate index , it is defined to be the net amount of electric charge that passes in the positive direction through a small area perpendicular to the direction in a small time , divided by , where the ratio is taken in the limit that and tend to 0. The units of are amps per metre. is the totally antisymmetric tensor I defined above. is a vector field called the magnetic field strengh, whose relation to the magnetic induction at a position depends on the material present at . The units of are amps per metre. has the same meaning as in the first part of the post, here, with now taken as , and now taken as .
In most non-magnetized materials the magnetic induction and the magnetic field strength are related by:
where , which is the Greek letter mu, is a number called the permeability of the material. Its unit is kilogram metres per coulomb. The permeability of the vacuum is denoted by . Its value is fixed by the definition of the amp, as above.
To check that the above equation summarizing Ampère's law leads to a force between two long straight parallel wires carrying electric currents, whose strength is inversely proportional to the distance between the wires as measured by Ampère, and to calculate the value of implied by the definition of the amp, as above, we'll calculate the magnetic field produced by an infinitely long straight wire that is carrying an electric current. We'll choose the wire to be along the 3 direction, and the zero of the 1 and 2 Cartesian coordinates to be at the centre of the wire, and represent the radius of the wire by . We'll assume that , the electric current density in the direction along the wire at position , does not depend on or the direction from to the centre of the wire, although it might depend on the distance from to the centre of the wire.
From its definition above, the antisymmetric tensor is 0 if any two of its indexes are equal, so in particular, is 0 for all values of the index . Thus Maxwell's equation summarizing Ampère's law, as above, does not relate to , so we'll assume is 0.
Now let's suppose that the magnetic field strength at position is directed along the straight line perpendicular to the wire from to the centre of the wire, so for , where is a quantity that depends on . Then in the same way as above, we find:
and also in the same way as above, we find:
so:
From Leibniz's rule for the rate of change of a product, which we obtained in the first part of the post, here, we have:
Thus:
so Maxwell's equation summarizing Ampère's law, as above, does not relate to this form of , so we'll also assume that this form of is 0.
The final possibility is that the magnetic field strength at position is perpendicular to the plane defined by and the wire carrying the current. Then , and from the diagram in the first part of the post, here, interpreted as the two-dimensional plane through and perpendicular to the wire, if and , then the direction of is along , so , , where is a quantity that depends on . Then from Leibniz's rule for the rate of change of a product, which we obtained in the first part of the post, here, and the formula above for , we have:
Thus from Maxwell's equation summarizing Ampère's law, as above:
From Leibniz's rule for the rate of change of a product, we have:
where the final equality follows from the result we obtained in the second part of the post, here, with taken as 2 and taken as . Thus after multiplying the previous equation by , it can be written:
So from the result we found in the first part of the post, here, that the integral of the rate of change of a quantity is equal to the net change of that quantity, we find that for any two particular values and of :
The expression is times the total electric charge per unit time passing through the region between distances and from the centre of the wire, in any cross-section of the wire. For the circumference of a circle of radius is , so the contribution to the integral from the interval from to is aproximately times the total electric charge per unit time passing through the region between distances and from the centre of the wire, in any cross-section of the wire, since the area of this shell is approximately , and the errors of these two approximations tend to 0 more rapidly than in proportion to as tends to 0.
Let's now assume that is finite throughout the cross-section of the wire, and depends smoothly on as tends to 0. Then is finite as tends to 0, so:
Thus for greater than the radius of the wire, we have:
where is the total electric current carried by the wire. Thus if is outside the wire, then the magnetic field strength at is given by:
Thus the magnetic induction in the region outside the wire is given by:
where is the permeability of the material in the region outside the wire. This is perpendicular to the plane defined by the point and the wire, and its magnitude is proportional to the current in the wire, and inversely proportional to the distance of the point from the wire, in agreement with the measurements of Biot and Savart as above, since is a vector of length 1.
Let's now suppose there is a second infinitely long straight wire parallel to the first, such that the 1 and 2 Cartesian coordinates of the centre of the second wire are , and the total electric current carried by the second wire is . From Maxwell's equation above, and the definition of the antisymmetric tensor as above, the force on a particle of electric charge moving with velocity along the second wire, in the presence of the magnetic field produced by the first wire, as above, is given by:
The interaction between this moving charge and the other particles in the second wire prevents this moving charge from accelerating sideways out of the second wire, so the above force is a contribution to the force on the second wire, that results from the magnetic field produced by the current in the first wire. If there are particles of electric charge and velocity per unit length of the second wire, then their contribution to the force per unit length on the second wire is:
The average number of these particles that pass through any cross-section of the second wire per unit time is , so their contribution to the electric current carried by the second wire is . Thus the contribution of these particles to the force per unit length on the second wire is times their contribution to the electric current carried by the second wire. So by adding up the contributions from charged particles of all relevant values of and , we find that the total force per unit length on the second wire that results from the current carried by the first wire and the current carried by the second wire is given by:
The direction of this force is towards the first wire if and have the same sign and away from the first wire if and have opposite sign, and the strength of this force is proportional to the product of the currents, and inversely proportional to the distance between the wires, so this force is in agreement with Ampère's law, as above. And from the definition of the amp, as above, we find that the permeability of a vacuum is by definition given by:
Maxwell noticed that his equation summarizing Ampère's law, as above, leads to a contradiction. For by applying to both sides of that equation, and summing over , we obtain:
For a quantity that depends smoothly on a number of quantities that can vary continuously, where represents the collection of those quantities, and indexes such as or distinguish the quantities in the collection, we have:
The expression in the third line here is equal to the expression we obtain from it by swapping the indexes and , so we have:
So if the magnetic field strength depends smoothly on position, we also have:
The value of the right-hand side of this formula does not depend on the particular letters , , and used for the indexes that are summed over. Thus if the letter , used as an index, is also understood to have the possible values 1, 2, or 3, we have:
At each of the first three steps in the above formula, one of the indexes summed over in the previous version of the expression is rewritten as a different letter that is understood to take the same possible values, 1, 2, or 3, and which does not otherwise occur in the expression. At the first step, the index is rewritten as , then at the second step, the index is rewritten as , and at the third step, the index is rewritten as . An index that occurs in an expression, but is summed over the range of its possible values, so that the full expression, including the , does not depend on the value of that index, is called a "dummy index".
The fourth step in the above formula used the definition of the antisymmetric tensor , as above, which implies that its value is multiplied by if two of its indexes are swapped, so that . The fifth step used the original formula for , as above, together with the fact that the order of the indexes under the in the right-hand side doesn't matter, since each of the indexes is simply summed over the values 1, 2, and 3.
Thus from the second formula for , as above, we have:
Hence:
Let's now consider the rate of change with time of the total electric charge in a tiny box-shaped region centred at a position , such that the edges of the box are aligned with the coordinate directions, and have lengths , , and . From the definition above of the electric current density , the net amount of electric charge that flows into the box through the face of the box perpendicular to the 1 direction and centred at , during a small time , is approximately , and the net amount of electric charge that flows out of the box through the face of the box perpendicular to the 1 direction and centred at , during the same small time , is approximately , and the errors of these approximations tend to 0 more rapidly than in proportion to , as , , and tend to 0. And from the result we obtained in the first part of the post, here, with taken as and taken as , we have:
where the error of the above approximations tends to 0 more rapidly than in proportion to , as tends to 0. Thus the net amount of electric charge that flows into the box through the faces of the box perpendicular to the 1 direction, during a small time , is approximately:
where the error of this approximation tends to 0 more rapidly than in proportion to , as , , , and tend to 0. So from the corresponding results for the net amount of electric charge that flows into the box through the faces of the box perpendicular to the 2 and 3 directions, during the same small time , we find that the net amount of electric charge that flows into the box through all the faces of the box, during the small time , is approximately:
where the error of this approximation tends to 0 more rapidly than in proportion to , as , , , and tend to 0.
There's no evidence that electric charge can vanish into nothing or appear from nothing, so the net amount of electric charge that flows into the box through all the faces of the box, during the small time , must be equal to the net increase of the total electric charge in the box, during the small time , which from the definition of the electric charge density , as above, is approximately:
where the error of this approximation tends to 0 more rapidly than in proportion to , as , , , and tend to 0. Thus we must have:
But we found above that Maxwell's equation summarizing Ampère's law, as above, leads instead to . This equation is false whenever there is a build-up of electric charge in a region, as, for example, on the plates of a parallel plate capacitor, in the method of measuring the permittivity of an electrical insulator, that I described above. Maxwell realized that the resolution of this paradox is that there must be an additional term in the left-hand side of his equation summarizing Ampère's law, where is the electric displacement vector field, so that the corrected form of his equation summarizing Ampère's law is:
This equation still correctly reproduces Ampère's law and the magnetic field produced by an electric current flowing in a long straight wire as measured by Biot and Savart, as I described above, because the experiments of Ampère and Biot and Savart were carried out in steady state conditions, where nothing changed with time, so the new term in the left-hand side gave 0. However if we apply to both sides of this corrected equation, and sum over , which is what led to the paradox for the original equation, we now find:
So if the electric displacement depends smoothly on position, so that , by the result we found above, we find:
Combining this with Maxwell's equations summarizing Coulomb's law, as above, it gives:
which is now in agreement with the formula expressing the conservation of electric charge, as above.
Michael Faraday discovered in 1831 that if an electrically insulated wire is arranged so that somewhere along its length it forms a loop, and the magnetic induction field inside the loop and perpendicular to the plane of the loop is changed, for example by switching on a current in a separate coil of wire in a suitable position near the loop, then a voltage is temporarily generated along the wire while the magnetic induction field is changing, such that if the directions of the 1 and 2 Cartesian coordinates are in the plane of the loop, and the value of in the region enclosed by the loop in the plane of the loop depends on time but not on position within that region, then:
where is the area enclosed by the loop, and the sign depends on the direction along the wire in which the voltage is measured. The sign of the voltage is such that if a current flows along the wire in consequence of the voltage, then the magnetic field produced by that current, as above, is such that in the region enclosed by the loop in the plane of the loop has the opposite sign to .
Maxwell assumed that the electric field strength that corresponds to the voltage is produced by the changing magnetic induction field even when there is no wire present to detect in a convenient way. To discover the consequences of this assumption, it is helpful to know about the relation between the electric field strength and the rate of change of voltage with distance in a particular direction.
For any vector , and any vector of length 1, the expression is called the component of in the direction . To relate this to the magnitude of , which is by Pythagoras, and the angle between the directions of and , we observe that is a vector of length 1, and if we consider and as representing the Cartesian coordinates of two points in the 3-dimensional generalization of Euclidean geometry, as in the first part of this post, here, then by Pythagoras, the distance between those points is:
If does not point either in the same direction as or the opposite direction to , so that is not equal to , then the directions of and define a 2-dimensional plane, and we can choose Cartesian coordinates in that 2-dimensional plane as in the first part of the post, here, such that the coordinates of are , and the coordinates of are . So by Pythagoras, the distance between the points they define is:
This is equal to the previous expression, so we have:
This formula is also true when , so . If is along the coordinate direction, this formula shows that , where is the angle between the direction of and the coordinate direction. Thus for any vector of length 1, is equal to the value that the coordinate of in the direction would have, if was one of the coordinate directions of Cartesian coordinates.
If the electric field strength can be derived from a voltage field , so that as above, then at each point along the electrically insulated wire, we have:
where is the distance along the wire from that point to a fixed end of the wire, and is a vector of length 1 whose direction is along the wire in the direction of increasing . The first equality here is the component of the equation in the direction along the wire. The component of in any direction is the rate of change of with distance in that direction, so the component of in the direction along the wire is the rate of change of with distance along the wire, which is the second equality.
The movable electrically charged particles in the wire are channelled by the electrical insulation of the wire so that their net motion can only be along the wire, and only the component of the electric field strength along the wire can affect their net motion. Their motion along the wire due to the force is determined by a voltage defined along the wire such that
as in the previous formula, even if the voltage defined along the wire does not correspond to a voltage field in the region outside the wire.
Let's consider Faraday's result, as above, for a very small rectangular loop centred at , such that the edges of the loop are in the 1 and 2 Cartesian coordinate directions and have lengths and . We'll assume that the wire arrives at and leaves the rectangle at the corner at , and that the two lengths of wire that run from this corner of the rectangle to the measuring equipment, such as a voltmeter, follow exactly the same path. Then if the voltage along the wire is related to an electric field strength as in the above formula, the net voltage difference between the ends of the wire, as measured by Faraday, must be produced by the electric field strength along the sides of the rectangle, because any voltages produced along the lengths of wire that run from the corner of the rectangle to the measuring equipment will be equal and opposite along the two lengths of wire, and thus cancel out of the net voltage.
We'll choose to be the distance along the wire from the end of the wire such that increases along the side of the rectangle from the corner at to the corner at , then along the side from this corner to the corner at , then along the side from this corner to the corner at , and finally along the side from this corner to the first corner at . The components of the vector of length 1, that points along the four sides of the rectangle in the direction of increasing , are therefore , , , and , for the four sides of the rectangle taken in this order.
The net change of the voltage around the rectangle in the direction of increasing is equal to the sum of the net change of the voltage along the four sides of the rectangle in the direction of increasing , so from the formula above, and the result we found in the first part of the post, here, that the integral of the rate of change of a quantity is equal to the net change of that quantity, is equal to the sum of the integrals along the four sides of the rectangle.
For near in the plane of the rectangle, the result we obtained in the first part of the post, here, with taken as and taken as , gives:
where as the magnitudes of and tend to 0, the error of this approximate representation tends to 0 more rapidly than in proportion to those magnitudes.
The coordinates of a point a distance along the first side of the rectangle from the first corner of this side are . And along this side, is equal to plus a constant value, the length of the wire from its first end to the first corner of this side, so . Thus since for this side, we have:
where the error of this approximation tends to 0 more rapidly than in proportion to or as and tend to 0, and I used the result we found in the first part of the post, here, that the integral of the rate of change of a quantity is equal to the net change of that quantity, and also and , from the result we found in the second part of the post, here.
The coordinates of a point a distance along the third side of the rectangle from the first corner of that side are . We again have , so since for that side, we have:
to the same accuracy as before. Thus:
where the error of this approximation tends to 0 more rapidly than in proportion to , as and tend to 0 with their ratio fixed to a finite non-zero value.
Similarly we find:
to the same accuracy. So:
to the same accuracy. Thus:
where the error of this approximation tends to 0 more rapidly than in proportion to , as and tend to 0 with their ratio fixed to a finite non-zero value.
Thus from Faraday's measurements, as above:
since is the area of the small rectangle. We have obtained this equation at the position of the centre of the small rectangle, so it holds everywhere the small rectangle of wire could have been placed.
To determine the sign, let's suppose that and are 0 at the centre of the small rectangle, and that is positive along the 1st side of the rectangle and negative along the 3rd side, and is positive along the 2nd side of the rectangle and negative along the 4th side. Then is negative and is positive, so is negative, and the force on a movable charged particle of positive is in the direction of increasing along all four sides of the rectangle, so the current along the wire is positive in the direction of increasing .
From the result we found above, Maxwell's equation summarizing Ampère's law, as above, implies that a positive current along a wire in the 3 direction produces a magnetic induction field such that is negative for greater than the coordinate of the wire and positive otherwise, and is positive for greater than the coordinate of the wire and negative otherwise.
The antisymmetric tensor , which I defined above, is unaltered by a cyclic permutation of its indexes, for example or , so Maxwell's equation summarizing Ampère's law, as above, also implies that a positive current along a wire in the 1 direction produces a magnetic induction field such that is positive for greater than the coordinate of the wire and negative otherwise, and a positive current along a wire in the 2 direction produces a magnetic induction field such that is negative for greater than the coordinate of the wire and positive otherwise.
Thus if the current along the wire is positive in the direction of increasing , the magnetic induction field produced by the current along each side of the small rectangle is such that is positive inside the small rectangle. So from the observed sign of the voltage, as I described above, a positive value of inside the small rectangle produces electric field strengths that result in a current along the wire that is negative in the direction of increasing , and thus of opposite sign to those I assumed above. Thus positive produces positive , so the formula with the correct sign is:
The corresponding formulae that result from considering small rectangles whose edges are in the 2 and 3 or 3 and 1 Cartesian coordinate directions are obtained from this formula by cyclic permutation of the indexes, and the three formulae can be written as:
where is the totally antisymmetric tensor I defined above. This is Maxwell's equation summarizing Faraday's measurements involving time-dependent magnetic fields, as above.
From the discussion above, if the electric field strength can be derived from a voltage field , then . The electric field strength produced by the changing magnetic induction field in accordance with the above equation cannot be derived from a voltage field , for if , and depends smoothly on position, then by a similar calculation to the one above, we have:
No magnetically charged particles, often referred to as magnetic monopoles, have yet been observed, and Maxwell's equation summarizing this fact, analogous to his equation summarizing Coulomb's law, as above, is:
Although it's not possible to derive the electric field strength from a voltage field alone if the magnetic induction field is time-dependent, Maxwell's equation summarizing Faraday's measurements involving time-dependent magnetic fields, as above, and his equation above summarizing the non-observation of magnetic monopoles, can always be solved by deriving the electric field strength and the magnetic induction field from a voltage field and a vector field called the vector potential, such that:
For if has this form, then the left-hand side of Maxwell's equation summarizing Faraday's measurements involving time-dependent magnetic fields, as above, is:
where I assumed that the vector potential depends smoothly on position and time, and used the result we found above. And if has the above form, then the right-hand side of that equation is:
where I again used the result we found above. This is equal to the left-hand side as above, so if and are derived from a voltage field and a vector potential field as above, then Maxwell's equation summarizing Faraday's measurements involving time-dependent magnetic fields, as above, is solved.
And if the magnetic induction field is derived from a vector potential field as above, then the left-hand side of Maxwell's equation above summarizing the non-observation of magnetic monopoles is:
by a similar calculation to the one above. Thus Maxwell's equation summarizing the non-observation of magnetic monopoles is also solved.
If the electric field strength and the magnetic induction field are derived from a voltage field and a vector potential field , as above, then in a vacuum, where the electric displacement field is related to the electric field strength by , and the magnetic field strength is related to the magnetic induction field by , Maxwell's equation summarizing Coulomb's law, as above, becomes:
And Maxwell's corrected equation summarizing Ampère's law, as above, becomes:
where each index from the start of the lower-case English alphabet can take values 1, 2, 3, corresponding to the directions in which the three Cartesian coordinates of spatial position increase.
To simplify the above formula, we'll consider the expression:
where is the Kronecker delta, that I defined in the first part of the post, here, so its value is 1 when , and 0 otherwise. Thus , and . A quantity whose value is unchanged if two of its indexes of the same type are swapped is said to be "symmetric" in those indexes, so from the definition of a tensor, as above, is an example of a symmetric tensor.
In the above definition of the tensor , each term in the right-hand side after the first term is obtained from the first term by leaving the indexes , , and in the same positions as in the first term, and swapping the indexes , , and among themselves. Among the 6 terms in the right-hand side, each of the possible sequences of the letters occurs exactly once, where for each non-negative whole number , I defined in the second part of the post here, and we observed in the second part of the post, here, that the number of different ways of putting distinguishable objects in distinguishable places, such that exactly one object goes to each place, is Thus the number of different sequences of different letters is .
A re-ordering of a sequence of different letters is called a permutation of the sequence. The sign of each term in the right-hand side of the above definition of is a sign associated with the permutation that changes the sequence into the sequence in which the letters occur in that term, and is defined in the following way. For any permutation of a sequence of different letters, a cycle of the permutation is a sequence of the letters such that the final position of each letter of the cycle is the same as the initial position of the next letter of the cycle, except that the final position of the last letter of the cycle is the same as the initial position of the first letter of the cycle. For example, for the permutation , the letter by itself is a cycle, and is a cycle. Two cycles are considered to be equivalent if they have the same letters, and the number of letters in a cycle is called its length. The sign associated with a permutation, which is called the sign of the permutation, is the sign of , where is the number of inequivalent cycles of even length. For example the second term in the right-hand side of the above definition of corresponds to the permutation , which has just one cycle whose length is 3, so its sign is .
If a permutation is followed by another permutation that just swaps two letters, then the cycles of the resulting permutation are the same as the cycles of the original permutation, except that if the two swapped letters were originally in the same cycle, that cycle is divided into two cycles, each of which contains one of the swapped letters, while if the two swapped letters were originally in two different cycles, those two cycles are combined into a single cycle. If the two swapped letters were originally in a cycle of even length, then when that cycle is divided into two cycles, the number of cycles of even length either increases by 1 or decreases by 1, so is multiplied by . If the two swapped letters were originally in a cycle of odd length, then when that cycle is divided into two cycles, one of the resulting cycles has even length and the other has odd length, so the number of cycles of even length increases by 1, so is again multiplied by . And if the two swapped letters were originally in two different cycles then the reverse of one of the preceding cases occurs, so is again multiplied by . Thus swapping any two letters reverses the sign of a permutation.
Thus if any two of the last three indexes of are swapped, the value of is multiplied by , so in accordance with the definition above, is antisymmetric in its last three indexes. Thus the value of must be 0 when any two of its last three indexes have the same value, for example must be 0, since swapping the 4th and 5th indexes of multiplies its value by . The only possible values of each index are 1, 2, or 3, so is 0 unless is one of the possibilities , , , , , or , and furthermore,
From the definition of the antisymmetric tensor , as above, this implies that:
since this equation is true for because , and it is therefore also true for all the other values of for which is non-zero, by the preceding equation and the definition of , as above, and it is also true whenever two of the indexes have the same value, since both sides of the equation are then 0.
We can also write the definition above of as:
which is the same as the formula above, except that I have changed the order of the factors in each term after the first, so that the indexes now occur in the same order in every term, while the order of the indexes is now different in each term. Each term now corresponds to one of the 6 permutations of the letters , and the sign of each term is the sign of the corresponding permutation of the letters . So in the same way as above, we find that is also antisymmetric in its first three indexes, and that:
From this and the formula above, we find:
This is true for all cases where the indexes take values 1, 2, or 3, and from the case where , we find:
Thus:
Furthermore, , since for these values of the indexes, only the first term in the right-hand side of the above definition of is non-zero, and its value is 1. Thus , so:
We now observe that:
and
since the indexes and can take values 1, 2, or 3, and from the definition of the Kronecker delta in the first part of the post, here, the product is non-zero for exactly one value of if , namely for , in which case , while if , where the symbol means, "is not equal to," then and are not both non-zero for any value of .
Thus:
Thus Maxwell's corrected equation summarizing Ampère's law, as above, expressed in terms of the voltage field and the vector potential field , as above, is:
We now observe that for any vector :
since is non-zero for exactly one value of , namely for , in which case it is 1.
Using this property of the Kronecker delta, we find:
Thus Maxwell's corrected equation summarizing Ampère's law, as above, expressed in terms of the voltage field and the vector potential field , as above, is:
We now observe that the formulae for the electric field strength and the magnetic induction field in terms of the voltage field and the vector potential field , as above, are unaltered if and are modified by the following replacements:
where is an arbitrary scalar field that depends smoothly on position and time. For the modified electric field strength and magnetic induction field are:
where I used the result we found above, and a similar calculation to the one above.
The replacement of the voltage field and the vector potential field by modified fields and , as above, which leaves the electric field strength and the magnetic induction field unaltered, and thus has no experimentally observable consequences, is called a gauge transformation.
We can simplify Maxwell's equation summarizing Coulomb's law, and his corrected equation summarizing Ampère's law, expressed in terms of the voltage field and the vector potential field , as above, and above, by doing a gauge transformation with a scalar field that satisfies:
We then find that:
Let's now assume that we've done a gauge transformation as above, so that:
This is called a gauge condition.
Then by the result we found above, the term in the left-hand side of Maxwell's equation summarizing Coulomb's law, expressed in terms of the voltage field and the vector potential field , as above, is equal to , so that equation becomes:
And Maxwell's corrected equation summarizing Ampère's law, expressed in terms of the voltage field and the vector potential field , as above, becomes:
Let's now consider a region where there are no electrically charged particles and no electric currents, so that and are 0. Then for any vector , and any angle , and any vector perpendicular to , which from the discussion above, means that , a solution of the above equations that satisfies the gauge condition above, which we used to simplify the equations, is given by:
For we found in the first part of the post, here, that and . So by a calculation similar to the one in the second part of the post, here, if and are any quantities independent of , then and . From these results with taken as and , we find:
From the second of these results, we find that is proportional to , so the gauge condition above is satisfied, and since by Pythagoras, the third and fourth of these results show that Maxwell's equation summarizing Ampère's law, as above, is satisfied. Maxwell's equation summarizing Coulomb's law, as above, is automatically satisfied, since for this solution.
From the formulae for the electric field strength and the magnetic induction field in terms of the voltage field and the vector potential field , as above, we find that for this solution:
Thus since we assumed that , we find that , which from the discussion above means that the vector is perpendicular to the vector . And from calculations similar to the one above we find that , so that , so the vector is perpendicular to the vector , and , so , so the electric field strength is perpendicular to the magnetic induction field .
This solution describes oscillating electric and magnetic fields moving in the direction at a speed . From above, the permittivity of a vacuum, measured from the electric charge stored on a paralle plate capacitor, is such that:
and from above, the definition of one amp one coulomb per second, in terms of the force between long parallel wires carrying steady electric currents, as above, implies that the permeability of a vacuum is by definition given by:
Thus:
which is the measured value of the speed of light. Maxwell therefore proposed that light is waves of oscillating electric and magnetic fields perpendicular to the direction of motion of the wave and to each other. The vector is called the wave vector, and the wave solutions above are called transverse waves, because the vector potential is perpendicular to the wave vector .
From calculations similar to those above, we find that the gauge condition above, and the field equations above, have another wave solution:
which is called a longitudinal wave, because the vector potential is parallel to the wave vector . However from the formulae for the electric field strength and the magnetic induction field in terms of the voltage field and the vector potential field , as above, we find that for this solution:
Thus the above longitudinal wave solution has no experimentally observable effects. It is called a pure gauge mode.
Maxwell suggested that there could also be transverse waves of electric and magnetic fields with frequencies outside the visible spectrum, and this was partly confirmed in 1879 by experiments by David Edward Hughes, and conclusively confirmed in 1886 when Heinrich Hertz generated and detected pulses of radio-frequency electromagnetic waves in his laboratory. This led to the utilization of radio-frequency electromagnetic waves for practical communications by Guglielmo Marconi, from around 1895.
Electromagnetic waves will also be emitted by hot objects, and will be present in a hot region that is in thermal equilibrium. It was the study of the electromagnetic waves in hot ovens, at the end of the nineteenth century, that provided the other part of the clue that led to the discovery of quantum mechanics and Richard Feynman's functional integral. In the next part of this post, Action for Fields, we'll look at how Maxwell's equations for the for the electric field strength and the magnetic induction field , expressed in terms of the voltage field and the vector potential field , as above, can be obtained from de Maupertuis's principle of stationary action, for a suitable action that depends on the electromagnetic fields and , and on the positions and motions of any electrically charged particles present, and in the part after that, Radiation in an Oven, we'll look at how the discoveries about heat and temperature that we looked at in the second part of this post, combined with the discoveries about electromagnetic radiation that we've looked at today, lead to a seriously wrong conclusion about the properties of electromagnetic radiation in a hot oven. In the subsequent parts of the post, we'll look at how that problem has been resolved by the discovery of quantum mechanics and Feynman's functional integral, which started with the identification of a new fundamental constant of nature by Max Planck, in 1899.
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https://link.springer.com/article/10.1007%2Fs10514-018-9725-6
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Autonomous Robots
, Volume 43, Issue 1, pp 239–257
# Robot learning of industrial assembly task via human demonstrations
• Maria Kyrarini
• Danijela Ristić-Durrant
• Axel Gräser
Open Access
Article
## Keywords
Robot learning Human–robot collaboration Modified GMM algorithm Industrial assembly task Adaptation to environmental changes
## 1 Introduction
There is a growing interest for human–robot collaboration in manufacturing (Nikolaidis and Shah 2013; Pedersen et al. 2016; ABB 2014; KUKA Robotic 2017). Whereas in the past it was all about replacing the work of humans with that of robots, today the focus is much more on the robot as an assistant or collaborator. The work presented in this paper contributes to the research and development in the human–robot collaboration in industrial applications, by proposing a framework for the manufacturing assembly scenarios with the following goals:
• robot learns the sequence of actions (high-level learning) needed to perform an assembly task from the human collaborators without pre-programming, which includes the object moving and grasping/releasing actions (low-level learning of trajectories),
• robot adapts the learned paths to environmental changes, which are introduced by the human collaborators, without additional training and
• robot performs the learned sequence of actions in different order of occurrence after suggestion from the human collaborator. If the human collaborator is satisfied with the new sequence of actions, the robot learns it.
Traditionally, the industrial robot manipulators are widely used in production lines as they are precise and swift. However, traditional industrial manipulators are pre-programmed by human programmers to perform a specific task in a well-structured and constant environment. In the case of environmental changes, the human programmer would have to take into account all the possible events in advance, and would need to code the actions of the robot as response to all these different events. This process would involve thorough testing of each different case. However, if new circumstances, which were not considered beforehand, appear, the entire pre-programming process would be repeated for which the robot would have to stay out of service until it is re-programmed. In order to make industrial robot programming easier, several technologies have been used in past years. One of them is a framework that enables human collaborators to simply demonstrate the task to the robot as opposite to time consuming and high technical skills demanding traditional robot programming methods (Zhang et al. 2016).
Additionally, regardless of their high precision, accuracy and speed, nowadays industrial robots are not able to perform every task autonomously. Human workers are still needed in assembly and manufacturing production lines, as they have cognition that enables them to respond and adapt quickly to uncertain environments and unpredicted events in a way that is still not possible for robots. Therefore, currently, research is focused on human–robot interaction in industry and on the human–robot synergetic work to perform a given task (Tellaeche et al. 2015).
However, humans sharing the same workspace and manipulating the same objects with robots may introduce uncertainty in the robot’s working environment. Let’s take as an example a human and robot collaboration in an assembly of an object consisting of several parts. Firstly, in the training phase, the human demonstrates to the robot the actions that have to be performed in order to complete the task. Actions could be the following: pick object-part 2, move and place it on top of the object-part 1, and then pick object-part 3, move and place it on top of the object-part 2. In the working phase, the robot–human team is jointly assembling the objects. Firstly, the human co-worker places the object’s parts on the working table and the robot performs the actions of manipulating the object’s parts, learned during the training phase, so to position them on top of each other. Since the human collaborator is not as precise as the robot, he/she cannot place the object’s parts in every repetition of the assembly task exactly at the object’s parts positions and orientations demonstrated during the training phase. Furthermore, the robot may cooperate with different human collaborators during a working day, which may introduce uncertainties for the robot’s performance as each human collaborator could position and orientate the object’s parts differently. Moreover, by mistake, human collaborators may place some objects, such as working tools, on the working table beside the parts of the objects to be assembled introducing so obstacles in robot’s working environments. This may cause collision, bad handling or other damages to the robot. In order to perform the task successfully and without interruptions in spite of the obstacles in the workspace, the robot needs to adapt to environmental changes and to avoid the obstacles without any additional training, alike the way a human collaborator would react to an obstacle appearance. In this paper, a novel framework that can enable robot to adapt the learned task to environmental changes without the need of additional training is suggested.
The proposed framework is based on an approach that enables the robot to learn object manipulation tasks involving as many objects as the industrial assembly task requires. This learning can be achieved by multiple human demonstrations (demos), which introduces both the autonomous adaptation of the learned actions to the different objects’ poses and the obstacle avoidance as requirements. In the presented framework, robot learns the sequence of actions for the demonstrated task, which are adapted in real-time to environmental changes if they appear. Additionally, the human collaborator is able to change the sequence of actions to perform the assembly task in an alternative way, and to provide feedback to the robot on its performance, so the robot learns the sequence with positive feedback.
This paper is organized as follows. The related work is presented in Sect. 2. The overview of the proposed novel robot learning framework is given in Sect. 3. The off-line learning of sequence of actions is presented in Sect. 4, while the online working phase for the adaptation to environmental changes and obstacle avoidance in described in Sect. 5. The results of the experiments with the real robot are shown in Sect. 6 and the conclusion and future work are discussed in Sect. 7.
## 2 Related work
Robot learning from demo is a method in which the human “teacher (demonstrator)” shows (demonstrates) his/her performance to the robot learner and the robot tries to imitate the demonstrated performance. Each process of robot learning from demo is composed of three fundamental steps: observation, representation and reproduction (Dindo and Schillaci 2010).
There are different methods to gather the datasets (observation of the demo) as summarized in Argall et al. (2009). These methods are: tele-operation with joystick or different other interfaces (Forbes et al. 2015; Pathirage et al. 2013), kinesthetic teaching (Kormushev et al. 2010; Kober and Peters 2009), wearable sensors placed on the teacher’ body (Krug and Dimitrovz 2013; Leitner et al. 2014), and vision-based external sensors (Quintero et al. 2014; Zhang et al. 2016).
Given a dataset of the skills or task executions that have been acquired using one or combination of the methods mentioned above, the robot learner must be able to learn a skill or a task from the dataset. In some studies, instead of using one dataset, datasets of multiple demos (Calinon et al. 2010b), (Ekvall and Kragic 2006) are used. In the work presented in this paper, a combination of multiple datasets from demos via kinesthetic teaching with vision-based external sensor is used.
There are different approaches to represent (abstract) and to learn the skill or the task from the datasets of demos. These approaches are grouped by Calinon et al. (2010b) and Billard et al. (2007) into two categories: Skill learning at trajectory level (low-level learning) and Symbolic task learning (high-level learning). One of the goals of the work presented in this paper has been to create a bridge between those two categories by combining high-level and low-level learning.
### 2.1 Skill learning at the trajectory level (low-level learning)
The main goal of this learning approach is to enable robot to learn the basic movements or gestures (motor skills). However, the approach does not allow reproducing of more complicated high-level tasks.
One popular method from this category is Dynamic Movement Primitives (DMP) (Schaal et al. 2005; Pastor et al. 2009), which allows robot to learn a non-linear differential equation based on the movement observed by one demo. In order to achieve generalization, in the modified DMP method (Park et al. 2008), the learned differential equation can be adapted for different start and goal desired positions of the movement or for the obstacle avoidance. Moreover, since the DMP algorithm works with one demo only, it was combined with Gaussian Mixture Model (GMM) to learn from multiple demos (Yin and Chen 2014). DMP can also be combined with Reinforcement learning to initialize the set of primitives for the demonstrated skill in order to improve and adapt the encoded skill by learning optimal policy parameters (Kormushev et al. 2010; Kober and Peters 2009). Another approach to model the robot motion with dynamic systems is Stable Estimator of Dynamic Systems (SEDS) (Khansari-Zadeh and Billard 2011). SEDS method is able to model the robot skill from multiple demos with different starting positions and same target position.
Hidden Markov model (HMM) based approaches have been also used for learning at trajectory level. In Calinon et al. (2011), the time and space constrains are learned by the HMM based framework. Additionally, a comparison between HMM with time dependent Gaussian Mixture Regression (GMR) and DMP is presented in the work by Calinon et al. (2010a), where it was shown how each framework can learn a trajectory based on multiple demos. Few demos are firstly taken having the same initial points but different goal point and after that few demos with the same goal point and different initial points are considered. The shown reproduction satisfied the constraints of the demonstrated task.
Another approach for the skill learning at the trajectory level is the estimation of a distribution, which is determined by Gaussian Mixture Models (GMM) (Calinon et al. 2007; Sabbaghi et al. 2014), where Gaussian Mixture Regression (GMR) is used to generalize the trajectories. GMM can also be combined with virtual spring-damper system (DS-GMR) (Calinon et al. 2014) or with linear attractor system combined with GMR (Mühlig et al. 2012) so to enable the robot to perform the learned skill with new start and target positions. Moreover, GMM/GMR is combined with DMP for generalizing the learned trajectory to new goal point and obstacle avoidance (Ghalamzan et al. 2015).
Furthermore, an algorithm based on discrete Laplace–Beltrami operator (Nierhoff et al. 2016) enables online adaptation of a learned trajectory to dynamic environmental changes while keeping the shape of the trajectory similar to the shape of the original trajectory.
In the approach presented in this paper, GMM is used for the low-level trajectory learning because it is a method which enables automatic extraction of trajectory constrains (Calinon et al. 2007). Also, a novel modified GMM/GMR method is used, which enables the robot to adapt the trajectory to environmental changes and to provide obstacle avoidance. The GMR is a real-time and analytic solution to produce smooth trajectory from the GMM/modified GMM. The produced trajectory can be used directly for the efficient robot control. The task is demonstrated offline multiple times in the unchanged environmental conditions and the adaptation module modifies the trajectories to meet the environmental changes appeared in the online robot functioning (working) phase. Table 1 shows a comparison between the related work and the presented novel approach for the skill learning at trajectory level with respect to number of human demos (single or multiple), method for reproduction, and possibilities for the adaptation to environmental changes.
Table 1
Comparison of related work for the low-level learning
Method for learning
Demonstrations from human
Method for reproduction
References
Different start pose
Different goal pose
Obstacle avoidance
DMP
Single
Modified DMP
$$\surd$$
$$\surd$$
$$\surd$$
Park et al. (2008)
SEDS
Multiple
SEDS
$$\surd$$
HMM
Multiple
HMM
$$\surd$$
$$\surd$$
Calinon et al. (2010a)
GMM
Single/multiple
GMR
Calinon et al. (2007)
GMM
Single/multiple
DS-GMR
$$\surd$$
$$\surd$$
Calinon et al. (2014)
GMM
Multiple
GMR/DMP
$$\surd$$
$$\surd$$
Ghalamzan et al. (2015)
Any method
Not specified
Laplace–Beltrami
$$\surd$$
$$\surd$$
$$\surd$$
Nierhoff et al. (2016)
GMM
Multiple
Modified GMM/GMR
$$\surd$$
$$\surd$$
$$\surd$$
Presented novel approach
### 2.2 Symbolic task learning (high-level learning)
In symbolic learning, the task is encoded according to the sequences of predefined motion elements. This approach allows the robot to learn the sequence of actions, so the robot can learn high-level task (Ekvall and Kragic 2006). A disadvantage of symbolic learning is that it relies on a priori knowledge to be able to abstract the important key-points of the demonstrated task.
For the abstraction and recognition of high-level skills, Hidden Markov Models (HMMs) have been widely used. HMM-based frameworks are used to generalize a task demonstrated multiple times to a robot (Kruger et al. 2010; Akgun and Thomaz 2016). The redundancies across all demos are identified and used for the reproduction of the task by the robot.
Another approach for the high-level task learning is the Growing Hierarchical Dynamic Bayesian Network (GHDBN) which is used for the representation and reproduction of complex actions from data (Dindo and Schillaci 2010). The GHDBN is a two-level Hierarchical Dynamic Bayesian Network (HDBN) where one level describes the high level representation of the task and the other describes the low level behavior of the robot.
A probabilistic approach for the representation and learning of complex manipulation based on multi-level Hierarchical Hidden Markov Model (HHMM) is presented in Patel et al. (2014), where the complex manipulation tasks are decomposed into multiple levels of abstraction to represents the actions in simpler way called action primitives.
A segmentation GMM-based framework provides task learning from a single demo (Lee et al. 2015). The GMM is combined with Principal component analysis (PCA) for dimensionality reduction and selection of the number of segments.
In the approach presented in this paper, the authors use a segmentation algorithm to split the demonstrated task to individual actions, and the Gaussians from the GMM model are grouped based on those actions.
### 2.3 Human–robot collaboration in industrial applications
As the robots are increasingly being used on factory floors, researchers are looking for the ways to help humans to work safe and more efficient with their electromechanical counterparts. In Weistroffer et al. (2014) the focus is on the acceptability of human–robot collaboration in industrial environments by designing a use case in which a human and a robot work side-by-side on the automotive assembly lines in physical and virtual environments. The results showed that the human collaborators preferred the virtual environment as the direct physical contact of the robot and the human collaborator is avoided. In some other works, the implementation of methods that enabled acceptance of direct human–robot object manipulation was investigated. For example, in Maeda et al. (2017) an imitation learning method based on probabilistic movement primitives is proposed and it is tested in the hand-over of objects between the robot and the human.
In this paper, the authors present a framework which enables human–robot cooperation in an industrial assembly application combined with the virtual environment-based situation awareness, which enables testing of robot’s movements before their execution.
## 3 Overview of the suggested robot learning framework
The overall structure of the proposed framework is shown in Fig. 1. The dual-arm industrial pi4 Workerbot 3 (http://www.pi4.de/english/systems/workerbot.html) is used as the framework robotic platform. It consists of two 6-degrees of freedom UR10 robotic arms controlled by the gravity-compensation controllers, which enables the use of the kinesthetic teaching for the human demo of the task to the robot. In the kinesthetic teaching, the human teacher demonstrates the task by grasping the robot’s end-effector and moving it along the appropriate trajectories throughout the task demo. In the used two-arm robotic platform, the end-effector of each robotic arm is an industrial vacuum gripper with two actuation status, “On” denoting the activated object manipulation (gripping) and “Off” denoting the not-activated gripping status. A Kinect for Xbox One camera (http://www.xbox.com/en-US/xbox-one/accessories/kinect) is mounted onto the head of the Workerbot and it is used as the vision-sensor which provides information about the working place, which is the working table located in front of the Workerbot and about the objects placed on the working table. The Kinect sensor features an RGB camera and a Depth sensor, and the Point Cloud Library (PCL—http://pointclouds.org/) is used to generate the point cloud of the scene from the Kinect sensor data and to process it.
As illustrated in Fig. 1, the proposed framework is organized in two main modules, the offline learning phase and the online working phase. A sub-module which is common for both main modules is the Environmental Perception module. This module processes the Point Could Data from the vision-sensor. Firstly, plane detection is performed to locate the working table with the objects placed on it. Secondly, a 3D-point cloud based processing object detection and recognition is performed. The output of this module is the information on position, orientation and dimension of every object on the working table with respect to the world coordinate system (Fang 2016).
During the learning (teaching) phase, all the actions needed to complete the assembly task are demonstrated via kinesthetic teaching several times by one or more human teachers (demonstrators). The working hypothesis of multiple demos is that the learning from a single demo has limitations as the human teacher may make mistakes during the demo so that the robot could be vulnerable to those mistakes. Also, the human teacher has a low precision compared to the robot and may perform unnecessary movements in attempts to be very precise in positioning the robot’s end-effector. Furthermore, as the different human demos lead to differently demonstrated skills, an optimally learned skill could outcome from a combination of different demos. Because of this, in the presented work, learning from multiple demos is suggested.
For the evaluation of the presented framework, an assembly of a robot gripper is selected as an appropriate industrial scenario. The assembly of the robot gripper consisting of 5 parts is illustrated in Fig. 2a. As shown, there are 4 objects, 4 gripper’s parts, which shall be assembled with the 5th, base part, to complete the assembly task. The manipulation of each gripper’s part, so called subtask, is done through the sequence of actions: “start arm moving”, “object grasping”, “arm moving while carrying the grasped object”, “object releasing” and “arm moving away from the working table”. During the demos, both robot arms can be used, but never at the same time because of safety. Different human collaborators are asked to demonstrate the complete task multiple times in the following order: manipulate the top part with the left arm (subtask 1), manipulate the black part with the right arm (subtask 2), manipulate the left side part with the left arm (subtask 3) and manipulate the right side part (subtask 4). The scenes after every manipulation are shown in Fig. 2a.
### 3.1 Offline learning phase
The offline learning module consists of the following 2 sub-modules:
• Data acquisition module This module records and stores in the robot database the joint angles, the end-effector pose of both robotic arms with respect to the world coordinate system as well as the actuation status of the grippers during the human demos. Each demo presents the complete assembly task. Additionally, this module stores in the database all the data provided by the Environmental Perception Module.
• Learning of sequence of actions module This module enables the robot to learn the sequence of actions needed to complete the demonstrated object manipulation task without the need for pre-programming by the human collaborator. The learning module is organized into two layers:
• High-level task learning compromising Symbolic Task Learning and consisting of the following steps: automatic task segmentation into actions (Sect. 4.1.1), which splits the task into subtasks and each subtask into actions, and labeling of the involved objects with specific IDs (Sect. 4.1.2).
• Low-level skill Learning comprising the Skill Learning at the trajectory level, which consists of two steps resulting in the learned end-effector path. These steps are: selection of similar demos (Sect. 4.2.1) and Gaussian mixture model (GMM)/Gaussian mixture regression (GMR) (Sect. 4.2.2).
The outcomes of the Learning of Sequence of Actions module are stored in the database and they are: the task segmented into actions; the position, orientation, dimensions and assigned ID of every involved object (as shown in Fig. 2b), the learned Gaussian mixture model (GMM) of the demonstrated end-effector paths and the learned end-effector paths generated by the GMR.
### 3.2 Online working phase
The online working phase is the phase in which the robot performs the learned task in real-time and the human collaborator is working together with the robot to complete the assembly task. In the presented scenario, the robot manipulates the gripper parts so to place them in appropriate places next to each other, while the human collaborator is supposed to screw the parts together in order to successfully complete the assembly task. Additionally, human collaborator also provides inputs to robot’s execution of the object manipulation tasks. Namely, before the task execution the learned sequence of actions will be displayed via Graphical User Interface (GUI) to the human collaborator. The human collaborator has than opportunity to either confirm the learned sequence of actions or to suggest new sequence of actions needed for completion of the task. Also, at the end of the robot’s task execution, the human collaborator provides a feedback (positive/negative) on the robot performance of particular sequence of actions. If the feedback is positive, the executed sequence of actions is stored so that only the sequences with the positive feedbacks are displayed to the human collaborator for the confirmation/adaptation before the next task execution.
The online phase consists of the following:
• Real-time adaptation module This module is organized into two layers:
• High-level adaptation module firstly performs object identification by identifying the objects on the working table based on their dimensions and pose. For the sake of explanation simplicity, the objects involved in the task during demo, which are stored in the database, are referred as original objects and the objects present in the scene in the working phase are current objects. The current objects are labeled based on their role in the task. In order to identify which current object matches which original object, the dimensions of the objects are compared. If there are more original objects with the same dimensions as the current object, the distance between the pose of each such original object and the pose of the current object is calculated. A current object is labeled with the ID of the original object of the same dimensions, which is the closest to the pose of the current object. The current objects, whose dimensions are not matched to any of the original objects, are treated as obstacles. An example of object identification and ID assignment is shown in Fig. 2c. Once the objects identification is completed, the learned sequence of actions is displayed via GUI to the human collaborator and he/she can confirm the sequence of actions or select a different one. For example, in the presented assembly scenario shown in Fig. 2a, the human collaborator can change the originally demonstrated sequence of actions by changing the order of the object manipulation. The originally learned sequence of actions and the newly suggested sequence of actions for the assembly of the same parts are shown in Fig. 2b, d respectively.
• Low-level adaptation module is a novel GMM-based method for the real-time adaptation of the learned low-level skills (trajectories) to the new environmental conditions. The new environmental conditions could arise due to changes in position and orientation of the objects as well as due to obstacles. The GMM-based adaptation is followed by the GMR method to generate the adapted path to be followed by robot’s end-effector so that the object manipulation task can be completed. Further details of this module are given in Sect. 5.
• Virtual environment-based situation awareness module A virtual environment has been developed using the ROS-based tool rviz (http://wiki.ros.org/rviz) to illustrate the robot’s environmental awareness and the robot’s execution of the learned task. For safety reasons in the suggested framework, the human collaborator firstly observes what the robot intents to do in the virtual environment and then, if safety criteria are satisfied, confirms that the real robot can perform the visualised sequence of actions.
## 4 Robot learning of sequence of actions for assembly task (offline learning phase)
### 4.1 High-level learning
This Module is responsible to learn the sequence of actions for the demonstrated assembly task. For the sake of explanation clarity, the following notations (Table 2) are introduced for this section.
#### 4.1.1 Task segmentation into actions
The inputs to the high-level task learning are the datasets $$\left\{ {L_m,R_m } \right\}$$. As example, the z dimension (blue line) of one demo of the gripper assembly scenario is shown in Fig. 3a, b for the left and right robot arm, respectively. As first, the task segmentation algorithm splits the task into subtasks. In Fig. 3a, b, the notations “Left Subtask $$n_L$$”, “Right Subtask $$n_R$$” mean that the $$n_L$$th, $$n_R$$ subtask, was performed by the left, right robot arm, respectively. After this, the algorithm segments the subtasks to the following sequence of actions: “start arm moving”, “object grasp”, “object release” and “stop arm moving” with the sub-paths, b and c that should be followed by the end-effector between those actions (Table 2). Segmentation of the subtasks into the sequence of actions is illustrated in Fig. 3a, b for the z-coordinate (dimension) of the end-effector. The segmented sub-paths abc are used as the input to the low-level learning (Sect. 4.2).
Table 2
Notations for Sect. 4
Data acquisition D Total number of demonstrations qx, qy, qz, qw The four quaternions $$L_m, R_m$$ Matrix of the left and right end-effector pose in Cartesian space {x, y, z, qx, qy, qz, qw} and$$m=1,\ldots ,D$$ ee.on, ee.off Index of the actuated and not-actuated end-effector state Task segmentation to actions $$P_L,P_R$$ Total number of times the left and right arm, respectively, was used to perform a subtask $$n_L , n_R$$ the number of subtasks for left and right robot arm, respectively a Sub-path between “start moving” and “grasp” actions b Sub-path between “grasp” and “release” actions c Sub-path between “release” and “stop moving” actions
#### 4.1.2 Object labeling
For the high-level learning of the task, that is for the learning of the sequence of task actions, the manipulated objects during the demonstration are labeled with specific IDs that denote the robot arm (left or right), which was used for the object manipulation and the role of the object in the subtask. For example, the ID “left_pick_$$n_L$$” means that the identified object was grasped (picked up) by the left robot arm during $$n_L$$th subtask. Since the proposed framework is focused on the assembly scenario, the “left_pick_$$n_L$$” object will be assembled with another object, which will then be labelled as “left_place_$$n_L$$”. In this ID “place” could mean that the object “left_pick_$$n_L$$” shall be placed onto the “left_place_$$n_L$$”. or shall be placed next to, that is aligned to, the “left_place_$$n_L$$”, depending on the demonstrated task. This labeling of the objects to be manipulated is a generic method where no matter how many objects are involved in the manipulation task the unique ID is assigned accordingly. Figure 2b shows the labeling of objects for the presented assembly scenario. One object can have more than one IDs, depending on its role in the task. For example the Base Part in Fig. 2b–d is denoted as “right/left_place_1/2” meaning that all gripper parts, those picked up by the left and right robot arms, shall be finally assembled with the base part.
### 4.2 Low-level learning
#### 4.2.1 Selection of similar demonstrations
During human demos via kinesthetic teaching, there are two main problems: the different duration of each demo and big variety in demos. In Fig. 4a, 9 different demos of the right subtask 1 are shown as an example. A widely used solution for the first problem is Dynamic Time Warping (DTW) (Akgun et al. 2012; Sabbaghi et al. 2014). Using of DTW also was proposed by the authors as possible solution of the second problem (Kyrarini et al. 2016, 2017). However, one disadvantage of DTW is the complexity of the algorithm which is time consuming (Movchan and Zymbler 2015).
In the presented work, a novel method for selection of similar demos without the use of DTW is proposed. More precisely, the proposed algorithm is able to select similar sub-paths. The sub-paths consists of data-points in 7 $$+$$ 1 dimensions {x, y, z, qx, qy, qz, qw, t}, where t is temporal variable, for the left and right arm are represented by $$L_{m,n_L,l},R_{m,n_R,l}$$, respectively, where $$n_L =\left\{ {1,\ldots ,P_L } \right\}$$, $$n_R =\left\{ {1,\ldots ,P_R } \right\}$$ and $$l=\left\{ {a,b,c} \right\}$$. The proposed algorithm is implemented in the following 3 steps:
• Step 1: Sub-paths of the same length (duration)
Since the sub-paths have different lengths (different duration of the end-effector movements between the actions of a sub-task) due to different speeds of performing the tasks during the demos, a variation of the Ramer–Douglas–Peucker (RDP) algorithm (Ramer 1972; Douglas and Peucker 1973) is used to provide sub-paths of the same length. The input to this algorithm are the desired length and the sub-paths $$L_{m,n_L,l},R_{m,n_R,l}$$, and the output is the RDP sub-paths $$L\_{ RDP}_{m,n_L,l} ,R\_{ RDP}_{m,n_R,l}$$. The desired length of the specified sub-path l is defined as the shortest length among the sub-paths of every group, where a group of the sub-paths consists of all the demos of the $$n_L$$th subtask for the left arm, that is of all the demos of the $$n_R$$th subtask for the right arm. In Fig. 4b, the output of this step is shown for nine different demos of the right subtask 1.
• Step 2: Calculation of similarity between the sub-paths of the same group
As mentioned above, the sub-paths are organized into groups. For every group, the dimensions {x, y, z} are normalized in the range of [− 1, 1] and a similarity matrix dist is computed as:
\begin{aligned} { dist}_n \left( {i,j} \right)= & {} w1*{ distPath}\left( {A\_{ RDP}_{i,n_A,l},A\_{ RDP}_{j,n_A,l} } \right) \nonumber \\&+\,w2*{ distIP}\left( {A\_{ RDP}_{i,n_A,l},A\_{ RDP}_{j,n_A ,l} } \right) \nonumber \\ \end{aligned}
(1)
where: $$i,j=\left\{ {1,\ldots ,D} \right\}$$, $$A=\left\{ {L,R} \right\}$$, $$n_A =\left\{ {n_L,n_R } \right\}$$. distPath is the 7 dimensional {x, y, z, qx, qy, qz, qw} Manhattan point-to-point distance between the points of two sub-paths, distIP is the 7 dimensional Manhattan distance between the important points (IP) of two sub-paths where important points in assembly task are the grasping and releasing points, w1 and w2 are the weights which satisfy the following equations: $$0\le w1\le 1,w2=1-w1$$.
The similarity vector is calculated as follows:
\begin{aligned} { similarity}\left( i \right) =\mathop \sum \limits _{j=1}^D { dist}_n \left( {i,j} \right) ,\forall j \epsilon \left\{ {1,\ldots ,D} \right\} \end{aligned}
(2)
• Step 3: Selection of demonstrations for every sub-path group
The presented algorithm gives the option to the human demonstrator to select a number of desired demos $$D_s <D$$. For every group of sub-paths, the demo with the smallest value in the vector similarity is selected as the “reference” demo r. Then, the algorithm selects the reference demo and $$D_s -1$$ demos that have minimal distance $${ dist}_n \left( {r,j} \right) ,\forall j\in \left\{ {1,\ldots ,D} \right\} ,j\ne r$$.
The selected demos for every sub-path group are joined together to create a complete path for each subtask as follows:
\begin{aligned} A\_{ RDP}_{k,n} =A\_{ RDP}_{k,n,a} \cup A\_{ RDP}_{k,n,b} \cup A\_{ RDP}_{k,n,c}\nonumber \\ \end{aligned}
(3)
where $$k=\left\{ {1,\ldots ,D_s } \right\}$$.
The above demos are the output of the selection of similar demos. In Fig. 4c, the selected demos of the right subtask 1 of the gripper assembly scenario is shown as example. Additionally, the gripper actuated and not-actuated state is mapped to the $$A\_{ RDP}_{k,n}$$. The notation of the matrix index $$A\_{ RDP}_{k,n}$$ is $$ee.on={ size}\left( {A\_{ RDP}_{k,n,a} } \right)$$ for the actuated state and $$ee.off={ size}\left( {A\_{ RDP}_{k,n,a} \cup A\_{ RDP}_{k,n,b} } \right)$$ for the not-actuated state, where size is a function to find the number of data-points.
#### 4.2.2 Gaussian mixture model (GMM)/Gaussian mixture regression (GMR)
The input to GMM is the above described result on the selection of similar demos. The GMM is used to extract constrains of the aligned trajectories (Calinon et al. 2007) and GMR is used to produce the learned end-effector path which can be used to control the robot efficiently (Calinon 2009).
The set of selected demos are fed to the learning system that trains the GMM in order to build the probabilistic model of the data. Every demo consists of data-points $$\beta _\gamma =\left\{ {\beta _s ,\beta _t } \right\}$$, where $$\beta _s \in R^{7}$$, s is spatial variables, $$\beta _t \in R$$. In the presented approach the dimensionality of the data-points is equal to 8; 7 dimensions {x, y, z, qx, qy, qz, qw} and the temporal dimension. In the learning phase, the model is created with a predefined number N of Gaussians. Each Gaussian consists of the following parameters: mean vector, covariance matrix and the prior probability. Each Gaussian has a dimensionality 8. The probability density function $$p\left( {\beta _\gamma } \right)$$ for a mixture of N Gaussians is calculated based on the following equation (Calinon 2009)
\begin{aligned} p\left( {\beta _\gamma } \right) =\mathop \sum \limits _{n=1}^N \pi _n \frac{1}{\sqrt{\left( {2\pi } \right) ^{8}}\left| {\varSigma _n } \right| }e^{-\frac{1}{2}\left[ {\left( {\beta _\gamma -\mu _n } \right) ^{T}\varSigma _n ^{-1}\left( {\beta _\gamma -\mu _n } \right) } \right] }\nonumber \\ \end{aligned}
(4)
where: $$\pi _n$$ are the prior probabilities, $$\mu _n =\left\{ {\mu _{n,t},\mu _{n,s} } \right\}$$ are the mean vectors and $$\varSigma _n =\left( {{\begin{array}{ll} {\varSigma _{n,t} }&{} {\varSigma _{n,ts} } \\ {\varSigma _{n,st} }&{} {\varSigma _{n,s} } \\ \end{array} }} \right)$$ are the covariance matrices of the GMM. The parameters (prior, mean and covariance) of the GMM are estimated by the expectation-maximization (EM) algorithm (Dempster et al. 1977). In Figs. 4c and 6a, the GMM for one subtask of the gripper assembly scenario is shown.
Table 3
Notations for Sect. 5
Offline Learning Phase: Output N Total number of Gaussians in the GMM model i $$i=\left\{ {1,\ldots ,7} \right\}$$ represents the dimensions {x, y, z, qx, qy, qz, qw} respectively j $$j=\left\{ {1,\ldots ,N} \right\}$$ the number of the Gaussian respectively k $$k=\left\{ {1,\ldots ,7} \right\}$$ represents the position, orientation and dimensions for the objects {x, y, z, yawangle, length, width, height}, respectively $${ GM}_{i,j}$$ Mean values of the learned GMM for 7 dimensions of the end effector of each robotic arm pick The Gaussian that corresponds to the grasping point ee.on.index in the learned path $${\hat{\beta }}$$ place The Gaussian that corresponds to the releasing point ee.off.index in the learned path $${\hat{\beta }}$$ $$Obj.pick_k$$ Original object position and orientation for an object to be picked up (grasped) $$Obj.place_k$$ Original object position and orientation for an object to be placed (released) $$ee.on_i, ee.{ off}_i$$ Position and Orientation (quaternion) of the end effector when gripper actuation status is on, off in the learned path $${\hat{\beta }}$$ Online working phase: environmental perception $$Obj.pick^{\prime }_k$$ Current object position and orientation for a pick object $$Obj.place^{\prime }_k$$ Current object position and orientation for a place object $$Obj.obst^{\prime }_k$$ Current object position and orientation for an obstacle Online working phase: output of the modification of Gaussian means of the learned GMM $$GM^{\prime }_{i,j}$$ Mean values of the modified GMM for 7 dimensions of the end effector of each robotic arm
The learned GMM parameters for the task are given as input to the GMR in order to generalise a path. The GMR has the advantage that generates a fast and optimal output from the GMM (Calinon 2009). The output path $${\hat{\beta }}$$ of the GMR is calculated as:
\begin{aligned} {\hat{\beta }}=\left\{ {\beta _t,\mathop \sum \limits _{n=1}^N a_n {\hat{\beta }}_{n,s} } \right\} \end{aligned}
(5)
where: $$a_n =\frac{p(\beta _t |n)}{\mathop \sum \nolimits _{n=1}^N p(\beta _t |n)}$$ and
\begin{aligned} {\hat{\beta }}_{n,s} =\mu _{n,s} +\varSigma _{n,st} \left( {\varSigma _{n,t} } \right) ^{-1}\left( {\beta _t -\mu _{n,t} } \right) , \forall n=\left\{ {1,\ldots ,N} \right\} . \end{aligned}
In Figs. 4d and 6b, the generated GMR path from the learned GMM is shown.
An algorithm based on GMM is used for the adaptation of a learned task (end-effector path) to different poses of the involved objects and to obstacle avoidance. This algorithm starts from the real-time object identification so that the robot knows which of the identified objects shall be grasped (picked up), with which robot arm and where those objects shall be released (placed). Secondly, the algorithm uses the human collaborator input on the sequence of actions, either confirmation of the learned sequence or suggestion of a different sequence (as explained in Sect. 3). Then, a novel robust algorithm is introduced that modifies the means of the learned Gaussian Model for the task in order to adapt to the new pose of the objects and to avoid collision with obstacles in real time. Once the new GMM has been created, the GMR is used to generate the new path (low-level) which is mapped to the learned actions (high-level) of the task. The execution of the task is performed by the real robot. The notations that are used in this section can be found in Table 3.
### 5.1 Modification of Gaussian means of the learned Gaussian mixture model
In this section, the proposed algorithm for modification of the means of learned Gaussians is explained in order to successfully adapt the actions of the task to the position (dimension xy) and orientation of the current objects. The dimension z is also modified only when there are obstacles in order to avoid collision.
The inputs of the proposed algorithm are the outputs of the offline learning phase: GM, pick, place, N, Obj.pick, Obj.placeee.on, ee.off, and the output of the environmental perception module for the current identified objects: $$Obj.pick^{\prime }$$, $$Obj.place^{\prime }$$ and $$Obj.obst^{\prime }$$
The Algorithm 1 explains how the modification of Gaussian Means is performed. Algorithms 2–4 explain functions that are used in Algorithm 1. The Algorithm 1 is generic and it does not depend on the number of Gaussians (as long as the Gaussians are more than 4).
The algorithm 1 consists of the following steps in order to achieve the modification of the Gaussians for the specific environment:
Step 1: New mean values for first and last Gaussians (Algorithm 1, line 1–4)
The new mean values for the first and last Gaussians are equal to the mean values of the first and last learned Gaussians, as shown in Fig. 4c. The first and last Gaussian represents a position in which the arm is far away from the working table.
Step 2: Identification of the pick and place Gaussians
The pick and place Gaussians are identified by mapping the position of the end-effector in which the gripper should grasp (pick) and release (place) the object to the corresponding Gaussians, as shown in Fig. 4c.
Step 3: Modification of mean value for pick and place Gaussians (Algorithm 1, line 5)
The new mean values of the pick and place Gaussians are modified based on the new position and orientation of the current objects, by calling the function for modification of pick and place Gaussian means (Algorithm 2). In Algorithm 2 the mean values for the pick and place Gaussians are calculated in lines 2–5 for the dimensions xy. An example of modification of the pick Gaussian can be seen in Fig. 4e. The dimension z is not needed since the current and the original objects are the same (so they have same height). To calculate the mean values for the quaternions, there is the need to know firstly the difference (in quaternion) between the yaw angle of the current object and of the original object. The angle difference in quaternion for the pick and place object is calculated in the lines 6 and 7 of Algorithm 2 with the help of the function “findRot” which is described in Algorithm 3. After the Algorithm 3 calculates the change of the object angle in quaternions, the product of two quaternions is calculated. The first quaternion is calculated from the Algorithm 3 and the second quaternion is the orientation of end effector when the gripper grasped or released an object in the learned path (Algorithm 2, lines 8 and 9). Finally, the modified mean values for the pick and place Gaussians for the quaternion are calculated in lines 10–13 of the Algorithm 2.
Step 4: Find close Gaussians to pick and place Gaussians (Algorithm 1, line 6)
The Gaussians that are close to the pick and place are found by calling the function “findCloseGaus”. This function compares the difference between each Gaussian mean and the ee.on, ee.off separately for each dimension {x, y, z, qx, qy, qz, qw} and, if this difference is smaller than a defined threshold value, then this Gaussian is selected as close. The output of this function is $$closeGaus_{i,m}$$, where $$m=\left\{ {1,\ldots ,4} \right\}$$ represents the close Gaussians before pick, after pick, before place, after place, respectively. The reason the close Gaussians needs to be determined is to perform the task more accurately since the most important Gaussians are those near the pick and place. An example of close Gaussians can be seen in Fig. 4c.
Step 5: Modification of mean values of the close Gaussians (Algorithm 1, line 7)
The mean values of the close Gaussians are modified by calling the function “modCloseGM”. At first, this function calculates the difference $${ diff}_p ={ GM}^{\prime }_{i,p} - { GM}_{i,p}$$, for $$p=\left\{ { pick},{ place} \right\}$$. Next, the close Gaussians are also modified by the same difference $${ diff}_p$$. An example of the modification of close Gaussians is shown in Fig. 4f.
Step 6: Modification of mean values of the remaining Gaussians (Algorithm 1, line 8–14)
The mean values of the remaining Gaussians are also modified by calling the function “modMidGM” (Algorithm 4) for the intermediate Gaussians to provide a smoother path. An example of the modification of intermediate (remaining) Gaussians is shown in Fig. 4g.
Step 7: Find Gaussians which are in collision with obstacles (Algorithm 1, line 15)
The function “findObsGM” determines which Gaussians are in collision with the identified obstacles. Every edge {x, y, z} of a bounding box for every obstacle is compared with the $${ GM}^{\prime }$$. If a mean value of the $${ GM}^{\prime }$$ is inside the obstacle’s bounding box, then this Gaussian is flagged as “Gaussian in obstacle”. Furthermore, for the Gaussians between the pick and place Gaussians, the dimensions of the picked object are also taken into account.
Step 8: Modification of mean values Gaussians which are in collision with obstacles (Algorithm 1, line 16)
The last step is to provide the modification of the Gaussians in order to avoid collision with obstacles. The mean values of Gaussians in obstacles are modified by adding the obstacle’s height to the z dimension of the $${ GM}^{\prime }$$ or, if the Gaussians in obstacles are in between pick and place Gaussians, by adding the obstacle’s height plus the picked current object’s height to the z dimension of the $$GM^{\prime }$$ plus a safety distance. The obstacle avoidance happens in z dimension as shown in Fig. 6c. The assumption is that the position of obstacles does not prevent the completion of the task, i.e. obstacle is not on the target position.
### 5.2 Gaussian mixture regression (GMR)
The modified mean vector ($${ GM}^{\prime }$$ or $$\mu ^{\prime }_{n,s} )$$, which is the output of the presented algorithm in Sect. 5.1 will be used to generate the adapted to the changed environment path $${\hat{\beta }}^{\prime }$$ via GMR. The Eq. (5), presented in Sect. 5.2, will be modified to the following equation:
\begin{aligned} {\hat{\beta }}^{{\prime }}=\left\{ {\beta _t,\mathop \sum \limits _{n=1}^N a_n {\hat{\beta }}_{n,s}^{\prime } } \right\} \end{aligned}
(6)
where $${\hat{\beta }}_{n,s}^{\prime } =\mu ^{\prime }_{n,s} +\varSigma _{n,st} \left( {\varSigma _{n,t} } \right) ^{-1}\left( {\beta _t -\mu _{n,t} } \right)$$, $$\forall n=\left\{ {1,\ldots ,N} \right\}$$.
The adapted path $${\hat{\beta }}^{\prime }$$ has all the essential features (i.e. pick and place) of the demos but, additionally, adapts to the new environmental conditions, as shown in Figs. 4h and 6d.
## 6 Real robot experimental results in an industrial assembly scenario
In the presented work, the assembly of a robot gripper is selected as an industrial assembly scenario to evaluate the suggested robot learning framework, as explained in Sect. 3.
Figure 5a shows a real-time working environment, in which the human collaborator set up the gripper parts in poses different from the demonstrated ones. Additionally, the human collaborator has selected a sequence of actions different from the demonstrated one. The robot performs the suggested sequence together with the human collaborator, as shown in Fig. 5b. After each subtask is completed by the robot, which is after two gripper parts are placed next to each other, the human screws the parts together. After that, for safety reasons, human collaborator confirms in Virtual Environment-based Situation Awareness module that the robot can continue with the next subtask. At the end of the sub-task, the human collaborator provides a feedback if the sub-task sequence of actions was performed well or not by the robot.
Figure 6e shows a real-time execution of the right subtask 2 (sequence based on Fig. 2d), in which an additional object is added as an obstacle. The robot was able to avoid the obstacle but the picked object (black part) was not positioned properly. The reason is that the black part is heavy (1 kg) and it oscillated during the manipulation by the vacuum gripper which caused the object misplacement.
## 7 Conclusion and future work
In this paper, a robot learning framework for industrial assembly applications is presented. The task is demonstrated in multiple human demos via kinesthetic teaching. The robot learns the sequence of actions (high-level) and the end-effector paths (low-level) needed to complete the assembly task. The learning is done in the offline learning phase while the reproducing of the learned actions and paths is done in the online working phase. This reproduction is possible even in the case of the changes in environment, such as different poses of the objects to be manipulated and present obstacles. Additionally, the framework offers to the human collaborator the possibility to change the order of the sequence of actions without additionally training.
A novel method for selection of similar demos is suggested and implemented and GMM/GMR is used to reproduce the learned path based on the selected demos. This method also copes with the human demonstrator imprecision in placing the objects during demos.
In the online working phase, a novel modification of the GMM algorithm for the adaptation to environmental changes is suggested and implemented. The algorithm is tested in a real-world assembly scenario with a dual-arm industrial robot collaborating with a human and the experimental results are presented.
## Notes
### Acknowledgements
The research was supported by the German Federal Ministry of Education and Research (BMBF) as part of the project MeRoSy (Human Robot Synergy). The authors thank MeRoSy industrial project partner pi4 robotics GmbH for the technical support in assembly scenario.
## Supplementary material
Supplementary material 1 (mp4 144950 KB)
Supplementary material 2 (mp4 21763 KB)
Supplementary material 3 (mp4 189617 KB)
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## Authors and Affiliations
• Maria Kyrarini
• 1
• 1
• Danijela Ristić-Durrant
• 1
• Axel Gräser
• 1
1. 1.Institute of Automation (IAT)University of BremenBremenGermany
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https://www.semanticscholar.org/paper/MOST-Detects-g-Modes-in-the-Late-Type-Be-Star-%CE%B2-(B8-Saio-Cameron/c3a86a80b53564b3368827968d94504e95ccd983
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# MOST Detects g-Modes in the Late-Type Be Star β Canis Minoris (B8 Ve)
@article{Saio2007MOSTDG,
title={MOST Detects g-Modes in the Late-Type Be Star $\beta$ Canis Minoris (B8 Ve)},
author={H. Saio and C. Cameron and R. Kuschnig and G. Walker and J. Matthews and J. Rowe and U．Lee and D. Huber and W. Weiss and D. Guenther and A. Moffat and S. Rucinski and D. Sasselov},
journal={The Astrophysical Journal},
year={2007},
volume={654},
pages={544-550}
}
The Microvariability and Oscillations of Stars (MOST) satellite has detected low-amplitude light variations (?m ~ 1 mmag) in the Be star ? CMi (B8 Ve). The observations lasted 41 days and the variations have typical periods ~0.3 days. We demonstrate that the dominant frequencies are consistent with prograde high-order g-modes of m = -1 excited by the Fe bump of opacity in an intermediate-mass (?3.5 M?) star with a nearly critical rotation period of 0.38 days. This is the first detection of… Expand
51 Citations
Pulsations in the late-type Be star HD 50 209 detected by CoRoT
Kepler observations of the variability in B-type stars
Recent MOST space photometry
Multiperiodicity in the newly discovered mid-late Be star V2104 Cygni
• Physics
• 2007
Asteroseismic observations of OB stars
• Physics
• Proceedings of the International Astronomical Union
• 2010
TESS observations of Be stars: a new interpretation.
• Physics
• 2019
Short-term variations in Be stars observed by the CoRoT and Kepler space missions
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https://astrophytheory.com/2021/02/18/a-very-brief-introduction-to-measure-theory-and-the-lebesgue-integral-part-i/
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# A Very Brief Introduction to Measure Theory and the Lebesgue Integral (Part I)
In the next few posts, I shall be discussing recent topics of study that, to me at least, have been very intruiging. In previous posts, I have talked about Hilbert spaces. I have of late been considering the mathematics necessary to formally understand in a pure mathematical sense what a Hilbert space is. This post, like the others on this site, serves as a reference of newly learned topics that are of interest (to me, at least; such a comment is subjective, of course).
The purpose of this post is two-fold: (1.) to provide an update with what I’ve been up to; (2.) introduce some interesting mathematics that have expanded my understanding to the “size” of a set as well as operations such as differentiation and integration.
Here is a quick summary of what I plan to cover in the next few posts (to a brief extent):
1. Elementary Sets and their Measure: Here I will discuss the concept of length and try extend length in greater dimensions to that of a measure of a set. Much of this topic will rely on geometric intuition.
2. Lebesgue Measure: This section will dicuss the concept of Lebesgue measure and distinguish it from the elementary measure. Also brief mention will be made of measurability of sets and functions.
3. General Measure: Discussion will be made of a general measure as a function as well as measurable spaces and measure spaces.
4. Lebesgue Integral: This topic will introduce the concept of the Lebesgue integral as compared to the Riemann integral.
5. $L^{p}$ and $l^{p}$ spaces: This section will discuss the concept of a norm as it relates to the spaces $L^{p}$ and $l^{p}$, and will define each space. We will also introduce the concept of Banach spaces.
6. Proof that $l^{p}$ space is a Banach space.
Section 1: Elementary Sets and their Measure:
The question that we want to answer is this: Given an arbitrary set, how do we go about measuring it?
In order to understand the difficulties present in this question we must first consider what are called elementary sets and the elementary measure. Elementary sets are those sets which are intuitively easy to measure; that is, intervals, rectangles, and boxes. We now give the formal definition of an elementary set:
Definition. (Interval; Elementary Set) We define an interval to be a subset of the real line $\mathbb{R}$ which take one of the following forms:
$[a,b] := \{x\in \mathbb{R}|a\leq x \leq b\} \label{(1.1)}$;
$[a,b) := \{x\in \mathbb{R}|a\leq x < b\} \label{(1.2)}$;
$(a,b] := \{x\in \mathbb{R}|a< x\leq b\} \label{(1.3)}$;
$(a,b):= \{x\in \mathbb{R}|a< x< b\} \label{(1.4)}$,
The length of an interval $I=[a,b]$ denoted $l(I):= b-a$. For dimensions $d\geq 2$, we define the measure of such sets as equalling the $d$-times Cartesian product of intervals $I_{d}$; that is,
$\displaystyle m(B) := \prod_{i=1}^{d}l(I_{i}); \label{(2)}$
we sometimes call sets of dimension 2 or greater as “boxes.” Thus, elementary sets are those subsets of $\mathbb{R}^{d}$ such that
$\displaystyle m(E)= \bigcup_{i=1}^{d}m(B_{i}), \label{(3)}$
where $B$ is $i$-th $d$-dimensional box contained in $\mathbb{R}^{d}$.
What this definition is doing is the following: first it introduces the concept of an interval and establishes the well-understood concept of its length as being the difference between the two endpoints provided one is less than the other. The definition then generalizes the idea of a length to 2 and 3 dimensions and beyond. Note that in 2-dimensions the interval then becomes a rectangle in the plane. Thus, the measure of the length of an interval then becomes the measure of the area of a rectangle. Similarly, for $d=3$ we replace rectangles with cubes and the area with the volume. For dimensions $d>3$, we replace cubes with boxes of $d$-dimension. Therefore, elementary sets are those subsets of $d$-dimensional real space that are unions of finitely-many boxes.
Section 2: Lebesgue Measure
In the last section, we discussed sets for which we can measure quite easily. Though ideally we would like to be able to measure more general sets; that is, sets that are more general than elementary sets. Therefore, we require a different way of measurement. Thus, we come to need the Lebesgue measure.
In order to introduce the Lebesgue measure we need to first introduce the concept of the outer measure, which we now define
Definition. (Outer Measure) We define the outer measure of a set $E\subset \mathbb{R}$, denoted $m^{*}(E)$ to be
$\displaystyle m^{*}(E) = \inf\bigg\{\sum_{k=1}^{\infty}l(I_{k})|\forall k\in \mathbb{N}, I_{k} \text{ is open such that } E \subset \bigcup_{k=1}^{\infty}I_{k}\bigg\}.$
The outer measure of a set in a sense “overestimates” the size of a given set and then takes the smallest such overestimate to within a specified tolerance. Thus, it estimates the size of the given set “from the outside,” and is used in lieu of the elementary measure when we are dealing with sets that we cannot easily measure the set in a geometrically-intuitive way.
We conclude this post with the definition of the Lebesgue measure given in two forms; the first will be in terms of what we have defined so far, and the second will be defined in terms that will be covered in the next post.
Definition. (Lebesgue Measure.) We define the Lebesgue measure of the set $E$ to be a set whose measure $m(E)=m^{*}(E)$; that is, its measure is equal to the outer measure.
The second way of defining this is as follows:
Definition. (Lebesgue Measure V.2) The Lebesgue measure is the measure on the measureable space $(\mathbb{R},\mathcal{L})$ where $\mathcal{L}$ is the $\sigma$-algebra of Lebesgue measurable subsets of $\mathbb{R}$ that assigns to each Lebesgue measurable set its outer measure.
The next post will discuss measures in general, as well as measurable sets, measureable spaces, Borel sets, and $\sigma$-algebras.
Until then, clear skies!
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