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http://mathhelpforum.com/calculus/4900-bisection-root-algorithm-print.html
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# bisection root algorithm
• Aug 13th 2006, 08:36 AM
bobby77
find the root of f(x)=2x^3-x^2+x-1=0 to 3 decimal places using interval bisection.
• Aug 13th 2006, 08:57 AM
CaptainBlack
1 Attachment(s)
Quote:
Originally Posted by bobby77
find the root of f(x)=2x^3-x^2+x-1=0 to 3 decimal places using interval bisection.
First sketch the graph to locate the approximate position of the root.
See attachment:
Now we see the root is located at about $x=0.7$. Now we need
a pair of values $x_{lo}, x_{hi}$ such that $x_{lo} such that
$sgn(f(x_{lo}) \ne sgn(f(x_{hi})$.
It looks as though $0.6, 0.8$ will do for these (check).
Now we need a table:
Code:
``` x_lo x_hi f(x_lo) f(x_hi) x_mid f(x_mid) 0.6 0.8 -0.328 0.184 0.7 -0.104```
This is the first row, the next row is obtained by replacing $x_{lo}$ or $x_{hi}$ by $x_{mid}$, so that we
still bracket the zero, thus:
Code:
``` x_lo x_hi f(x_lo) f(x_hi) x_mid f(x_mid) 0.6 0.8 -0.328 0.184 0.7 -0.104 0.7 0.8 -0.104 0.184 0.75 0.0312 0.7 0.75 -0.104 0.0312 0.725 -0.0385```
and so on utill $|x_{hi}-x_{lo}|<0.001$.
RonL
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http://mathhelpforum.com/statistics/53135-word-combinations-problem.html
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# Thread: word combinations problem
1. ## word combinations problem
How many ways can 4 people be chosen from a group of 9? Tell whether the situation is a permutation of combination. Then solve.
2. Originally Posted by biggestbernard1
How many ways can 4 people be chosen from a group of 9? Tell whether the situation is a permutation of combination. Then solve.
this is just "9 choose 4", or in other words, ${9 \choose 4} = _9C_4$
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https://www.mathdoubts.com/factoring-quadratic-equations/
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A mathematical approach of converting the quadratic expression into a product of two factors is called the factorization (or factorisation) of the quadratic equation.
## Introduction
A quadratic expression is a second degree polynomial. So, it has two roots. The idea of converting a quadratic expression as a product of two linear expressions in one variable helps us to find the zeros (or roots) of any quadratic equation easily. This method is called the factorization (or factorisation) of quadratic equations.
$ax^2+bx+c \,=\, 0$ is a general form of a quadratic equation.
Now, take the literal coefficient of $x^2$ common from all the terms in the quadratic equation.
$\implies$ $a\bigg(x^2+\Big(\dfrac{b}{a}\Big)x+\dfrac{c}{a}\bigg) \,=\, 0$
Completing the square method is used to derive a quadratic formula for finding the roots of a quadratic equation.
$x \,=\, \dfrac{-b \pm \sqrt{b^2-4ac}}{2a}$
$\implies$ $x \,=\, \dfrac{-b+\sqrt{b^2-4ac}}{2a}$ or $x \,=\, \dfrac{-b-\sqrt{b^2-4ac}}{2a}$
If the roots of a quadratic equation are denoted by alpha and beta, then its solutions are expressed as follows.
$(1).\,\,\,$ $\alpha \,=\, \dfrac{-b+\sqrt{b^2-4ac}}{2a}$
$(2).\,\,\,$ $\beta \,=\, \dfrac{-b-\sqrt{b^2-4ac}}{2a}$
The sum and product of the roots of the quadratic equations are expressed as follows.
$(1).\,\,\,$ $\alpha+\beta \,=\, -\dfrac{b}{a}$
$(2).\,\,\,$ $\alpha \beta \,=\, \dfrac{c}{a}$
Now, the general form quadratic equation $a\bigg(x^2+\Big(\dfrac{b}{a}\Big)x+\dfrac{c}{a}\bigg) \,=\, 0$ can be expressed in terms of sum and product of the zeros (or roots).
$\implies$ $a\bigg(x^2-\Big(-\dfrac{b}{a}\Big)x+\dfrac{c}{a}\bigg) \,=\, 0$
$\implies$ $a\Big(x^2-(\alpha+\beta)x+\alpha \beta\Big)$ $\,=\,$ $0$
Now, it is time to factor this quadratic equation mathematically.
$\implies$ $a\Big(x^2-x \times (\alpha+\beta)+\alpha \times \beta\Big)$ $\,=\,$ $0$
$\implies$ $a(x^2-x \times \alpha$ $-$ $x \times \beta+\beta \times \alpha)$ $\,=\,$ $0$
$\implies$ $a\Big(x \times x-x \times \alpha$ $-$ $\beta \times x-\beta \times (-\alpha)\Big)$ $\,=\,$ $0$
$\implies$ $a\Big(x \times (x-\alpha)$ $-$ $\beta \times (x-\alpha)\Big)$ $\,=\,$ $0$
$\implies$ $a\Big((x-\alpha) \times x$ $-$ $(x-\alpha) \times \beta\Big)$ $\,=\,$ $0$
$\,\,\,\therefore\,\,\,\,\,\,$ $a(x-\alpha)(x-\beta)$ $\,=\,$ $0$
Therefore, the quadratic equation $ax^2+bx+c = 0$ is factored as $a(x-\alpha)(x-\beta) = 0$
### Solution
List of the steps for factoring a quadratic equation and an example to learn how to solve the quadratic equation by the factorization (or factorisation) method.
#### Problems
List of the questions on quadratic equations with step by step solution to learn how to factor a quadratic equation for solving the quadratic equation by factoring.
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https://www.gamedev.net/forums/topic/74123-how-to-maintan-aspect-ratio-with-bitblt/
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• ### Announcements
#### Archived
This topic is now archived and is closed to further replies.
# How to maintan aspect ratio with bitblt?
## Recommended Posts
Aman 122
Any ideas (theory) on how to maintan an aspect ratio using bitblt? MSVC++ 6, GDI I have a source bitmap of x size (arbatrary size) I have a destination rect of set size (96x96) Currently I just StretchBlt. I would like to maintan the aspect ratio with a black backgound. Any ideas? (theroy, steps, process not just cut/paste code) Thanks up front, Aman
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Guest Anonymous Poster
Well.. it''s actually pretty simple... you could trying something like this..
void BlitImage(long DestHdc, long SrcHdc, BitmapSizeX, BitmapSizeY) { float Ratio, size; if (BitmapSizeX>BitmapSizeY) //X > Y! { Ratio = 96.0/BitmapSizeX; size = Ratio*BitmapSizeY; //Size Y in new ratio!//48.0-size/2.0 centers the bitmap! StretchBlt(DestHdc,0,48.0- size/2.0,96.0,size,SrcHdc,0,0,BitmapSizeX,BitmapSizeY,SRCCOPY); } else //Y > X! { Ratio = 96.0/BitmapSizeY; size = Ratio*BitmapSizeX; //Size X in new ratio!//48.0-size/2.0 centers the bitmap! StretchBlt(DestHdc,48.0-size/2.0,0,size,96.0,SrcHdc,0,0,BitmapSizeX,BitmapSizeY,SRCCOPY); }}
Basically what this does is checks which ratio is going to be larger (X or Y ratio). If the x is larger, then the bitmap will be completely across, and leave gaps at the top/bottom (to keep aspect ratio). If the y is larger, then the opposite happens. It''s really simple actually.
Billy - [email protected]
Disclaimer: This was written in this text box, and is subject to mispellings, and non-compiling problems without warning... so use at your own risk :o)
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https://simple.wikipedia.org/wiki/Damping
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Damping
Graph of a damped vibratory deflection y.
Damped spring.
In physics, damping is any effect that tends to reduce the amplitude of vibrations.[1]
In mechanics, the internal friction may be one of the causes of such damping effect. For many purposes the damping force Ff can be modeled as being proportional to the velocity v of the object:
${\displaystyle F_{\mathrm {f} }=-cv\,,}$
where c is the damping coefficient, given in units of Newton-seconds per meter.
References
1. Tongue, Benson, Principles of Vibration, Oxford University Pres, 2001, ISBN 0-195-142462
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http://al-roomi.org/economic-dispatch/15-units-system
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# IEEE 15-Units ELD Test System
I. Introduction:
$$\bullet$$ This system contains fifteen generating units with a load demand of 2630 MW. Some researchers could evaluate their proposed optimization algorithms with different load demands.
$$\bullet$$ The fuel-cost function of this test system is modeled using the quadratic cost function as follows:
$$C_i\left(P_i\right) = a_i + b_i P_i + c_i P^2_i$$ .......... $$(1)$$
where $$a_i$$, $$b_i$$, and $$c_i$$ are the function coefficients and tabulated in Table 1.
$$\bullet$$ The network losses are modeled, by using Kron's loss formula, as follows:
$$P_L = \sum_{i=1}^{n} \sum_{j=1}^{n} P_i B_{ij} P_j + \sum_{i=1}^{n} B_{0i} P_i + B_{00}$$ .......... $$(2)$$
where $$B_{ij}$$, $$B_{0i}$$, and $$B_{00}$$ are called loss coefficients (or just B-coefficients) and listed below:
$$\bullet$$ If the ramp-rate limits are modeled as constraints in the design function, then the feasible search space of each unit is determined through the following equation:
$$\text{max}\left(P_i^{min},P_i^{now}-R_i^{down}\right) \leqslant P_i^{new} \leqslant \text{min}\left(P_i^{max},P_i^{now}+R_i^{up}\right)$$ .......... $$(3)$$
where $$P_i^{now}$$ and $$P_i^{new}$$ are respectively the existing and new power output of the $$i$$th generator. $$R_i^{down}$$ and $$R_i^{up}$$ are respectively the downward and upward ramp-rate limits, which are tabulated in Table 2.
$$\bullet$$ Also, if the prohibited operating zone phenomenon is considered in the design function of the ELD problem, then the fuel-cost curves will have some discontinuities. This constraint can be modeled as follows:
\begin{align} P_i^{min} & \leqslant P_i \leqslant P_{i,j}^L \\ P_{i,j}^U & \leqslant P_i \leqslant P_{i,j+1}^L \text{ .......... $$(4)$$}\\ P_{i,\varkappa_i}^U & \leqslant P_i \leqslant P_i^{max}\end{align}
where $$P_{i,j}^L$$ and $$P_{i,j}^U$$ are respectively the lower and upper bounds of the $$j$$th prohibited operating zone on the fuel-cost curve of the $$i$$th unit. $$\varkappa_i$$ means the total number of the prohibited operating zones exist within the $i$th unit. Based on that, Table 2 is updated to Table 3.
$$\bullet$$ In [6] and [11], the valve-point loading effects are considered in the cost function, so (1) becomes:
$$C_i\left(P_i\right) = a_i + b_i P_i + c_i P^2_i + \left|d_i \times \sin\left[e_i \times \left(P_i^{min} - P_i\right) \right]\right|$$ .......... $$(5)$$
where $$d_i$$ and $$e_i$$ are the coefficients of the valve-point loading effects. Thus, Table 3 is expanded to Table 4.
$$\bullet$$ The valve-point loading effects can be relaxed if either $$d$$ or $$e$$ of all units are set to zero.
II. Files:
$$\bullet$$ System Data (Text Format) [Download]
III. References (Some selected papers that use this test system):
[1] F. N. Lee and A. M. Breipohl, “Reserve Constrained Economic Dispatch with Prohibited Operating Zones,” IEEE Trans. Power Syst., vol. 8, no. 1, pp. 246–254, 1993.
[2] Z.-L. Gaing, “Particle Swarm Optimization to Solving the Economic Dispatch Considering the Generator Constraints,” IEEE Trans. Power Syst., vol. 18, no. 3, pp. 1187–1195, Aug. 2003.
[3] L. dos S. Coelho and V. C. Mariani, “Improved Differential Evolution Algorithms for Handling Economic Dispatch Optimization with Generator Constraints,” Energy Convers. Manag., vol. 48, no. 5, pp. 1631–1639, Jan. 2007.
[4] K. T. Chaturvedi, M. Pandit, and L. Srivastava, “Self-Organizing Hierarchical Particle Swarm Optimization for Nonconvex Economic Dispatch,” IEEE Trans. Power Syst., vol. 23, no. 3, pp. 1079–1087, Aug. 2008.
[5] C. C. Kuo, “A Novel Coding Scheme for Practical Economic Dispatch by Modified Particle Swarm Approach,” IEEE Trans. Power Syst., vol. 23, no. 4, pp. 1825–1835, Nov. 2008.
[6] G. Shabib, M. A. Gayed, and A. M. Rashwan, “Modified Particle Swarm Optimization for Economic Load Dispatch with Valve-Point Effects and Transmission Losses,” Curr. Dev. Artif. Intell., vol. 2, no. 1, pp. 39–49, 2011.
[7] M. I. Abouheaf, S. Haesaert, W. Lee, and F. L. Lewis, “Q-Learning with Eligibility Traces to Solve Non-Convex Economic Dispatch Problems,” Int. J. Electr. Robot. Electron. Commun. Eng., vol. 6, no. 7, pp. 41–48, 2012.
[8] A. Nazari and A. Hadidi, “Biogeography Based Optimization Algorithm for Economic Load Dispatch of Power System,” Am. J. Adv. Sci. Res., vol. 1, no. 3, pp. 99–105, Sep. 2012.
[9] G. Xiong, D. Shi, and X. Duan, “Multi-Strategy Ensemble Biogeography-Based Optimization for Economic Dispatch Problems,” Appl. Energy, vol. 111, pp. 801–811, Jun. 2013.
[10] K. Zare and T. G. Bolandi, “Modified Iteration Particle Swarm Optimization Procedure for Economic Dispatch Solving with Non-Smooth and Non-Convex Fuel Cost Function,” in 3rd IET International Conference on Clean Energy and Technology (CEAT) 2014, 2014, pp. 1–6.
[11] Hardiansyah, “Modified Differential Evolution Algorithm for Economic Load Dispatch Problem with Valve-Point Effects,” Int. J. Adv. Res. Electr. Electron. Instrum. Eng., vol. 3, no. 11, pp. 13400–13409, Nov. 2014.
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http://en.wikipedia.org/wiki/Parralax
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# Parallax
(Redirected from Parralax)
For other uses, see Parallax (disambiguation).
A simplified illustration of the parallax of an object against a distant background due to a perspective shift. When viewed from "Viewpoint A", the object appears to be in front of the blue square. When the viewpoint is changed to "Viewpoint B", the object appears to have moved in front of the red square.
This animation is an example of parallax. As the viewpoint moves side to side, the objects in the distance appear to move slower than the objects close to the camera.
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.[1][2] The term is derived from the Greek παράλλαξις (parallaxis), meaning "alteration". Nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances.
Astronomers use the principle of parallax to measure distances to the closer stars. Here, the term "parallax" is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the sun in its orbit.[3] These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder.
Parallax also affects optical instruments such as rifle scopes, binoculars, microscopes, and twin-lens reflex cameras that view objects from slightly different angles. Many animals, including humans, have two eyes with overlapping visual fields that use parallax to gain depth perception; this process is known as stereopsis. In computer vision the effect is used for computer stereo vision, and there is a device called a parallax rangefinder that uses it to find range, and in some variations also altitude to a target.
A simple everyday example of parallax can be seen in the dashboard of motor vehicles that use a needle-style speedometer gauge. When viewed from directly in front, the speed may show exactly 60; but when viewed from the passenger seat the needle may appear to show a slightly different speed, due to the angle of viewing.
## Visual perception
This image demonstrates parallax. The Sun is visible above the streetlight. The reflection in the water is a virtual image of the Sun and the streetlight. The location of the virtual image is below the surface of the water, offering a different vantage point of the streetlight, which appears to be shifted relative to the more distant Sun.
As the eyes of humans and other animals are in different positions on the head, they present different views simultaneously. This is the basis of stereopsis, the process by which the brain exploits the parallax due to the different views from the eye to gain depth perception and estimate distances to objects.[4] Animals also use motion parallax, in which the animals (or just the head) move to gain different viewpoints. For example, pigeons (whose eyes do not have overlapping fields of view and thus cannot use stereopsis) bob their heads up and down to see depth.[5]
The motion parallax is exploited also in wiggle stereoscopy, computer graphics which provide depth cues through viewpoint-shifting animation rather than through binocular vision.
## Parallax in astronomy
Parallax is an angle subtended by a line on a point. In the upper diagram the earth in its orbit sweeps the parallax angle subtended on the sun. The lower diagram shows an equal angle swept by the sun in a geostatic model. A similar diagram can be drawn for a star except that the angle of parallax would be minuscule.
Parallax arises due to change in viewpoint occurring due to motion of the observer, of the observed, or of both. What is essential is relative motion. By observing parallax, measuring angles, and using geometry, one can determine distance.
### Stellar parallax
Main article: Stellar parallax
Stellar parallax created by the relative motion between the Earth and a star can be seen, in the Copernican model, as arising from the orbit of the Earth around the Sun: the star only appears to move relative to more distant objects in the sky. In a geostatic model, the movement of the star would have to be taken as real with the star oscillating across the sky with respect to the background stars.
Stellar parallax is most often measured using annual parallax, defined as the difference in position of a star as seen from the Earth and Sun, i. e. the angle subtended at a star by the mean radius of the Earth's orbit around the Sun. The parsec (3.26 light-years) is defined as the distance for which the annual parallax is 1 arcsecond. Annual parallax is normally measured by observing the position of a star at different times of the year as the Earth moves through its orbit. Measurement of annual parallax was the first reliable way to determine the distances to the closest stars. The first successful measurements of stellar parallax were made by Friedrich Bessel in 1838 for the star 61 Cygni using a heliometer.[6] Stellar parallax remains the standard for calibrating other measurement methods. Accurate calculations of distance based on stellar parallax require a measurement of the distance from the Earth to the Sun, now based on radar reflection off the surfaces of planets.[7]
The angles involved in these calculations are very small and thus difficult to measure. The nearest star to the Sun (and thus the star with the largest parallax), Proxima Centauri, has a parallax of 0.7687 ± 0.0003 arcsec.[8] This angle is approximately that subtended by an object 2 centimeters in diameter located 5.3 kilometers away.
Hubble Space Telescope - Spatial scanning precisely measures distances up to 10,000 light-years away (10 April 2014).[9]
The fact that stellar parallax was so small that it was unobservable at the time was used as the main scientific argument against heliocentrism during the early modern age. It is clear from Euclid's geometry that the effect would be undetectable if the stars were far enough away, but for various reasons such gigantic distances involved seemed entirely implausible: it was one of Tycho's principal objections to Copernican heliocentrism that in order for it to be compatible with the lack of observable stellar parallax, there would have to be an enormous and unlikely void between the orbit of Saturn and the eighth sphere (the fixed stars).[10]
In 1989, the satellite Hipparcos was launched primarily for obtaining improved parallaxes and proper motions for over 100,000 nearby stars, increasing the reach of the method tenfold. Even so, Hipparcos is only able to measure parallax angles for stars up to about 1,600 light-years away, a little more than one percent of the diameter of the Milky Way Galaxy. The European Space Agency's Gaia mission, launched in December 2013, will be able to measure parallax angles to an accuracy of 10 microarcseconds, thus mapping nearby stars (and potentially planets) up to a distance of tens of thousands of light-years from Earth.[11][12] In April 2014, NASA astronomers reported that the Hubble Space Telescope, by using spatial scanning, can now precisely measure distances up to 10,000 light-years away, a ten-fold improvement over earlier measurements.[9] (related image)
### Distance measurement
Main article: Distance measurement
Distance measurement by parallax is a special case of the principle of triangulation, which states that one can solve for all the sides and angles in a network of triangles if, in addition to all the angles in the network, the length of at least one side has been measured. Thus, the careful measurement of the length of one baseline can fix the scale of an entire triangulation network. In parallax, the triangle is extremely long and narrow, and by measuring both its shortest side (the motion of the observer) and the small top angle (always less than 1 arcsecond,[6] leaving the other two close to 90 degrees), the length of the long sides (in practice considered to be equal) can be determined.
Assuming the angle is small (see derivation below), the distance to an object (measured in parsecs) is the reciprocal of the parallax (measured in arcseconds): $d (\mathrm{pc}) = 1 / p (\mathrm{arcsec}).$ For example, the distance to Proxima Centauri is 1/0.7687=1.3009 parsecs (4.243 ly).[8]
### Diurnal parallax
Diurnal parallax is a parallax that varies with rotation of the Earth or with difference of location on the Earth. The Moon and to a smaller extent the terrestrial planets or asteroids seen from different viewing positions on the Earth (at one given moment) can appear differently placed against the background of fixed stars.[13][14]
### Lunar parallax
Lunar parallax (often short for lunar horizontal parallax or lunar equatorial horizontal parallax), is a special case of (diurnal) parallax: the Moon, being the nearest celestial body, has by far the largest maximum parallax of any celestial body, it can exceed 1 degree.[15]
The diagram (above) for stellar parallax can illustrate lunar parallax as well, if the diagram is taken to be scaled right down and slightly modified. Instead of 'near star', read 'Moon', and instead of taking the circle at the bottom of the diagram to represent the size of the Earth's orbit around the Sun, take it to be the size of the Earth's globe, and of a circle around the Earth's surface. Then, the lunar (horizontal) parallax amounts to the difference in angular position, relative to the background of distant stars, of the Moon as seen from two different viewing positions on the Earth: one of the viewing positions is the place from which the Moon can be seen directly overhead at a given moment (that is, viewed along the vertical line in the diagram); and the other viewing position is a place from which the Moon can be seen on the horizon at the same moment (that is, viewed along one of the diagonal lines, from an Earth-surface position corresponding roughly to one of the blue dots on the modified diagram).
The lunar (horizontal) parallax can alternatively be defined as the angle subtended at the distance of the Moon by the radius of the Earth[16]—equal to angle p in the diagram when scaled-down and modified as mentioned above.
The lunar horizontal parallax at any time depends on the linear distance of the Moon from the Earth. The Earth-Moon linear distance varies continuously as the Moon follows its perturbed and approximately elliptical orbit around the Earth. The range of the variation in linear distance is from about 56 to 63.7 earth-radii, corresponding to horizontal parallax of about a degree of arc, but ranging from about 61.4' to about 54'.[15] The Astronomical Almanac and similar publications tabulate the lunar horizontal parallax and/or the linear distance of the Moon from the Earth on a periodical e.g. daily basis for the convenience of astronomers (and formerly, of navigators), and the study of the way in which this coordinate varies with time forms part of lunar theory.
Diagram of daily lunar parallax
Parallax can also be used to determine the distance to the Moon.
One way to determine the lunar parallax from one location is by using a lunar eclipse. A full shadow of the Earth on the Moon has an apparent radius of curvature equal to the difference between the apparent radii of the Earth and the Sun as seen from the Moon. This radius can be seen to be equal to 0.75 degree, from which (with the solar apparent radius 0.25 degree) we get an Earth apparent radius of 1 degree. This yields for the Earth-Moon distance 60.27 Earth radii or 384,399 kilometres (238,854 mi) This procedure was first used by Aristarchus of Samos[17] and Hipparchus, and later found its way into the work of Ptolemy.[18] The diagram at right shows how daily lunar parallax arises on the geocentric and geostatic planetary model in which the Earth is at the centre of the planetary system and does not rotate. It also illustrates the important point that parallax need not be caused by any motion of the observer, contrary to some definitions of parallax that say it is, but may arise purely from motion of the observed.
Another method is to take two pictures of the Moon at exactly the same time from two locations on Earth and compare the positions of the Moon relative to the stars. Using the orientation of the Earth, those two position measurements, and the distance between the two locations on the Earth, the distance to the Moon can be triangulated:
$\mathrm{distance}_{\textrm{moon}} = \frac {\mathrm{distance}_{\mathrm{observerbase}}} {\tan (\mathrm{angle})}$
Example of lunar parallax: Occultation of Pleiades by the Moon
This is the method referred to by Jules Verne in From the Earth to the Moon:
Until then, many people had no idea how one could calculate the distance separating the Moon from the Earth. The circumstance was exploited to teach them that this distance was obtained by measuring the parallax of the Moon. If the word parallax appeared to amaze them, they were told that it was the angle subtended by two straight lines running from both ends of the Earth's radius to the Moon. If they had doubts on the perfection of this method, they were immediately shown that not only did this mean distance amount to a whole two hundred thirty-four thousand three hundred and forty-seven miles (94,330 leagues), but also that the astronomers were not in error by more than seventy miles (≈ 30 leagues).
### Solar parallax
After Copernicus proposed his heliocentric system, with the Earth in revolution around the Sun, it was possible to build a model of the whole solar system without scale. To ascertain the scale, it is necessary only to measure one distance within the solar system, e.g., the mean distance from the Earth to the Sun (now called an astronomical unit, or AU). When found by triangulation, this is referred to as the solar parallax, the difference in position of the Sun as seen from the Earth's centre and a point one Earth radius away, i. e., the angle subtended at the Sun by the Earth's mean radius. Knowing the solar parallax and the mean Earth radius allows one to calculate the AU, the first, small step on the long road of establishing the size and expansion age[19] of the visible Universe.
A primitive way to determine the distance to the Sun in terms of the distance to the Moon was already proposed by Aristarchus of Samos in his book On the Sizes and Distances of the Sun and Moon. He noted that the Sun, Moon, and Earth form a right triangle (right angle at the Moon) at the moment of first or last quarter moon. He then estimated that the Moon, Earth, Sun angle was 87°. Using correct geometry but inaccurate observational data, Aristarchus concluded that the Sun was slightly less than 20 times farther away than the Moon. The true value of this angle is close to 89° 50', and the Sun is actually about 390 times farther away.[17] He pointed out that the Moon and Sun have nearly equal apparent angular sizes and therefore their diameters must be in proportion to their distances from Earth. He thus concluded that the Sun was around 20 times larger than the Moon; this conclusion, although incorrect, follows logically from his incorrect data. It does suggest that the Sun is clearly larger than the Earth, which could be taken to support the heliocentric model.[20]
Measuring Venus transit times to determine solar parallax
Although Aristarchus' results were incorrect due to observational errors, they were based on correct geometric principles of parallax, and became the basis for estimates of the size of the solar system for almost 2000 years, until the transit of Venus was correctly observed in 1761 and 1769.[17] This method was proposed by Edmond Halley in 1716, although he did not live to see the results. The use of Venus transits was less successful than had been hoped due to the black drop effect, but the resulting estimate, 153 million kilometers, is just 2% above the currently accepted value, 149.6 million kilometers.
Much later, the Solar System was 'scaled' using the parallax of asteroids, some of which, such as Eros, pass much closer to Earth than Venus. In a favourable opposition, Eros can approach the Earth to within 22 million kilometres.[21] Both the opposition of 1901 and that of 1930/1931 were used for this purpose, the calculations of the latter determination being completed by Astronomer Royal Sir Harold Spencer Jones.[22]
Also radar reflections, both off Venus (1958) and off asteroids, like Icarus, have been used for solar parallax determination. Today, use of spacecraft telemetry links has solved this old problem. The currently accepted value of solar parallax is 8".794 143.[23]
### Dynamic or moving-cluster parallax
Main article: Moving cluster method
The open stellar cluster Hyades in Taurus extends over such a large part of the sky, 20 degrees, that the proper motions as derived from astrometry appear to converge with some precision to a perspective point north of Orion. Combining the observed apparent (angular) proper motion in seconds of arc with the also observed true (absolute) receding motion as witnessed by the Doppler redshift of the stellar spectral lines, allows estimation of the distance to the cluster (151 light-years) and its member stars in much the same way as using annual parallax.[24]
Dynamic parallax has sometimes also been used to determine the distance to a supernova, when the optical wave front of the outburst is seen to propagate through the surrounding dust clouds at an apparent angular velocity, while its true propagation velocity is known to be the speed of light.[25]
### Derivation
For a right triangle,
$\sin p = \frac {1 AU} {d} ,$
where $p$ is the parallax, 1 AU (149,600,000 km) is approximately the average distance from the Sun to Earth, and $d$ is the distance to the star. Using small-angle approximations (valid when the angle is small compared to 1 radian),
$\sin x \approx x\textrm{\ radians} = x \cdot \frac {180} {\pi} \textrm{\ degrees} = x \cdot 180 \cdot \frac {3600} {\pi} \textrm{\ arcseconds} ,$
so the parallax, measured in arcseconds, is
$p'' \approx \frac {1 \textrm{\ AU}} {d} \cdot 180 \cdot \frac{3600} {\pi} .$
If the parallax is 1", then the distance is
$d = 1 \textrm{\ AU} \cdot 180 \cdot \frac {3600} {\pi} \approx 206,265 \textrm{\ AU} \approx 3.2616 \textrm{\ ly} \equiv 1 \textrm{\ parsec} .$
This defines the parsec, a convenient unit for measuring distance using parallax. Therefore, the distance, measured in parsecs, is simply $d = 1 / p$, when the parallax is given in arcseconds.[26]
### Parallax error in astronomy
Precise parallax measurements of distance have an associated error. However this error in the measured parallax angle does not translate directly into an error for the distance, except for relatively small errors. The reason for this is that an error toward a smaller angle results in a greater error in distance than an error toward a larger angle.
However, an approximation of the distance error can be computed by
$\delta d = \delta \left( {1 \over p} \right) =\left| {\partial \over \partial p} \left( {1 \over p} \right) \right| \delta p ={\delta p \over p^2}$
where d is the distance and p is the parallax. The approximation is far more accurate for parallax errors that are small relative to the parallax than for relatively large errors. For meaningful results in stellar astronomy, Dutch astronomer Floor van Leeuwen recommends that the parallax error be no more than 10% of the total parallax when computing this error estimate.[27]
## Parallax error in measurement instruments
The correct line of sight needs to be used to avoid parallax error.
Measurements made by viewing the position of some marker relative to something to be measured are subject to parallax error if the marker is some distance away from the object of measurement and not viewed from the correct position. For example, if measuring the distance between two ticks on a line with a ruler marked on its top surface, the thickness of the ruler will separate its markings from the ticks. If viewed from a position not exactly perpendicular to the ruler, the apparent position will shift and the reading will be less accurate than the ruler is capable of.
A similar error occurs when reading the position of a pointer against a scale in an instrument such as an analog multimeter. To help the user avoid this problem, the scale is sometimes printed above a narrow strip of mirror, and the user's eye is positioned so that the pointer obscures its own reflection, guaranteeing that the user's line of sight is perpendicular to the mirror and therefore to the scale. The same effect alters the speed read on a car's speedometer by a driver in front of it and a passenger off to the side, values read from a graticule not in actual contact with the display on an oscilloscope, etc.
## Photogrammetric parallax
Aerial picture pairs, when viewed through a stereo viewer, offer a pronounced stereo effect of landscape and buildings. High buildings appear to 'keel over' in the direction away from the centre of the photograph. Measurements of this parallax are used to deduce the height of the buildings, provided that flying height and baseline distances are known. This is a key component to the process of photogrammetry.
## Parallax error in photography
Contax III rangefinder camera with macro photography setting. Because the viewfinder is on top of the lens and of the close proximity of the subject, goggles are fitted in front of the rangefinder and a dedicated viewfinder installed to compensate for parallax.
Parallax error can be seen when taking photos with many types of cameras, such as twin-lens reflex cameras and those including viewfinders (such as rangefinder cameras). In such cameras, the eye sees the subject through different optics (the viewfinder, or a second lens) than the one through which the photo is taken. As the viewfinder is often found above the lens of the camera, photos with parallax error are often slightly lower than intended, the classic example being the image of person with his or her head cropped off. This problem is addressed in single-lens reflex cameras, in which the viewfinder sees through the same lens through which the photo is taken (with the aid of a movable mirror), thus avoiding parallax error.
Parallax is also an issue in image stitching, such as for panoramas.
## Parallax in sights
Parallax affects sights in many ways. On sights fitted to small arms, bows in archery, etc. the distance between the sighting mechanism and the weapon's bore or axis can introduce significant errors when firing at close range, particularly when firing at small targets. This difference is generally referred to as "sight height"[28] and is compensated for (when needed) via calculations that also take in other variables such as bullet drop, windage, and the distance at which the target is expected to be.[29] Sight height can be used to advantage when "sighting-in" rifles for field use. A typical hunting rifle (.222 with telescopic sights) sighted-in at 75m will be useful from 50m to 200m without further adjustment.[citation needed]
### Parallax in optical sights
In optical sights parallax refers to the apparent movement of the reticle in relationship to the target when the user moves his/her head laterally behind the sight (up/down or left/right),[30] i.e. it is an error where the reticle does not stay aligned with the sight's own optical axis.
In optical instruments such as telescopes, microscopes, or in telescopic sights used on small arms and theodolites, the error occurs when the optics are not precisely focused: the reticle will appear to move with respect to the object focused on if one moves one's head sideways in front of the eyepiece. Some firearm telescopic sights are equipped with a parallax compensation mechanism which basically consists of a movable optical element that enables the optical system to project the picture of objects at varying distances and the reticle crosshairs pictures together in exactly the same optical plane. Telescopic sights may have no parallax compensation because they can perform very acceptably without refinement for parallax with the sight being permanently adjusted for the distance that best suits their intended usage. Typical standard factory parallax adjustment distances for hunting telescopic sights are 100 yd or 100 m to make them suited for hunting shots that rarely exceed 300 yd/m. Some target and military style telescopic sights without parallax compensation may be adjusted to be parallax free at ranges up to 300 yd/m to make them better suited for aiming at longer ranges.[citation needed] Scopes for rimfires, shotguns, and muzzleloaders will have shorter parallax settings, commonly 50 yd/m[citation needed] for rimfire scopes and 100 yd/m[citation needed] for shotguns and muzzleloaders. Scopes for airguns are very often found with adjustable parallax, usually in the form of an adjustable objective, or AO. These may adjust down as far as 3 yards (2.74 m).[citation needed]
Non-magnifying reflector or "reflex" sights have the ability to be theoretically "parallax free." But since these sights use parallel collimated light this is only true when the target is at infinity. At finite distances eye movement perpendicular to the device will cause parallax movement in the reticle image in exact relationship to eye position in the cylindrical column of light created by the collimating optics.[31][32] Firearm sights, such as some red dot sights, try to correct for this via not focusing the reticle at infinity, but instead at some finite distance, a designed target range where the reticle will show very little movement due to parallax.[31] Some manufactures market reflector sight models they call "parallax free,"[33] but this refers to an optical system that compensates for off axis spherical aberration, an optical error induced by the spherical mirror used in the sight that can cause the reticle position to diverge off the sight's optical axis with change in eye position.[34][35]
## Artillery gunfire
Because of the positioning of field or naval artillery guns, each one has a slightly different perspective of the target relative to the location of the fire-control system itself. Therefore, when aiming its guns at the target, the fire control system must compensate for parallax in order to assure that fire from each gun converges on the target.
## Parallax rangefinders
Parallax theory for finding naval distances
A coincidence rangefinder or parallax rangefinder can be used to find distance to a target.
## As a metaphor
In a philosophic/geometric sense: an apparent change in the direction of an object, caused by a change in observational position that provides a new line of sight. The apparent displacement, or difference of position, of an object, as seen from two different stations, or points of view. In contemporary writing parallax can also be the same story, or a similar story from approximately the same time line, from one book told from a different perspective in another book. The word and concept feature prominently in James Joyce's 1922 novel, Ulysses. Orson Scott Card also used the term when referring to Ender's Shadow as compared to Ender's Game.
The metaphor is invoked by Slovenian philosopher Slavoj Žižek in his work The Parallax View. Žižek borrowed the concept of "parallax view" from the Japanese philosopher and literary critic Kojin Karatani. "The philosophical twist to be added (to parallax), of course, is that the observed distance is not simply subjective, since the same object that exists 'out there' is seen from two different stances, or points of view. It is rather that, as Hegel would have put it, subject and object are inherently mediated so that an 'epistemological' shift in the subject's point of view always reflects an ontological shift in the object itself. Or—to put it in Lacanese—the subject's gaze is always-already inscribed into the perceived object itself, in the guise of its 'blind spot,' that which is 'in the object more than object itself', the point from which the object itself returns the gaze. Sure the picture is in my eye, but I am also in the picture."[36]
## Notes
1. ^ Shorter Oxford English Dictionary. 1968. "Mutual inclination of two lines meeting in an angle"
2. ^ "Parallax". Oxford English Dictionary (Second Edition ed.). 1989. "Astron. Apparent displacement, or difference in the apparent position, of an object, caused by actual change (or difference) of position of the point of observation; spec. the angular amount of such displacement or difference of position, being the angle contained between the two straight lines drawn to the object from the two different points of view, and constituting a measure of the distance of the object."
3. ^ In the past diurnal parallax was also used to measure distances to celestial objects within the solar system. This method has now been superseded by more accurate techniques.
4. ^ Steinman, Scott B.; Garzia, Ralph Philip (2000). Foundations of Binocular Vision: A Clinical perspective. McGraw-Hill Professional. pp. 2–5. ISBN 0-8385-2670-5.
5. ^ Steinman & Garzia 2000, p. 180.
6. ^ a b Zeilik & Gregory 1998, p. 44.
7. ^ Zeilik & Gregory 1998, § 22-3.
8. ^ a b Benedict, G. Fritz et al. (1999). "Interferometric Astrometry of Proxima Centauri and Barnard's Star Using HUBBLE SPACE TELESCOPE Fine Guidance Sensor 3: Detection Limits for Substellar Companions". The Astronomical Journal 118 (2): 1086–1100. arXiv:astro-ph/9905318. Bibcode:1999astro.ph..5318B. doi:10.1086/300975.
9. ^ a b Harrington, J.D.; Villard, Ray (10 April 2014). "NASA's Hubble Extends Stellar Tape Measure 10 Times Farther Into Space". NASA. Retrieved 11 April 2014.
10. ^ See p.51 in The reception of Copernicus' heliocentric theory: proceedings of a symposium organized by the Nicolas Copernicus Committee of the International Union of the History and Philosophy of Science, Torun, Poland, 1973, ed. Jerzy Dobrzycki, International Union of the History and Philosophy of Science. Nicolas Copernicus Committee; ISBN 90-277-0311-6, ISBN 978-90-277-0311-8
11. ^ "Soyuz ST-B successfully launches Gaia space observatory". nasaspaceflight.com. 19 December 2013. Retrieved 19 December 2013.
12. ^ Henney, Paul J. "ESA's Gaia Mission to study stars". Astronomy Today. Retrieved 2008-03-08.
13. ^ Seidelmann, P. Kenneth (2005). Explanatory Supplement to the Astronomical Almanac. University Science Books. pp. 123–125. ISBN 1-891389-45-9.
14. ^ Barbieri, Cesare (2007). Fundamentals of astronomy. CRC Press. pp. 132–135. ISBN 0-7503-0886-9.
15. ^ a b Astronomical Almanac e.g. for 1981, section D
16. ^ Astronomical Almanac, e.g. for 1981: see Glossary; for formulae see Explanatory Supplement to the Astronomical Almanac, 1992, p.400
17. ^ a b c Gutzwiller, Martin C. (1998). "Moon-Earth-Sun: The oldest three-body problem". Reviews of Modern Physics 70 (2): 589. Bibcode:1998RvMP...70..589G. doi:10.1103/RevModPhys.70.589.
18. ^ Webb, Stephen (1999), "3.2 Aristarchus, Hipparchus, and Ptolemy", Measuring the Universe: The Cosmological Distance Ladder, Springer, pp. 27–35, ISBN 9781852331061. See in particular p. 33: "Almost everything we know about Hipparchus comes down to us by way of Ptolemy."
19. ^ Freedman, W.L. (2000). "The Hubble constant and the expansion age of the Universe". Physics Reports 333 (1): 13. arXiv:astro-ph/9909076. Bibcode:2000PhR...333...13F. doi:10.1016/S0370-1573(00)00013-2.
20. ^ Al-Khalili, Jim (2010), Pathfinders: The Golden Age of Arabic Science, Penguin UK, p. 270, ISBN 9780141965017, "Some have suggested that his calculation of the relative size of the earth and sun led Aristarchus to conclude that it made more sense for the earth to be moving around the much larger sun than the other way round."
21. ^ Whipple 2007, p. 47.
22. ^ Whipple 2007, p. 117.
23. ^ US Naval Observatory, Astronomical Constants
24. ^ Vijay K. Narayanan; Andrew Gould (1999). "A Precision Test of Hipparcos Systematics toward the Hyades". The Astrophysical Journal 515 (1): 256. arXiv:astro-ph/9808284. Bibcode:1999ApJ...515..256N. doi:10.1086/307021.
25. ^ Panagia, N.; Gilmozzi, R.; MacChetto, F.; Adorf, H.-M.; Kirshner, R. P. (1991). "Properties of the SN 1987A circumstellar ring and the distance to the Large Magellanic Cloud". The Astrophysical Journal 380: L23. Bibcode:1991ApJ...380L..23P. doi:10.1086/186164.
26. ^ Similar derivations are in most astronomy textbooks. See, e. g., Zeilik & Gregory 1998, § 11-1.
27. ^ van Leeuwen, Floor (2007). Hipparcos, the new reduction of the raw data. Astrophysics and space science library 350. Springer. p. 86. ISBN 1-4020-6341-5.
28. ^ Dexadine, Ballistic Explorer, Sight Height
29. ^ crossbowmen.com, Crossbow Arrow & Bolts, Trajectories
30. ^ Setting Up An Air Rifle And Telescopic Sight For Field Target - An Instruction Manual For Beginners, page 16
31. ^ a b Encyclopedia of Bullseye Pistol
32. ^ American rifleman: Volume 93, National Rifle Association of America - THE REFLECTOR SIGHT By JOHN B. BUTLER, page 31
33. ^ Aimpoint's parallax-free, double lens system... AFMO.com
34. ^ ar15.com, How Aimpoints, EOTechs, And Other Parallax-Free Optics Work
35. ^ Gunsight - Patent 5901452 - general description of a mangin mirror system
36. ^ Žižek, Slavoj (2006). The Parallax View. The MIT Press. p. 17. ISBN 0-262-24051-3.
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https://ajayshahblog.blogspot.com/2007/05/humility-in-making-statements-about.html
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Wednesday, May 16, 2007
Humility in making statements about equilibrium exchange rates
In discussions about the rupee, many people are offering views about overvaluation (or lack thereof). In a recent piece on the subject [link], I said :
The present state of economic science does not permit such confident statements. REER calculations are extremely imprecise and have little content in explaining key relationships - as the above example shows.
Menzie Chinn has a blog posting on this subject. I found it particularly amusing that the two numerical values about the Indian rupee on this page were +12.1 and -14.7. In other words, we just don't know.
Please note: LaTeX mathematics works. This means that if you want to say $10 you have to say \$10.
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https://www.physicsforums.com/threads/lightly-damped-harmonic-oscillator.79617/
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# Lightly Damped Harmonic Oscillator
1. Jun 19, 2005
### e(ho0n3
Question:
(a) Show that the total mechanical energy of a lightly damped harmonic oscillator is
$$E = E_0 e^{-bt/m}$$
where $E_0$ is the total mechanical energy at t = 0.
(b) Show that the fractional energy lost per period is
$$\frac{\Delta E}{E} = \frac{2 \pi b}{m \omega_0} = \frac{2 \pi}{Q}$$
where $\omega_0 = \sqrt{k/m}$ and $Q = m \omega_0 / b$ is called the quality factor or Q value of the system. A larger Q value means the system can undergo oscillations for a longer time.
(a) When the velocity of the oscillator is 0, the total mechanical energy is purely potential energy, $U = 1/2kx^2$. Since I know that $x = Ae^{-bt/(2m)}\cos{\omega't}$ where t is some multiple of $2\pi/\omega'$, then
$$E = \frac{1}{2}kA^2e^{-bt/m}$$
and $E_0 = 1/2kA^2$. Of course, this is only valid when the velocity of the oscillator is 0, but since it is lightly damped the total mechanical energy should be approximately the same when the velocity is > 0. Right?
(b) Using some calculus, I can timidly state that
$$\frac{\Delta E}{\Delta t} \approx \frac{dE}{dt} = -\frac{E_0b}{m}e^{bt/m}$$
and since $\Delta t = 2\pi / \omega'$ then
$$\frac{\Delta E}{E} = -\frac{b\Delta t}{m} = -\frac{2\pi b}{m\omega'}$$
Since the oscillator is lightly damped, $\omega' \approx \omega_0$. However the result I get is negative. Should it be negative?
2. Jun 19, 2005
### OlderDan
Yes, it should be negative because you calculated the rate of change of energy, which is decreasing with time. The question asked for the fractional energy loss, which is the absolute value of the energy change.
Your calculation of the times at which the energy is all potential is overlooking the fact that the peaks in x do not correspond to the points where the cosine has value 1 because the exponential is also time dependent. However, the times between peaks still satisfy the condition you used, so the result follows subject to the other approximations you made.
Similar Discussions: Lightly Damped Harmonic Oscillator
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https://www.illustrativemathematics.org/content-standards/4/G/A/3/tasks/1060
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Update all PDFs
# Lines of symmetry for circles
Alignments to Content Standards: 4.G.A.3
Mr. Watkins asked his students to draw a line of symmetry for a circle with center $O$ pictured below:
1. Lisa drew the picture below. Is Lisa correct?
3. How many lines of symmetry does a circle have? Explain.
4. Explain why each line of symmetry divides the circle in half.
5. Explain why each line of symmetry for the circle must go through the center.
## IM Commentary
A circle has an infinite number of symmetries. This contrasts with polygons such as the triangles and quadrilaterals considered in 4.G Lines of symmetry for triangles and 4.G Lines of symmetry for quadrilaterals. The circle is, in some sense, the most symmetric two dimensional figure and it is partly for this reason that it is so familiar. Coins, clock faces, wheels, the image of the full moon in the sky: these are all examples of circles which we encounter on a regular basis.
This is an instructional task that gives students a chance to reason about lines of symmetry and discover that a circle has an an infinite number of lines of symmetry. Even though the concept of an infinite number of lines is fairly abstract, fourth graders can understand infinity in an informal way. Just as there is always a fraction between any two fractions on the number line, there is always another line through the center of the circle "between" any two lines through the center of the circle. So if you identify a certain number of lines, you can argue that there is always at least one more.
• The algebraic perspective, using the equation that defines a circle, and
• The geometric perspective, using the definition of reflections in terms of perpendicular lines.
This task includes an experimental GeoGebra worksheet, with the intent that instructors might use it to more interactively demonstrate the relevant content material. The file should be considered a draft version, and feedback on it in the comment section is highly encouraged, both in terms of suggestions for improvement and for ideas on using it effectively. The file can be run via the free online application GeoGebra, or run locally if GeoGebra has been installed on a computer.
## Attached Resources
• 1060 GeoGebra File
• ## Solution
1. Lisa is correct. If we fold the circle over the line she has drawn then the parts of the circle on each side of the line match up.
2. Brad is also correct. If we fold the circle over the line he has drawn then the parts of the circle on each side of the line match up.
3. If we fold the circle over any line through the center $O$, then the parts of the circle on each side of the line will match up. One way to create such a line is to pick a point on the top half of the circle and draw the line through that point and the center $O$. Just like there are an infinite number of points on a line (if you pick any two points, there is always another one in between them) there are an infinite number of points on the top half of the circle. Each of these points can be used to draw a line of symmetry. Since there are an infinite number of lines through the center, the circle has an infinite number of lines of symmetry.
4. When the circle is folded over a line of symmetry, the parts of the circle on each side of the line match up. This means that the parts of the circle on each side of the line must have the same area. So a line of symmetry divides the circle into two parts with equal area.
5. A line of symmetry for the circle must cut the circle into two parts with equal area. Below is a picture of two lines not containing $O$:
Note that in each case, for a line $L$ through the circle that does not contain the center $O$, the part of the circle on the side of $L$ that contains $O$ is larger than the part of the circle on the side of $L$ which does not contain $O$. Hence these lines cannot be lines of symmetry as any line of symmetry would cut the circle in half.
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https://epjc.epj.org/articles/epjc/abs/2002/07/100520323/100520323.html
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2018 Impact factor 4.843
Particles and Fields
Eur. Phys. J. C 24, 323-329 (2002)
DOI: 10.1007/s100520200951
## Borel convergence of the variationally improved mass expansion and dynamical symmetry breaking
J.-L. Kneur and D. Reynaud
Physique Mathématique et Théorique, UMR-5825-CNRS, Université Montpellier II, 34095 Montpellier Cedex 5, France
(Received: 25 February 2002 / Published online: 8 May 2002 - © Springer-Verlag / Società Italiana di Fisica 2002 )
Abstract
A modification of perturbation theory, known as the delta expansion (variationally improved perturbation), gave rigorously convergent series in some D=1 models (oscillator energy levels) with factorially divergent ordinary perturbative expansions. In a generalization of the variationally improved perturbation technique appropriate to renormalizable asymptotically free theories, we show that the large expansion orders of certain physical quantities are similarly improved, and prove the Borel convergence of the corresponding series for , with mv the new (arbitrary) mass perturbation parameter. We argue that non-ambiguous estimates of quantities relevant to dynamical (chiral) symmetry breaking in QCD are possible in this resummation framework.
© Società Italiana di Fisica, Springer-Verlag 2002
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https://www.quantumdiaries.org/2011/07/22/the-birds-and-the-bs/
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## View Blog | Read Bio
### The Birds and the Bs
`Yesterday marked the beginning of the HEP summer conference season with EPS-HEP 2011, which is particularly exciting since the LHC now has enough luminosity (accumulated data) to start seeing hints of new physics. As Ken pointed out, the Tevatron’s new lower bound on the Bs → μμ decay rate seemed to be a harbinger of things to come (Experts can check out the official paper, the CDF public page, and the excellent summaries by Tommaso Dorigo and Jester.).
Somewhat unfortunately, the first LHCb results on this process do not confirm the CDF excess, though they are not yet mutually exclusive. Instead of delving too much into this particular result, I’d like to give some background to motivate why it’s interesting to those of us looking for new physics. This requires a lesson in “the birds and the Bs”—of course, by this I mean B mesons and the so-called ‘penguin’ diagrams.
## The Bs meson: why it’s special
It's a terrible pun, I know.
A Bs meson is a bound state of a bottom anti-quark and strange quark; it’s sort of like a “molecule” of quarks. There are all sorts of mesons that one could imagine by sticking together different quarks and anti-quarks, but the Bs meson and it’s lighter cousin, the Bd meson, are particularly interesting characters in the spectrum of all possible mesons.
The reason is that both the Bs and the Bd are neutral particles, and it turns out that they mix quantum mechanically with their antiparticles, which we call the Bs and Bd. This mixing is the exact same kind of flavor phenomenon that we described when we mentioned “Neapolitan” neutrinos and is analogous to the mixing of chiralities in a massive fermion. Recall that properties like “bottom-ness” or “strangeness” are referred to as flavor. Going from a Bs to a Bs changes the “number of bottom quarks” from -1 to +1 and the “number of strange quarks” from +1 to -1, so such effects are called flavor-changing.
To help clarify things, here’s an example diagram that encodes this quantum mixing:
The ui refers to any up-type quark.
Any neutral meson can mix—or “oscillate”—into its antiparticle, but the B mesons are special because of their lifetime. Recall that mesons are unstable and decay, so unlike neutrinos, we can’t just wait for a while to see if they oscillate into something interesting. Some mesons live for too long and their oscillation phenomena get ‘washed out’ before we get to observe them. Other mesons don’t live long enough and decay before they have a chance to oscillate at all. But B mesons—oh, wonderful Goldilocks B mesons—they have a lifetime and oscillation time that are roughly of the same magnitude. This means that by measuring their decays and relative decay rates we can learn about how these mesons mix, i.e. we can learn about the underlying flavor structure of the Standard Model.
Historical remark: The Bd meson is special for another reason: by a coincidence, we can produce them rather copiously. The reason is that the Bd meson mass just happens to be just under half of the mass of the Upsilon 4S particle, ϒ(4S), which just happens to decay into a BdBd pair. Thus, by the power of resonances, we can collide electrons and positrons to produce lots of upsilons, which then decay in to lots of B mesons. For the past decade flavor physics focused around these ‘B factories,’ mainly the BaBar detector at SLAC and Belle in Japan. BaBar has since been retired, while Belle is being upgraded to “Super Belle.” For the meanwhile, the current torch-bearer for B-physics is LHCb.
## The CDF and LHCb results: Bs → mu mu
It turns out that there are interesting flavor-changing effects even without considering meson mixing, but rather in the decay of the B meson itself. For example, we can modify the previous diagram to consider the decay of a Bs meson into a muon/anti-muon pair:
This is still a flavor-changing decay since the net strangeness (+1) and bottom-ness (-1) is not preserved; but note that the lepton flavor is conserved since the muon/anti-muon pair have no net muon number. (As an exercise: try drawing the other diagrams that contribute; the trick is that you need W bosons to change flavor.) You could also replace muons by electrons or taus, but those decays are much harder to detect experimentally. As a rule of thumb muons are really nice final state particles since they make it all the way through the detector and one has a decent shot at getting good momentum measurements.
It turns out that this decay is extremely rare. For the Bs meson, the Standard Model predicts a dimuon branching ratio of around 3 × 10-9, which means that a Bs will only decay into two muons 0.0000003% of the time… clearly in order to accurately measure the actual rate one needs to produce a lot of B mesons.
In fact, until recently, we simply did not have enough observed B meson decays to even estimate the true dimuon decay rate. The ‘B factories’ of the past decade were only able to put upper limits on this rate. In fact, this decay is one of the main motivations for LHCb, which was designed to be the first experiment that would be sensitive enough to probe the Standard Model decay rate. (This means that if the decay rate is at least at the Standard Model rate, then LHCb will see it.)
The exciting news from CDF last week was that—for the first time—they appeared to have been able to set a lower bound on the dimuon decay rate of the Bs meson. (The Bd meson has a smaller decay rate and CDF was unable to set a lower bound.) The lower bound is still statistically consistent with the Standard Model rate, but the suggested (‘central value’) rate was 1.8 × 10-8. If this is true, then it would be a fairly strong signal for new physics beyond the Standard Model. The 90% confidence level range from CDF is:
4.6 × 10-9 < BR(Bs → μ+μ) < 3.9 × 10-8.
Unfortunately, today’s new result from LHCb didn’t detect an excess with which it could set a lower bound and could only set a 90% confidence upper bound,
BR(Bs → μ+μ) < 1.3 × 10-8.
This goes down to 1.2 × 10-8 when including 2010 data. The bounds are not yet at odds with one another, but many people were hoping that LHCb would have been able to confirm the CDF excess in dimuon events. The analyses of the two experiments seem to be fairly similar, so there isn’t too much wiggle room to think that the different results just come from having different experiments.
More data will clarify the situation; LHCb should accumulate enough data to prove branching ratios down to the Standard Model prediction of 3 × 10-9. Unfortunately CDF will not be able to reach that sensitivity.
## New physics in loops
Now that we’re up to date with the experimental status of Bs → μμ, let’s figure out why it’s so interesting from a theoretical point of view. One thing you might have noticed from the “box” Feynman diagrams above is that they involve a closed loop. An interesting thing about closed loops in Feynman diagrams is that they can probe physics at much higher energies than one would naively expect.
The reason for this is that the particles running in the loop do not have their momenta fixed in terms of the momenta of the external particles. You can see this for yourself by assigning momenta (call them p1, p2, … , etc.) to each particle line and (following the usual Feynman rules) impose momentum conservation at each vertex. You’ll find that there is an unconstrained momentum that goes around the loop. Because this momentum is unspecified, the laws of quantum physics say that one must add together the contributions from all possible momenta. Thus it turns out that even though the Bs meson mass is around 5 GeV, the dimuon decay is sensitive to particles that are a hundred times heavier.
Note that unlike other processes where we study new physics by directly producing it and watching it decay, in low-energy loop diagrams one only intuits the presence of new particles through their virtual effects (quantum interference). I’ll leave the details for another time, but here are a few facts that you can assume for now:
1. Loop diagrams can be sensitive to new heavy particles through quantum interference.
2. Processes which only occur through loop diagrams are often suppressed. (This is partly why the Standard Model branching ratio for Bs → μμ is so small.)
3. In the Standard Model, all flavor-changing neutral currents (FCNC)—i.e. all flavor-changing processes whose intermediate states carry no net electric charge—only occur at loop level. (Recall that the electrically-charged W bosons can change flavor, but the electrically neutral Z bosons cannot. Similarly, note that there is no way to draw a Bs → μμ diagram in the Standard Model without including a loop.)
4. Thus, processes with a flavor-changing neutral current (such as Bs → μμ) are fruitful places to look for new physics effects that only show up at loop level. If there were a non-loop level (“tree level”) contribution from the Standard Model, then the loop-induced new physics effects would tend to be drowned out because they are only small corrections to the tree-level result. However, since there are no FCNCs in the Standard Model, the new physics contributions have a ‘fighting change’ at having a big effect relative to the Standard Model result.
5. Semi-technical remark, for experts: indeed, for Bs → μμ the Standard Model diagrams are additionally suppressed by a GIM suppression (as is the case for FCNCs) as well as helicity suppression (the B meson is a pseudoscalar, so the final states require a muon mass insertion).
So the punchline is that Bs → μμ is a really fertile place to hope to see some deviation from the Standard Model branching ratio due to new physics.
## Introducing the Penguin
I would be remiss if I didn’t mention the “penguin diagram” and its role in physics. You can learn about the penguin’s silly etymology in its Wikipedia article; suffice it for me to ‘wow’ you with a picture of an autographed paper from one of the penguin’s progenitors:
A copy of the original "penguin" paper, autographed by John Ellis.
The main idea is that penguin diagrams are flavor-changing loops that involve two fermions and a neutral gauge boson. For example, the b→s penguin takes the form (no, it doesn’t look much like a penguin)
You should have guessed that in the Standard Model, the wiggly line on top has to be a W boson in order for the fermion line to change flavors. The photon could also be a Z boson, a gluon, or even a Higgs boson. If we allow the boson to decay into a pair of muons, we obtain a diagram that contributes to Bs → μμ.
Some intuition for why the penguin takes this particular form: as mentioned above, any flavor-changing neutral transition in the Standard Model requires a loop. So we start by drawing a diagram with a W loop. This is fine, but because the b quark is so much heavier than the s quark, the diagram does not conserve energy. We need to have a third particle which carries away the difference in energy between the b and the s, so we allow the loop to emit a gauge boson. And thus we have the diagram above.
Thus, in addition to the box diagrams above, there are penguin diagrams which contribute to Bs → μμ. As a nice ‘homework’ exercise, you can try drawing all of the penguins that contribute to this process in the Standard Model. (Most of the work is relabeling diagrams for different internal states.)
[Remark, 6/23: my colleague Monika points out that it’s ironic that I drew the b, s, photon penguin since this penguin doesn’t actually contribute to the dimuon decay! (For experts: the reason is the Ward identity.) ]
## Supersymmetry and the Bs → mu mu penguin
Finally, I’d like to give an example of a new physics scenario where we would expect that penguins containing new particles give a large contribution to the Bs → μμ branching ratio. It turns out that this happens quite often in models of supersymmetry or, more generally, ‘two Higgs doublet models.’
If neither of those words mean anything to you, then all you have to know is that these models have not just one, but two independent Higgs particles which obtain separate vacuum expectation values (vevs). The punchline is that there is a free parameter in such theories called tan β which measures the ratio of the two vevs, and that for large values of tan β, the Bs → μμ branching ratio goes like (tan β)6 … which can be quite large and can dwarf the Standard Model contribution.
Added 6/23, because I couldn't help it: a supersymmetric penguin. Corny image from one of my talks.
[What follows is mostly for ‘experts,’ my apologies.]
On a slightly more technical note, it’s not often well explained why this branching ratio goes like the sixth power of tan β, so I did want to point this out for anyone who was curious. There are three sources of tan β in the amplitude; these all appear in the neutral Higgs diagram:
Each blue dot is a factor of tan β. The Yukawa couplings at each Higgs vertex goes like the fermion mass divided by the Higgs vev. For the down-type quarks and leptons, this gives a factor of m/v ~ 1/cos β ~ tan β for large tan β. An additional factor of comes from the mixing between the s and b quarks, which also goes like the Yukawa coupling. (This is the blue dot on the s quark leg.) Hence one has three powers of tan β in the amplitude, and thus six powers of tan β in the branching ratio.
## Outlook
While the LHCb result was somewhat sobering, we can still cross our fingers and hope that there is still an excess to be discovered in the near future. The LHC shuts down for repairs at the end of next year; this should provide ample data for LHCb to probe all the way down to the Standard Model expectation value for this process. Meanwhile, it seems that while I’ve been writing this post there have been intriguing hints of a Higgs (also via our editor)… [edit, 6/23: Aidan put up an excellent intro to these results]
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http://www.physicsforums.com/showthread.php?t=374684
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Recognitions:
Gold Member
## A glance beyond the quantum model
I wanted to follow up on a couple of specific points that were raised in another thread, and felt it would be better to split the discussion off here. The references for the discussion are:
A glance beyond the quantum model, Navascues and Wunderlich (2009)
"One of the most important problems in Physics is how to reconcile Quantum Mechanics with General Relativity. Some authors have suggested that this may be realized at the expense of having to drop the quantum formalism in favor of a more general theory. However, as the experiments we can perform nowadays are far away from the range of energies where we may expect to observe non-quantum effects, it is difficult to theorize at this respect. Here we propose a fundamental axiom that we believe any reasonable post-quantum theory should satisfy, namely, that such a theory should recover classical physics in the macroscopic limit. We use this principle, together with the impossibility of instantaneous communication, to characterize the set of correlations that can arise between two distant observers. Although several quantum limits are recovered, our results suggest that quantum mechanics could be falsified by a Bell-type experiment if both observers have a sufficient number of detectors. "
...And a recent comment on the above (by a PF member no less :)
Comment on "A glance beyond the quantum model", Peter Morgan (2010)
"The aim of "A glance beyond the quantum model" [arXiv:0907.0372] to modernize the Correspondence Principle is compromised by an assumption that a classical model must start with the idea of particles, whereas in empirical terms particles are secondary to events. The discussion also proposes, contradictorily, that observers who wish to model the macroscopic world classically should do so in terms of classical fields, whereas, if we are to use fields, it would more appropriate to adopt the mathematics of random fields. Finally, the formalism used for discussion of Bell inequalities introduces two assumptions that are not necessary for a random field model, locality of initial conditions and non-contextuality, even though these assumptions are, in contrast, very natural for a classical particle model. Whether we discuss physics in terms of particles or in terms of events and (random) fields leads to differences that a glance would be well to notice. "
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Of interest - and there has been recent discussion about several of these points - are the following:
a) Can you speak of particles without discussing the associated fields?
b) Are the fields themselves discrete or continuous?
c) It the correspondence between the macroscopic world and the microscopic world fundamental? Can we recover certain classical concepts - such as "no-signaling principle" or the introduced idea of "macroscopic locality" when a large number of particles are involved and our measurement devices fail to resolve discrete particles?
d) Are their low-energy Bell-type experiments that can set limits on the unification of quantum theory and gravity?
e) Anything else you might think of from the above...
Quote by DrChinese Of interest - and there has been recent discussion about several of these points - are the following: a) Can you speak of particles without discussing the associated fields? b) Are the fields themselves discrete or continuous? c) It the correspondence between the macroscopic world and the microscopic world fundamental? Can we recover certain classical concepts - such as "no-signaling principle" or the introduced idea of "macroscopic locality" when a large number of particles are involved and our measurement devices fail to resolve discrete particles? d) Are their low-energy Bell-type experiments that can set limits on the unification of quantum theory and gravity? e) Anything else you might think of from the above...
a) Not easily, but one can talk about measurement results (which one can say are properties of the measured systems, even though the systems themselves are not seen) in a finite-dimensional Hilbert space context, without introducing the Schrodinger equation or a quantum field. Indeed, quantum information lives very happily in this regime and often is thought to be fundamental.
b) One can work with either discrete or continuous mathematics. QFT on a lattice has certainly taught us stuff. Universality makes it difficult to make a categorical statement here, because discrete structure at the Planck scale would presumably be washed out at the scales at which we have any present hope of making measurements.
c) I think I take the Correspondence Principle to be a methodological requirement that comes from social issues in science. If one wants a new theory to get a running start, it helps to be able to point out how it is the same as and how it is different from the theories we currently take to be empirically effective. If one can show that the new theory can legitimately adopt a lot of the empirical effectiveness of an existing theory, it leaves less to do to establish how the new theory is better. The Correspondence Principle was used with stunning effectiveness by the founders of the new quantum theory in the late 20s to constrain quantum theory, so it seems worthwhile to attempt the same sort of approach now.
From a Correspondence Principle point of view, given that our current best theories are QFT and GR, it makes sense to stick with a field approach of some sort in attempts to construct new theories. The choice of an effective mathematical structure is important. Part of my enthusiasm for random fields is that they are a powerful generalization of classical differentiable fields that introduces the concept of probability in a mathematically correct way (whereas differentiable fields don't sit well with the measure theory), and which can be presented in a way that is very closely parallel to quantum fields. Retrospectively, a random field formalism might make a Correspondence Principle approach more possible.
However, this does not, to my more-or-less empiricist approach, entail that the world is continuous, only that it can be useful to use continuum mathematics, always supposing that we can get finite answers out, somehow.
d) Dunno. When I critiqued Navascués' and Wunderlich's assumptions I was careful not to get into the actual purpose of their paper because I know not much about QG.
e) Even less to say. Except that I believe the published version of the Navascués and Wunderlich paper is free to access on Proc. Roy. Soc. A, at http://rspa.royalsocietypublishing.o...t/466/2115/881, and is preferable, from the point of view of my Comment, because they introduced classical fields into their paper only after the current arXiv version.
Recognitions:
Quote by DrChinese a) Can you speak of particles without discussing the associated fields?
I've been wondering about a similar question in a different context,
namely the problem of IR divergences in QED, and correct identification
of the asymptotic dynamics, and hence also the asymptotic fields.
(I'm not sure whether what follows is tangential to your focus in this
thread, but I guess you'll tell me if so. :-)
In brief, I find it interesting that considering charged particles
together with their Coulomb fields seems to solve the IR problem in
QED in a much more physically satisfactory way than the typical
textbook treatments. This (imho) lends credence to the proposition that
it's better to treat particles together with their entourage of associated
fields, although such composite dressed entities are of course nonlocal.
For those who want more detail, here's an extract from a summary I've
been writing up for myself about it...
-----------------------------
Textbook treatments of the infrared (IR) divergences in quantum
electrodynamics (QED) typically introduce a small fictitious photon
mass to regularize the integrals. Allowing this mass to approach zero,
it becomes necessary to sum physically measurable quantities, such as
the cross sections for electron scattering, over all possible
asymptotic states involving an infinite number of soft photons, yielding
the so-called "inclusive" cross section.
The IR divergences are thus dealt with by restricting attention only to these
"IR-safe" quantities such as the inclusive cross section. However, various
authors have expressed dissatisfaction with this state of affairs in which
the cross sections become the objects of primary interest rather than the
S-matrix. The seminal paper of Chung (Chu) showed how one may
dress the asymptotic electron states with an operator familiar from the
Glauber theory of photon coherent states, thereby eliminating IR divergences
in the S-matrix to all orders for the cases he considered.
In a series of papers, Kibble (Kib1,Kib2,Kib3,Kib4) provided a much
more extensive (and more rigorous) development of Chung's idea, solving
the dynamical problem to show that IR divergences are eliminated by
dressing the asymptotic electron states by coherent states of soft
photons. Kibble constructed a very large nonseparable state space, within
which various separable subspaces are mapped into each other by the
S-matrix, but there is no stable separable subspace that is mapped into
itself.
less cumbersome treatment involving modification of the asymptotic
condition and a new space of asymptotic states which is not only
separable, but also relativistically and gauge invariant. They were
able to derive Chung's formulas without the laborious calculations of
Kibble, yet also obtained a more satisfactory generalization to the
case of arbitrary numbers of charged particles and photons in the
initial and final states.
KF emphasized the role of the nonvanishing interaction of QED at
asymptotic times as the source of the problems. This inconvenient fact
means that QED's asymptotic dynamics is not governed by the usual
free Hamiltonian $$H_0$$, so perturbative approaches starting from such
free states are singular (a so-called "discontinuous" perturbation).
Standard treatments rely on the unphysical fiction of adiabatically
switching off the interaction, but KF wished to find a more physically
satisfactory operator governing the asymptotic dynamics.
Much earlier, Dirac (Dir55) took some initial steps in
constructing a manifestly gauge-invariant electrodynamics. The dressing
operator he obtained is a simplified version of those mentioned above
involving soft-photon coherent states, but he did not
address the IR divergences in this paper. Neither Chung, Kibble, nor
Kulish and Faddeev cite Dirac's paper, and the connection between explicit
gauge invariance and resolution of the IR problem did not emerge until
later. (Who was the first to note this??) In 1965 Dirac noted (Dir65, Dir66)
that problems in QED arise because the full gauge-invariant Hamiltonian is
typically split into a "free" part $$H_0$$
and an "interaction" part $$H_I$$ which are not separately
gauge-invariant. Indeed, Dirac's original 1955 construction had
resulted in an electron together with its Coulomb field, which is
clearly a more physically correct representation of electrons at
asymptotic times: a physical electron is always accompanied by its
Coulomb field.
More recently, Bagan, Lavelle and McMullan (BagLavMcMul-1, BagLavMcMul-2)
("BLM" hereafter) and other collaborators have developed these ideas
further, applying them to IR divergences in QED, and also QCD in which
a different class of so-called "collinear" IR divergence occurs. (See
also the references therein.) These authors generalized Dirac's
construction to the case of moving charged particles. Their dressed
asymptotic fields include the asymptotic interaction, and they show
that the on-shell Green's functions and S-matrix elements for these
charged fields have (to all orders) the pole structure associated with
particle propagation and scattering.
--------------------------------------------
Bibliography for the above:
\bibitem{BagLavMcMul-1}
E. Bagan, M. Lavelle, D. McMullan,
"Charges from Dressed Matter: Construction",
(Available as hep-ph/9909257.)
\bibitem{BagLavMcMul-2}
E. Bagan, M. Lavelle, D. McMullan,
"Charges from Dressed Matter: Physics \& Renormalisation",
(Available as hep-ph/9909262.)
\bibitem{Bal} L. Ballentine,
"Quantum Mechanics -- A Modern Development",
World Scientific, 2008, ISBN 978-981-02-4105-6
\bibitem{Chu}
V. Chung,
"Infrared Divergences in Quantum Electrodynamics",
Phys. Rev., vol 140, (1965), B1110.
\bibitem{Dir55}
P.A.M. Dirac,
"Gauge-Invariant Formulation of Quantum Electrodynamics",
Can. J. Phys., vol 33, (1955), p. 650.
\bibitem{Dir65}
P.A.M. Dirac,
Phys. Rev., vol 139, (1965), B684-690.
\bibitem{Dir66}
P.A.M. Dirac,
"Lectures on Quantum Field Theory",
Belfer Graduate School of Science, Yeshiva Univ., NY, 1966
\bibitem{Dol}
J. D. Dollard,
"Asymptotic Convergence and the Coulomb Interaction",
J. Math. Phys., vol, 5, no. 6, (1964), 729-738.
\bibitem{Kib1}
T.W.B. Kibble,
"Coherent Soft-Photon States \& Infrared Divergences. I.
Classical Currents",
J. Math. Phys., vol 9, no. 2, (1968), p. 315.
\bibitem{Kib2}
T.W.B. Kibble,
"Coherent Soft-Photon States \& Infrared Divergences. II.
Mass-Shell Singularities of Green's Functions",
Phys. Rev., vol 173, no. 5, (1968), p. 1527.
\bibitem{Kib3}
T.W.B. Kibble,
"Coherent Soft-Photon States \& Infrared Divergences.
III. Asymptotic States and Reduction Formulas.",
Phys. Rev., vol 174, no. 5, (1968), p. 1882.
\bibitem{Kib4}
T.W.B. Kibble,
"Coherent Soft-Photon States \& Infrared Divergences.
IV. The Scattering Operator.",
Phys. Rev., vol 175, no. 5, (1968), p. 1624.
J. R. Klauder \& B. Skagerstam,
"Coherent States -- Applications in Physics \& Mathematical Physics",
World Scientific, 1985, ISBN 9971-966-52-2
"Asymptotic Conditions and Infrared Divergences in Quantum
Electrodynamics",
Theor. Math. Phys., vol 4, (1970), p. 745
-----------------------------
Recognitions:
## A glance beyond the quantum model
Quote by Peter Morgan Part of my enthusiasm for random fields is that they are a powerful generalization of classical differentiable fields that introduces the concept of probability in a mathematically correct way (whereas differentiable fields don't sit well with the measure theory)
It's been a while since I looked at your papers, and I don't remember the point about
"random fields ... introducing the concept of probability in a mathematically correct way".
Could you elaborate on the details of this point, and/or give specific places in your
earlier papers where you discuss this, please?
I found your discussion of IR divergences interesting, and I've bookmarked it both for the discussion and for the references, but I regret that I can't speak to it at this point, except to say that I've never seen anything that makes dressed particles look conceptually simple enough (or, more specifically, algebraically simple enough -- though that's not a conceptual direction one necessarily has to take).
Quote by strangerep It's been a while since I looked at your papers, and I don't remember the point about "random fields ... introducing the concept of probability in a mathematically correct way". Could you elaborate on the details of this point, and/or give specific places in your earlier papers where you discuss this, please?
I've had considerable trouble getting this across to anyone, although it seems clear as day to me, so I'm happy to try again. If one introduces a path integral approach for particles (though the same fact can be expressed in Hamiltonian formalisms), the path integral is dominated by nowhere differentiable paths (I've just seen this cited from Reed & Simon, which I don't have, but it ties in with my understanding of Hamiltonian methods). This works OK for particle trajectories, but notoriously, people have trouble making path integral methods rigorous in the field context, where there are more infinite limits to be taken. In the field context, I would say that no-one has really adequate mathematical control of the procedure, although some people are happy to say that renormalization is adequate mathematical control.
For a quantum field, some mathematical control (but not enough) is achieved by defining the quantum field to be an operator-valued distribution, not an operator-valued field, so that to construct an operator one has to "average" the quantum field over a finite region. As we consider smaller regions, the variance of such operators diverges, so if we try to talk about the quantum field at a point we find that, more-or-less, we would always observe either +infinity or -infinity, which isn't a good start for constructing a differentiable function. For the vacuum state of a free quantum field, the two point correlation function $$\left\langle 0\right|\widehat{\phi}(x)\widehat{\phi}(y)\left|0\right\rangle$$ is finite for $$x-y$$ non-zero, but diverges as $$x\rightarrow y$$, which is to say that the variance $$\left\langle 0\right|\widehat{\phi}(x)^2\left|0\right\rangle$$ is infinite. It's also to say that the correlation coefficient between the observed values at x and y is finite/infinity=zero, if we relinquish decent control of what limits we're taking. For interacting fields this only gets much worse, of course.
For classical fields, when we introduce the classical probability density $${\normalfont exp}(-\beta H(\phi))$$ of a thermal state we also find ourselves working with classical fields that are nowhere differentiable. I shouldn't say that there's no other way to deal with the situation, it can be managed, but random fields do deal with it pretty well, without introducing anything relatively exotic such as nonstandard analysis, for example.
I've taken it to be useful to consider random fields because they can be presented as random-variable-valued distributions, or even as mutually commutative operator-valued distributions, which are close enough to quantum fields to make comparison of random fields and quantum fields very interesting. In comparison of classical differentiable fields with quantum fields it's hard to know how to start. Part of why this is good to do is that it does give a new way to think about quantum fields, even if the more ambitious hopes I have for my program don't work out.
Recognitions:
Quote by Peter Morgan For a quantum field, some mathematical control (but not enough) is achieved by defining the quantum field to be an operator-valued distribution, not an operator-valued field, so that to construct an operator one has to "average" the quantum field over a finite region. As we consider smaller regions, the variance of such operators diverges, so if we try to talk about the quantum field at a point we find that, more-or-less, we would always observe either +infinity or -infinity, which isn't a good start for constructing a differentiable function. For the vacuum state of a free quantum field, the two point correlation function $$\left\langle 0\right|\widehat{\phi}(x)\widehat{\phi}(y)\left|0\right\rangle$$ is finite for $$x-y$$ non-zero, but diverges as $$x\rightarrow y$$, which is to say that the variance $$\left\langle 0\right|\widehat{\phi}(x)^2\left|0\right\rangle$$ is infinite.
Yep... standard stuff so far. $$\widehat{\phi}(x)$$ are not operators, therefore applying
them to a state vector is technically illegal. They must be smeared with test functions to
give bonafide operators. OK.
I've taken it to be useful to consider random fields because they can be presented as random-variable-valued distributions, or even as mutually commutative operator-valued distributions, which are close enough to quantum fields to make comparison of random fields and quantum fields very interesting.
introduce the concept of probability in a "mathematically correct way".
My perception of your random fields (or should we say "Lie fields"?)
is as an inf-dim Lie algebra parameterized by spacetime points,
as we discussed a while back. But obviously I'm missing some crucial
connection between this and probability. I need you to be more explicit/expansive
on this point if I'm to understand...
Quote by strangerep You didn't really answer the question I asked about how random fields introduce the concept of probability in a "mathematically correct way". My perception of your random fields (or should we say "Lie fields"?) is as an inf-dim Lie algebra parameterized by spacetime points, as we discussed a while back. But obviously I'm missing some crucial connection between this and probability. I need you to be more explicit/expansive on this point if I'm to understand...
Perhaps a more abstract approach? A set of operators $$\{\widehat{\phi}_{f_i}\}$$ generates a *-algebra (to which we add an operator 1, which acts as a multiplicative identity in the *-algebra). A state $$\omega(\widehat{A})$$ over the *-algebra is positive on any operator of the form $$AA^\dagger$$, $$\omega(AA^\dagger)\ge 0$$, and $$\omega(1)=1$$, which allows us to use the GNS-construction of a Hilbert space. We take $$\omega(\widehat{A})$$ to be the expected value associated with the random variable A, corresponding to the operator $$\widehat{A}$$. The sample space associated with A is the set of eigenvalues of $$\widehat{A}$$, and the probability density in the state $$\omega$$ can be written as $$P(x)=\omega(\delta(\widehat{A}-x.1))$$. From this we can generate the characteristic function associated with that probability density as a Fourier transform $$\widetilde{P}(\lambda)=\omega(exp(i\lambda\widehat{A}))$$.
All that is standard QM, albeit not in elementary terms. When we introduce joint observables $$\widehat{A}$$ and $$\widehat{B}$$, the difference between QM and random fields is only whether they always commute, which they do not for QM, but they do for a random field. In the random field case, the function $$\widetilde{P}(\lambda,\mu)=\omega(exp(i\lambda\widehat{A}+i\mu\widehat{ B}))$$ is a joint characteristic function, whereas it is not (in general) the Fourier transform of a positive function in the QM case (unless $$[\widehat{A},\widehat{B}]=0$$, which will be the case if the two operators are constructed using only quantum field operators associated with mutually space-like regions).
I hope this is at an appropriate level and helpful? I'm not sure it's an answer even if the level is OK, in which case sorry.
I realize now that I should also note that IMO a random field and a quantum field are better considered as indexed by smooth functions on space-time, not indexed by space-time points. I find it helpful to think of the index functions as "window functions", which is the name this concept is given in signal processing. Learning to work intuitively with the concept of operator-valued distributions took me several years, but it seems obvious enough by now that I have trouble explaining. Sorry.
Recognitions:
Quote by Peter Morgan [...] the probability density in the state $\omega$ can be written as $$P(x)=\omega(\delta(\widehat{A}-x.1))$$ .
I thought I was conversant with the algebraic approach,
but what is your $\delta$ in the above expression?
Hi strangerep, Thank you very much for the interesting review of IR divergences and references. I am very interested in combining these ideas with the dressed particles approach of Greenberg and Schweber. Do you have any suggestions? Eugene.
Recognitions:
Quote by meopemuk I am very interested in combining these ideas with the dressed particles approach of Greenberg and Schweber. Do you have any suggestions?
I'm wrestling with related questions, but it's too soon for me to say anything.
(And it would probably be too speculative for Physics Forums anyway. :-)
Perhaps after you've had a look through the referenced papers we could
discuss further in a separate thread, or privately.
Quote by strangerep I thought I was conversant with the algebraic approach, but what is your $\delta$ in the above expression?
Hee! It's a Dirac delta, perhaps too quick and dirty as a way to construct a probability density. It's also, formally, the inverse Fourier transform of the characteristic function that follows,
$$\omega(exp(i\lambda\widehat{\phi}_f))= \omega(\sum_{k=0}^{\infty}\left[\frac{(i\lambda\widehat{\phi}_f)^k}{k!}\right])$$.
Except, urp, that there should be a factor of $2\pi$. That seems a better way to introduce it. The expected values of $\widehat{\phi}_f^k$ are the moments of the vacuum state's probability density over $\widehat{\phi}_f$, giving us the characteristic function, which we can formally inverse Fourier transform to obtain the probability density. In practice, one constructs the characteristic function as a scalar function of $\lambda$, which for the free field vacuum would be a Gaussian, which inverse Fourier transforms into a Gaussian probability density.
It does seem that what you have to say about IR divergences and dressed particles is pretty vague at the moment. A "discuss these papers" thread would seem reasonable to me, however, and it's generally a helpful discipline to pay attention to how speculative what we're doing is and to look for ways to rein it in. Indeed, I think that the path to my getting papers into journals is very much about that process, partly because anything that looks speculative is often picked on by referees as a reason to reject a paper that they only have general misgivings about. If you make no speculations, the referee's rejection letter is generally much more helpful, because they have to engage more with the paper to give a clear reason to reject it. At a grosser level, which I have often visited, editors can spot speculative from about a light-year away, so one then doesn't get as far as relatively more detailed feedback from a referee. Getting papers published is just making the speculation look well reasoned --- not getting rid of it, which IMO often makes for a boring paper.
Quote by Peter Morgan Hee! It's a Dirac delta, perhaps too quick and dirty as a way to construct a probability density. It's also, formally, the inverse Fourier transform of the characteristic function that follows, $$\omega(exp(i\lambda\widehat{\phi}_f))= \omega(\sum_{k=0}^{\infty}\left[\frac{(i\lambda\widehat{\phi}_f)^k}{k!}\right])$$. Except, urp, that there should be a factor of $2\pi$.
A citation is possible, page 119 of Itzykson & Zuber, Section 3-1-2, eq. (3-63) does exactly this (in a 1980, McGraw-Hill paperback edition; I don't know whether there are substantially different editions, which is why I'm over-specifying).
Recognitions:
Quote by Peter Morgan page 119 of Itzykson & Zuber, Section 3-1-2, eq. (3-63) does exactly this [...]
OK, so let's see if I now understand what your random fields are...
Your random fields (and their noncommutative quantum generalization) are basically
a generalization of certain concepts in classical statistical mechanics. Actually, let me
quote some stuff from the draft book of Neumaier & Westra, arXiv:0810.1019v1,
that (I think) relates to this way of looking at things...
(This is from their sect 1.2...)
An important ingredient in statistical mechanics is a phase space density ρ playing the role of a measure to calculate probabilities; the expectation value of a function f is given by $$\langle f \rangle ~=~ \int \rho f ~~~~~~~~~~~~~~ (1.1)$$ where the integral indicates integration with respect to the so-called Liouville measure in phase space. In the quantum version of statistical mechanics the density ρ gets replaced by a linear operator ρ on Hilbert space called the density matrix, the functions become linear opera- tors, and we have again (1.1), except that the integral is now interpreted as the quantum integral, $$\int f ~=~ tr f, ~~~~~~~~~~~~~~ (1.2)$$ where tr f denotes the trace of a trace class operator. We shall see that the algebraic properties of the classical integral and the quantum integral are so similar that using the same name and symbol is justified.
But (iiuc) a difference between this approach and yours is that, whereas classical
quantities f are normally interpreted as functions over phase space (hence the
Liouville measure above), your random fields are just over 4D spacetime (or rather
over a space of test functions over 4D spacetime). (?)
So I'm now trying to follow your criticism of Navascues and Wunderlich more carefully...
But... in the online version (arXiv:0907.0372), which is all I have access to right now,
I can't relate your quotes to their section numbering. I also can't find the mention
of "continuous fields"? Is the Proc Roy Soc version different from the online version,
and you were commenting on the former?
Quote by strangerep But (iiuc) a difference between this approach and yours is that, whereas classical quantities f are normally interpreted as functions over phase space (hence the Liouville measure above), your random fields are just over 4D spacetime (or rather over a space of test functions over 4D spacetime). (?)
Yes, my definition and constructions are manifestly Lorentz and translation invariant. The usual definition is Lorentz and translation invariant, but not manifestly so. The usual phase space approach, is only possible if only mass shell components of a test function contribute. The restriction to only a single mass shell (if that's what is wanted) is implemented in my approach by the inner product having a delta function restriction to the mass shell.
So I'm now trying to follow your criticism of Navascues and Wunderlich more carefully... But... in the online version (arXiv:0907.0372), which is all I have access to right now, I can't relate your quotes to their section numbering. I also can't find the mention of "continuous fields"? Is the Proc Roy Soc version different from the online version, and you were commenting on the former?
The Proc. Roy. Soc. A version is different, which I didn't discover until after I submitted my comment. The Proc. Roy. Soc. A version is available for free, I think because of the Royal Society's anniversary celebrations. Go to http://dx.doi.org/ and enter the DOI that's in my paper, 10.1098/rspa.2009.0453, or go straight to the Proc. Roy. Soc. A page, http://rspa.royalsocietypublishing.o...t/466/2115/881. [You won't find any citation to the arXiv version in my paper, the arXiv administration added it to the arXiv abstract, in their wisdom.]
Recognitions:
Quote by Peter Morgan [...] the Proc. Roy. Soc. A page, http://rspa.royalsocietypublishing.o...t/466/2115/881.
At the end of your comment paper, you say:
Navascués and Wunderlich have done something rather remarkable. By introducing the idea of continuous fields in their paper they have laid themselves open to a criticism that they must introduce random fields, and encourage a discussion that would otherwise have been mpossible. If they had introduced fields without daring to go “beyond” the standard model, they would equally have been conventionally impervious. Navascués’ and Wunderlich’s paper requires a vigorous condemnation where something less ambitious would have gone unchallenged. Finally, this comment does not touch Navascués’ and Wunderlich’s argument; their paper’s flaw, I think, and such little as it is, is to have introduced a classical field metaphysics and not to have thought enough of it. [...]
In this one paragraph, you say "requires a vigorous condemnation" but then say
"this comment does not touch Navascués’ and Wunderlich’s argument". So... you're not
actually arguing against the essential results of NW's paper? But only the "little" flaw
of using the phrase "continuous fields" rather than "random fields" ?
Quote by strangerep In [the last] paragraph, you say "requires a vigorous condemnation" but then say "this comment does not touch Navascués’ and Wunderlich’s argument". So... you're not actually arguing against the essential results of NW's paper? But only the "little" flaw of using the phrase "continuous fields" rather than "random fields"?
Mixed messages indeed. I was cross at Navascués’ and Wunderlich’s assumptions, not at their argument. When I saw your quote, "requires a vigorous condemnation", I thought you might have quoted me out of context, because I thought I surely must have mentioned that it was their assumptions that require a vigorous condemnation, but I see that I was vigorous at their whole paper.
Getting the politeness right in a critical comment apparently evaded me, but I do think these are serious Physicists, running with a respectable idea, that we might look at what the Correspondence Principle might tell us about the Planck scale and beyond. I think it's a good idea to do that in principle, but I'm telling them that "Oh, I wouldn't start from there". That could be boring.
What saves their paper, I think, and what made it possible for me to make my comment constructive, I hope, is that they introduce classical continuous fields. They do it half-heartedly, and they might even have been made to introduce fields because the referee said, "well, but what about fields?", but they do it. This is a potentially significant development, because the ways in which classical fields might be used to model Physics is underdeveloped. Good math approaches to QFT take it almost for granted that QFT is about
fields, not about particles, particularly because of the Unruh effect, since about 20 years ago, say.
Very few Physicists, however, take the obvious next step, which is that in that case we'd better find ways to talk about fields instead of about particles. A notable exception is Art Hobson, whose web-site has available a copy of the paper of his that I cite. He's concerned with how to teach QFT, and proposes to do it by emphasizing a field perspective. Andrei Khrennikov, who is a Mathematical Physicist who turned seriously to foundations of Physics about ten years ago, takes a similar line, but his mathematical methods and mine are very different. 't Hooft's approach is also similar but different, as also for Wolfram. Elze and Wetterich are two other hard Mathematical Physicists who are developing entirely different formalisms. Khrennikov, Elze, and Wetterich are developing fairly traditional stochastic differential equation methods, 't Hooft and Wolfram are developing finite automata models, in which the statistics are generated by simulation; I'm the only one, to my knowledge, who is seriously developing an algebraic presentation of random fields. A friend, Ken Wharton, is developing a view based on classical fields, with me trying to persuade him that he has to introduce probability in a mathematically decent way, and him dragging his heels, perfectly reasonably, because he doesn't like a metaphysics that includes probability. If I have a metaphysics, it is a metaphysics of statistics and ensembles rather than of probability, with my being content with a relatively loose, somewhat post-positivist relationship between observed statistics and the mathematics of probability, but we've been negotiating this fine point for a while. All this move to fields, and lattices, has more-or-less started to happen in the last ten years (although there's also Stochastic Electrodynamics, dating from the 60s, and Nelson's approach, too, from the 70s, but these are arguably problematic because they are preoccupied with fermions being particles, bosons being fields, and these programs, although I believe always continuing, have had significant hiatuses).
As far as all these different approaches are concerned, I consider that mine has the most to gain from comparison with QFT, in a Correspondence Principle sort of way, because I can even show that a free complex quantum field is empirically equivalent to a free random field, so I'm especially happy to see NW talking about CP. Nonetheless, I would only claim that my approach gives a useful counterpoint to stochastic or lattice methods, not that my approach is correct. I wish not to claim that the world is continuous rather than discrete, for example. A random field, properly speaking, is only an indexed set of random variables, it is only associated with a continuous space-time if we specifically take the index set to be the Schwarz space of functions on space-time (or some other well enough controlled function space on space-time).
So why should NW be pulled up for this rather than someone else, given that almost no-one pays any attention to how their use of particle-talk conditions their thinking? Their fault, I suppose, is that they mention fields so glibly, without thinking about how rich the seam is, and proceed with a discussion that would make almost no sense if they tried to accommodate both particle and field ways of thinking. At the very least, their conclusions would have to be hedged with a statement such as "if we think only in terms of particles, ...".
NW's discussion of Bell inequalities is similarly conventional. If they did the job properly, they would know that the flow of ideas surrounding Bell inequalities has been shifting dramatically over the last 10 years, with roots that go back to about 1980. The relative significances of contextuality and of locality are gradually being teased out more and more clearly. Anybody trying to talk about Bell inequalities should at least acknowledge those currents, and again they should either accommodate the various possibilities or explicitly hedge their conclusions.
As the last sentence of the abstract says, "Whether we discuss physics in terms of particles or in terms of events and (random) fields leads to differences that a glance would be well to notice." Perhaps I might add, even more facetiously, "or at least what is not noticed ought to be mentioned", but that would go far enough that I imagine the editors would have sent it back to me unrefereed. As it is, my comment is with referees; I hope they see that my criticism is constructive.
Recognitions:
"classical fields" [...] "continuous fields" [...] "random fields" [...]
When I first read NW's sentence where they mention "continuous fields"
my first thought was "what _precisely_ do they mean by that phrase"?
(Such pedantic detail becomes important in discussions about
"introducing probability in a mathematically correct way"...)
So let me ask you the question...
You've explained in earlier posts what you mean by a random field
(i.e., an inf-dim commutative *-algebra, with basis elements indexed
from a space of well-behaved functions over spacetime, such that
state functionals over this algebra make sense).
What then are your definitions of the phrases "classical field"
and "continuous field" ?
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https://arxiv.org/abs/0710.2886
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hep-th
(what is this?)
# Title: $κ$-Minkowski space, scalar field, and the issue of Lorentz invariance
Abstract: We describe $\kappa$-Minkowski space and its relation to group theory. The group theoretical picture makes it possible to analyze the symmetries of this space. As an application of this analysis we analyze in detail free field theory on $\kappa$-Minkowski space and the Noether charges associated with deformed spacetime symmetries.
Comments: Based on the talk given at the conference "From Quantum to Emergent Gravity", SISSA, June, 2007; to appear in the proceedings Subjects: High Energy Physics - Theory (hep-th) Cite as: arXiv:0710.2886 [hep-th] (or arXiv:0710.2886v1 [hep-th] for this version)
## Submission history
From: Jerzy Kowalski-Glikman [view email]
[v1] Mon, 15 Oct 2007 17:53:41 GMT (106kb,D)
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http://link.springer.com/chapter/10.1007%2F3-540-55599-4_120
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Lecture Notes in Computer Science Volume 605, 1992, pp 725-732
Date: 14 Jul 2005
Repeated matrix squaring for the parallel solution of linear systems
* Final gross prices may vary according to local VAT.
Abstract
Given a n×n nonsingular linear system Ax=b, we prove that the solution x can be computed in parallel time ranging from Ω(log n) to O(log2 n), provided that the condition number, μ(A), of A is bounded by a polynomial in n. In particular, if μ(A) = O(1), a time bound O(log n) is achieved. To obtain this result, we reduce the computation of x to repeated matrix squaring and prove that a number of steps independent of n is sufficient to approximate x up to a relative error 2−d, d=O(1). This algorithm has both theoretical and practical interest, achieving the same bound of previously published parallel solvers, but being far more simple.
This work has been partly supported by the Italian National Research Council, under the “Progetto Finalizzato Sistemi Informatici e Calcolo Parallelo”, subproject 2 “Processori dedicati”. Part of this work was done while the first author was with the Istituto di Elaborazione dell'Informazione, Consiglio Nazionale delle Ricerche, Pisa (Italy).
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http://rationalwiki.org/wiki/White_hole_cosmology
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# White hole cosmology
Foreword by Ken Ham, so you know it's about science.
White hole cosmology is a pseudoscientific cosmology invented by young Earth creationist Russell Humphreys and put forward in his 1994 book Starlight and Time: Solving the Puzzle of a Young Universe in a Universe with Distant Starlight.[1] Curiously, its "science" is so flawed that it has been criticised even by other creationists. Now that takes some doing.[2]
The theory is not based on any observable evidence, but rather on the creationist desire to solve the challenge to the 6000 year-old earth that the starlight problem poses. White hole cosmology is currently regarded as pseudoscience by the general scientific community, but is claimed to be the truth by creationist organizations such as Answers in Genesis and the Institute for Creation Research.
The main idea of white hole cosmology is that the world was created inside a black hole and that Earth was subjected to intense time dilation so billions of years could have passed outside the field while only a few days would pass inside it.[3]
## Problems with the theory
The theory of white hole cosmology is fatally flawed. The mathematics used by Humphreys are riddled with problems,[4] and special relativity is repeatedly misinterpreted.[5] In several places the theory is even self-contradictory, most notably about the cosmological constant "lambda".[6]
### Compression and intensification of light
The idea requires that the universe outside the Solar System is as old as contemporary scientists hold it to be:[7] 13,700,000,000 years.[8] They then say that while all this time passed outside the vicinity of the Earth, only six days (creation week) passed on earth. The stars outside the dilation field would still be emitting light towards earth at the same rate which would have to be compressed into six days of time, which would cause celestial objects outside the dilation field to appear roughly 833,416,666,666 times brighter inside the field, raising the surface temperature of the earth to hundreds of thousands of Kelvins.
### Size of the original black hole
White hole cosmology states that the black hole from which the universe came from was an even 2 light years across, a nice even number that seems to fit his theory perfectly. The width of Humphrey's black hole would not be such a small pleasant number though.
The black hole according to this theory encompassed all the matter in the observable universe, a number estimated at 3*1055 g.[9] If you have the mass of a black hole you can determine the distance from the singularity to the event horizon using the Schwarzschild equation.
$r_s=\frac{2Gm}{c^2}$
where
G is the gravitational constant.
m is the mass of the black hole.
c is the speed of light.
Solving the equation with the stated mass gives a Schwarzschild radius of 4.7*109 light years.
## White holes in science
A white hole is the theoretical time reversal of a black hole, which is not disallowed by quantum theory. In such a time reversal, however, the second law of thermodynamics would also be reversed. This would result in causality reversal, and would thus be undetectable to any thought process or mechanism operating in such a universe. The upshot is that we might be living in such a universe now and be unable to recognize it.
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https://nrich.maths.org/public/topic.php?code=71&cl=4&cldcmpid=1936
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# Resources tagged with: Mathematical reasoning & proof
Filter by: Content type:
Age range:
Challenge level:
### There are 174 results
Broad Topics > Using, Applying and Reasoning about Mathematics > Mathematical reasoning & proof
### Tetra Inequalities
##### Age 16 to 18 Challenge Level:
Prove that in every tetrahedron there is a vertex such that the three edges meeting there have lengths which could be the sides of a triangle.
### Triangular Intersection
##### Age 14 to 16 Short Challenge Level:
What is the largest number of intersection points that a triangle and a quadrilateral can have?
### Our Ages
##### Age 14 to 16 Challenge Level:
I am exactly n times my daughter's age. In m years I shall be ... How old am I?
### Three Ways
##### Age 16 to 18 Challenge Level:
If x + y = -1 find the largest value of xy by coordinate geometry, by calculus and by algebra.
### Big, Bigger, Biggest
##### Age 16 to 18 Challenge Level:
Which is the biggest and which the smallest of $2000^{2002}, 2001^{2001} \text{and } 2002^{2000}$?
### Always Perfect
##### Age 14 to 16 Challenge Level:
Show that if you add 1 to the product of four consecutive numbers the answer is ALWAYS a perfect square.
### Impossible Triangles?
##### Age 16 to 18 Challenge Level:
Which of these triangular jigsaws are impossible to finish?
##### Age 16 to 18 Challenge Level:
Find all positive integers a and b for which the two equations: x^2-ax+b = 0 and x^2-bx+a = 0 both have positive integer solutions.
### Dalmatians
##### Age 14 to 18 Challenge Level:
Investigate the sequences obtained by starting with any positive 2 digit number (10a+b) and repeatedly using the rule 10a+b maps to 10b-a to get the next number in the sequence.
### Integral Inequality
##### Age 16 to 18 Challenge Level:
An inequality involving integrals of squares of functions.
##### Age 14 to 16 Challenge Level:
Kyle and his teacher disagree about his test score - who is right?
### Unit Interval
##### Age 14 to 18 Challenge Level:
Take any two numbers between 0 and 1. Prove that the sum of the numbers is always less than one plus their product?
### Thousand Words
##### Age 16 to 18 Challenge Level:
Here the diagram says it all. Can you find the diagram?
### Iffy Logic
##### Age 14 to 18 Challenge Level:
Can you rearrange the cards to make a series of correct mathematical statements?
### Square Mean
##### Age 14 to 16 Challenge Level:
Is the mean of the squares of two numbers greater than, or less than, the square of their means?
### Diverging
##### Age 16 to 18 Challenge Level:
Show that for natural numbers x and y if x/y > 1 then x/y>(x+1)/(y+1}>1. Hence prove that the product for i=1 to n of [(2i)/(2i-1)] tends to infinity as n tends to infinity.
### Proximity
##### Age 14 to 16 Challenge Level:
We are given a regular icosahedron having three red vertices. Show that it has a vertex that has at least two red neighbours.
### More Number Sandwiches
##### Age 11 to 16 Challenge Level:
When is it impossible to make number sandwiches?
### Diophantine N-tuples
##### Age 14 to 16 Challenge Level:
Can you explain why a sequence of operations always gives you perfect squares?
### Dodgy Proofs
##### Age 16 to 18 Challenge Level:
These proofs are wrong. Can you see why?
### Euler's Squares
##### Age 14 to 16 Challenge Level:
Euler found four whole numbers such that the sum of any two of the numbers is a perfect square...
### Without Calculus
##### Age 16 to 18 Challenge Level:
Given that u>0 and v>0 find the smallest possible value of 1/u + 1/v given that u + v = 5 by different methods.
### How Many Solutions?
##### Age 16 to 18 Challenge Level:
Find all the solutions to the this equation.
### Little and Large
##### Age 16 to 18 Challenge Level:
A point moves around inside a rectangle. What are the least and the greatest values of the sum of the squares of the distances from the vertices?
### Why 24?
##### Age 14 to 16 Challenge Level:
Take any prime number greater than 3 , square it and subtract one. Working on the building blocks will help you to explain what is special about your results.
### Angle Trisection
##### Age 14 to 16 Challenge Level:
It is impossible to trisect an angle using only ruler and compasses but it can be done using a carpenter's square.
### Modular Fractions
##### Age 16 to 18 Challenge Level:
We only need 7 numbers for modulus (or clock) arithmetic mod 7 including working with fractions. Explore how to divide numbers and write fractions in modulus arithemtic.
### A Long Time at the Till
##### Age 14 to 18 Challenge Level:
Try to solve this very difficult problem and then study our two suggested solutions. How would you use your knowledge to try to solve variants on the original problem?
### Prime AP
##### Age 16 to 18 Challenge Level:
What can you say about the common difference of an AP where every term is prime?
### Polite Numbers
##### Age 16 to 18 Challenge Level:
A polite number can be written as the sum of two or more consecutive positive integers. Find the consecutive sums giving the polite numbers 544 and 424. What characterizes impolite numbers?
### Target Six
##### Age 16 to 18 Challenge Level:
Show that x = 1 is a solution of the equation x^(3/2) - 8x^(-3/2) = 7 and find all other solutions.
### Sixational
##### Age 14 to 18 Challenge Level:
The nth term of a sequence is given by the formula n^3 + 11n . Find the first four terms of the sequence given by this formula and the first term of the sequence which is bigger than one million. . . .
### Interpolating Polynomials
##### Age 16 to 18 Challenge Level:
Given a set of points (x,y) with distinct x values, find a polynomial that goes through all of them, then prove some results about the existence and uniqueness of these polynomials.
### A Biggy
##### Age 14 to 16 Challenge Level:
Find the smallest positive integer N such that N/2 is a perfect cube, N/3 is a perfect fifth power and N/5 is a perfect seventh power.
### Particularly General
##### Age 16 to 18 Challenge Level:
By proving these particular identities, prove the existence of general cases.
### Common Divisor
##### Age 14 to 16 Challenge Level:
Find the largest integer which divides every member of the following sequence: 1^5-1, 2^5-2, 3^5-3, ... n^5-n.
### Mod 3
##### Age 14 to 16 Challenge Level:
Prove that if a^2+b^2 is a multiple of 3 then both a and b are multiples of 3.
### Pythagorean Triples I
##### Age 11 to 16
The first of two articles on Pythagorean Triples which asks how many right angled triangles can you find with the lengths of each side exactly a whole number measurement. Try it!
### Pythagorean Triples II
##### Age 11 to 16
This is the second article on right-angled triangles whose edge lengths are whole numbers.
### Euclid's Algorithm II
##### Age 16 to 18
We continue the discussion given in Euclid's Algorithm I, and here we shall discover when an equation of the form ax+by=c has no solutions, and when it has infinitely many solutions.
### Contrary Logic
##### Age 16 to 18 Challenge Level:
Can you invert the logic to prove these statements?
### The Clue Is in the Question
##### Age 16 to 18 Challenge Level:
Starting with one of the mini-challenges, how many of the other mini-challenges will you invent for yourself?
### Water Pistols
##### Age 16 to 18 Challenge Level:
With n people anywhere in a field each shoots a water pistol at the nearest person. In general who gets wet? What difference does it make if n is odd or even?
### Perfectly Square
##### Age 14 to 16 Challenge Level:
The sums of the squares of three related numbers is also a perfect square - can you explain why?
### Geometric Parabola
##### Age 14 to 16 Challenge Level:
Explore what happens when you draw graphs of quadratic equations with coefficients based on a geometric sequence.
### Pareq Exists
##### Age 14 to 16 Challenge Level:
Prove that, given any three parallel lines, an equilateral triangle always exists with one vertex on each of the three lines.
### Composite Notions
##### Age 14 to 16 Challenge Level:
A composite number is one that is neither prime nor 1. Show that 10201 is composite in any base.
### Proofs with Pictures
##### Age 14 to 18
Some diagrammatic 'proofs' of algebraic identities and inequalities.
### Continued Fractions II
##### Age 16 to 18
In this article we show that every whole number can be written as a continued fraction of the form k/(1+k/(1+k/...)).
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https://icmp2018.org/prog/session/pl2
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# Prize Lectures
Organizers:
• Vojkan Jaksic
• Val Kelly
Each Prize awarded has an associated lecture given during the Congress. Prize recipient names and scheduled lectures are shown below prize descriptions.
### Prize Descriptions
Henri Poincaré Prize
Sponsored by the Daniel Iagolnitzer Foundation.
The Henri Poincaré Prize was created in 1997 to recognize outstanding contributions in mathematical physics, and contributions which lay the groundwork for novel developments in this broad field. The Prize is also created to recognize and support young people of exceptional promise who have already made outstanding contributions to the field of mathematical physics.
The prize is awarded every three years at the International Mathematical Physics Congress and in each case, is an award to three individuals (to be exact, the rules say approximately three allowing for exceptional circumstances, at the discretion of the prize committee). Previous Laureates are listed here.
Prize recipients and their associated lectures are shown below.
IAMP Early Career Award
The prize is awarded at the International Congress of Mathematical Physics (ICMP) in recognition of a single achievement in Mathematical Physics. The prize consists of the sum of 3000€ and is reserved for scientists whose age in years since birth on July 31 of the year of the Congress is less than 35. Previous Laureates are listed here.
The prize recipients and associated lecture are shown below.
IUPAP Young Scientist Prize
Sponsored by the International Union of Pure and Applied Physics.
The Young Scientist Prizes were established in 2007. The recipients of the awards in a given year should have a maximum of 8 years of research experience following their PhD, and should have performed original work of outstanding scientific quality.
The IUPAP Commission C18 for Mathematical Physics awarded its Young Scientist Prizes for the first time in 2009. Previous Laureates are listed here.
There will be three Prizes awarded. Prize recipients and their associated lectures are shown below.
Annales Henri Poincaré Journal Prize
Each year a prize founded by Birkhäuser is awarded for the most remarkable paper published in the journal Annales Henri Poincaré. The winners of the AHP prize are selected by the Editorial Board. Since 2008, the AHP executive board decided to award also distinguished papers.
For further information and prevous Laureates, read here.
Prize recipients and their associated lectures are shown below.
### Lecture Abstracts
• Semyon Dyatlov
University of California, Berkeley
IAMP Early Career Award Lecture
Fractal uncertainty principle and quantum chaos
Fractal uncertainty principle states that no function can be localized close to a fractal set simultaneously in position and momentum. The strongest version so far has been obtained in one dimension by Bourgain and the speaker with recent higher dimensional advances by Han and Schlag. It has applications to spectral gaps in chaotic scattering and to localization and control of high energy eigenfunctions.
More precisely, using the work with Bourgain and earlier work with Zahl, Jin and the speaker proved that on hyperbolic surfaces, the mass of an eigenfunction on an open set is bounded from below independently of the energy. As shown by Jin, these results lead to observability and control for the Schrödinger equation. Another application is the existence of a spectral gap for every convex co-compact hyperbolic surface, which implies local energy decay of waves at high frequency.
Slides: 1200_dyatlov_symposia_monday.pdf Size: 5 mb
• Percy Deift
Courant Institute
Henri Poincaré Prize Lecture
Universality in numerical computation with random data: Case studies and analytical results.
The speaker will discuss various universality aspects of numerical computations using standard algorithms. These aspects include empirical observations, rigorous results, and some speculations about computation in a broader sense.
Joint with C. Pfrang, G. Menon, S. Olver and Thomas Trogdon.
Slides: 1130_deift_symposia_tuesday.pdf Size: 2 mb
MIT
IUPAP Young Scientist Prize Lecture
Telegraph equation from the six-vertex model
I will explain how a second order hyperbolic PDE, known as the telegraph equation, arises in the asymptotic of the height function of a celebrated model of 2d statistical mechanics - the six-vertex (or square ice) model. Homogeneous equation describes the limit shape in the system, and its stochastic inhomogeneous version governs the fluctuations.
Slides: 1630_gorin_symposia_tuesday.pdf Size: 978 kb
• Giovanni Gallavotti
Sapienza University of Rome
Henri Poincaré Prize Lecture
Reversibility, Irreversibility, Friction and Nonequilibrium Ensembles in Navier-Stokes equations
A proposal for a theory of equivalent ensembles in nonequilibrium statistical mechanics.
The case of Navier-Stokes fluids. Equivalent irreversible and reversible friction for incompressible, periodic boundary conditions, constant forcing flows in 2/3D.
Slides: 1400_giovanni_gallavotti_symposia_wednesday.pdf Size: 246 kb
• Annales Henri Poincaré Journal Prize Ceremony
The prize recipients for 2014, 2015, and 2016 will be formally recognized during this brief ceremony.
The associated lectures for each of the prizes are separately scheduled.
• Wei-Kuo Chen
University of Minnesota
IUPAP Young Scientist Prize Lecture
Some recent progress on mean field spin glasses.
Spin glass models were initially introduced by theoretical physicists in order to study some strange magnetic behavior of certain alloys. They exhibit several features, such as quenched disorder and frustration, that are commonly shared in many real world problems involving randomized combinatorial optimizations. In this talk, we will discuss some recent progress on the famous Sherrington-Kirkpatrick mean field spin glass as well as its variants. We will explain Parisi's solution to the computation of the ground state energies and give descriptions on the energy landscapes of the models in relation to the computational hardness of the ground state energies.
Slides: 1645_chen_international_friday.pdf Size: 873 kb
• Phan Thanh Nam
Ludwig Maximilian University
IUPAP Young Scientist Prize Lecture
Nonlinear Gibbs measure and equilibrium Bose gases
Nonlinear Gibbs measure plays an important role in the studies of Euclidean Quantum Field Theory, nonlinear PDEs and stochastic PDEs. I will discuss the natural emergence of this measure as the mean-field limit of bosonic equilibrium states. The talk is based on joint work with Mathieu Lewin and Nicolas Rougerie.
Slides: 1715_phan_thanh_nam_international_friday.pdf Size: 232 kb
• Michael Aizenman
Princeton University
Henri Poincaré Prize Lecture
Emergent structures in statistical mechanics
Equilibrium states of classical and quantum systems can often be understood in terms of spontaneously emergent random geometric structures. Examples of such can be seen in the spontaneous organization of Ising and Potts spins into cliques, whose statistics are given by the Fortuin - Kasteleyn random cluster models, the random current representation of the equilibrium Gibbs states of Ising / phi^4 models, and loop based organization of certain quantum spin chains into spin zero clusters. Uncovering the hidden stochastic geometric features allows insights on the model’s phase structure, and the nature of the correlation functions. For quantum spin chains the loop representations are of relevance for the phenomena of dimerization, the emergence of boundary spin excitations, and in some cases of topological states. Mentioned in the talk will be results based on both old and recent collaborations.
• David Damanik
Rice
Annales Henri Poincaré Journal 2014 Prize Lecture
Schrödinger operators with thin spectra
In the early days of the spectral analysis of Schrödinger operators, the essential spectrum commonly turned out to be an interval, or at least a union of intervals. In the 1980's, new types of spectra were discovered, displaying a Cantor set structure. In this talk we present recent work on Schrödinger operators whose spectra are even thinner, having zero Lebesgue measure, or even zero Hausdorff dimension. The mechanisms leading to these results will be elucidated. This is joint work with Jake Fillman, Anton Gorodetski and Milivoje Lukic.
Article: Damanik, D., Fillman, J. & Gorodetski, A. Ann. Henri Poincaré (2014) 15: 1123. https://doi.org/10.1007/s00023-013-0264-6
Slides: 1645_2_damanik_symposia_friday.pdf Size: 3 mb
• Juliane Rama
Fraunhofer FHR
Annales Henri Poincaré Journal 2015 Prize Lecture
Instability of pre-existing resonances in the DC Stark effect
This talk is based on the article:
I. Herbst, J. Rama, "Instability of Pre-Existing Resonances Under a Small Constant Electric Field", Ann. Henri Poincar$\acute{\rm e}$ 16 (2015), 2783 - 2835.
A simple model operator (Friedrichs model) with a pre-existing resonance $r_0$, defined in a dilation or translation analytic framework, is considered. Adding a potential corresponding to a small constant electric field of strength $f>0$ (DC Stark effect) perturbs the pre-existing resonance into (infinitely many) resonances of the resulting operator. It is shown that the pre-existing resonance $r_0$ is unstable in the weak field limit $f\downarrow 0$, in the sense that the new resonances do not converge to $r_0$ as $f\downarrow 0$. In a dilation analytic framework this instability result in the DC Stark effect is in contrast to the AC Stark effect (time-periodic electric field), where the pre-existing resonance is stable in the weak field limit.
Article: Herbst, I. & Rama, J. Ann. Henri Poincaré (2015) 16: 2783. https://doi.org/10.1007/s00023-014-0389-2
• Wojciech Dybalski
Technische Universität München
Annales Henri Poincaré Journal 2016 Prize Lecture
Lieb-Robinson bounds, Arveson spectrum and Haag-Ruelle scattering theory for gapped quantum spin systems
We consider translation invariant gapped quantum spin systems satisfying the Lieb-Robinson bound and containing single-particle states in a ground state representation. Following the Haag-Ruelle approach from relativistic quantum field theory, we construct states describing collisions of several particles, and define the corresponding S-matrix. For the purpose of our analysis we adapt the concepts of almost local observables and energy-momentum transfer (or Arveson spectrum) from relativistic QFT to the lattice setting. Our results hold, in particular, in the Ising model in strong transverse magnetic fields. Based on these developments, a general discussion of the problem of asymptotic completeness for gapped quantum spin systems will be given.
Based on joint work with S. Bachmann and P. Naaijkens.
Article: Bachmann, S., Dybalski, W. & Naaijkens, P. Ann. Henri Poincaré (2016) 17: 1737. https://doi.org/10.1007/s00023-015-0440-y
Slides: 1745_dybalski_symposia_friday.pdf Size: 429 kb
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https://worldwidescience.org/topicpages/b/bismuth+borides.html
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#### Sample records for bismuth borides
1. Kinetics of borided gear steels
ration (FeB + Fe2B) due to the high intensity stress states generally situated at the ... performed molten salt boriding of AISI D2 steel with borax (Na2B4O7) as the ... the borided layer thickness; silicon, chromium and aluminium have moderate.
2. Nanodispersed boriding of titanium alloy
International Nuclear Information System (INIS)
Kostyuk, K.O.; Kostyuk, V.O.
2015-01-01
The problem of improving the operational reliability of machines is becoming increasingly important due to the increased mechanical, thermal and other loads on the details. There are many surface hardening methods for machines parts which breakdown begins with surface corruption. The most promising methods are chemical-thermal treatment. The aim of this work is to study the impact of boriding on the structure and properties of titanium alloy. Materials and Methods: The material of this study is VT3-1 titanium alloy. The boriding were conducted using nanodispersed powder blend based on boric substances. It is established that boriding of paste compounds allows obtaining the surface hardness within 30 - 29 GPa and with declining to 27- 26 GPa in layer to the transition zone (with total thickness up to 110 μm) owing to changes of the layer phase composition where T 2 B, TiB, TiB 2 titanium borides are formed. The increasing of chemical-thermal treatment time from 15 minutes to 2 hours leads to thickening of the borated layer (30 - 110 μm) and transition zone (30 - 190 μm). Due to usage of nanodispersed boric powder, the boriding duration is decreasing in 2 - 3 times. This allows saving time and electric energy. The developed optimal mode of boriding the VT3-1 titanium alloy allows obtaining the required operational characteristics and to combine the saturation of the surface layer with atomic boron and hardening
3. Superconductivity in borides and carbides
International Nuclear Information System (INIS)
Muranaka, Takahiro
2007-01-01
It was thought that intermetallic superconductors do not exhibit superconductivity at temperatures over 30 K because of the Bardeen-Cooper-Schrieffer (BCS) limit; therefore, researchers have been interested in high-T c cuprates. Our group discovered high-T c superconductivity in MgB 2 at 39 K in 2001. This discovery has initiated a substantial interest in the potential of high-T c superconductivity in intermetallic compounds that include 'light' elements (borides, carbides, etc.). (author)
4. Boride particles in a powder metallurgy superalloy
Energy Technology Data Exchange (ETDEWEB)
Witt, M C; Charles, J A
1985-12-01
Using optical and electron metallography, the composition, morphology, and distribution of M/sub 3/B/sub 2/ borides in as-hipped (hot isostatically pressed) samples of the powder metallurgy superalloy Nimonic AP1 have been determined. Two types of boride are present depending on the HIP temperature. Hipping below the boride solvus results in low-aspect ratio particles, distributed both inter- and intragranularly. Hipping above the boride solvus produces high-aspect ratio particles which are exclusively intergranular. A small difference in both lattice parameter and composition has been measured. Electron energy loss spectroscopy of the particles has confirmed the presence of boron, and laser ion-induced mass analysis has indicated a low carbon level. The higher susceptibility to edge cracking during forging of material hipped above the boride solvus is related to the boride morphology. Studies of the subsequent recrystallization of the forged samples have indicated that necklace formation is neither inhibited nor accelerated by the presence of grain boundary borides. 18 references.
5. New superhard boride composite materials. Part 1; Neue superharte Borid-Verbundwerkstoffe. Teil 1
Energy Technology Data Exchange (ETDEWEB)
Zachariev, Z.
2001-07-01
Contents: Investigations of diffusion coupling between steels and borides (ZrB{sub 2}, TiB{sub 2}, CrB, MoB); Diffusion saturation of armco iron inpowdered borides; Gaseous phase transport intensivation of the transition metal using suitable activators (vapour phase process); boron circonisation of steels; High-temperature oxidation studies on boride composite coatings on iron and steel; Corrosion resistance of boride coated iron base composites; Superhard boride coatings on hard metals and on cermet plates with reduced tungsten contents. [German] Dieser Beitrag ist wie folgt gegliedert: Untersuchung der Diffusionskopplung zwischen Staehlen und den Boriden (ZrB{sub 2}, TiB{sub 2}, CrB, MoB); Diffusionssaettigung von Armcoeisen in Pulverboride; Gasphasentransport-Intensivierung des Uebergangsmetalls mittels geeigneter Akivatoren (vapour phase process); Borzirkonieren von Staehlen; Hochtemperaturoxidationuntersuchungen von Borid-Composite-Schichten auf Eisen und Stahl; Korrosionsbestaendigkeit der boridbeschichteten Verbundwerkstoffe auf Eisenbasis; Superharte Boridbeschichtungen auf Hartmetall und auf Metallkeramikplatten mit reduziertem Wolframgehalt.
6. Characterization of AISI 4140 borided steels
International Nuclear Information System (INIS)
Campos-Silva, I.; Ortiz-Dominguez, M.; Lopez-Perrusquia, N.; Meneses-Amador, A.; Escobar-Galindo, R.; Martinez-Trinidad, J.
2010-01-01
The present study characterizes the surface of AISI 4140 steels exposed to the paste-boriding process. The formation of Fe 2 B hard coatings was obtained in the temperature range 1123-1273 K with different exposure times, using a 4 mm thick layer of boron carbide paste over the material surface. First, the growth kinetics of boride layers at the surface of AISI 4140 steels was evaluated. Second, the presence and distribution of alloying elements on the Fe 2 B phase was measured using the Glow Discharge Optical Emission Spectrometry (GDOES) technique. Further, thermal residual stresses produced on the borided phase were evaluated by X-ray diffraction (XRD) analysis. The fracture toughness of the iron boride layer of the AISI 4140 borided steels was estimated using a Vickers microindentation induced-fracture testing at a constant distance of 25 μm from the surface. The force criterion of fracture toughness was determined from the extent of brittle cracks, both parallel and perpendicular to the surface, originating at the tips of an indenter impression. The fracture toughness values obtained by the Palmqvist crack model are expressed in the form K C (π/2) > K C > K C (0) for the different applied loads and experimental parameters of the boriding process.
7. Characterization of AISI 4140 borided steels
Science.gov (United States)
Campos-Silva, I.; Ortiz-Domínguez, M.; López-Perrusquia, N.; Meneses-Amador, A.; Escobar-Galindo, R.; Martínez-Trinidad, J.
2010-02-01
The present study characterizes the surface of AISI 4140 steels exposed to the paste-boriding process. The formation of Fe 2B hard coatings was obtained in the temperature range 1123-1273 K with different exposure times, using a 4 mm thick layer of boron carbide paste over the material surface. First, the growth kinetics of boride layers at the surface of AISI 4140 steels was evaluated. Second, the presence and distribution of alloying elements on the Fe 2B phase was measured using the Glow Discharge Optical Emission Spectrometry (GDOES) technique. Further, thermal residual stresses produced on the borided phase were evaluated by X-ray diffraction (XRD) analysis. The fracture toughness of the iron boride layer of the AISI 4140 borided steels was estimated using a Vickers microindentation induced-fracture testing at a constant distance of 25 μm from the surface. The force criterion of fracture toughness was determined from the extent of brittle cracks, both parallel and perpendicular to the surface, originating at the tips of an indenter impression. The fracture toughness values obtained by the Palmqvist crack model are expressed in the form KC( π/2) > KC > KC(0) for the different applied loads and experimental parameters of the boriding process.
8. Characterization of AISI 4140 borided steels
Energy Technology Data Exchange (ETDEWEB)
Campos-Silva, I., E-mail: [email protected] [Instituto Politecnico Nacional, Grupo Ingenieria de Superficies, SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F., 07738 (Mexico); Ortiz-Dominguez, M.; Lopez-Perrusquia, N.; Meneses-Amador, A. [Instituto Politecnico Nacional, Grupo Ingenieria de Superficies, SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F., 07738 (Mexico); Escobar-Galindo, R. [Instituto de Ciencia de Materiales de Madrid (CSIC), E-28049 Cantoblanco, Madrid (Spain); Martinez-Trinidad, J. [Instituto Politecnico Nacional, Grupo Ingenieria de Superficies, SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F., 07738 (Mexico)
2010-02-01
The present study characterizes the surface of AISI 4140 steels exposed to the paste-boriding process. The formation of Fe{sub 2}B hard coatings was obtained in the temperature range 1123-1273 K with different exposure times, using a 4 mm thick layer of boron carbide paste over the material surface. First, the growth kinetics of boride layers at the surface of AISI 4140 steels was evaluated. Second, the presence and distribution of alloying elements on the Fe{sub 2}B phase was measured using the Glow Discharge Optical Emission Spectrometry (GDOES) technique. Further, thermal residual stresses produced on the borided phase were evaluated by X-ray diffraction (XRD) analysis. The fracture toughness of the iron boride layer of the AISI 4140 borided steels was estimated using a Vickers microindentation induced-fracture testing at a constant distance of 25 {mu}m from the surface. The force criterion of fracture toughness was determined from the extent of brittle cracks, both parallel and perpendicular to the surface, originating at the tips of an indenter impression. The fracture toughness values obtained by the Palmqvist crack model are expressed in the form K{sub C}({pi}/2) > K{sub C} > K{sub C}(0) for the different applied loads and experimental parameters of the boriding process.
9. Ultra-fast boriding of metal surfaces for improved properties
Science.gov (United States)
Timur, Servet; Kartal, Guldem; Eryilmaz, Osman L.; Erdemir, Ali
2015-02-10
A method of ultra-fast boriding of a metal surface. The method includes the step of providing a metal component, providing a molten electrolyte having boron components therein, providing an electrochemical boriding system including an induction furnace, operating the induction furnace to establish a high temperature for the molten electrolyte, and boriding the metal surface to achieve a boride layer on the metal surface.
10. Kinetics of electrochemical boriding of low carbon steel
International Nuclear Information System (INIS)
Kartal, G.; Eryilmaz, O.L.; Krumdick, G.; Erdemir, A.; Timur, S.
2011-01-01
In this study, the growth kinetics of the boride layers forming on low carbon steel substrates was investigated during electrochemical boriding which was performed at a constant current density of 200 mA/cm 2 in a borax based electrolyte at temperatures ranging from 1123 K to 1273 K for periods of 5-120 min. After boriding, the presence of both FeB and Fe 2 B phases were confirmed by the X-ray diffraction method. Cross-sectional microscopy revealed a very dense and thick morphology for both boride phases. Micro hardness testing of the borided steel samples showed a significant increase in the hardness of the borided surfaces (i.e., up to (1700 ± 200) HV), while the hardness of un-borided steel samples was approximately (200 ± 20) HV. Systematic studies over a wide range of boriding time and temperature confirmed that the rate of the boride layer formation is strongly dependent on boriding duration and has a parabolic character. The activation energy of boride layer growth for electrochemical boriding was determined as (172.75 ± 8.6) kJ/mol.
11. Boriding with boron carbide base pastes
International Nuclear Information System (INIS)
Aliev, A.A.
1978-01-01
The aim of this paper is to develop an advanced technique of boriding using pastes under the conditions of furnace heating. The research is carried out on flat specimens of 20 and U8 steels pre-annealed in vacuum. B 4 C base pastes were used as saturating media, and the glue prepared by dissolving of nitrocellulose in the mixture of butylacetate and acetone was used as a bond. Measured was the depth of diffusion layers, produced on the 20 and u8 steels after boriding with the pastes under different temperatures and saturation times. The results of metallographic analysis show that borided layers have a specific needle-like structure. The surface of the specimens is clean and free from any paste residues and traces of partial melting
12. Production and properties of boride powders
International Nuclear Information System (INIS)
Klinskaya, N.A.; Koroleva, E.B.; Petrunichev, V.A.
1990-01-01
Results of plasma metallization of boride powders 40-80 μ diam. are presented. Peculiarities of changes of granulometric powder composition and of metallic cover on refractory cores were investigated. There are shown size- and compositional cores effects on metallization level of poders and on cover structure
13. Preparation of single phase molybdenum boride
International Nuclear Information System (INIS)
Camurlu, Hasan Erdem
2011-01-01
Highlights: → Formation of Mo and a mixture of molybdenum boride phases take place in preparation of molybdenum borides. → It is intricate to prepare single phase molybdenum borides. → Formation of single phase MoB from MoO 3 + B 2 O 3 + Mg mixtures has not been reported previously. → Single phase MoB was successfully prepared through a combination of mechanochemical synthesis and annealing process. - Abstract: The formation of MoB through volume combustion synthesis (VCS), and through mechanochemical synthesis (MCS) followed by annealing has been investigated. MoO 3 , B 2 O 3 and Mg were used as reactants while MgO and NaCl were introduced as diluents. Products were leached in dilute HCl solution and were subjected to X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) examinations. Mo was the major phase component in the VCS products under all the experimental conditions. Mo 2 B, MoB, MoB 2 and Mo 2 B 5 were found as minor phases. Products of MCS contained a mixture of Mo 2 B, MoB, MoB 2 and Mo. After annealing the MCS product at 1400 deg. C for 3 h, single phase α-MoB was obtained.
14. Growth kinetics of boride coatings formed at the surface AISI M2 during dehydrated paste pack boriding
Energy Technology Data Exchange (ETDEWEB)
Doñu Ruiz, M.A., E-mail: [email protected] [Universidad Politécnica del Valle de México UPVM, Grupo Ciencia e Ingeniería de Materiales, Av. Mexiquense S/N Esquina Av. Universidad Politécnica, Col Villa Esmeralda, 54910 Tultitlan (Mexico); López Perrusquia, N.; Sánchez Huerta, D. [Universidad Politécnica del Valle de México UPVM, Grupo Ciencia e Ingeniería de Materiales, Av. Mexiquense S/N Esquina Av. Universidad Politécnica, Col Villa Esmeralda, 54910 Tultitlan (Mexico); Torres San Miguel, C.R.; Urriolagoitia Calderón, G.M. [Instituto Politécnico Nacional, SEPI-ESIME, Unidad Profesional Adolfo López Mateos Zacatenco, Edificio 5, 2do. Piso, Col. Lindavista, CP 07738 México, D.F. (Mexico); Cerillo Moreno, E.A. [Universidad Politécnica del Valle de México UPVM, Grupo Ciencia e Ingeniería de Materiales, Av. Mexiquense S/N Esquina Av. Universidad Politécnica, Col Villa Esmeralda, 54910 Tultitlan (Mexico); Cortes Suarez, J.V. [Univerisdad Autónoma Metropolitana Unidad Azcapotzalco, Av. San Pablo 180 Azcapotzalco 02200, Área de Ciencia de los Materiales, México, D.F. (Mexico)
2015-12-01
The growth kinetics of the boride coatings (FeB and Fe{sub 2}B) at the surface of AISI M2 high speed steels were studied in this work. Boriding thermochemical treatment was carried out by dehydrated paste pack at three different temperatures 1173, 1223, and 1273 K and four exposure times 1, 3, 5, and 7 h, respectively. The presence of FeB and Fe{sub 2}B phases was identified by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction method. In order to obtain the boron diffusion coefficients at the FeB/Fe{sub 2}B boride coatings, a mathematical model based on the mass balance at the growing interfaces was proposed under certain assumptions. Likewise the parabolic growth constants and the boride incubation time were established as a function of the parameters η (T) and ε (T). The activation energy values estimated for the FeB and Fe{sub 2}B layers were 233.42 and 211.89 kJ mol{sup −1} respectively. A good agreement was obtained between the simulated values of boride layer thicknesses and the experimental results. Finally, empirical relationships of boride coating thickness as a function of boriding temperature and time are presented. - Highlights: • Formed boride coatings at the surface of AISI M2 high speed steels by new process dehydrated paste pack boriding. • The model was based on the mass balance equation at the FeB/Fe{sub 2}B and Fe{sub 2}B/Fe interfaces by considering the boride incubation time. • A good agreement was obtained between the simulated values of boride layers coatings and the experimental results.
15. Preparation of iron boride layers from the gas phase
International Nuclear Information System (INIS)
Marx, G.; Plaenitz, H.; Treffer, G.; Koenig, H.; Altenburger, S.
1980-01-01
Coating of Armco iron, steel-C100W1, and steel-100Cr6 with borides by decomposition of boron tribromide on the surface of the specimens is described. The experiments were carried out in a laboratory apparatus at temperatures between 923 and 1223 K. The dependence of the thickness of the boride layers on time and temperature is presented in graphs
16. Low-temperature heat capacity of molybdenum borides
International Nuclear Information System (INIS)
Bolgar, A.S.; Klinder, A.V.; Novoseletskaya, L.M.; Turov, V.P.; Klochkov, L.A.; Lyashchenko, A.B.
1988-01-01
Heat capacity of molybdenum borides Mo 2 B, MoB, Mo 2 B 5 is studied for the first time in the 60-300 K range using the adiabatic method. Standard (at 298.15 K) thermodynamic functions (enthalpy, heat capacity, entropy, reduced Gibbs energy) of molybdenum borides are calculated
17. Pulsed nanocrystalline plasma electrolytic boriding as a novel ...
Potentiodynamic polarization and electrochemical impedance spectroscopy were employed to test borided CP-Ti, treated by a relatively new method called pulsed plasma electrolytic boriding. The results show excellent corrosion resistance for modified CP-Ti. The effect of frequency and duty cycle of pulsed current was ...
18. Pulsed nanocrystalline plasma electrolytic boriding as a novel ...
WINTEC
borided CP-Ti, treated by a relatively new method called pulsed plasma electrolytic boriding. The results ... ratio, high stiffness and strength (Donachie 2000; Lutjer- ing and Albrecht ..... both direct current and a.c. techniques. Although the main ...
19. Investigation of diffusion kinetics of plasma paste borided AISI 8620 ...
Henríquez 2009), plasma boriding (Rodríguez et al 1999) and plasma paste boriding (Gunes et al 2011; Yoon et al ... symmetric geometry with monochromatized radiation (Cu Kα, λ = 0.15418 nm). ..... cate the degree of reliability of the predicted results, when compared with that of the experiments. ... low alloy steels. Surf.
20. Fracture toughness of borides formed on boronized ductile iron
International Nuclear Information System (INIS)
Sen, Ugur; Sen, Saduman; Koksal, Sakip; Yilmaz, Fevzi
2005-01-01
In this study, fracture toughness properties of boronized ductile iron were investigated. Boronizing was realized in a salt bath consisting of borax, boric acid and ferro-silicon. Boronizing heat treatment was carried out between 850 and 950 deg. C under the atmospheric pressure for 2-8 h. Borides e.g. FeB, Fe 2 B formed on ductile iron was verified by X-ray diffraction (XRD) analysis, SEM and optical microscope. Experimental results revealed that longer boronizing time resulted in thicker boride layers. Optical microscope cross-sectional observation of borided layers showed dentricular morphology. Both microhardness and fracture toughness of borided surfaces were measured via Vickers indenter. The harnesses of borides formed on the ductile iron were in the range of 1160-2140 HV 0.1 and fracture toughness were in the range of 2.19-4.47 MPa m 1/2 depending on boronizing time and temperature
1. Surface oxidation phenomena of boride coatings grown on iron
International Nuclear Information System (INIS)
Carbucicchio, M.; Palombarini, G.; Sambogna, G.
1992-01-01
Very hard boride coatings are grown on various metals using thermochemical as well as chemical vapour deposition techniques. In this way many surface properties, and in particular the wear resistance, can be considerably improved. Usually, also the corrosion behaviour of the treated components is important. In particular, oxidizing atmospheres are involved in many applications where, therefore, coating-environment interactions can play a relevant role. In a previous work, the early stages of the oxidation of iron borides were studied by treating single phase compacted powders in flowing oxygen at low temperatures (300-450deg C). In the present paper, the attention is addressed to the oxidation of both single phase and polyphase boride coatings thermochemically grown on iron. The single phase boride coatings were constituted by Fe 2 B, while the polyphase coatings were constituted by an inner Fe 2 B layer and an outer FeB-base layer. All the boride layers displayed strong (002) preferred crystallographic orientations. (orig.)
2. Hardness of carbides, nitrides, and borides
International Nuclear Information System (INIS)
Schroeter, W.
1981-01-01
Intermetallic compounds of metals with non-metals such as C, N, and B show different hardness. Wagner's interaction parameter characterizes manner and extent of the interaction between the atoms of the substance dissolved and the additional elements in metallic mixed phases. An attempt has been made to correlate the hardness of carbides, nitrides, and borides (data taken from literature) with certain interaction parameters and associated thermodynamic quantities (ΔH, ΔG). For some metals of periods 4, 5, and 6 corresponding relations were found between microhardness, interaction parameters, heat of formation, and atomic number
3. Magnesium Aluminum Borides as Explosive Materials
Science.gov (United States)
2011-12-20
pestle and screened -325 mesh to remove the filter paper. However, some of the filter paper remained in this powder. Table 13 Compositions of...Property of Si-B System Ceramics,” J. Japan Soc. Pow. and Pow. Met., 41[11] 1299-1303 (1994). 53. H. Nakamura, K. Murata, T. Anan, and Y. Hara...Oxidation of Zirconium Borides,” J. Japan Explosives Society, 55[4] 142-146 (1994). 54. M. Woerle, R.Nesper, G. Mair, M. Schwarz, and H. G. von Schnering
4. Platinum boride nanowires: Synthesis and characterization
International Nuclear Information System (INIS)
Ding Zhanhui; Qiu Lixia; Zhang Jian; Yao Bin; Cui Tian; Guan Weiming; Zheng Weitao; Wang Wenquan; Zhao Xudong; Liu Xiaoyang
2012-01-01
Highlights: ► Platinum boride nanowires have been synthesized via the direct current arc discharge method. ► XRD, TEM and SAED indicate that the nanowires are single-crystal PtB. ► Two broad photoluminescence emission peaks at about 586 nm and 626 nm have been observed in the PL spectroscopy of PtB nanowires. - Abstract: Platinum boride (PtB) nanowires have been successfully fabricated with direct current arc discharge method using a milled mixture of platinum (Pt) and boron nitride (BN) powders. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the compositions, morphology, and structures of the samples. The results show that PtB nanowires are 30–50 nm thick and 20–30 μm long. TEM and selected area electron diffraction (SAED) patterns identify that the PtB nanowires are single-crystalline in nature. A growth mechanism based on vapor–liquid–solid (VLS) process is proposed for the formation of nanowires.
5. Electrochemical boriding and characterization of AISI D2 tool steel
International Nuclear Information System (INIS)
Sista, V.; Kahvecioglu, O.; Eryilmaz, O.L.; Erdemir, A.; Timur, S.
2011-01-01
D2 is an air-hardening tool steel and due to its high chromium content provides very good protection against wear and oxidation, especially at elevated temperatures. Boriding of D2 steel can further enhance its surface mechanical and tribological properties. Unfortunately, it has been very difficult to achieve a very dense and uniformly thick boride layers on D2 steel using traditional boriding processes. In an attempt to overcome such a deficiency, we explored the suitability and potential usefulness of electrochemical boriding for achieving thick and hard boride layers on this tool steel in a molten borax electrolyte at 850, 900, 950 and 1000 °C for durations ranging from 15 min to 1 h. The microstructural characterization and phase analysis of the resultant boride layers were performed using optical, scanning electron microscopy and X-ray diffraction methods. Our studies have confirmed that a single phase Fe 2 B layer or a composite layer consisting of FeB + Fe 2 B is feasible on the surface of D2 steel depending on the length of boriding time. The boride layers formed after shorter durations (i.e., 15 min) mainly consisted of Fe 2 B phase and was about 30 μm thick. The thickness of the layer formed in 60 min was about 60 μm and composed mainly of FeB and Fe 2 B. The cross sectional micro-hardness values of the boride layers varied between 14 and 22 GPa, depending on the phase composition.
6. Borides of the group 1 metals of the periodic system
International Nuclear Information System (INIS)
Samsonov, G.V.; Serebryakova, T.I.; Neronov, V.A.
1975-01-01
The borides of alkali metals (lithium, sodium, potassium) and the metals of a copper subgroup (copper, silver, gold) are described. Consideration is given to the crystalline structure and state diagrams of the metal systems within the first group of the Periodic Table with boron. Existence, formation conditions and physico-chemical properties of binary boride phases are characterized. Conclusion is made as to the absence of interaction between boron and silver. Information on the interaction between gold and boron is scanty and conflicting. Methods are described suitable for the production of the borides of the metals within the first group of the Periodic Table [ru
7. Properties of boride-added powder metallurgy magnesium alloys
Science.gov (United States)
Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi
2009-06-01
Magnesium alloys with metallic borides, magnesium diboride (MgB2) or aluminum diboride (AlB2), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB2, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg17Al12, formed in the alloy with AlB2, which was consistent with its higher hardness.
8. Properties of boride-added powder metallurgy magnesium alloys
Energy Technology Data Exchange (ETDEWEB)
Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi [Department of Mechanical Engineering, Tokyo City University 1-28-1 Tamazutsumi, Setagaya, Tokyo 158-8557 (Japan)], E-mail: [email protected]
2009-06-01
Magnesium alloys with metallic borides, magnesium diboride (MgB{sub 2}) or aluminum diboride (AlB{sub 2}), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB{sub 2} exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB{sub 2}, did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg{sub 17}Al{sub 12}, formed in the alloy with AlB{sub 2}, which was consistent with its higher hardness.
9. Properties of boride-added powder metallurgy magnesium alloys
International Nuclear Information System (INIS)
Tanaka, Atsushi; Yoshimura, Syota; Fujima, Takuya; Takagi, Ken-ichi
2009-01-01
Magnesium alloys with metallic borides, magnesium diboride (MgB 2 ) or aluminum diboride (AlB 2 ), were investigated regarding their mechanical properties, transverse rupture strength (TRS) and micro Vickers hardness (HV). The alloys were made from pure Mg, Al and B powders by mechanical alloying and hot pressing to have boride content of between 2.0 and 20 vol%. The alloy with AlB 2 exhibited an obvious improvement of HV around a boride content of 6 vol% though the other alloy, with MgB 2 , did not. TRS showed moderate maxima around the same boride content region for the both alloys. X-ray diffraction measurements indicated an intermetallic compound, Mg 17 Al 12 , formed in the alloy with AlB 2 , which was consistent with its higher hardness.
10. Tetragonal ternary borides: superconductivity, ferromagnetism and the role of scandium
International Nuclear Information System (INIS)
Matthias, B.T.; Patel, C.K.N.; Barz, H.; Corenzwit, E.; Vandenberg, J.M.
1978-01-01
The authors report and discuss two discoveries made while studying the condensation phenomena of ternary rhodium borides, MRh 4 B 4 . M is generally a trivalent transition metal, usually a rare earth element RE. An exception is scandium which by itself does not form an isomorphous boride, but in combination with many other elements will do just that. A suprising correlation between ferromagnetic and superconducting transition temperatures has been found. (Auth.)
11. Structure, microstructure and residual stresses in borided steels
Czech Academy of Sciences Publication Activity Database
Pala, Z.; Mušálek, Radek; Kyncl, J.; Harcuba, P.; Stráský, J.; Kolařík, K.
2013-01-01
Roč. 20, č. 2 (2013), s. 93-95 ISSN 1211-5894. [Struktura 2013 - Kolokvium Krystalografické společnosti. Češkovice (Blansko), 09.09.2013-13.09.2013] Institutional support: RVO:61389021 Keywords : boriding * surface hardening * iron borides * tooth-shaped microstructure * residual stresses Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://www.xray.cz/ms/bul2013-2/s6.pdf
12. Formation of boride layers on steel substrates
International Nuclear Information System (INIS)
Stergioudis, G.
2006-01-01
Boronizing coatings were prepared by means of pack cementation technique. It was found that using the appropriate substrate and controlling parameters of the boribing process such as boron activity of the mixture, temperature and time of treatment, it is possible to obtain a structure predominantly consisting of the Fe 2 B phase. In the present study low alloy ferritic steels were chosen as substrates. Changing the boron carbide concentration in the mixture and the temperature and time of boronizing process the conditions of the boronizing were altered. As a result the formation of the Fe 2 B phase is enhanced. Characterization of the as-borided steels is discussed based on X-ray diffraction and Curie temperature measurements. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
13. Synthesis of cobalt boride nanoparticles using radio frequency thermal plasma
International Nuclear Information System (INIS)
Lapitan, Jr. Lorico DS.; Ying Ying Chen; Seesoek Choe; Watanabe, Takayuki
2012-01-01
Nano size cobalt boride particles were synthesized from vapor phase using a 30 kw-4 MHz radio frequency (RF) thermal plasma. Cobalt and boron powder mixtures used as precursors in different composition and feed rate were evaporated immediately in the high temperature plasma and cobalt boride nanoparticles were produced through the quenching process. The x-ray diffractometry (XRD) patterns of cobalt boride nanoparticles prepared from the feed powder ratio of 1:2 and 1:3 for Co: B showed peaks that are associated with the Co 2 B and CoB crystal phases of cobalt boride. The XRD analysis revealed that increasing the powder feed rate results in a higher mass fraction and a larger crystalline diameter of cobalt boride nanoparticles. The images obtained by field emission scanning electron microscopy (FE-SEM) revealed that cobalt boride nanoparticles have a spherical morphology. The crystallite size of the particles estimated with XRD was found to be 18-22 nm. (author)
14. Valley polarization in bismuth
Science.gov (United States)
Fauque, Benoit
2013-03-01
The electronic structure of certain crystal lattices can contain multiple degenerate valleys for their charge carriers to occupy. The principal challenge in the development of valleytronics is to lift the valley degeneracy of charge carriers in a controlled way. In bulk semi-metallic bismuth, the Fermi surface includes three cigar-shaped electron valleys lying almost perpendicular to the high symmetry axis known as the trigonal axis. The in-plane mass anisotropy of each valley exceeds 200 as a consequence of Dirac dispersion, which drastically reduces the effective mass along two out of the three orientations. According to our recent study of angle-dependent magnetoresistance in bismuth, a flow of Dirac electrons along the trigonal axis is extremely sensitive to the orientation of in-plane magnetic field. Thus, a rotatable magnetic field can be used as a valley valve to tune the contribution of each valley to the total conductivity. As a consequence of a unique combination of high mobility and extreme mass anisotropy in bismuth, the effect is visible even at room temperature in a magnetic field of 1 T. Thus, a modest magnetic field can be used as a valley valve in bismuth. The results of our recent investigation of angle-dependent magnetoresistance in other semi-metals and doped semiconductors suggest that a rotating magnetic field can behave as a valley valve in a multi-valley system with sizeable mass anisotropy.
15. Mechanochemically Driven Syntheses of Boride Nanomaterials
Science.gov (United States)
Blair, Richard G.
Solid state metathesis reactions have proven to be a viable route to the production of unfunctionalized nanomaterials. However, current implementations of this approach are limited to self-propagating reactions. We have been investigating mechanically driven metathesis reactions. The use of high-energy ball mills allows control of crystallite sizes without the use of a capping group. Reinforcement materials with crystallite sizes on the order of 5-30 nm can be produced in such a manner. Borides are of particular interest due to their strength, high melting point, and electrical conductivity. The ultimate goal of this work is to prepare oxide and capping group-free nanoparticles suitable for incorporation in thermoelectric, polymer, and ceramic composites. Ultimately this work will facilitate the production of improved thermoelectric materials that will provide robust, deployable, power generation modules to supplement or replace fuel cell, Stirling, and battery-derived power sources. It will also result in scalable, bulk syntheses of tough, refractory, conductive nanomaterials for polymer composites with improved electrical properties, ceramic composites with enhanced fracture toughness, and composites with enhanced neutron reflectance and/or absorbance.
16. Corrosion behavior of boride layers evaluated by the EIS technique
Energy Technology Data Exchange (ETDEWEB)
Campos, I. [Instituto Politecnico Nacional. SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico)], E-mail: [email protected]; Palomar-Pardave, M. [Universidad Autonoma Metropolitana-Azcapotzalco, Materials Department, Avenue San Pablo 180 Col. Reynosa Tamaulipas, Mexico D.F. 02200 (Mexico); Amador, A. [Tecnologico de Monterrey, Campus Ciudad de Mexico, Calle del Puente 222 Col. Ejidos de Huipulco, Mexico D.F. 14380 (Mexico); VillaVelazquez, C. [Instituto Politecnico Nacional. SEPI-ESIME U.P. Adolfo Lopez Mateos, Zacatenco, Mexico D.F. 07738 (Mexico); Hadad, J. [Tecnologico de Monterrey, Campus Ciudad de Mexico, Calle del Puente 222 Col. Ejidos de Huipulco, Mexico D.F. 14380 (Mexico)
2007-09-30
The corrosion behavior of boride layers at the AISI 304 steel surface is evaluated in the present study. Electrochemical impedance spectroscopy (EIS) technique was used for the evaluation of the polarization resistance at the steel surface, with the aid of AUTOLAB potentiostat. Samples were treated with boron paste thickness of 4 and 5 mm, in the range of temperatures 1123 {<=} T {<=} 1273 K and exposed time of 4 and 6 h. The electrochemical technique employed 10 mV AC with a frequency scan range from 8 kHz to 3 mHz in deaerated 0.1 M NaCl solution. Nyquist diagrams show that the highest values of corrosion resistance are present in the samples borided at the temperature of 1273 K, with treatment time of 4 h and 4 mm of boron paste thickness. The values of corrosion resistance on borided steels are compared with the porosity exhibited in the layers.
17. Synthesis of Magnesium Nickel Boride Aggregates via Borohydride Autogenous Pressure.
Science.gov (United States)
Shahbazi, Mahboobeh; Cathey, Henrietta E; Mackinnon, Ian D R
2018-03-23
We demonstrate synthesis of the ternary intermetallic MgNi₃B₂ using autogenous pressure from the reaction of NaBH₄ with Mg and Ni metal powder. The decomposition of NaBH₄ to H₂ and B₂H₆ commences at low temperatures in the presence of Mg and/or Ni and promotes formation of Ni-borides and MgNi₃B₂ with the increase in temperature. MgNi₃B₂ aggregates with Ni-boride cores are formed when the reaction temperature is >670 °C and autogenous pressure is >1.7 MPa. Morphologies and microstructures suggest that solid-gas and liquid-gas reactions are dominant mechanisms and that Ni-borides form at a lower temperature than MgNi₃B₂. Magnetic measurements of the core-shell MgNi₃B₂ aggregates are consistent with ferromagnetic behaviour in contrast to stoichiometric MgNi₃B₂ which is diamagnetic at room temperature.
18. Laser borided composite layer produced on austenitic 316L steel
Directory of Open Access Journals (Sweden)
Mikołajczak Daria
2016-12-01
Full Text Available Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.
19. Thermodynamic properties of molybdenum borides at temperatures above 300 K
International Nuclear Information System (INIS)
Bolgar, A.S.; Blinder, A.V.; Serbova, M.I.
1990-01-01
Enthalpy of Mo 2 B, MoB, Mo 2 B 5 borides within the range of temperatures above 300 K has been experimentally studied. Parameters of temperature dependences of enthalpy, heat capacity, entropy and the reduced Gibbs energy of the studied substances are calculated within a wide range. It is stated that high-temperature heat capacity of the studied borides can be presented as a sum of the electron component, a harmonic part of the lattice component and a contribution caused by anharmonic oscillations of lattice atoms. Values of coefficients of isothermal compressibility of Mo 2 , MoB, Mo 2 B 5 within the high temperature range are estimated
20. Swelling and fracturing of borides under neutron irradiation
International Nuclear Information System (INIS)
Krainy, A.G.; Ogorodnikov, V.V.; Grinik, E.U.; Chirko, L.I.; Shinakov, A.A.
1994-01-01
The neutron irradiation of high temperature borides, which are included in boron-containing reactor materials, results in high internal stresses, leading to considerable swelling and micro- and macro-fracturing. Experimental results over a large range of temperature and fluences, show a change of damage mechanism for borides within 400-530 C: the macro-cracking with formation of annular and radial cracks is observed below this temperature zone. The accumulation of micro-fractures and the process of gas swelling take place at irradiation temperatures above 530 C. The effect of the high internal stresses is compared to external pressure. 12 refs., 4 figs
1. Bismuth toxicity in patients treated with bismuth iodoform paraffin packs.
Science.gov (United States)
Atwal, A; Cousin, G C S
2016-01-01
Bismuth is a heavy metal used in bismuth iodoform paraffin paste (BIPP) antiseptic dressings and in a number of other medical preparations. It can be absorbed systemically and cause toxicity. We report 2 cases of such neurotoxicity after it was used in operations on the jaws. Copyright © 2015. Published by Elsevier Ltd.
2. Development and application of high strength ternary boride base cermets
International Nuclear Information System (INIS)
Takagi, Ken-ichi
2006-01-01
Reaction boronizing sintering is a novel strategy to form a ternary boride coexisting with a metal matrix in a cermet during liquid phase sintering. This new sintering technique has successfully developed world first ternary boride base cermets with excellent mechanical properties such as Mo 2 FeB 2 , Mo 2 NiB 2 and WCoB base ones. In these cermets Mo 2 FeB 2 and Mo 2 NiB 2 base ones consist of a tetragonal M 3 B 2 (M: metal)-type complex boride as a hard phase and a transition metal base matrix. The cermets have already been applied to wear resistant applications such as injection molding machine parts, can making tools, and hot copper extruding dies, etc. This paper focuses on the characteristics, effects of the additional elements on the mechanical properties and structure, and practical applications of the ternary boride base cermets. - Graphical abstract: TRS and hardness of Ni-5B-51Mo-17.5Cr and Ni-5B-51Mo-12.5Cr-5V-xMn mass% cermets as functions of Mn content (Fig. 17)
3. Metal Borohydrides synthesized from metal borides and metal hydrides
DEFF Research Database (Denmark)
Sommer, Sanna
2014-01-01
Aarhus C, Denmark email: [email protected] / [email protected] Magnesium boride, MgB2, ball milled with MH (M = Li, Na, Ca) followed by hydrogenation under high hydrogen pressure, readily forms the corresponding metal borohydrides, M(BH4)x (M = Li, Na, Ca) and MgH2 according to reaction scheme...
4. Assessment of polyphase sintered iron-cobalt-iron boride cermets
International Nuclear Information System (INIS)
Nowacki, J.; Pieczonka, T.
2004-01-01
Sintering of iron, cobalt and boron powders has been analysed. As a result iron-iron boride, Fe-Fe 2 B and iron/cobalt boride with a slight admixture of molybdenum, Fe - Co - (FeMoCo) 2 B cermets have been produced. Iron was introduced to the mixture as the Astalloy Mo Hoeganaes grade powder. Elemental amorphous boron powder was used, and formation of borides occurred both during heating and isothermal sintering periods causing dimensional changes of the sintered body. Dilatometry was chosen to control basic phenomena taking place during multiphase sintering of investigated systems. The microstructure and phase constituents of sintered compacts were controlled as well. The cermets produced were substituted to: metallographic tests, X-ray analysis, measurements of hardness and of microhardness, and of wear in the process of sliding dry friction. Cermets are made up of two phases; hard grains of iron - cobalt boride, (FeCo) 2 B (1800 HV) constituting the reinforcement and a relatively soft and plastic eutectic mixture Fe 2 B - Co (400-500 HV) constituting the matrix. (author)
5. Nanosize boride particles in heat-treated nickel base superalloys
International Nuclear Information System (INIS)
Zhang, H.R.; Ojo, O.A.; Chaturvedi, M.C.
2008-01-01
Grain boundary microconstituents in aged nickel-based superalloys were studied by transmission electron microscopy techniques. A nanosized M 5 B 3 boride phase, possibly formed by intergranular solute desegregation-induced precipitation, was positively identified. The presence of these intergranular nanoborides provides reasonable clarification of a previously reported reduction of grain boundary liquation temperature during the weld heat affected zone thermal cycle
6. Bonding and doping of simple icosahedral-boride semiconductors
International Nuclear Information System (INIS)
Emin, David
2004-01-01
A simple model of the bonding and doping of a series of icosahedral-boride insulators is presented. Icosahedral borides contain clusters of boron atoms that occupy the 12 vertices of icosahedra. This particular series of icosahedral borides share both the stoichiometry B 12 X 2 , where X denotes a group V element (P or As), and a common lattice structure. The inter-icosahedral bonding of these icosahedral borides is contrasted with that of B 12 O 2 and with that of α-rhombohedral boron. Knowledge of the various types of inter-icosahedral bonding is used as a basis to address effects of inter-icosahedral atomic substitutions. The inter-icosahedral bonding is maintained when an atom of a group V element is replaced with an atom of a group IV element, thereby producing a p-type dopant. However, changes of inter-icosahedral bonding occur upon replacing an atom of a group V element with an atom of a group VI element or with a vacancy. As a result, these substitutions do not produce effective n-type dopants. Moreover, partial substitution of boron atoms for atoms of group V elements generally renders these materials p-type semiconductors
7. Subminiature eddy current transducers for studying boride coatings
Science.gov (United States)
Dmitriev, S. F.; Ishkov, A. V.; Malikov, V. N.; Sagalakov, A. M.
2016-07-01
Strengthening of parts and units of machines, increased reliability and longer service life is an important task of modern mechanical engineering. The main objects of study in the work were selected steel 65G and 50HGA, wear-resistant boride coatings ternary system Fe-B-Fe n B which were investigated by scanning electron microscopy and eddy-current nondestructive methods.
8. Borides and vitreous compounds sintered as high-energy fuels
International Nuclear Information System (INIS)
Mota, J.M.; Abenojar, J.; Martinez, M.A.; Velasco, F.; Criado, A.J.
2004-01-01
Boron was chosen as fuel in view of its excellent thermodynamic values for combustion, as compared to traditional fuels. The problem of the boron in combustion is the formation of a surface layer of oxide, which delays the ignition process, reducing the performance of the rocket engine. This paper presents a high-energy fuel for rocket engines. It is composed of sintered boron (borides and carbides and vitreous compounds) with a reducing chemical agent. Borides and boron carbide were prepared since the combustion heat of the latter is similar to that of the amorphous boron (in: K.K. Kuo (Ed.), Boron-Based Solid Propellant and Solid Fuel, Vol. 427, CRC Press, Boca Raton, FL, 1993). Several chemical reducing elements were used, such as aluminum, magnesium, and coke. As the raw material for boron, different compounds were used: amorphous boron, boric acid and boron oxide
9. Catalytic activity of metal borides in the reaction of decomposition
International Nuclear Information System (INIS)
Labodi, I.; Korablev, L.I.; Tavadyan, L.A.; Blyumberg, Eh.A.
1982-01-01
Catalytic effect of CoB, MoB 2 , ZrB 2 and NbB 2 , prepared by the method of self-propagating high-temperature synthesis, on decomposition of tertiary butyl hydroperoxide has been studied. A technigue of determination of action mechanism of heterogeneous catalysts in liquid-phase process is suggested. It is established that CoB in contrast to other metal borides catalyzes only hydroperoxide decomposition into radicals
10. Novel boride base cermets with very high strength
International Nuclear Information System (INIS)
Ken-ichi Takagi; Mari Yonetsu; Yuji Yamasaki
2001-01-01
Mo 2 NiB 2 boride base cermets consist of a Mo 2 NiB 2 type complex boride as a hard phase and a Ni base binder. The addition of Cr and V to the cermets changed the boride structure from orthorhombic to tetragonal and resulted in the improvement of mechanical properties and microstructural refinement. The tetragonal Mo 2 NiB 2 was formed through the orthorhombic Mo 2 NiB 2 by the solid state reaction during sintering and not formed directly from the raw material powders. Ni-4.5B-46.9Mo-12.5V-xMn (wt.%) model cermets with five levels of Mn content from 0 to 10 wt.% were prepared to investigate the effects of Mn on the mechanical properties and microstructure Of Mo 2 NiB 2 base cermets. The transverse rupture strength (TRS) of the cermets depended strongly on the microstructure, which varied significantly with Mn content. The maximum TRS obtained at 2.5 wt.%Mn were 3.5 Gpa with hardness of 87 R A . (author)
11. Characterization and diffusion model for the titanium boride layers formed on the Ti6Al4V alloy by plasma paste boriding
Energy Technology Data Exchange (ETDEWEB)
Keddam, Mourad, E-mail: [email protected] [Laboratoire de Technologie des Matériaux, Faculté de Génie Mécanique et Génie des Procédés, USTHB, B.P. No. 32, 16111 El-Alia, Bab-Ezzouar, Algiers (Algeria); Taktak, Sukru [Metallurgical and Materials Engineering, Faculty of Technology, Afyon Kocatepe University, ANS Campus, 03200, Afyonkarahisar (Turkey)
2017-03-31
Highlights: • Titanium boride layers were produced by plasma paste boriding on Ti6Al4V at 973–1073 K. • Formation rates of the Ti boride layers have parabolic character at all temperatures. • Boron diffusivities were estimated using a diffusion model including incubation times. • Activation energies of boron in TiB{sub 2} and TiB were 136 and 63 kJ/mol respectively. - Abstract: The present study is focused on the estimation of activation energy of boron in the plasma paste borided Ti6Al4V alloy, which is extensively used in technological applications, using an analytical diffusion model. Titanium boride layers were successfully produced by plasma paste boriding method on the Ti6Al4V alloy in the temperature range of 973–1073 K for a treatment time ranging from 3 to 7 h. The presence of both TiB{sub 2} top-layer and TiB whiskers sub-layer was confirmed by the XRD analysis and SEM observations. The surface hardness of the borided alloy was evaluated using Micro-Knoop indenter. The formation rates of the TiB{sub 2} and TiB layers were found to have a parabolic character at all applied process temperatures. A diffusion model was suggested to estimate the boron diffusivities in TiB{sub 2} and TiB layers under certain assumptions, by considering the effect of boride incubation times. Basing on own experimental data on boriding kinetics, the activation energies of boron in TiB{sub 2} and TiB phases were estimated as 136.24 ± 0.5 and 63.76 ± 0.5 kJ mol{sup −1}, respectively. Finally, the obtained values of boron activation energies for Ti6Al4V alloy were compared with the data available in the literature.
12. Plasma boriding of a cobalt–chromium alloy as an interlayer for nanostructured diamond growth
Energy Technology Data Exchange (ETDEWEB)
Johnston, Jamin M.; Jubinsky, Matthew; Catledge, Shane A., E-mail: [email protected]
2015-02-15
Highlights: • Metal-boride layer creates a compatible surface for NSD deposition. • PECVD boriding on CoCrMo produces robust metal-boride layer. • Deposition temperature comparison shows 750 °C boriding masks surface cobalt. • EDS shows boron diffusion as well as deposition. • Nanoindentation hardness of CoCrMo substantially increases after boriding. - Abstract: Chemical vapor deposited (CVD) diamond coatings can potentially improve the wear resistance of cobalt–chromium medical implant surfaces, but the high cobalt content in these alloys acts as a catalyst to form graphitic carbon. Boriding by high temperature liquid baths and powder packing has been shown to improve CVD diamond compatibility with cobalt alloys. We use the microwave plasma-enhanced (PE) CVD process to deposit interlayers composed primarily of the borides of cobalt and chromium. The use of diborane (B{sub 2}H{sub 6}) in the plasma feedgas allows for the formation of a robust boride interlayer for suppressing graphitic carbon during subsequent CVD of nano-structured diamond (NSD). This metal–boride interlayer is shown to be an effective diffusion barrier against elemental cobalt for improving nucleation and adhesion of NSD coatings on a CoCrMo alloy. Migration of elemental cobalt to the surface of the interlayer is significantly reduced and undetectable on the surface of the subsequently-grown NSD coating. The effects of PECVD boriding are compared for a range of substrate temperatures and deposition times and are evaluated using glancing-angle X-ray diffraction (XRD), cross-sectional scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and micro-Raman spectroscopy. Boriding of CoCrMo results in adhered nanostructured diamond coatings with low surface roughness.
13. Evaluation of High Temperature Particle Erosion Resistance of Vanadium-Boride Coating
International Nuclear Information System (INIS)
Lee, E. Y.; Kim, J. H.; Jeong, S. I.; Lee, S. H.; Eum, G. W.
2015-01-01
The components in ultra super critical (USC) steam turbine, which is under development for high efficient power generation, are encountering harsher solid particle erosion by iron oxide scales than ones in the existing steam turbines. Therefore, the currently used boride coating will not be able to hold effective protection from particle erosion in USC system and should be replaced by new particle erosion resistant coatings. One of the best protective coatings developed for USC steam turbine parts was found to be vanadium-boride (V-boride) coating which has a hardness of about 3000 HV, much higher than that of boride, 1600∼2000 HV. In order to evaluate particle erosion resistance of the various coatings such as V-boride, boride and Cr-carbide coatings at high temperature, particle erosion test equipment were designed and manufactured. In addition, erosion particle velocity was simulated using FLUENT software based on semi-implicity method for pressure linked equations revised (SIMPLER). Based on experimental results of this work, the vanadium-boride coating was found to be superior to others and to be a candidate coating to replace the boride coating
14. Evaluation of High Temperature Particle Erosion Resistance of Vanadium-Boride Coating
Energy Technology Data Exchange (ETDEWEB)
Lee, E. Y.; Kim, J. H.; Jeong, S. I. [Andong National University, Andong (Korea, Republic of); Lee, S. H.; Eum, G. W. [Corporate R and D Institute Doosan Heavy Industries and Construction Co., Changwon (Korea, Republic of)
2015-04-15
The components in ultra super critical (USC) steam turbine, which is under development for high efficient power generation, are encountering harsher solid particle erosion by iron oxide scales than ones in the existing steam turbines. Therefore, the currently used boride coating will not be able to hold effective protection from particle erosion in USC system and should be replaced by new particle erosion resistant coatings. One of the best protective coatings developed for USC steam turbine parts was found to be vanadium-boride (V-boride) coating which has a hardness of about 3000 HV, much higher than that of boride, 1600∼2000 HV. In order to evaluate particle erosion resistance of the various coatings such as V-boride, boride and Cr-carbide coatings at high temperature, particle erosion test equipment were designed and manufactured. In addition, erosion particle velocity was simulated using FLUENT software based on semi-implicity method for pressure linked equations revised (SIMPLER). Based on experimental results of this work, the vanadium-boride coating was found to be superior to others and to be a candidate coating to replace the boride coating.
15. Standard entropy for borides of non-transition metals, rare-earth metals and actinides
International Nuclear Information System (INIS)
Borovikova, M.S.
1986-01-01
Using as initial data the most reliable values of standard entropy for 10 compounds, the entropies for 40 compounds of non-transition metals, rare-earth metals and actinides have been evaluated by the method of comparative calculation. Taking into account the features of boride structures, two methods, i.e. additive and proportional, have been selected for the entropy calculations. For the range of borides the entropies were calculated from the linear relation of the latter to the number of boron atoms in the boride. For borides of rare-earth metals allowance has been made for magnetic contributions in conformity with the multiplicity of the corresponding ions. Insignificant differences in the electronic contributions to the entropy for borides and metals have been neglected. For dodecaborides only the additive method has been used. This is specified by the most rigid network that provides the same contribution to compound entropy. (orig.)
16. Some mechanical properties of borided AISI H13 and 304 steels
International Nuclear Information System (INIS)
Taktak, Sukru
2007-01-01
In the present study, mechanical properties of borides formed on AISI H13 hot work tool and AISI 304 stainless steels have been investigated. Both steels have high chromium content and have a widespread use in the engineering application. Boriding treatment was carried out in slurry salt bath consisting of borax, boric acid, and ferrosilicon at temperature range of 800-950 deg. C for 3, 5, and 7 h. X-ray diffraction analysis of boride layers on the surface of steels revealed various peaks of FeB, Fe 2 B, CrB, and Ni 3 B. Metallographic studies showed that the boride layer has a flat and smooth morphology in the 304 steel while H13 steel was a ragged morphology. The characterization of the boride layer is also carried out by means of the micro-hardness, surface roughness, adhesion, and fracture toughness studies
17. Borides - a new generation of highly resistant materials?
International Nuclear Information System (INIS)
Telle, R.
1988-01-01
High-duty ceramics are on advance in all sectors where materials with extremely good resistance to high temperatures and wear are required. The group of oxides, nitrides and carbides in use for quite a time now recently has been increased by the metal borides which offer among others economic advantages in certain applications. The drawbacks of these materials still to be reduced are their brittleness and susceptibility to oxidation and corrosion. Current research work on the thermodynamics of such systems, on the interaction between structure and properties, and on means to improve strength and resistance to wear are expected to soon open up new applications. (orig.) [de
18. Transition metal borides. Synthesis, characterization and superconducting properties
Energy Technology Data Exchange (ETDEWEB)
Kayhan, Mehmet
2013-07-12
A systematic study was done on the synthesis and superconducting properties of metal rich transition metal borides. Five different binary systems were investigated including the boride systems of niobium, tantalum, molybdenum, tungsten and rhenium. High temperature solid state methods were used in order to synthesize samples of different transition metal borides of the composition M{sub 2}B, MB, M{sub 3}B{sub 2}, MB{sub 2}, and M{sub 2}B{sub 4}. The reactions were carried out in three different furnaces with different sample containers: the electric arc (copper crucible), the high frequency induction furnace (boron nitride, tantalum or glassy carbon crucibles), and the conventional tube furnace (sealed evacuated quartz ampoules). The products obtained were characterized with X-ray powder diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Phase analyses and crystal structure refinements using the Rietveld method and based on structure models known from literature were performed. A neutron diffraction measurement was done for W{sub 2}B{sub 4} to allow for a complete crystal structure determination, because of the presence of a heavy element like tungsten and a light element like boron that made it difficult to determine the accurate determination of the boron atom positions and occupancies from X-ray data. A new structure model for W{sub 2}B{sub 4} was proposed. Magnetic measurements in a SQUID magnetometer down to temperatures as low as 1.8 K were performed to several of the products in order to see if the transition metal borides become superconducting at low temperatures, and the results were compared with data from literature. Superconducting properties were found for the following compounds: NbB{sub 2} (T{sub C} = 3.5 K), β-MoB (T{sub C} = 2.4 K), β-WB (T{sub C} = 2.0 K), α-WB (T{sub C} = 4.3 K), W{sub 2}B{sub 4} (T{sub C} = 5.4 K), Re{sub 7}B{sub 3} (T{sub C} = 2.4 K). A relationship between the superconducting properties
19. Deposition and characterization of aluminum magnesium boride thin film coatings
Science.gov (United States)
Tian, Yun
Boron-rich borides are a special group of materials possessing complex structures typically comprised of B12 icosahedra. All of the boron-rich borides sharing this common structural unit exhibit a variety of exceptional physical and electrical properties. In this work, a new ternary boride compound AlMgB14, which has been extensively studied in bulk form due to its novel mechanical properties, was fabricated into thin film coatings by pulsed laser deposition (PLD) technology. The effect of processing conditions (laser operating modes, vacuum level, substrate temperature, and postannealing, etc.) on the composition, microstructure evolution, chemical bonding, and surface morphology of AlMgB14 thin film coatings has been investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectrometry; the mechanical, electrical, and optical properties of AlMgB14 thin films have been characterized by nanoindentation, four-point probe, van der Pauw Hall measurement, activation energy measurement, and UV-VIS-NIR spectrophotometer. Experimental results show that AlMgB14 films deposited in the temperature range of 300 K - 873 K are amorphous. Depositions under a low vacuum level (5 x 10-5 Torr) can introduce a significant amount of C and O impurities into AlMgB14 films and lead to a complex oxide glass structure. Orthorhombic AlMgB14 phase cannot be obtained by subsequent high temperature annealing. By contrast, the orthorhombic AlMgB 14 crystal structure can be attained via high temperature-annealing of AlMgB14 films deposited under a high vacuum level (boride films, high vacuum level-as deposited AlMgB14 films also possess a low n-type electrical resistivity, which is a consequence of high carrier concentration and moderate carrier mobility. The operative electrical transport mechanism and doping behavior for high vacuum level-as deposited AlMgB14
20. Transition metal borides. Synthesis, characterization and superconducting properties
International Nuclear Information System (INIS)
Kayhan, Mehmet
2013-01-01
A systematic study was done on the synthesis and superconducting properties of metal rich transition metal borides. Five different binary systems were investigated including the boride systems of niobium, tantalum, molybdenum, tungsten and rhenium. High temperature solid state methods were used in order to synthesize samples of different transition metal borides of the composition M 2 B, MB, M 3 B 2 , MB 2 , and M 2 B 4 . The reactions were carried out in three different furnaces with different sample containers: the electric arc (copper crucible), the high frequency induction furnace (boron nitride, tantalum or glassy carbon crucibles), and the conventional tube furnace (sealed evacuated quartz ampoules). The products obtained were characterized with X-ray powder diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Phase analyses and crystal structure refinements using the Rietveld method and based on structure models known from literature were performed. A neutron diffraction measurement was done for W 2 B 4 to allow for a complete crystal structure determination, because of the presence of a heavy element like tungsten and a light element like boron that made it difficult to determine the accurate determination of the boron atom positions and occupancies from X-ray data. A new structure model for W 2 B 4 was proposed. Magnetic measurements in a SQUID magnetometer down to temperatures as low as 1.8 K were performed to several of the products in order to see if the transition metal borides become superconducting at low temperatures, and the results were compared with data from literature. Superconducting properties were found for the following compounds: NbB 2 (T C = 3.5 K), β-MoB (T C = 2.4 K), β-WB (T C = 2.0 K), α-WB (T C = 4.3 K), W 2 B 4 (T C = 5.4 K), Re 7 B 3 (T C = 2.4 K). A relationship between the superconducting properties and the compositional and structural features was discussed for metal diborides. Also it was
1. Anisotropic elastic and thermal properties of titanium borides by first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Sun, Liang; Gao, Yimin [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Xiao, Bing [Department of Physics and Quantum Theory Group, School of Science and Engineering, Tulane University, New Orleans, LA 70118 (United States); Li, Yefei, E-mail: [email protected] [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Guoliang [State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China)
2013-12-05
Highlights: •Elastic properties of titanium borides are calculated by first principles calculation. •Thermodynamical stability of titanium borides is analyzed. •Heat capacity and thermal expansion coefficient for titanium borides are calculated and compared. •Grüneisen parameters of titanium borides are calculated. -- Abstract: The anisotropic elastic and thermal expansions of the titanium borides (TiB{sub 2}, Ti{sub 3}B{sub 4}, TiB{sub P}nma and TiB{sub F}m3{sup ¯}m) are calculated from first-principles using density functional theory. All borides show different anisotropic elastic properties; the bulk, shear and Young’s moduli are consistent with those determined experimentally. The temperature dependence of thermal expansions is mainly caused by the restoration of thermal energy due to phonon excitations at low temperature. When the temperature is higher than 500 K, the volumetric coefficient is increased linearly by increasing temperature. Meanwhile, the heat capacities of titanium borides are obtained based on the knowledge of thermal expansion coefficient and the elasticity, the calculations are in good agreement with the experiments.
2. Electron momentum distribution and electronic response of ceramic borides
Energy Technology Data Exchange (ETDEWEB)
Heda, N.L. [Department of Pure and Applied Physics, University of Kota, Kota 324005 (India); Meena, B.S.; Mund, H.S. [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India); Sahariya, Jagrati [Department of Physics, Manipal University, Jaipur 303007 (India); Kumar, Kishor [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India); Ahuja, B.L., E-mail: [email protected] [Department of Physics, Mohanlal Sukhadia University, Udaipur 313001 (India)
2017-03-15
Isotropic Compton profiles of transition metal based ceramics TaB and VB have been measured using {sup 137}Cs (661.65 keV) γ-ray Compton spectrometer. The experimental momentum densities are compared with those deduced using linear combination of atomic orbitals (LCAO) with Hartree-Fock (HF), density functional theory (DFT) with Wu-Cohen generalized gradient approximation (WCGGA) and also the hybridization of HF and DFT (namely B3PW and PBE0) schemes. It is found that LCAO-DFT-WCGGA scheme based profiles give an overall better agreement with the experimental data, for both the borides. In addition, we have computed the Mulliken's population (MP) charge transfer data, energy bands, density of states and Fermi surface topology of both the borides using full potential-linearized augmented plane wave (FP-LAPW) and LCAO methods with DFT-WCGGA scheme. Cross-overs of Fermi level by the energy bands corresponding to B-2p and valence d-states of transition metals lead to metallic character in both the compounds. Equal-valence-electron-density profiles and MP analysis suggest more ionic character of VB than that of TaB.
3. A Simple, General Synthetic Route toward Nanoscale Transition Metal Borides.
Science.gov (United States)
Jothi, Palani R; Yubuta, Kunio; Fokwa, Boniface P T
2018-04-01
Most nanomaterials, such as transition metal carbides, phosphides, nitrides, chalcogenides, etc., have been extensively studied for their various properties in recent years. The similarly attractive transition metal borides, on the contrary, have seen little interest from the materials science community, mainly because nanomaterials are notoriously difficult to synthesize. Herein, a simple, general synthetic method toward crystalline transition metal boride nanomaterials is proposed. This new method takes advantage of the redox chemistry of Sn/SnCl 2 , the volatility and recrystallization of SnCl 2 at the synthesis conditions, as well as the immiscibility of tin with boron, to produce crystalline phases of 3d, 4d, and 5d transition metal nanoborides with different morphologies (nanorods, nanosheets, nanoprisms, nanoplates, nanoparticles, etc.). Importantly, this method allows flexibility in the choice of the transition metal, as well as the ability to target several compositions within the same binary phase diagram (e.g., Mo 2 B, α-MoB, MoB 2 , Mo 2 B 4 ). The simplicity and wide applicability of the method should enable the fulfillment of the great potential of this understudied class of materials, which show a variety of excellent chemical, electrochemical, and physical properties at the microscale. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
4. Comparative NMR investigation of the Re-based borides
Science.gov (United States)
Lue, C. S.; Tao, Y. F.; Su, T. H.
2008-07-01
We report a systematic study of the rhenium-based borides, ReB2 , Re7B3 , and Re3B , by means of the B11 nuclear magnetic resonance (NMR) spectroscopy. While Re7B3 and Re3B are superconductors, ReB2 exhibits no superconducting signature but is of current interest due to its superhard mechanical property. Since the major focus of this investigation is their electronic characteristics in the normal states, we performed the measurements at temperatures between 77 and 295 K. For Re7B3 and Re3B , s -character electrons were found to be responsible for the observed B11 NMR Knight shift and spin-lattice relaxation rate (1/T1) . From T1 analysis, we thus deduce the partial Bs Fermi-level density of states (DOS) of both borides. On the other hand, the relaxation rate of ReB2 is mainly associated with p electrons, similar to the cases of OsB2 and RuB2 . In addition, the extracted B2p Fermi-level DOS is in good agreement with the theoretical prediction from band-structure calculations.
5. Characterisation of Wear Resistant Boride Layers on a Tool Steel by Activity Controlled Pack Boronising
DEFF Research Database (Denmark)
Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Somers, Marcel A. J.
2015-01-01
The present work addresses the production and characterisation of iron boride layers by pack boronising of a Vanadis 6 tool steel. The boride layers were produced at 900°C for 2h using different pack compositions in order to obtain a single-phase boride layer. The layers were characterized...... by electron microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, Vickers hardness tests and wear testing with a pin-on-disc tribometer. It was found that the type of boride phases (FeB and/or Fe2B) present in the treated layer can be controlled by changing the boron activity...... by pack boronising for all conditions as compared to the heat treated tool steel....
6. Hard Surface Layers by Pack Boriding and Gaseous Thermo-Reactive Deposition and Diffusion Treatments
DEFF Research Database (Denmark)
Christiansen, Thomas Lundin; Bottoli, Federico; Dahl, Kristian Vinter
2017-01-01
) layers with hardnesses up to 1800 HV. Titanizing of ARNE tool steel results in a surface layer consisting of TiC with a hardness of approximately 4000 HV. Duplex treatments, where boriding is combined with subsequent (TRD) titanizing, result in formation of hard TiB2 on top of a thick layer of Fe......Thermo-reactive deposition and diffusion (TRD) and boriding are thermochemical processes that result in very high surface hardness by conversion of the surface into carbides/nitrides and borides, respectively. These treatments offer significant advantages in terms of hardness, adhesion, tribo...... subjected to TRD (chromizing and titanizing) and boriding treatments. For the steels with low carbon content, chromizing results in surface alloying with chromium, i.e., formation of a (soft) “stainless” surface zone. Steels containing higher levels of carbon form chromium carbide (viz. Cr23C6, Cr7C3...
7. Quantitative electron probe microanalysis of borides in aluminium
International Nuclear Information System (INIS)
Karduck, P.; Schuerhoff, H.J.; Burchard, W.G.
1983-01-01
A procedure for the quantitative analysis of borides in aluminium was introduced. For this purpose the optimal apparative boundary conditions for the EPMA of boron were worked out. With these conditions a satisfactory peak to background ratio of 57 could be achieved for B-Kα-radiation. By application of this method the following conclusion should be drawn concerning the kind of nuclei during grain refinement of aluminium with titanium and boron: For grain refinement of aluminium with titanium and boron in the hypoperitectic region of the binary system Al-Ti TiB 2 -particles in clusters provide the high efficiency of refinement. This entails that the TiB 2 -particles already present in the master alloy remain inert in the melt. Hence, the good efficiency of refinement in this region cannot be attributed to the presence of particles like Al 3 Ti, AlB 2 or (Al, Ti) B 2 . (Author)
8. Synthesis, Structure, and Properties of Refractory Hard-Metal Borides
Science.gov (United States)
Lech, Andrew Thomas
As the limits of what can be achieved with conventional hard compounds, such as tungsten carbide, are nearing reach, super-hard materials are an area of increasing industrial interest. The refractory hard metal borides, such as ReB2 and WB4, offer an increasingly attractive alternative to diamond and cubic boron nitride as a next-generation tool material. In this Thesis, a thorough discussion is made of the progress achieved by our laboratory towards understanding the synthesis, structure, and properties of these extremely hard compounds. Particular emphasis is placed on structural manipulation, solid solution formation, and the unique crystallographic manifestations of what might also be called "super-hard metals".
9. Boron-Based Hydrogen Storage: Ternary Borides and Beyond
Energy Technology Data Exchange (ETDEWEB)
Vajo, John J. [HRL Laboratories, LLC, Malibu, CA (United States)
2016-04-28
DOE continues to seek reversible solid-state hydrogen materials with hydrogen densities of ≥11 wt% and ≥80 g/L that can deliver hydrogen and be recharged at moderate temperatures (≤100 °C) and pressures (≤100 bar) enabling incorporation into hydrogen storage systems suitable for transportation applications. Boron-based hydrogen storage materials have the potential to meet the density requirements given boron’s low atomic weight, high chemical valance, and versatile chemistry. However, the rates of hydrogen exchange in boron-based compounds are thus far much too slow for practical applications. Although contributing to the high hydrogen densities, the high valance of boron also leads to slow rates of hydrogen exchange due to extensive boron-boron atom rearrangements during hydrogen cycling. This rearrangement often leads to multiple solid phases occurring over hydrogen release and recharge cycles. These phases must nucleate and react with each other across solid-solid phase boundaries leading to energy barriers that slow the rates of hydrogen exchange. This project sought to overcome the slow rates of hydrogen exchange in boron-based hydrogen storage materials by minimizing the number of solid phases and the boron atom rearrangement over a hydrogen release and recharge cycle. Two novel approaches were explored: 1) developing matched pairs of ternary borides and mixed-metal borohydrides that could exchange hydrogen with only one hydrogenated phase (the mixed-metal borohydride) and only one dehydrogenated phase (the ternary boride); and 2) developing boranes that could release hydrogen by being lithiated using lithium hydride with no boron-boron atom rearrangement.
10. Thermal properties of zirconium diboride -- transition metal boride solid solutions
Science.gov (United States)
McClane, Devon Lee
This research focuses on the thermal properties of zirconium diboride (ZrB2) based ceramics. The overall goal was to improve the understanding of how different transition metal (TM) additives influence thermal transport in ZrB2. To achieve this, ZrB2 with 0.5 wt% carbon, and 3 mol% of individual transition metal borides, was densified by hot-press sintering. The transition metals that were investigated were: Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, and Re. The room temperature thermal diffusivities of the compositions ranged from 0.331 cm2/s for nominally pure ZrB2 to 0.105 cm2/s for (Zr,Cr)B2 and converged around 0.155cm2/s at higher temperatures for all compositions. Thermal conductivities were calculated from the diffusivities, using temperature-dependent values for density and heat capacity. The electron contribution to thermal conductivity was calculated from measured electrical resistivity according to the Wiedemann-Franz law. The phonon contribution to thermal conductivity was calculated by subtracting the electron contribution from the total thermal conductivity. Rietveld refinement of x-ray diffraction data was used to determine the lattice parameters of the compositions. The decrease in thermal conductivity for individual additives correlated directly to the metallic radius of the additive. Additional strain appeared to exist for additives when the stable TM boride for that metal had different crystal symmetries than ZrB2. This research provided insight into how additives and impurities affect thermal transport in ZrB2. The research potentially offers a basis for future modeling of thermal conductivity in ultra-high temperature ceramics based on the correlation between metallic radius and the decrease in thermal conductivity.
11. Iodine Gas Trapping using Granular Porous Bismuth
Energy Technology Data Exchange (ETDEWEB)
Yang, Jae Hwan; Shin, Jin Myeong; Park, Jang Jin; Park, Geun Il [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Yim, Mansung [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)
2014-05-15
{sup 129}I is a radionuclide with a very long half-life of 1.57 Χ 10{sup 7} years and has negative health effects to the human body. Therefore, the emission of {sup 129}I into the air is closely regulated by the Environmental Protection Agency (EPA). Many methods for trapping gaseous {sup 129}I have been developed thus far, including wet scrubbing and adsorption using silver loaded zeolites. Although wet scrubbing can effectively remove iodine, it suffers from corrosion of the vessel due to high concentration of the scrubbing solution. Silver loaded zeolites also show effectiveness in capturing {sup 129}I gas, yet weak thermal stability of physisorbed iodine remains a challenge. We studied a novel and facile method to trap iodine gas using bismuth. Granular bismuth having many pores was synthesized using bismuth nitrate and polyvinyl alcohol as a bismuth precursor and pore forming agent, respectively. Reaction of iodine and our samples resulted in an iodine capturing capacity of more than 2 times that of the commercial grade silver exchanged zeolite (AgX). Granular porous bismuths synthesized using bismuth nitrate and PVA show a promising performance in capturing iodine gas. The use of bismuth in trapping {sup 129}I gas can reduce the process cost as bismuth is cheap. Further study is going on to improve the mechanical property of granular porous bismuths for their easy handling.
12. Iodine Gas Trapping using Granular Porous Bismuth
International Nuclear Information System (INIS)
Yang, Jae Hwan; Shin, Jin Myeong; Park, Jang Jin; Park, Geun Il; Yim, Mansung
2014-01-01
129 I is a radionuclide with a very long half-life of 1.57 Χ 10 7 years and has negative health effects to the human body. Therefore, the emission of 129 I into the air is closely regulated by the Environmental Protection Agency (EPA). Many methods for trapping gaseous 129 I have been developed thus far, including wet scrubbing and adsorption using silver loaded zeolites. Although wet scrubbing can effectively remove iodine, it suffers from corrosion of the vessel due to high concentration of the scrubbing solution. Silver loaded zeolites also show effectiveness in capturing 129 I gas, yet weak thermal stability of physisorbed iodine remains a challenge. We studied a novel and facile method to trap iodine gas using bismuth. Granular bismuth having many pores was synthesized using bismuth nitrate and polyvinyl alcohol as a bismuth precursor and pore forming agent, respectively. Reaction of iodine and our samples resulted in an iodine capturing capacity of more than 2 times that of the commercial grade silver exchanged zeolite (AgX). Granular porous bismuths synthesized using bismuth nitrate and PVA show a promising performance in capturing iodine gas. The use of bismuth in trapping 129 I gas can reduce the process cost as bismuth is cheap. Further study is going on to improve the mechanical property of granular porous bismuths for their easy handling
13. Oxygen depletion of bismuth molybdates
Energy Technology Data Exchange (ETDEWEB)
Yong, L.K.; Howe, R.F.; Keulks, G.W.; Hall, W.K.
1978-05-01
Pure ..cap alpha..-phase bismuth molybdate (Bi/sub 2/Mo/sub 3/O/sub 12/), which is known to be weakly active for selective oxidation, and pure ..gamma..-phase bismuth molybdate (Bi/sub 2/MoO/sub 6/), which has good activity, were subjected to oxidation-reduction cycles with known amounts of hydrogen and oxygen, at 300/sup 0/-570/sup 0/C and with evacuation steps between treatments. The volume of oxygen consumed during reoxidation was equal to half the hydrogen consumed during the reduction on the ..cap alpha..-phase, which indicated that no hydrogen was retained during reduction. For the ..gamma..-phase, the oxygen consumption was greater than half of the hydrogen consumption and it increased with extent of reduction. The excess oxygen was apparently consumed by filling anion vacancies formed during outgassing subsequent to the reduction step. ESR spectroscopy and temperature-programed oxidation-reduction indicated that lattice oxide ions which bridge between bismuth and molybdenum layers of the koechlinite structure become more labile when the catalyst is in a partially reduced state, and that this effect is greater in the ..gamma..- than the ..cap alpha..-phase. Table and 15 references.
14. Bismuth absorption from sup 205 Bi-labelled pharmaceutical bismuth compounds used in the treatment of peptic ulcer disease
Energy Technology Data Exchange (ETDEWEB)
Dresow, B.; Fischer, R.; Gabbe, E.E.; Wendel, J.; Heinrich, H.C. (Eppendorf University Hospital, Hamburg (Germany))
1992-04-01
The absorption of bismuth from five {sup 205}Bi-labelled pharmaceutically used bismuth compounds was studied in man. From single oral doses of all compounds under investigation only <0.1% bismuth was absorbed and excreted with the urine. A significantly higher absorption was observed from the colloidal bismuth subcitrate and the basic bismuth gallate than from the basic bismuth salicylate, nitrate and aluminate. No retention of bismuth in the whole body was found from the single dose experiment. The biologic fast-term half-lives of absorbed bismuth were calculated to be 0.12 and 1.5 days. 14 refs., 2 figs., 1 tab.
15. Preparation of boron-rich aluminum boride nanoparticles by RF thermal plasma
Energy Technology Data Exchange (ETDEWEB)
Choi, Sooseok [Inha University, Department of Chemical Engineering and Regional Innovation Center for Environmental Technology of Thermal Plasma (Korea, Republic of); Matsuo, Jiro; Cheng, Yingying [Tokyo Institute of Technology, Department of Environmental Chemistry and Engineering (Japan); Watanabe, Takayuki, E-mail: [email protected] [Kyushu University, Department of Chemical Engineering (Japan)
2013-08-15
Boron-rich compounds of AlB{sub 12} and AlB{sub 10} nanoparticles were synthesized by a radiofrequency thermal plasma. Aluminum and boron raw powders were evaporated in virtue of high enthalpy of the thermal plasma in upstream region, followed by the formation of aluminum boride nanoparticles in the tail region of plasma flame with rapid quenching. A high production rate of aluminum boride was confirmed by the X-ray diffraction measurement in the case of high input power, high boron content in raw material and helium inner gas. Polyhedral nanoparticles of 20.8 nm in mean size were observed by a transmission electron microscope. In the raw powder mixture of aluminum, titanium, and boron, titanium-boride nanoparticles were synthesized preferentially, because the Gibbs free energy for the boridation of titanium is lower than that of aluminum. Since the nucleation temperature of boron is higher than that of aluminum, the condensation of metal monomers onto boron nuclei results in the formation of boron-rich aluminum boride nanoparticles.
16. Some physical properties of the higher borides of molybdenum and tungsten
International Nuclear Information System (INIS)
Koval'chenko, M.S.; Bodrova, L.G.; Nemchenko, V.F.; Kolotun, V.F.
1979-01-01
The temperature dependences of the thermal conductivity, the specific electrical resistance, the thermo-e.m.f. and the magnetic susceptibility, together with the variation of magnetic resistance and of Hall constant with the magnetic field strength at liquid nitrogen temperature and at room temperature, for the higher borides Mo 2 B 5 , MoB 4 , W 2 B 5 and WB 4 were studied. Some features of the physical properties of these metallic borides were established. In contrast with the corresponding metals the higher borides are diamagnetic and the Hall constants are negative. The values of the magnetic susceptibility and the Hall constant are larger for the higher borides than for the low borides. As the temperature increased an inversion of the thermo-e.m.f. sign took place and the signs of the thermo-e.m.f. and the Hall constant are different. The values of the magnetic susceptibility of Mo 2 B 5 , MoB 4 and WB 4 were temperature independent. The electronic structure of the compounds studied is discussed briefly. (Auth.)
17. Characterization and wear performance of boride phases over tool steel substrates
Directory of Open Access Journals (Sweden)
Edgar E Vera Cárdenas
2016-02-01
Full Text Available This research work was conducted to characterize boride phases, obtained from the powder-pack process, on AISI H13 and D2 steel substrates, and investigate their tribological behavior. The boriding was developed at a temperature of 1273 K with an exposure time of 8 h. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were conducted on the borided material to characterize the presence of the FeB, Fe2B, and CrB phases and the distribution of heavy elements on the surface of the substrates. The adherence of the boride layers was evaluated, in a qualitative form, through the Daimler-Benz Rockwell-C indentation technique. Sliding wear tests were then performed using a reciprocating wear test machine. All tests were conducted in dry conditions at room temperature. A frequency of 10 Hz and 15-mm sliding distance were used. The applied Hertzian pressure was 2.01 GPa. Scanning electron microscopy was used to observe and analyze the wear mechanisms. Additionally, the variation of the friction coefficient versus the number of cycles was obtained. Experimental results showed that the characteristic wear mechanism for the borided surface was plastic deformation and mild abrasive wear; for unborided substrates, cracking and spalling were observed.
18. Study of microcracks morphology produced by Vickers indentation on AISI 1045 borided steels
International Nuclear Information System (INIS)
Campos, I.; Ramirez, G.; VillaVelazquez, C.; Figueroa, U.; Rodriguez, G.
2008-01-01
In this work, we analyzed the roughness morphology of indentation microcracks produced by the Vickers microindentation in the iron boride Fe 2 B. Using the paste boriding process, the boride layers were formed at the surface of AISI 1045 steels. The diffusion processes were carried out with 5 mm of boron paste thickness over the substrate surface at three different temperatures (1193, 1223 and 1273 K) with two different time exposures. The indentations in each Fe 2 B layer were made using a constant load of 200 g at four different distances from the surface. The fracture behavior of the Fe 2 B borided phase is found to be brittle in nature. The profiles of microcracks formed at the corners of the indentations were obtained using the scanning electronic microscopy and were analyzed within the framework of fractal geometry. We found that all indentation microcracks display a self-affine invariance characterized by the same roughness (Hurst) exponent H = 0.8 ± 0.1. The effect of the self-affine roughness of indentation microcracks on the measured fracture toughness is discussed within the framework of the mechanics of self-affine cracks. It is pointed out that the arrest of indentation microcracks is controlled by the fractal fracture toughness, which for the Fe 2 B borided phase is found to be K fc = 0.42 ± 0.02 MPa m 0.75 at all distances from the surface
19. Quantitative electron probe microanalysis of boron in binary borides
International Nuclear Information System (INIS)
Bastin, G.F.; Heijligers, H.J.M.
1986-01-01
Quantitative electron probe microanalysis has been performed in 27 binary borides in the range of 4-30 keV, both for the metals as well as for Boron. The procedures along which accurate intensity measurements for B-K α must be carried out are discussed in detail. A total of 196 k-ratios with respect to elemental standards for the metal X-ray lines and 180 k-ratios for B-K α relative to elemental Boron have been obtained. These data have been used to arrive at an improved parameterization for the φ(ρz) approach in matrix correction. The resulting new program (BAS861) was compared to 5 other current correction programs. At the same occasion the available set of mass absorption coefficients for Boron was tested on its consistency and better values suggested where necessary. Finally it is shown that the modified version of the Gaussian φ(ρz) approach (BAS861 program) is highly successful in the matrix correction for B-K α : a relative root-mean-square value of 6.30% was obtained. (Auth.)
20. Bismuth ions are metabolized into autometallographic traceable bismuth-sulphur quantum dots
Directory of Open Access Journals (Sweden)
M Stoltenberg
2009-06-01
Full Text Available Bismuth – sulphur quantum dots can be silver enhanced by autometallography (AMG. In the present study, autometallographic silver enhanced bismuth-sulphur nanocrystals were isolated from unfixed cryo-sections of kidneys and livers of rats exposed to bismuth (Bi207 subnitrate. After being subjected to AMG all the organic material was removed by sonication and enzymatic digestion and the silver enhanced Bi- S quantum dots spun down by an ultracentrifuge and analyzed by scintillation. The analysis showed that the autometallographic technique traces approximately 94% of the total bismuth. This implies that the injected bismuth is ultimately captured in bismuthsulphur quantum dots, i.e., that Bi-S nanocrystals are the end product of bismuth metabolism
1. The influence of bismuth oxide doping on the rechargeability of aqueous cells using MnO2 cathode and LiOH electrolyte
International Nuclear Information System (INIS)
Minakshi, Manickam; Mitchell, David R.G.
2008-01-01
Bi-doped manganese dioxide (MnO 2 ) has been prepared from γ-MnO 2 by physical admixture of bismuth oxide (Bi 2 O 3 ). The doping improved the cycling ability of the aqueous cell. These results are discussed and compared with the electrochemical behavior of bismuth-free MnO 2 . Batteries using the traditional potassium hydroxide (KOH) electrolyte are non-rechargeable. However, with lithium hydroxide (LiOH) as an electrolyte, the cell becomes rechargeable. Furthermore, the incorporation of bismuth into MnO 2 in the LiOH cell was found to result in significantly longer cycle life, compared with cells using undoped MnO 2 . The Bi-doped cell exhibited a greater capacity after 100 discharge cycles, than the undoped cell after just 40 cycles. X-ray diffraction and the microscopic analysis suggest that the presence of Bi 3+ ions reduces the magnitude of structural changes occurring in MnO 2 during cycling. Comparison with additives assessed in our previous studies (titanium disulfide (TiS 2 ); titanium boride (TiB 2 )) shows that the best rechargeability behavior is obtained for the current Bi-doped MnO 2 . As the size of Bi 3+ ions (0.96 A) is much larger than Mn 3+ (0.73 A) or Mn 2+ (0.67 A) they have effectively prevented the formation of non-rechargeable products
2. Metal Immiscibility Route to Synthesis of Ultrathin Carbides, Borides, and Nitrides.
Science.gov (United States)
Wang, Zixing; Kochat, Vidya; Pandey, Prafull; Kashyap, Sanjay; Chattopadhyay, Soham; Samanta, Atanu; Sarkar, Suman; Manimunda, Praveena; Zhang, Xiang; Asif, Syed; Singh, Abhisek K; Chattopadhyay, Kamanio; Tiwary, Chandra Sekhar; Ajayan, Pulickel M
2017-08-01
Ultrathin ceramic coatings are of high interest as protective coatings from aviation to biomedical applications. Here, a generic approach of making scalable ultrathin transition metal-carbide/boride/nitride using immiscibility of two metals is demonstrated. Ultrathin tantalum carbide, nitride, and boride are grown using chemical vapor deposition by heating a tantalum-copper bilayer with corresponding precursor (C 2 H 2 , B powder, and NH 3 ). The ultrathin crystals are found on the copper surface (opposite of the metal-metal junction). A detailed microscopy analysis followed by density functional theory based calculation demonstrates the migration mechanism, where Ta atoms prefer to stay in clusters in the Cu matrix. These ultrathin materials have good interface attachment with Cu, improving the scratch resistance and oxidation resistance of Cu. This metal-metal immiscibility system can be extended to other metals to synthesize metal carbide, boride, and nitride coatings. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
3. Hardness optimization of boride diffusion layer on Astm F-75 alloy using response surface methodology
Energy Technology Data Exchange (ETDEWEB)
Arguelles O, J. L.; Corona R, M. A. [Universidad Autonoma de San Luis Potosi, Doctorado Institucional en Ingenieria y Ciencia de Materiales, San Luis Potosi 78000, SLP (Mexico); Marquez H, A.; Saldana R, A. L.; Saldana R, A. [Universidad de Guanajuato, Ingenieria Mecanica Agricola DICIVA, Irapuato, Guanajuato 36500 (Mexico); Moreno P, J., E-mail: [email protected] [Universidad de Guanajuato, Departamento de Minas, Metalurgia y Geologia, Ex-Hacienda San Matias s/n, Guanajuato, Guanajuato 36020 (Mexico)
2017-11-01
In this study, the Response Surface Methodology (Rsm) and Central Composite Design (Ccd) were used to optimize the hardness of boride diffusion layer on Astm F-75 alloy (also called Haynes alloy). A boronizing thermochemical treatment was carried out at different temperatures and for different time periods. Hardness tests were conducted. The boride diffusion layer was verified by the X-ray diffraction (XRD) analysis indicating the formation of Co B, Co{sub 2}B, Cr B and Mo{sub 2}B phases. An optimal hardness of 3139.7 Hv was obtained for the samples subjected to the boriding process for a duration of 6.86 h at 802.4 degrees Celsius. (Author)
4. Wear behavior of tempered and borided tool steels under various conditions
International Nuclear Information System (INIS)
Al-Haidary, T. J.; Faleh, M. N.
2000-01-01
. Tool steel 61CrV5, 50 NiCr13 and X1000Cr MoV51 were used in the first stage of this investigation. They have been treated as follows: boriding, boriding and tempering and hardening and tempering. The wear tests were conducted under fixed conditions (150 N/mm 2 , 0.48m/sec) with and without lubricant. The wear rate and coefficient of friction of 61Cr Si V5 steel have been studied in the second stage hoping to find the influence of working conditions on these parameters and then to compare these results with the case of hardening and tempering which is the usual case in the actual working field. The study gives a good indication about the improvement achieved in boriding and tempering cases (∼ 30%) as compared with hardening tempering cases in dry sliding conditions -∼5% with lubricating ones. (authors). 13 refs., 19 figs., 1 table
5. The effect of boriding on wear resistance of cold work tool steel
International Nuclear Information System (INIS)
Anzawa, Y; Koyama, S; Shohji, I
2017-01-01
Recently, boriding has attracted extensive attention as surface stiffening processing of plain steel. In this research, the influence of processing time on the formation layer of cold work tool steel (KD11MAX) by Al added fused salt bath was examined. In addition, in order to improve the abrasion resistance of KD11MAX, the effect of the treatment of boronization on the formation layer has been investigated. Boriding were performed in molten borax which contained about 10 mass% Al at processing time of 1.8 ∼ 7.2 ks (processing temperature of 1303 K). As a result of the examination, the hardness of the boriding layer becomes about 1900 HV when the processing time of 3.6 ks. Also the abrasion resistance has improved remarkably. Furthermore, it was revealed that the formation layer was boronized iron from the Vickers hardness and analysis of the X-ray diffraction measurement. (paper)
6. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition
Energy Technology Data Exchange (ETDEWEB)
Johnston, Jamin M.; Catledge, Shane A., E-mail: [email protected]
2016-02-28
Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W{sub 2}CoB{sub 2}. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W{sub 2}CoB{sub 2} with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.
7. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition
International Nuclear Information System (INIS)
Johnston, Jamin M.; Catledge, Shane A.
2016-01-01
Graphical abstract: - Highlights: • A detailed phase analysis after PECVD boriding shows WCoB, CoB and/or W_2CoB_2. • EDS of PECVD borides shows boron diffusion into the carbide grain structure. • Nanoindentation hardness and modulus of borides is 23–27 GPa and 600–780 GPa. • Scratch testing shows hard coating with cracking at 40N and spallation at 70N. - Abstract: Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W_2CoB_2 with average hardness from 23 to 27 GPa and average elastic modulus of 600–730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.
8. Boride-based nano-laminates with MAX-phase-like behaviour
International Nuclear Information System (INIS)
Telle, Rainer; Momozawa, Ai; Music, Denis; Schneider, Jochen M.
2006-01-01
MAX-phases being usually composed of transition metals, group A elements and carbon/nitrogen are considered interesting materials for many applications because of their tremendous bulk modulus, 'reversible' plasticity, and machinability. This is mainly due to their unique kind of bonding comprising covalent, ionic as well as metallic bonds providing 'easy' planes of rupture and deformability due to the layered crystal structures. In transition metal boride systems, similar types of bonding are available. In particular the W 2 B 5 -structure type and its stacking variations allow the synthesis of strongly layered crystal structures exhibiting unique delamination phenomena. The paper presents ab initio calculations showing the similarities of bonding between the ternary carbides and the corresponding ternary or quaternary borides. Formation of boride-based nano-laminates from auxiliary liquid phases, from the melt as well as during sintering and precipitation from supersaturated solid solutions will be discussed by means of SEM and TEM studies. The role of impurities weakening the interlayer bonding will be addressed in particular. The pronounced cleavage parallel to the basal plane gives rise for crack deflection and pull-out mechanisms if the laminates are dispersed in brittle matrices such as boron carbide, silicon carbide or other transition metal borides. - Graphical abstract: Some transition metal borides crystallise in a layered structure of alternating stacks of metal and boron atoms giving rise for strongly anisotropic properties. Their preferred cleavage parallel and the deformability perpendicular to the basal plan are similar to the peculiar mechanical behaviour recently described for MAX-phases. Ab initio calculations of the crystal structure prove the weak bonds between the layers for a variety of borides which can be used to reinforce ceramic materials on a nano-scale level
9. Gravimetric Analysis of Bismuth in Bismuth Subsalicylate Tablets: A Versatile Quantitative Experiment for Undergraduate Laboratories
Science.gov (United States)
Davis, Eric; Cheung, Ken; Pauls, Steve; Dick, Jonathan; Roth, Elijah; Zalewski, Nicole; Veldhuizen, Christopher; Coeler, Joel
2015-01-01
In this laboratory experiment, lower- and upper-division students dissolved bismuth subsalicylate tablets in acid and precipitated the resultant Bi[superscript 3+] in solution with sodium phosphate for a gravimetric determination of bismuth subsalicylate in the tablets. With a labeled concentration of 262 mg/tablet, the combined data from three…
10. Electrosynthesis of tantalum borides in oxygen-free and oxygen-containing fluoride melts
DEFF Research Database (Denmark)
Polyakova, L.P.; Polyakov, E.G.; Makarova, O.V.
2001-01-01
Results of electrosynthesis of tantalum borides in fluoride and oxyfluoride melts are compared. It is shown that the single-phase X-ray-amorphous micro-layered coatings form only in the latter case. Linear and square-wave voltammetry, complemented by X-ray diffraction analysis, IR spectroscopy...
11. Micro-Abrasion Wear Resistance of Borided 316L Stainless Steel and AISI 1018 Steel
Science.gov (United States)
Reséndiz-Calderon, C. D.; Rodríguez-Castro, G. A.; Meneses-Amador, A.; Campos-Silva, I. E.; Andraca-Adame, J.; Palomar-Pardavé, M. E.; Gallardo-Hernández, E. A.
2017-11-01
The 316L stainless steel has high corrosion resistance but low tribological performance. In different industrial sectors (biomedical, chemical, petrochemical, and nuclear engineering), improvement upon wear resistance of 316L stainless steel components using accessible and inexpensive methods is critical. The AISI 1018 steel is widely used in industry, but its tribological performance is not the best among steels. Therefore, in this study the behavior of the borided 316L stainless steel and 1018 steel is evaluated under micro-abrasion wear. The boriding was carried out at 1223 K over 6 h of exposure time, resulting in a biphase layer composed of FeB/Fe2B phases. In order to evaluate Fe2B phase with no influence from FeB phase, AISI 1018 steel samples were borided at 1273 K for over 20 min and then diffusion annealed at 1273 K over 2 h to obtain a Fe2B mono-phase layer. Micro-abrasion wear resistance was evaluated by a commercial micro-abrasion testing rig using a mix of F-1200 SiC particles with deionized water as abrasive slurry. The obtained wear rates for FeB and Fe2B phases and for the 316L stainless steel were compared. Wear resistance of 316L stainless steel increases after boriding. The wear mechanisms for both phases and for the stainless steel were identified. Also, transient conditions for rolling and grooving abrasion were determined for the FeB and Fe2B phases.
12. Growth kinetics of boride layers formed on 99.0% purity nickel
abrasion wear, corrosion and high oxidation resistance com- pared with other ... Ni and Ni-base alloys are used in various industrial plants and equipment for their high ... with 1000-grit emery paper before the boronizing process. The boriding ...
13. Kinetics of boride layers formed on the surface of AISI 4140 steel
International Nuclear Information System (INIS)
Sen, S.; Sen, U.; Bindal, C.
2004-01-01
The present study reports on boride layer growth kinetics of borided AISI 4140 steel. Steels were boronized in molten borax, boric acid and ferro-silicon bath at 1123 K 1173 K and 1223 K for 2, 4, 6 and 8 hours. Boride layer thickness ranged from 38.4 to 225 μm. Layer growth kinetics were analysed by measuring the extent of penetration of FeB and Fe 2 B sublayers as a function of boronizing time and temperature in the range of 1123-1223 K. The depth of the tips of the most deeply penetrated FeB and Fe 2 B needles are taken as measures for diffusion in the fast directions. The kinetics of the reaction, K=K 0 exp(-Q/RT) have also been determined by varying the boriding temperature and time. The results showed that K increase with boronizing temperature. Activation energy (Q) for present study was determined as 215 kj.mol -1 . The diffusion coefficient (K) ranged from 3 x 10 -9 cm 2 s -1 to 2 x 10 -8 cm 2 s -1 . Also temperature-dependent constant (K 0 ) at temperatures 1123 K, 1173 K and 1223 K was 179.4 cm 2 s -1 . (orig.)
14. Kinetics of boride layers formed on the surface of AISI 4140 steel
Energy Technology Data Exchange (ETDEWEB)
Sen, S.; Sen, U. [Sakarya Univ., Dept. of Metal Education, Sakarya (Turkey); Bindal, C. [Sakarya Univ., Dept. of Materials and Metallurgy, Sakarya (Turkey)
2004-07-01
The present study reports on boride layer growth kinetics of borided AISI 4140 steel. Steels were boronized in molten borax, boric acid and ferro-silicon bath at 1123 K 1173 K and 1223 K for 2, 4, 6 and 8 hours. Boride layer thickness ranged from 38.4 to 225 {mu}m. Layer growth kinetics were analysed by measuring the extent of penetration of FeB and Fe{sub 2}B sublayers as a function of boronizing time and temperature in the range of 1123-1223 K. The depth of the tips of the most deeply penetrated FeB and Fe{sub 2}B needles are taken as measures for diffusion in the fast directions. The kinetics of the reaction, K=K{sub 0} exp(-Q/RT) have also been determined by varying the boriding temperature and time. The results showed that K increase with boronizing temperature. Activation energy (Q) for present study was determined as 215 kj.mol{sup -1}. The diffusion coefficient (K) ranged from 3 x 10{sup -9} cm{sup 2}s{sup -1} to 2 x 10{sup -8} cm{sup 2}s{sup -1}. Also temperature-dependent constant (K{sub 0}) at temperatures 1123 K, 1173 K and 1223 K was 179.4 cm{sup 2}s{sup -1}. (orig.)
15. Additive-assisted synthesis of boride, carbide, and nitride micro/nanocrystals
International Nuclear Information System (INIS)
Chen, Bo; Yang, Lishan; Heng, Hua; Chen, Jingzhong; Zhang, Linfei; Xu, Liqiang; Qian, Yitai; Yang, Jian
2012-01-01
General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. Here, a series of boride (TiB 2 , ZrB 2 , NbB 2 , CeB 6 , PrB 6 , SmB 6 , EuB 6 , LaB 6 ), carbide (SiC, TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN 2 , VN) micro/nanocrystals were prepared from related oxides and amorphous boron/active carbon/NaN 3 with the assistance of metallic Na and elemental S. In-situ temperature monitoring showed that the reaction temperature could increase quickly to ∼850 °C, once the autoclave was heated to 100 °C. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of borides, carbides and nitrides. The as-obtained products were characterized by XRD, SEM, TEM, and HRTEM techniques. Results in this report will greatly benefit the future extension of this approach to other compounds. - Graphical abstract: An additive-assisted approach is successfully developed for the syntheses of borides, carbides and nitrides micro/nanocrystals with the assistance of the exothermic reaction between Na and S. Highlights: ► An additive-assisted synthesis strategy is developed for a number of borides, carbides and nitrides. ► The reaction mechanism is demonstrated by the case of SiC nanowires. ► The formation of SiC nanowires is initiated by the exothermic reaction of Na and S.
16. Short report: evaluation of Helicobacter pylori eradication with bismuth sucralfate
NARCIS (Netherlands)
Reijers, M. H.; Noach, L. A.; Tytgat, G. N.
1994-01-01
In a pilot study we have evaluated the clinical efficacy of bismuth sucralfate to eradicate H. pylori. Ten consecutive patients with chronic dyspepsia and H. pylori associated gastritis were treated with bismuth sucralfate (220 mg bismuth per tablet, 4 tablets per day for 4 weeks). If a 14C urea
17. Ni/boride interfaces and environmental embrittlement in Ni-based superalloys: A first-principles study
International Nuclear Information System (INIS)
Sanyal, Suchismita; Waghmare, Umesh V.; Hanlon, Timothy; Hall, Ernest L.
2011-01-01
Highlights: ► Fracture strengths of Ni/boride interfaces through first-principles calculations. ► Fracture strengths of Ni/boride interfaces are higher than Ni/Ni 3 Al and NiΣ5 grain boundaries. ► Ni/boride interfaces have higher resistance to O-embrittlement than Ni/Ni 3 Al and NiΣ5 grain boundaries. ► CrMo-borides are more effective than Cr-borides in resisting O-embrittlement. ► Electronegativity differences between alloying elements correlate with fracture strengths. - Abstract: Motivated by the vital role played by boride precipitates in Ni-based superalloys in improving mechanical properties such as creep rupture strength, fatigue crack growth rates and improved resistance towards environmental embrittlement , we estimate fracture strength of Ni/boride interfaces through determination of their work of separation using first-principles simulations. We find that the fracture strength of Ni/boride interfaces is higher than that of other commonly occurring interfaces in Ni-alloys, such as Ni Σ-5 grain boundaries and coherent Ni/Ni 3 Al interfaces, and is less susceptible to oxygen-induced embrittlement. Our calculations show how the presence of Mo in Ni/M 5 B 3 (M = Cr, Mo) interfaces leads to additional reduction in oxygen-induced embrittlement. Through Electron-Localization-Function based analyses, we identify the electronic origins of effects of alloying elements on fracture strengths of these interfaces and observe that chemical interactions stemming from electronegativity differences between different atomic species are responsible for the trends in calculated strengths. Our findings should be useful towards designing Ni-based alloys with higher interfacial strengths and reduced oxygen-induced embrittlement.
18. Bismuth titanate nanorods and their visible light photocatalytic properties
International Nuclear Information System (INIS)
Pei, L.Z.; Liu, H.D.; Lin, N.; Yu, H.Y.
2015-01-01
Highlights: • Bismuth titanate nanorods have been synthesized by a simple hydrothermal process. • The size of bismuth titanate nanorods can be controlled by growth conditions. • Bismuth titanate nanorods show good photocatalytic activities of methylene blue and Rhodamine B. - Abstract: Bismuth titanate nanorods have been prepared using a facile hydrothermal process without additives. The bismuth titanate products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and UV-vis diffusion reflectance spectrum. XRD pattern shows that the bismuth titanate nanorods are composed of cubic Bi 2 Ti 2 O 7 phase. Electron microscopy images show that the length and diameter of the bismuth titanate nanorods are 50-200 nm and 2 μm, respectively. Hydrothermal temperature and reaction time play important roles on the formation and size of the bismuth titanate nanorods. UV-vis diffusion reflectance spectrum indicates that bismuth titanate nanorods have a band gap of 2.58 eV. The bismuth titanate nanorods exhibit good photocatalytic activities in the photocatalytic degradation of methylene blue (MB) and Rhodamine B (RB) under visible light irradiation. The bismuth titanate nanorods with cubic Bi 2 Ti 2 O 7 phase are a promising candidate as a visible light photocatalyst
19. Bismuth Subgallate Toxicity in the Age of Online Supplement Use.
Science.gov (United States)
Sampognaro, Paul; Vo, Kathy T; Richie, Megan; Blanc, Paul D; Keenan, Kevin
2017-11-01
Bismuth salts have been used to treat gastroenterological disorders and are readily available over-the-counter and via the internet. Even though generally considered safe, bismuth compounds can cause a syndrome of subacute, progressive encephalopathy when taken in large quantities. We present the case of woman who developed progressive encephalopathy, aphasia, myoclonus, and gait instability after chronically ingesting large amounts of bismuth subgallate purchased from a major online marketing website to control symptoms of irritable bowel syndrome. After extensive neurological work-up, elevated bismuth levels in her blood, urine, and cerebrospinal fluid confirmed the diagnosis of bismuth-related neurotoxicity. She improved slowly following cessation of exposure. This case highlights bismuth subgallate as a neurotoxic bismuth formulation and reminds providers of the potential for safety misconceptions of positively reviewed online supplements.
20. A crossover from high stiffness to high hardness. The case of osmium and its borides
International Nuclear Information System (INIS)
Bian, Yongming; Li, Anhu; Liu, Xiaomei; Shanghai Univ. of Engineering Science; Liang, Yongcheng
2016-01-01
Transition-metal light-element compounds are currently raising great expectations for hard and superhard materials. Using the widely attracting osmium (Os) and its borides (OsB, Os_2B_3 and OsB_2) as prototypes, we demonstrate by first-principles calculations that heavy transition metals, which possess high stiffness but low hardness, can be converted into highly hard materials by incorporating of light elements to form compounds. Such a crossover is a manifestation that the underlying sources of high stiffness and high hardness are fundamentally different. The stiffness is related to elastic deformation that is closely associated with valence electron density, whereas the hardness depends strongly on plastic deformation that is determined by bonding nature. Therefore, the incorporation of light atoms into transition metal should be a valid pathway of designing hard and superhard materials. This strategy is in principle also applicable to other transition-metal borides, carbides, and nitrides.
1. A crossover from high stiffness to high hardness. The case of osmium and its borides
Energy Technology Data Exchange (ETDEWEB)
Bian, Yongming; Li, Anhu [Tongji Univ., Shanghai (China). School of Mechanical Engineering; Liu, Xiaomei [Tongji Univ., Shanghai (China). School of Mechanical Engineering; Shanghai Univ. of Engineering Science (China). College of Mechanical Engineering; Liang, Yongcheng [Shanghai Ocean Univ. (China). College of Engineering Science and Technology
2016-07-01
Transition-metal light-element compounds are currently raising great expectations for hard and superhard materials. Using the widely attracting osmium (Os) and its borides (OsB, Os{sub 2}B{sub 3} and OsB{sub 2}) as prototypes, we demonstrate by first-principles calculations that heavy transition metals, which possess high stiffness but low hardness, can be converted into highly hard materials by incorporating of light elements to form compounds. Such a crossover is a manifestation that the underlying sources of high stiffness and high hardness are fundamentally different. The stiffness is related to elastic deformation that is closely associated with valence electron density, whereas the hardness depends strongly on plastic deformation that is determined by bonding nature. Therefore, the incorporation of light atoms into transition metal should be a valid pathway of designing hard and superhard materials. This strategy is in principle also applicable to other transition-metal borides, carbides, and nitrides.
2. Radio-sensitization of animals by bismuth; Radio sensibilisation de l'animal par le bismuth
Energy Technology Data Exchange (ETDEWEB)
Pierotti, T; Verain, A [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1969-07-01
Digestive absorption of bismuth by animals leads to radio-sensitization. This effect is very marked when the X-rays used are centered on the absorption line of bismuth. This work has involved the use of more than 2000 C3H/JAX mice, and has shown that a maximum lethal effect, with respect to the standard, occurs for bismuth sub-nitrate doses of the order of 3 g/kg and for exposures of 700 R. For stronger or weaker doses, the sensitization effect is less marked. (authors) [French] L'absorption digestive de bismuth provoque une radiosensibilisation de l'animal. Celle-ci est nette quand le rayonnement X utilise est centre sur la raie d'absorption du bismuth. L'etude portant sur plus de 2000 souris C3H/JAX a montre une lethalite maximale par rapport aux temoins pour des doses de sous-nitrate de bismuth de l'ordre de 3 g/kg et pour des expositions de 700 R. Pour des doses plus fortes ou plus faibles, l'effet de sensibilisation est moins net. (auteurs)
3. Preparation of molybdenum borides by combustion synthesis involving solid-phase displacement reactions
International Nuclear Information System (INIS)
Yeh, C.L.; Hsu, W.S.
2008-01-01
Preparation of molybdenum borides of five different phases in the Mo-B binary system (including Mo 2 B, MoB, MoB 2 , Mo 2 B 5 , and MoB 4 ) was performed by self-propagating high-temperature synthesis (SHS) with two kinds of the reactant samples. When elemental powder compacts with an exact stoichiometry corresponding to the boride phase were employed, self-sustaining reaction was only achieved in the sample with Mo:B = 1:1 and nearly single-phase MoB was yielded. Therefore, the other four boride compounds were prepared from the reactant compacts composed of MoO 3 , Mo, and B powders, within which the displacement reaction of MoO 3 with boron was involved in combustion synthesis. Experimental evidence shows that the extent of displacement reaction in the overall reaction has a significant impact on sustainability of the synthesis reaction, combustion temperature, reaction front velocity, and composition of the end product. An increase in the solid-phase displacement reaction taking place during the SHS process contributes more heat flux to the synthesis reaction, thus resulting in the increase of combustion temperature and enhancement of the reaction front velocity. Based upon the XRD analysis, formation of Mo 2 B, MoB 2 , and Mo 2 B 5 as the dominant boride phase in the end product was successful through the SHS reaction with powder compacts under appropriate stoichiometries between MoO 3 , Mo, and B. However, a poor conversion was observed in the synthesis of MoB 4 . The powder compact prepared for the production of MoB 4 yielded mostly Mo 2 B 5
4. 21 CFR 73.2110 - Bismuth citrate.
Science.gov (United States)
2010-04-01
... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Bismuth citrate. 73.2110 Section 73.2110 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL LISTING OF COLOR... paragraph (c)(1), effective April 27, 2010. For the convenience of the user, the revised text is set forth...
5. Magnetoreflection studies of ion implanted bismuth
International Nuclear Information System (INIS)
Nicolini, C.; Chieu, T.C.; Dresselhaus, M.S.; Massachusetts Inst. of Tech., Cambridge; Dresselhaus, G.
1982-01-01
The effect of the implantation of Sb ions on the electronic structure of the semimetal bismuth is studied by the magnetoreflection technique. The results show long electronic mean free paths and large implantation-induced increases in the band overlap and L-point band gap. These effects are opposite to those observed for Bi chemically doped with Sb. (author)
6. Growth kinetics of borided layers: Artificial neural network and least square approaches
Science.gov (United States)
Campos, I.; Islas, M.; Ramírez, G.; VillaVelázquez, C.; Mota, C.
2007-05-01
The present study evaluates the growth kinetics of the boride layer Fe 2B in AISI 1045 steel, by means of neural networks and the least square techniques. The Fe 2B phase was formed at the material surface using the paste boriding process. The surface boron potential was modified considering different boron paste thicknesses, with exposure times of 2, 4 and 6 h, and treatment temperatures of 1193, 1223 and 1273 K. The neural network and the least square models were set by the layer thickness of Fe 2B phase, and assuming that the growth of the boride layer follows a parabolic law. The reliability of the techniques used is compared with a set of experiments at a temperature of 1223 K with 5 h of treatment time and boron potentials of 2, 3, 4 and 5 mm. The results of the Fe 2B layer thicknesses show a mean error of 5.31% for the neural network and 3.42% for the least square method.
7. Structure of superhard tungsten tetraboride: A missing link between MB2 and MB12 higher borides
Science.gov (United States)
Lech, Andrew T.; Turner, Christopher L.; Mohammadi, Reza; Tolbert, Sarah H.; Kaner, Richard B.
2015-01-01
Superhard metals are of interest as possible replacements with enhanced properties over the metal carbides commonly used in cutting, drilling, and wear-resistant tooling. Of the superhard metals, the highest boride of tungsten—often referred to as WB4 and sometimes as W1–xB3—is one of the most promising candidates. The structure of this boride, however, has never been fully resolved, despite the fact that it was discovered in 1961—a fact that severely limits our understanding of its structure–property relationships and has generated increasing controversy in the literature. Here, we present a new crystallographic model of this compound based on refinement against time-of-flight neutron diffraction data. Contrary to previous X-ray–only structural refinements, there is strong evidence for the presence of interstitial arrangements of boron atoms and polyhedral bonding. The formation of these polyhedra—slightly distorted boron cuboctahedra—appears to be dependent upon the defective nature of the tungsten-deficient metal sublattice. This previously unidentified structure type has an intermediary relationship between MB2 and MB12 type boride polymorphs. Manipulation of the fractionally occupied metal and boron sites may provide insight for the rational design of new superhard metals. PMID:25733870
8. Synthesis of borides in molybdenum implanted by B+ ions under thermal and electron annealing
International Nuclear Information System (INIS)
Kazdaev, Kh.R.; Akchulakov, M.T.; Bayadilov, E.M.; Ehngel'ko, V.I.; Lazarenko, A.V.; Chebukov, E.S.
1989-01-01
The possibility of formation of borides in the near surface layers of monocrystalline molybdenum implanted by boron ions at 35 keV energy under thermal and pulsed electron annealing by an electon beam at 140 keV energy is investigated. It is found that implantation of boron ions into molybdenum with subsequent thermal annealing permits to produce both molybdenum monoboride (α-MoB) and boride (γ-Mo 2 B) with rather different formation mechanisms. Formation of the α-MoB phase occurs with the temperature elevation from the centers appeared during implantation, while the γ-Mo 2 B phase appears only on heating the implanted layers up to definite temperature as a result of the phase transformation of the solid solution into a chemical compound. Pulsed electron annealing instead of thermal annealing results mainly in formation of molybdenum boride (γ-Mo 2 B), the state of structure is determined by the degree of heating of implanted layers and their durable stay at temperatures exceeding the threshold values
9. Bismuth( Ⅲ ) Salts: Green Catalysts for Organic Transformations
Institute of Scientific and Technical Information of China (English)
C. Le Roux
2005-01-01
@@ 1Introduction Bismuth, the heaviest stable element in the periodic table, stands out from other heavy elements (such as mercury, thallium and lead) due to its relatively non-toxic character which confers on bismuth the enviable status of being an eco-friendly element. Therefore, bismuth and its compounds hold considerable promise as useful catalysts for green chemistry. The research presented in this communication is devoted to the applications of bismuth( Ⅲ ) salts as catalysts for organic transformations.After some general comments about bismuth and a short presentation of the various applications of bismuth( Ⅲ ) salts in organic synthesis, this communication will focus on the works done in our research group during the last several years which deals mainly with electrophilic substitutions. When appropriate, some mechanistic details will be given.
10. Thermal decomposition synthesis of nanorods bismuth sulphide from bismuth N-ethyl cyclohexyl dithiocarbamate complex
International Nuclear Information System (INIS)
Abdullah, Nurul Hidayah; Zainal, Zulkarnain; Silong, Sidik; Tahir, Mohamed Ibrahim Mohamed; Tan, Kar-Ban; Chang, Sook-Keng
2016-01-01
Highlights: • Bismuth N-ethyl cyclohexyl dithiocarbamate was used as single source precursor. • No surfactant was used in the preparation of Bi_2S_3 nanorods. • Pure phase orthorhombic Bi_2S_3 is obtained. • Bismuth sulphide with an average atomic ratio of Bi:S close to 2:3 is obtained. - Abstract: Nanorods of bismuth sulphide were prepared by thermal decomposition of bismuth N-ethyl cyclohexyl dithiocarbamate at different calcination duration. X-ray diffraction (XRD) analysis shows that at 400 °C, the precursor was fully decomposed to orthorhombic bismuth sulphide after 2 h of calcination. Besides, calcination duration does not affect the existence of Bi_2S_3 phase. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analyses reveal that Bi_2S_3 nanorods with an average width ranging from 29–36 nm were obtained. Energy dispersive X-ray (EDX) analysis confirmed the atomic ratio of Bi and S close to 2:3, giving a possible composition of Bi_2S_3. Direct band gap energy of Bi_2S_3 decreases from 1.83 eV to 1.54 eV as calcination time increases.
11. "Chemical contraction" in rubidium-bismuth melts
Science.gov (United States)
Khairulin, R. A.; Abdullaev, R. N.; Stankus, S. V.
2017-10-01
The density and thermal expansion of liquid rubidium and rubidium-bismuth alloy containing 25.0 at % Bi were measured by the gamma-ray attenuation technique at temperatures from liquidus to 1000 K. The results of this study were compared with the data obtained by other authors. The molar volume of the Rb75Bi25 melt strongly deviates from the additivity rule for ideal solutions.
12. Electrocatalytic activity of bismuth doped silver electrodes
CERN Document Server
2002-01-01
Investigation of redox reactions on silver, and bismuth doped silver electrodes in aqueous KOH solutions, by using potentiostatic steady-state polarization technique, has been carried out. The redox wave potential and current displacements along with multiplicity of the latter have been examined. These electrodes were employed for the oxidation of organic molecules such as ethylamine in alkaline media. Subsequently, these electrodes were ranked with respect to their activity for the redox reactions. (author)
13. Flame spray synthesis under a non-oxidizing atmosphere: Preparation of metallic bismuth nanoparticles and nanocrystalline bulk bismuth metal
Energy Technology Data Exchange (ETDEWEB)
Grass, Robert N.; Stark, Wendelin J. [Institute for Chemical and Bioengineering, ETH Zuerich (Switzerland)], E-mail: [email protected]
2006-10-15
Metallic bismuth nanoparticles of over 98% purity were prepared by a modified flame spray synthesis method in an inert atmosphere by oxygen-deficient combustion of a bismuth-carboxylate based precursor. The samples were characterized by X-ray diffraction, thermal analysis and scanning electron microscopy confirming the formation of pure, crystalline metallic bismuth nanoparticles. Compression of the as-prepared powder resulted in highly dense, nanocrystalline pills with strong electrical conductivity and bright metallic gloss.
14. Doping of germanium telluride with bismuth tellurides
International Nuclear Information System (INIS)
Abrikosov, N.Kh.; Karpinskij, O.G.; Makalatiya, T.Sh.; Shelimova, L.E.
1981-01-01
Effect of germanium telluride doping with bismuth fellurides (Bi 2 Te 3 ; BiTe; Bi 2 Te) on phase transition temperature, lattice parameters and electrophysical properties of alloys is studied. It is shown that in alloys of GeTe-Bi 2 Te 3 (BiTe)(Bi 2 Te) cross sections solid solution of GeTe with Bi 2 Te 3 , characterized by deviation from stoichiometry, and germanium in the second phase the quantity of which increases during the transition from GeTe-Bi 2 Te 3 cross section to GeTe-Bi 2 Te are in equilibrium. Lower values of holes concentration and of electric conductivity and higher values of thermo e.m.f. coefficient in comparison with alloys of GeTe-Bi 2 Te 3 cross section with the same bismuth content are characterized for GeTe-Bi 2 Te cross section alloys. It is shown that in the range of GeTe-base solid solution the α→γ phase transformation which runs trough the two-phase region (α→γ) is observed with tellurium content increase. Extension of α-phase existence region widens with the bismuth content increase. Peculiarities of interatomic interaction in GeTe-base solid solutions with isovalent and heterovalent cation substitution are considered [ru
15. Effect of excess bismuth on the dielectric and piezoelectric properties of strontium bismuth niobate ceramics
International Nuclear Information System (INIS)
Verma, Maya; Tanwar, Amit; Sreenivas, K.
2013-01-01
Excess Bismuth Strontium Bismuth Niobate (Sr 2 Bi 2 Nb 2 O 9 + x wt% Bi 2 O 3 ) ceramics were prepared using conventional solid state reaction method by varying x in the range (x=0%wt - 20%wt). X-ray diffraction studies reveal no significant shift in the peak positions as the Bi content increases from 0.0 to 5%wt. However, at a higher content of Bi beyond x = 5wt% secondary phases relating to Bi 2 O 3 are identified. The c-axis orientation is found to be minimum for SBN ceramic prepared with 5% excess bismuth whereas with further increase in excess Bi 2 O 3 addition during processing, SBN ceramics show a much stronger c-axis orientation. Room temperature dielectric constant measured at 100 KHz is found to increase from 117 to 130 with increase in Bi content from x = 0 to 10wt% suggesting Bi addition has make up for the bismuth losses at higher sintering temperature (1200℃), however with further increase in Bi content (x > 10wt%), the dielectric constant decreases, and could be due to the increased probability of segregation of Bi on the grains of SBN ceramics. The improvement in ferroelectric properties were obtained when the bismuth excess is increased from 0% to 5%. It may be observed that on increasing the excess bismuth to 5%, the transition temperature increases from 424 to 450℃, while further increasing to 10%, transition becomes slightly diffused and phase transition temperature gets decreased to 398℃, which may be due to the formation of secondary phase. 5% excess Bi is found to enhance the dielectric and ferroelectricity properties, and any further increase of Bi in excess (>10%) during processing is found to degrade the electrical and functional properties of SBN. (author)
16. Identification of an eta boride phase as a crystallization product of a NiMoFeB amorphous alloy
International Nuclear Information System (INIS)
Kim, Y.W.; Rabenberg, L.; Bourell, D.L.
1988-01-01
A new, apparently metastable, Mo--Ni boride phase has been observed in transmission electron microscope samples of rapidly consolidated MoNiFeB metallic glass powders. The phase is cubic with lattice parameter 1.083 nm. Its space group as determined by electron diffraction is Fd3-barm and its approximate composition is Mo 3 Ni 3 B. Because its structure, its composition, and its role as a transition phase are analogous to those of eta carbide (M 6 C) in steels and cemented carbides, this phase has tentatively been named ''eta boride.''
17. Successive determinations of metals and boron in metal borides by chelatometric and alkalimetric titrations
International Nuclear Information System (INIS)
Takahashi, Yasuo; Higashi, Iwami; Atoda, Tetzuzo
1976-01-01
Based on the investigation of chemical reactivities of metal borides and of the metal chelate effects on the alkalimetric titration of boron, a method of successive determinations of metals and boron of Mn-, Fe-, Cu- and Al-borides has been developed. The procedure is as follows: (1) Mn-, Fe- and Cu-borides: Dissolve 10 to 30 mg of a sample in a mixture of 3 ml of 3N HNO 3 , 3 ml of 3N H 2 SO 4 and 0.3 ml of 10% H 2 O 2 by heating in a quartz flask equipped with a reflux condenser. Cool the solution obtained, add 0.02M CyDTA solution in excess and neutralize to pH 3 with 2N NaOH solution. Boil the solution for several minutes to ensure the formation of the metal chelate. After cooling, adjust the pH exactly to 6.7 with 0.5 M NaHCO 3 solution, and then determine the metal concentration by back-titrating the excess CyDTA with 0.01M ZnSO 4 solution using MTB as an indicator. After the titration is over, make the solution to pH 3 with 2N H 2 SO 4 and boil for several minutes to expel CO 2 . Cool the solution, adjust the pH exactly to 7.0 with 0.1N CO 2 -free NaOH solution and add 5 g of mannite and ten drops of 0.1% phenolphthalein solution. Finally, titrate the mannite-boric acid complex with 0.05N NaOH solution until the pink tinge is observed (pH 8.2). (2) Al-boride: Fuse 10 to 30 mg of a sample with a mixture of 1.5 g of Na 2 CO 3 and 0.3 g of KNO 3 in a nickel crucible. Digest the melt with water and filter off the residue (nickel oxide). Add 0.01 M EDTA solution in excess to the filterate and make it to pH 3 with 2N H 2 SO 4 . Analytical Results obtained by the present method agree well with those by other methods. The present method takes only 40 minutes, whereas several hours are required to determine metal and boron by other methods. (auth.)
18. Effectiveness of ranitidine bismuth citrate and proton pump inhibitor ...
African Journals Online (AJOL)
Effectiveness of ranitidine bismuth citrate and proton pump inhibitor based triple therapies of Helicobacter pylori in Turkey. ... Results: When we look at the eradication rates of the treatment groups, only two groups (ranitidine bismuth citrate and rabeprazole groups) had eradication rates greater than 80%, both at intention to ...
19. Bismuth-silver mineralization in the Sergozerskoe gold occurrence
Directory of Open Access Journals (Sweden)
Kalinin A. A.
2017-03-01
Full Text Available Bismuth-silver mineralization attendant to gold mineralization in the Sergozerskoe gold occurrence has been studied in detail. Bi-Ag mineralization is connected with diorite porphyry dykes, which cut volcanic-sedimentary Lopian complexes of the Strel'ninsky greenstone belt – hornblendite and actinolite-chlorite amphibolites, biotite and bi-micaceous gneisses. Distribution of Bi-Ag mineralization similar to gold mineralization is controlled by 80 m thick zone of silicification. Bi minerals are found in brecciated diorite porphyry. Bismuth-silver mineralization includes native metals (bismuth, electrum, silver, tellurides (hedleyite, hessite, selenides (ikunolite, sulfides and sulfosalts of Bi and Ag (matildite, lillianite, eckerite, jalpaite, prustite, acanthite, a few undiagnosed minerals. All Bi and Ag minerals associate with galena. Composition of mineralization evolved from early to late stages of development, depending on intensity of rock alteration. The earliest Bi-Ag minerals were native bismuth and hedleyite formed dissemination in galena, and electrum with 30-45 mass.% Au. Later native bismuth was partly substituted by silver and bismuth sulfosalts and bismuth sulfides. The latest minerals were low-temperature silver sulfides eckerite, jalpaite, and acanthite, which were noted only in the most intensively altered rocks. As soon as the process of formation of Bi-Ag mineralization is the same as formation of gold, findings of bismuth-silver mineralization can serve as a positive exploration sign for gold in the region.
20. Heat capacity, enthalpy and entropy of bismuth niobate and bismuth tantalate
Czech Academy of Sciences Publication Activity Database
Hampl, M.; Strejc, A.; Sedmidubský, D.; Růžička, K.; Hejtmánek, Jiří; Leitner, J.
2006-01-01
Roč. 179, - (2006), s. 77-80 ISSN 0022-4596 Institutional research plan: CEZ:AV0Z10100521 Keywords : heat capacity * heat of formation * heat content * bismuth perovskite Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.107, year: 2006
1. Heat-Pipe Bismuth Laser; Examination of Laser Action at 4722A in Bismuth Vapor
Science.gov (United States)
1976-11-01
11, 15(1975). of Type 6p 3 -6p 2 7s in the Bismuth Atomic Spectrum in Intermediate Coupling," Acta Physica Polonica A47, 231(1975). 19. A.N. Nesmeyanov...Calculated Transit n Probabilities and Lifetimes for the First Excited Configuration np (n+l)s in the Neutral As, Sb and Bi Atoms, " Physica Scripta
2. Bismuth X-ray absorber studies for TES microcalorimeters
International Nuclear Information System (INIS)
Sadleir, J.E.; Bandler, S.R.; Brekosky, R.P.; Chervenak, J.; Figueroa-Feliciano, E.; Finkbeiner, F.; Iyomoto, N.; Kelley, R.L.; Kilbourne, C.A.; King, J.M.; Porter, F.S.; Robinson, I.K.; Saab, T.; Talley, D.J.
2006-01-01
Bismuth's large atomic number and low carrier density makes it an attractive X-ray absorber material for microcalorimeters. Bismuth's long Fermi wavelength and long mean free paths have motivated much interest in the fabrication of high quality bismuth films to study quantum size effects. Despite such incentives, fabrication of high quality bismuth films has proven difficult, and measured properties of such films are highly variable in the literature. Implementing a bismuth deposition process for TES (superconducting Transition Edge Sensor) device fabrication presents additional challenges particularly at interfaces due to the inherent granularity and surface roughness of its films, its low melting point, and its tendency to diffuse and form undesired intermetallic phases. We report observations of Bi-Cu and Bi-Au diffusion in our devices correlating with large shifts in T c (superconducting transition temperature). Using SEM and in situ R vs T annealing experiments we have been able to study these diffusion processes and identify their activation temperatures
3. Boron-dependency of molybdenum boride electrocatalysts for the hydrogen evolution reaction
Energy Technology Data Exchange (ETDEWEB)
Park, Hyounmyung; Encinas, Andrew; Fokwa, Boniface P.T. [Department of Chemistry, University of California, Riverside, CA (United States); Department of Chemical and Environmental Engineering, University of California, Riverside, CA (United States); Scheifers, Jan P.; Zhang, Yuemei [Department of Chemistry, University of California, Riverside, CA (United States)
2017-05-08
Molybdenum-based materials have been considered as alternative catalysts to noble metals, such as platinum, for the hydrogen evolution reaction (HER). We have synthesized four binary bulk molybdenum borides Mo{sub 2}B, α-MoB, β-MoB, and MoB{sub 2} by arc-melting. All four phases were tested for their electrocatalytic activity (linear sweep voltammetry) and stability (cyclic voltammetry) with respect to the HER in acidic conditions. Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy (XPS) for the first time; MoB{sub 2} and β-MoB show excellent activity in the same range as the recently reported α-MoB and β-Mo{sub 2}C phases, while the molybdenum richest phase Mo{sub 2}B show significantly lower HER activity, indicating a strong boron-dependency of these borides for the HER. In addition, MoB{sub 2} and β-MoB show long-term cycle stability in acidic solution. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
4. Characterization of boride-based powders and detonation gun sprayed cermet coatings
International Nuclear Information System (INIS)
Keraenen, J.; Stenberg, T.; Maentylae, T.
1995-01-01
Detonation gun sprayed (DGS) cermet coatings containing complex ternary transition metal boride as hard particles dispersed in a stainless steel or nickel based superalloy matrix have been characterized. Microstructure of the coatings, as well as powders, were studied with optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and analytical transmission electron microscopy (AEM). X-ray microanalysis of the coatings were carried out using energy dispersive X-ray spectrometer (EDS) attached to the SEM and AEM. Moreover, abrasion wear resistance of the coatings was evaluated with a rubber wheel abrasion test equipment. The general microstructure of studied coatings appeared to be heterogeneous in the terms of the distribution, size and crystallographic nature of the phases. Nonetheless, very low porosities were obtained and in the coatings the oxide phase as well as the unmelted particles and the formation of oxide phase were avoided by optimization of DGS parameters. So far the abrasive wear resistance of boride-based cermet coatings is not so good as that of the WC-12Co coatings
5. Boron-dependency of molybdenum boride electrocatalysts for the hydrogen evolution reaction
International Nuclear Information System (INIS)
Park, Hyounmyung; Encinas, Andrew; Fokwa, Boniface P.T.; Scheifers, Jan P.; Zhang, Yuemei
2017-01-01
Molybdenum-based materials have been considered as alternative catalysts to noble metals, such as platinum, for the hydrogen evolution reaction (HER). We have synthesized four binary bulk molybdenum borides Mo_2B, α-MoB, β-MoB, and MoB_2 by arc-melting. All four phases were tested for their electrocatalytic activity (linear sweep voltammetry) and stability (cyclic voltammetry) with respect to the HER in acidic conditions. Three of these phases were studied for their HER activity and by X-ray photoelectron spectroscopy (XPS) for the first time; MoB_2 and β-MoB show excellent activity in the same range as the recently reported α-MoB and β-Mo_2C phases, while the molybdenum richest phase Mo_2B show significantly lower HER activity, indicating a strong boron-dependency of these borides for the HER. In addition, MoB_2 and β-MoB show long-term cycle stability in acidic solution. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
6. Bismuth-Based Quadruple Therapy with Bismuth Subcitrate, Metronidazole, Tetracycline and Omeprazole in the Eradication of Helicobacter pylori
Directory of Open Access Journals (Sweden)
Raymond Lahaie
2001-01-01
Full Text Available BACKGROUND: A previous study showed that 14 days of qid bismuth-based triple therapy with tetracycline 500 mg, metronidazole 250 mg and colloidal bismuth subcitrate 120 mg resulted in excellent Helicobacter pylori eradication rates (89.5%. The present study looked at a shorter treatment period by adding omeprazole and by reducing the dose of tetracycline.
7. Synthesis of molybdenum borides and molybdenum silicides in molten salts and their oxidation behavior in an air-water mixture
NARCIS (Netherlands)
Kuznetsov, S.A.; Kuznetsova, S.V.; Rebrov, E.V.; Mies, M.J.M.; Croon, de M.H.J.M.; Schouten, J.C.
2005-01-01
The formation of various coatings in molybdenum-boron and molybdenum-silicon systems was investigated. Boronizing and siliciding treatments were conducted in molten salts under inert gas atm. in the 850-1050 DegC temp. range for 7 h. The presence of boride (e.g. Mo2B, MoB, Mo2B5) and silicide
8. Elevated temperature tensile properties of borated 304 stainless steel: Effect of boride dispersion on strength and ductility
International Nuclear Information System (INIS)
Stephens, J.J.; Sorenson, K.B.; McConnell, P.
1991-01-01
This paper has documented the increase in strain to fracture and yield strength obtained with Grade A versions of types 304B5 and 304B7 relative to their respective Grade B, counterparts. The apparent microstructural reason for these property increases is the finer dispersion of boride in the Grade A material, obtained by means of a Powder Metallurgy process, relative to the conventional Grade B material which is produced using an Ingot Metallurgy process. The area size distribution of borides can be well approximated using a log-normal distribution, with the largest boride particles in the Grade B material having areas in the range of 450--600 μm 2 . By comparison, the largest boride particles in the Grade A material have areas nearly an order of magnitude smaller than the largest particles in their Grade B counterparts. A Section III ASME B ampersand PV code case inquiry has been initiated for non-welded versions of 304B4A, 3045A and 3046A ,material
9. Wear resistance of laser-deposited boride reinforced Ti-Nb-Zr-Ta alloy composites for orthopedic implants
International Nuclear Information System (INIS)
Samuel, Sonia; Nag, Soumya; Scharf, Thomas W.; Banerjee, Rajarshi
2008-01-01
The inherently poor wear resistance of titanium alloys limits their application as femoral heads in femoral (hip) implants. Reinforcing the soft matrix of titanium alloys (including new generation β-Ti alloys) with hard ceramic precipitates such as borides offers the possibility of substantially enhancing the wear resistance of these composites. The present study discusses the microstructure and wear resistance of laser-deposited boride reinforced composites based on Ti-Nb-Zr-Ta alloys. These composites have been deposited using the LENS TM process from a blend of elemental Ti, Nb, Zr, Ta, and boron powders and consist of complex borides dispersed in a matrix of β-Ti. The wear resistance of these composites has been compared with that of Ti-6Al-4V ELI, the current material of choice for orthopedic femoral implants, against two types of counterfaces, hard Si 3 N 4 and softer SS440C stainless steel. Results suggest a substantial improvement in the wear resistance of the boride reinforced Ti-Nb-Zr-Ta alloys as compared with Ti-6Al-4V ELI against the softer counterface of SS440. The presence of an oxide layer on the surface of these alloys and composites also appears to have a substantial effect in terms of enhanced wear resistance
10. Quantum oscillations of conductivity in bismuth wires
International Nuclear Information System (INIS)
Condrea, Elena
2011-01-01
Measurements of the resistance of bismuth nanowires with several diameters and different quality reveal oscillations on the dependence of resistance under uniaxial strain at T = 4.2 K. Amplitude of oscillations is significant (38 %) at helium temperature and becomes smearing at T = 77 K. Observed oscillations originate from quantum size effect. A simple evaluation of period of oscillations allows us to identify the groups of carriers involved in transport. Calculated periods of 42.2 and 25.9 nm satisfy approximately the ratio 2:1 for two experimentally observed sets of oscillations from light and heavy electrons.
11. An evaluated neutronic data file for bismuth
International Nuclear Information System (INIS)
Guenther, P.T.; Lawson, R.D.; Meadows, J.W.; Smith, A.B.; Smith, D.L.; Sugimoto, M.; Howerton, R.J.
1989-11-01
A comprehensive evaluated neutronic data file for bismuth, extending from 10 -5 eV to 20.0 MeV, is described. The experimental database, the application of the theoretical models, and the evaluation rationale are outlined. Attention is given to uncertainty specification, and comparisons are made with the prior ENDF/B-V evaluation. The corresponding numerical file, in ENDF/B-VI format, has been transmitted to the National Nuclear Data Center, Brookhaven National Laboratory. 106 refs., 10 figs., 6 tabs
12. Optical Properties of Bismuth Tellurite Based Glass
Directory of Open Access Journals (Sweden)
Hooi Ming Oo
2012-04-01
Full Text Available A series of binary tellurite based glasses (Bi2O3x (TeO2100−x was prepared by melt quenching method. The density, molar volume and refractive index increase when bismuth ions Bi3+ increase, this is due to the increased polarization of the ions Bi3+ and the enhanced formation of non-bridging oxygen (NBO. The Fourier transform infrared spectroscopy (FTIR results show the bonding of the glass sample and the optical band gap, Eopt decreases while the refractive index increases when the ion Bi3+ content increases.
13. Optical Properties of Bismuth Tellurite Based Glass
Science.gov (United States)
Oo, Hooi Ming; Mohamed-Kamari, Halimah; Wan-Yusoff, Wan Mohd Daud
2012-01-01
A series of binary tellurite based glasses (Bi2O3)x (TeO2)100−x was prepared by melt quenching method. The density, molar volume and refractive index increase when bismuth ions Bi3+ increase, this is due to the increased polarization of the ions Bi3+ and the enhanced formation of non-bridging oxygen (NBO). The Fourier transform infrared spectroscopy (FTIR) results show the bonding of the glass sample and the optical band gap, Eopt decreases while the refractive index increases when the ion Bi3+ content increases. PMID:22605999
14. Effect of borides on hot deformation behavior and microstructure evolution of powder metallurgy high borated stainless steel
Energy Technology Data Exchange (ETDEWEB)
Zhou, Xuan [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Wang, Mingjia, E-mail: [email protected] [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Fu, Yifeng [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China); Wang, Zixi; Li, Yanmei [Yanming Alloy Roll Co. Ltd, Qinhuangdao 066004 (China); Yang, Shunkai; Zhao, Hongchang; Li, Hangbo [State Key Laboratory of Metastable Materials Science and Technology, College of Materials Science and Engineering, Yanshan University, Qinhuangdao 066004 (China)
2017-02-15
To investigate borides effect on the hot deformation behavior and microstructure evolution of powder metallurgy high borated stainless steel, hot compression tests at the temperatures of 950– 1150 °C and the strain rates of 0.01– 10 s{sup −1} were performed. Flow stress curves indicated that borides increased the material's stress level at low temperature but the strength was sacrificed at temperatures above 1100 °C. A hyperbolic-sine equation was used to characterize the dependence of the flow stress on the deformation temperature and strain rate. The hot deformation activation energy and stress exponent were determined to be 355 kJ/mol and 3.2, respectively. The main factors leading to activation energy and stress exponent of studied steel lower than those of commercial 304 stainless steel were discussed. Processing maps at the strains of 0.1, 0.3, 0.5, and 0.7 showed that flow instability mainly concentrated at 950– 1150 °C and strain rate higher than 0.6 s{sup −1}. Results of microstructure illustrated that dynamic recrystallization was fully completed at both high temperature-low strain rate and low temperature-high strain rate. In the instability region cracks were generated in addition to cavities. Interestingly, borides maintained a preferential orientation resulting from particle rotation during compression. - Highlights: •The decrement of activation energy was affected by boride and boron solution. •The decrease of stress exponent was influenced by composition and Cottrell atmosphere. •Boride represented a preferential orientation caused by particle rotation.
15. Coating compositions comprising bismuth-alloyed zinc
DEFF Research Database (Denmark)
2008-01-01
The present application discloses (i) a coating composition comprising a particulate zinc-based alloyed material, said material comprising 0.05-0.7% by weight of bismuth (Bi), the D50 of the particulate material being in the range of 2.5-30 µm; (ii) a coated structure comprising a metal structure...... having a first coating of the zinc-containing coating composition applied onto at least a part of the metal structure in a dry film thickness of 5-100 µm; and an outer coating applied onto said zinc-containing coating in a dry film thickness of 30-200 µm; (iii) a particulate zinc-based alloyed material......, wherein the material comprises 0.05-0.7%(w/w) of bismuth (Bi), and wherein the D50 of the particulate material is in the range of 2.5-30 µm; (iv) a composite powder consisting of at least 25%(w/w) of the particulate zinc-based alloyed material, the rest being a particulate material consisting of zinc...
16. Liquid Lead-Bismuth Materials Test Loop
International Nuclear Information System (INIS)
Tcharnotskaia, Valentina; Ammerman, Curtt; Darling, Timothy; King, Joe; Li, Ning; Shaw, Don; Snodgrass, Leon; Woloshun, Keith
2002-01-01
We designed and built the Liquid Lead-Bismuth Materials Test Loop (MTL) to study the materials behavior in a flow of molten lead-bismuth eutectic (LBE). In this paper we present a description of the loop with main components and their functions. Stress distribution in the piping due to sustained, occasional and expansion loads is shown. The loop is designed so that a difference of 100 deg. C can be attained between the coldest and the hottest parts at a nominal flow rate of 8.84 GPM. Liquid LBE flow can be activated by a mechanical sump pump or by natural convection. In order to maintain a self-healing protective film on the surface of the stainless steel pipe, a certain concentration of oxygen has to be maintained in the liquid metal. We developed oxygen sensors and an oxygen control system to be implemented in the loop. The loop is outfitted with a variety of instruments that are controlled from a computer based data acquisition system. Initial experiments include preconditioning the loop, filling it up with LBE, running at uniform temperature and tuning the oxygen control system. We will present some preliminary results and discuss plans for the future tests. (authors)
17. What is the structure of liquid Bismuth?
International Nuclear Information System (INIS)
Caspi, El'ad N; Greenberg, Yaron; Yahel, Eyal; Beuneu, Brigitte; Makov, Guy
2012-01-01
The structure of liquid Bismuth is probably the best-studied among elemental liquid metals because of a combination of the interesting physical properties of Bismuth and its excellent neutron scattering properties. Over the last six decades there have been more than 10 independent studies of the structure of liquid Bi, near the melting temperature. This remarkable number of measurements provides an opportunity to compare these results and to analyze the different sources of error contributing to the calculated pair distribution function. In the present contribution we analyze possible sources of error by varying the analysis procedure for a given measurement. By repeating a previous measurement in a new experimental configuration we demonstrate that an invariant (i.e. up to an absolute error) structure factor can be obtained. Transforming the structure factor into the radial distribution introduces new sources of error which causes the scatter to be greater than that required to resolve issues such as the existence of liquid-liquid phase transitions in Bi and to obtain correlation between thermo-physical properties and structure. We consider the contribution of different parameters when transforming the structure factor to the radial distribution function.
18. Study of point defects in bismuth
International Nuclear Information System (INIS)
Bois, P.
1987-03-01
Single crystalline samples of bismuth, pure and n or p - doped by adding tellurium or tin, were electron irradiated at low temperature (4.2 K and 20 K). In the energy range 0.7 - 2.5 MeV, a displacement threshold energy of 13 eV and an athermal recombination volume of 150 atomic volumes were determined. Joint measurements of resistivity, magnetotransport and positron annihilation enabled to precised the nature of the annealing stages: 40-50 K, free migration of interstitials; 90-120 K long range migration of vacancy. Point defects have according to their nature a different effect on the electronic properties of bismuth: isolated Frenkel pairs are globally donnors with a charge of + 0.16 e- and the vacancy is donnor, which seems to attribute to it a negative formation volume. A simple model with non-deformating bands is no longer sufficient to explain the behaviour under irradiation: one has to take into account an acceptor level with a charge of - 0,27 e-, linked to the cascade-type defects and resonating with the valence band. It's position in the band overlap and it's width (8 meV) could be precised. In first approximation this coupling with less mobile carriers does not affect the simple additive rule which exists for relaxation times. Some yet obscure magnetic properties seem to be linked to this defect level [fr
19. Development of lead-bismuth coolant technology for nuclear device
International Nuclear Information System (INIS)
Kamata, Kin-ya; Kitano, Teruaki; Ono, Mikinori
2004-01-01
Liquid lead-bismuth is a promising material as a future fast reactor coolant or an intensive neutron source material for accelerator driven transmutation system (ADS). To develop nuclear plants and their installations using lead-bismuth coolant for practical use, both coolant technologies, inhabitation process of steels and quality control of coolant, and total operation system for liquid lead-bismuth plants are required. Based on the experience of liquid metal coolant, Mitsui Engineering and Shipbuilding Co., Ltd. (MES) has completed the liquid lead-bismuth forced circulation loop and has acquired various engineering data on main components including economizer. As a result of tis operation, MES has developed key technologies of lead-bismuth coolant such as controlling of oxygen content in lead-bismuth and a purification of lead-bismuth coolant. MES participated in the national project, ''The Development of Accelerator Driven Transmutation System'', together with JAERI (Japan Atomic Energy Research Institute) and started corrosion test for beam window of ADS. (author)
20. High Temperature Sliding Wear of NiAl-based Coatings Reinforced by Borides
Directory of Open Access Journals (Sweden)
Oleksandr UMANSKYI
2016-05-01
Full Text Available The development of composite materials (CM in the systems “metal-refractory compound” is one of the up-to-date trends in design of novel materials aimed at operating under the conditions of significant loads at high temperature. To design such material, NiAl, which is widely used for deposition of protective coatings on parts of gas-turbine engines, was selected for a matrix. To strengthen a NiAl under the conditions of intense wear and a broad temperature range (up to 1000 °C, it is reasonable to add refractory inclusions. Introduction of refractory borides into matrix leads to a marked increase in metal wear resistance. In order to research the behavior of the designed composites at high temperatures and to study the influence of oxides on the friction processes, the authors carried out high temperature oxidation of CM of the above systems at 1000 °С for 90 min. It was determined that all of the composites were oxidized selectively and that the thickness of oxide layers formed on the boride inclusions is 3 – 7 times that on the oxides formed on the NiAl matrix. The mechanism of wear of gas-thermal coatings of the NiAl – МеB2 systems was studied for conditions of high temperature tribotests using the «pin-on-disc» technique. The obtained results indicate that introduction of TiB2, CrB2 and ZrB2 leads to their more intense oxidation during high temperature tribotests as compared to the matrix. The oxides formed on refractory borides act as solid lubricants, which promote a decrease in wear of the contact friction pairs. For more detailed investigation of the effect of tribo-oxidation products on the friction processes, tribotests were conducted for prior oxidized (at 900 °С coatings NiAl – 15 wt.% CrB2 (TiB2, ZrB2.DOI: http://dx.doi.org/10.5755/j01.ms.22.1.8093
1. Properties of Nanostructure Bismuth Telluride Thin Films Using Thermal Evaporation
Directory of Open Access Journals (Sweden)
Swati Arora
2017-01-01
Full Text Available Bismuth telluride has high thermoelectric performance at room temperature; in present work, various nanostructure thin films of bismuth telluride were fabricated on silicon substrates at room temperature using thermal evaporation method. Tellurium (Te and bismuth (Bi were deposited on silicon substrate in different ratio of thickness. These films were annealed at 50°C and 100°C. After heat treatment, the thin films attained the semiconductor nature. Samples were studied by X-ray diffraction (XRD and scanning electron microscopy (SEM to show granular growth.
2. Electronic Structure Properties and a Bonding Model of Thermoelectric Half-Heusler and Boride Phases
Science.gov (United States)
Simonson, Jack William
Half-Heusler alloys MNiSn and MCoSb (M = Ti, Zr, Hf) and layered boride intermetallics with structure types YCrB4 and Er 3CrB7 were designed, synthesized, and characterized. The thermoelectric properties of these two classes of alloys were measured from room temperature to 1100 K with the intent of indirectly studying their electronic structure properties and gauging not only their suitability but that of related alloys for high temperature thermoelectric power generation. In the case of the half-Heusler alloys, transition metals were substituted to both the M and Ni/Co sites to study the resultant modifications of the d-orbital-rich portion of the electronic structure near the Fermi energy. This modification and subsequent pinning of the Fermi energy within the gap is discussed herein in terms of first principles electronic structure calculations from the literature. In the half-Heusler alloys, it was found that substitution of transition metals invariably led to a decrease in the thermopower, while the resistivity typically maintained its semiconducting trend. On the other hand, Sn doping in MCoSb type alloys -- a dopant that has been known for some time to be efficient -- was shown to result in high ZT at temperatures in excess of 1000 K. Moreover, the band gaps of the transition metal-doped alloys measured in this work offer insight into the discrepancy between the predicted and measured band gaps in the undoped parent compositions. In the case of the layered boride alloys, on the other hand, few electronic calculations have been published, thus prompting the generalization of a well-known electron counting rule -- which is typically used to study molecular organometallics, boranes, and metallocenes -- to predict the trends in the densities of states of crystalline solids that possess the requisite deltahedral bonding geometry. In accordance with these generalized electronic counting rules, alloys of the form RMB4 (R = Y, Gd, Ho; M = Cr, Mo, W) were measured to
3. Thermo-emf of cermet films based on rare earth borides
International Nuclear Information System (INIS)
Islamgaliev, R.K.; Zyrin, A.V.; Shulishova, O.I.; Shcherbak, I.A
1987-01-01
Thermo-emf and electric conductivity of granulated films which contain a solid solution of europium and praseodymium borides Eu 0.5 Pr 0.5 B 6 as a conducting phase, and glass-crystal binder on the base of alummomagnesial fluosilicates as a dielectric phase are studied within the temperature range of 100-1100 K. Thermo-emf of films has a negative sign within the temperature range of 100-500 K and does not exceed 5 μkV/K according to the absolute value which is close to the value of the conducting phase thermo-emf. A negative sign and a small value of thermo-emf are indicative of the charge transfer in granulated films by electrons. Contribution of each of the components into the general thermo-emf is different at high temperatures in different temperature ranges and depends on the individual physico-chemical properties of the used materials
4. New ternary transition metal borides containing uranium and rare earth elements
International Nuclear Information System (INIS)
Rogl, P.; Delong, L.
1983-01-01
The new ternary actinide metal diborides U 2 MoB 6 , U 2 ReB 6 , U 2 OsB 6 , URuB 4 and UOsB 4 were prepared and found to crystallize with either the Y 2 ReB 6 or the ThMoB 4 type of structure. LuRuB 4 and LuOsB 4 crystallize with the YCrB 4 type of structure. In a ternary series of solid solutions YRh 3 Bsub(1-x) (0 0 C), boron was found to stabilize a Cu 3 Au type of structure. The superconductivity of the new uranium compounds and of a series of ternary transition metal borides was investigated; no superconductivity was observed for temperatures as low at 1.3-1.5 K. The cubic perovskite or filled Cu 3 Au structure is discussed as a type which is very unfavorable for the occurrence of superconductivity. (Auth.)
5. Structure-chemical and metallurgical investigations in boride- and boron nitride systems
International Nuclear Information System (INIS)
Smid, I.
1987-01-01
Thermodynamic phase equilibria in the systems (Ti, Zv, Hf)-B-N were determined in an isothermal cut at 1500 O C and 1 atm. The phase field separation is dominated by the high stability of the metal mononitrides and metal diborides. No ternery compounds were found. There are varying solubilities of B and N in the nitrides and borides. The system Cr-B-N was investigated at 1000 O C under 1 atm argon and vacuum, and at 1400 O C at 1 atm argon and 1 atm nitrogen. For the system Mn-B-N the phase field separation was determined at 900 O C under 1 atm Ar and under vacuum. The properties of hard metals with various binding phases and TiBr as hard constituents were investigated. 6 refs., 6 figs., 6 tabs. (qui)
6. Structural, electronic and thermal properties of super hard ternary boride, WAlB
Science.gov (United States)
Rajpoot, Priyanka; Rastogi, Anugya; Verma, U. P.
2018-04-01
A first principle study of the structural, electronic and thermal properties of Tungsten Aluminum Boride (WAlB) using full-potential linearized augmented plane wave (FP-LAPW) in the frame work of density function theory (DFT) have been calculated. The calculated equilibrium structural parameters are in excellent agreement with available experimental results. The calculated electronic band structure reveals that WAlB is metallic in nature. The quasi-harmonic Debye model is applied to study of the temperature and pressure effect on volume, Debye temperature, thermal expansion coefficient and specific heat at constant volume and constant pressure. To the best of our knowledge theoretical investigation of these properties of WAlB is reported for the first time.
7. Ultrasonic investigations of some bismuth borate glasses doped with ...
Keywords. Bismuth borate glasses; elastic moduli; Makishima–Mackenzie model. 1. Introduction ... former because of the small field strength of Bi3+ ion. Bi2O3 ..... Typically, when the material undergoes a phase change, the value of the.
8. Studies on bismuth carboxylates—synthesis and characterization of ...
crystalline modification (4 ) of the previously reported coordination polymer, bismuth tris(picolinate), [Bi(2– .... no significant change in the IR spectrum or the melting behaviour between 4 .... lens et al.7 There are moderate differences in the.
9. PREFACE: The 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008)
Science.gov (United States)
Tanaka, Takaho
2009-07-01
This volume of Journal of Physics: Conference Series contains invited and contributed peer-reviewed papers that were presented at the 16th International Symposium on Boron, Borides and Related Materials (ISBB 2008), which was held on 7-12 September 2008, at Kunibiki Messe, Matsue, Japan. This triennial symposium has a half-century long history starting from the 1st meeting in 1959 at Asbury Park, New Jersey. We were very pleased to organize ISBB 2008, which gathered chemists, physicists, materials scientists as well as diamond and high-pressure researchers. This meeting had a strong background in the boron-related Japanese research history, which includes the discovery of superconductivity in MgB2 and development of Nd-Fe-B hard magnets and of YB66 soft X-ray monochromator. The scope of ISBB 2008 spans both basic and applied interdisciplinary research that is centered on boron, borides and related materials, and the collection of articles defines the state of the art in research on these materials. The topics are centered on: 1. Preparation of new materials (single crystals, thin films, nanostructures, ceramics, etc) under normal or extreme conditions. 2. Crystal structure and chemical bonding (new crystal structures, nonstoichiometry, defects, clusters, quantum-chemical calculations). 3. Physical and chemical properties (band structure, phonon spectra, superconductivity; optical, electrical, magnetic, emissive, mechanical properties; phase diagrams, thermodynamics, catalytic activity, etc) in a wide range of temperatures and pressures. 4. Applications and prospects (thermoelectric converters, composites, ceramics, coatings, etc) There were a few discoveries of new materials, such as nanomaterials, and developments in applications. Many contributions were related to 4f heavy Fermion systems of rare-earth borides. Exotic mechanisms of magnetism and Kondo effects have been discussed, which may indicate another direction of development of boride. Two special sessions
10. Synthesis and characterization of superconducting bismuthates
International Nuclear Information System (INIS)
Tang, Horngyi.
1991-01-01
A new electrosynthetic technique for low-temperature crystal growth of superconducting bismuthates was developed, and its utility demonstrated by growing various high-quality BiO 3 crystals. The crystals of Ba 1-x K x BiO 3 and Ba 1-x Rb x BiO 3 display their T c onset at 31.8k and 28k, respectively, using SQUID magnetometry. The structure of a KBiO 3 x H 2 O single crystal determined by single crystal x-ray diffraction confirms previous results from powder samples that it is isostructural with KSbO 3 . The crystals of Ba 1-x Cs x BiO 3 do not show superconductivity to 4k. Chemical vapor-transport experiments leading to the fabrication of MoS 2 /WSe 2 junctions were also performed and are described in detail
11. Flotation atomic absorption determination of bismuth in nonferrous metal alloys
International Nuclear Information System (INIS)
Ososkov, V.K.; Plintus, A.M.; Kornelli, M.Eh.; Zakhariya, A.N.; Lozanova, E.V.
1986-01-01
Technique of flotation concentration and atomic absorption determination of bismuth microquantities in alloys on the basis of copper and zinc has been developed. Fine-dispersed EhDEh-10P anionite was used as a carrier in flotation concentration. State standard samples (SSS) of brasses and German silver were used as analysed objects. Effect of macrocomponents on the results of bismuth content determination has been studied. Satisfactory coincidence of the results obtained and SSS certificates is shown
12. Platinum-Bismuth Bimetallic Catalysts: Synthesis, Characterization and Applications
OpenAIRE
Saucedo, Jose A, Jr; Xiao, Yang; Varma, Arvind
2015-01-01
Bimetallic catalysts have been explored and shown to exhibit unique characteristics which are not present in monometallic catalysts. Platinum is well known as an effective catalyst for oxidation and reduction reactions, and it can be made more effective when bismuth is introduced as a promotor. Thus, the effectiveness of the Pt-Bi catalyst was demonstrated in prior work. What is not clear, however, is the mechanism behind the catalyst function; why addition of bismuth to platinum decreases de...
13. Interlayer utilization (including metal borides) for subsequent deposition of NSD films via microwave plasma CVD on 316 and 440C stainless steels
Science.gov (United States)
Ballinger, Jared
Diamond thin films have promising applications in numerous fields due to the extreme properties of diamonds in conjunction with the surface enhancement of thin films. Biomedical applications are numerous including temporary implants and various dental and surgical instruments. The unique combination of properties offered by nanostructured diamond films that make it such an attractive surface coating include extreme hardness, low obtainable surface roughness, excellent thermal conductivity, and chemical inertness. Regrettably, numerous problems exist when attempting to coat stainless steel with diamond generating a readily delaminated film: outward diffusion of iron to the surface, inward diffusion of carbon limiting necessary surface carbon precursor, and the mismatch between the coefficients of thermal expansion yielding substantial residual stress. While some exotic methods have been attempted to overcome these hindrances, the most common approach is the use of an intermediate layer between the stainless steel substrate and the diamond thin film. In this research, both 316 stainless steel disks and 440C stainless steel ball bearings were tested with interlayers including discrete coatings and graded, diffusion-based surface enhancements. Titanium nitride and thermochemical diffusion boride interlayers were both examined for their effectiveness at allowing for the growth of continuous and adherent diamond films. Titanium nitride interlayers were deposited by cathodic arc vacuum deposition on 440C bearings. Lower temperature diamond processing resulted in improved surface coverage after cooling, but ultimately, both continuity and adhesion of the nanostructured diamond films were unacceptable. The ability to grow quality diamond films on TiN interlayers is in agreement with previous work on iron and low alloy steel substrates, and the similarly seen inadequate adhesion strength is partially a consequence of the lacking establishment of an interfacial carbide phase
14. In situ electron beam irradiated rapid growth of bismuth nanoparticles in bismuth-based glass dielectrics at room temperature
International Nuclear Information System (INIS)
Singh, Shiv Prakash; Karmakar, Basudeb
2011-01-01
In this study, in situ control growth of bismuth nanoparticles (Bi 0 NPs) was demonstrated in bismuth-based glass dielectrics under an electron beam (EB) irradiation at room temperature. The effects of EB irradiation were investigated in situ using transmission electron microscopy (TEM), selected-area electron diffraction and high-resolution transmission electron microscopy. The EB irradiation for 2–8 min enhanced the construction of bismuth nanoparticles with a rhombohedral structure and diameter of 4–9 nm. The average particle size was found to increase with the irradiation time. Bismuth metal has a melting point of 271 °C and this low melting temperature makes easy the progress of energy induced structural changes during in situ TEM observations. This is a very useful technique in nano-patterning for integrated optics and other applications.
15. Quantity, size and distribution of borides for aluminium grain refinement by neutron-induced autoradiography (NIAR). Pt. 2
International Nuclear Information System (INIS)
Rachlitz, R.; Gaertner, S.; Holze, J.; Krumnacker, M.
1990-01-01
Al-Ti-B grain refiners improve the cast structure of aluminium and its alloys, but also cause problems related to the great hardness of the borides and their tendency to agglomerate and settle. Accurate information about the distribution, quantity and size of the TiB 2 particles is needed if material properties are to be improved and the quantity of additives minimized. This information is obtained mostly by NIAR. In laboratory-scale tests Al 99.8 and Al 99.5 were refined using different master alloys added in various quantities. In all cases the commercial master alloy gave the best refining effect. Besides boride particle size distribution and the presence of nuclei and nucleus stabilizers, morphological properties (duplex particles) are obviously of essential importance. It has been demonstrated that the TiB 2 size distribution values determined by NIAR are comparable with those established by optical microscopy measurements. (orig.) [de
16. Effects of process parameters on tungsten boride production from WO{sub 3} by self propagating high temperature synthesis
Energy Technology Data Exchange (ETDEWEB)
Yazici, Sertac [Metallurgical and Materials Engineering Department, Istanbul Technical University, Maslak, Istanbul 34469 (Turkey); Derin, Bora, E-mail: [email protected] [Metallurgical and Materials Engineering Department, Istanbul Technical University, Maslak, Istanbul 34469 (Turkey)
2013-01-01
Highlights: Black-Right-Pointing-Pointer We produced tungsten boride compounds by SHS method. Black-Right-Pointing-Pointer Mg containing byproducts were leached out by using a hot aqueous HCl media. Black-Right-Pointing-Pointer The ratio of W{sub 2}B{sub 5}/WB was found to be {approx}2.0 containing minor phases of W{sub 2}B and W. - Abstract: In the present study, the production parameters of tungsten boride compounds by self-propagating high-temperature synthesis (SHS) method and following leaching process were investigated. In the SHS stage, the products consisting of tungsten borides, magnesium oxide, magnesium borate, and also minor compounds were obtained by using different initial molar ratios of WO{sub 3}, Mg and B{sub 2}O{sub 3} as starting materials. In the leaching step, Mg containing byproducts, i.e. MgO and Mg{sub 3}B{sub 2}O{sub 6}, existed in the selected SHS product synthesized at 1:8:2.5 initial molar ratio of WO{sub 3}:Mg:B{sub 2}O{sub 3} were leached out by using aqueous HCl solution to obtain clean tungsten boride compounds at different experimental parameters which are time, acid concentration and temperature. The acid leaching experiments of the SHS product showed that optimum leaching conditions could be achieved by using 5.8 M HCl at 1/10 S/L ratio and the temperature of 80 Degree-Sign C for 60 min.
17. On magnetic properties of thorium and uranium borides and Usub(1-x)Thsub(x)Bsub(4) solid solutions
International Nuclear Information System (INIS)
Chachkhiani, Z.B.; Chachkhiani, L.G.; Chechernikov, V.I.; Slovyanskikh, V.K.
1982-01-01
The dependence of magnetic susceptibility on temperature of UB 4 compound and Usub(1-x)Thsub(x)Bsub(4) alloy system in the 140-1300 K temperature range is investigated. It has been found that paramagnetic susceptibility does not obeys the Curie-Weiss law. The interpretation of experimental results is performed on the basis of Stoner model of collectivized electrons which permits also to explain the magnetic properites of other thorium and uranium borides
18. Bismuth ferrite as low-loss switchable material for plasmonic waveguide modulator
DEFF Research Database (Denmark)
Babicheva, Viktoriia; Zhukovsky, Sergei; Lavrinenko, Andrei
2014-01-01
We propose new designs of plasmonic modulators, which can beused for dynamic signal switching in photonic integrated circuits. We studyperformance of a plasmonic waveguide modulator with bismuth ferrite as atunable material. The bismuth ferrite core is sandwiched between metalplates (metal...
19. Controlled synthesis of bismuth oxyiodide toward optimization of photocatalytic performance
Energy Technology Data Exchange (ETDEWEB)
Liao, Chenxing; Ma, Zhijun [State Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Wushan Road 381, Guangzhou 510641 (China); Chen, Xiaofeng, E-mail: [email protected] [Biomaterials Research Institute, School of Materials Science and Engineering, South China University of Technology, Wushan Road 381, Guangzhou 510641 (China); He, Xin [School of Applied Physics and Materials, Wuyi University, Jiangmen 529020 (China); Qiu, Jianrong, E-mail: [email protected] [State Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Wushan Road 381, Guangzhou 510641 (China)
2016-11-30
Highlights: • Different bismuth oxyiodide was synthesized. • The hollow Bi{sub 4}O{sub 5}I{sub 2} microspheres was obtained. • Formation mechanism of the hollow structure was discussed in detail. - Abstract: A new investigation on the variation rule of the structure, morphology, chemical composition and photocatalytic performance of bismuth oxyiodide synthesized by solvothermal method as a function of reaction conditions was performed here. The composition and morphology of the product could be determined by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The results revealed that the particle size together with content of iodide in bismuth oxyiodide decrease with the increase of the concentration of reaction precursors. Hollow Bi{sub 4}O{sub 5}I{sub 2} microsphere with specific surface area as high as 120.88 m{sup 2} g{sup −1} can be easily synthesized when the concentration of the reaction precursors finally increased to 62.5 mM. Photocatalytic water purification performance of the as-prepared samples was evaluated by using Rhodamine B (RhB) as a model contaminant. The results revealed that the hollow Bi{sub 4}O{sub 5}I{sub 2} exhibited the best performance among all the bismuth oxyodide synthesized here for the degradation of RhB under visible light irradiation. Meanwhile, the formation mechanism of the hierarchical hollow structure of bismuth oxyiodide was investigated by the dissolution-recrystallization mechanism.
International Nuclear Information System (INIS)
Bouchter, J.C.; Courouau, J.L.; Dufour, P.; Guidez, J.; Latge, C.; Martinelli, L.; Renault, C.; Rimpault, G.
2014-01-01
1. Oxygen holes and hybridization in the bismuthates
Science.gov (United States)
Khazraie, Arash; Foyevtsova, Kateryna; Elfimov, Ilya; Sawatzky, George A.
2018-02-01
Motivated by the recently renewed interest in the superconducting bismuth perovskites, we investigate the electronic structure of the parent compounds A BiO3 (A = Sr, Ba) using ab initio methods and tight-binding (TB) modeling. We use the density functional theory (DFT) in the local density approximation (LDA) to understand the role of various interactions in shaping the A BiO3 band structure near the Fermi level. It is established that interatomic hybridization involving Bi-6 s and O-2 p orbitals plays the most important role. Based on our DFT calculations, we derive a minimal TB model and demonstrate that it can describe the properties of the band structure as a function of lattice distortions, such as the opening of a charge gap with the onset of the breathing distortion and the associated condensation of holes onto a1 g-symmetric molecular orbitals formed by the O-2 pσ orbitals on collapsed octahedra. We also derive a single band model involving the hopping of an extended molecular orbital involving both Bi-6 s and a linear combination of six O-2 p orbitals which provides a very good description of the dispersion and band gaps of the low energy scale bands straddling the chemical potential.
2. Laser Spectroscopy of Neutron Rich Bismuth Isotopes
CERN Multimedia
2002-01-01
%IS344 :\\\\ \\\\ The aim of the experiment is to measure the optical isotope shifts and hyperfine structures of bismuth isotopes across the N=126 shell closure in order to extract the change in mean square charge radii ($\\delta\\langle r^{2}\\rangle$) and static moments. These include the first isotones of lead to be measured directly above the shell closure and will provide new information on the systematics of the kink ($\\delta\\langle r^{2}\\rangle)$ seen in the lead isotopic chain. After two very successful runs the programme has been extended to include the neutron deficient isotopes below $^{201}$Bi to study the systematics across the $i_{13/2}$ neutron sub-shell closure at N=118.\\\\ \\\\ During the initial 2 runs (9 shifts) the isotope shifts and hyperfine structures of three new isotopes, $^{210,212,213}$Bi and the 9$^{-}$ isomer of $^{210}$Bi have been measured. The accuracy of the previous measurements of $^{205,206,208}$Bi have been greatly improved. The samples of $^{208,210,210^{m}}$Bi were prepared by c...
3. Tunneling in cuprate and bismuthate superconductors
International Nuclear Information System (INIS)
Zasadzinski, J.F.; Huang, Qiang; Tralshawala, N.
1991-10-01
Tunneling measurements using a point-contact technique are reported for the following high temperature superconducting oxides: Ba 1-x K x BiO 3 (BKBO), Nd 2-x Ce x CuO 4 (NCCO), Bi 2 Sr 2 CaCu 2 O 7 (BSCCO) and Tl 2 Ba 2 CaCu 2 O x (TBCCO). For the bismuthate, BKBO, ideal, S-I-N tunneling characteristics are observed using a Au tip. The normalized conductance is fitted to a BCS density of states and thermal smearing only proving there is no fundamental limitation in BKBO for device applications. For the cuprates, the normalized conductance displays BCS-like characteristics, but with a broadening larger than from thermal smearing. Energy gap values are presented for each material. For BKBO and NCCO the Eliashberg functions, α 2 F(ω), obtained from the tunneling are shown to be in good agreement with neutron scattering results. Proximity effect tunneling studies are reported for Au/BSCCO bilayers and show that the energy gap of BSCCO can be observed through Au layers up to 600 Angstrom thick
4. Use of Russian technology of ship reactors with lead-bismuth coolant in nuclear power
International Nuclear Information System (INIS)
Zrodnikov, A.V.; Chitaykin, V.I.; Gromov, B.F.; Grigoryv, O.G.; Dedoul, A.V.; Toshinsky, G.I.; Dragunov, Yu.G.; Stepanov, V.S.
2000-01-01
The experience of using lead-bismuth coolant in Russian nuclear submarine reactors has been presented. The fundamental statements of the concept of using the reactors cooled by lead-bismuth alloy in nuclear power have been substantiated. The results of developments for using lead bismuth coolant in nuclear power have been presented. (author)
5. Prognostic Value of Bismuth Typing and Modified T-stage in Hilar Cholangiocarcinoma
Directory of Open Access Journals (Sweden)
Shengen Yi
2015-01-01
Conclusion: The majority of our patients with HCC were characterized as Subtype IV in Bismuth typing and Stage T3 in modified T-stage. Both Bismuth typing and modified T-stage showed prognostic value in HCC. Compared with Bismuth typing, modified T-stage is a better indicator of the resectability of HCC.
6. Microstructure and electrical properties of bismuth and bismuth oxide deposited by magnetron sputtering UBM
International Nuclear Information System (INIS)
Otalora B, D. M.; Dussan, A.; Olaya F, J. J.
2015-01-01
In this work, bismuth (Bi) and bismuth oxide (Bi 2 O 3 ) thin films were prepared, at room temperature, by Sputtering Unbalanced Magnetron (UBM - Unbalance Magnetron) technique under glass substrates. Microstructural and electrical properties of the samples were studied by X-ray diffraction (XRD) and System for Measuring Physical Properties - PPMS (Physical Property Measurement System). Dark resistivity of the material was measured for a temperature range between 100 and 400 K. From the XRD measurements it was observed a polycrystalline character of the Bi associated to the presence of phases above the main peak, 2θ = 26.42 grades and a growth governed by a rhombohedral structure. Crystal parameters were obtained for both compounds, Bi and Bi 2 O 3 . From the analysis of the spectra of the conductivity as a function of temperature, it was established that the transport mechanism that governs the region of high temperature (T>300 K) is thermally activated carriers. From conductivity measurements the activation energies were obtained of 0.0094 eV and 0.015 eV for Bi 2 O 3 and Bi, respectively. (Author)
7. Suppression of Boride Formation in Transient Liquid Phase Bonding of Pairings of Parent Superalloy Materials with Different Compositions and Grain Structures and Resulting Mechanical Properties
Science.gov (United States)
Steuer, Susanne; Singer, Robert F.
2014-07-01
Two Ni-based superalloys, columnar grained Alloy 247 and single-crystal PWA1483, are joined by transient liquid phase bonding using an amorphous brazing foil containing boron as a melting point depressant. At lower brazing temperatures, two different morphologies of borides develop in both base materials: plate-like and globular ones. Their ratio to each other is temperature dependent. With very high brazing temperatures, the deleterious boride formation in Alloy 247 can be totally avoided, probably because the three-phase-field moves to higher alloying element contents. For the superalloy PWA1483, the formation of borides cannot be completely avoided at high brazing temperatures as incipient melting occurs. During subsequent solidification of these areas, Chinese-script-like borides precipitate. The mechanical properties (tensile tests at room and elevated temperatures and short-term creep rupture tests at elevated temperatures) for brazed samples without boride precipitation are very promising. Tensile strengths and creep times to 1 pct strain are comparable, respectively, higher than the ones of the weaker parent material for all tested temperatures and creep conditions (from 90 to 100 pct rsp. 175 to 250 pct).
8. A superconducting battery material: Lithium gold boride (LiAu3B)
Science.gov (United States)
Aydin, Sezgin; Şimşek, Mehmet
2018-04-01
The superconducting and potential cathode material properties of ternary boride of LiAu3B have been investigated by density functional first principles. The Li-concentration effects on the actual electronic and structural properties, namely the properties of LixAu9B3 (x = 0, 1, 2) sub-systems are studied. It is remarkably shown that the existence of Li-atoms has no considerable effect on the structural properties of Au-B skeleton in LiAu3B. Then, it can be offered as a potential cathode material for Li-ion batteries with the very small volume deviation of 0.42%, and the suitable average open circuit voltage of ∼1.30 V. Furthermore, the vibrational and superconducting properties such as electron-phonon coupling constant (λ) and critical temperature (Tc) of LiAu3B are studied. The calculated results suggest that LiAu3B should be a superconductor with Tc ∼5.8 K, also.
9. Boride Formation Induced by pcBN Tool Wear in Friction-Stir-Welded Stainless Steels
Science.gov (United States)
Park, Seung Hwan C.; Sato, Yutaka S.; Kokawa, Hiroyuki; Okamoto, Kazutaka; Hirano, Satoshi; Inagaki, Masahisa
2009-03-01
The wear of polycrystalline cubic boron nitride (pcBN) tool and its effect on second phase formation were investigated in stainless steel friction-stir (FS) welds. The nitrogen content and the flow stress were analyzed in these welds to examine pcBN tool wear. The nitrogen content in stir zone (SZ) was found to be higher in the austenitic stainless steel FS welds than in the ferritic and duplex stainless steel welds. The flow stress of austenitic stainless steels was almost 1.5 times larger than that of ferritic and duplex stainless steels. These results suggest that the higher flow stress causes the severe tool wear in austenitic stainless steels, which results in greater nitrogen pickup in austenitic stainless steel FS welds. From the microstructural observation, a possibility was suggested that Cr-rich borides with a crystallographic structure of Cr2B and Cr5B3 formed through the reaction between the increased boron and nitrogen and the matrix during FS welding (FSW).
10. Bismuth iron oxide thin films using atomic layer deposition of alternating bismuth oxide and iron oxide layers
Energy Technology Data Exchange (ETDEWEB)
Puttaswamy, Manjunath; Vehkamäki, Marko [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Kukli, Kaupo, E-mail: [email protected] [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); University of Tartu, Institute of Physics, W. Ostwald 1, EE-50411 Tartu (Estonia); Dimri, Mukesh Chandra [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Kemell, Marianna; Hatanpää, Timo; Heikkilä, Mikko J. [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Mizohata, Kenichiro [University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 Helsinki (Finland); Stern, Raivo [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Ritala, Mikko; Leskelä, Markku [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland)
2016-07-29
Bismuth iron oxide films with varying contributions from Fe{sub 2}O{sub 3} or Bi{sub 2}O{sub 3} were prepared using atomic layer deposition. Bismuth (III) 2,3-dimethyl-2-butoxide, was used as the bismuth source, iron(III) tert-butoxide as the iron source and water vapor as the oxygen source. The films were deposited as stacks of alternate Bi{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} layers. Films grown at 140 °C to the thickness of 200–220 nm were amorphous, but crystallized upon post-deposition annealing at 500 °C in nitrogen. Annealing of films with intermittent bismuth and iron oxide layers grown to different thicknesses influenced their surface morphology, crystal structure, composition, electrical and magnetic properties. Implications of multiferroic performance were recognized in the films with the remanent charge polarization varying from 1 to 5 μC/cm{sup 2} and magnetic coercivity varying from a few up to 8000 A/m. - Highlights: • Bismuth iron oxide thin films were grown by atomic layer deposition at 140 °C. • The major phase formed in the films upon annealing at 500 °C was BiFeO{sub 3}. • BiFeO{sub 3} films and films containing excess Bi favored electrical charge polarization. • Slight excess of iron oxide enhanced saturative magnetization behavior.
11. Characterization of bismuth nanospheres deposited by plasma focus device
Energy Technology Data Exchange (ETDEWEB)
Ahmad, M., E-mail: [email protected] [IBA Laboratory, Chemistry Department, Atomic Energy Commission of Syria, P.O. Box 6091, Damascus (Syrian Arab Republic); Al-Hawat, Sh.; Akel, M. [Physics Department, Atomic Energy Commission of Syria, P.O. Box 6091, Damascus (Syrian Arab Republic); Mrad, O. [Chemistry Department, Atomic Energy Commission of Syria, P.O. Box 6091, Damascus (Syrian Arab Republic)
2015-02-14
A new method for producing thin layer of bismuth nanospheres based on the use of low energy plasma focus device is demonstrated. Various techniques such as scanning electron microscopy, Rutherford backscattering spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been used to characterize the morphology and the composition of the nanospheres. Experimental parameters may be adjusted to favour the formation of bismuth nanospheres instead of microspheres. Therefore, the formation of large surface of homogeneous layer of bismuth nanospheres with sizes of below 100 nm can be obtained. The natural snowball phenomenon is observed to be reproduced in nanoscale where spheres roll over the small nanospheres and grow up to bigger sizes that can reach micro dimensions. The comet-like structure, a reverse phenomenon to snowball is also observed.
12. Inexpensive laser-induced surface modification in bismuth thin films
Energy Technology Data Exchange (ETDEWEB)
2015-05-01
Highlights: • Laser-induced microbumps were formed on bismuth films using a simple, low-cost, laser setup. • The patterns, similar to those typically obtained with high-power lasers, were characterized. • Control of laser ablation conditions is critical in the fabrication of surface microbumps. - Abstract: In this work, we present results on texturing a 500 nm thick bismuth film, deposited by sputtering onto a glass slide using a low-cost homemade, near-infrared pulsed laser platform. A 785 nm laser diode of a CD–DVD pickup head was precisely focused on the sample mounted on a motorized two-axis translation stage to generate localized surface microbumps on the bismuth films. This simple method successfully transferred desired micropatterns on the films in a computer-numerical control fashion. Irradiated zones were characterized by atomic force microscopy and scanning electron microscopy. It was observed that final results are strongly dependent on irradiation parameters.
13. Characterization of bismuth nanospheres deposited by plasma focus device
International Nuclear Information System (INIS)
2015-01-01
A new method for producing thin layer of bismuth nanospheres based on the use of low energy plasma focus device is demonstrated. Various techniques such as scanning electron microscopy, Rutherford backscattering spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy have been used to characterize the morphology and the composition of the nanospheres. Experimental parameters may be adjusted to favour the formation of bismuth nanospheres instead of microspheres. Therefore, the formation of large surface of homogeneous layer of bismuth nanospheres with sizes of below 100 nm can be obtained. The natural snowball phenomenon is observed to be reproduced in nanoscale where spheres roll over the small nanospheres and grow up to bigger sizes that can reach micro dimensions. The comet-like structure, a reverse phenomenon to snowball is also observed
14. MES lead bismuth forced circulation loop and test results
International Nuclear Information System (INIS)
Ono, Mikinori; Mine, Tatsuya; Kitano, Teruaki; Kamata, Kin-ya
2003-01-01
Liquid lead-bismuth is a promising material as future reactor coolant or intensive neutron source material for accelerator driven system (ADS). Mitsui Engineering and Shipbuilding Co., Ltd. (MES) completed lead-bismuth coolant (LBC) forced circulation loop in May 2001 and acquired engineering data on economizer, electro magnetic pump, electro magnetic flow meter and so on. For quality control of LBC, oxygen sensor and filtering element are developing using some hydrogen and moisture mixed gases. Structural materials corrosion test for accelerator driver system (ADS) will start soon. And thermal hydraulic test for ADS will start in tree years. (author)
15. Hydrolysis studies on bismuth nitrate: synthesis and crystallization of four novel polynuclear basic bismuth nitrates.
Science.gov (United States)
Miersch, L; Rüffer, T; Schlesinger, M; Lang, H; Mehring, M
2012-09-03
Hydrolysis of Bi(NO(3))(3) in aqueous solution gave crystals of the novel compounds [Bi(6)O(4)(OH)(4)(NO(3))(5)(H(2)O)](NO(3)) (1) and [Bi(6)O(4)(OH)(4)(NO(3))(6)(H(2)O)(2)]·H(2)O (2) among the series of hexanuclear bismuth oxido nitrates. Compounds 1 and 2 both crystallize in the monoclinic space group P2(1)/n but show significant differences in their lattice parameters: 1, a = 9.2516(6) Å, b = 13.4298(9) Å, c = 17.8471(14) Å, β = 94.531(6)°, V = 2210.5(3) Å(3); 2, a = 9.0149(3) Å, b = 16.9298(4) Å, c = 15.6864(4) Å, β = 90.129(3)°, V = 2394.06(12) Å(3). Variation of the conditions for partial hydrolysis of Bi(NO(3))(3) gave bismuth oxido nitrates of even higher nuclearity, [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·4DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·4DMSO] (3) and [{Bi(38)O(45)(NO(3))(24)(DMSO)(26)}·2DMSO][{Bi(38)O(45)(NO(3))(24)(DMSO)(24)}·0.5DMSO] (5), upon crystallization from DMSO. Bismuth oxido clusters 3 and 5 crystallize in the triclinic space group P1 both with two crystallographically independent molecules in the asymmetric unit. The following lattice parameters are observed: 3, a = 20.3804(10) Å, b = 20.3871(9) Å, c = 34.9715(15) Å, α = 76.657(4)°, β = 73.479(4)°, γ = 60.228(5)°, V = 12021.7(9) Å(3); 5, a = 20.0329(4) Å, b = 20.0601(4) Å, c = 34.3532(6) Å, α = 90.196(1)°, β = 91.344(2)°, γ = 119.370(2)°, V = 12025.8(4) Å(3). Differences in the number of DMSO molecules (coordinated and noncoordinated) and ligand (nitrate, DMSO) coordination modes are observed.
16. Computer simulation of monolayer growth kinetics of Fe2B phase during the paste-boriding process: Influence of the paste thickness
International Nuclear Information System (INIS)
Keddam, M.
2006-01-01
This paper deals with the effect of boron paste thickness on the study of the monolayer growth kinetics of Fe 2 B phase forming on AISI 1045 steel by the paste-boriding process. A mathematical diffusion model based on the Fick's phenomenological equations was applied in order to estimate the growth rate constant at (Fe 2 B/γ-Fe) interface, the layer thickness of iron boride as well as the associated mass gain depending on the boriding parameters such as time, temperature and surface boron concentration related to the boron paste thickness. The simulation results are found to be in a fairly good agreement with the experimental data derived from the literature
17. Bismuth oxyfluoride @ CMK-3 nanocomposite as cathode for lithium ion batteries
Science.gov (United States)
Ni, Dan; Sun, Wang; Xie, Liqiang; Fan, Qinghua; Wang, Zhenhua; Sun, Kening
2018-01-01
Bismuth oxyfluoride impregnated CMK-3 nanocomposite is synthesized by a facile nanocasting approach. Mesoporous carbon CMK-3 can suppress the aggregation and growth of bismuth oxyfluoride particles and offer rapid electron and Li ion passageways. Bismuth oxyfluoride nanoparticles are embedded in the mesoporous channels with particle size less than 20 nm. The bismuth oxyfluoride@CMK-3 nanocomposite maintains 148 mA h g-1 after 40 cycles with the capacity from both the bismuth oxyfluoride and the functional groups on the mesoporous carbon. The hybrid with confined bismuth oxyfluoride nanoparticles, conductive carbon network, and oxygen functional groups on the carbon matrix exhibits higher capacity and cycling stability than bulk bismuth oxyfluoride particles when used as lithium ion batteries cathode.
18. Temperature gradient compatibility tests of some refractory metals and alloys in bismuth and bismuth--lithium solutions
International Nuclear Information System (INIS)
DiStefano, J.R.; Cavin, O.B.
1976-11-01
Quartz, T-111, and Mo thermal-convection loop tests were conducted at temperatures up to 700 0 C (100 0 C ΔT) to determine the compatibility of several refractory metals/alloys with bismuth and bismuth-lithium solutions for molten salt breeder reactor applications. Methods of evaluation included weight change measurements, metallographic examination, chemical and electron microprobe analysis, and mechanical properties tests. Molybdenum, T-111, and TA--10 percent W appear to be the most promising containment materials, while niobium and iron-based alloys are unacceptable
19. Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and Their Structure-Property Relations
Directory of Open Access Journals (Sweden)
Lkhamsuren Bayarjargal
2011-09-01
Full Text Available Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p; T stability, compressibility and hardness is described as obtained from experiments.
20. Synthesis of Binary Transition Metal Nitrides, Carbides and Borides from the Elements in the Laser-Heated Diamond Anvil Cell and Their Structure-Property Relations
Science.gov (United States)
Friedrich, Alexandra; Winkler, Björn; Juarez-Arellano, Erick A.; Bayarjargal, Lkhamsuren
2011-01-01
Transition metal nitrides, carbides and borides have a high potential for industrial applications as they not only have a high melting point but are generally harder and less compressible than the pure metals. Here we summarize recent advances in the synthesis of binary transition metal nitrides, carbides and borides focusing on the reaction of the elements at extreme conditions generated within the laser-heated diamond anvil cell. The current knowledge of their structures and high-pressure properties like high-(p,T) stability, compressibility and hardness is described as obtained from experiments. PMID:28824101
1. Measured and evaluated neutron cross sections of elemental bismuth
International Nuclear Information System (INIS)
Smith, A.; Guenther, P.; Smith, D.; Whalen, J.; Howerton, R.
1980-04-01
Neutron total cross sections of elemental bismuth are measured with broad resolution from 1.2 to 4.5 MeV to accuracies of approx. = 1%. Neutron-differential-elastic-scattering cross sections of bismuth are measured from 1.5 to 4.0 MeV at incident neutron energy intervals of approx.< 0.2 MeV over the scattered-neutron angular range approx. = 20 to 160 deg. Differential neutron cross sections for the excitation of observed states in bismuth at 895 +- 12, 1606 +- 14, 2590 +- 15, 2762 +- 29, 3022 +- 21, and 3144 +- 15 keV are determined at incident neutron energies up to 4.0 MeV. An optical-statistical model is deduced from the measured values. This model, the present experimental results, and information available elsewhere in the literature are used to construct a comprehensive evaluated nuclear data file for elemental bismuth in the ENDF format. The evaluated file is particularly suited to the neutronic needs of the fusion-fission hybrid designer. 87 references, 10 figures, 6 tables
2. The reduction of background signal in bismuth germanate scintillators
International Nuclear Information System (INIS)
Lewis, T.A.
1986-07-01
Bismuth germanate (BGO) is one of several new scintillator materials developed in recent years. It has similar energy resolution (6-8%) to sodium iodide (NaI) but it is non-hygroscopic, has a much better Peak-to-Compton ratio and a stopping power about 2.3 times greater than NaI. For counting activated foils it represents an improvement on NaI for high efficiency counting where the resolution of a germanium spectrometer is not required. Two scintillators bought for this purpose were found to have a higher than expected background signal between 500 keV and 2 MeV which was traced to Bi207, an active isotope of bismuth with a 38 year half-life and not listed as occurring naturally. Reference to the manufacturer showed all crystals to be similarly contaminated. It is speculated that this active isotope arises from cosmic proton activation of associated lead in the ore from which the bismuth is extracted. Although not confirmed rigorously it has been shown that bismuth extracted from ore with a low lead content does not contain Bi207. Scintillators have been manufactured from uncontaminated material and reductions in the background signal of more than an order of magnitude have been achieved. This reduction will be of immediate benefit for monitoring nickel foils (fast flux monitors) activated in zero-energy reactors and should also permit the exploitation of other low probability reactions previously not thought to be feasible. (author)
3. Short-term static corrosion tests in lead-bismuth
Science.gov (United States)
Soler Crespo, L.; Martín Muñoz, F. J.; Gómez Briceño, D.
2001-07-01
Martensitic steels have been proposed to be used as structural materials and as spallation target window in hybrid systems devoted to the transmutation of radioactive waste of long life and high activity. However, their compatibility with lead-bismuth in the operating conditions of these systems depends on the existence of a protective layer such as an oxide film. The feasibility of forming and maintaining an oxide layer or maintaining a pre-oxidised one has been studied. Martensitic steel F82Hmod. (8% Cr) has been tested in lead-bismuth under static and isothermal conditions at 400°C and 600°C. In order to study the first stages of the interaction between the steel and the eutectic, short-term tests (100 and 665 h) have been carried out. Pre-oxidised and as-received samples have been tested in atmospheres with different oxidant potential. For low oxygen concentration in lead-bismuth due to unexpected oxygen consumption in the experimental device, dissolution of as-received F82Hmod. occurs and pre-oxidation does not prevent the material dissolution. For high oxygen concentration, the pre-oxidation layer seems to improve the feasibility of protecting stainless steels controlling the oxygen potential of lead-bismuth with a gas phase.
4. Short-term static corrosion tests in lead-bismuth
International Nuclear Information System (INIS)
Soler Crespo, L.; Martin Munoz, F.J.; Gomez Briceno, D.
2001-01-01
Martensitic steels have been proposed to be used as structural materials and as spallation target window in hybrid systems devoted to the transmutation of radioactive waste of long life and high activity. However, their compatibility with lead-bismuth in the operating conditions of these systems depends on the existence of a protective layer such as an oxide film. The feasibility of forming and maintaining an oxide layer or maintaining a pre-oxidised one has been studied. Martensitic steel F82Hmod. (8% Cr) has been tested in lead-bismuth under static and isothermal conditions at 400 o C and 600 o C. In order to study the first stages of the interaction between the steel and the eutectic, short-term tests (100 and 665 h) have been carried out. Pre-oxidised and as-received samples have been tested in atmospheres with different oxidant potential. For low oxygen concentration in lead-bismuth due to unexpected oxygen consumption in the experimental device, dissolution of as-received F82Hmod. occurs and pre-oxidation does not prevent the material dissolution. For high oxygen concentration, the pre-oxidation layer seems to improve the feasibility of protecting stainless steels controlling the oxygen potential of lead-bismuth with a gas phase
5. Pairing from dynamically screened Coulomb repulsion in bismuth
Science.gov (United States)
Ruhman, Jonathan; Lee, Patrick A.
2017-12-01
Recently, Prakash et al. have discovered bulk superconductivity in single crystals of bismuth, which is a semimetal with extremely low carrier density. At such low density, we argue that conventional electron-phonon coupling is too weak to be responsible for the binding of electrons into Cooper pairs. We study a dynamically screened Coulomb interaction with effective attraction generated on the scale of the collective plasma modes. We model the electronic states in bismuth to include three Dirac pockets with high velocity and one hole pocket with a significantly smaller velocity. We find a weak-coupling instability, which is greatly enhanced by the presence of the hole pocket. Therefore we argue that bismuth is the first material to exhibit superconductivity driven by retardation effects of Coulomb repulsion alone. By using realistic parameters for bismuth we find that the acoustic plasma mode does not play the central role in pairing. We also discuss a matrix element effect, resulting from the Dirac nature of the conduction band, which may affect Tc in the s -wave channel without breaking time-reversal symmetry.
6. Synthesis and structural characterization of Ce-doped bismuth titanate
International Nuclear Information System (INIS)
2009-01-01
Ce-modified bismuth titanate nanopowders Bi 4-x Ce x Ti 3 O 12 (x ≤ 1) have been synthesized using a coprecipitation method. DTA/TG, FTIR, XRD, SEM/EDS and BET methods were used in order to investigate the effect of Ce-substitution on the structure, morphology and sinterability of the obtained powders. The phase structure investigation revealed that after calcinations at 600 deg. C powder without Ce addition exhibited pure bismuth titanate phase; however, powders with Ce (x = 0.25, 0.5 and 0.75) had bismuth titanate pyrochlore phase as the second phase. The strongest effect of Ce addition on the structure was noted for the powder with the highest amount of Ce (x = 1) having a cubic pyrochlore structure. The presence of pure pyrochlore phase was explained by its stabilization due to the incorporation of cerium ions in titanate structure. Ce-modified bismuth titanate ceramic had a density over 95% of theoretical density and the fracture in transgranular manner most probably due to preferable distribution of Ce in boundary region
7. Void worths in subcritical cores cooled by lead-bismuth
International Nuclear Information System (INIS)
Wallenius, Janne; Tucek, Kamil; Gudowski, Waclaw
2001-01-01
The introduction lead-bismuth coolant in accelerator driven transmutation systems (ADS) was: good neutron economy (higher source efficiency); natural circulation possible (decay heat removal); synergy with spallation target (simplified coolant management); high temperature of boiling (larger overpower margin); smaller void worths (operation at higher k-values). This paper deals with different aspects of the void worths in JAERI ADS
8. Preparation of Ferroelectric Thin Films of Bismuth Layer Structured Compounds
Science.gov (United States)
Watanabe, Hitoshi; Mihara, Takashi; Yoshimori, Hiroyuki; Araujo, Carlos
1995-09-01
Ferroelectric thin films of bismuth layer structured compounds, SrBi2Ta2O9, SrBi2Nb2O9, SrBi4Ti4O15 and their solid solutions, were formed onto a sputtered platinum layer on a silicon substrate using spin-on technique and metal-organic decomposition (MOD) method. X-ray diffraction (XRD) analysis and some electrical measurements were performed on the prepared thin films. XRD results of SrBi2(Ta1- x, Nb x)2O9 films (0≤x≤1) showed that niobium ions substitute for tantalum ions in an arbitrary ratio without any change of the layer structure and lattice constants. Furthermore, XRD results of SrBi2 xTa2O9 films (0≤x≤1.5) indicated that the formation of the bismuth layer structure does not always require an accurate bismuth content. The layer structure was formed above 50% of the stoichiometric bismuth content in the general formula. SrBi2(Ta1- x, Nb x)2O9 films with various Ta/Nb ratios have large enough remanent polarization for nonvolatile memory application and have shown high fatigue resistance against 1011 cycles of full switching of the remanent polarization. Mixture films of the three compounds were also investigated.
9. Ultrafast electron diffraction studies of optically excited thin bismuth films
International Nuclear Information System (INIS)
Rajkovic, Ivan
2008-01-01
This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)
10. Bismuth Ferrite for Active Control of Surface Plasmon Polariton Modes
DEFF Research Database (Denmark)
Babicheva, Viktoriia; Zhukovsky, Sergei; Lavrinenko, Andrei
2014-01-01
We propose and investigate several layouts of m etal-insulator-metal waveguide with active core which can be utilized for dynamic switching in photonic integrated circuits. The active material, bismuth ferrite (BiFeO3), is sandwiched between metal plates and changes i ts refractive index through...
11. Ultrafast electron diffraction studies of optically excited thin bismuth films
Energy Technology Data Exchange (ETDEWEB)
Rajkovic, Ivan
2008-10-21
This thesis contains work on the design and the realization of an experimental setup capable of providing sub-picosecond electron pulses for ultrafast electron diffraction experiments, and performing the study of ultrafast dynamics in bismuth after optical excitation using this setup. (orig.)
12. Phase transition of bismuth telluride thin films grown by MBE
DEFF Research Database (Denmark)
Fülöp, Attila; Song, Yuxin; Charpentier, Sophie
2014-01-01
A previously unreported phase transition between Bi2Te3 and Bi4Te3 in bismuth telluride grown by molecular beam epitaxy is recorded via XRD, AFM, and SIMS observations. This transition is found to be related to the Te/Bi beam equivalent pressure (BEP) ratio. BEP ratios below 17 favor the formation...
13. Possible multigap type-I superconductivity in the layered boride RuB2
Science.gov (United States)
Singh, Jaskaran; Jayaraj, Anooja; Srivastava, D.; Gayen, S.; Thamizhavel, A.; Singh, Yogesh
2018-02-01
The structure of the layered transition-metal borides A B2 (A =Os,Ru ) is built up by alternating T and B layers with the B layers forming a puckered honeycomb. Here we report superconducting properties of RuB2 with a Tc≈1.5 K using measurements of the magnetic susceptibility versus temperature T , magnetization M versus magnetic field H , resistivity versus T , and heat capacity versus T at various H . We observe a reduced heat capacity anomaly at Tc given by Δ C /γ Tc≈1.1 suggesting multigap superconductivity. Strong support for this is obtained by the successful fitting of the electronic specific heat data to a two-gap model with gap values Δ1/kBTc≈1.88 and Δ2/kBTc≈1.13 . Additionally, M versus H measurements reveal a behavior consistent with type-I superconductivity. This is confirmed by comparing the experimental critical field ≈122 Oe obtained from extrapolation to T =0 of the H -T phase diagram, with an estimate of the T =0 thermodynamic critical field ≈114 Oe. Additionally, the Ginzburg-Landau parameter was estimated to be κ ≈0.1 -0.66 . These results strongly suggest multigap type-I superconductivity in RuB2. We also calculate the band structure and obtain the Fermi surface for RuB2. The Fermi surface consists of one quasi-two-dimensional sheet and two concentric ellipsoidal sheets very similar to OsB2. An additional small fourth sheet is also found for RuB2. RuB2 could thus be an example of a multigap type-I superconductor.
14. AB initio energetics of lanthanum substitution in ferroelectric bismuth titanate
International Nuclear Information System (INIS)
Shah, S.H.
2012-01-01
Density functional theory based electronic structure calculations play a vital role in understanding, controlling and optimizing physical properties of materials at microscopic level. In present study system of interest is bismuth titanate (Bi/sub 4/Ti/sub 3/O/sub 12/)/(BIT) which has wide range of applications such as a high temperature piezoelectric and one of the best material for memory devices. However, it also suffers from serious issues such as oxygen vacancies which degrade its performance as a memory element and piezoelectric material. In this context, the bulk and defect properties of orthorhombic bismuth titanate (Bi/sub 4/Ti/sub 3/O/sub 12/) and bismuth lanthanum titanate (Bi/sub 3.25/La/sub 0.75/Ti/sub 3/O/sub 12/)/(BLT, x=0.75) were investigated by using first principles calculations and atomistic thermodynamics. Heats of formation, valid chemical conditions for synthesis, lanthanum substitution energies and oxygen and bismuth vacancy formation energies were computed. The study improves understanding of how native point defects and substitutional impurities influence the ferroelectric properties of these layered perovskite materials. It was found that lanthanum incorporation could occur on either of the two distinct bismuth sites in the structure and that the effect of substitution is to increase the formation energy of nearby native oxygen vacancies. The results provide direct atomistic evidence over a range of chemical conditions for the suggestion that lanthanum incorporation reduces the oxygen vacancy concentration. Oxygen vacancies contribute to ferroelectric fatigue by interacting strongly with domain walls and therefore a decrease in their concentration is beneficial. (orig./A.B.)
15. Efficient enhancement of bismuth NIR luminescence by aluminum and its mechanism in bismuth doped germanate laser glass
DEFF Research Database (Denmark)
Wang, L.P.; Tan, L.L.; Yue, Yuanzheng
2016-01-01
As a new member of laser glass family, bismuth-doped glasses have received rising interests due to the application of fiber amplifiers and laser sources in the new spectral range for the next-generation optical communication system. For practical application of the glasses, it must be considered ...
16. Formation of gas-phase π-allyl radicals from propylene over bismuth oxide and γ-bismuth molybdate catalysts
International Nuclear Information System (INIS)
Martir, W.; Lunsford, J.H.
1981-01-01
17. Microstructural evaluation of a low carbon steel submitted to boriding treatment pre and post GTAW welding; Avaliacao microestrutural de um aco de baixo carbono submetido ao tratamento de boretacao pre e pos-soldagem GTAW
Energy Technology Data Exchange (ETDEWEB)
Pollnow, Edilson Nunes; Osorio, Alice Goncalves, E-mail: [email protected], E-mail: [email protected] [Universidade Federal de Pelotas (CDTec/UFPel), Pelotas, RS (Brazil). Centro de Desenvolvimento Tecnologico; Araujo, Douglas Bezerra de, E-mail: [email protected] [Universidade Federal de Uberlandia (FEMEC/UFU), Uberlandia, MG (Brazil). Faculdade de Engenharia Mecanica; Passos, Thais Andrezza dos; Souza, Daniel, E-mail: [email protected], E-mail: [email protected] [Universidade Federal do Rio Grande (EE/FURG), Rio Grande, RS (Brazil). Escola de Engenharia
2017-04-15
Studies on surface engineering area are given great importance due to the improvement that surface modifications provide to materials. With a global market that has the need to provide parts and equipment with extended service life and low cost, to support stringent requests and thus maintain its high performance, surface treatments may bring what was impossible into reality. Among the surface treatments that have received attention recently, we have the thermochemical process of boriding. The boriding process consists of saturate the surface of steels and metal alloys with boron. This saturation provides an increase in the surface properties not inherent to the base metal, such as hardness, resistance to abrasion and corrosion. Although the properties of boriding steels have already been studied, the effects that the boriding process perform on the steel during or after the welding processes are not known. Hence, it is the purpose of this study to evaluate the microstructure of a low carbon steel treated with boriding before and after GTAW welding. The results indicated poor metallurgical weldability of low carbon steel with boride layer, with the presence of solidification cracks. Nonetheless, the steel welded previous to boring treatment presented a more ductile nucleus, with harder surface. Although the values of hardness within the nucleus of the steel had dropped drastically at the welded zone after the boring, the surface of this steel showed higher values of hardness due to the boriding layer. This fact should be considered when applications where wear resistance is needed. (author)
18. Surface decoration through electrostatic interaction leading to enhanced reactivity: Low temperature synthesis of nanostructured chromium borides (CrB and CrB2)
International Nuclear Information System (INIS)
Menaka,; Kumar, Bharat; Kumar, Sandeep; Ganguli, A.K.
2013-01-01
The present study describes a novel low temperature route at ambient pressure for the synthesis of nanocrystalline chromium borides (CrB and CrB 2 ) without using any flux or additives. The favorable and intimate mixing of nanoparticles of chromium acetate (Cr source) and boron forms an active chromium–boron precursor which decomposes at much lower temperature (400 °C) to form CrB (which is ∼1000 °C less than the known ambient pressure synthesis). The chromium acetate nanoparticles (∼5 nm) decorate the larger boron particles (150–200 nm) due to electrostatic interactions resulting from opposing surface charges of boron (zeta potential:+48.101 mV) and chromium acetate (zeta potential:−4.021 mV) in ethanolic medium and is evident in the TEM micrographs. The above method leads to the formation of pure CrB film like structure at 400 °C and nanospheres (40–60 nm) at 600 °C. Also, chromium diboride (CrB 2 ) nanoparticles (25 nm) could be obtained at 1000 °C. - Graphical abstract: Variation of surface charge of reactants, precursor and the products, chromium borides (CrB and CrB 2 ). Highlights: ► Novel borothermal reduction process for synthesis of chromium boride. ► Significant lowering of reaction temperature to obtain nanocrystalline chromium boride. ► Enhanced reactivity due to appropriate surface interactions
19. Equilibrium evaporation test of lead-bismuth eutectic and of tellurium in lead-bismuth
International Nuclear Information System (INIS)
Ohno, Shuji; Nishimura, Masahiro; Hamada, Hirotsugu; Miyahara, Shinya; Sasa, Toshinobu; Kurata, Yuji
2005-01-01
A series of equilibrium evaporation experiment was performed to acquire the essential and the fundamental knowledge about the transfer behavior of lead-bismuth eutectic (LBE) and impurity tellurium in LBE from liquid to gas phase. The experiments were conducted using the transpiration method in which saturated vapor in an isothermal evaporation pot was transported by inert carrier gas and collected outside of the pot. The size of the used evaporation pot is 8 cm inner diameter and 15 cm length. The weight of the LBE pool in the pot is about 500 g. The investigated temperature range was 450degC to 750degC. From this experiment and discussion using the data in literature, we have obtained several instructive and useful data on the LBE evaporation behavior such as saturated vapor pressure of LBE, vapor concentration of Pb, Bi and Bi 2 in LBE saturated gas phase, and activity coefficient of Pb in the LBE. The LBE vapor pressure equation is represented as the sum of Pb, Bi and Bi 2 vapor in the temperature range between 550degC and 750degC as logP[Pa]=10.2-10100/T[k]. The gas-liquid equilibrium partition coefficient of tellurium in LBE is in the range of 10 to 100, with no remarkable temperature dependency between 450degC and 750degC. This research was founded by the Ministry of Education, Culture, Sports, Science and Technology (MEXT). (author)
20. Rapid semi-quantitative determination of bismuth in minerals using ascending paper chromatography (1961)
International Nuclear Information System (INIS)
Agrinier, H.
1961-01-01
The bismuth is separated by a solvent made up of acetone, water, and hydrofluoric and hydrochloric acids. The bismuth is developed with dimercapto-2.5 thio-diazole-1.3.4 and ammonium sulphide. The use of this method for the detection of bismuth in minerals makes it possible to determine the metal at a concentration of 5 x 10 -6 . (author) [fr
1. Influence of bismuth on structural, elastic and spectroscopic properties of Nd{sup 3+} doped Zinc–Boro-Bismuthate glasses
Energy Technology Data Exchange (ETDEWEB)
Gupta, Gaurav; Sontakke, Atul D.; Karmakar, P.; Biswas, K.; Balaji, S.; Saha, R.; Sen, R.; Annapurna, K., E-mail: [email protected]
2014-05-01
The present investigation reports, influence of bismuth addition on structural, elastic and spectral properties of [(99.5−x) {4ZnO−3B_2O_3}−0.5Nd{sub 2}O{sub 3}−x Bi{sub 2}O{sub 3} where x=0, 5, 10, 20, 30, 40, 50 and 60] glasses. The measured FTIR reflectance spectra facilitated a thorough insight of methodical modifications that are arising in the glass structure from borate (build by BO{sub 3} and BO{sub 4} units) to bismuthate (BiO{sub 3} and BiO{sub 6} units) network due to the increase of bismuth content ensuing with a steady decrease in host phonon energy (ν{sub ph}). The elastic properties estimated from measured longitudinal and shear ultrasonic velocities (U{sub L} and U{sub s}) demonstrated the reduction in network rigidity of glasses on Bi{sub 2}O{sub 3} inclusion. The three phenomenological Judd–Ofelt intensity parameters (Ω{sub 2,4,6}) were obtained from recorded absorption spectra of Nd{sup 3+} ions in these glasses and have been used to predict radiative properties as a function of variation in bismuth content. The reduced host phonon energy and high optical basicity effect due to Bi{sub 2}O{sub 3} incorporation remarkably improved the Nd{sup 3+} luminescence properties such as emission intensity, quantum yield and emission cross-section. The quantum yield showed a strong increase from mere 16% in Zinc–Borate glass to almost 73% in 60 mol% Bi{sub 2}O{sub 3} containing glass. Similarly, the emission cross-section for Nd{sup 3+4}F{sub 3/2}→{sup 4}I{sub 11/2} laser transition raised from 2.43×10{sup −20} cm{sup 2} to 3.95×10{sup −20} cm{sup 2} in studied concentration suggesting a strong improvement in Nd{sup 3+} laser spectroscopic properties in Zinc–Boro-Bismuthate glass. These materials may be promising for compact solid state infrared lasers. - Highlights: • Continuous structural changes associated with reduction in host phonon energy by Bi{sub 2}O{sub 3} inclusion. • Ultrasonic velocity study revealed reduced Debye
2. Phase transition of solid bismuth under high pressure
International Nuclear Information System (INIS)
Chen Hai-Yan; Xiang Shi-Kai; Yan Xiao-Zhen; Zhang Yi; Liu Sheng-Gang; Bi Yan; Zheng Li-Rong
2016-01-01
As a widely used pressure calibrator, the structural phase transitions of bismuth from phase I, to phase II, to phase III, and then to phase V with increasing pressure at 300 K have been widely confirmed. However, there are different structural versions for phase III, most of which are determined by x-ray diffraction (XRD) technology. Using x-ray absorption fine structure (XAFS) measurements combined with ab initio calculations, we show that the proposed incommensurate composite structure of bismuth of the three configurations is the best option. An abnormal continuous increase of the nearest-neighbor distance of phase III with elevated pressure is also observed. The electronic structure transformation from semimetal to metal is responsible for the complex behavior of structure transformation. (paper)
3. Ac irreversibility line of bismuth-based high temperature superconductors
Energy Technology Data Exchange (ETDEWEB)
Mehdaoui, A. [Laboratoire de Physique et de Spectroscopie Electronique, URA 1435 Faculte des Sciences, Universite de Haute Alsace 4, rue des Freres Lumiere, 68093 Mulhouse Cedex (France); Beille, J. [Laboratoire Louis Neel, CNRS, BP 166, 38042 Grenoble Cedex 9 (France); Berling, D.; Loegel, B. [Laboratoire de Physique et de Spectroscopie Electronique, URA 1435 Faculte des Sciences, Universite de Haute Alsace 4, rue des Freres Lumiere, 68093 Mulhouse Cedex (France); Noudem, J.G.; Tournier, R. [EPM-MATFORMAG, Laboratoire dElaboration par Procede Magnetique, CNRS, BP 166, 38042 Grenoble Cedex 9 (France)
1997-09-01
We discuss the magnetic properties of lead doped Bi-2223 bulk samples obtained through combined magnetic melt texturing and hot pressing (MMTHP). The ac complex susceptibility measurements are achieved over a broad ac field range (1 Oe{lt}h{sub ac}{lt}100 Oe) and show highly anisotropic properties. The intergranular coupling is improved in the direction perpendicular to the applied stress and magnetic field direction, and an intragranular loss peak is observed for the first time. A comparison is made with other bismuth-based compounds and it is shown that the MMTHP process shifts the ac irreversibility line (ac IL) toward higher fields. It is also shown that all the ac IL{close_quote}s for quasi 2D bismuth-based compounds show a nearly quadratic temperature dependence and deviate therefore strongly from the linear behavior observed in quasi 3D compounds and expected from a critical state model.{copyright} {ital 1997 Materials Research Society.}
4. Ac irreversibility line of bismuth-based high temperature superconductors
International Nuclear Information System (INIS)
Mehdaoui, A.; Beille, J.; Berling, D.; Loegel, B.; Noudem, J.G.; Tournier, R.
1997-01-01
We discuss the magnetic properties of lead doped Bi-2223 bulk samples obtained through combined magnetic melt texturing and hot pressing (MMTHP). The ac complex susceptibility measurements are achieved over a broad ac field range (1 Oe ac <100 Oe) and show highly anisotropic properties. The intergranular coupling is improved in the direction perpendicular to the applied stress and magnetic field direction, and an intragranular loss peak is observed for the first time. A comparison is made with other bismuth-based compounds and it is shown that the MMTHP process shifts the ac irreversibility line (ac IL) toward higher fields. It is also shown that all the ac IL close-quote s for quasi 2D bismuth-based compounds show a nearly quadratic temperature dependence and deviate therefore strongly from the linear behavior observed in quasi 3D compounds and expected from a critical state model.copyright 1997 Materials Research Society
5. Quantum nernst effect in a bismuth single crystal
International Nuclear Information System (INIS)
Matsuo, M.; Endo, A.; Hatano, N.; Nakamura, H.; Shirasaki, R.; Sugihara, K.
2009-07-01
We calculate the phonon-drag contribution to the transverse (Nernst) thermoelectric power S yx in a bismuth single crystal subjected to a quantizing magnetic field. The calculated heights of the Nernst peaks originating from the hole Landau levels and their temperature dependence reproduce the right order of magnitude for those of the pronounced magneto-oscillations recently reported by Behnia et al. A striking experimental finding that S yx is much larger than the longitudinal (Seebeck) thermoelectric power S xx can be naturally explained as the effect of the phonon drag, combined with the well-known relation between the longitudinal and the Hall resistivity ρ xx >> |ρ yx | in a semi-metal bismuth. The calculation that includes the contribution of both holes and electrons suggests that some of the hitherto unexplained minor peaks located roughly at the fractional filling of the hole Landau levels are attributable to the electron Landau levels. (author)
6. Nanophotonic Modulator with Bismuth Ferrite as Low-loss Switchable Material
DEFF Research Database (Denmark)
Babicheva, Viktoriia; Zhukovsky, Sergei; Lavrinenko, Andrei
2015-01-01
We propose a nanophotonic waveguide modulator with bismuth ferrite as a tunable material. Due to near-zero losses in bismuth ferrite, modulation with up to 20 dB/μm extinction ratio and 12 μm propagation length is achieved.......We propose a nanophotonic waveguide modulator with bismuth ferrite as a tunable material. Due to near-zero losses in bismuth ferrite, modulation with up to 20 dB/μm extinction ratio and 12 μm propagation length is achieved....
7. Dose reduction using Bismuth protectors in chest computed tomography
International Nuclear Information System (INIS)
Anaya, R.
2012-01-01
This monography is about the Dose reduction using Bismuth protectors in chest CT. The radiation protection of specific areas is necessary when the tissues or radiosensitive organs are near the path of light beam. The correct use of protection represents a challenge for the radiologist because of the time and materials required. The method used was a prospective investigatio in CHPR (TC service) and the doses was measured with TLD dosimeters. It is important to use these protectors in children hospitals.
8. Oxide layer stability in lead-bismuth at high temperature
Science.gov (United States)
Martín, F. J.; Soler, L.; Hernández, F.; Gómez-Briceño, D.
2004-11-01
Materials protection by 'in situ' oxidation has been studied in stagnant lead-bismuth, with different oxygen levels (H 2/H 2O ratios of 0.3 and 0.03), at temperatures from 535 °C to 600 °C and times from 100 to 3000 h. The materials tested were the martensitic steels F82Hmod, EM10 and T91 and the austenitic stainless steels, AISI 316L and AISI 304L. The results obtained point to the existence of an apparent threshold temperature above which corrosion occurs and the formation of a protective and stable oxide layer is not possible. This threshold temperature depends on material composition, oxygen concentration in the liquid lead-bismuth and time. The threshold temperature is higher for the austenitic steels, especially for the AISI 304L, and it increases with the oxygen concentration in the lead-bismuth. The oxide layer formed disappear with time and, after 3000 h all the materials, except AISI 304L, suffer corrosion, more severe for the martensitic steels and at the highest temperature tested.
9. Theoretical study of bismuth-doped cadmium telluride
Science.gov (United States)
Menendez-Proupin, E.; Rios-Gonzalez, J. A.; Pena, J. L.
Cadmium telluride heavily doped with bismuth has been proposed as an absorber with an intermediate band for solar cells. Increase in the photocurrent has been shown recently, although the overall cell efficiency has not improved. In this work, we study the electronic structure and the formation energies of the defects associated to bismuth impurities. We have performed electronic structure calculations within generalized density functional theory, using the exchange-correlation functional HSE(w) , where the range-separation parameter w has been tuned to reproduce the CdTe bandgap. Improving upon previous reports, we have included the spin-orbit interaction, which modifies the structure of the valence band and the energy levels of bismuth. We have found that interstitial Bi (Bii) tends to occupy Cd vacancies, cadmium substitution (BiCd) creates single donor level, while tellurium substitution (BiTe) is a shallow single acceptor. We investigate the interaction between these point defects and how can they be combined to create a partially filled intermediate band. Supported by FONDECYT Grant 1130437, CONACYT-SENER SUSTENTABILIDAD ENERGETICA/project CeMIE-Sol PY-207450/25 and PY-207450/26. JARG acknowledges CONACYT fellowship for research visit. Powered@NLHPC (ECM-02).
10. Study of barium bismuth titanate prepared by mechanochemical synthesis
Directory of Open Access Journals (Sweden)
Lazarević Z.Ž.
2009-01-01
Full Text Available Barium-bismuth titanate, BaBi4Ti4O15 (BBT, a member of Aurivillius bismuth-based layer-structure perovskites, was prepared from stoichiometric amounts of barium titanate and bismuth titanate obtained via mechanochemical synthesis. Mechanochemical synthesis was performed in air atmosphere in a planetary ball mill. The reaction mechanism of BaBi4Ti4O15 and the preparation and characteristics of BBT ceramic powders were studied using XRD, Raman spectroscopy, particle analysis and SEM. The Bi-layered perovskite structure of BaBi4Ti4O15 ceramic forms at 1100 °C for 4 h without a pre-calcination step. The microstructure of BaBi4Ti4O15 exhibits plate-like grains typical for the Bi-layered structured material and spherical and polygonal grains. The Ba2+ addition leads to changes in the microstructure development, particularly in the change of the average grain size.
11. Aerosol deposition of (Cu,Ti) substituted bismuth vanadate films
Energy Technology Data Exchange (ETDEWEB)
Exner, Jörg, E-mail: [email protected] [University of Bayreuth, Department of Functional Materials, Universitätsstraße 30, 95440 Bayreuth (Germany); Fuierer, Paul [Materials and Metallurgical Engineering Department, New Mexico Institute of Mining and Technology, Socorro, NM 87801 (United States); Moos, Ralf [University of Bayreuth, Department of Functional Materials, Universitätsstraße 30, 95440 Bayreuth (Germany)
2014-12-31
Bismuth vanadate, Bi{sub 4}V{sub 2}O{sub 11}, and related compounds with various metal (Me) substitutions, Bi{sub 4}(Me{sub x}V{sub 1−x}){sub 2}O{sub 11−δ}, show some of the highest ionic conductivities among the known solid oxide electrolytes. Films of Cu and Ti substituted bismuth vanadate were prepared by an aerosol deposition method, a spray coating process also described as room temperature impact consolidation. Resultant films, several microns in thickness, were dense with good adhesion to the substrate. Scanning electron microscopy and high temperature X-ray diffraction were used to monitor the effects of temperature on the structure and microstructure of the film. The particle size remained nano-scale while microstrain decreased rapidly up to 500 °C, above which coarsening and texturing increased rapidly. Impedance measurements of films deposited on inter-digital electrodes revealed an annealing effect on the ionic conductivity, with the conductivity exceeding that of a screen printed film, and approaching that of bulk ceramic. - Highlights: • Cu and Ti doped bismuth vanadate films were prepared by aerosol deposition (AD). • Dense 3–5 μm thick films were deposited on alumina, silicon and gold electrodes. • Annealing of the AD-layer increases the conductivity by 1.5 orders of magnitude. • Effect of temperature on structure and microstructure was investigated.
12. Soluble Lead and Bismuth Chalcogenidometallates: Versatile Solders for Thermoelectric Materials
Energy Technology Data Exchange (ETDEWEB)
Zhang, Hao [Department; Son, Jae Sung [Department; School; Dolzhnikov, Dmitriy S. [Department; Filatov, Alexander S. [Department; Hazarika, Abhijit [Department; Wang, Yuanyuan [Department; Hudson, Margaret H. [Department; Sun, Cheng-Jun [Advanced; Chattopadhyay, Soma [Physical; Talapin, Dmitri V. [Department; Center
2017-07-27
Here we report the syntheses of largely unexplored lead and bismuth chalcogenidometallates in the solution phase. Using N2H4 as the solvent, new compounds such as K6Pb3Te6·7N2H4 were obtained. These soluble molecular compounds underwent cation exchange processes using resin chemistry, replacing Na+ or K+ by decomposable N2H5+ or tetraethylammonium cations. They also transformed into stoichiometric lead and bismuth chalcogenide nanomaterials with the addition of metal salts. Such a versatile chemistry led to a variety of composition-matched solders to join lead and bismuth chalcogenides and tune their charge transport properties at the grain boundaries. Solution-processed thin films composed of Bi0.5Sb1.5Te3 microparticles soldered by (N2H5)6Bi0.5Sb1.5Te6 exhibited thermoelectric power factors (~28 μW/cm K2) comparable to those in vacuum-deposited Bi0.5Sb1.5Te3 films. The soldering effect can also be integrated with attractive fabrication techniques for thermoelectric modules, such as screen printing, suggesting the potential of these solders in the rational design of printable and moldable thermoelectrics.
13. Shape-controlled solvothermal synthesis of bismuth subcarbonate nanomaterials
International Nuclear Information System (INIS)
Cheng Gang; Yang Hanmin; Rong Kaifeng; Lu Zhong; Yu Xianglin; Chen Rong
2010-01-01
Much effort has been devoted to the synthesis of novel nanostructured materials because of their unique properties and potential applications. Bismuth subcarbonate ((BiO) 2 CO 3 ) is one of commonly used antibacterial agents against Helicobacter pylori (H. pylori). Different (BiO) 2 CO 3 nanostructures such as cube-like nanoparticles, nanobars and nanoplates, were fabricated from bismuth nitrate via a simple solvothermal method. The nanostructures were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that the solvents and precursors have an influence on the morphologies of (BiO) 2 CO 3 nanostructures. The possible formation mechanism of different (BiO) 2 CO 3 nanostructures fabricated under different conditions was also discussed. - Graphical abstract: Different bismuth subcarbonate ((BiO) 2 CO 3 ) nanostructures were successfully synthesized by a simple solvothermal method. It was found that the solvents and precursors have an influence on the morphologies of (BiO) 2 CO 3 nanostructures.
14. Bismuth Oxysulfide and Its Polymer Nanocomposites for Efficient Purification
Directory of Open Access Journals (Sweden)
Yidong Luo
2018-03-01
Full Text Available The danger of toxic organic pollutants in both aquatic and air environments calls for high-efficiency purification material. Herein, layered bismuth copper oxychalcogenides, BiCuSO, nanosheets of high photocatalytic activity were introduced to the PVDF (Polyvinylidene Fluoride. The fibrous membranes provide an easy, efficient, and recyclable way to purify organic pollutant. The physical and photophysical properties of the BiCuSO and its polymer composite were characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD, ultraviolet-visible diffuse reflection spectroscopy (DRS, X-ray photoelectron spectroscopy (XPS, electron spin resonance (EPR. Photocatalysis of Congo Red reveals that the BiCuSO/PVDF shows a superior photocatalytic activity of a 55% degradation rate in 70 min at visible light. The high photocatalytic activity is attributed to the exposed active {101} facets and the triple vacant associates V B i ‴ V O • • V B i ‴ . By engineering the intrinsic defects on the surface of bismuth oxysulfide, high solar-driven photocatalytic activity can be approached. The successful fabrication of the bismuth oxysulfide and its polymer nanocomposites provides an easy and general approach for high-performance purification materials for various applications.
15. Thermodynamic modelling of phase equilibrium in system Ti-B-Si-C, synthesis and phases composition of borides and carbides layers on titanic alloyVT-1 at electron beam treatment in vacuum
Science.gov (United States)
Smirnyagina, N. N.; Khaltanova, V. M.; Lapina, A. E.; Dasheev, D. E.
2017-01-01
Composite layers on the basis of carbides and borides the titan and silicon on titanic alloy VT-1 are generated at diffused saturation in vacuum. Formation in a composite of MAX phase Ti3SiC2 is shown. Thermodynamic research of phase equilibrium in systems Ti-Si-C and Ti-B-C in the conditions of high vacuum is executed. The thermodynamics, formation mechanisms of superfirm layers borides and carbides of the titan and silicon are investigated.
16. Study on corrosion test techniques in lead bismuth eutectic flow. Joint research report in JFY2002
International Nuclear Information System (INIS)
Takahashi, Minoru; Sekimoto, Hiroshi
2003-03-01
17. Tunable field emission characteristics of ZnO nanowires coated with varied thickness of lanthanum boride thin films
International Nuclear Information System (INIS)
Zhao, C.X.; Li, Y.F.; Chen, Jun; Deng, S.Z.; Xu, N.S.
2013-01-01
Lanthanum boride (LaB x ) thin films with various thicknesses were deposited on ZnO nanowire arrays by electron beam evaporation. Field emission characteristics of ZnO nanowires show close dependence on LaB x coating thickness. The turn-on field increases with increasing LaB x coating thickness from 10 nm to 50 nm. The observed phenomena were explained by a model that the tunneling at ZnO/LaB x interface dominates the emission process. - Highlights: ► Coating thickness dependence of field emission characteristics of ZnO nanowires was observed from LaB x coated ZnO nanowires. ► More stable field emission was observed from ZnO nanowires with LaB x coating. ► A model was proposed that the tunneling at ZnO/LaB x interface dominates the emission process
18. The low-lying quartet electronic states of group 14 diatomic borides XB (X = C, Si, Ge, Sn, Pb)
Science.gov (United States)
Pontes, Marcelo A. P.; de Oliveira, Marcos H.; Fernandes, Gabriel F. S.; Da Motta Neto, Joaquim D.; Ferrão, Luiz F. A.; Machado, Francisco B. C.
2018-04-01
The present work focuses in the characterization of the low-lying quartet electronic and spin-orbit states of diatomic borides XB, in which X is an element of group 14 (C, Si, Ge, Sn, PB). The wavefunction was obtained at the CASSCF/MRCI level with a quintuple-ζ quality basis set. Scalar relativistic effects were also taken into account. A systematic and comparative analysis of the spectroscopic properties for the title molecular series was carried out, showing that the (1)4Π→X4Σ- transition band is expected to be measurable by emission spectroscopy to the GeB, SnB and PbB molecules, as already observed for the lighter CB and SiB species.
19. Synthesis, characterization and investigation of thermoelectric properties of selected metal borides; Synthese, Charakterisierung und Untersuchung thermoelektrischer Eigenschaften ausgewaehlter Metallboride
Energy Technology Data Exchange (ETDEWEB)
Stober, Frederick
2012-06-04
The present work deals with the high-temperature thermoelectric properties of transition metal [eg V, Cr, Mn, Ni, Cu] and lanthanide [e.g. Sc, Y, Gd, Er, Dy]-borides. In particular, intercalation compounds of beta-rhombohedral boron, compounds of the type MB{sub 66}, dodecaborides and hexaborides were examined. In the case of intercalation compounds of beta-rhombohedral boron it was found that the incorporation of metals such as Sc, Mn or Cu result in favorable thermoelectric properties. The reason is most likely the preferred occupation of the metal position M2 instead of M4. Composites, for example, DyB{sub 66}-DyB{sub 12} show high electrical conductivities, high Seebeck effects at high temperatures due to the presence of DyB{sub 12} and low thermal conductivities as a result of the DyB{sub 66} matrix. At 1100K the composite DyB{sub 66}-DyB{sub 12} shows a ZT value of 0.55, thus exceeding the ZT of boron carbide (B{sub 13}C{sub 2}) at this temperature which is considered the best p-type boride material. A composite of ErB{sub 12}-ErB{sub 4}-ErB{sub 2} has negative Seebeck coefficients and shows a ZT value of 0.5 at 840K. Furthermore, the structure of tetragonal Scandiumdodecaboride ScB{sub 12} was solved on the basis of synchrotron data from a crystalline powder, after it has been debated for decades but never fully resolved.
20. Co3O4 nanoneedle@electroactive nickel boride membrane core/shell arrays: A novel hybrid for enhanced capacity
International Nuclear Information System (INIS)
Li, Tingting; Zhu, Congxu; Yang, Xiaogang; Gao, Yuanhao; He, Weiwei; Yue, Hongwei; Zhao, Hongxiao
2017-01-01
Graphical abstract: Active nickel boride membrane anchored Co 3 O 4 nanoneedle arrays hybrid is synthesized via rapid interface reaction. The optimized core/shell nanostructure demonstrates greatly enhanced electrochemical properties. Display Omitted -- Highlights: •Active nickel boride membrane anchored Co 3 O 4 nanoneedle arrays core-shell hybrid architectures was fabricated via rapid interface reaction. •Specific capacity was improved by synergy between highly active components and optimized electron transfer microstructure. •The assembled asymmetric supercapacitor device exhibited excellent electrochemical performance. -- Abstract: Exploring novel hybrid materials with efficient microstructure using facile approaches is highly urgent in designing supercapacitor electrodes. Here, the Ni-B membrane was used for coating the porous Co 3 O 4 nanoneedle arrays which supported on the nickel foam (NF) frameworks through a rapid chemical reduction process (denoted as NF/Co 3 O 4 @NiB). The Ni-B membrane both provided sufficient active sites for redox reactions and inhibited the aggregation of formed hybrid architectures. Benefiting from the unique structural design and strongly coupled effects between porous Co 3 O 4 arrays and Ni-B membrane, the resulted NF/Co 3 O 4 @NiB electrode exhibited high areal capacitance of 3.47 F cm −2 (0.48 mAh cm −2 ) at a current density of 2.5 mA cm −2 , an excellent rate capability while maintaining 95.5% capacity retention after 2000 cycles. The asymmetric supercapacitor constructed with the NF/Co 3 O 4 @NiB as positive electrode and hierarchical porous carbon (HPC) as negative electrode also showed ideal capacitive behavior, and simultaneously delivered high energy and power densities. The easily decoration of Ni-B membrane on various active nanoarrays may arouse more novel design about hybrid architectures for large-scale applications.
1. A single drug for Helicobacter pylori infection: first results with a new bismuth triple monocapsule
NARCIS (Netherlands)
de Boer, W. A.; van Etten, R. J.; Schneeberger, P. M.; Tytgat, G. N.
2000-01-01
In this pilot study we investigated the efficacy and tolerability of a new monocapsule that contains a bismuth compound, tetracycline, and metronidazole. If proven to be effective, this monotherapy would turn the well-accepted multidrug regimen of standard bismuth-based triple therapy into an easy
2. Method of Creating Micro-scale Silver Telluride Grains Covered with Bismuth Nanoparticles
Science.gov (United States)
Kim, Hyun-Jung (Inventor); Choi, Sang Hyouk (Inventor); King, Glen C. (Inventor); Park, Yeonjoon (Inventor); Lee, Kunik (Inventor)
2014-01-01
Provided is a method of enhancing thermoelectric performance by surrounding crystalline semiconductors with nanoparticles by contacting a bismuth telluride material with a silver salt under a substantially inert atmosphere and a temperature approximately near the silver salt decomposition temperature; and recovering a metallic bismuth decorated material comprising silver telluride crystal grains.
3. Build-up enhancement of photoluminescence from phenylazomethine bismuth dendrimer using Bi(OTf)3
Science.gov (United States)
Kambe, Tetsuya; Imaoka, Shotaro; Imaoka, Takane; Yamamoto, Kimihisa
2018-05-01
Metal assembly to a dendrimer can provide various functionalities based on the branched structure. Here, we researched assembly phenomena of bismuth salts in the phenylazomethine dendrimer and achieved enhancement of emission intensity per metal unit by using Bi(OTf)3. This enhancement suggested increasing of Bi-N coordination bonds derived from the bismuth units in the dendrimer.
4. Selective oxidation of propylene to acrolein by silica-supported bismuth molybdate catalysts
DEFF Research Database (Denmark)
Duc, Duc Truong; Ha, Hanh Nguyen; Fehrmann, Rasmus
2011-01-01
Silica-supported bismuth molybdate catalysts have been prepared by impregnation, structurally characterized and examined as improved catalysts for the selective oxidation of propylene to acrolein. Catalysts with a wide range of loadings (from 10 to 90 wt%) of beta bismuth molybdate (β-Bi2Mo2O9) w...
5. Localization and Related Phenomena in Multiply Connected Nanostructured Inverse Opal Bismuth
Science.gov (United States)
Bleiweiss, Michael; Saygi, Salih; Amirzadeh, Jafar; Datta, Timir; Lungu, Anca; Yin, Ming; Palm, Eric; Brandt, Bruce; Iqbal, Zafar
2001-03-01
The nanostructures were fabricated by pressure infiltration of bismuth into porous artificial opal and were characterized using SEM, EDX and XRD. These structures form a regular three-dimensional network in which the bismuth regions percolate in all directions between the close packed spheres of SiO_2. The sizes of the conducting regions are of the order of tens of nanometers. The static magnetic properties of both bismuth inverse opal and bulk bismuth were studied using a SQUID magnetometer. Transport measurements, including Hall, were done using standard ac four and six probe techniques in fields up to 17 T* and temperatures between 4.2 and 150 K. The results of these measurements, including the observation of localization phenomena, will be discussed. Comparisons will be made with published results on bismuth nanowires. *Performed at the National High Magnetic Field Lab (NHMFL) FSU, Tallahassee, FL. Partially supported by a grant from NASA.
6. Thermodynamics Calculation and Experimental Study on Separation of Bismuth from a Bismuth Glance Concentrate Through a Low-Temperature Molten Salt Smelting Process
Science.gov (United States)
Yang, Jian-Guang; He, De-Wen; Tang, Chao-Bo; Chen, Yong-Ming; Sun, Ya-Hui; Tang, Mo-Tang
2011-08-01
The main purpose of this study is to characterize and separate bismuth from a bismuth glance concentrate through a low-temperature, sulfur-fixing smelting process. This article reports on a study conducted on the optimization of process parameters, such as Na2CO3 and zinc oxide wt pct in charging, smelting temperature, smelting duration on the bismuth yield, resultant crude bismuth grade, and sulfur-fixing rate. A maximum bismuth recovery of 97.31 pct, crude bismuth grade of 96.93 pct, and 98.23 pct sulfur-fixing rate are obtained when a charge (containing 63.50 wt pct of Na2CO3 and 22.50 wt pct of bismuth glance, as well as 5 pct in excess of the stoichiometric requirement of zinc oxide dosage) is smelted at 1000 K (727 °C) for 150 minutes. This smelting operation is free from atmospheric pollution because zinc oxide is used as the sulfur-fixing agent, which can capture sulfur from bismuth sulfide and form the more thermodynamic-stable compound, zinc sulfide. The solid residue is subjected to a mineral dressing operation to obtain suspension, which is filtered to produce a cake, representing the solid particles of zinc sulfide. Based on the results of the chemical content analysis of the as-resultant zinc sulfide, more than 93 pct zinc sulfide can be recovered, and the recovered zinc sulfide grade can reach 60.20 pct. This material can be sold as zinc sulfide concentrate or roasted to be regenerated as zinc oxide.
7. Bioavailability and chronic toxicity of bismuth citrate to earthworm Eisenia andrei exposed to natural sandy soil.
Science.gov (United States)
Omouri, Zohra; Hawari, Jalal; Fournier, Michel; Robidoux, Pierre Yves
2018-01-01
The present study describes bioavailability and chronic effects of bismuth to earthworms Eisenia andrei using OECD reproduction test. Adult earthworms were exposed to natural sandy soil contaminated artificially by bismuth citrate. Average total concentrations of bismuth in soil recovered by HNO 3 digestion ranged from 75 to 289mg/kg. Results indicate that bismuth decreased significantly all reproduction parameters of Eisenia andrei at concentrations ≥ 116mg/kg. However, number of hatched cocoons and number of juveniles seem to be more sensitive than total number of cocoons, as determined by IC 50 ; i.e., 182, 123 and > 289mg/kg, respectively. Bismuth did not affect Eisenia andrei growth and survival, and had little effect on phagocytic efficiency of coelomocytes. The low immunotoxicity effect might be explained by the involvement of other mechanisms i.e. bismuth sequestered by metal-binding compounds. After 28 days of exposure bismuth concentrations in earthworms tissue increased with increasing bismuth concentrations in soil reaching a stationary state of 21.37mg/kg dry tissue for 243mg Bi/kg dry soil total content. Data indicate also that after 56 days of incubation the average fractions of bismuth available extracted by KNO 3 aqueous solution in soil without earthworms varied from 0.0051 to 0.0229mg/kg, while in soil with earthworms bismuth concentration ranged between 0.310-1.347mg/kg dry soil. We presume that mucus and chelating agents produced by earthworms and by soil or/and earthworm gut microorganisms could explain this enhancement, as well as the role of dermal and ingestion routes of earthworms uptake to soil contaminant. Copyright © 2017 Elsevier Inc. All rights reserved.
8. Bismuth oxide nanotubes-graphene fiber-based flexible supercapacitors
Science.gov (United States)
Gopalsamy, Karthikeyan; Xu, Zhen; Zheng, Bingna; Huang, Tieqi; Kou, Liang; Zhao, Xiaoli; Gao, Chao
2014-07-01
Graphene-bismuth oxide nanotube fiber as electrode material for constituting flexible supercapacitors using a PVA/H3PO4 gel electrolyte is reported with a high specific capacitance (Ca) of 69.3 mF cm-2 (for a single electrode) and 17.3 mF cm-2 (for the whole device) at 0.1 mA cm-2, respectively. Our approach opens the door to metal oxide-graphene hybrid fibers and high-performance flexible electronics.Graphene-bismuth oxide nanotube fiber as electrode material for constituting flexible supercapacitors using a PVA/H3PO4 gel electrolyte is reported with a high specific capacitance (Ca) of 69.3 mF cm-2 (for a single electrode) and 17.3 mF cm-2 (for the whole device) at 0.1 mA cm-2, respectively. Our approach opens the door to metal oxide-graphene hybrid fibers and high-performance flexible electronics. Electronic supplementary information (ESI) available: Equations and characterization. SEM images of GGO, XRD and XPS of Bi2O3 NTs, HRTEM images and EDX Spectra of Bi2O3 NT5-GF, CV curves of Bi2O3NT5-GF, Bi2O3 NTs and bismuth nitrate in three-electrode system (vs. Ag/AgCl). CV and GCD curves of Bi2O3 NT1-GF and Bi2O3 NT3-GF. See DOI: 10.1039/c4nr02615b
9. Conduction mechanism in bismuth silicate glasses containing titanium
International Nuclear Information System (INIS)
Dult, Meenakshi; Kundu, R.S.; Murugavel, S.; Punia, R.; Kishore, N.
2014-01-01
Bismuth silicate glasses mixed with different concentrations of titanium dioxide having compositions xTiO 2 –(60−x)Bi 2 O 3 –40SiO 2 with x=0, 5, 10, 15 and 20 were prepared by the normal melt quench technique. The frequency dependence of the ac electrical conductivity of different compositions of titanium bismuth silicate glasses has been studied in the frequency range 10 −1 Hz to 10 MHz and in the temperature range 623–703 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the compositions of titanium bismuth silicate glass system. The dc conductivity (σ dc ), so called crossover frequency (ω H ), and frequency exponent (s) have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating center (H f ) and enthalpy of migration (H m ) have also been estimated. The conductivity data have been analyzed in terms of different theoretical models to determine the possible conduction mechanism. Analysis of the conductivity data and the frequency exponent shows that the correlated barrier hopping of electrons between Ti 3+ and Ti 4+ ions in the glasses is the most favorable mechanism for ac conduction. The temperature dependent dc conductivity has been analyzed in the framework of theoretical variable range hopping model (VRH) proposed by Mott which describe the hopping conduction in disordered semiconducting systems. The various polaron hopping parameters have also been deduced. Mott's VRH model is found to be in good agreement with experimental data and the values of inverse localization length of s-like wave function (α) obtained by this model with modifications suggested by Punia et al. are close to the ones reported for a number of oxide glasses
10. Yttrium bismuth titanate pyrochlore mixed oxides for photocatalytic hydrogen production
Energy Technology Data Exchange (ETDEWEB)
Merka, Oliver
2012-10-18
In this work, the sol-gel synthesis of new non-stoichiometric pyrochlore titanates and their application in photocatalytic hydrogen production is reported. Visible light response is achieved by introducing bismuth on the A site or by doping the B site by transition metal cations featuring partially filled d orbitals. This work clearly focusses on atomic scale structural changes induced by the systematical introduction of non-stoichiometry in pyrochlore mixed oxides and the resulting influence on the activity in photocatalytic hydrogen production. The materials were characterized in detail regarding their optical properties and their atomic structure. The pyrochlore structure tolerates tremendous stoichiometry variations. The non-stoichiometry in A{sub 2}O{sub 3} rich compositions is compensated by distortions in the cationic sub-lattice for the smaller Y{sup 3+} cation and by evolution of a secondary phase for the larger Bi{sup 3+} cation on the A site. For TiO{sub 2} rich compositions, the non-stoichiometry leads to a special vacancy formation in the A and optionally O' sites. It is shown that pyrochlore mixed oxides in the yttrium bismuth titanate system represent very active and promising materials for photocatalytic hydrogen production, if precisely and carefully tuned. Whereas Y{sub 2}Ti{sub 2}O{sub 7} yields stable hydrogen production rates over time, the bismuth richer compounds of YBiTi{sub 2}O{sub 7} and Bi{sub 2}Ti{sub 2}O{sub 7} are found to be not stable under irradiation. This drawback is overcome by applying a special co-catalyst system consisting of a precious metal core and a Cr{sub 2}O{sub 3} shell on the photocatalysts.
11. Solution combustion synthesis and characterization of nanosized bismuth ferrite
Science.gov (United States)
Sai Kumar, V. Sesha; Rao, K. Venkateswara; Krishnaveni, T.; Kishore Goud, A. Shiva; Reddy, P. Ranjith
2012-06-01
The present paper describes a simple method of nanosized BiFeO3 by the solution combustion synthesis using bismuth and iron nitrates as oxidizers and the combination fuel of citric acid and ammonium hydroxide, with fuel to oxidizer ratio (Ψ = 1) one. The X-ray Diffraction results indicated rhombohedral phase (R3m) with JCPDS data card no: 72-2035. The ferroelectric transition of the sample at 8310C was detected by differential thermal analysis. Thermal analysis was done by Thermal gravimetric-Differential thermal analyzer and obtained results were presented in this paper.
12. Investigation of corrosion, water reaction, polonium evaporation and bismuth resource in liquid metal lead-bismuth technology
Energy Technology Data Exchange (ETDEWEB)
Takano, Hideki; Takizuka, Takakazu [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Kitano, Teruaki [Mitsui Shipbuilding and Engineering Co. Ltd., Tokyo (Japan)
2000-10-01
13. Bismuth Silver Oxysulfide for Photoconversion Applications: Structural and Optoelectronic Properties
KAUST Repository
Baqais, Amal Ali Abdulallh; Curutchet, Antton; Ziani, Ahmed; Ait Ahsaine, Hassan; Sautet, Philippe; Takanabe, Kazuhiro; Le Bahers, Tangui
2017-01-01
Single-phase bismuth silver oxysulfide, BiAgOS, was prepared by a hydrothermal method. Its structural, morphological and optoelectronic properties were investigated and compared with bismuth copper oxysulfide (BiCuOS). Rietveld refinement of the powder X-ray diffraction (XRD) measurements revealed that the BiAgOS and BiCuOS crystals have the same structure as ZrSiCuAs: the tetragonal space group P4/nmm. X-ray photoelectron spectroscopy (XPS) analyses confirmed that the BiAgOS has a high purity, in contrast with BiCuOS, which tends to have Cu vacancies. The Ag has a monovalent oxidation state, whereas Cu is present in the oxidation states of +1 and +2 in the BiCuOS system. Combined with experimental measurements, density functional theory calculations employing the range-separated hybrid HSE06 exchange-correlation functional with spin-orbit coupling quantitatively elucidated photophysical properties such as ab-sorption coefficients, effective masses and dielectric constants. BiCuOS and BiAgOS were found to have indirect bandgaps of 1.1 and 1.5 eV, respectively. Both possess high dielectric constants and low electron and hole effective masses. Therefore, these materials are expected to have high exciton dissociation capabilities and excellent carrier diffusion properties. This study reveals that BiAgOS is a promising candidate for photoconversion applications.
14. Synthesis and characterization of bismuth alkaline titanate powders
Energy Technology Data Exchange (ETDEWEB)
Torres-Huerta, A.M., E-mail: [email protected] [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Dominguez-Crespo, M.A. [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Hernandez-Perez, M.A. [ESIQIE, Metalurgia, Instituto Politecnico Nacional, Mexico, D. F (Mexico); Garcia-Zaleta, D.S. [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Brachetti-Sibaja, S.B. [CICATA-Altamira, Instituto Politecnico Nacional, Km. 14.5 Carretera Tampico Puerto Industrial Altamira, Altamira, Tamps. 89600 (Mexico); Instituto Tecnologico de Ciudad Madero, Av. 1o. de Mayo esq. Sor Juana Ines de la Cruz s/n Col. Los Mangos C.P.89440 Cd. Madero Tamaulipas (Mexico)
2011-06-15
In this work, samples of bismuth alkaline titanate, (K{sub 0.5}Na{sub 0.5}){sub (2-x/2)}Bi{sub (x/6)}TiO{sub 3}, (x = 0.05-0.75) have been prepared by conventional ceramic technique and molten salts. Metal oxides or carbonates powders were used as starting raw materials. The crystalline phase of the synthesized powders was identified by the X-ray diffraction (XRD) and particle morphology was characterized by scanning electron microscopy (SEM). Solid state reaction method was unsuccessful to obtain pellets. From XRD results, a rhombohedral structure was detected and the parameter lattice were estimated to be a = 5.5478 A and {alpha} = 59.48{sup o}. These parameters were used to refine the structure by Rietveld analysis. SEM results showed several morphologies. Apparently, bismuth is promoting the grain growth whose sizes vary from 30 nm to 180 nm It is expected that these materials can be utilized in practical applications as substitutes for lead zirconatetitanate (PZT)-based ceramics.
15. Angle Dependence of the Orbital Magnetoresistance in Bismuth
Directory of Open Access Journals (Sweden)
Aurélie Collaudin
2015-06-01
Full Text Available We present an extensive study of angle-dependent transverse magnetoresistance in bismuth, with a magnetic field perpendicular to the applied electric current and rotating in three distinct crystallographic planes. The observed angular oscillations are confronted with the expectations of semiclassic transport theory for a multivalley system with anisotropic mobility and the agreement allows us to quantify the components of the mobility tensor for both electrons and holes. A quadratic temperature dependence is resolved. As Hartman argued long ago, this indicates that inelastic resistivity in bismuth is dominated by carrier-carrier scattering. At low temperature and high magnetic field, the threefold symmetry of the lattice is suddenly lost. Specifically, a 2π/3 rotation of magnetic field around the trigonal axis modifies the amplitude of the magnetoresistance below a field-dependent temperature. By following the evolution of this anomaly as a function of temperature and magnetic field, we map the boundary in the (field, temperature plane separating two electronic states. In the less symmetric state, confined to low temperature and high magnetic field, the three Dirac valleys cease to be rotationally invariant. We discuss the possible origins of this spontaneous valley polarization, including a valley-nematic scenario.
16. Bismuth Silver Oxysulfide for Photoconversion Applications: Structural and Optoelectronic Properties
KAUST Repository
Baqais, Amal Ali Abdulallh
2017-09-18
Single-phase bismuth silver oxysulfide, BiAgOS, was prepared by a hydrothermal method. Its structural, morphological and optoelectronic properties were investigated and compared with bismuth copper oxysulfide (BiCuOS). Rietveld refinement of the powder X-ray diffraction (XRD) measurements revealed that the BiAgOS and BiCuOS crystals have the same structure as ZrSiCuAs: the tetragonal space group P4/nmm. X-ray photoelectron spectroscopy (XPS) analyses confirmed that the BiAgOS has a high purity, in contrast with BiCuOS, which tends to have Cu vacancies. The Ag has a monovalent oxidation state, whereas Cu is present in the oxidation states of +1 and +2 in the BiCuOS system. Combined with experimental measurements, density functional theory calculations employing the range-separated hybrid HSE06 exchange-correlation functional with spin-orbit coupling quantitatively elucidated photophysical properties such as ab-sorption coefficients, effective masses and dielectric constants. BiCuOS and BiAgOS were found to have indirect bandgaps of 1.1 and 1.5 eV, respectively. Both possess high dielectric constants and low electron and hole effective masses. Therefore, these materials are expected to have high exciton dissociation capabilities and excellent carrier diffusion properties. This study reveals that BiAgOS is a promising candidate for photoconversion applications.
17. Magneto-photoconductivity of three dimensional topological insulator bismuth telluride
Science.gov (United States)
Cao, Bingchen; Eginligil, Mustafa; Yu, Ting
2018-03-01
Magnetic field dependence of the photocurrent in a 3D topological insulator is studied. Among the 3D topological insulators bismuth telluride has unique hexagonal warping and spin texture which has been studied by photoemission, scanning tunnelling microscopy and transport. Here, we report on low temperature magneto-photoconductivity, up to 7 T, of two metallic bismuth telluride topological insulator samples with 68 and 110 nm thicknesses excited by 2.33 eV photon energy along the magnetic field perpendicular to the sample plane. At 4 K, both samples exhibit negative magneto-photoconductance below 4 T, which is as a result of weak-antilocalization of Dirac fermions similar to the previous observations in electrical transport. However the thinner sample shows positive magneto-photoconductance above 4 T. This can be attributed to the coupling of surface states. On the other hand, the thicker sample shows no positive magneto-photoconductance up to 7 T since there is only one surface state at play. By fitting the magneto-photoconductivity data of the thicker sample to the localization formula, we obtain weak antilocalization behaviour at 4, 10, and 20 K, as expected; however, weak localization behaviour at 30 K, which is a sign of surface states masked by bulk states. Also, from the temperature dependence of phase coherence length bulk carrier-carrier interaction is identified separately from the surface states. Therefore, it is possible to distinguish surface states by magneto-photoconductivity at low temperature, even in metallic samples.
18. Genotoxic effects of bismuth (III oxide nanoparticles by comet assay
Directory of Open Access Journals (Sweden)
Reecep Liman
2015-06-01
Full Text Available Bismuth oxide is one of the important transition metal oxides and it has been intensively studied due to their peculiar characteristics (semiconductor band gap, high refractive index, high dielectric permittivity, high oxygen conductivity, resistivity, photoconductivity and photoluminescence etc.. Therefore, it is used such as microelectronics, sensor technology, optical coatings, transparent ceramic glass manufacturing, nanoenergetic gas generator, biosensor for DNA hybridization, potential immobilizing platforms for glucose oxidase and polyphenol oxidase, fuel cells, a additive in paints, an astringent in a variety of medical creams and topical ointments, and for the determination of heavy metal ions in drinking water, mineral water and urine. In addition this, Bismuth (III oxide nanoparticles (BONPs are favorable for the biomolecules adsorption than regular sized particles because of their greater advantages and novel characteristics (much higher specific surface, greater surface free energy, and good electrochemical stability etc.. Genotoxic effects of BONPs were investigated on the root cells of Allium cepa by Comet assay. A. cepa roots were treated with the aqueous dispersions of BONPs at 5 different concentrations (12.5, 25, 50, 75, and 100 ppm for 4 h. A significant increase in DNA damage was also observed at all concentrations of BONPs except 12.5 ppm by Comet assay. The results were also analyzed statistically by using SPSS for Windows; Duncan’s multiple range test was performed. These result indicate that BONPs exhibit genotoxic activity in A. cepa root meristematic cells.
19. Magnetic anisotropies in ultrathin bismuth iron garnet films
International Nuclear Information System (INIS)
Popova, Elena; Franco Galeano, Andres Felipe; Deb, Marwan; Warot-Fonrose, Bénédicte; Kachkachi, Hamid; Gendron, François; Ott, Frédéric
2013-01-01
Ultrathin bismuth iron garnet Bi 3 Fe 5 O 12 films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi 3 Fe 5 O 12 films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi 3 Fe 5 O 12 films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi 3 Fe 5 O 12 were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed
20. Magnetic anisotropies in ultrathin bismuth iron garnet films
Energy Technology Data Exchange (ETDEWEB)
Popova, Elena, E-mail: [email protected] [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Franco Galeano, Andres Felipe [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Deb, Marwan [Groupe d' Etude de la Matière Condensée (GEMaC), CNRS/Université de Versailles-Saint-Quentin, 45 Avenue des Etats-Unis, 78035 Versailles (France); Warot-Fonrose, Bénédicte [Centre d' Elaboration de Matériaux et d' Etudes Structurales (CEMES), CNRS, 29 rue Jeanne Marvig, 31055 Toulouse (France); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS–Universidad de Zaragoza (Spain); Kachkachi, Hamid [Laboratoire PROcédés, Matériaux et Energie Solaire (PROMES), CNRS/Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan (France); Gendron, François [Institut des NanoSciences de Paris (INSP), CNRS/Université Pierre et Marie Curie-Paris 6, 4 place Jussieu, Boîte courrier 840, 75252 Paris Cedex 05 (France); Ott, Frédéric [Laboratoire Léon Brillouin (LLB), CNRS/CEA, Bâtiment 563, CEA Saclay, 91191 Gif sur Yvette Cedex (France); and others
2013-06-15
Ultrathin bismuth iron garnet Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on (001)-oriented gadolinium gallium garnet substrates. Film thickness varied from two to three dozens of unit cells. Bi{sub 3}Fe{sub 5}O{sub 12} films grow pseudomorphically on substrates up to a thickness of 20 nm, and then a lattice relaxation occurs. Magnetic properties of the films were studied as a function of bismuth iron garnet thickness. The magnetization and cubic anisotropy decrease with decreasing film thickness. The uniaxial magnetocrystalline anisotropy is constant for all film thicknesses. For two unit cell thick films, the easy magnetization axis changes from in-plane to perpendicular to the plane direction. Such a reorientation takes place as a result of the competition of constant uniaxial perpendicular anisotropy with weakening film magnetization. - Highlights: ► Ultrathin Bi{sub 3}Fe{sub 5}O{sub 12} films were grown epitaxially on structure-matching substrates. ► Magnetic properties of Bi{sub 3}Fe{sub 5}O{sub 12} were studied down to the thickness of 2.5 nm. ► Reorientation of easy magnetization axis as a function of film thickness was observed.
1. Superconductivity in Bismuth. A New Look at an Old Problem.
Science.gov (United States)
2016-01-01
To investigate the relationship between atomic topology, vibrational and electronic properties and superconductivity of bismuth, a 216-atom amorphous structure (a-Bi216) was computer-generated using our undermelt-quench approach. Its pair distribution function compares well with experiment. The calculated electronic and vibrational densities of states (eDOS and vDOS, respectively) show that the amorphous eDOS is about 4 times the crystalline at the Fermi energy, whereas for the vDOS the energy range of the amorphous is roughly the same as the crystalline but the shapes are quite different. A simple BCS estimate of the possible crystalline superconducting transition temperature gives an upper limit of 1.3 mK. The e-ph coupling is more preponderant in a-Bi than in crystalline bismuth (x-Bi) as indicated by the λ obtained via McMillan's formula, λc = 0.24 and experiment λa = 2.46. Therefore with respect to x-Bi, superconductivity in a-Bi is enhanced by the higher values of λ and of eDOS at the Fermi energy.
2. System design study of small lead-bismuth cooled reactor
International Nuclear Information System (INIS)
Chikazawa, Yoshitaka; Hori, Toru; Konomura, Mamoru
2003-07-01
In phase II of the feasibility study of JNC, we will make a concept of a dispersion power source reactor with various requirements, such as economical competitiveness and safety. In the study of a small lead-bismuth cooled reactor, a concept whose features are long life core, inherent safety, natural convection of cooling system and steam generators in the reactor vessel has been designed since 2000. The investigations which have been done in 2002 are shown as follows; Safety analysis of UTOP considering uncertainty of reactivity. Possibility of reduction of number of control rods. Estimation of construction cost. Transient analyses of UTOP have been done in considering uncertainty of reactivity in order to show the inherent safety in the probabilistic method. And the inherent safety in UTOP is realized under the condition of considering uncertainty. Transient analyses of UTOP with various numbers of control rods have been done and it is suggested that there is possibility of reduction of the number of control rods considering accident managements. The method of cost estimation is a little modified. The cost of reactor vessel is estimated from that of medium sized lead-bismuth cooled reactor and the estimation of a purity control system is by coolant volume flow rate. The construction cost is estimated 850,000yen/kWe. (author)
3. Electrodeposition of bismuth alloys by the controlled potential method
International Nuclear Information System (INIS)
Lopez Alvarez, F.A.
1993-01-01
We worked with the electrodeposition of three bismuth alloys, the composition of the first electrolyte was: 0.3 g/l. Bi; 20 g/l. Ni; and the conditions were pH = 5.2 - 5.6; T = 25 Centigrade degrees; current density 0.3 A / dm 2 - 6.6 A / dm 2 . Following alloy was between Bi - Pb, composition of the electrolyte was 3.18 g/l. Bi (metallic); 31.81 g/l. Pb (Pb(NO 3 ) 2 ) pH : 1; T = 20 Centigrade degrees; current density 10.20 A/dm 2 . The third electrolyte was Bi-Cu, its composition was: 20.89 g/l. Bi; (metallic) 63.54 g/l Cu (Cu(NO 3 ) 2 ) pH : 1.5 - 1.8; T = 25-30 Centigrade degrees; current density 1-2 A/dm 2 . The best results were obtained with the third electrolyte. The purpose of this work was to experiment with different parameters like temperature, pH and the electrolyte concentration to obtain a bismuth alloy. (Author)
4. Helicobacter pylori second-line rescue therapy with levofloxacin- and bismuth-containing quadruple therapy, after failure of standard triple or non-bismuth quadruple treatments.
Science.gov (United States)
Gisbert, J P; Romano, M; Gravina, A G; Solís-Muñoz, P; Bermejo, F; Molina-Infante, J; Castro-Fernández, M; Ortuño, J; Lucendo, A J; Herranz, M; Modolell, I; Del Castillo, F; Gómez, J; Barrio, J; Velayos, B; Gómez, B; Domínguez, J L; Miranda, A; Martorano, M; Algaba, A; Pabón, M; Angueira, T; Fernández-Salazar, L; Federico, A; Marín, A C; McNicholl, A G
2015-04-01
5. Complexometric consequent titration of bismuth-titanium mixtures in the μg-region
International Nuclear Information System (INIS)
Schaefer, H.
1975-01-01
A quantitative method is described for the determination of microquantities of bismuth and titanium. Both metals are determined complexometrically with EDTA and potentiometric equivalence point indication using a Cu-ion sensitive electrode in a consequent titration. The analysis is conducted as back-titration with standard Cu-solution. The relative error of the determination is 0.8% for bismuth (50-100 μg) and for titanium (10-30 μg) at 1.0%. Under the chosen conditions, it is possible to determine as little as 15 μg bismuth and 5 μg titanium by means of this procedure. (author)
6. Specificities of reactor coolant pumps units with lead and lead-bismuth coolant
International Nuclear Information System (INIS)
Beznosov, A.V.; Anotonenkov, M.A.; Bokov, P.A.; Baranova, V.S.; Kustov, M.S.
2009-01-01
The analysis results of impact of lead and lead-bismuth coolants specific properties on the coolants flow features in flow channels of the main and auxiliary circulating pumps are presented. Impossibility of cavitation initiation in flow channels of vane pumps pumping lead and lead-bismuth coolants was demonstrated. The experimental research results of discontinuity of heavy liquid metal coolant column were presented and conditions of gas cavitation initiation in coolant flow were discussed. Invalidity of traditional calculation methods of water and sodium coolants circulation pumps calculations for lead and lead-bismuth coolants circulation pumps was substantiated [ru
7. Topological Insulator State in Thin Bismuth Films Subjected to Plane Tensile Strain
Science.gov (United States)
Demidov, E. V.; Grabov, V. M.; Komarov, V. A.; Kablukova, N. S.; Krushel'nitskii, A. N.
2018-03-01
The results of experimental examination of galvanomagnetic properties of thin bismuth films subjected to plane tensile strain resulting from the difference in thermal expansion coefficients of the substrate material and bismuth are presented. The resistivity, the magnetoresistance, and the Hall coefficient were studied at temperatures ranging from 5 to 300 K in magnetic fields as strong as 0.65 T. Carrier densities were calculated. A considerable increase in carrier density in films thinner than 30 nm was observed. This suggests that surface states are more prominent in thin bismuth films on mica substrates, while the films themselves may exhibit the properties of a topological insulator.
8. Chemical structure of bismuth compounds determines their gastric ulcer healing efficacy and anti-Helicobacter pylori activity.
Science.gov (United States)
Sandha, G S; LeBlanc, R; Van Zanten, S J; Sitland, T D; Agocs, L; Burford, N; Best, L; Mahoney, D; Hoffman, P; Leddin, D J
1998-12-01
The recognition of the role of Helicobacter pylori in the pathogenesis of peptic ulcer disease has led to renewed interest in bismuth pharmacology since bismuth compounds have both anti-Helicobacter pylori and ulcer healing properties. The precise chemical structure of current bismuth compounds is not known. This has hindered the development of new and potentially more efficacious formulations. We have created two new compounds, 2-chloro-1,3-dithia-2-bismolane (CDTB) and 1,2-[bis(1,3-dithia-2-bismolane)thio]ethane (BTBT), with known structure. In a rat model of gastric ulceration, BTBT was comparable to, and CDTB was significantly less effective than colloidal bismuth subcitrate in healing cryoprobe-induced ulcers. However, both BTBT and CDTB inhibited H. pylori growth in vitro at concentrations <1/10 that of colloidal bismuth subcitrate. The effects on ulcer healing are not mediated by suppression of acid secretion, pepsin inhibition, or prostaglandin production. Since all treated animals received the same amount of elemental bismuth, it appears that the efficacy of bismuth compounds varies with compound structure and is not simply dependent on the delivery of bismuth ion. Because the structure of the novel compounds is known, our understanding of the relationship of bismuth compound structure and to biologic activity will increase. In the future it may be possible to design other novel bismuth compounds with more potent anti-H. pylori and ulcer healing effects.
9. Theoretical Investigation of Bismuth-Based Semiconductors for Photocatalytic Applications
KAUST Repository
2017-11-01
Converting solar energy to clean fuel has gained remarkable attention as an emerged renewable energy resource but optimum efficiency in photocatalytic applications has not yet been reached. One of the dominant factors is designing efficient photocatalytic semiconductors. The research reveals a theoretical investigation of optoelectronic properties of bismuth-based metal oxide and oxysulfide semiconductors using highly accurate first-principles quantum method based on density functional theory along with the range-separated hybrid HSE06 exchange-correlation functional. First, bismuth titanate compounds including Bi12TiO20, Bi4Ti3O12, and Bi2Ti2O7 were studied in a combined experimental and theoretical approach to prove its photocatalytic activity under UV light. They have unique bismuth layered structure, tunable electronic properties, high dielectric constant and low electron and effective masses in one crystallographic direction allowing for good charge separation and carrier diffusion properties. The accuracy of the investigation was determined by the good agreement between experimental and theoretical values. Next, BiVO4 with the highest efficiency for oxygen evolution was investigated. A discrepancy between the experimental and theoretical bandgap was reported and inspired a systematic study of all intrinsic defects of the material and the corresponding effect on the optical and transport properties. A candidate defective structure was proposed for an efficient photocatalytic performance. To overcome the carrier transport limitation, a mild hydrogen treatment was also introduced. Carrier lifetime was enhanced due to a significant reduction of trap-assisted recombination, either via passivation of deep trap states or reduction of trap state density. Finally, an accurate theoretical approach to design a new family of semiconductors with enhanced optoelectronic properties for water splitting was proposed. We simulated the solid solutions Bi1−xRExCuOS (RE = Y, La
10. Status and future application of pilot lead-bismuth target circuit TC-1 for ADS
Energy Technology Data Exchange (ETDEWEB)
Ignatiev, S.; Leonchuk, M.; Orlov, Y.; Pankratov, D.; Reshetnikova, O.; Suvorov, G.; Zabudko, A. [Institute for Physics and Power Engineering, Obninsk (Russian Federation); Stepanov, V.; Klimov, N. [Experimental and Design Organization, Gidropress, Podolsk (Russian Federation); Hechanova, A.; Ma, J. [Nevada Univ., Las Vegas, NV (United States); Li, N. [Los Alamos National Lab., NM (United States); Gudowski, W. [International Science and Technology Center, Moscow (Russian Federation)
2007-07-01
A complicated evolution, status and future application of the pilot molten lead-bismuth target circuit of 1 MW proton beam power (TC-1) as an important part of a target-blanket accelerator driven system (ADS), that has been developed, created and twice tested under the auspice of the International Science and Technology Center (ISTC), is analyzed. The target complex TC-1 is a circulation lead-bismuth loop whose beam window is made of ferritic steel EP-823 (this steel was used in the past as material of fuel rods cladding in reactors cooled with lead-bismuth). At present TC-1 is operating at coolant temperature up to 300 C degrees and will be used to study different issues linked to the use of lead-bismuth: -) interaction with air, water and hydrogen, -) different regimes of flow, -) corrosion, -) filtering, or -) slag formation.
11. Shielding property of bismuth glass based on MCNP 5 and WINXCOM simulated calculation
International Nuclear Information System (INIS)
Zhang Zhicheng; Zhang Jinzhao; Liu Ze; Lu Chunhai; Chen Min
2013-01-01
Background: Currently, lead glass is widely used as observation window, while lead is toxic heavy metal. Purpose: Non-toxic materials and their shielding effects are researched in order to find a new material to replace lead containing material. Methods: The mass attenuation coefficients of bismuth silicate glass were investigated with gamma-ray's energy at 0.662 MeV, 1.17 MeV and 1.33 MeV, respectively, by MCNP 5 (Monte Carlo) and WINXCOM program, and compared with those of the lead glass. Results: With attenuation factor K, shielding and mechanical properties taken into consideration bismuth glass containing 50% bismuth oxide might be selected as the right material. Dose rate distributions of water phantom were calculated with 2-cm and 10-cm thick glass, respectively, irradiated by 137 Cs and 60 Co in turn. Conclusion: Results show that the bismuth glass may replace lead glass for radiation shielding with appropriate energy. (authors)
12. Corrosion by liquid lead and lead-bismuth: experimental results review and analysis
Energy Technology Data Exchange (ETDEWEB)
Zhang, Jinsuo [Los Alamos National Laboratory
2008-01-01
Liquid metal technologies for liquid lead and lead-bismuth alloy are under wide investigation and development for advanced nuclear energy systems and waste transmutation systems. Material corrosion is one of the main issues studied a lot recently in the development of the liquid metal technology. This study reviews corrosion by liquid lead and lead bismuth, including the corrosion mechanisms, corrosion inhibitor and the formation of the protective oxide layer. The available experimental data are analyzed by using a corrosion model in which the oxidation and scale removal are coupled. Based on the model, long-term behaviors of steels in liquid lead and lead-bismuth are predictable. This report provides information for the selection of structural materials for typical nuclear reactor coolant systems when selecting liquid lead or lead bismuth as heat transfer media.
13. On the origin of near-IR luminescence in SiO{sub 2} glass with bismuth as the single dopant. Formation of the photoluminescent univalent bismuth silanolate by SiO{sub 2} surface modification
Energy Technology Data Exchange (ETDEWEB)
Romanov, A.N., E-mail: [email protected]; Haula, E.V.; Shashkin, D.P.; Vtyurina, D.N.; Korchak, V.N.
2017-03-15
Near infrared photoluminescent bismuth(I) silanolate centers ((≡Si-O){sub 3}Si–O-Bi) were prepared on the surface of SiO{sub 2} xerogel, by the treatment in the vapors of bismuth(I) chloride. The optical properties of these groups are almost identical to that of photoluminescent centers in the bulk SiO{sub 2} glasses with bismuth as the single dopant. - Highlights: • univalent bismuth silanolate can be prepared on SiO{sub 2} surface by treatment in BiCl vapors. • univalent bismuth silanolate is responsible for NIR photoluminescence in Bi-doped SiO{sub 2} glass. • univalent bismuth silanolate is the active center in laser, operating on Bi-doped SiO{sub 2} fiber.
14. Study of irradiation defects in bismuth by electric transport measurements
International Nuclear Information System (INIS)
Le Goff, M.
1984-01-01
Pure monocrystalline bismuth is irradiated near 4K by electrons of different energies. Irradiation effects are measured by galvanomagnetic properties at low temperature. Frenkel pairs created during irradiation have a strong effect on carrier mobilities. The data are quantitatively analyzed assuming a rigid band model. After irradiation with 1 MeV electrons, each Frankel pair created corresponds to a total charge of 0.14 electrons. This result obtained by magnetoresistance and Hall effect is confirmed by Shubnikov-de Haas experiments. There is a linear variation between the excess carrier density (p-n) and the Frenkel pair concentration. The more important step of annealing is observed around 40-50 K. This step is attributed to interstitial migration. Resistivity presents a minimum at low temperature after irradiation with electrons of energy over 1.3 MeV. This is explained by virtual bound levels near the Fermi level. The Kondo effect bound to magnetic defects is discussed [fr
15. Ni-rich precipitates in a lead bismuth eutectic loop
International Nuclear Information System (INIS)
Kikuchi, K.; Saito, S.; Hamaguchi, D.; Tezuka, M.
2010-01-01
Solidified LBE was sampled from the specimens, electro-magnetic pump, filter, drain valve and oxygen sensor at the JAEA Lead Bismuth Loop-1 (JLBL-1) where the structural material was made of SS316. The concentration of Ni, Fe and Cr in LBE were analyzed by the Inductive Coupled Plasma atomic emission spectrometer. It was concluded that the solution of Ni into LBE was not saturated although the concentration of Fe and Cr almost achieved to the values in the literature. A needle-type structure appeared on the surface of solidified LBE inside the tube specimens. It was found to be Ni-rich precipitates by X-ray analyses (Field Emission Scanning Electron Microscope, FE-SEM). LBE samples collected from a circulating loop after discharging did not show the amount of impurities equivalent to the LBE bulk property.
16. Ni-rich precipitates in a lead bismuth eutectic loop
Energy Technology Data Exchange (ETDEWEB)
Kikuchi, K., E-mail: [email protected] [Ibaraki University, IQBRC, Tokai, Ibaraki 319-1106 (Japan); Saito, S.; Hamaguchi, D.; Tezuka, M. [J-PARC Center, JAEA, Tokai, Ibaraki 319-1195 (Japan)
2010-03-15
Solidified LBE was sampled from the specimens, electro-magnetic pump, filter, drain valve and oxygen sensor at the JAEA Lead Bismuth Loop-1 (JLBL-1) where the structural material was made of SS316. The concentration of Ni, Fe and Cr in LBE were analyzed by the Inductive Coupled Plasma atomic emission spectrometer. It was concluded that the solution of Ni into LBE was not saturated although the concentration of Fe and Cr almost achieved to the values in the literature. A needle-type structure appeared on the surface of solidified LBE inside the tube specimens. It was found to be Ni-rich precipitates by X-ray analyses (Field Emission Scanning Electron Microscope, FE-SEM). LBE samples collected from a circulating loop after discharging did not show the amount of impurities equivalent to the LBE bulk property.
17. Ni-rich precipitates in a lead bismuth eutectic loop
Science.gov (United States)
Kikuchi, K.; Saito, S.; Hamaguchi, D.; Tezuka, M.
2010-03-01
Solidified LBE was sampled from the specimens, electro-magnetic pump, filter, drain valve and oxygen sensor at the JAEA Lead Bismuth Loop-1 (JLBL-1) where the structural material was made of SS316. The concentration of Ni, Fe and Cr in LBE were analyzed by the Inductive Coupled Plasma atomic emission spectrometer. It was concluded that the solution of Ni into LBE was not saturated although the concentration of Fe and Cr almost achieved to the values in the literature. A needle-type structure appeared on the surface of solidified LBE inside the tube specimens. It was found to be Ni-rich precipitates by X-ray analyses (Field Emission Scanning Electron Microscope, FE-SEM). LBE samples collected from a circulating loop after discharging did not show the amount of impurities equivalent to the LBE bulk property.
18. Coolant Chemistry Control: Oxygen Mass Transport in Lead Bismuth Eutectic
International Nuclear Information System (INIS)
Weisenburger, A.; Mueller, G.; Bruzzese, C.; Glass, A.
2015-01-01
In lead-bismuth cooled transmutation systems, oxygen, dissolved in the coolant at defined quantities, is required for stable long-term operation by assuring the formation of protective oxide scales on structural steel surfaces. Extracted oxygen must be permanently delivered to the system and distributed in the entire core. Therefore, coolant chemistry control involves detailed knowledge on oxygen mass transport. Beside the different flow regimes a core might have stagnant areas at which oxygen delivery can only be realised by diffusion. The difference between oxygen transport in flow paths and in stagnant zones is one of the targets of such experiments. To investigate oxygen mass transport in flowing and stagnant conditions, a dedicated facility was designed based on computational fluid dynamics (CFD). CFD also was applied to define the position of oxygen sensors and ultrasonic Doppler velocimetry transducers for flow measurements. This contribution will present the test facility, design relevant CFD calculations and results of first tests performed. (authors)
19. Bismuth Sodium Titanate Based Materials for Piezoelectric Actuators.
Science.gov (United States)
Reichmann, Klaus; Feteira, Antonio; Li, Ming
2015-12-04
The ban of lead in many electronic products and the expectation that, sooner or later, this ban will include the currently exempt piezoelectric ceramics based on Lead-Zirconate-Titanate has motivated many research groups to look for lead-free substitutes. After a short overview on different classes of lead-free piezoelectric ceramics with large strain, this review will focus on Bismuth-Sodium-Titanate and its solid solutions. These compounds exhibit extraordinarily high strain, due to a field induced phase transition, which makes them attractive for actuator applications. The structural features of these materials and the origin of the field-induced strain will be revised. Technologies for texturing, which increases the useable strain, will be introduced. Finally, the features that are relevant for the application of these materials in a multilayer design will be summarized.
20. Lead-Bismuth technology ; corrosion resistance of structural materials
Energy Technology Data Exchange (ETDEWEB)
Jeong, Ji Young; Park, Won Seok [Korea Atomic Energy Research Institute, Taejeon (Korea)
2000-02-01
Lead-Bismuth (Pb-Bi) eutectic alloy was determined as a coolant material for the HYPER system being studied by KAERI. The Pb-Bi alloy as a coolant, has a number of the favorable thermo-physical and technological properties, while it is comparatively corrosive to the structural materials. It is necessary to solve this problem for providing a long failure-proof operation of the facilities with Pb-Bi coolant. It seems to be possible to maintain corrosion resistance on structural material up to 600 deg C by using of various technologies, but it needs more studies for application to large-scale NPPs. 22 refs., 11 figs., 7 tabs. (Author)
1. Stimulated Raman scattering of sub-millimeter waves in bismuth
Science.gov (United States)
Kumar, Pawan; Tripathi, V. K.
2007-12-01
A high-power sub-millimeter wave propagating through bismuth, a semimetal with non-spherical energy surfaces, parametrically excites a space-charge mode and a back-scattered electromagnetic wave. The free carrier density perturbation associated with the space-charge wave couples with the oscillatory velocity due to the pump to derive the scattered wave. The scattered and pump waves exert a pondermotive force on electrons and holes, driving the space-charge wave. The collisional damping of the decay waves determines the threshold for the parametric instability. The threshold intensity for 20 μm wavelength pump turns out to be ˜2×1012 W/cm2. Above the threshold, the growth rate scales increase with ωo, attain a maximum around ωo=6.5ωp, and, after this, falls off.
2. Radiopacity and histological assessment of Portland cement plus bismuth oxide.
Science.gov (United States)
Coutinho-Filho, Tauby; De-Deus, Gustavo; Klein, Leila; Manera, Gisele; Peixoto, Carla; Gurgel-Filho, Eduardo Diogo
2008-12-01
The present study evaluated the subcutaneous connective tissue reactions and the radiopacity of MTA, Portland cement (PC), and Portland cement plus bismuth oxide (BO). Forty rats were divided into 5 groups (n = 8 per group): A1: Control (empty capsule); A2: Pro-Root MTA; A3: PC; A4: PC + BO 1:1; and A5: PC + BO 2:1. Polyethylene tubes were filled with the test materials and standardized radiographic images were taken. Histological evaluation was done after 7 and 60 days. Student t test and Fisher's test were used in the statistical analysis (P A4 > A5 > A3. No differences were found for the tissue response in the 2 experimental periods. A positive correlation between BO concentration and radiopacity of PC was determined. The histological evaluation suggests that all studied materials were biocompatible at 7 and 60 days.
3. High ionic conductivity in confined bismuth oxide-based heterostructures
Directory of Open Access Journals (Sweden)
Simone Sanna
2016-12-01
Full Text Available Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3 exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure δ-Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ, deposited by pulsed laser deposition. The resulting [δ-Bi2O3/YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C and exhibits stable high ionic conductivity over a long time comparable to the value of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk.
4. High ionic conductivity in confined bismuth oxide-based heterostructures
DEFF Research Database (Denmark)
Sanna, Simone; Esposito, Vincenzo; Christensen, Mogens
2016-01-01
Bismuth trioxide in the cubic fluorite phase (δ-Bi2O3) exhibits the highest oxygen ionic conductivity. In this study, we were able to stabilize the pure -Bi2O3 at low temperature with no addition of stabilizer but only by engineering the interface, using highly coherent heterostructures made...... of alternative layers of δ-Bi2O3 and Yttria Stabilized Zirconia (YSZ), deposited by pulsed laser deposition. The resulting [δ-Bi2O3=YSZ] heterostructures are found to be stable over a wide temperature range (500-750 °C) and exhibits stable high ionic conductivity over a long time comparable to the value...... of the pure δ-Bi2O3, which is approximately two orders of magnitude higher than the conductivity of YSZ bulk....
5. A novel route to nanosized molybdenum boride and carbide and/or metallic molybdenum by thermo-synthesis method from MoO3, KBH4, and CCl4
International Nuclear Information System (INIS)
Li Yuanzhi; Fan Yining; Chen Yi
2003-01-01
Nanosized molybdenum boride and carbide were synthesized from MoO 3 , KBH 4 , and CCl 4 by thermo-synthesis method at lower temperature. The relative content of Mo, Mo 2 C, and molybdenum boride in the product was decided by the molar ratio between MoO 3 , KBH 4 , and CCl 4 . Increasing the molar ratio of CCl 4 to MoO 3 was favorable to the production of Mo 2 C. Increasing the molar ratio of KBH 4 to MoO 3 was favorable to the production of molybdenum boride. By carefully adjusting the reaction conditions and annealing in Ar at 900 deg. C, a single phase of MoB could be obtained
6. Study of bismuth minerals belonging to the mineralogical collection from the National Museum
International Nuclear Information System (INIS)
Baptista, A.; Baptista, N.R.
1991-09-01
With the purpose of searching the presence of Tellurium minerals in the Ouro Preto-Mariana country, Minas Gerais State, and considering the existence of a great number of minerals in which this element come across allied with Bismuth, samples of the mineralogical collection of the Museu Nacional, proceeding that region and classified as Bismuth minerals were studied by X-ray fluorescence analysis and diffractometric analysis. In this report the results of this research are presented. (Author)
International Nuclear Information System (INIS)
Akperov, M.M.; Ismailov, Sh.S.; Shukyurova, A.A.
2004-01-01
Results of study of the Gd impurities effect on the bismuth telluride thermo-electric properties are presented. The experiment was carried out within the temperature range T=300-700 K. It is determined, that at temperature increase the energy level is appreciably closing up to bismuth telluride forbidden zone which makes up 0.16-0.24 eV. Such anomalous energy properties of gadolinium in telluride affect on material thermoelectric properties
8. An acclerator-based installation of small power with the lead-bismuth coolant
Energy Technology Data Exchange (ETDEWEB)
Gorshkov, V.T.; Yefimov, E.I.; Novikova, N.N. [Research and Development Bereau, Podolsk (Russian Federation)] [and others
1995-10-01
The structure of the accelerator-based installation is described that includes the subcritical reactor-blanket with power 15 MW(h) cooled with lead-bismuth, the lead-bismuth flow target where a beam of {alpha}-particle is injected, the equipment of a primary and secondary curcuits. Some results of calculations and estimations are discussed that have been carried out to justify the target and blanket constructions. Some main characteristics of the installation are presented.
9. Bismuth oxide nanorods based immunosensor for mycotoxin detection
Energy Technology Data Exchange (ETDEWEB)
Solanki, Pratima R., E-mail: [email protected] [DST Centre for Biomolecular Electronics, CSIR-National Physical Laboratory, K.S. Krishnan Marg, New Delhi (India); Special Centre for Nano Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Singh, Jay [DST Centre for Biomolecular Electronics, CSIR-National Physical Laboratory, K.S. Krishnan Marg, New Delhi (India); Department of Applied Chemistry and Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Rupavali, Bharti [DST Centre for Biomolecular Electronics, CSIR-National Physical Laboratory, K.S. Krishnan Marg, New Delhi (India); Tiwari, Sachchidanand [Special Centre for Nano Sciences, Jawaharlal Nehru University, New Delhi 110067 (India); Malhotra, Bansi D., E-mail: [email protected] [DST Centre for Biomolecular Electronics, CSIR-National Physical Laboratory, K.S. Krishnan Marg, New Delhi (India); Department of Biotechnology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India)
2017-01-01
We report results of the studies relating to fabrication of an efficient immunosensor based on bismuth oxide nanorods (nBi{sub 2}O{sub 3}), electrophoretically deposited onto indium-tin-oxide (ITO) coated glass substrate. This immunosensor was fabricated by immobilization of anti-aflatoxin monoclonal antibodies (Ab-AFB1) and bovine serum albumin (BSA) for aflatoxin B1 detection. The structural and morphological studies of n-Bi{sub 2}O{sub 3} have been carried out by XRD, UV–vis spectrophotometer; SEM, AFM and FTIR. It was found that the nBi{sub 2}O{sub 3} provided improved sensing characteristics to the electrode interface in terms of electroactive surface area, diffusion coefficient, charge transfer rate constant and electron transfer kinetics. The results of electrochemical response studies of this BSA/Ab-AFB1/nBi{sub 2}O{sub 3}/ITO immunosensor revealed good linearity in the range of 1–70 ng dL{sup −1} with low detection limit of 8.715 ng/dL, improved sensitivity of 1.132 μA/(ng/dL cm{sup −2}), regression coefficient R{sup 2} of 0.918 and reproducibility of > 11 times. The association constant for the BSA/Ab-AFB1/nBi{sub 2}O{sub 3}/ITO immunosensor was determined as 7.318 ng/dL. - Highlights: • Use of Bismuth oxide nanorods for aflatoxin B1 detection. • It improved the electrochemical properties. • First report on nBi{sub 2}O{sub 3} for mycotoxin detection.
10. Magnetic properties of the binary Nickel/Bismuth alloy
Energy Technology Data Exchange (ETDEWEB)
Keskin, Mustafa; Şarlı, Numan, E-mail: [email protected]
2017-09-01
Highlights: • We model and investigate the magnetic properties of the Ni/Bi alloy within the EFT. • Magnetizations of the Ni/Bi alloy are observed as Bi1 > Bi2 > Ni/Bi > Ni at T < Tc. • Magnetization of the Bi1 is dominant and Ni is at least dominant T < Tc. • Total magnetization of the Ni/Bi alloy is close to those of Ni at T < Tc. • Hysteresis curves are overlap at T < 0.1 and they behave separately at T > 0.1. - Abstract: Magnetic properties of the binary Nickel/Bismuth alloy (Ni/Bi) are investigated within the effective field theory. The Ni/Bi alloy has been modeled that the rhombohedral Bi lattice is surrounded by the hexagonal Ni lattice. According to lattice locations, Bi atoms have two different magnetic properties. Bi1 atoms are in the center of the hexagonal Ni atoms (Ni/Bi1 single layer) and Bi2 atoms are between two Ni/Bi1 bilayers. The Ni, Bi1, Bi2 and Ni/Bi undergo a second-order phase transition from the ferromagnetic phase to paramagnetic phase at Tc = 1.14. The magnetizations of the Ni/Bi alloy are observed as Bi1 > Bi2 > Ni/Bi > Ni at T < Tc; hence the magnetization of the Bi1 is dominant and Ni is at least dominant. However, the total magnetization of the Ni/Bi alloy is close to magnetization of the Ni at T < Tc. The corcivities of the Ni, Bi1, Bi2 and Ni/Bi alloy are the same with each others, but the remanence magnetizations are different. Our theoretical results of M(T) and M(H) of the Ni/Bi alloy are in quantitatively good agreement with the some experimental results of binary Nickel/Bismuth systems.
11. Studies of corrosion resistance of Japanese steels in liquid lead-bismuth
International Nuclear Information System (INIS)
Kamata, Kin-ya; Ono, Hiroshi; Kitano, Teruaki; Ono, Mikinori
2003-01-01
Liquid lead-bismuth has attractive characteristics as a coolant in future fast reactors and Accelerator Driven Sub-critical Systems (ADS) applications. The corrosion behavior of structural materials in lead-bismuth eutectic is one of key problems in developing nuclear power plants and installations using lead-bismuth coolant. Our experiences with heat exchangers using liquid lead-bismuth and the results of corrosion tests of Japanese steels are reported in this paper. A series of corrosion tests was carried out in collaboration with the Institute of Physics and Power Engineering (IPPE). Test specimens of various Japanese steels were exposed in a non-isothermal forced circulation loop. The influence of maximum temperature and oxygen content in lead bismuth were chosen for study as the primary causes of corrosion in Japanese steels. After the corrosion tests, corrosion behavior was analyzed by visual inspection, measurement of weight loss and metallurgical examination of the microstructure of the corroded zone. The corrosion mechanism in liquid lead bismuth is discussed on the basis of the metallurgical examination of the corroded zone. (author)
12. Nano sized bismuth oxy chloride by metal organic chemical vapour deposition
Energy Technology Data Exchange (ETDEWEB)
Jagdale, Pravin, E-mail: [email protected] [Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 (Italy); Castellino, Micaela [Center for Space Human Robotics, Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Torino (Italy); Marrec, Françoise [Laboratory of Condensed Matter Physics, University of Picardie Jules Verne (UPJV), Amiens 80039 (France); Rodil, Sandra E. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexicom (UNAM), Mexico D.F. 04510 (Mexico); Tagliaferro, Alberto [Department of Applied Science and Technology (DISAT), Politecnico di Torino, 10129 (Italy)
2014-06-01
Metal organic chemical vapour deposition (MOCVD) method was used to prepare thin films of bismuth based nano particles starting from bismuth salts. Nano sized bismuth oxy chloride (BiOCl) crystals were synthesized from solution containing bismuth chloride (BiCl{sub 3}) in acetone (CH{sub 3}-CO-CH{sub 3}). Self-assembly of nano sized BiOCl crystals were observed on the surface of silicon, fused silica, copper, carbon nanotubes and aluminium substrates. Various synthesis parameters and their significant impact onto the formation of self-assembled nano-crystalline BiOCl were investigated. BiOCl nano particles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and Micro-Raman spectroscopy. These analyses confirm that bismuth nanometer-sized crystal structures showing a single tetragonal phase were indeed bismuth oxy chloride (BiOCl) square platelets 18–250 nm thick and a few micrometres wide.
13. Evaluation of the strength and radiopacity of Portland cement with varying additions of bismuth oxide.
Science.gov (United States)
Saliba, E; Abbassi-Ghadi, S; Vowles, R; Camilleri, J; Hooper, S; Camilleri, J
2009-04-01
To study the effect of addition of various proportions of bismuth oxide on compressive strength and radiopacity of Portland cement. The compressive strength of white Portland cement and cement replaced with 10, 15, 20, 25 and 30% bismuth oxide was evaluated by testing cylinders 6 mm in diameter and 12 mm high. Twelve cylinders were tested for each material under study. The radiopacity of the cements tested was evaluated using an aluminium step-wedge and densitometer. The optical density was compared with the relevant thickness of aluminium (Al). Statistical analysis was performed using Analysis of Variance (ANOVA) with P = 0.05 and Tukey test to perform multiple comparison tests. Various additions of bismuth oxide had no significant effect on the strength of the material when compared with the unmodified Portland cement (P > 0.05). The radiopacity of the cements tested ranged from 2.02 mm Al for Portland cement to 9.79 mm Al for the highest bismuth replacement. Addition of bismuth oxide did not affect the compressive strength of Portland cement. All the bismuth oxide cement mixtures had radio-opacities higher than 3 mm thickness of aluminium.
14. Extreme Pressure Synergistic Mechanism of Bismuth Naphthenate and Sulfurized Isobutene Additives
Science.gov (United States)
Xu, Xin; Hu, Jianqiang; Yang, Shizhao; Xie, Feng; Guo, Li
A four-ball tester was used to evaluate the tribological performances of bismuth naphthenate (BiNap), sulfurized isobutene (VSB), and their combinations. The results show that the antiwear properties of BiNap and VSB are not very visible, but they possess good extreme pressure (EP) properties, particularly sulfur containing bismuth additives. Synergistic EP properties of BiNap with various sulfur-containing additives were investigated. The results indicate that BiNap exhibits good EP synergism with sulfur-containing additives. The surface analytical tools, such as X-ray photoelectron spectrometer (XPS) scanning electron microscope (SEM) and energy dispersive X-ray (EDX), were used to investigate the topography, composition contents, and depth profile of some typical elements on the rubbing surface. Smooth topography of wear scar further confirms that the additive showed good EP capacities, and XPS and EDX analyzes indicate that tribochemical mixed protective films composed of bismuth, bismuth oxides, sulfides, and sulfates are formed on the rubbing surface, which improves the tribological properties of lubricants. In particular, a large number of bismuth atoms and bismuth sulfides play an important role in improving the EP properties of oils.
15. Intrinsic stress of bismuth oxide thin films: effect of vapour chopping and air ageing
International Nuclear Information System (INIS)
Patil, R B; Puri, R K; Puri, V
2008-01-01
Bismuth oxide thin films of thickness 1000 A 0 have been prepared by thermal oxidation (in air) of vacuum evaporated bismuth thin films (on glass substrate) at different oxidation temperatures and duration. Both the vapour chopped and nonchopped bismuth oxide thin films showed polycrystalline and polymorphic structure. The monoclinic bismuth oxide was found to be predominant in both the cases. The effect of vapour chopping and air exposure for 40 days on the intrinsic stress of bismuth oxide thin films has been studied. The vapour chopped films showed low (3.92 - 4.80 x 10 9 N/m 2 ) intrinsic stress than those of nonchopped bismuth oxide thin films (5.77 - 6.74 x 10 9 N/m 2 ). Intrinsic stress was found to increase due to air ageing. The effect of air ageing on the vapour chopped films was found low. The vapour chopped films showed higher packing density. Higher the packing density, lower the film will age. The process of chopping vapour flow creates films with less inhomogenety i.e. a low concentration of flaws and non-planar defects which results in lower intrinsic stress
16. Extraction of lanthanide elements and bismuth in molten lithium chloride-liquid bismuth-lithium alloy system
International Nuclear Information System (INIS)
1987-01-01
The equilibrium distributions of neodymium and samarium between molten LiCl and liquid Bi-Li alloy were measured in a wide range of Li-mole fraction in the alloy phase, X Li . These lanthanide elements were extracted through redox reactions. In high X Li range, X Li > 0.03, the distributions of neodymium and bismuth in the salt phase increased markedly. The anomalous increase is attributed to the formation of the compound comprized of Nd, Li, Bi and oxygen in the salt phase. The reaction processes in samarium and neodymium were very fast and the extraction rates are controlled by the diffusion processes of the solutes and metallic lithium. (author)
17. Neutron activation determination of impurities in high-purity bismuth with separation of matrix in form of hydroxide
International Nuclear Information System (INIS)
Artyukhin, P.I.; Shavinskij, B.M.; Mityakin, Yu.L.
1979-01-01
The technique of neutron activation determination of 15 impurity elements (Au, Ag, Ba, Cd, Co, Cs, Cu, Hg, K, Na, Ni, Se, Sr, Te, Zn) in high-purity bismuth (impurity content is approximately 10 -6 -10 -10 %) is presented. Bismuth hydroxide precipitation by ammonia from nitric acid solutions was used to separate bismuth from alkali, alkaline earth metals and elements forming stable ammines. Gold, selenium and tellurium are isolated in the form of metals at reduction by muriatic hydrazine. Results of analyzing two samples of special purity bismuth are presented. Neutron flux comprised 0.8-1x10 13 n/cm 2 xs. Radiation time was equal to 90 hours
18. Elevated temperature tensile properties of borated 304 stainless steel: Effect of boride dispersion on strength and ductility
International Nuclear Information System (INIS)
Stephens, J.J.; Sorenson, K.B.; McConnell, P.
1992-01-01
19. The effect of lanthanum boride on the sintering, sintered microstructure and mechanical properties of titanium and titanium alloys
International Nuclear Information System (INIS)
Yang, Y.F.; Luo, S.D.; Qian, M.
2014-01-01
An addition of ≤0.5 wt% lanthanum boride (LaB 6 ) to powder metallurgy commercially pure Ti (CP-Ti), Ti–6Al–4V and Ti–10V–2Fe–3Al (all in wt%) resulted in improved sintered density, substantial microstructural refinement, and noticeably increased tensile elongation. The addition of LaB 6 led to scavenging of both oxygen (O) and chlorine (Cl) from the titanium powder during sintering, evidenced by the formation of La 2 O 3 and LaCl x O y . The pinning effect of La 2 O 3 , LaCl x O y and TiB inhibited prior-β grain growth and resulted in subsequent smaller α-laths. The formation of nearly equiaxed α-Ti phase is partially attributed to the nucleation effect of α-Ti on TiB. The improved sintered density was caused by B from LaB 6 rather than La, while excessive formation of La 2 O 3 and TiB with an addition of >0.5 wt% LaB 6 resulted in a noticeable decrease in sintered density. The improved tensile elongation with an addition of ≤0.5 wt% LaB 6 was mainly attributed to the scavenging of oxygen by LaB 6 , partially assisted by the improved sintered density. However, an addition of >0.5 wt% LaB 6 led to the formation of large La 2 O 3 aggregates and more brittle TiB whiskers and therefore decreased tensile elongation. Balanced scavenging of O is thus important. The optimal addition of LaB 6 was 0.5 wt% but this may change depending on the powder size of the LaB 6 to be used
20. Corrosion behavior of Si-enriched steels for nuclear applications in liquid lead–bismuth
Energy Technology Data Exchange (ETDEWEB)
Kurata, Yuji, E-mail: [email protected] [Japan Atomic Energy Agency, Tokai-mura, Ibaraki-ken 319-1195 (Japan)
2013-06-15
1. Zerovalent bismuth nanoparticles inhibit Streptococcus mutans growth and formation of biofilm
Directory of Open Access Journals (Sweden)
2012-04-01
Full Text Available Rene Hernandez-Delgadillo1, Donaji Velasco-Arias2, David Diaz2, Katiushka Arevalo-Niño1, Marianela Garza-Enriquez1, Myriam A De la Garza-Ramos1, Claudio Cabral-Romero11Instituto de Biotecnologia, Centro de Investigacion y Desarrollo en Ciencias de la Salud, CIDICS, Facultad de Odontologia, Universidad Autonoma de Nuevo Leon, UANL, Monterrey, Nuevo Leon, 2Facultad de Quimica, Universidad Nacional Autonoma de Mexico, Distrito Federal, MexicoBackground and methods: Despite continuous efforts, the increasing prevalence of resistance among pathogenic bacteria to common antibiotics has become one of the most significant concerns in modern medicine. Nanostructured materials are used in many fields, including biological sciences and medicine. While some bismuth derivatives has been used in medicine to treat vomiting, nausea, diarrhea, and stomach pain, the biocidal activity of zerovalent bismuth nanoparticles has not yet been studied. The objective of this investigation was to analyze the antimicrobial activity of bismuth nanoparticles against oral bacteria and their antibiofilm capabilities.Results: Our results showed that stable colloidal bismuth nanoparticles had 69% antimicrobial activity against Streptococcus mutans growth and achieved complete inhibition of biofilm formation. These results are similar to those obtained with chlorhexidine, the most commonly used oral antiseptic agent. The minimal inhibitory concentration of bismuth nanoparticles that interfered with S. mutans growth was 0.5 mM.Conclusion: These results suggest that zerovalent bismuth nanoparticles could be an interesting antimicrobial agent to be incorporated into an oral antiseptic preparation.Keywords: zerovalent bismuth nanoparticles, antimicrobial agent, biofilm, Streptococcus mutans
2. Bismuth oxide aqueous colloidal nanoparticles inhibit Candida albicans growth and biofilm formation
Directory of Open Access Journals (Sweden)
2013-04-01
Full Text Available Rene Hernandez-Delgadillo,1 Donaji Velasco-Arias,3 Juan Jose Martinez-Sanmiguel,2 David Diaz,3 Inti Zumeta-Dube,3 Katiushka Arevalo-Niño,1 Claudio Cabral-Romero2 1Facultad de Ciencias Biológicas, Instituto de Biotecnologia, Universidad Autonoma de Nuevo Leon, UANL, Monterrey, Mexico; 2Facultad de Odontología, Universidad Autonoma de Nuevo Leon, UANL, Monterrey, México; 3Facultad de Quimica, Universidad Nacional Autonoma de Mexico, UNAM, Distrito Federal, México Abstract: Multiresistance among microorganisms to common antimicrobials has become one of the most significant concerns in modern medicine. Nanomaterials are a new alternative to successfully treat the multiresistant microorganisms. Nanostructured materials are used in many fields, including biological sciences and medicine. Recently, it was demonstrated that the bactericidal activity of zero-valent bismuth colloidal nanoparticles inhibited the growth of Streptococcus mutans; however the antimycotic potential of bismuth nanostructured derivatives has not yet been studied. The main objective of this investigation was to analyze the fungicidal activity of bismuth oxide nanoparticles against Candida albicans, and their antibiofilm capabilities. Our results showed that aqueous colloidal bismuth oxide nanoparticles displayed antimicrobial activity against C. albicans growth (reducing colony size by 85% and a complete inhibition of biofilm formation. These results are better than those obtained with chlorhexidine, nystatin, and terbinafine, the most effective oral antiseptic and commercial antifungal agents. In this work, we also compared the antimycotic activities of bulk bismuth oxide and bismuth nitrate, the precursor metallic salt. These results suggest that bismuth oxide colloidal nanoparticles could be a very interesting candidate as a fungicidal agent to be incorporated into an oral antiseptic. Additionally, we determined the minimum inhibitory concentration for the synthesized
3. Sulfate-reducing bacteria slow intestinal transit in a bismuth-reversible fashion in mice.
Science.gov (United States)
Ritz, N L; Lin, D M; Wilson, M R; Barton, L L; Lin, H C
2017-01-01
Hydrogen sulfide (H 2 S) serves as a mammalian cell-derived gaseous neurotransmitter. The intestines are exposed to a second source of this gas by sulfate-reducing bacteria (SRB). Bismuth subsalicylate binds H 2 S rendering it insoluble. The aim of this study was to test the hypothesis that SRB may slow intestinal transit in a bismuth-reversible fashion. Eighty mice were randomized to five groups consisting of Live SRB, Killed SRB, SRB+Bismuth, Bismuth, and Saline. Desulfovibrio vulgaris, a common strain of SRB, was administered by gavage at the dose of 1.0 × 10 9 cells along with rhodamine, a fluorescent dye. Intestinal transit was measured 50 minutes after gavage by euthanizing the animals, removing the small intestine between the pyloric sphincter and the ileocecal valve and visualizing the distribution of rhodamine across the intestine using an imaging system (IVIS, Perkin-Elmer). Intestinal transit (n=50) was compared using geometric center (1=minimal movement, 100=maximal movement). H 2 S concentration (n=30) was also measured when small intestinal luminal content was allowed to generate this gas. The Live SRB group had slower intestinal transit as represented by a geometric center score of 40.2 ± 5.7 when compared to Saline: 73.6 ± 5.7, Killed SRB: 77.9 ± 6.9, SRB+Bismuth: 81.0 ± 2.0, and Bismuth: 73.3 ± 4.2 (Pfashion in mice. Our results demonstrate that intestinal transit is slowed by SRB and this effect could be abolished by H 2 S-binding bismuth. © 2016 John Wiley & Sons Ltd.
4. Spectroscopic Characterization of Extracellular Polymeric Substances from Escherichia coli and Serratia marcescens: Suppression using Sub-Inhibitory Concentrations of Bismuth Thiols
Energy Technology Data Exchange (ETDEWEB)
Badireddy, Appala R.; Korpol, Bhoom Reddy; Chellam, Shankararaman; Gassman, Paul L.; Engelhard, Mark H.; Lea, Alan S.; Rosso, Kevin M.
2008-10-21
Free and capsular EPS produced by Escherichia coli and Serratia marcescens were characterized in detail using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Total EPS production decreased upon treatment with sub-inhibitory concentrations of lipophilic bismuth thiols (bismuth dimercaptopropanol, BisBAL; bismuth ethanedithiol, BisEDT; and bismuth pyrithione, BisPYR), BisBAL being most effective. Bismuth thiols also influenced acetylation and carboxylation of polysaccharides in EPS from S. marcescens. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, polysaccharides, and nucleic acids varying predominantly only in the total amount expressed. Second derivative analysis of the amide I region of FTIR spectra revealed decreases in protein secondary structures in the presence of bismuth thiols. Hence, anti-fouling properties of bismuth thiols appear to originate in their ability to suppress O-acetylation and protein secondary structures in addition to total EPS secretion.
5. Reactive magnetron sputtering deposition of bismuth tungstate onto titania nanoparticles for enhancing visible light photocatalytic activity
Energy Technology Data Exchange (ETDEWEB)
Ratova, Marina, E-mail: [email protected] [Surface Engineering Group, School of Engineering, Manchester Metropolitan University, Manchester, M1 5GD (United Kingdom); Kelly, Peter J.; West, Glen T. [Surface Engineering Group, School of Engineering, Manchester Metropolitan University, Manchester, M1 5GD (United Kingdom); Tosheva, Lubomira; Edge, Michele [School of Science and the Environment, Manchester Metropolitan University, Manchester M1 5GD (United Kingdom)
2017-01-15
Highlights: • Bismuth tungstate coatings were deposited by reactive magnetron sputtering. • Oscillating bowl was introduced to the system to enable coating of nanopartulates. • Deposition of Bi{sub 2}WO{sub 6} enhanced visible light activity of titania nanoparticles. • The best results were obtained for coating with Bi:W ratio of approximately 2:1. • Deposition of Bi{sub 2}WO{sub 6} onto TiO{sub 2} resulted in more efficient electron-hole separation. - Abstract: Titanium dioxide − bismuth tungstate composite materials were prepared by pulsed DC reactive magnetron sputtering of bismuth and tungsten metallic targets in argon/oxygen atmosphere onto anatase and rutile titania nanoparticles. The use of an oscillating bowl placed beneath the two magnetrons arranged in a co-planar closed field configuration enabled the deposition of bismuth tungstate onto loose powders, rather than a solid substrate. The atomic ratio of the bismuth/tungsten coatings was controlled by varying the power applied to each target. The effect of the bismuth tungstate coatings on the phase, optical and photocatalytic properties of titania was investigated by X-ray diffraction, energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area measurements, transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy and an acetone degradation test. The latter involved measurements of the rate of CO{sub 2} evolution under visible light irradiation of the photocatalysts, which indicated that the deposition of bismuth tungstate resulted in a significant enhancement of visible light activity, for both anatase and rutile titania particles. The best results were achieved for coatings with a bismuth to tungsten atomic ratio of 2:1. In addition, the mechanism by which the photocatalytic activity of the TiO{sub 2} nanoparticles was enhanced by compounding it with bismuth tungstate was studied by microwave cavity perturbation. The results of these
6. Bismuth nanoparticles synthesized by laser ablation in lubricant oils for tribological tests
Energy Technology Data Exchange (ETDEWEB)
Flores-Castañeda, M., E-mail: [email protected] [Universidad Autónoma del Estado de México, Av. Instituto Literario No. 100, Oriente Col. Centro, Toluca, Estado de México C.P. 50000, México (Mexico); Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, La Marquesa, Ocoyoacac, Edo. de México C.P. 52750, México (Mexico); Camps, E. [Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca s/n, La Marquesa, Ocoyoacac, Edo. de México C.P. 52750, México (Mexico); Camacho-López, M. [Universidad Autónoma del Estado de México, Av. Instituto Literario No. 100, Oriente Col. Centro, Toluca, Estado de México C.P. 50000, México (Mexico); Muhl, S. [Instituto de Investigación en Materiales (UNAM), Circuito Exterior, Ciudad Universitaria, Coyoacán, 04510 México, D.F., México (Mexico); and others
2015-09-15
Highlights: • Bismuth nanoparticles have been obtained by laser ablation of solids in liquids. • The technique allows controlling the size and concentration of the samples. • Bi np’s in base oils can improve the tribological characteristics of the lubricant. - Abstract: The improvement of the tribological properties of mineral base oils through the addition of bismuth nanoparticles as an additive, together with the idea of obtaining lubricants free of heavy metals, was evaluated. Bismuth nanoparticles were produced directly in the heavy and light viscosity mineral base oils (BS900 and BS6500) using the technique of laser ablation of solids immersed in liquids. Transmission electron microscopy measurements showed the presence of pure bismuth nanoparticles. Small Angle X-ray Scattering (SAXS) measurements showed that the average size of the nanoparticles was between 7 and 65 nm depending on the experimental conditions used. The tribological properties of the base oil with the bismuth nanoparticles additives were evaluated using a four-ball tester. Tests were performed using the base oil with and without Bi nanoparticles. It was observed that the coefficient of friction of the oil decrease with an increasing concentration of the nanoparticles. The results also showed that the wear rate was reduced when the Bi nanoparticle additives were used.
7. Photoinduced switchable wettability of bismuth coating with hierarchical dendritic structure between superhydrophobicity and superhydrophilicity
Energy Technology Data Exchange (ETDEWEB)
Su, Chunping; Lu, Zhong; Zhao, Huiping; Yang, Hao, E-mail: [email protected]; Chen, Rong, E-mail: [email protected]
2015-10-30
Graphical abstract: - Highlights: • Hierarchical bismuth nanostructures were synthesized by galvanic replacement reaction. • The bismuth coating shows superhydrophobicity after being modified by stearic acid. • Wetting transition could be realized by alternation of irradiation and modification. - Abstract: Special wettability such as superhydrophobicity and superhydrophilicity has aroused considerable attention in recent years, especially for the surface that can be switched between superhydrophobicity and superhydrophilicity. In this work, hierarchical bismuth nanostructures with hyperbranched dendritic architectures were synthesized via the galvanic replacement reaction between zinc plate and BiCl{sub 3} in ethylene glycol solution, which was composed of a trunk, branches (secondary branch), and leaves (tertiary branch). After being modified by stearic acid, the as-prepared bismuth coating shows superhydrophobicity with a high water contact angle of 164.8° and a low sliding angle of 3°. More importantly, a remarkable surface wettability transition between superhydrophobicity and superhydrophilicity could be easily realized by the alternation of UV–vis irradiation and modification with stearic acid. The tunable wetting behavior of bismuth coating could be used as smart materials to make a great application in practice.
8. Electronic Properties of Tin and Bismuth from Angular Correlation of Annihilation Photons
DEFF Research Database (Denmark)
Mogensen, O.E.; Trumpy, Georg
1969-01-01
) deformed bismuth. For both metals, the single-crystal angular-correlation curves lie near to the free-electron parabola. The tin curves show more anisotropy than the bismuth curves. An important result is the clear anisotropy found in the high-momentum part of the curves—the tails—for both metals. Little......A linear slit setup has been used to obtain results of angular-correlation measurements in (a) tin single crystals in three orientations: [001], [100], and [110], (b) bismuth single crystals in four orientations: [111], [100], [1¯10], and [2¯1¯1], (c) solid and liquid tin and bismuth, and (d...... of the liquid-metal curves are smaller and of another form than the tails of polycrystalline curves; no Gaussian with only one adjustable constant factor can give a fit to both tails. No useful method for interpreting liquid-metal angular-correlation curves seems to exist. Two deformed bismuth samples gave...
9. Characterization and re-activation of oxygen sensors for use in liquid lead-bismuth
International Nuclear Information System (INIS)
Kurata, Yuji; Abe, Yuji; Futakawa, Masatoshi; Oigawa, Hiroyuki
2010-01-01
Control of oxygen concentration in liquid lead-bismuth is one of the most important tasks to develop accelerator driven systems. In order to improve the reliability of oxygen sensors, re-activation treatments were investigated as well as characterization of oxygen sensors for use in liquid lead-bismuth. The oxygen sensor with a solid electrolyte of yttria-stabilized zirconia and a Pt/gas reference electrode showed almost the same electromotive force values in gas and liquid lead-bismuth, respectively, as the theoretical ones at temperatures above 400 deg. C or 450 deg. C. After long-term use of 6500 h, the outputs of the sensor became incorrect in liquid lead-bismuth. The state of the sensor that indicated incorrect outputs could not be recovered by cleaning with a nitric acid. However, it was found that the oxygen sensor became a correct sensor indicating theoretical values in liquid lead-bismuth after re-activation by the Pt-treatment of the outer surface of the sensor.
10. Bismuth nanoparticles synthesized by laser ablation in lubricant oils for tribological tests
International Nuclear Information System (INIS)
Flores-Castañeda, M.; Camps, E.; Camacho-López, M.; Muhl, S.
2015-01-01
Highlights: • Bismuth nanoparticles have been obtained by laser ablation of solids in liquids. • The technique allows controlling the size and concentration of the samples. • Bi np’s in base oils can improve the tribological characteristics of the lubricant. - Abstract: The improvement of the tribological properties of mineral base oils through the addition of bismuth nanoparticles as an additive, together with the idea of obtaining lubricants free of heavy metals, was evaluated. Bismuth nanoparticles were produced directly in the heavy and light viscosity mineral base oils (BS900 and BS6500) using the technique of laser ablation of solids immersed in liquids. Transmission electron microscopy measurements showed the presence of pure bismuth nanoparticles. Small Angle X-ray Scattering (SAXS) measurements showed that the average size of the nanoparticles was between 7 and 65 nm depending on the experimental conditions used. The tribological properties of the base oil with the bismuth nanoparticles additives were evaluated using a four-ball tester. Tests were performed using the base oil with and without Bi nanoparticles. It was observed that the coefficient of friction of the oil decrease with an increasing concentration of the nanoparticles. The results also showed that the wear rate was reduced when the Bi nanoparticle additives were used
11. Facile solvothermal synthesis of a graphene nanosheet-bismuth oxide composite and its electrochemical characteristics
Energy Technology Data Exchange (ETDEWEB)
Wang Huanwen [Key Laboratory of Eco-Environment-Related Polymer Materials of Ministry of Education, Key Laboratory of Polymer Materials of Gansu Province, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Hu Zhongai, E-mail: [email protected] [Key Laboratory of Eco-Environment-Related Polymer Materials of Ministry of Education, Key Laboratory of Polymer Materials of Gansu Province, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China); Chang Yanqin; Chen Yanli; Lei Ziqiang; Zhang Ziyu; Yang Yuying [Key Laboratory of Eco-Environment-Related Polymer Materials of Ministry of Education, Key Laboratory of Polymer Materials of Gansu Province, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070 (China)
2010-12-01
This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet-bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene-bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180 {sup o}C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG-DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255 F g{sup -1} (based on composite) is obtained at a specific current of 1 A g{sup -1} as compared with 71 F g{sup -1} for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757 F g{sup -1} even at 10 A g{sup -1}. In addition, the graphene nanosheet-bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility.
12. Facile solvothermal synthesis of a graphene nanosheet-bismuth oxide composite and its electrochemical characteristics
International Nuclear Information System (INIS)
Wang Huanwen; Hu Zhongai; Chang Yanqin; Chen Yanli; Lei Ziqiang; Zhang Ziyu; Yang Yuying
2010-01-01
This work demonstrates a novel and facile route for preparing graphene-based composites comprising of metal oxide nanoparticles and graphene. A graphene nanosheet-bismuth oxide composite as electrode materials of supercapacitors was firstly synthesized by thermally treating the graphene-bismuth composite, which was obtained through simultaneous solvothermal reduction of the colloidal dispersions of negatively charged graphene oxide sheets in N,N-dimethyl formamide (DMF) solution of bismuth cations at 180 o C. The morphology, composition, and microstructure of the composites together with pure graphite oxide, and graphene were characterized using powder X-ray diffraction (XRD), FT-IR, field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetry and differential thermogravimetry (TG-DTG). The electrochemical behaviors were measured by cyclic voltammogram (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). The specific capacitance of 255 F g -1 (based on composite) is obtained at a specific current of 1 A g -1 as compared with 71 F g -1 for pure graphene. The loaded-bismuth oxide achieves a specific capacitance as high as 757 F g -1 even at 10 A g -1 . In addition, the graphene nanosheet-bismuth oxide composite electrode exhibits the excellent rate capability and well reversibility.
13. Bismuth Modified Carbon-Based Electrodes for the Determination of Selected Neonicotinoid Insecticides
Directory of Open Access Journals (Sweden)
Marko Rodić
2011-05-01
Full Text Available Two types of bismuth modified electrodes, a bismuth-film modified glassy carbon (BiF-GCE and a bismuth bulk modified carbon paste, were applied for the determination of selected nitroguanidine neonicotinoid insecticides. The method based on an ex situ prepared BiF-GCE operated in the differential pulse voltammetric (DPV mode was applied to determine clothianidin in the concentration range from 2.5 to 23 μg cm−3 with a relative standard deviation (RSD not exceeding 1.5%. The tricresyl phosphate-based carbon paste electrodes (TCP-CPEs, bulk modified with 5 and 20 w/w% of bismuth, showed a different analytical performance in the determination of imidacloprid, regarding the peak shape, potential window, and noise level. The TCP-CPE with 5% Bi was advantageous, and the developed DPV method based on it allowed the determination in the concentration range from 1.7 to 60 μg cm−3 with an RSD of 2.4%. To get a deeper insight into the morphology of the bismuth-based sensor surfaces, scanning electron microscopic measurements were performed of both the surface film and the bulk modified electrodes.
14. Electrochemical study on determination of diffusivity, activity and solubility of oxygen in liquid bismuth
Energy Technology Data Exchange (ETDEWEB)
Ganesan, Rajesh [Liquid Metals and Structural Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Gnanasekaran, T. [Liquid Metals and Structural Chemistry Division, Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)]. E-mail: [email protected]; Srinivasa, Raman S. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Mumbai 400 076 (India)
2006-06-15
Diffusivity of oxygen in liquid bismuth was measured by potentiostatic method and is given bylg(D{sub O}{sup Bi}/cm{sup 2}.s{sup -1})(+/-0.042)=-3.706-1377/(TK{sup -1})(804bismuth was determined by coulometric titrations and using the measured data standard free energy of dissolution of oxygen in liquid bismuth was derived for the reaction:1/2O{sub 2}(g)=[O]{sub Bi}(at.%)and is given by{delta}G{sub O(Bi)}{sup o}/(J.g-atomO{sup -1})(+/-720)=-108784+20.356TK{sup -1}(753bismuth was derived as a function of temperature and is given by the following expressions:lg(S/at%O)(+/-0.05)=-4476/TK{sup -1}+4.05(753bismuth is compared with the literature data.
15. Crystallinity and electrical properties of neodymium-substituted bismuth titanate thin films
International Nuclear Information System (INIS)
Chen, Y.-C.; Hsiung, C.-P.; Chen, C.-Y.; Gan, J.-Y.; Sun, Y.-M.; Lin, C.-P.
2006-01-01
We report on the properties of Nd-substituted bismuth titanate Bi 4-x Nd x Ti 3 O 12 (BNdT) thin films for ferroelectric non-volatile memory applications. The Nd-substituted bismuth titanate thin films fabricated by modified chemical solution deposition technique showed much improved properties compared to pure bismuth titanate. A pyrochlore free crystalline phase was obtained at a low annealing temperature of 640 deg. C and grain size was found to be considerably increased as the annealing temperature increased. The film properties were found to be strongly dependent on the Nd content and annealing temperatures. The measured dielectric constant of BNdT thin films was in the range 172-130 for Bi 4-x Nd x Ti 3 O 12 with x 0.0-0.75. Ferroelectric properties of Nd-substituted bismuth titanate thin films were significantly improved compared to pure bismuth titanate. For example, the observed 2P r and E c for Bi 3.25 Nd 0.75 Ti 3 O 12 , annealed at 680 deg. C, were 38 μC/cm 2 and 98 kV/cm, respectively. The improved microstructural and ferroelectric properties of BNdT thin films suggest their suitability for high density ferroelectric random access memory applications
16. Emulsion liquid membrane for selective extraction of bismuth from nitrate medium
International Nuclear Information System (INIS)
Mokhtari, Bahram; Pourabdollah, Kobra
2013-01-01
The novelty of this work is the selective extraction of bismuth ions from nitrate medium by emulsion liquid membrane. Di(2-ethylhexyl)phosphoric acid was used as extractant of bismuth ions from nitrate medium by emulsion liquid membrane, and Triton X-100 was used as the biodegradable surfactant in n-pentanol n-pentanol bulk membrane. The extraction of bismuth ions was evaluated by the yield of extraction. The experimental parameters were evaluated and were optimized. They included the ratio of di(2-ethylhexyl)phosphoric acid concentration to the concentration of /Triton X-100 concentration (1.0 : 0.5% w/w), nature of diluents (n-pentanol), nature and concentration of the stripping solution (sulfuric acid, 0.5M), stirring speed (1,800 rpm) and equilibrium time of extraction (20min), initial feed solution of bismuth (350 ppm) and the volume ratio of the internal stripping phase to the membrane phase (14 times). The experimental parameters of kinetic extraction revealed that the bismuth ions were extracted at 100% 97%
17. Emulsion liquid membrane for selective extraction of bismuth from nitrate medium
Energy Technology Data Exchange (ETDEWEB)
Mokhtari, Bahram; Pourabdollah, Kobra [Islamic Azad University, Shahreza (Iran, Islamic Republic of)
2013-07-15
The novelty of this work is the selective extraction of bismuth ions from nitrate medium by emulsion liquid membrane. Di(2-ethylhexyl)phosphoric acid was used as extractant of bismuth ions from nitrate medium by emulsion liquid membrane, and Triton X-100 was used as the biodegradable surfactant in n-pentanol n-pentanol bulk membrane. The extraction of bismuth ions was evaluated by the yield of extraction. The experimental parameters were evaluated and were optimized. They included the ratio of di(2-ethylhexyl)phosphoric acid concentration to the concentration of /Triton X-100 concentration (1.0 : 0.5% w/w), nature of diluents (n-pentanol), nature and concentration of the stripping solution (sulfuric acid, 0.5M), stirring speed (1,800 rpm) and equilibrium time of extraction (20min), initial feed solution of bismuth (350 ppm) and the volume ratio of the internal stripping phase to the membrane phase (14 times). The experimental parameters of kinetic extraction revealed that the bismuth ions were extracted at 100% 97%.
18. How reliable are environmental data on 'orphan' elements? The case of bismuth concentrations in surface waters.
Science.gov (United States)
Filella, Montserrat
2010-01-01
Like all elements of the periodic table, bismuth is ubiquitously distributed throughout the environment as a result of natural processes and human activities. It is present as Bi(III) in environmental, biological and geochemical samples. Although bismuth and its compounds are considered to be non-toxic to humans, its increasing use as a replacement for lead has highlighted how little is known about its environmental and ecotoxicological behaviour. In this first critical review paper on the existing information on bismuth occurrence in natural waters, 125 papers on fresh and marine waters have been collated. Although the initial objective of this study was to establish the range of the typical concentrations of total dissolved bismuth in natural waters, this proved impossible to achieve due to the wide, and hitherto unexplained, dispersion of published data. Since analytical limitations might be one of the reasons underlying value dispersion, new analytical methods published since 2000--intended to be applied to natural waters--have also been reviewed. Disappointingly, the detection limits of the bulk of them are well above those required; they are thus of limited usefulness. Analysis of the existing information on bismuth in secondary references (i.e., books, review chapters) and on its chemical speciation in seawater revealed that the uncritical reproduction of old data is a widespread practice.
19. Recent Advances in Bismuth-Based Nanomaterials for Photoelectrochemical Water Splitting.
Science.gov (United States)
Bhat, Swetha S M; Jang, Ho Won
2017-08-10
In recent years, bismuth-based nanomaterials have drawn considerable interest as potential candidates for photoelectrochemical (PEC) water splitting owing to their narrow band gaps, nontoxicity, and low costs. The unique electronic structure of bismuth-based materials with a well-dispersed valence band comprising Bi 6s and O 2p orbitals offers a suitable band gap to harvest visible light. This Review presents significant advancements in exploiting bismuth-based nanomaterials for solar water splitting. An overview of the different strategies employed and the new ideas adopted to improve the PEC performance of bismuth-based nanomaterials are discussed. Morphology control, the construction of heterojunctions, doping, and co-catalyst loading are several approaches that are implemented to improve the efficiency of solar water splitting. Key issues are identified and guidelines are suggested to rationalize the design of efficient bismuth-based materials for sunlight-driven water splitting. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
20. Comparison of Second-Line Quadruple Therapies with or without Bismuth for Helicobacter pylori Infection
Directory of Open Access Journals (Sweden)
Guang-Hong Jheng
2015-01-01
Full Text Available The bismuth-based quadruple regimen has been applied in Helicobacter pylori rescue therapy worldwide. The non-bismuth-based quadruple therapy or “concomitant therapy” is an alternative option in first-line eradication but has not been used in second-line therapy. Discovering a valid regimen for rescue therapy in bismuth-unavailable countries is important. We conducted a randomized controlled trial to compare the efficacies of the standard quadruple therapy and a modified concomitant regimen. One hundred and twenty-four patients were randomly assigned into two groups: RBTM (rabeprozole 20 mg bid., bismuth subcitrate 120 mg qid, tetracycline 500 mg qid, and metronidazole 250 mg qid and RATM (rabeprozole 20 mg bid., amoxicillin 1 g bid., tetracycline 500 mg qid, and metronidazole 250 mg qid for 10 days. The eradication rate of the RBTM and RATM regimen was 92.1% and 90.2%, respectively, in intention-to-treat analysis. Patients in both groups had good compliance (~96%. The overall incidence of adverse events was higher in the RATM group (42.6% versus 22.2%, P=0.02, but only seven patients (11.5% experienced grades 2-3 events. In conclusion, both regimens had good efficacy, compliance, and acceptable side effects. The 10-day RATM treatment could be an alternative rescue therapy in bismuth-unavailable countries.
1. Evaluation on the characteristics of tin-silver-bismuth solder
Science.gov (United States)
Xia, Z.; Shi, Y.; Chen, Z.
2002-02-01
Tin-silver-bismuth solder is characterized by its lower melting point, good wetting behavior, and good mechanical property for which it is expected to be a new lead-free solder to replace tin-lead solder. In this article, Sn-3.33Ag-4.83Bi solder was investigated concerning its physical, spreading, and mechanical properties under specific conditions. Cooling curves and DSC results showed that it was close to eutectic composition (m.p. 210° 212 °C). Coefficiency of thermal expansion (CTE) of this solder, between that of PCBs and copper substrates, was beneficial to alleviate the thermal mismatch of the substrates. It was also a good electrical and thermal conductor. Using a rosin-based, mildly activated (RMA) flux, a spreading test indicated that SnAgBi solder paste had good solderability. Meanwhile, the solder had high tensile strength and fracture energy. Its fracture mechanism was a mixture of ductile and brittle fracture morphology. The metallographic and EDAX analyses indicated that it was composed of a tin-based solid solution and some intermetallic compound (IMC) that could strengthen the substrate. However, these large needle-like IMCs would cut the substrate and this resulted in the decreasing of the toughness of the solder.
2. Ballistic edge states in Bismuth nanowires revealed by SQUID interferometry.
Science.gov (United States)
Murani, Anil; Kasumov, Alik; Sengupta, Shamashis; Kasumov, Yu A; Volkov, V T; Khodos, I I; Brisset, F; Delagrange, Raphaëlle; Chepelianskii, Alexei; Deblock, Richard; Bouchiat, Hélène; Guéron, Sophie
2017-07-05
The protection against backscattering provided by topology is a striking property. In two-dimensional insulators, a consequence of this topological protection is the ballistic nature of the one-dimensional helical edge states. One demonstration of ballisticity is the quantized Hall conductance. Here we provide another demonstration of ballistic transport, in the way the edge states carry a supercurrent. The system we have investigated is a micrometre-long monocrystalline bismuth nanowire with topological surfaces, that we connect to two superconducting electrodes. We have measured the relation between the Josephson current flowing through the nanowire and the superconducting phase difference at its ends, the current-phase relation. The sharp sawtooth-shaped phase-modulated current-phase relation we find demonstrates that transport occurs selectively along two ballistic edges of the nanowire. In addition, we show that a magnetic field induces 0-π transitions and ϕ 0 -junction behaviour, providing a way to manipulate the phase of the supercurrent-carrying edge states and generate spin supercurrents.
3. On the use of bismuth as a neutron filter
CERN Document Server
2003-01-01
A formula is given which, for neutron energies in the range 10 sup - sup 4 bismuth temperature and crystalline form. Computer programs have been developed which allow calculations for the Bi rhombohedral structure in its poly-crystalline form and its equivalent hexagonal close-packed structure. The calculated total neutron cross-sections for poly-crystalline Bi at different temperatures were compared with the measured values. An overall agreement is indicated between the formula fits and experimental data. Agreement was also obtained for values of Bi-single crystals, at room and liquid nitrogen temperatures. A feasibility study for use of Bi in powdered form, as a cold neutron filter, is detailed in terms of the optimum Bi-single crystal thickness, mosaic spread, temperature and cutting plane for efficient transmission of thermal-reactor neutrons, and also for rejection of the accom...
4. On the use of bismuth as a neutron filter
Science.gov (United States)
2003-02-01
A formula is given which, for neutron energies in the range 10 -4< E<10 eV, permits calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of bismuth temperature and crystalline form. Computer programs have been developed which allow calculations for the Bi rhombohedral structure in its poly-crystalline form and its equivalent hexagonal close-packed structure. The calculated total neutron cross-sections for poly-crystalline Bi at different temperatures were compared with the measured values. An overall agreement is indicated between the formula fits and experimental data. Agreement was also obtained for values of Bi-single crystals, at room and liquid nitrogen temperatures. A feasibility study for use of Bi in powdered form, as a cold neutron filter, is detailed in terms of the optimum Bi-single crystal thickness, mosaic spread, temperature and cutting plane for efficient transmission of thermal-reactor neutrons, and also for rejection of the accompanying fast neutrons and gamma rays.
5. On the use of bismuth as a neutron filter
Energy Technology Data Exchange (ETDEWEB)
Adib, M.; Kilany, M. E-mail: [email protected]
2003-02-01
A formula is given which, for neutron energies in the range 10{sup -4}bismuth temperature and crystalline form. Computer programs have been developed which allow calculations for the Bi rhombohedral structure in its poly-crystalline form and its equivalent hexagonal close-packed structure. The calculated total neutron cross-sections for poly-crystalline Bi at different temperatures were compared with the measured values. An overall agreement is indicated between the formula fits and experimental data. Agreement was also obtained for values of Bi-single crystals, at room and liquid nitrogen temperatures. A feasibility study for use of Bi in powdered form, as a cold neutron filter, is detailed in terms of the optimum Bi-single crystal thickness, mosaic spread, temperature and cutting plane for efficient transmission of thermal-reactor neutrons, and also for rejection of the accompanying fast neutrons and gamma rays.
6. On the use of bismuth as a neutron filter
International Nuclear Information System (INIS)
2003-01-01
A formula is given which, for neutron energies in the range 10 -4 < E<10 eV, permits calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of bismuth temperature and crystalline form. Computer programs have been developed which allow calculations for the Bi rhombohedral structure in its poly-crystalline form and its equivalent hexagonal close-packed structure. The calculated total neutron cross-sections for poly-crystalline Bi at different temperatures were compared with the measured values. An overall agreement is indicated between the formula fits and experimental data. Agreement was also obtained for values of Bi-single crystals, at room and liquid nitrogen temperatures. A feasibility study for use of Bi in powdered form, as a cold neutron filter, is detailed in terms of the optimum Bi-single crystal thickness, mosaic spread, temperature and cutting plane for efficient transmission of thermal-reactor neutrons, and also for rejection of the accompanying fast neutrons and gamma rays
International Nuclear Information System (INIS)
Dzodzo, M.; Cuckovic-Dzodzo, D.
2001-01-01
The design of liquid metal reactors such as Encapsulated Nuclear Heat Source (ENHS) which are based predominantly on the flow generated by natural convection effects demands knowledge of velocity and temperature fields, distribution of the local Nusselt numbers and values of the average Nusselt numbers for small coolant velocity regimes. Laminar natural convection in rectangular enclosures with different aspect ratios, containing lead-bismuth and lead is studied numerically in this paper. The numerical model takes into account variable properties of the liquid metals. The developed correlation for average Nusselt numbers is presented. It is concluded that average Nusselt numbers are lower than in 'normal' fluids (air, water and glycerol) for the same values of Rayleigh numbers. However, the heat flux, which can be achieved, is greater due to the high thermal conductivity of liquid metals. Some specific features of the flow fields generated by natural convection in liquid metals are presented. Their consequences on the design of heat exchangers for liquid metals are discussed. An application of the obtained results to the design of a new type of steam generator, which integrates the intermediate heat exchanger and secondary pool functions of the ENHS reactor, is presented. (authors)
8. Antibacterial effect of bismuth subsalicylate nanoparticles synthesized by laser ablation
International Nuclear Information System (INIS)
Flores-Castañeda, Mariela; Vega-Jiménez, Alejandro L.; Almaguer-Flores, Argelia; Camps, Enrique; Pérez, Mario; Silva-Bermudez, Phaedra; Berea, Edgardo; Rodil, Sandra E.
2015-01-01
The antimicrobial properties of bismuth subsalicylate (BSS) nanoparticles against four opportunistic pathogens; E. coli, P. aeruginosa, S. aureus, and S. epidermidis were determined. BSS nanoparticles were synthesized by pulse laser ablation of a solid target in distilled water under different conditions. The nanoparticles were characterized using high-resolution transmission electron microscopy and absorption spectra and small angle X-ray scattering. The analysis shows that the colloids maintained the BSS structure and presented average particle size between 20 and 60 nm, while the concentration ranges from 95 to 195 mg/L. The antibacterial effect was reported as the inhibition ratio of the bacterial growth after 24 h and the cell viability was measured using the XTT assay. The results showed that the inhibition ratio of E. coli and S. epidermidis was dependant on the NPs size and/or concentration, meanwhile P. aeruginosa and S. aureus were more sensitive to the BSS nanoparticles independently of both the size and the concentration. In general, the BSS colloids with average particle size of 20 nm were the most effective, attaining inhibition ratios >80 %, similar or larger than those obtained with the antibiotic used as control. The results suggest that the BSS colloids could be used as effective antibacterial agents with potential applications in the medical area
9. Possible superconductivity in the Bismuth IV solid phase under pressure.
Science.gov (United States)
2018-04-13
The first successful theory of superconductivity was the one proposed by Bardeen, Cooper and Schrieffer in 1957. This breakthrough fostered a remarkable growth of the field that propitiated progress and questionings, generating alternative theories to explain specific phenomena. For example, it has been argued that Bismuth, being a semimetal with a low number of carriers, does not comply with the basic hypotheses underlying BCS and therefore a different approach should be considered. Nevertheless, in 2016 based on BCS we put forth a prediction that Bi at ambient pressure becomes a superconductor at 1.3 mK. A year later an experimental group corroborated that in fact Bi is a superconductor with a transition temperature of 0.53 mK, a result that eluded previous work. So, since Bi is superconductive in almost all the different structures and phases, the question is why Bi-IV has been elusive and has not been found yet to superconduct? Here we present a study of the electronic and vibrational properties of Bi-IV and infer its possible superconductivity using a BCS approach. We predict that if the Bi-IV phase structure were cooled down to liquid helium temperatures it would also superconduct at a T c of 4.25 K.
10. Optical bleaching of bismuth implanted silica glass: A threshold effect
International Nuclear Information System (INIS)
Park, S.Y.; Magruder, R.H. III; Weeks, R.A.
1992-01-01
The near surface regions of high purity silica glass discs, Spectrosil A, were modified by implantation with bismuth ions at 160 key and room temperature. The glasses implanted with a nominal dose of 6x10 16 Bi/cm 2 at ∼5 μA/cm 2 were subsequently bleached with a 5.0 eV KrF pulsed excimer laser. The laser had an average pulse duration of ∼20 ns and repetition rate of 10 Hz. It was found that the bleaching was dependent upon the power density of the laser for a constant total integrated energy. Ion backscattering and optical absorption measurements were made before and after laser irradiation. Large changes in optical density and depth distribution of the implanted ions were observed at power densities of ≥45 mJ/cm 2 -pulse. Onset of threshold for bleaching of silica glass implanted with 6x10 16 Bi/cm 2 at 160 key and at room temperature is between 30 and 45 mJ/cm 2 -pulse
11. Bismuth alloying properties in GaAs nanowires
Energy Technology Data Exchange (ETDEWEB)
Ding, Lu [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, PO Box 72, Beijing 100876 (China); Lu, Pengfei, E-mail: [email protected] [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, PO Box 72, Beijing 100876 (China); Cao, Huawei; Cai, Ningning; Yu, Zhongyuan [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, PO Box 72, Beijing 100876 (China); Gao, Tao [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Wang, Shumin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg (Sweden)
2013-09-15
First-principles calculations have been performed to investigate the structural, electronic and optical properties of bismuth alloying in GaAs nanowires. A typical model of Ga{sub 31}As{sub 31} nanowires is introduced for its reasonable band gap. The band gap of GaAs{sub 1−x}Bi{sub x} shrinks clearly with the increasing Bi concentration and the band edge shifts when spin–orbit coupling (SOC) is considered. The insertion of Bi atom leads to hybridization of Ga/As/Bi p states which contributes a lot around Fermi level. Scissor effect is involved. The optical properties are presented, including dielectric function, optical absorption spectra and reflectivity, which are also varied with the increasing of Bi concentrations. - Graphical abstract: Top view of Bi-doped GaAs nanowires. Ga, As, and Bi atoms are denoted with grey, purple and red balls, respectively. Display Omitted - Highlights: • A typical model of Ga{sub 31}As{sub 31} nanowires is introduced for its reasonable band gap. • The band gap of GaAs{sub 1−x}Bi{sub x} shrinks clearly with the increasing Bi concentration. • The band edge shifts when spin–orbit coupling (SOC) is considered. • The insertion of Bi atom leads to hybridization of Ga/As/Bi p states.
12. Antibacterial effect of bismuth subsalicylate nanoparticles synthesized by laser ablation
Science.gov (United States)
Flores-Castañeda, Mariela; Vega-Jiménez, Alejandro L.; Almaguer-Flores, Argelia; Camps, Enrique; Pérez, Mario; Silva-Bermudez, Phaedra; Berea, Edgardo; Rodil, Sandra E.
2015-11-01
The antimicrobial properties of bismuth subsalicylate (BSS) nanoparticles against four opportunistic pathogens; E. coli, P. aeruginosa, S. aureus, and S. epidermidis were determined. BSS nanoparticles were synthesized by pulse laser ablation of a solid target in distilled water under different conditions. The nanoparticles were characterized using high-resolution transmission electron microscopy and absorption spectra and small angle X-ray scattering. The analysis shows that the colloids maintained the BSS structure and presented average particle size between 20 and 60 nm, while the concentration ranges from 95 to 195 mg/L. The antibacterial effect was reported as the inhibition ratio of the bacterial growth after 24 h and the cell viability was measured using the XTT assay. The results showed that the inhibition ratio of E. coli and S. epidermidis was dependant on the NPs size and/or concentration, meanwhile P. aeruginosa and S. aureus were more sensitive to the BSS nanoparticles independently of both the size and the concentration. In general, the BSS colloids with average particle size of 20 nm were the most effective, attaining inhibition ratios >80 %, similar or larger than those obtained with the antibiotic used as control. The results suggest that the BSS colloids could be used as effective antibacterial agents with potential applications in the medical area.
13. Synthesis and characterization of bismuth zinc niobate pyrochlore nanopowders
Directory of Open Access Journals (Sweden)
Sonia Maria Zanetti
2007-09-01
Full Text Available Bismuth zinc niobate pyrochlores Bi1.5ZnNb1.5O7 (alpha-BZN, and Bi2(Zn1/3Nb2/32O 7 (beta-BZN have been synthesized by chemical method based on the polymeric precursors. The pyrochlore phase was investigated by differential scanning calorimetry, infrared spectroscopy, and X ray diffraction. Powder and sintered pellets morphology was examined by scanning electron microscopy. The study of alpha-BZN phase formation reveals that, at 500 °C, the pyrochlore phase was already present while a single-phased nanopowder was obtained after calcination at 700 °C. The crystallization mechanism of the beta-BZN is quite different, occurring through the crystallization of alpha-BZN and BiNbO4 intermediary phases. Both compositions yielded soft agglomerated powders. alpha-BZN pellets, sintered at 800 °C for 2 hours, presented a relative density of 97.3% while those of beta-BZN, sintered at 900 °C for 2 hours, reached only 91.8%. Dielectric constant and dielectric loss, measured at 1 MHz, were 150 and 4 x/10-4 for a-BZN, and 97 and 8 x 10-4 for beta-BZN.
14. Structure, spectra and stability of solid bismuth carbonates
International Nuclear Information System (INIS)
Taylor, Peter; Sunder, S.; Lopata, V.J.
1984-01-01
A previously unreported basic bismuth carbonate, (BiO)sub(4)(OH)sub(2)COsub(3), has been identified as an intermediate product in the interconversion of α-Bisub(2)Osub(3) and synthetic bismutite, (BiO)sub(2)COsub(3), in aqueous carbonate solutions. It has a narrow stability field between COsub(2) partial pressures of 10sup(-5.5+-1.0) Pa, in the presence of dilute aqueous solution at 25 degrees C. Gibbs energies of formation, calculated from these partial pressures, are Δsub(f)Gsup(0)((BiO)sub(4)(OH)sub(2)COsub(3),s,298.15 K)-1678 +- 9 kJ molsup(-1) and Δsub(f)Gsup(0)((BiO)sub(2)COsub(3),s,298.15 K)=-945 +- 7 kJ molsup(-1). The two carbonates have been compared by thermogravimetric analysis, X-ray powder diffractometry, and infrared and Raman spectroscopy. The unit cell of (BiO)sub(4)(OH)sub(2)COsub(3) is dimensionally orthorhombic, with a=10.772(1), b=5.4898(5), c=14.757(1)angstrom,Z=4, but its true symmetry is probably triclinic. A structural model for (BiO)sub(4)(OH)sub(2)COsub(3), and two modified models for (BiO)sub(2)COsub(3), are proposed. The possible natural occurrence of (BiO)sub(4)(OH)sub(2)COsub(3) is discussed
15. Modular Lead-Bismuth Fast Reactors in Nuclear Power
Directory of Open Access Journals (Sweden)
2012-09-01
Full Text Available On the basis of the unique experience of operating reactors with heavy liquid metal coolant–eutectic lead-bismuth alloy in nuclear submarines, the concept of modular small fast reactors SVBR-100 for civilian nuclear power has been developed and validated. The features of this innovative technology are as follows: a monoblock (integral design of the reactor with fast neutron spectrum, which can operate using different types of fuel in various fuel cycles including MOX fuel in a self-providing mode. The reactor is distinct in that it has a high level of self-protection and passive safety, it is factory manufactured and the assembled reactor can be transported by railway. Multipurpose application of the reactor is presumed, primarily, it can be used for regional power to produce electricity, heat and for water desalination. The Project is being realized within the framework of state-private partnership with joint venture OJSC “AKME-Engineering” established on a parity basis by the State Atomic Energy Corporation “Rosatom” and the Limited Liability Company “EuroSibEnergo”.
16. Antibacterial effect of bismuth subsalicylate nanoparticles synthesized by laser ablation
Energy Technology Data Exchange (ETDEWEB)
Flores-Castañeda, Mariela [Instituto Nacional de Investigaciones Nucleares (Mexico); Vega-Jiménez, Alejandro L., E-mail: [email protected]; Almaguer-Flores, Argelia [Universidad Nacional Autónoma de México, Facultad de Odontología, DEPeI, I (Mexico); Camps, Enrique; Pérez, Mario [Instituto Nacional de Investigaciones Nucleares (Mexico); Silva-Bermudez, Phaedra [Instituto Nacional de Rehabilitación, Unidad de Ingeniería de Tejidos, Terapia Celular y Medicina Regenerativa (Mexico); Berea, Edgardo [FarmaQuimia SA de CV. (Mexico); Rodil, Sandra E. [Universidad Nacional Autónoma de México, Instituto de Investigaciones en Materiales (Mexico)
2015-11-15
The antimicrobial properties of bismuth subsalicylate (BSS) nanoparticles against four opportunistic pathogens; E. coli, P. aeruginosa, S. aureus, and S. epidermidis were determined. BSS nanoparticles were synthesized by pulse laser ablation of a solid target in distilled water under different conditions. The nanoparticles were characterized using high-resolution transmission electron microscopy and absorption spectra and small angle X-ray scattering. The analysis shows that the colloids maintained the BSS structure and presented average particle size between 20 and 60 nm, while the concentration ranges from 95 to 195 mg/L. The antibacterial effect was reported as the inhibition ratio of the bacterial growth after 24 h and the cell viability was measured using the XTT assay. The results showed that the inhibition ratio of E. coli and S. epidermidis was dependant on the NPs size and/or concentration, meanwhile P. aeruginosa and S. aureus were more sensitive to the BSS nanoparticles independently of both the size and the concentration. In general, the BSS colloids with average particle size of 20 nm were the most effective, attaining inhibition ratios >80 %, similar or larger than those obtained with the antibiotic used as control. The results suggest that the BSS colloids could be used as effective antibacterial agents with potential applications in the medical area.
17. Superconductivity in the unconventional high pressure phase bismuth-III
Energy Technology Data Exchange (ETDEWEB)
Semeniuk, Konstantin; Brown, Philip; Vasiljkovic, Aleksandar; Grosche, Malte [University of Cambridge (United Kingdom)
2015-07-01
One of the most surprising developments in high pressure research was the realisation that many elements assume very unexpected high pressure structures, described in terms of extremely large or even infinite unit cells. Elemental bismuth, which has been known to undergo a series of pressure induced structural transitions between 25 kbar and 80 kbar, is an interesting example: the intermediate pressure Bi-III phase has a complex 'host-guest' structure consisting of two incommensurate sublattices. Since the unit cell is infinitely large, the description of electronic and lattice excitations is problematic. Apart from its metallic character and the observation of superconductivity at low temperature, little is known about the electronic structure in this phase. We investigate the electrical resistivity within the metallic Bi-III phase under high hydrostatic pressure and in applied magnetic field using a piston cylinder cell. Superconductivity is observed below 7.1 K, and we extract the temperature dependence of the upper critical field, which exceeds 2 T at low temperature. The normal state resistivity exhibits an approximately linear temperature dependence. This could be attributed to strong scattering from low-lying excitations, as caused by an unusually soft phonon spectrum. The results suggest that strong coupling superconductivity arises within the host-guest structure of Bi-III out of an unusual electronic state.
18. MEXICO loop provides essential technology for MYRRHA. SCK•CEN investigates the chemistry of lead-bismuth
International Nuclear Information System (INIS)
2014-01-01
In the MYRRHA facility, Lead-Bismuth Eutectic (LBE) alloy will act as the primary coolant. There are different experimental lead-bismuth loops in the world. Most have been designed to study steel corrosion in LBE or the thermohydraulics of LBE. The article discusses the MEXICO test loop, which has been developed by SCK-CEN to investigate the chemistry of leadbismuth.
19. The safety and efficacy of ranitidine bismuth citrate in combination with antibiotics for the eradication of Helicobacter pylori
NARCIS (Netherlands)
Wyeth, J. W.; Pounder, R. E.; Duggan, A. E.; O'Morain, C. A.; Schaufelberger, H. D.; de Koster, E. H.; Rauws, E. A.; Bardhan, K. D.; Gilvarry, J.; Buckley, M. J.; Gummett, P. A.; Logan, R. P.
1996-01-01
Ranitidine bismuth citrate is a novel salt of ranitidine and a bismuth citrate complex. It has intrinsic antisecretory and anti-Helicobacter pylori activity, but monotherapy rarely eradicates H. pylori infection in man. A pilot study to investigate rates of H. pylori eradication achieved by
20. The influence of metronidazole resistance on the efficacy of ranitidine bismuth citrate triple therapy regimens for Helicobacter pylori infection
NARCIS (Netherlands)
Van der Wouden, EJ; Thijs, JC; Van Zwet, AA; Kooy, A; Kleibeuker, JH
Aim: To assess the influence of metronidazole resistance on the efficacy of ranitidine bismuth citrate-based triple therapy regimens in two consecutive studies. Methods: In the first study, patients with a culture-proven Helicobacter pylori infection were treated with ranitidine bismuth citrate 400
1. The effect of lanthanum boride on the sintering, sintered microstructure and mechanical properties of titanium and titanium alloys
Energy Technology Data Exchange (ETDEWEB)
Yang, Y.F. [RMIT University, Centre for Additive Manufacturing, School of Aerospace, Mechanical and Manufacturing Engineering, GPO Box 2476, Melbourne VIC 3001 (Australia); Luo, S.D. [The University of Queensland, School of Mechanical and Mining Engineering, Brisbane, QLD 4072 (Australia); Qian, M., E-mail: [email protected] [RMIT University, Centre for Additive Manufacturing, School of Aerospace, Mechanical and Manufacturing Engineering, GPO Box 2476, Melbourne VIC 3001 (Australia)
2014-11-17
An addition of ≤0.5 wt% lanthanum boride (LaB{sub 6}) to powder metallurgy commercially pure Ti (CP-Ti), Ti–6Al–4V and Ti–10V–2Fe–3Al (all in wt%) resulted in improved sintered density, substantial microstructural refinement, and noticeably increased tensile elongation. The addition of LaB{sub 6} led to scavenging of both oxygen (O) and chlorine (Cl) from the titanium powder during sintering, evidenced by the formation of La{sub 2}O{sub 3} and LaCl{sub x}O{sub y}. The pinning effect of La{sub 2}O{sub 3}, LaCl{sub x}O{sub y} and TiB inhibited prior-β grain growth and resulted in subsequent smaller α-laths. The formation of nearly equiaxed α-Ti phase is partially attributed to the nucleation effect of α-Ti on TiB. The improved sintered density was caused by B from LaB{sub 6} rather than La, while excessive formation of La{sub 2}O{sub 3} and TiB with an addition of >0.5 wt% LaB{sub 6} resulted in a noticeable decrease in sintered density. The improved tensile elongation with an addition of ≤0.5 wt% LaB{sub 6} was mainly attributed to the scavenging of oxygen by LaB{sub 6}, partially assisted by the improved sintered density. However, an addition of >0.5 wt% LaB{sub 6} led to the formation of large La{sub 2}O{sub 3} aggregates and more brittle TiB whiskers and therefore decreased tensile elongation. Balanced scavenging of O is thus important. The optimal addition of LaB{sub 6} was 0.5 wt% but this may change depending on the powder size of the LaB{sub 6} to be used.
2. Fabrication of crystal-oriented barium-bismuth titanate ceramics in high magnetic field and subsequent reaction sintering
International Nuclear Information System (INIS)
Tanaka, Satoshi; Tomita, Yusuke; Furushima, Ryoichi; Uematsu, Keizo; Shimizu, Hiroyuki; Doshida, Yutaka
2009-01-01
High magnetic field was applied to fabricate novel lead-free piezoelectric ceramics with a textured structure. A compact of crystallographically oriented grains was prepared by dry forming in a high magnetic field from a mixed slurry of bismuth titanate and barium titanate powders. Bismuth titanate particles with a size of about 1 μ m were used as the host material. In the forming process, the slurry was poured into a mold and set in a magnetic field of 10 T until completely dried. Bismuth titanate particles were highly oriented in the slurry under the magnetic field. The dried powder compact consisted of highly oriented bismuth titanate particles and randomly oriented barium titanate particles. Barium bismuth titanate ceramics with a- and b-axis orientations were successfully produced from the dried compact by sintering at temperatures above 1100 deg. C.
3. Overview of the use of ATHENA for thermal-hydraulic analysis of systems with lead-bismuth coolant
International Nuclear Information System (INIS)
Davis, C.B.; Shieh, A. S.
2000-01-01
The INEEL and MIT are investigating the suitability of lead-bismuth cooled fast reactor for producing low-cost electricity as well as for actinide burning. This paper is concerned with the general area of thermal-hydraulics of lead-bismuth cooled reactors. The ATHENA code is being used in the thermal-hydraulic design and analysis of lead-bismuth cooled reactors. The ATHENA code was reviewed to determine its applicability for simulating lead-bismuth cooled reactors. Two modifications were made to the code as a result of this review. Specifically, a correlation to represent heat transfer from rod bundles to a liquid metal and a void correlation based on data taken in a mixture of lead-bismuth and steam were added the code. The paper also summarizes the analytical work that is being performed with the code and plans for future analytical work
4. Overview of the Use of ATHENA for Thermal-Hydraulic Analysis of Systems with Lead-Bismuth Coolant
Energy Technology Data Exchange (ETDEWEB)
Davis, Cliff Bybee; Shieh, Arthur Shan Luk
2000-04-01
The INEEL and MIT are investigating the suitability of lead-bismuth cooled fast reactor for producing low-cost electricity as well as for actinide burning. This paper is concerned with the general area of thermal-hydraulics of lead-bismuth cooled reactors. The ATHENA code is being used in the thermal-hydraulic design and analysis of lead-bismuth cooled reactors. The ATHENA code was reviewed to determine its applicability for simulating lead-bismuth cooled reactors. Two modifications were made to the code as a result of this review. Specifically, a correlation to represent heat transfer from rod bundles to a liquid metal and a void correlation based on data taken in a mixture of lead-bismuth and steam were added the code. The paper also summarizes the analytical work that is being performed with the code and plans for future analytical work.
5. Synthesis of binary bismuth-cadmium oxide nanorods with sensitive electrochemical sensing performance
International Nuclear Information System (INIS)
Wen, Yong; Pei, Lizhai; Wei, Tian
2017-01-01
Binary bismuth-cadmium oxide nanorods have been synthesized by a simple hydrothermal process without templates and additives. X-ray diffraction and high-resolution transmission electron microscopy reveal that the nanorods possess single crystalline tetragonal Bi 2 CdO 4 phase. Scanning electron microscopy and transmission electron microscopy images show that the length and diameter of the nanorods are 20-300 nm and 5-10 μm, respectively. The formation of the binary bismuth-cadmium oxide nanorods is closely related to the hydrothermal parameters. The electrochemical sensing performance of the binary bismuth-cadmium oxide nanorods has been investigated using the nanorods as glassy carbon electrode modifiers. The detection limit is 0.19 μM with a linear range of 0.0005-2 mM. The nanorod-modified glassy carbon electrode exhibits good electrocatalytic activity toward L-cysteine and great application potential for electrochemical sensors.
International Nuclear Information System (INIS)
Hughes, M.; Suzuki, T.; Ohishi, Y.
2008-01-01
We fabricated a series of glasses with the composition 94.7-χGeO 2 -5Al 2 O 3 -0.3Bi 2 O 3 -χPbO (χ=0-24 mol. %). Characteristic absorption bands of bismuth centered at 500, 700, 800, and 1000 nm were observed. Adding PbO was found to decrease the strength of bismuth absorption. The addition of 3%-4% PbO resulted in a 50% increase in lifetime, a 20-fold increase in quantum efficiency, and a 28-fold increase in the product of emission cross section and lifetime on the 0% PbO composition. We propose that the 800 nm absorption band relates a different bismuth center than the other absorption bands
7. Potentiation of the action of metronidazole on Helicobacter pylori by omeprazole and bismuth subcitrate
DEFF Research Database (Denmark)
Andersen, L P; Colding, H; Kristiansen, J E
2000-01-01
test (Etest). With 0.5 MIC of either of the two drugs, the susceptibility of all H. pylori4 mg/l) reverted to being metronidazole sensitive. These results suggested that either bismuth salts or proton pump inhibitors may be effective in the treatment of some infections with metronidazole-resistant H...... to regimens that include proton pump inhibitors. In the present study, the synergistic effect of subinhibitory concentrations (0.25-0.5 MIC) of either bismuth subcitrate or omeprazole with metronidazole on the susceptibility of 42 H. pylori strains was investigated by agar dilution method and the Epsilometer......Treatment failures using triple therapy that include metronidazole, are common in patients infected with metronidazole-resistant Helicobacter pylori in the gastric mucosa. Higher eradication rates in such patients have been described when treatment regimens include bismuth salts compared...
International Nuclear Information System (INIS)
Miura, T.; Obara, T.; Sekimoto, H.
2004-01-01
After neutron capture, bismuth-209 changes to polonium-210 that emits α-particles. Lead-Bismuth eutectic (LBE) in reactor system contaminates the system by polonium. We analyzed adsorbed materials from melted LBE on quartz glass plate. Lead, bismuth and their oxides were confirmed in adsorbed materials. And, we evaluated the baking method in vacuum for removal of polonium and adsorbed materials on quartz glass plate. It was evaluated that it is possible to remove almost all the polonium from the quartz glass plate by baking at temperature more than 300 C. degrees. Unfolding method was applied to calculate polonium distribution in LBE ingot. From measured α-particle pulse height distribution, the polonium distribution in depth of LBE ingot was calculated using quadratic programming code, where response functions are calculated by Monte Carlo method. (authors)
9. Synthesis of Bismuth Stannate Nanoparticles with High Photocatalytic Activity under the Visible Light Irradiation
Directory of Open Access Journals (Sweden)
G. Gnanamoorthy
2017-06-01
Full Text Available Malachite Green is one of the most important organic dye, it contains triphenylmethane groups and it has been widely used for many industries. The hazardous dyes were rapidly act on immune and reproductive systems with carcinogenic effect of human health. Different methods were used for the hazardous removal in various industries, such as photocatalysis, biological treatment and adsorption process. The bismuth stannate nanoparticles have special properties of the hydrogen storage, biomolecule detection, gas sensors and catalysis. The bismuth stannate nanoparticles can be used for the degradation of organic pollutants and bismuth stannate is an important ternary oxide semiconductor with a wide band gap material. The composites were synthesized by a hydrothermal method, the obtained product was characterized by XRD, Raman, the morphology structure was confirmed by scanning electron microscopy and optical properties were carried out by DRS-UV-Vis spectroscopy. The excellent photocatalytic performance of the catalyst was evaluated by malachite green under the visible light.
10. Synthesis of binary bismuth-cadmium oxide nanorods with sensitive electrochemical sensing performance
Energy Technology Data Exchange (ETDEWEB)
Wen, Yong [Xinjiang Univ., Xinjiang (China). School of Civil Engineering and Architecture; Pei, Lizhai; Wei, Tian [Anhui Univ. of Technology, Anhui (China). School of Materials Science and Engineering
2017-07-15
Binary bismuth-cadmium oxide nanorods have been synthesized by a simple hydrothermal process without templates and additives. X-ray diffraction and high-resolution transmission electron microscopy reveal that the nanorods possess single crystalline tetragonal Bi{sub 2}CdO{sub 4} phase. Scanning electron microscopy and transmission electron microscopy images show that the length and diameter of the nanorods are 20-300 nm and 5-10 μm, respectively. The formation of the binary bismuth-cadmium oxide nanorods is closely related to the hydrothermal parameters. The electrochemical sensing performance of the binary bismuth-cadmium oxide nanorods has been investigated using the nanorods as glassy carbon electrode modifiers. The detection limit is 0.19 μM with a linear range of 0.0005-2 mM. The nanorod-modified glassy carbon electrode exhibits good electrocatalytic activity toward L-cysteine and great application potential for electrochemical sensors.
11. Bismuth- and lithium-loaded plastic scintillators for gamma and neutron detection
International Nuclear Information System (INIS)
Cherepy, Nerine J.; Sanner, Robert D.; Beck, Patrick R.; Swanberg, Erik L.; Tillotson, Thomas M.; Payne, Stephen A.; Hurlbut, Charles R.
2015-01-01
Transparent plastic scintillators based on polyvinyltoluene (PVT) have been fabricated with high loading of bismuth carboxylates for gamma spectroscopy, and with lithium carboxylates for neutron detection. When activated with a combination of standard fluors, 2,5-diphenyloxazole (PPO) and tetraphenylbutadiene (TPB), gamma light yields with 15 wt% bismuth tripivalate of 5000 Ph/MeV are measured. A PVT plastic formulation including 30 wt% lithium pivalate and 30 wt% PPO offers both pulse shape discrimination, and a neutron capture peak at ~400 keVee. In another configuration, a bismuth-loaded PVT plastic is coated with ZnS( 6 Li) paint, permitting simultaneous gamma and neutron detection via pulse shape discrimination with a figure-of-merit of 3.8, while offering gamma spectroscopy with energy resolution of R(662 keV)=15%
12. Study of magnesium bismuth alloys with a composition close to Mg3Bi2
International Nuclear Information System (INIS)
Tournier, Jean
1964-01-01
The author reports the study of magnesium-bismuth alloys with a high bismuth content. These alloys were aimed to be irradiated in a pile at a temperature of about 300 C, and thus had specific requirements regarding their bismuth content, a high density, a high fusion point with also a pressure strength constraint. The author first reports the determination of an alloy grade which could meet these requirements, and then reports issues related to their elaboration by performing optical micrography and X ray analysis in order to investigate their homogeneity. Then, the alloy hot compression strength has been assessed under significantly higher constraining conditions. Fusion point and density have also been measured. As a fast alloy degradation has been noticed, brief corrosion tests have been performed
13. Optical properties of thermally reduced bismuth-doped sodium aluminosilicate glasses
DEFF Research Database (Denmark)
Nielsen, K.H.; Smedskjær, Morten Mattrup; Yue, Yuanzheng
Heat-treatment of multivalent ion containing glasses in a hydrogen atmosphere may cause both reduction of the multivalent ions and ionic inward diffusion, resulting in improved glass properties. Bismuth-doped glasses are also interesting objects not only concerning the reduction induced diffusion...... pressure of hydrogen. Here, we present results on the effect of the heat-treatment on the optical properties of bismuth-doped sodium aluminosilicate glasses.......Heat-treatment of multivalent ion containing glasses in a hydrogen atmosphere may cause both reduction of the multivalent ions and ionic inward diffusion, resulting in improved glass properties. Bismuth-doped glasses are also interesting objects not only concerning the reduction induced diffusion...
14. Peculiarities of the interaction of indium-tin and indium-bismuth alloys with ammonium halides
International Nuclear Information System (INIS)
Red'kin, A.N.; Smirnov, V.A.; Sokolova, E.A.; Makovej, Z.I.; Telegin, G.F.
1990-01-01
Peculiarities of fusible metal alloys interaction with ammonium halogenides in vertical reactor are considered using indium-tin and indium-bismuth binary alloys. It is shown that at the end of the process the composition of metal and salt phases is determined by the equilibrium type and constant characteristic of the given salt-metal system. As a result the interaction of indium-tin and indium-bismuth alloys with ammonium halogenides leads to preferential halogenation of indium-bismuth alloys with ammonium halogenides leads to preferential halogenation of indium which may be used in the processes of separation or purification. A model is suggested to calculate the final concentration of salt and metal phase components
15. Evaluation of the gamma radiation shielding parameters of bismuth modified quaternary glass system
Science.gov (United States)
Kaur, Parminder; Singh, K. J.; Thakur, Sonika
2018-05-01
Glasses modified with heavy metal oxides (HMO) are an interesting area of research in the field of gamma-ray shielding. Bismuth modified lithium-zinc-borate glasses have been studied whereby bismuth oxide is added from 0 to 50 mol%. The gamma ray shielding properties of the glasses were evaluated at photon energy 662 keV with the help of XMuDat computer program by using the Hubbell and Seltzer database. Various gamma ray shielding parameters such as attenuation coefficient, shield thickness in terms of half and tenth value layer, effective atomic number have been studied in this work. A useful comparison of this glass system has been made with standard radiation shielding concretes viz. ordinary, barite and iron concrete. The glass samples containing 20 to 50 mol% bismuth oxide have shown better gamma ray shielding properties and hence have the potential to become good radiation absorbers.
16. Bismuth Passivation Technique for High-Resolution X-Ray Detectors
Science.gov (United States)
Chervenak, James; Hess, Larry
2013-01-01
The Athena-plus team requires X-ray sensors with energy resolution of better than one part in 3,000 at 6 keV X-rays. While bismuth is an excellent material for high X-ray stopping power and low heat capacity (for large signal when an X-ray is stopped by the absorber), oxidation of the bismuth surface can lead to electron traps and other effects that degrade the energy resolution. Bismuth oxide reduction and nitride passivation techniques analogous to those used in indium passivation are being applied in a new technique. The technique will enable improved energy resolution and resistance to aging in bismuth-absorber-coupled X-ray sensors. Elemental bismuth is lithographically integrated into X-ray detector circuits. It encounters several steps where the Bi oxidizes. The technology discussed here will remove oxide from the surface of the Bi and replace it with nitridized surface. Removal of the native oxide and passivating to prevent the growth of the oxide will improve detector performance and insulate the detector against future degradation from oxide growth. Placing the Bi coated sensor in a vacuum system, a reduction chemistry in a plasma (nitrogen/hydrogen (N2/H2) + argon) is used to remove the oxide and promote nitridization of the cleaned Bi surface. Once passivated, the Bi will perform as a better X-ray thermalizer since energy will not be trapped in the bismuth oxides on the surface. A simple additional step, which can be added at various stages of the current fabrication process, can then be applied to encapsulate the Bi film. After plasma passivation, the Bi can be capped with a non-diffusive layer of metal or dielectric. A non-superconducting layer is required such as tungsten or tungsten nitride (WNx).
17. Synthesis and characterization of titanium oxide/bismuth sulfide nanorods for solar cells applications
International Nuclear Information System (INIS)
Solis, M.; Rincon, M. E.
2008-01-01
In the present work is showed the synthesis and characterization of titanium oxide/bismuth sulfide nanowires hetero-junctions for solar cells applications. Conductive glass substrates (Corning 25 x 75 mm) were coated with a thin layer of sol-gel TiO2 and used as substrates for the subsequent deposition of bismuth sulfide nanorods (BN). TiO2 films (∼400 nm) were deposited with a semiautomatic immersion system with controlled immersion/withdraw velocity, using titanium isopropoxide as the titania precursor [1]. For BN synthesis and deposition, the solvo-thermal method was used, introducing air annealed TiO2-substrates in the autoclave. The typical bilayer TiO2/BN hetero-junction was 600 nm thick. The synthesized materials (powders and films) were characterized by X-Ray Diffraction, Scanning Electron Microscopy, and UV-Visible Spectroscopy. Anatase was the crystalline phase of TiO2, while bismuth sulfide nanotubes show a diffraction pattern characteristic of bismuthinite distorted by the preferential growth of some planes [2-4]. The optoelectronic characterization of TiO2/NB hetero-junctions was compared with hetero-junctions obtained by sensitizing TiO2 with chemically deposited bismuth sulfide films. Bismuth sulfide nanowires are 2µm long and 70nm wide (aspect ratio L/D = 43), while chemically deposited bismuth sulfide have L/D = 1, therefore the effect of particle size evaluation and geometry in the photosensitization phenomena will be discussed in the context of new materials for solar-cells applications. (Full text)
18. Basic principles of lead and lead-bismuth eutectic application in blanket of fusion reactors
International Nuclear Information System (INIS)
Beznosov, A.V.; Pinaev, S.S.; Muraviev, E.V.; Romanov, P.V.
2005-01-01
19. Growth morphology and structure of bismuth thin films on GaSb(110)
DEFF Research Database (Denmark)
Gemmeren, T. van; Lottermoser, L.; Falkenberg, G.
1998-01-01
Photoelectron spectroscopy, low-energy electron diffraction, scanning tunneling microscopy and surface X-ray diffraction were used to investigate the growth of thin layers of bismuth on GaSb(110). At submonolayer coverages, growth of two-dimensional islands occurs. A uniform (1 x I)-reconstructio...... that the (1 x 1)-phases formed by antimony and bismuth adsorbates on (110) surfaces of other III-V compound semiconductors are also described by the epitaxial continued layer model. (C) 1998 Elsevier Science B.V. All rights reserved....
20. Evaluation of gamma-ray attenuation properties of bismuth borate glass systems using Monte Carlo method
International Nuclear Information System (INIS)
Tarim, Urkiye Akar; Ozmutlu, Emin N.; Yalcin, Sezai; Gundogdu, Ozcan; Bradley, D.A.; Gurler, Orhan
2017-01-01
A Monte Carlo method was developed to investigate radiation shielding properties of bismuth borate glass. The mass attenuation coefficients and half-value layer parameters were determined for different fractional amounts of Bi 2 O 3 in the glass samples for the 356, 662, 1173 and 1332 keV photon energies. A comparison of the theoretical and experimental attenuation coefficients is presented. - Highlights: • Radiation shielding properties of bismuth borate glass systems have been reported. • Mass attenuation coefficients increase linearly with increase in Bi concentration. • Half-value layer decreases with increasing concentration of Bi. • Half-value layer decreases with the increase in the sample density.
1. Neutron scattering differential cross sections of carbon and bismuth at 37 MeV
International Nuclear Information System (INIS)
Zhou Zuying; Tang Hongqing; Qi Bujia; Zhou Chenwei; Du Yanfeng; Xia Haihong; Walter, R.L.; Tornow, W.; Howell, C.; Braun, R.; Roper, C.; Chen Zemin; Chen Zhengpeng; Chen Yingtang
1997-01-01
Elastic differential cross sections of 37 MeV neutrons scattered from carbon and bismuth were measured in the angular range 11 to 160 degrees by means of the multi-detector TOF facility. The 37 MeV neutrons were produced via the T(d,n) 4 He reaction in a tritium gas target. The pulsed 20 MeV deuteron beam was provided by the HI-13 tandem accelerator. The angular distribution of scattered neutrons from carbon and bismuth were measured in the angular range 11 degree to 145 degree and 11 degree to 160 degree respectively in steps of about 3 degree
2. Bismuth germanate's role in the new revolution in gamma-ray spectroscopy
International Nuclear Information System (INIS)
Johnson, N.R.; Baktash, C.; Lee, I.Y.
1983-01-01
Some of the considerations on how to effectively incorporate bismuth germanate into complex detection systems are covered, and some of these new systems now in operation or under construction are discussed. Significant achievements in gamma ray spectroscopy are reviewed as well as some recent results based on data taken with coincidence arrays of germanium detectors and Compton-suppression spectrometers. Then the first impact of bismuth germanate detectors on our understanding of the properties of nuclei that have high energy and very high angular momentum states are addressed
3. Formic acid oxidation at platinum-bismuth catalysts
Directory of Open Access Journals (Sweden)
Popović Ksenija Đ.
2015-01-01
Full Text Available The field of heterogeneous catalysis, specifically catalysis on bimetallic surfaces, has seen many advances over the past few decades. Bimetallic catalysts, which often show electronic and chemical properties that are distinct from those of their parent metals, offer the opportunity to obtain new catalysts with enhanced selectivity, activity, and stability. The oxidation of formic acid is of permanent interest as a model reaction for the mechanistic understanding of the electrooxidation of small organic molecules and because of its technical relevance for fuel cell applications. Platinum is one of the most commonly used catalysts for this reaction, despite the fact that it shows a few significant disadvantages: high cost and extreme susceptibility to poisoning by CO. To solve this problem, several approaches have been used, but generally, they all consist in the modification of platinum with a second element. Especially, bismuth has received significant attention as Pt modifier. According to the results presented in this survey dealing with the effects influencing the formic acid oxidation it was found that two types of Pt-Bi bimetallic catalysts (bulk and low loading deposits on GC showed superior catalytic activity in terms of the lower onset potential and oxidation current density, as well as exceptional stability compared to Pt. The findings in this report are important for the understanding of mechanism of formic acid electrooxidation on a bulk alloy and decorated surface, for the development of advanced anode catalysts for direct formic acid fuel cells, as well as for the synthesis of novel low-loading bimetallic catalysts. The use of bimetallic compounds as the anode catalysts is an effective solution to overcoming the problems of the formic acid oxidation current stability for long term applications. In the future, the tolerance of both CO poisoning and electrochemical leaching should be considered as the key factors in the development
4. Bismuth subsalicylate nanoparticles with anaerobic antibacterial activity for dental applications
Science.gov (United States)
Vega-Jiménez, A. L.; Almaguer-Flores, A.; Flores-Castañeda, M.; Camps, E.; Uribe-Ramírez, M.; Aztatzi-Aguilar, O. G.; De Vizcaya-Ruiz, A.
2017-10-01
In recent years, nanomaterials have been used in the medical-dental field as new alternative antimicrobial agents. Bismuth subsalicylate (BSS) has been used as an antimicrobial agent, but the effect of BSS in the form of nanoparticles (BSS-nano) as a potential antimicrobial agent has not been tested, in specific against bacteria responsible for periodontal disease. The aim of this study was to evaluate the antibacterial effect of BSS-nano against oral anaerobic bacteria and to assess the safety of BSS-nano by evaluating their cytotoxicity in human gingival fibroblast (HGF-1) cells. BSS-nano were synthesized by laser ablation and were previously physico-chemically characterized using in vitro assays. The antibacterial activity was measured using the tetrazolium-based XTT assay, and cytotoxicity was determined using lactate dehydrogenase (LDH) and MTS assays in HGF-1 cells. Transmission electron microscopy of HGF-1 exposed to BSS-nano was also performed. BSS-nano was shown to have a primary size of 4-22 nm and a polygonal shape. Among the tested bacterial strains, those with a greater sensitivity to BSS-nano (highest concentration of 21.7 μg ml-1) were A. actinomycetemcomitans, C. gingivalis, and P. gingivalis. BSS-nano at a concentration of 60 μg ml-1 showed low cytotoxicity (6%) in HFG-1 cells and was mainly localized intracellularly in acidic vesicles. Our results indicate that the concentration of BSS-nano used as an effective antibacterial agent does not induce cytotoxicity in mammalian cells; thus, BSS-nano can be applied as an antibacterial agent in dental materials or antiseptic solutions.
5. Lead-Bismuth-Eutectic Spallation Neutron Source for Nuclear Transmuter
International Nuclear Information System (INIS)
Gohar, Y.; Herceg, J.; Krajtl, L.; Micklich, B.; Pointer, D.; Saiveau, J.; Sofu, T.; Finck, P.
2002-01-01
A lead-bismuth eutectic (LBE) spallation target design concept has been developed for the subcritical multiplier (SCM) design of the accelerator-driven test facility (ADTF). The design is based on a coaxial geometrical configuration, which has been carefully analyzed and designed to achieve an optimum performance. The target design description, the results from the parametric studies, and the design analyses including neutronics, heat transfer, and hydraulics analyses are given in this paper. A detailed MCNPX geometrical model for the target has been developed to generate heating rates and nuclear responses in the structural material for the design process. The beam has a uniform distribution of 600 MeV protons and 5-MW total power. A small LBE buffer is optimized to reduce the irradiation damage in the SCM fuel elements from the scatter protons and the high-energy neutrons, to maximize the neutron yield to the SCM operation, and to provide inlet and outlet manifolds for the LBE coolant. A special attention has been given to the target window design to enhance its lifetime. The window volumetric heating is 766 W/cm 3 relative to 750 W/cm 3 in LBE for a 40-μA/cm 2 current density. The results show that the nuclear heating from the proton beam diminishes at about 32 cm along the beam axis in the LBE target material. The neutron contribution to the atomic displacement is in the range of 94 to ∼100% for the structure material outside the proton beam path. In the beam window, the neutron contribution is ∼74% and the proton beam is responsible for more than 95% of the total gas production. The proton contribution to the gas production vanishes outside the beam path. The LBE average velocity is ∼2 m/s. The heat transfer and the hydraulics analyses have been iterated to reduce the maximum temperature and the thermal stress level in the target window to enhance its operating life. (authors)
6. New ternary tantalum borides containing boron dumbbells: Experimental and theoretical studies of Ta2OsB2 and TaRuB
International Nuclear Information System (INIS)
Mbarki, Mohammed; Touzani, Rachid St.; Rehorn, Christian W.G.; Gladisch, Fabian C.; Fokwa, Boniface P.T.
2016-01-01
The new ternary transition metal-rich borides Ta 2 OsB 2 and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that Ta 2 OsB 2 and TaRuB crystallize in the tetragonal Nb 2 OsB 2 (space group P4/mnc, no. 128) and the orthorhombic NbRuB (space group Pmma, no. 51) structure types with lattice parameters a=5.878(2) Å, c=6.857(2) Å and a=10.806(2) Å, b=3.196(1) Å, c=6.312(2) Å, respectively. Furthermore, crystallographic, electronic and bonding characteristics have been studied by density functional theory (DFT). Electronic structure relaxation has confirmed the crystallographic parameters while COHP bonding analysis indicates that B 2 -dummbells are the strongest bonds in both compounds. Moreover, the formation of osmium dumbbells in Ta 2 OsB 2 through a Peierls distortion along the c-axis, is found to be the origin of superstructure formation. Magnetic susceptibility measurements reveal that the two phases are Pauli paramagnets, thus confirming the theoretical DOS prediction of metallic character. Also hints of superconductivity are found in the two phases, however lack of single phase samples has prevented confirmation. Furthermore, the thermodynamic stability of the two modifications of AMB (A=Nb, Ta; M =Ru, Os) are studied using DFT, as new possible phases containing either B 4 - or B 2 -units are predicted, the former being the most thermodynamically stable modification. - Graphical abstract: The two new ternary tantalum borides, Ta 2 OsB 2 and TaRuB, have been discovered. Their crystal structures contain boron dumbbells, which are the strongest bonds. Peirls distortion is found responsible for Os 2 -dumbbells formation in Ta 2 OsB 2 . Ta 2 OsB 2 and TaRuB are Pauli paramagnet and potential superconductors. - Highlights:
7. The coloring problem in the solid-state metal boride carbide ScB{sub 2}C{sub 2}. A theoretical analysis
Energy Technology Data Exchange (ETDEWEB)
Lassoued, Souheila [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Boucher, Benoit [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques; Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany); Boutarfaia, Ahmed [Universite Kasdi Merbah-Ouargla (Algeria). Faculte des Mathematiques et des Sciences de la Matiere; Gautier, Regis; Halet, Jean-Francois [Universite de Rennes, Ecole Nationale Superieure de Chimie, UMR 6226 CNRS (France). Inst. des Sciences Chimiques
2016-08-01
The electronic properties of the layered ternary metal boride carbide ScB{sub 2}C{sub 2}, the structure of which consists of B/C layers made of fused five- and seven-membered rings alternating with scandium sheets, are analyzed. In particular, the respective positions of the B and C atoms (the so-called coloring problem) are tackled using density functional theory, quantum theory of atoms in molecules, and electron localizability indicator calculations. Results reveal that (i) the most stable coloring minimizes the number of B-B and C-C contacts and maximizes the number of boron atoms in the heptagons, (ii) the compound is metallic in character, and (iii) rather important covalent bonding occurs between the metallic sheets and the boron-carbon network.
8. Adsorption of volatile polonium and bismuth species on metals in various gas atmospheres. Pt. I. Adsorption of volatile polonium and bismuth on gold
Energy Technology Data Exchange (ETDEWEB)
Maugeri, Emilio Andrea; Neuhausen, Joerg; Dressler, Rugard; Piguet, David; Voegele, Alexander; Schumann, Dorothea [Paul Scherrer Institut (PSI), Villigen (Switzerland). Lab. for Radiochemistry; Eichler, Robert [Paul Scherrer Institut (PSI), Villigen (Switzerland). Lab. for Radiochemistry; Bern Univ. (Switzerland). Dept. for Chemistry and Biochemistry; Rijpstra, Kim [Ghent Univ., Zwijnaarde (Belgium). Center for Molecular Modeling (CMM); Cottenier, Stefaan [Ghent Univ., Zwijnaarde (Belgium). Center for Molecular Modeling (CMM); Ghent Univ., Zwijnaarde (Belgium). Dept. of Materials Science and Engineering
2016-07-01
Polonium isotopes are considered the most hazardous radionuclides produced during the operation of accelerator driven systems (ADS) when lead-bismuth eutectic (LBE) is used as the reactor coolant and as the spallation target material. In this work the use of gold surfaces for capturing polonium from the cover gas of the ADS reactor was studied by thermochromatography. The results show that gaseous monoatomic polonium, formed in dry hydrogen, is adsorbed on gold at 1058 K. Its adsorption enthalpy was calculated as -250±7 kJ mol{sup -1}, using a Monte Carlo simulation code. Highly volatile polonium species that were observed in similar experiments in fused silica columns in the presence of moisture in both inert and reducing gas were not detected in the experiments studying adsorption on gold surfaces. PoO{sub 2} is formed in both dry and moist oxygen, and its interaction with gold is characterized by transport reactions. The interaction of bismuth, present in large amounts in the atmosphere of the ADS, with gold was also evaluated. It was found that bismuth has a higher affinity for gold, compared to polonium, in an inert, reducing, and oxidizing atmosphere. This fact must be considered when using gold as a material for filtering polonium in the cover gas of ADS.
9. Effects of crystallite structure and interface band alignment on the photocatalytic property of bismuth ferrite/ (N-doped) graphene composites
International Nuclear Information System (INIS)
Li, Pai; Chen, Qiang; Lin, Yinyin; Chang, Gang; He, Yunbin
2016-01-01
Bismuth ferrite/graphene (N-doped graphene) photocatalysts are successfully prepared by a facile and effective two-step hydrothermal method. Bismuth ferrite/graphene shows superior photocatalytic activity compared with bismuth ferrite/N-doped graphene and pure BiFeO 3 . X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy analyses indicate that Bi 25 FeO 40 crystalline phase is obtained with the addition of graphene, while BiFeO 3 is formed under the same hydrothermal conditions in the presence of N-doped graphene. Core-level and valence-band X-ray photoelectron spectroscopy analyses reveal a downward band bending of bismuth ferrite (∼0.5 eV) at the interface of the bismuth ferrite/(N-doped) graphene composites, which facilitates the electron transfer from bismuth ferrite to (N-doped) graphene and suppresses the recombination of photo-generated electron–hole pairs. This downward bending band alignment at the interface supposes to be the main mechanism underlying the enhanced photocatalytic activity of the bismuth ferrite/graphene composites that are currently of great interest in the photocatalysis field. - Highlights: • Bismuth ferrite/(N-doped) graphene composites were prepared by a hydrothermal method. • Bi 25 FeO 40 and BiFeO 3 were obtained with presence of graphene and N-graphene, respectively. • Bi 25 FeO 40 /graphene shows superior photocatalytic activity over BiFeO 3 and BiFeO 3 /N-graphene. • A downward band bending (∼0.5 eV) of bismuth ferrite exists at the composites interface. • The downward band bending supposes to be the mechanism for the enhanced photocatalytic activity.
10. Ultrathin bismuth nanosheets from in situ topotactic transformation for selective electrocatalytic CO2 reduction to formate.
Science.gov (United States)
Han, Na; Wang, Yu; Yang, Hui; Deng, Jun; Wu, Jinghua; Li, Yafei; Li, Yanguang
2018-04-03
Electrocatalytic carbon dioxide reduction to formate is desirable but challenging. Current attention is mostly focused on tin-based materials, which, unfortunately, often suffer from limited Faradaic efficiency. The potential of bismuth in carbon dioxide reduction has been suggested but remained understudied. Here, we report that ultrathin bismuth nanosheets are prepared from the in situ topotactic transformation of bismuth oxyiodide nanosheets. They process single crystallinity and enlarged surface areas. Such an advantageous nanostructure affords the material with excellent electrocatalytic performance for carbon dioxide reduction to formate. High selectivity (~100%) and large current density are measured over a broad potential, as well as excellent durability for >10 h. Its selectivity for formate is also understood by density functional theory calculations. In addition, bismuth nanosheets were coupled with an iridium-based oxygen evolution electrocatalyst to achieve efficient full-cell electrolysis. When powered by two AA-size alkaline batteries, the full cell exhibits impressive Faradaic efficiency and electricity-to-formate conversion efficiency.
11. Study of bismuth oxide compounds as cathodic materials in lithium accumulators
International Nuclear Information System (INIS)
Apostolova, R.D.; Shembel', E.M.
1999-01-01
Two groups of bismuth oxide base compounds: rare earth bismuthides - SmBiO 3 and EuBiO 3 , as well as the Aurivillius phase - Bi 4 V 2 O 11 , were synthesized and electrochemically studied as novel cathodic materials for high-energy lithium current sources [ru
12. 75 FR 14491 - Listing of Color Additives Exempt From Certification; Bismuth Citrate
Science.gov (United States)
2010-03-26
... DEPARTMENT OF HEALTH AND HUMAN SERVICES Food and Drug Administration 21 CFR Part 73 [Docket No... Safety and Applied Nutrition (HFS-265), Food and Drug Administration, 5100 Paint Branch Pkwy., College... results from a 90-day oral toxicity study on bismuth citrate in rats, genotoxicity studies, dermal...
13. Sensing characteristics of nanocrystalline bismuth oxide clad-modified fiber optic gas sensor
Science.gov (United States)
Manjula, M.; Karthikeyan, B.; Sastikumar, D.
2017-08-01
Gas sensing properties of nanocrystalline bismuth oxide clad - modified fiber optic sensor is reported for ammonia, ethanol, methanol and acetone gasses at room temperature. The output of sensor increases or decreases for certain gasses when the concentration of the gas is increased. The sensor exhibits high response and good selectivity to methanol gas. Time response characteristics of the sensor are also reported.
14. The design of the data acquisition system for a very large bismuth germanate calorimeter
Energy Technology Data Exchange (ETDEWEB)
Bakken, J.; Isaila, M.; Piroue, P.; Stickland, D.; Sumner, R.
1984-02-01
LEPC, the Large Electron Positron Collider being built at CERN, will be ready for experiments in 1988. A large array of bismuth germanate crystals will be part of one of the first experiments to be installed. Particles (including photons) resulting from the collisions will be identified and measured in the surrounding detector. At the center of this composite detector is a tracking device to observe the trajectories of all particles. Beyond this is the bismuth germanate array; it will measure the energy of electrons and photons from a few MeV to 100 GeV. This is surrounded by the hadron calorimeter. The bismuth germanate calorimeter will consist of about 12,000 individual bismuth germanate crystals. Each crystal will have an independent readout system. This system uses silicon photodiodes, each with its own ADC, to measure the scintillation light from each crystal. The ADC is implemented in software in a single chip microcomputer, using a modification of successive approximation, which produces a very wide dynamic range. The microcomputer also provides data buffering and several other housekeeping functions. The initial design of the readout system, presented in this paper, evolved from an attempt to minimize the size requirements and the number of cables needed, and to meet the dynamic range requirement in a practical way.
15. The design of the data acquisition system for a very large bismuth germanate calorimeter
International Nuclear Information System (INIS)
Bakken, J.; Isaila, M.; Piroue, P.; Stickland, D.; Sumner, R.
1984-01-01
LEPC, the Large Electron Positron Collider being built at CERN, will be ready for experiments in 1988. A large array of bismuth germanate crystals will be part of one of the first experiments to be installed. Particles (including photons) resulting from the collisions will be identified and measured in the surrounding detector. At the center of this composite detector is a tracking device to observe the trajectories of all particles. Beyond this is the bismuth germanate array; it will measure the energy of electrons and photons from a few MeV to 100 GeV. This is surrounded by the hadron calorimeter. The bismuth germanate calorimeter will consist of about 12,000 individual bismuth germanate crystals. Each crystal will have an independent readout system. This system uses silicon photodiodes, each with its own ADC, to measure the scintillation light from each crystal. The ADC is implemented in software in a single chip microcomputer, using a modification of successive approximation, which produces a very wide dynamic range. The microcomputer also provides data buffering and several other housekeeping functions. The initial design of the readout system, presented in this paper, evolved from an attempt to minimize the size requirements and the number of cables needed, and to meet the dynamic range requirement in a practical way
16. Fridel-Crafts acylation using bismuth triflate in [BMI][PF6
DEFF Research Database (Denmark)
Tran, Phuong Hoang; Duus, Fritz; Le, Thach Ngoc
2012-01-01
Bismuth trifluoromethanesulfonate was found to be a good catalyst for the Friedel–Craftsacylation. Bismuthtriflate immobilized in an ionic liquid was the most efficient catalytic system. Bismuthtriflate in [BMI][PF6] catalyzes this reaction under microwave irradiation allowing the rapid synthesis...
17. Studying Impact of Different Precipitating Agents on Crystal Structure, Morphology and Photocatalytic Activity of Bismuth Oxide
Directory of Open Access Journals (Sweden)
Yayuk Astuti
2017-10-01
How to Cite: Astuti, Y., Arnelli, Pardoyo, Fauziyah, A., Nurhayati, S., Wulansari, A.D., Andianingrum, R., Widiyandari, H., Bhaduri, G.A. (2017. Studying Impact of Different Precipitating Agents on Crystal Structure, Morphology and Photocatalytic Activity of Bismuth Oxide. Bulletin of Chemical Reaction Engineering & Catalysis, 12 (3: 478-484 (doi:10.9767/bcrec.12.3.1144.478-484
18. Microwave-assisted facile and rapid Friedel-Crafts benzoylation of arenes catalysed by bismuth trifluoromethanesulfonate
DEFF Research Database (Denmark)
Tran, Phoung Hoang; Hansen, Poul Erik; Pham, Thuy Than
2014-01-01
The catalytic activity of metal triflates was investigated in Friedel–Crafts benzoylation under microwave irradiation. Friedel–Crafts benzoylation with benzoyl chloride of a variety of arenes containing electron-rich and electron-poor rings using bismuth triflate under microwave irradiation is de...
19. Mucosa protectives: sucralfate and colloidal bismuth subcitrate in peptic ulcer disease
NARCIS (Netherlands)
Tytgat, G. N.; Nio, C. Y.
1987-01-01
Mucosa protective drugs are thought to have an important role in the treatment of both duodenal (DU) and gastric ulcer (GU) disease by means of correcting the disturbed defensive factors. Sucralfate as well as colloidal bismuth subcitrate (CBS) form a layer on the ulcer base and in this way protect
20. Dynamic spatial structure of spontaneous beams in photorefractive bismuth sillicon oxide
DEFF Research Database (Denmark)
Buchhave, Preben; Lyuksyutov, S.; Vasnetsov, M.
1996-01-01
We report the domain structure of spontaneously occurring beams (subharmonics) in photorefractive bismuth silicon oxide with an applied electric field from 1 to 6 kV/cm and a running grating. The subharmonic beams are generated in a pattern of domains that evolve dynamically as they move through ...
1. Dismantling and chemical characterization of spent Peltier thermoelectric devices for antimony, bismuth and tellurium recovery.
Science.gov (United States)
Balva, Maxime; Legeai, Sophie; Garoux, Laetitia; Leclerc, Nathalie; Meux, Eric
2017-04-01
Major uses of thermoelectricity concern refrigeration purposes, using Peltier devices, mainly composed of antimony, bismuth and tellurium. Antimony was identified as a critical raw material by EU and resources of bismuth and tellurium are not inexhaustible, so it is necessary to imagine the recycling of thermoelectric devices. That for, a complete characterization is needed, which is the aim of this work. Peltier devices were manually dismantled in three parts: the thermoelectric legs, the alumina plates on which remain the electrical contacts and the silicone paste used to connect the plates. The characterization was performed using five Peltier devices. It includes mass balances of the components, X-ray diffraction analysis of the thermoelectric legs and elemental analysis of each part of the device. It appears that alumina represents 45% of a Peltier device in weight. The electrical contacts are mainly composed of copper and tin, and the thermoelectric legs of bismuth, tellurium and antimony. Thermoelectric legs appear to be Se-doped Bi 2 Te 3 and (Bi 0,5 Sb 1,5 )Te 3 for n type and p type semiconductors, respectively. This work shows that Peltier devices can be considered as a copper ore and that thermoelectric legs contain high amounts of bismuth, tellurium and antimony compared to their traditional resources.
2. Improvements in the energy resolution and high-count-rate performance of bismuth germanate
International Nuclear Information System (INIS)
Koehler, P.E.; Wender, S.A.; Kapustinsky, J.S.
1985-01-01
Several methods for improving the energy resolution of bismuth germanate (BGO) have been investigated. It is shown that some of these methods resulted in a substantial improvement in the energy resolution. In addition, a method to improve the performance of BGO at high counting rates has been systematically studied. The results of this study are presented and discussed
3. Structure-Composition-Property Relationships of Complex Bismuth Oxide Based Photocatalysts
Energy Technology Data Exchange (ETDEWEB)
Vogt, Thomas [Univ. of South Carolina, Columbia, SC (United States). Dept. of Chemistry and Biochemistry
2014-01-08
Development of a new family of up- and down-conversion materials based on oxtfluorides that can potentially increase photocatalytic activities of photocatalysts such as bismuth oxides and can also be used as phosphors in Al1-xGaxN-based devices and solar devices.
4. Nanodomains and nanometer-scale disorder in multiferroic bismuth ferrite single crystals
Czech Academy of Sciences Publication Activity Database
Jia, C.L.; Jin, L.; Wang, D.; Mi, S.B.; Alexe, M.; Hesse, D.; Reichlová, Helena; Martí, Xavier; Bellaiche, L.; Urban, K.W.
2015-01-01
Roč. 82, Jan (2015), s. 356-368 ISSN 1359-6454 Institutional support: RVO:68378271 Keywords : bismuth ferrite * crystal growth * high-resolution electron microscopy * atomic structure * first-principles calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.058, year: 2015
5. Study of inclusive proton spectra from 20 MeV deuteron breakup by bismuth
International Nuclear Information System (INIS)
Badiger, N.M.; Hallur, B.R.; Madhusoodhanan, T.; Sathyavathiamma, M.P.; Puttaswamy, N.G.; Darshan, V.P.; Sharma, H.; Chintalapudi, S.N.
1997-01-01
The breakup of deuteron into proton and neutron has been studied earlier to understand the breakup mechanism. Inclusive measurements show the expected broad bumps near the beam velocity. In the present experiment, the breakup of 20 MeV deuterons by bismuth target has been investigated
6. A sensitive fluorescence quenching method for determination of bismuth with tiron
Energy Technology Data Exchange (ETDEWEB)
Taher, Mohammad Ali; Rahimi, Mina [Department of Chemistry, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Fazelirad, Hamid, E-mail: [email protected] [Department of Chemistry, Shahid Bahonar University of Kerman, Kerman (Iran, Islamic Republic of); Department of Chemistry, Science and Research Branch, Islamic Azad University, Yazd (Iran, Islamic Republic of); Young Researchers Society, Shahid Bahonar University of Kerman, P.O. Box 76175-133, Kerman (Iran, Islamic Republic of)
2014-01-15
We describe a fluorescence quenching method for determination of bismuth with tiron. The method is based on the reaction of tiron by bismuth(III) in acidic media. The influence of variables such as the pH, type of buffer, tiron concentration, reaction time and temperature were investigated. Under optimized conditions, the fluorescence quenching extent is proportional to the concentration of bismuth for Bi–tiron system at the range 0.13–2.09 μg mL{sup −1} and the detection limit is 0.05 μg mL{sup −1}. The proposed sensor presented good repeatability, evaluated in terms of relative standard deviation (R.S.D.=±0.498%) for 11 replicates. This sensitive, rapid and accurate method has been successfully applied to the determination of trace bismuth(III) in water and hair samples and certified reference materials. -- Highlights: • No previous paper report on use of fluorescence quenching for determination of Bi. • Fluorescence quenching of trion is a sensitive method for determination of Bi(III). • Under the optimum conditions the detection limit is very low (0.05 μg mL{sup −1}). • The procedure is simple and safe and has high tolerance limit to interferences.
7. Effect of bismuth citrate, lactose, and organic acid on necrotic enteritis in broilers
Science.gov (United States)
Clostridium perfringens – associated necrotic enteritis causes significant losses and increased morbidity in poultry. The objective of this study was to evaluate the effect of bismuth citrate and acidifiers on the development of necrotic enteritis in broilers. The first study was a dose response t...
8. Influence of bismuth on properties and microstructures of Sr0⋅ 5Ba0 ...
Home; Journals; Bulletin of Materials Science; Volume 29; Issue 5. Influence of bismuth on properties and microstructures of Sr0.5Ba0.5–Bi TiO3 thin films. Tao Wenhong Wang Yin Fu Xinghua Wei Qihong. Thin Films Volume 29 Issue 5 October 2006 pp 523-527 ...
9. Bismuth knowledge during the Renaissance strengthened by its use in Italian lustres production
Science.gov (United States)
The knowledge of bismuth during the XV and XVI centuries represents an open question since, according to some authors, this element was confused with lead, tin and silver. On the contrary, G. Agricola (1494-1555), the pioneer of mineralogical science in Europe, in his two works (De Natura Fossilium, Lib X, 1546 and Bermannus Sive De Re Metallica Dialogus, 1528) asserts that bismuth was considered as an element distinct from the other metals at that time. This question gave rise to some interest, and von Lippmann in 1930 wrote a treatise dealing with the history of bismuth between 1400 and 1800. In this work we present the results obtained on Italian and Hispano-Moresque shards studied by means of X-ray diffraction, atomic absorption spectrometry with electrothermal atomisation, inductively coupled plasma optical emission spectrometry and scanning electron microscopy. It seems that our work could provide a new and important contribution to this debate, because we found bismuth in lustre composition of Renaissance shards produced in central Italy. Furthermore, we found that it could also be considered as a discriminating element between Italian and Hispano-Moresque productions, useful to assess their origin.
Directory of Open Access Journals (Sweden)
Vahid Karami
2017-06-01
11. Bismuth oxide based ceramics with improved electrical and mechanical properties: Part II. Structural and mechanical properties
NARCIS (Netherlands)
Kruidhof, H.; Seshan, Kulathuiyer; van de Velde, G.M.H.; de Vries, K.J.; Burggraaf, A.J.
1988-01-01
Coprecipitation as a method of preparation for bismuth oxides based ceramics yields relatively strong and machineable materials in comparison with the solid state reaction. Compositions within the system (1−x)Bi2O3|xEr2O3 containing up to twenty five mole percent of erbium oxide show a slow
12. Solution processed bismuth sulfide nanowire array core/silver shuffle shell solar cells
NARCIS (Netherlands)
Cao, Y.; Bernechea, M.; Maclachlan, A.; Zardetto, V.; Creatore, M.; Haque, S.A.; Konstantatos, G.
2015-01-01
Low bandgap inorganic semiconductor nanowires have served as building blocks in solution processed solar cells to improve their power conversion capacity and reduce fabrication cost. In this work, we first reported bismuth sulfide nanowire arrays grown from colloidal seeds on a transparent
13. Bio-assisted synthesis and characterization of nanostructured bismuth (III) sulphide using Clostridium acetobutylicum
International Nuclear Information System (INIS)
Kamaraj, Sathish Kumar; Venkatachalam, Ganesh; Arumugam, Palaniappan; Berchmans, Sheela
2014-01-01
Nanostructured bismuth (III) sulphide is synthesized at room temperature using a hydrogen sulphide producing microorganism namely Clostridium acetobutylicum. On contrary to chemical routes involving both the high and room temperature methods, the present experimental procedure involves a bio-assisted approach. This method is free from the usage of toxic and hazardous chemicals making it an environment friendly route. The synthesized bismuth sulphide is characterized using transmission electron microscope (TEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). From our experiments we find that bismuth sulphide produced using this bio-assisted approach exhibits a hexagonal shaped plate-like structures and is stabilized by the extracellular proteins present in the culture medium. - Graphical abstract: A green chemistry approach towards the synthesis of bismuth (III) sulphide nanostructures at room temperature using a hydrogen sulphide producing microorganism namely, Clostridium acetobutylicum is demonstrated. - Highlights: • Environmentally benign (greener) route towards synthesis of Bi 2 S 3 nanostructures. • Bio-assisted synthesis of Bi 2 S 3 at room temperature using Clostridium acetobutylicum. • Extracellular proteins in H 2 S producing microorganism as stabilizer for Bi 2 S 3 NPs. • Hexagonal platelets of Bi 2 S 3 possessing an orthorhombic crystalline structure
14. Dietary intake of barium, bismuth, chromium, lithium, and strontium in a Spanish population (Canary Islands, Spain).
Science.gov (United States)
González-Weller, Dailos; Rubio, Carmen; Gutiérrez, Ángel José; González, Gara Luis; Caballero Mesa, José María; Revert Gironés, Consuelo; Burgos Ojeda, Antonio; Hardisson, Arturo
2013-12-01
The aim of this study was to analyze barium, bismuth, chromium, lithium, and strontium contents in food and beverages consumed by the population of the Canary Islands (Spain) as well as determine dietary intake of these metals in the archipelago as a whole and in its individual islands. To this end, 440 samples were analyzed by ICP-OES and GFAAS. Barium concentrations ranged from 5.210 ± 2.117 mg/kg in nuts to 0.035 ± 0.043 mg/L in water. Viscera exhibited the highest levels of bismuth (38.07 ± 36.80 mg/kg). The cold meat and sausages group stood out for its high chromium concentrations (0.494 ± 0.257 mg/kg). The highest concentration of lithium and strontium came out in nuts (8.761 ± 5.368 mg/kg and 9.759 ± 5.181 mg/kg, respectively). The total intakes of barium, bismuth, chromium, lithium, and strontium were 0.685, 1.274, 0.087, 3.674, and 1.923 mg/day, respectively. Cereals turned out to contribute most to the dietary intake of barium, bismuth, chromium, and lithium in the Canary Islands, while fruit contributes most to the strontium intake. We also performed a metal intake study by age and sex of the population and compared the outcome with data from other regions, both national and international.
15. First heats of cerium solution in liquid aluminium, gallium, indium, tin, lead and bismuth
International Nuclear Information System (INIS)
Yamshchikov, L.F.; Lebedev, V.A.; Nichkov, I.F.; Raspopin, S.P.; Shein, V.G.
1983-01-01
Cerium solution heats in liquid alluminium, gallium, indium, tin, lead and bismuth are determined in high temperature mixing calorimeter with an isothermal shell. The statistical analysis carried out proves that values of cerium solution heat in fusible metals obtained by the methods of electric motive forces and calorimety give a satisfactory agreement
16. Evaluation of gamma-ray attenuation properties of bismuth borate glass systems using Monte Carlo method
Science.gov (United States)
Tarim, Urkiye Akar; Ozmutlu, Emin N.; Yalcin, Sezai; Gundogdu, Ozcan; Bradley, D. A.; Gurler, Orhan
2017-11-01
A Monte Carlo method was developed to investigate radiation shielding properties of bismuth borate glass. The mass attenuation coefficients and half-value layer parameters were determined for different fractional amounts of Bi2O3 in the glass samples for the 356, 662, 1173 and 1332 keV photon energies. A comparison of the theoretical and experimental attenuation coefficients is presented.
17. Light-Induced Surface Reactions at the Bismuth Vanadate/Potassium Phosphate Interface.
Science.gov (United States)
Favaro, Marco; Abdi, Fatwa F; Lamers, Marlene; Crumlin, Ethan J; Liu, Zhi; van de Krol, Roel; Starr, David E
2018-01-18
Bismuth vanadate has recently drawn significant research attention as a light-absorbing photoanode due to its performance for photoelectrochemical water splitting. In this study, we use in situ ambient pressure X-ray photoelectron spectroscopy with "tender" X-rays (4.0 keV) to investigate a polycrystalline bismuth vanadate (BiVO 4 ) electrode in contact with an aqueous potassium phosphate (KPi) solution at open circuit potential under both dark and light conditions. This is facilitated by the creation of a 25 to 30 nm thick electrolyte layer using the "dip-and-pull" method. We observe that under illumination bismuth phosphate forms on the BiVO 4 surface leading to an increase of the surface negative charge. The bismuth phosphate layer may act to passivate surface states observed in photoelectrochemical measurements. The repulsive interaction between the negatively charged surface under illumination and the phosphate ions in solution causes a shift in the distribution of ions in the thin aqueous electrolyte film, which is observed as an increase in their photoelectron signals. Interestingly, we find that such changes at the BiVO 4 /KPi electrolyte interface are reversible upon returning to dark conditions. By measuring the oxygen 1s photoelectron peak intensities from the phosphate ions and liquid water as a function of time under dark and light conditions, we determine the time scales for the forward and reverse reactions. Our results provide direct evidence for light-induced chemical modification of the BiVO 4 /KPi electrolyte interface.
18. Improvements to a Flow Sensor for Liquid Bismuth-Fed Hall Thrusters
Science.gov (United States)
Bonds, Kevin; Polzin, Kurt A.
2010-01-01
Recently, there has been significant interest in using bismuth metal as a propellant in Hall Thrusters [1, 2]. Bismuth offers some considerable cost, weight, and space savings over the traditional propellant--xenon. Quantifying the performance of liquid metal-fed Hall thrusters requires a very precise measure of the low propellant flow rates [1, 2]. The low flow rates (10 mg/sec) and the temperature at which free flowing liquid bismuth exists (above 300 C) preclude the use of off-the-shelf flow sensing equipment [3]. Therefore a new type of sensor is required. The hotspot bismuth flow sensor, described in Refs. [1-5] is designed to perform a flow rate measurement by measuring the velocity at which a thermal feature moves through a flow chamber. The mass flow rate can be determined from the time of flight of the thermal peak, [4, 5]. Previous research and testing has been concerned mainly with the generation of the thermal peak and it's subsequent detection. In this paper, we present design improvements to the sensor concept; and the results of testing conducted to verify the functionality of these improvements. A ceramic material is required for the sensor body (see Fig. 1), which must allow for active heating of the bismuth flow channel to keep the propellant in a liquid state. The material must be compatible with bismuth and must be bonded to conductive elements to allow for conduction of current into the liquid metal and measurement of the temperature in the flow. The new sensor requires fabrication techniques that will allow for a very small diameter flow chamber, which is required to produce useful measurements. Testing of various materials has revealed several that are potentially compatible with liquid bismuth. Of primary concern in the fabrication and testing of a robust, working prototype, is the compatibility of the selected materials with one another. Specifically, the thermal expansion rates of the materials relative to the ceramic body cannot expand so
19. The synthesis, structure and reactivity of iron-bismuth complexes : Potential Molecular Precursors for Multiferroic BiFeO3
OpenAIRE
Wójcik, Katarzyna
2009-01-01
The thesis presented here is focused on the synthesis of iron-bismuth alkoxides and siloxides as precursors for multiferroic BiFeO3 systems. Spectrum of novel cyclopentadienyl substituted iron-bismuth complexes of the general type [{Cpy(CO)2Fe}BiX2], as potential precursors for cyclopentadienyl iron-bismuth alkoxides or siloxides [{Cpy(CO)2Fe}Bi(OR)2] (R-OtBu, OSiMe2tBu), were obtained and characterised. The use of wide range of cyclopentadienyl rings in the iron carbonyl compounds allowed fo...
20. Bismuth silicate glass containing heavy metal oxide as a promising radiation shielding material
Science.gov (United States)
Elalaily, Nagia A.; Abou-Hussien, Eman M.; Saad, Ebtisam A.
2016-12-01
Optical and FTIR spectroscopic measurements and electron paramagnetic resonance (EPR) properties have been utilized to investigate and characterize the given compositions of binary bismuth silicate glasses. In this work, it is aimed to study the possibility of using the prepared bismuth silicate glasses as a good shielding material for γ-rays in which adding bismuth oxide to silicate glasses causes distinguish increase in its density by an order of magnitude ranging from one to two more than mono divalent oxides. The good thermal stability and high density of the bismuth-based silicate glass encourage many studies to be undertaken to understand its radiation shielding efficiency. For this purpose a glass containing 20% bismuth oxide and 80% SiO2 was prepared using the melting-annealing technique. In addition the effects of adding some alkali heavy metal oxides to this glass, such as PbO, BaO or SrO, were also studied. EPR measurements show that the prepared glasses have good stability when exposed to γ-irradiation. The changes in the FTIR spectra due to the presence of metal oxides were referred to the different housing positions and physical properties of the respective divalent Sr2+, Ba2+ and Pb2+ ions. Calculations of optical band gap energies were presented for some selected glasses from the UV data to support the probability of using these glasses as a gamma radiation shielding material. The results showed stability of both optical and magnetic spectra of the studied glasses toward gamma irradiation, which validates their irradiation shielding behavior and suitability as the radiation shielding candidate materials.
1. Alkali metal bismuth(III) chloride double salts
Energy Technology Data Exchange (ETDEWEB)
Kelly, Andrew W. [Department of Chemistry, College of William and Mary, Williamsburg, VA 23187 (United States); Nicholas, Aaron; Ahern, John C. [Department of Chemistry, University of Maine, Orono, ME 04469 (United States); Chan, Benny [Department of Chemistry, College of New Jersey, Ewing, NJ 08628-0718 (United States); Patterson, Howard H. [Department of Chemistry, University of Maine, Orono, ME 04469 (United States); Pike, Robert D., E-mail: [email protected] [Department of Chemistry, College of William and Mary, Williamsburg, VA 23187 (United States)
2016-06-15
near 295, 340, and 380 nm and a broad emission near 440 nm. - Graphical abstract: The double salts Na2BiCl5·5H2O, K7Bi3Cl16, Rb3BiCl6·0.5H2O, Cs3BiCl6, and Cs3Bi2Cl9 were formed by co-crystallization of MCl (M = Na, K, Rb, Cs) with BiOCl in aqueous HCl. The crystal structures and solid state luminescence are reported. - Highlights: • New double salt phases are reported for NaCl/BiCl{sub 3}, KCl/BiCl{sub 3}, RbCl/BiCl{sub 3}, and CsCl/BiCl{sub 3}. • A variety of alkali chloride:bismuth chloride ratios are reported. • Chloride bridging produces oligomeric and/or polymeric bismuth chloride chains in several cases. • Convenient bulk synthesis from BiOCl is reported. • Four of the five reported double salts exhibit photoluminescence as a result of charge transfer.
2. Determination of zinc and cadmium with characterized Electrodes of carbon and polyurethane modified by a bismuth film
Directory of Open Access Journals (Sweden)
Jossy Karla Brasil Bernardelli
2011-09-01
Full Text Available This study aims to use electrodes modified with bismuth films for the determination of zinc and cadmium. The film was electrodeposited ex situ on a composite carbon electrode with polyurethane and 2% metallic bismuth (2BiE and on a carbon bar electrode (CBE. The electrodes were characterized by scanning electron microscopy and energy dispersive spectroscopy. Through differential pulse anodic stripping voltammetry, the electrodes 2BiE and CBE containing bismuth films showed a limit of detection (LOD of 5.56 × 10-5 and 3.07 × 10-5 g.L-1 for cadmium and 1.24 × 10-4 and 1.53 × 10-4 g.L-1 for zinc, respectively. The presence of a bismuth film increased the sensitivity of both electrodes.
3. Determination of Lung-to-Blood Absorption Rates for Lead and Bismuth which are Appropriate for Radon Progeny
International Nuclear Information System (INIS)
Marsh, J.W.; Birchall, A.
1999-01-01
The ICRP Publication 66 Human Respiratory Tract Model (HRTM) treats clearance as a competitive process between absorption into blood and particle transport to the gastrointestinal tract and lymphatics. The ICRP recommends default absorption rates for lead and bismuth in ICRP Publication 71 but states that the values are not appropriate for short-lived radon progeny. This paper describes an evaluation of published data from volunteer experiments to estimate the absorption half-times of lead and bismuth that are appropriate for short-lived radon progeny. The absorption half-time for lead was determined to be 10±2 h, based on 212 Pb lung and blood retention data from several studies. The absorption half-time for bismuth was estimated to be about 13 h, based on 212 Bi urinary excretion data from one experiment and the ICRP biokinetic model for bismuth as a decay product of lead. (author)
4. Correlation between near infrared emission and bismuth radical species of Bi2O3-containing aluminoborate glass
International Nuclear Information System (INIS)
Masai, Hirokazu; Takahashi, Yoshihiro; Fujiwara, Takumi; Suzuki, Takenobu; Ohishi, Yasutake
2009-01-01
A strong correlation between bismuth radical species and emission in the near infrared (NIR) region of SnO-doped bismuth-containing aluminoborate glass, (CaO-B 2 O 3 -Bi 2 O 3 -Al 2 O 3 -TiO 2 ) (CaBBAT), was observed. Since the activation energy of the NIR emission was similar to that of electron spin resonance signal, it is expected that bismuth radical species in the CaBBAT glass is an origin of the NIR emission. Compared to the observed emission spectra with energy diagram of previous data, we have confirmed that bismuth ion possessing low valence is the origin of broad emission in the NIR region.
5. A Study on the Effect of the Boron Potential on the Mechanical Properties of the Borided Layers Obtained by Boron Diffusion at the Surface of AISI 316L Steel
Directory of Open Access Journals (Sweden)
E. Hernández-Sánchez
2014-01-01
Full Text Available The effect of the boron potential on the thickness and the mechanical properties of borided layers was evaluated. The boron potential was established by means of the available atoms of boron contained in a control volume inside a cylinder. The cylinders were manufactured from AISI 316L steel, and the boriding treatment was performed using the powder pack technique at a temperature of 1273 K over an exposure time of 6 h. Four different internal diameters of the cylinders were evaluated (3.17, 4.76, 6.35, and 7.93 mm. The mechanical properties were evaluated using the Berkovich instrumented indentation technique. The results showed a clear influence of the boron potential on the mechanical properties of the layers. The hardness of the layers was stablished in the range of 16.22 to 21.16 GPa. Young’s modulus values were stablished in the range of 255.96 to 341.37 GPa. Also the fracture toughness and brittleness of the layers reflected the influence of the boron potential supplied during the boriding process. Finally, the influence of the boron potential on the constant of parabolic growth (K was also established as a function of the inner diameter of the cylinders.
International Nuclear Information System (INIS)
Beznosov, A.V.; Bokova, T.A.; Molodtsov, A.A.
2006-01-01
The reactor emergency heat removal systems should transfer heat from the surface of reactor core fuel element claddings to the primary circuit followed by heat transfer to the environment. One suggests three design approaches for emergency heat removal systems in lead-bismuth and lead cooled reactor circuits that take account of the peculiar nature of their features. Application of the discussed systems for emergency heat removal improves safety of lead-bismuth and lead cooled reactor plants [ru
7. Bismuth-ceramic nanocomposites through ball milling and liquid crystal synthetic methods
Science.gov (United States)
Dellinger, Timothy Michael
Three methods were developed for the synthesis of bismuth-ceramic nanocomposites, which are of interest due to possible use as thermoelectric materials. In the first synthetic method, high energy ball milling of bismuth metal with either MgO or SiO2 was found to produce nanostructured bismuth dispersed on a ceramic material. The morphology of the resulting bismuth depended on its wetting behavior with respect to the ceramic: the metal wet the MgO, but did not wet on the SiO2. Differential Scanning Calorimetry measurements on these composites revealed unusual thermal stability, with nanostructure retained after multiple cycles of heating and cooling through the metal's melting point. The second synthesis methodology was based on the use of lyotropic liquid crystals. These mixtures of water and amphiphilic molecules self-assemble to form periodic structures with nanometer-scale hydrophilic and hydrophobic domains. A novel shear mixing methodology was developed for bringing together reactants which were added to the liquid crystals as dissolved salts. The liquid crystals served to mediate synthesis by acting as nanoreactors to confine chemical reactions within the nanoscale domains of the mesophase, and resulted in the production of nanoparticles. By synthesizing lead sulfide (PbS) and bismuth (Bi) particles as proof-of-concept, it was shown that nanoparticle size could be controlled by controlling the dimensionality of the nanoreactors through control of the liquid crystalline phase. Particle size was shown to decrease upon going from three-dimensionally percolating nanoreactors, to two dimensional sheet-like nanoreactors, to one dimensional rod-like nanoreactors. Additionally, particle size could be controlled by varying the precursor salt concentration. Since the nanoparticles did not agglomerate in the liquid crystal immediately after synthesis, bismuth-ceramic nanocomposites could be prepared by synthesizing Bi nanoparticles and mixing in SiO2 particles which
8. Separation of bismuth from gram amounts of thallium and silver by cation-exchange chromatography in nitric acid.
Science.gov (United States)
Meintjies, E; Strelow, F W; Victor, A H
1987-04-01
Traces and small amounts of bismuth can be separated from gram amounts of thallium and silver by successively eluting these elements with 0.3M and 0.6M nitric acid from a column containing 13 ml (3 g) of AG50W-X4, a cation-exchanger (100-200 mesh particle size) with low cross-linking. Bismuth is retained and can be eluted with 0.2M hydrobromic acid containing 20% v/v acetone, leaving many other trace elements absorbed. Elution of thallium is quite sharp, but silver shows a small amount of tailing (less than 1 gmg/ml silver in the eluate) when gram amounts are present, between 20 and 80 mug of silver appearing in the bismuth fraction. Relevant elution curves and results for the analysis of synthetic mixtures containing between 50 mug and 10 mg of bismuth and up to more than 1 g of thallium and silver are presented, as well as results for bismuth in a sample of thallium metal and in Merck thallium(I) carbonate. As little as 0.01 ppm of bismuth can be determined when the separation is combined with electrothermal atomic-absorption spectrometry.
9. Characterization, Leaching, and Filtration Testing for Bismuth Phosphate Sludge (Group 1) and Bismuth Phosphate Saltcake (Group 2) Actual Waste Sample Composites
International Nuclear Information System (INIS)
Lumetta, Gregg J.; Buck, Edgar C.; Daniel, Richard C.; Draper, Kathryn; Edwards, Matthew K.; Fiskum, Sandra K.; Hallen, Richard T.; Jagoda, Lynette K.; Jenson, Evan D.; Kozelisky, Anne E.; MacFarlan, Paul J.; Peterson, Reid A.; Shimskey, Rick W.; Sinkov, Sergey I.; Snow, Lanee A.
2009-01-01
A testing program evaluating actual tank waste was developed in response to Task 4 from the M-12 External Flowsheet Review Team (EFRT) issue response plan.() The test program was subdivided into logical increments. The bulk water-insoluble solid wastes that are anticipated to be delivered to the Waste Treatment and Immobilization Plant (WTP) were identified according to type such that the actual waste testing could be targeted to the relevant categories. Eight broad waste groupings were defined. Samples available from the 222S archive were identified and obtained for testing. The actual waste-testing program included homogenizing the samples by group, characterizing the solids and aqueous phases, and performing parametric leaching tests. Two of the eight defined groups - bismuth phosphate sludge (Group 1) and bismuth phosphate saltcake (Group 2) - are the subjects of this report. The Group 1 waste was anticipated to be high in phosphorus and was implicitly assumed to be present as BiPO4 (however, results presented here indicate that the phosphate in Group 1 is actually present as amorphous iron(III) phosphate). The Group 2 waste was also anticipated to be high in phosphorus, but because of the relatively low bismuth content and higher aluminum content, it was anticipated that the Group 2 waste would contain a mixture of gibbsite, sodium phosphate, and aluminum phosphate. Thus, the focus of the Group 1 testing was on determining the behavior of P removal during caustic leaching, and the focus of the Group 2 testing was on the removal of both P and Al. The waste-type definition, archived sample conditions, homogenization activities, characterization (physical, chemical, radioisotope, and crystal habit), and caustic leaching behavior as functions of time, temperature, and hydroxide concentration are discussed in this report. Testing was conducted according to TP-RPP-WTP-467
10. New ternary tantalum borides containing boron dumbbells: Experimental and theoretical studies of Ta{sub 2}OsB{sub 2} and TaRuB
Energy Technology Data Exchange (ETDEWEB)
Mbarki, Mohammed; Touzani, Rachid St.; Rehorn, Christian W.G.; Gladisch, Fabian C. [Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Fokwa, Boniface P.T., E-mail: [email protected] [Institute of Inorganic Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Department of Chemistry, University of California Riverside (UCR), Riverside, CA 92521 (United States)
2016-10-15
The new ternary transition metal-rich borides Ta{sub 2}OsB{sub 2} and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that Ta{sub 2}OsB{sub 2} and TaRuB crystallize in the tetragonal Nb{sub 2}OsB{sub 2} (space group P4/mnc, no. 128) and the orthorhombic NbRuB (space group Pmma, no. 51) structure types with lattice parameters a=5.878(2) Å, c=6.857(2) Å and a=10.806(2) Å, b=3.196(1) Å, c=6.312(2) Å, respectively. Furthermore, crystallographic, electronic and bonding characteristics have been studied by density functional theory (DFT). Electronic structure relaxation has confirmed the crystallographic parameters while COHP bonding analysis indicates that B{sub 2}-dummbells are the strongest bonds in both compounds. Moreover, the formation of osmium dumbbells in Ta{sub 2}OsB{sub 2} through a Peierls distortion along the c-axis, is found to be the origin of superstructure formation. Magnetic susceptibility measurements reveal that the two phases are Pauli paramagnets, thus confirming the theoretical DOS prediction of metallic character. Also hints of superconductivity are found in the two phases, however lack of single phase samples has prevented confirmation. Furthermore, the thermodynamic stability of the two modifications of AMB (A=Nb, Ta; M =Ru, Os) are studied using DFT, as new possible phases containing either B{sub 4}- or B{sub 2}-units are predicted, the former being the most thermodynamically stable modification. - Graphical abstract: The two new ternary tantalum borides, Ta{sub 2}OsB{sub 2} and TaRuB, have been discovered. Their crystal structures contain boron dumbbells, which are the strongest bonds. Peirls distortion is found responsible for Os{sub 2}-dumbbells formation in Ta{sub 2}OsB{sub 2}. Ta{sub 2}OsB{sub 2} and
11. Bismuth adjuvant ameliorates adverse effects of high-dose chemotherapy in patients with multiple myeloma and malignant lymphoma undergoing autologous stem cell transplantation
DEFF Research Database (Denmark)
Hansen, Per Boye; Penkowa, Milena
2017-01-01
show for the first time that bismuth significantly reduces grade 2 stomatitis, febrile neutropenia and infections caused by melphalan in multiple myeloma, where adverse effects also were significantly linked to gender. In lymphoma patients, bismuth significantly reduces diarrhoea relative to placebo......PURPOSE: High-dose chemotherapy prior to autologous stem cell transplantation (ASCT) leads to adverse effects including mucositis, neutropenia and bacteremia. To reduce the toxicity, we treated myeloma and lymphoma patients with peroral bismuth as an adjuvant to chemotherapy to convey...
12. Spectral investigation of highly ionized bismuth plasmas produced by subnanosecond Nd:YAG laser pulses
Science.gov (United States)
Wu, Tao; Higashiguchi, Takeshi; Li, Bowen; Arai, Goki; Hara, Hiroyuki; Kondo, Yoshiki; Miyazaki, Takanori; Dinh, Thanh-Hung; Dunne, Padraig; O'Reilly, Fergal; Sokell, Emma; O'Sullivan, Gerry
2016-02-01
The unresolved transition arrays (UTAs) emitted from laser produced bismuth (Bi) plasma sources show potential for single-shot live cell imaging. We have measured extreme ultraviolet spectra from bismuth laser produced plasmas in the 1-7 nm region using a λ = 1064 nm Nd:YAG laser with a pulse duration of 150 ps. Comparison of spectra obtained under different laser power densities with calculations using the Hartree-Fock with configuration interaction Cowan suite of codes and the UTA formalism, as well as consideration of previous predictions of isoelectronic trends, are employed to identify lines and a number of new features in spectra from Bi XXIII to Bi XLVII. The results show that Δn = 0, n = 4-4 emission from highly charged ions merges to form intense UTAs in the 4 nm region and Δn = 1, n = 4-5 resonance transitions UTAs dominate the 1-3 nm region of the Bi spectrum.
13. The photorefractive characteristics of bismuth-oxide doped lithium niobate crystals
International Nuclear Information System (INIS)
Zheng, Dahuai; Yao, Jiaying; Kong, Yongfa; Liu, Shiguo; Zhang, Ling; Chen, Shaolin; Xu, Jingjun
2015-01-01
Bismuth-doped lithium niobate (LN:Bi) crystals were grown by Czochralski method and their optical damage resistance, photorefraction, absorption spectra, and defect energy levels were investigated. The experimental results indicate that the photorefractive properties of LN:Bi were enhanced as compared with congruent one, the photorefractive response time was greatly shortened, the photorefractive sensitivity was increased, and the diffraction efficiency of near-stoichiometric LN:Bi (SLN:Bi) reached 31.72% and 49.08% at 532 nm and 488 nm laser, respectively (light intensity of 400 mW/cm 2 ). An absorption peak at about 350 nm was observed in the absorption spectrum of LN:Bi. And the defect energy levels simulation indicates new defect levels appear in the forbidden gap of LN:Bi crystals. Therefore bismuth can act as photorefractive centers in LN crystals
14. Evaluation of bismuth shielding effectiveness in reducing breast absorbed dose during thoracic CT scan
Energy Technology Data Exchange (ETDEWEB)
Alonso, T. C.; Mourao, A. P.; Santana, P. C.; Silva, T. A. [Federal University of Minas Gerais, Program of Nuclear Science and Techniques, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil)
2015-10-15
Computed Tomography (CT) is an essential method for tracking neoplasia and efficiently diagnosing a wide variety of thoracic diseases. CT is generally considered the most accurate choice for lung examination. Due to the growing use of CT, breast and other superficial and radiosensitive organs are unnecessarily irradiated during radiological procedures, thus requiring the development of strategies appropriate to optimize and, if possible, to reduce the radiation dose. The use of bismuth shielding to reduce radiation dose absorbed by breast during thoracic CT examinations has been the subject of many studies recently published by Brazilian and foreign authors of various fields. The purpose of this paper is both to accurately determine the glandular dose when breast is exposed to radiation and to assess the reduction in absorbed dose during thoracic CT examinations, using a set of Thermoluminescent Dosimeters, an anthropomorphic phantom and bismuth shielding. (Author)
15. The Role of Bismuth in the Treatment of Gastroduodenal Pathology (Literature Review and Own Researches
Directory of Open Access Journals (Sweden)
Yu.M. Stepanov
2016-09-01
Full Text Available The article presents the history of colloidal bismuth subcitrate and considers the basic mechanisms of its effects on the gastric mucosa, both cytoprotective and anti-helicobacter. The recent data of the worldwide researches are given on the use of the bismuth subcitrate as a component of antibacterial therapy in order to improve the effectiveness of the eradication, especially under the resistance to the basic drugs. The results of own researches are also shown, they are dedicated to the dynamics of structural adjustment of the gastric mucosa in patients with chronic atrophic gastritis for 3 years after the eradication of H.pylori. The use of first-line therapy with the addition of the drug De-Nol allowed to achieve eradication in 94.3 % of patients and positive microstructural changes of the gastric mucosa.
16. Conceptual design of module fast reactor of ultimate safety cooled by lead-bismuth alloy
International Nuclear Information System (INIS)
Myasnikov, V.O.; Stekolnikov, V.V.; Stepanov, V.S.; Gorshkov, V.T.; Kulikov, M.L.; Shulyndin, V.A.; Gromov, B.F.; Kalashnikov, A.G.; Pashkin, Yu.G.
1993-01-01
During past time all basic problems arisen during working-out of NPP with lead-bismuth coolant were solved: physics and thermal physics of the cores, heat transfer and hydrodynamics, corrosion resistance of the structural materials and coolant technology, radiation and nuclear safety, investigations of emergency situations, development of fuel elements and absorbing elements of the reactor, equipment of the primary circuit and other circuits. A powerful experimental base equpped by unique rigs is made. A series of ship and test NPP has been constructed whereat repair of the plants and reactor refuelling are developed. Highly-skilled groups of investigators, designers and operation personnel capable of performing the development of the reactor plant with MFR within short terms have been formed. In this case MFR with lead-bismuth coolant may become the initial step in development of large-scale nuclear power engineering with fast reactors cooled by liquid lead
17. The photorefractive characteristics of bismuth-oxide doped lithium niobate crystals
Energy Technology Data Exchange (ETDEWEB)
Zheng, Dahuai; Yao, Jiaying [School of Physics, Nankai University, Tianjin 300071 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Kong, Yongfa, E-mail: [email protected] [School of Physics, Nankai University, Tianjin 300071 (China); MOE Key Laboratory of Weak-Light Nonlinear Photonics and TEDA Applied Physics School, Nankai University, Tianjin 300457 (China); R and D Center, Taishan Sports Industry Group, Leling 253600 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China); Liu, Shiguo [School of Physics, Nankai University, Tianjin 300071 (China); Zhang, Ling; Chen, Shaolin [MOE Key Laboratory of Weak-Light Nonlinear Photonics and TEDA Applied Physics School, Nankai University, Tianjin 300457 (China); Xu, Jingjun [School of Physics, Nankai University, Tianjin 300071 (China); MOE Key Laboratory of Weak-Light Nonlinear Photonics and TEDA Applied Physics School, Nankai University, Tianjin 300457 (China); Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072 (China)
2015-01-15
Bismuth-doped lithium niobate (LN:Bi) crystals were grown by Czochralski method and their optical damage resistance, photorefraction, absorption spectra, and defect energy levels were investigated. The experimental results indicate that the photorefractive properties of LN:Bi were enhanced as compared with congruent one, the photorefractive response time was greatly shortened, the photorefractive sensitivity was increased, and the diffraction efficiency of near-stoichiometric LN:Bi (SLN:Bi) reached 31.72% and 49.08% at 532 nm and 488 nm laser, respectively (light intensity of 400 mW/cm{sup 2}). An absorption peak at about 350 nm was observed in the absorption spectrum of LN:Bi. And the defect energy levels simulation indicates new defect levels appear in the forbidden gap of LN:Bi crystals. Therefore bismuth can act as photorefractive centers in LN crystals.
18. Rapid synthesis of single-phase bismuth ferrite by microwave-assisted hydrothermal method
Energy Technology Data Exchange (ETDEWEB)
Cao, Wenqian [College of Materials Science and Engineering, China Jiliang University, 258 Xueyuan Street, Xiasha Higher Education District, Hangzhou 310018, Zhejiang Province (China); Chen, Zhi, E-mail: [email protected] [College of Materials Science and Engineering, China Jiliang University, 258 Xueyuan Street, Xiasha Higher Education District, Hangzhou 310018, Zhejiang Province (China); Gao, Tong; Zhou, Dantong; Leng, Xiaonan; Niu, Feng [College of Materials Science and Engineering, China Jiliang University, 258 Xueyuan Street, Xiasha Higher Education District, Hangzhou 310018, Zhejiang Province (China); Zhu, Yuxiang [College of Materials Science and Engineering, China Jiliang University, 258 Xueyuan Street, Xiasha Higher Education District, Hangzhou 310018, Zhejiang Province (China); Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin (China); Qin, Laishun, E-mail: [email protected] [College of Materials Science and Engineering, China Jiliang University, 258 Xueyuan Street, Xiasha Higher Education District, Hangzhou 310018, Zhejiang Province (China); Wang, Jiangying; Huang, Yuexiang [College of Materials Science and Engineering, China Jiliang University, 258 Xueyuan Street, Xiasha Higher Education District, Hangzhou 310018, Zhejiang Province (China)
2016-06-01
This paper describes on the fast synthesis of bismuth ferrite by the simple microwave-assisted hydrothermal method. The phase transformation and the preferred growth facets during the synthetic process have been investigated by X-ray diffraction. Bismuth ferrite can be quickly prepared by microwave hydrothermal method by simply controlling the reaction time, which is further confirmed by Fourier Transform infrared spectroscopy and magnetic measurement. - Graphical abstract: Single-phase BiFeO{sub 3} could be realized at a shortest reaction time of 65 min. The reaction time has strong influences on the phase transformation and the preferred growth facets. - Highlights: • Rapid synthesis (65 min) of BiFeO{sub 3} by microwave-assisted hydrothermal method. • Reaction time has influence on the purity and preferred growth facets. • FTIR and magnetic measurement further confirm the pure phase.
19. Spectral investigation of highly ionized bismuth plasmas produced by subnanosecond Nd:YAG laser pulses
International Nuclear Information System (INIS)
Wu, Tao; Higashiguchi, Takeshi; Arai, Goki; Hara, Hiroyuki; Kondo, Yoshiki; Miyazaki, Takanori; Dinh, Thanh-Hung; Li, Bowen; Dunne, Padraig; O’Reilly, Fergal; Sokell, Emma; O’Sullivan, Gerry
2016-01-01
The unresolved transition arrays (UTAs) emitted from laser produced bismuth (Bi) plasma sources show potential for single-shot live cell imaging. We have measured extreme ultraviolet spectra from bismuth laser produced plasmas in the 1–7 nm region using a λ = 1064 nm Nd:YAG laser with a pulse duration of 150 ps. Comparison of spectra obtained under different laser power densities with calculations using the Hartree–Fock with configuration interaction Cowan suite of codes and the UTA formalism, as well as consideration of previous predictions of isoelectronic trends, are employed to identify lines and a number of new features in spectra from Bi XXIII to Bi XLVII. The results show that Δn = 0, n = 4–4 emission from highly charged ions merges to form intense UTAs in the 4 nm region and Δn = 1, n = 4–5 resonance transitions UTAs dominate the 1–3 nm region of the Bi spectrum. (paper)
20. High precision hyperfine measurements in Bismuth challenge bound-state strong-field QED.
Science.gov (United States)
Ullmann, Johannes; Andelkovic, Zoran; Brandau, Carsten; Dax, Andreas; Geithner, Wolfgang; Geppert, Christopher; Gorges, Christian; Hammen, Michael; Hannen, Volker; Kaufmann, Simon; König, Kristian; Litvinov, Yuri A; Lochmann, Matthias; Maaß, Bernhard; Meisner, Johann; Murböck, Tobias; Sánchez, Rodolfo; Schmidt, Matthias; Schmidt, Stefan; Steck, Markus; Stöhlker, Thomas; Thompson, Richard C; Trageser, Christian; Vollbrecht, Jonas; Weinheimer, Christian; Nörtershäuser, Wilfried
2017-05-16
Electrons bound in highly charged heavy ions such as hydrogen-like bismuth 209 Bi 82+ experience electromagnetic fields that are a million times stronger than in light atoms. Measuring the wavelength of light emitted and absorbed by these ions is therefore a sensitive testing ground for quantum electrodynamical (QED) effects and especially the electron-nucleus interaction under such extreme conditions. However, insufficient knowledge of the nuclear structure has prevented a rigorous test of strong-field QED. Here we present a measurement of the so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like bismuth 209 Bi 82+,80+ with a precision that is improved by more than an order of magnitude. Even though this quantity is believed to be largely insensitive to nuclear structure and therefore the most decisive test of QED in the strong magnetic field regime, we find a 7-σ discrepancy compared with the theoretical prediction.
1. Bismuth Basic Nitrate as a Novel Adsorbent for Azo Dye Removal
Directory of Open Access Journals (Sweden)
E. A. Abdullah
2012-01-01
Full Text Available Bismuth basic nitrate (BBN and its TiO2-Ag modified sorbent, PTBA were successfully synthesized via a precipitation method. The structural characteristics of prepared sorbents were determined through different analytical techniques. The potential use of prepared sorbents for organic compounds' removal was evaluated using Methyl Orange and Sunset Yellow dyes as model pollutants in aqueous solutions. The experimental results showed that the presence of TiO2 and Ag particles during the crystal growth of bismuth basic nitrate has an effect on the crystal structure, point of zero charge (pHpzc, pore volume and diameter. The lower binding energy of Ti 2p core level peak indicates the octahedral coordination of TiO2 particles on the PTBA surface. The alteration of hydrophilic-hydrophobic characteristics of sorbent's surface improves the adsorptive performance of the modified sorbent and provides an efficient route for organic contaminants' removal from aqueous solutions.
2. Evaluation of bismuth shielding effectiveness in reducing breast absorbed dose during thoracic CT scan
International Nuclear Information System (INIS)
Alonso, T. C.; Mourao, A. P.; Santana, P. C.; Silva, T. A.
2015-10-01
Computed Tomography (CT) is an essential method for tracking neoplasia and efficiently diagnosing a wide variety of thoracic diseases. CT is generally considered the most accurate choice for lung examination. Due to the growing use of CT, breast and other superficial and radiosensitive organs are unnecessarily irradiated during radiological procedures, thus requiring the development of strategies appropriate to optimize and, if possible, to reduce the radiation dose. The use of bismuth shielding to reduce radiation dose absorbed by breast during thoracic CT examinations has been the subject of many studies recently published by Brazilian and foreign authors of various fields. The purpose of this paper is both to accurately determine the glandular dose when breast is exposed to radiation and to assess the reduction in absorbed dose during thoracic CT examinations, using a set of Thermoluminescent Dosimeters, an anthropomorphic phantom and bismuth shielding. (Author)
3. Analysis of lenses absorbed dose in head CT scan with the use of bismuth shielding
Energy Technology Data Exchange (ETDEWEB)
Santos, F.S.; Santana, P.C., E-mail: [email protected] [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (Brazil); Mourão, A.P. [Centro de Educação Tecnológica de Minas Gerais (CEFET-MG), Belo Horizonte, MG (Brazil)
2017-07-01
Computed Tomography (CT) has become an important tool to diagnose cancer and to obtain additional information for different clinical questions. However, CT scan usually requires a higher radiation exposure than a conventional radiography examination. Head CT scans are used for diagnosis of traumatic head injuries, infections and other diseases with instability. Based on this information, it was studied the dose variation deposited in the lenses and in nearby organs, such as: pharynx, hypophysis and salivary gland with and without the use of bismuth shield. In this study a head CT scan was performed on anthropomorphic male phantom using a GE scanner. Dose measurements have been performed by using radiochromic film strips to register the individual doses in the organs of interest. The results show that the lenses had a reduction of 26% of the dose with the use of the bismuth shield. (author)
4. Rapid synthesis of single-phase bismuth ferrite by microwave-assisted hydrothermal method
International Nuclear Information System (INIS)
Cao, Wenqian; Chen, Zhi; Gao, Tong; Zhou, Dantong; Leng, Xiaonan; Niu, Feng; Zhu, Yuxiang; Qin, Laishun; Wang, Jiangying; Huang, Yuexiang
2016-01-01
This paper describes on the fast synthesis of bismuth ferrite by the simple microwave-assisted hydrothermal method. The phase transformation and the preferred growth facets during the synthetic process have been investigated by X-ray diffraction. Bismuth ferrite can be quickly prepared by microwave hydrothermal method by simply controlling the reaction time, which is further confirmed by Fourier Transform infrared spectroscopy and magnetic measurement. - Graphical abstract: Single-phase BiFeO_3 could be realized at a shortest reaction time of 65 min. The reaction time has strong influences on the phase transformation and the preferred growth facets. - Highlights: • Rapid synthesis (65 min) of BiFeO_3 by microwave-assisted hydrothermal method. • Reaction time has influence on the purity and preferred growth facets. • FTIR and magnetic measurement further confirm the pure phase.
5. Formation of planar waveguides in bismuth germanate by 4He+ ion implantation
International Nuclear Information System (INIS)
Mahdavi, S.M.; Chandler, P.J.; Townsend, P.D.
1989-01-01
Planar optical waveguides have been formed in crystalline bismuth germanate (BGO) Bi 4 Ge 3 O 12 , by He + ion implantation. The refractive index profiles have been determined using a dark-mode technique at 0.6328 and 0.488 micrometres. In the region of the electronic and nuclear stopping power of the ion beam in bismuth germanate there is an index enhancement, which forms an optical 'well', This is stable up to ∼ 200 0 C, but then there is a gradual recovery of index up to 400 0 C. Between 425 and 450 0 C, for heavily implanted samples (≥4 x 10 16 ions/cm 2 ), the well rapidly disappears, and is replaced by a sharp 'barrier' of reduced index. For lower dose implants ( 16 ion/cm 2 ) at 450 0 C many of the modes disappear without being replaced by a sharp barrier. (author)
6. The study of the sample size on the transverse magnetoresistance of bismuth nanowires
International Nuclear Information System (INIS)
2012-01-01
The effects of sample size on the galvanomagnetice properties of semimetal nanowires are theoretically investigated. Transverse magnetoresistance (TMR) ratios have been calculated within a Boltzmann Transport Equation (BTE) approach by specular reflection approximation. Temperature and radius dependence of the transverse magnetoresistance of cylindrical Bismuth nanowires are given. The obtained values are in good agreement with the experimental results, reported by Heremans et al. - Highlights: ► In this study effects of sample size on the galvanomagnetic properties of Bi. ► Nanowires were explained by Parrott theorem by solving the Boltzmann Transport Equation. ► Transverse magnetoresistance (TMR) ratios have been measured by specular reflection approximation. ► Temperature and radius dependence of the transverse magnetoresistance of cylindrical Bismuth nanowires are given. ► The obtained values are in good agreement with the experimental results, reported by Heremans et al.
7. Role of Bismuth in the Electrokinetics of Silicon Photocathodes for Solar Rechargeable Vanadium Redox Flow Batteries.
Science.gov (United States)
Flox, Cristina; Murcia-López, Sebastián; Carretero, Nina M; Ros, Carles; Morante, Juan R; Andreu, Teresa
2018-01-10
The ability of crystalline silicon to photoassist the V 3+ /V 2+ cathodic reaction under simulated solar irradiation, combined with the effect of bismuth have led to important electrochemical improvements. Besides the photovoltage supplied by the photovoltaics, additional decrease in the onset potentials, high reversibility of the V 3+ /V 2+ redox pair, and improvement in the electrokinetics were attained thanks to the addition of bismuth. In fact, Bi 0 deposition has shown to slightly decrease the photocurrent, but the significant enhancement in the charge transfer, reflected in the overall electrochemical performance clearly justifies its use as additive in a photoassisted system for maximizing the efficiency of solar charge to battery. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
8. Graphite felt modified with bismuth nanoparticles as negative electrode in a vanadium redox flow battery.
Science.gov (United States)
Suárez, David J; González, Zoraida; Blanco, Clara; Granda, Marcos; Menéndez, Rosa; Santamaría, Ricardo
2014-03-01
A graphite felt decorated with bismuth nanoparticles was studied as negative electrode in a vanadium redox flow battery (VRFB). The results confirm the excellent electrochemical performance of the bismuth modified electrode in terms of the reversibility of the V(3+) /V(2+) redox reactions and its long-term cycling performance. Moreover a mechanism that explains the role that Bi nanoparticles play in the redox reactions in this negative half-cell is proposed. Bi nanoparticles favor the formation of BiHx , an intermediate that reduces V(3+) to V(2+) and, therefore, inhibits the competitive irreversible reaction of hydrogen formation (responsible for the commonly observed loss of Coulombic efficiency of VRFBs). Thus, the total charge consumed during the cathodic sweep in this electrode is used to reduce V(3+) to V(2+) , resulting in a highly reversible and efficient process. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
9. Interlayer interactions in absorption and reflection spectra of bismuth HTSC crystals
International Nuclear Information System (INIS)
Kruchinin, S.P.; Yaremko, A.M.
1992-01-01
The HTSC reflection and absorption optic spectra peculiarities are analysed in the paper on the basis of bismuth and thallium. The approach suggested takes into account the complex character of crystals structure, possible localization of excitations in the isolated layers and further excitations exchange due to the interlayer interaction between cuprate (Cu O) and quasi-degenerate bismuth layers (Bi O/3pO). The expressions for the excitation and intensity energies of the corresponding transitions are obtained. It is shown that only part of excitations whose number is determined by the number of layers in the unit cell will be manifest in optical reflection and absorption spectra. The experimental results on spectral dependence of crystal reflection coefficients are analysed
10. Evidence for a temperature-driven structural transformation in liquid bismuth
International Nuclear Information System (INIS)
Greenberg, Y.; Dariel, M.P.; Greenberg, Y.; Yahel, E.; Caspi, E.N.; Makov, G.; Benmore, C.; Beuneu, B.
2009-01-01
The thermodynamic properties of liquid bismuth have been explored from the melting point to 1100 C degrees by high-resolution measurements of the density, the heat capacity and the static structure factor. These physical properties display a number of anomalies. In particular, we have observed evidence for the presence of a temperature-driven liquid-liquid structural transformation that takes place at ambient pressure. The latter is characterized by a density discontinuity that occurs at 740 C degrees. Differential thermal analysis measurements revealed the endo-thermal nature of this transformation. A rearrangement of liquid bismuth structure was found by neutron diffraction measurements, supporting the existence of a liquid-liquid transformation far above the liquidus. (authors)
11. Mixed-layered bismuth--oxygen--iodine materials for capture and waste disposal of radioactive iodine
Science.gov (United States)
Krumhansl, James L; Nenoff, Tina M
2015-01-06
Materials and methods of synthesizing mixed-layered bismuth oxy-iodine materials, which can be synthesized in the presence of aqueous radioactive iodine species found in caustic solutions (e.g. NaOH or KOH). This technology provides a one-step process for both iodine sequestration and storage from nuclear fuel cycles. It results in materials that will be durable for repository conditions much like those found in Waste Isolation Pilot Plant (WIPP) and estimated for Yucca Mountain (YMP). By controlled reactant concentrations, optimized compositions of these mixed-layered bismuth oxy-iodine inorganic materials are produced that have both a high iodine weight percentage and a low solubility in groundwater environments.
12. Mixed-layered bismuth-oxygen-iodine materials for capture and waste disposal of radioactive iodine
Science.gov (United States)
Krumhansl, James L; Nenoff, Tina M
2013-02-26
Materials and methods of synthesizing mixed-layered bismuth oxy-iodine materials, which can be synthesized in the presence of aqueous radioactive iodine species found in caustic solutions (e.g. NaOH or KOH). This technology provides a one-step process for both iodine sequestration and storage from nuclear fuel cycles. It results in materials that will be durable for repository conditions much like those found in Waste Isolation Pilot Plant (WIPP) and estimated for Yucca Mountain (YMP). By controlled reactant concentrations, optimized compositions of these mixed-layered bismuth oxy-iodine inorganic materials are produced that have both a high iodine weight percentage and a low solubility in groundwater environments.
13. Structure and magnetic properties of the 3d transition-metal mono-borides TM–B (TM=Mn, Fe, Co) under pressures
International Nuclear Information System (INIS)
Bourourou, Y.; Beldi, L.; Bentria, B.; Gueddouh, A.; Bouhafs, B.
2014-01-01
In this paper, spin-polarization and pressure effects on the structural and electronic properties of the 3d transition-metal mono-borides TM–B (TM=Mn, Fe, Co) have been studied by using both local spin-density approximation (LSDA) and generalized gradient approximation (GGA) within the framework of density-functional theory (DFT). At equilibrium, spin-polarization calculations show that MnB and FeB compounds carry magnetic moment. The non-spin-polarization results show that the non-magnetic state is unstable for MnB and FeB compounds, but a stable non-magnetic phase for CoB compound, which is discussed in the framework of the well-known Stoner criterion. The calculated lattice parameters, bulk moduli, their first-pressure derivatives and magnetic moments agree well with experimental and other theoretical results. Significant differences in volume and in bulk modulus were found between the magnetic and non-magnetic case reached 4%, 22%, respectively. The effect of pressure on the crystal structure reflects in a compression of the unit cell volume with a decreasing in the magnetic moment. The density of states of MnB and FeB ferromagnetic compounds are significantly modified under high pressures. The exchange energy decreases with increasing pressure, at approximately V/V 0 =0.6, the exchange energy becomes absent in ferromagnetic compounds causes mirror in upper and lowers half panels. Finally, we notice that spin-polarization and pressure play a crucially important role in determining the electronic and structural properties of 3d transition-metal mono-borides. - Highlights: • Spin polarization and pressure effects on TM–B (TM=Mn, Fe, Co) have been investigated. • The non-spin-polarization results show that the non-magnetic state is stable for CoB. • The magnetic states of MnB and FeB are found more stable than their nonmagnetic states. • We report significant differences between the magnetic and non-magnetic cases. • The density of states of MnB and
14. Electronic, structural and magnetic studies of niobium borides of group 8 transition metals, Nb2MB2 (M=Fe, Ru, Os) from first principles calculations
International Nuclear Information System (INIS)
Touzani, Rachid St.; Fokwa, Boniface P.T.
2014-01-01
The Nb 2 FeB 2 phase (U 3 Si 2 -type, space group P4/mbm, no. 127) is known for almost 50 years, but until now its magnetic properties have not been investigated. While the synthesis of Nb 2 OsB 2 (space group P4/mnc, no. 128, a twofold superstructure of U 3 Si 2 -type) with distorted Nb-layers and Os 2 -dumbbells was recently achieved, “Nb 2 RuB 2 ” is still not synthesized and its crystal structure is yet to be revealed. Our first principles density functional theory (DFT) calculations have confirmed not only the experimental structures of Nb 2 FeB 2 and Nb 2 OsB 2 , but also predict “Nb 2 RuB 2 ” to crystalize with the Nb 2 OsB 2 structure type. According to chemical bonding analysis, the homoatomic B–B interactions are optimized and very strong, but relatively strong heteroatomic M–B, B–Nb and M–Nb bonds (M=Fe, Ru, Os) are also found. These interactions, which together build a three-dimensional network, are mainly responsible for the structural stability of these ternary borides. The density-of-states at the Fermi level predicts metallic behavior, as expected, from metal-rich borides. Analysis of possible magnetic structures concluded preferred antiferromagnetic ordering for Nb 2 FeB 2 , originating from ferromagnetic interactions within iron chains and antiferromagnetic exchange interactions between them. -- Graphical abstract: Nb 2 FeB 2 (U 3 Si 2 structure type, space group P4/mbm, no. 127) is predicted to order antiferromagnetically, due to the presence of iron chains which show ferromagnetic interactions in the chains and antiferromagnetic interactions between them. “Nb 2 RuB 2 ” is predicted to crystallize with the recently discovered Nb 2 OsB 2 twofold superstructure (space group P4/mnc, no. 128) of U 3 Si 2 structure type. The building of ruthenium dumbbells instead of chains along [001] is found to be responsible for the stabilization of this superstructure. Highlights: • Nb 2 FeB 2 is predicted to order antiferromagnetically.
15. Report - Melter Testing of New High Bismuth HLW Formulations VSL-13R2770-1
Energy Technology Data Exchange (ETDEWEB)
Kruger, Albert A.; Pegg, I. L.; Kot, W. K.; Gan, H.; Matlack, K. S.
2013-11-13
The primary objective of the work described was to test two glasses formulated for a high bismuth waste stream on the DM100 melter system. Testing was designed to determine processing characteristics and production rates, assess the tendency for foaming, and confirm glass properties. The glass compositions tested were previously developed to maintain high waste loadings and processing rates while suppressing the foaming observed in previous tests
16. A circulating loop tester for liquid alloyed metal of lead-bismuth
International Nuclear Information System (INIS)
Kitano, Teruaki; Ono, Mikinori; Kamata, Kinya
2002-01-01
Mitsui Engineering and Shipbuilding Co., Ltd. (MES) had focused to merits of this lead-bismuth alloy, to actively carry out many works on this field such as an experience of development of heat exchanger at industrial level of intercourse with IPPE (Institute of Physics and Power Engineering) in Russia with an experience of using results for 80 years on coolant for nuclear reactor. Before about 20 years, MES developed a heat exchanger for installation at a lead-zinc separation process in a refinery in Japan under cooperation of the Mitsui Metal and Mine Co., Ltd., to deliver it for a power generation system at the Hachinohe refinery. As the heat exchanger aims at control of cooling in the separation process, it also contributes to power generation of about 4,300 kW, and now it continues to separate and contribute to self-power generation in the refinery. The heat exchanger is filled with the liquid alloyed metal of lead-bismuth for an intermediate thermal medium in its casing. The metal has some merits such as inactivity to air and water, high boiling point (1,700 centigrade), almost no volume change at its coagulation, and its minus reactivity coefficient. However, the metal has some problems to be solved, such as its steel corrosion, its purification, and control technology. To grow up lead-bismuth technology to a nuclear energy technology in Japan, the lead-bismuth circulating loop tester was produced on May, 2001, to establish application technology on this system to nuclear energy technology in Japan. (G.K.)
17. Effect of bismuth addition to the triple therapy of Helicobacter pylori eradication
Directory of Open Access Journals (Sweden)
Ezel Taşdemir
2012-03-01
Full Text Available Objective: Success rates of amoxicillin, clarithromycin, and proton-pump inhibitor therapy in the Helicobacter pylori (Hp eradication have been decreasing. The aim of this study was to investigate the impact of bismuth subcitrate addition to triple therapy.Materials and methods: 148 patients diagnosed Hp infection with both histology and Hp stool antigen (HpSA tests were examined retrospectively. The patients were divided into 3 groups according to the eradication therapy. The first group received triple therapy with claritromycine 2x 500 mg, amoxicilline 2x1 g and PPI 2x1 for 14 days (n=40. The second group had bismuth subcitrate 4x120 mg with triple therapy for 14 days (n=73. The third group received 14 days pretreatment with bismuth subcitrate 4x1 together with PPI 2x1 then had triple therapy for 14 days (n=35. (14C urea breath and HpSA tests were used to detect posttreatment H.pylori status.Results: There were no statistical difference between the groups in terms of gender and age (p > 0.05. In group one 12 patients, in group two 20 patients and in group three 10 patients were identified as Hp positive after treatment. Eradication rates were 70% for group one, 72.6% for group two and 71.4% for group three respectively. There was no statistical difference between the groups in terms of eradication rates of treatment (p > 0.05.Conclusions: The addition of bismuth to conventional triple therapy did not affect treatment success rates.
18. Study of some health physics parameters of bismuth-ground granulated blast furnace slag shielding concretes
Energy Technology Data Exchange (ETDEWEB)
Kumar, Sandeep, E-mail: [email protected] [Department of Physics, Punjabi University, Patiala (India); Singh, Sukhpal, E-mail: [email protected] [Department of Basic and Applied Sciences, Punjabi University, Patiala (India)
2016-05-06
The Bismuth-ground granulated blastfurnace slang (Bi-GGBFS) concrete samples were prepared. The weight percentage of different elements present in Bi-GGBFS Shielding concretewas evaluated by Energy Dispersive X-ray Microanalysis (EDX). The exposure rate and absorbed dose rate characteristics were calculated theoretically for radioactive sources namely {sup 241}Am and {sup 137}Cs. Our calculations reveal that the Bi-GGBFS concretes are effective in shielding material for gamma radiations.
19. Study of some health physics parameters of bismuth-ground granulated blast furnace slag shielding concretes
Science.gov (United States)
Kumar, Sandeep; Singh, Sukhpal
2016-05-01
The Bismuth-ground granulated blastfurnace slang (Bi-GGBFS) concrete samples were prepared. The weight percentage of different elements present inBi-GGBFS Shielding concretewas evaluated by Energy Dispersive X-ray Microanalysis (EDX). The exposure rate and absorbed dose rate characteristics were calculated theoretically for radioactive sources namely 241Am and 137Cs. Our calculations reveal that the Bi-GGBFS concretes are effective in shielding material for gamma radiations.
20. Large-scale synthesis of bismuth sulfide nanorods by microwave irradiation
International Nuclear Information System (INIS)
Wu Jiliang; Qin Fan; Cheng Gang; Li Hui; Zhang Jiuhong; Xie Yaoping; Yang Haijian; Lu Zhong; Yu Xianglin; Chen Rong
2011-01-01
Graphical abstract: Display Omitted Research highlights: → Large-scale Bi 2 S 3 nanorods have been prepared by microwave irradiation methods. → CTAB and β-CD are beneficial to the formation of Bi 2 S 3 nanorods. → DMF, EG and DEG were favorable solvents. → Bismuth and sulfur precursors influenced the size and morphology. → A proposed formation mechanism of Bi 2 S 3 nanorods was summarized. - Abstract: Bismuth sulfide (Bi 2 S 3 ) has attracted considerable interest due to its potential applications in thermoelectric and electronic devices, optoelectronic devices, and biomedicine. In this study, large-scale highly crystalline Bi 2 S 3 nanorods were successfully prepared from bismuth citrate and thiourea (Tu) by microwave irradiation methods. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM, HRTEM) and selected area electron diffraction (SAED). The influences of reaction time, surfactants, solvents, and precursors on the formation of Bi 2 S 3 nanorods were discussed. The microwave irradiation method reduced reaction time by at least 80% in the synthesis of Bi 2 S 3 nanorods compared with the refluxing method. Cetyltrimethylammonium bromide (CTAB) and β-cyclodextrin (β-CD) were found to be beneficial to the formation of Bi 2 S 3 nanorods. N,N-dimethylformamide, ethylene glycol, and diethylene glycol were the favorable solvents in the fabrication of these nanorods. It was found that different bismuth and sulfur precursors influenced the sizes and morphologies of the Bi 2 S 3 nanorods. The proposed growth mechanism of Bi 2 S 3 nanorods was also discussed.
1. Determination of the two-loop Lamb shift in lithiumlike bismuth
International Nuclear Information System (INIS)
Sapirstein, J.; Cheng, K. T.
2001-01-01
The energy levels of lithiumlike bismuth are shown to be accurately described in a representation-independent manner when all diagrams involving one and two photons, with the exception of the two-loop Lamb shift, are evaluated. Comparison with the experimental value of the 2p 3/2 -2s 1/2 splitting then shows that, assuming three-photon effects are negligible, the contribution of the two-loop Lamb shift is 0.175(39) eV
2. Bismuth Infusion of ABS Enables Additive Manufacturing of Complex Radiological Phantoms and Shielding Equipment
Directory of Open Access Journals (Sweden)
Justin Ceh
2017-02-01
3. Donor impurity self-compensation by neutral complexes in bismuth doped lead telluride
International Nuclear Information System (INIS)
Ravich, Yu.I.; Nemov, S.A.; Proshin, V.I.
1994-01-01
Self-compensation is calculated of impurity doping action in semiconductors of the A 4 B 6 type by neutral complexes, consisting of a vacancy and two impurity atoms. Complexes entropy is estimated and the thermodynamic potential is minimized in the concentration of single two-charge vacancies and complexes. Calculation results are compared with experimental data, obtained when lead telluride doping by bismuth. Account for complex formation improves agreement theory with experiment. 4 refs., 1 fig
4. Ultrasonic and Thermal Properties of Borate and Phosphate Glasses Containing Bismuth and Lead
International Nuclear Information System (INIS)
Aziz, Sidek Hj. Abd.; Ahmad, Hamezan; Wahab, Zaidan A.; Sulaiman, Zainal Abidin; Talib, Zainal Abidin; Shaari, A. Halim; Senin, H. B.
2007-01-01
Systematic series of (B2O3,P2O5)-Bi2O3-PbO glasses have been successfully prepared by using the rapid quenching technique in which each oxide content changes for every series on the basis of its weight percentage. Their amorphous natures were confirmed earlier by the x-ray diffraction technique. The experimental results show that the density of both glasses, determined by using the Archimedes principle, increases with the glass modifier content. This is due to the replacement of Bi2O3 and PbO in the borate and phosphate glassy networks. The molar volume for borate glass increases with the addition of bismuth and lead oxides, but a reverse trend occurs for the phosphate glass. The longitudinal and shear ultrasound velocities, determined by the MBS 8000 system, of both lead bismuth borate and phosphate glasses show a decreasing trend as more PbO and Bi2O3 are added to the glass system. The increase in PbO/Bi2O3 content was probably related to the progressive increase in the concentration of non-bridging oxygen (NBOs). Thermal studies of the glass, using the Labsys DTA-Setaram machine, show that the value of the glass transition temperature (Tg) is closely related to the chemical bond in the system. In lead bismuth borate glasses, the addition of more Pb2+ and Bi3+ results in a more dominant ionic bond character in the system and hence decreases Tg of the sample. However, in lead bismuth phosphate glasses, the addition of Pb2+ and Bi3+ not only failed to weaken the covalent character in P-O-P bonds, but strengthened it further, leading to an increment in the values of Tg
5. Systematics of c-axis phonons in the thallium- and bismuth-based cuprate superconductors
NARCIS (Netherlands)
Tsvetkov, A.A.; Dulic, Diana; Marel, D. van der; Damascelli, A.; Kaljushnaia, G.A.; Gorina, J.I.; Senturina, N.N.; Kolesnikov, N.N.; Ren, Z.F.; Wang, J.H.; Menovsky, A.A.; Palstra, T.T.M.
1999-01-01
We present grazing incidence reflectivity measurements in the far-infrared region at temperatures above and below Tc for a series of thallium- (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth- (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi2-xPbxSr2CaCu2O8) based cuprate superconductors. From the spectra, which are
6. Eye-lens bismuth shielding in paediatric head CT: artefact evaluation and reduction
International Nuclear Information System (INIS)
Raissaki, Maria; Perisinakis, Kostas; Damilakis, John; Gourtsoyiannis, Nicholas
2010-01-01
CT scans of the brain, sinuses and petrous bones performed as the initial imaging test for a variety of indications have the potential to expose the eye-lens, considered among the most radiosensitive human tissues, to a radiation dose. There are several studies in adults discussing the reduction of orbital dose resulting from the use of commercially available bismuth-impregnated latex shields during CT examinations of the head. To evaluate bismuth shielding-induced artefacts and to provide suggestions for optimal eye-lens shielding in paediatric head CT. A bismuth shield was placed over the eyelids of 60 consecutive children undergoing head CT. Images were assessed for the presence and severity of artefacts with regard to eye-shield distance and shield wrinkling. An anthropomorphic paediatric phantom and thermoluminescence dosimeters (TLDs) were used to study the effect of eye lens-to-shield distance on shielding efficiency. Shields were tolerated by 56/60 children. Artefacts were absent in 45% of scans. Artefacts on orbits, not affecting and affecting orbit evaluation were noted in 39% and 14% of scans, respectively. Diagnostically insignificant artefacts on intracranial structures were noted in 1 case (2%) with shield misplacement. Mean eye-lens-to-shield distance was 8.8 mm in scans without artefacts, and 4.3 mm and 2.2 mm in scans with unimportant and diagnostically important artefacts, respectively. Artefacts occurred in 8 out of 9 cases with shield wrinkling. Dose reduction remained unchanged for different shield-to-eye distances. Bismuth shielding-related artefacts occurring in paediatric head CT are frequent, superficial and diagnostically insignificant when brain pathology is assessed. Shields should be placed 1 cm above the eyes when orbital pathology is addressed. Shield wrinkling should be avoided. (orig.)
OpenAIRE
2017-01-01
Background: The use and effectiveness of traditional lead gonad shields in pediatric pelvic radiography has been challenged by several literatures over the past two decades. The aim of this study was to develop a new radioprotective gonad shields to be use in pediatric pelvic radiography. Materials and Methods: The commercially available 0.06 mm lead equivalent bismuth garment has cropped squarely and used as ovarian shield to cover the entire region of pelvis. In order to prevent deteriorati...
8. Study of some health physics parameters of bismuth-ground granulated blast furnace slag shielding concretes
International Nuclear Information System (INIS)
Kumar, Sandeep; Singh, Sukhpal
2016-01-01
The Bismuth-ground granulated blastfurnace slang (Bi-GGBFS) concrete samples were prepared. The weight percentage of different elements present in Bi-GGBFS Shielding concretewas evaluated by Energy Dispersive X-ray Microanalysis (EDX). The exposure rate and absorbed dose rate characteristics were calculated theoretically for radioactive sources namely "2"4"1Am and "1"3"7Cs. Our calculations reveal that the Bi-GGBFS concretes are effective in shielding material for gamma radiations.
9. Technical tutorial: How to pack a nose with bismuth iodoform paraffin paste gauze safely and effectively.
Science.gov (United States)
Amen, F; Pace-Balzan, A
2009-01-01
The current primary treatment for epistaxis in accident and emergency departments is the insertion of Merocel packs. If these are properly inserted, but fail to control bleeding, it is necessary to insert a bismuth iodoform paraffin paste (BIPP) pack. A BIPP pack, when properly inserted, has the potential to stop most bleeds, but books and journals suggest a method of insertion that limits its effectiveness. A safer and more effective way of packing a nose with BIPP than the traditional method is described.
10. Effect of Gamma Irradiation on Some Properties of Bismuth Silicate Glasses and Their Glass Derivatives
International Nuclear Information System (INIS)
Abo Hussein, E.M.K.
2014-01-01
Glasses containing bismuth oxide have attracted considerable attention, although it is non-conventional glass forming oxide, but it has wide applications. In this work, it is aimed to prove that bismuth silicate glass can act as a good shielding material for γ- rays. For this purpose glass containing 20% bismuth oxide and 80% SiO_2 was prepared using melting-annealing technique. Also effects of adding some alkali heavy metal oxides to this glass such as PbO, BaO or SrO were also studied. The formed glasses were also heat treated at 450 degree C for 4 hours to give the corresponding heat treated glasses. Electron Paramagnetic Resonance (EPR) measurements show that the prepared glasses and heat treated glasses have very good stability when exposed to γ- irradiation, which encourage the assumption of using these glasses as gamma ray shielding materials. Many properties have been investigated, such as density to understand the structural properties, also mechanical properties were verified by measuring microhardness, while the chemical resistance was identified by testing their durability in both acidic and basic solutions. The EPR results were supported by measuring electrical conductivity of the glass and heat treated glass samples at different temperatures ranging from 298 to 553 K, which proved that these glasses have very low conductivity even at high temperature. The formed phases of heat treated glass or glass ceramic samples were demonstrated by means of X-ray diffraction (XRD). Also studying the structure of glasses and heat treated glasses before and after irradiation was investigated by the Infrared transmitting spectra. Calculations of optical band gap energies were demonstrated for some selected glasses and heat treated glasses from the data of UV optical absorption spectra to support the probability of using these bismuth silicate glasses for gamma radiation shielding processing.
11. Analysis of the color alteration and radiopacity promoted by bismuth oxide in calcium silicate cement.
Science.gov (United States)
Marciano, Marina Angélica; Estrela, Carlos; Mondelli, Rafael Francisco Lia; Ordinola-Zapata, Ronald; Duarte, Marco Antonio Hungaro
2013-01-01
The aim of the study was to determine if the increase in radiopacity provided by bismuth oxide is related to the color alteration of calcium silicate-based cement. Calcium silicate cement (CSC) was mixed with 0%, 15%, 20%, 30% and 50% of bismuth oxide (BO), determined by weight. Mineral trioxide aggregate (MTA) was the control group. The radiopacity test was performed according to ISO 6876/2001. The color was evaluated using the CIE system. The assessments were performed after 24 hours, 7 and 30 days of setting time, using a spectrophotometer to obtain the ΔE, Δa, Δb and ΔL values. The statistical analyses were performed using the Kruskal-Wallis/Dunn and ANOVA/Tukey tests (poxide was added showed radiopacity corresponding to the ISO recommendations (>3 mm equivalent of Al). The MTA group was statistically similar to the CSC/30% BO group (p>0.05). In regard to color, the increase of bismuth oxide resulted in a decrease in the ΔE value of the calcium silicate cement. The CSC group presented statistically higher ΔE values than the CSC/50% BO group (poxide has no relation to the color alteration of calcium silicate-based cements.
12. Performance of solid electrolyte type oxygen sensor in flowing lead bismuth
International Nuclear Information System (INIS)
Kondo, Masatoshi; Takahashi, Minoru
2005-01-01
A solid electrolyte type oxygen sensor for liquid 45%lead-55%bismuth (Pb-Bi) was developed. The performance of the oxygen sensor in the flowing lead-bismuth (Pb-Bi) was investigated. The initial performance of the sensor was not reliable, since the reference fluid of the oxygen saturated bismuth in the sensor cell was not compact initially. The electromotive force (EMF) obtained from the yttria stabilized zirconia (YSZ) cell was the same as that from the magnesia stabilized zirconia (MSZ) cell in the flowing Pb-Bi. The EMF of the sensor in the flowing Pb-Bi was lower than that in the stagnant Pb-Bi. However, the difference was small. The sensor showed repeatability after the long term interruption and the Pb-Bi drain/charge operation. After the performance tests, the corrosion of the sensor cells were investigated metallurgically. The YSZ cell was eroded around the free surface of the flowing Pb-Bi after 3500 hour-exposure in the flowing Pb-Bi. The MSZ cell showed smooth surface without the erosion. Although the YSZ cell worked more stably than the MSZ cell, the mechanical strength of the YSZ cell is weaker than that of the MSZ cell. (author)
13. Behaviour of F82H mod. stainless steel in lead-bismuth under temperature gradient
Science.gov (United States)
Gómez Briceño, D.; Martín Muñoz, F. J.; Soler Crespo, L.; Esteban, F.; Torres, C.
2001-07-01
Austenitic steels can be used in a hybrid system in contact with liquid lead-bismuth eutectic if the region of operating temperatures is not beyond 400°C. For higher temperatures, martensitic steels are recommended. However, at long times, the interaction between the structural material and the eutectic leads to the dissolution of some elements of the steel (Ni, Cr and Fe, mainly) in the liquid metal. In a non-isothermal lead-bismuth loop, the material dissolution takes place at the hot leg of the circuit and, due to the mass transfer, deposition occurs at the cold leg. One of the possible ways to improve the performance of structural materials in lead-bismuth is the creation of an oxide layer. Tests have been performed in a small natural convection loop built of austenitic steel (316L) that has been operating for 3000 h. This loop contains a test area in which several samples of F82Hmod. martensitic steel have been tested at different times. A gas with an oxygen content of 10 ppm was bubbled in the hot area of the circuit during the operation time. The obtained results show that an oxide layer is formed on the samples introduced in the loop at the beginning of the operation and this layer increases with time. However, the samples introduced at different times during the loop operation, are not protected by oxide layers and present material dissolution in some cases.
14. Behaviour of F82H mod. stainless steel in lead-bismuth under temperature gradient
International Nuclear Information System (INIS)
Gomez Briceno, D.; Martin Munoz, F.J.; Soler Crespo, L.; Esteban, F.; Torres, C.
2001-01-01
Austenitic steels can be used in a hybrid system in contact with liquid lead-bismuth eutectic if the region of operating temperatures is not beyond 400 deg. C. For higher temperatures, martensitic steels are recommended. However, at long times, the interaction between the structural material and the eutectic leads to the dissolution of some elements of the steel (Ni, Cr and Fe, mainly) in the liquid metal. In a non-isothermal lead-bismuth loop, the material dissolution takes place at the hot leg of the circuit and, due to the mass transfer, deposition occurs at the cold leg. One of the possible ways to improve the performance of structural materials in lead-bismuth is the creation of an oxide layer. Tests have been performed in a small natural convection loop built of austenitic steel (316L) that has been operating for 3000 h. This loop contains a test area in which several samples of F82Hmod. martensitic steel have been tested at different times. A gas with an oxygen content of 10 ppm was bubbled in the hot area of the circuit during the operation time. The obtained results show that an oxide layer is formed on the samples introduced in the loop at the beginning of the operation and this layer increases with time. However, the samples introduced at different times during the loop operation, are not protected by oxide layers and present material dissolution in some cases
15. Synthesis, structure and photoluminescence properties of amine-templated open-framework bismuth sulfates
International Nuclear Information System (INIS)
Marri, Subba R.; Behera, J.N.
2014-01-01
Two organically-templated bismuth sulfates of the compositions, [C 6 N 2 H 14 ] [Bi(SO 4 ) 2 (NO 3 )], (1) and [C 4 N 2 H 12 ] 4 [Bi 4 (SO 4 ) 10 (H 2 O) 4 ], (2), with open architecture have been synthesized and their structures determined by single crystal X-ray diffraction. 1 has a corrugated layered structure with 8-membered aperture wherein the SO 4 tetrahedra and the BiO 8 polyhedra join together to form (4, 4) net sheets of the metal centers while 2 has a three-dimensional structure possessing 8- and 12-membered channels. Both the compounds show good fluorescence properties exhibiting blue luminescence. Time-resolved fluorescence behavior of 1 and 2 shows mean fluorescence life time of 0.9 and 1.0 ns, respectively. - Graphical abstract: Two open-framework bismuth sulfates with the layered and three-dimensional structures have been synthesized and characterized. Both the compounds show good fluorescence properties exhibiting blue luminescence. Display Omitted - Highlights: • Two organically-templated bismuth sulfates with open architecture have been synthesized and characterized. • One has a corrugated layered structure while the other one has a three-dimensional structure possessing channels. • They are novel in that open-framework three-dimensional main group metal sulfates are first to be reported. • They show good fluorescence properties exhibiting blue luminescence
16. The fabrication and thermal properties of bismuth-aluminum oxide nanothermometers.
Science.gov (United States)
Wang, Chiu-Yen; Chen, Shih-Hsun; Tsai, Ping-Hsin; Chiou, Chung-Han; Hsieh, Sheng-Jen
2017-01-27
Bismuth (Bi) nanowires, well controlled in length and diameter, were prepared by using an anodic aluminum oxide (AAO) template-assisted molding injection process with a high cooling rate. A high performance atomic layer deposition (ALD)-capped bismuth-aluminum oxide (Bi-Al 2 O 3 ) nanothermometer is demonstrated that was fabricated via a facile, low-cost and low-temperature method, including AAO templated-assisted molding injection and low-temperature ALD-capped processes. The thermal behaviors of Bi nanowires and Bi-Al 2 O 3 nanocables were studied by in situ heating transmission electron microscopy. Linear thermal expansion of liquid Bi within native bismuth oxide nanotubes and ALD-capped Bi-Al 2 O 3 nanocables were evaluated from 275 °C to 700 °C and 300 °C to 1000 °C, respectively. The results showed that the ALD-capped Bi-Al 2 O 3 nanocable possesses the highest working temperature, 1000 °C, and the broadest operation window, 300 °C-1000 °C, of a thermal-expanding type nanothermometer. Our innovative approach provides another way of fabricating core-shell nanocables and to further achieve sensing local temperature under an extreme high vacuum environment.
17. Determination of bismuth and cadmium after solid-phase extraction with chromosorb-107 in a syringe
International Nuclear Information System (INIS)
Tokman, Nilgun; Akman, Suleyman
2004-01-01
The determination of bismuth and cadmium by graphite furnace atomic absorption spectrometry (GFAAS) after solid-phase extraction (SPE) on Chromosorb-107 filled in a syringe was described. To retain the analytes, the sample solution treated with and without ammonium pyrolidine dithiocarbamate (APDC) was drawn into the syringe filled with Chromosorb-107 and discharged back manually. Bismuth and cadmium were quantitatively sorbed at pH ≥ 6 irrespective of whether the analyte was complexed with APDC prior to passing through the Chromosorb-107. Analyte elements sorbed on the resin were quantitatively eluted with 3.0 M of HNO 3 again drawing and discharging the eluent into the syringe and ejected it back. Optimum flow rates of sample or eluent for sorption and elution processes were 20 ml min -1 for drawing and 20 ml min -1 for discharging in all cases. Bismuth and cadmium were analyzed by graphite furnace atomic absorption spectrometry. The elements could be concentrated by drawing and discharging several portions of sample successively but eluting only one time. The validity of the proposed method was checked with standard reference materials (NIST SRM 1515 Apple-Leaves, CWW-TM-E Waste Water and CRM-SW Sea Water). The analyte elements were quantitatively (>95%) recovered from different matrices irrespective of treated samples with APDC. Detection limits (δ) were 0.8 and 1.2 μg l -1 for Bi and Cd, respectively. The method can be characterized with fastness, simplicity, quantitative recovery and high reproducibility
18. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases
Energy Technology Data Exchange (ETDEWEB)
Gomez, Celia L. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Depablos-Rivera, Osmary, E-mail: [email protected] [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Posgrado en Ciencia e Ingeniería de Materiales, UNAM, Unidad de Posgrado, Edificio C, Piso 1, Zona Cultural de CU, México, D.F. 04510 (Mexico); Silva-Bermudez, Phaedra [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Instituto Nacional de Rehabilitación, Calz. México Xochimilco No. 289 Col. Arenal de Guadalupe, C.P.14389, Ciudad de México, D.F. (Mexico); Muhl, Stephen [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico); Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre [Laboratoire de Physique de la Matière Condensée, Université de Picardie Jules Verne, 33 rue Saint Leu, 80039 Amiens Cedex 1 (France); Camps, Enrique [Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, kilómetro 36.5. La Marquesa, Municipio de Ocoyoacac, CP 52750, Estado de México (Mexico); Rodil, Sandra E. [Instituto de Investigaciones en Materiales, UNAM, Circuito Exterior s/n CU, México D.F. 04510 (Mexico)
2015-03-02
The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi{sub 2}O{sub 3} thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi{sub 2}O{sub 3} phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi{sub 2}O{sub 3} thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV.
19. Effect of bismuth ion substitution on structural properties of zinc ferrite nanoparticles
Directory of Open Access Journals (Sweden)
Naraavula Suresh Kumar
2016-06-01
Full Text Available Bismuth doped nano zinc ferrite particles having the general formula ZnFe2-xBixO4 (x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25 were synthesized by sol-gel combustion method. The effect of bismuth doping on structural properties were investigated. The X-ray diffraction (XRD spectra confirm the single phase cubic spinel structure. The average crystallite sizes of all the samples were determined by Debye-Scherrer equation and are in the range 16–20 nm. The lattice parameter increases with the increase of bismuth ion concentration. This is due to the larger ionic radius of Bi3+ ions substituting smaller Fe3+ ions at octahedral sites (B-sites. The surface morphology of all compounds was studied by scanning electron microscope (SEM. The microstructure analysis and the particle size were examined by transmission electron microscope (TEM. The compositional stoichiometry of these samples was verified by energy dispersive spectroscopy (EDS analysis.
20. Selective resputtering of bismuth in sputtered Bi-Sr-Ca-Cu-O films
Science.gov (United States)
Grace, J. M.; McDonald, D. B.; Reiten, M. T.; Olson, J.; Kampwirth, R. T.; Gray, K. E.
1991-10-01
We present studies using a dc magnetron in an on-axis configuration to sputter Bi-Sr-Ca-Cu-O films from a composite target. These studies show that bismuth can be preferentially resputtered. The influence of ozone, molecular oxygen, and total pressure on the resputtering of bismuth is investigated and discussed. Ozone, in low concentrations, can dramatically affect the degree of resputtering. By comparing the effects of molecular oxygen and ozone, some insight is gained regarding the possible mechanisms of negative ion formation in the magnetron environment. Based on our results we suggest that molecular oxygen can bring about resputtering primarily by forming O+2, which collides with the target to produce energetic negative oxygen ions. In contrast, ozone may form negative ions by electron impact in the dark space above the target, giving rise to lower-energy negative ions, which can traverse the plasma unneutralized and can be stopped with an applied bias on the sample block. With no added oxidant, negative oxygen ions from the target oxygen may dominate the background resputtering. Similarity is found between our results and those for similar studies on Y-Ba-Cu-O by other workers. Bismuth in Bi-Sr-Ca-Cu-O behaves as barium in Y-Ba-Cu-O with regards to preferential resputtering; furthermore, the response of strontium, calcium, and copper to oxygen in sputtered Bi-Sr-Ca-Cu-O is similar to what is observed for copper in Y-Ba-Cu-O.
1. Selective resputtering of bismuth in sputtered Bi-Sr-Ca-Cu-O films
International Nuclear Information System (INIS)
Grace, J.M.; McDonald, D.B.; Reiten, M.T.; Olson, J.; Kampwirth, R.T.; Gray, K.E.
1991-01-01
We present studies using a dc magnetron in an on-axis configuration to sputter Bi-Sr-Ca-Cu-O films from a composite target. These studies show that bismuth can be preferentially resputtered. The influence of ozone, molecular oxygen, and total pressure on the resputtering of bismuth is investigated and discussed. Ozone, in low concentrations, can dramatically affect the degree of resputtering. By comparing the effects of molecular oxygen and ozone, some insight is gained regarding the possible mechanisms of negative ion formation in the magnetron environment. Based on our results we suggest that molecular oxygen can bring about resputtering primarily by forming O + 2 , which collides with the target to produce energetic negative oxygen ions. In contrast, ozone may form negative ions by electron impact in the dark space above the target, giving rise to lower-energy negative ions, which can traverse the plasma unneutralized and can be stopped with an applied bias on the sample block. With no added oxidant, negative oxygen ions from the target oxygen may dominate the background resputtering. Similarity is found between our results and those for similar studies on Y-Ba-Cu-O by other workers. Bismuth in Bi-Sr-Ca-Cu-O behaves as barium in Y-Ba-Cu-O with regards to preferential resputtering; furthermore, the response of strontium, calcium, and copper to oxygen in sputtered Bi-Sr-Ca-Cu-O is similar to what is observed for copper in Y-Ba-Cu-O
2. Performance comparison of metallic, actinide burning fuel in lead-bismuth and sodium cooled fast reactors
International Nuclear Information System (INIS)
Weaver, K.D.; Herring, J.S.; Macdonald, P.E.
2001-01-01
Various methods have been proposed to ''incinerate'' or ''transmute'' the current inventory of transuranic waste (TRU) that exits in spent light-water-reactor (LWR) fuel, and weapons plutonium. These methods include both critical (e.g., fast reactors) and non-critical (e.g., accelerator transmutation) systems. The work discussed here is part of a larger effort at the Idaho National Engineering and Environmental Laboratory (INEEL) and at the Massachusetts Institute of Technology (MIT) to investigate the suitability of lead and lead-alloy cooled fast reactors for producing low-cost electricity as well as for actinide burning. The neutronics of non fertile fuel loaded with 20 or 30-wt% light water reactor (LWR) plutonium plus minor actinides for use in a lead-bismuth cooled fast reactor are discussed in this paper, with an emphasis on the fuel cycle life and isotopic content. Calculations show that the average actinide burn rate is similar for both the sodium and lead-bismuth cooled cases ranging from -1.02 to -1.16 g/MWd, compared to a typical LWR actinide generation rate of 0.303 g/MWd. However, when using the same parameters, the sodium-cooled case went subcritical after 0.2 to 0.8 effective full power years, and the lead-bismuth cooled case ranged from 1.5 to 4.5 effective full power years. (author)
3. Red light emission from europium doped zinc sodium bismuth borate glasses
Science.gov (United States)
Hegde, Vinod; Viswanath, C. S. Dwaraka; Upadhyaya, Vyasa; Mahato, K. K.; Kamath, Sudha D.
2017-12-01
Zinc sodium bismuth borate (ZNBB) glasses doped with different concentrations of europium were prepared by conventional melt quenching method and characterized through the measurements of density, refractive index, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectra, optical absorption, luminescence and radiative lifetimes. FTIR spectra showed seven characteristic peaks of bismuth and borate functional groups in the range of 400-1600 cm-1. The optical band gap and bonding parameters have been calculated from absorption spectra. Photoluminescence spectra recorded in the visible region with 394 nm excitation are used to calculate the Judd-Ofelt (JO) intensity parameters (Ω2 and Ω4). The JO intensity parameters have been used to calculate the radiative parameters such as branching ratio (β), stimulated emission cross-section (σse), transition probability (A) for the fluorescent level of 5D0→7F2. Decay rates through single exponential are used to calculate the lifetime (τm) of the meta-stable state 5D0 of (Eu3+ ion) these glasses. The radiative parameters measured for all these glasses show 0.7 mol% europium doped zinc sodium bismuth borate glass 5D0→7F2 transition has the potential for red laser applications. The quality of the colour emitted by the present glasses are estimated quantitatively by CIE chromaticity coordinates, which confirms the suitability of these glasses as a red emitting material for field emission technologies and LEDs.
4. Use of a Soluble Anode in Electrodeposition of Thick Bismuth Telluride Layers
Science.gov (United States)
Maas, M.; Diliberto, S.; de Vaulx, C.; Azzouz, K.; Boulanger, C.
2014-10-01
Integration of thermoelectric devices within an automotive heat exchanger could enable conversion of lost heat into electrical energy, contributing to improved total output from the engine. For this purpose, synthesis of thick bismuth telluride (Bi2Te3) films is required. Bismuth telluride has been produced by an electrochemical method in nitric acid with a sacrificial bismuth telluride anode as the source of cations. The binary layer grows on the working electrode while the counter-electrode, a Bi2Te3 disk obtained by high frequency melting, is oxidized to BiIII and TeIV. This process leads to auto-regeneration of the solution without modification of its composition. The thickness of films deposited by use of the Bi2Te3 anode was approximately 10 times that without. To demonstrate the utility of a soluble anode in electrochemical deposition, we report characterization of the composition and morphology of the films obtained under different experimental conditions. Perfectly dense and regular Bi2Te3 films (˜400 μm) with low internal stress and uniform composition across the cross-section were prepared. Their thermoelectric properties were assessed.
5. Opto-electronic properties of bismuth oxide films presenting different crystallographic phases
International Nuclear Information System (INIS)
Gomez, Celia L.; Depablos-Rivera, Osmary; Silva-Bermudez, Phaedra; Muhl, Stephen; Zeinert, Andreas; Lejeune, Michael; Charvet, Stephane; Barroy, Pierre; Camps, Enrique; Rodil, Sandra E.
2015-01-01
The optical, electrical and structural properties of bismuth oxide thin films deposited by radio frequency reactive magnetron sputtering were studied. The Bi 2 O 3 thin films were grown on Si and glass substrates under different power and substrate temperatures in an oxygen-enriched plasma leading to films with different crystalline phase as evidenced by X-ray diffraction and Raman spectroscopy. The optical properties of the films were measured using ellipsometric spectroscopy and optical transmission spectra. In order to parameterize the optical dispersion functions (n, k) of the films, the Tauc–Lorentz dispersion model was used. The optical bandgap was then assessed by different methods and the results are compared to the thermal variations of the electrical resistivity of the films. It was found that the refractive index, extinction coefficient and optical gap strongly depend on the deposition conditions and the crystalline phase; the fluorite defect cubic δ-Bi 2 O 3 phase showed the lowest optical gap and lower resistivity. - Highlights: • Different bismuth oxide phases were obtained by sputtering. • The power and substrate temperature were the two key parameters. • Room temperature delta-Bi 2 O 3 thin films were obtained. • The optical bandgap was around 1.5 and 2.2 eV, depending on the phase. • The bismuth oxide films presented activation energies around 1 eV
6. Study on the extraction of rare earth elements in liquid bismuth
International Nuclear Information System (INIS)
1987-01-01
Three factors, which are important for the extraction of rare earth elements in liquid bismuth - molten salt system, were studied, i. e., the equilibrium distribution of neodymium, samarium and bismuth between molten LiCl - liquid Bi-Li alloys, the extraction rate of rare earths, and the characteristics of the extractor with drop dispersion. The rare earth elements were extracted through redox reactions. In high range of Li-mole fraction in the alloy phase, X Li , the distribution of neodymium and bismuth in the salt phase markedly increased as X Li increased. The anomalous increase is attributed to the formation of the compound comprised of Nd, Li, Bi and oxygen in the salt phase. The redox reaction processes were very fast and the extraction rates for rare earths are controlled by the diffusion processes of the solute and the metallic lithium. The process for the formation of liquid metal drops in the continuous phase is predictable from semiempirical correlations reported for aqueous solution - organic solvent systems. The height of droplet bed being accumulated on drop settling portion is predictable from the coalescence time of single drop to a flat metal interface. The coalescence of metal drop to clean interface was very fast. The extractor type of liquid metal dispersion in molten salt is suitable for the extraction process in the fuel reprocessing of MSR or MSBR. (author)
7. Glass composite waste forms for iodine confined in bismuth-embedded SBA-15
Science.gov (United States)
Yang, Jae Hwan; Park, Hwan Seo; Ahn, Do-Hee; Yim, Man-Sung
2016-11-01
The aim of this study was to stabilize bismuth-embedded SBA-15 that captured iodine gas by fabrication of monolithic waste forms. The iodine containing waste was mixed with Bi2O3 (a stabilizing additive) and low-temperature sintering glass followed by pelletizing and the sintering process to produce glass composite materials. Iodine volatility during the sintering process was significantly affected by the ratio of Bi2O3 and the glass composition. It was confirmed that BiI3, the main iodine phase within bismuth-embedded SBA-15, was effectively transformed to the mixed phases of Bi5O7I and BiOI. The initial leaching rates of iodine from the glass composite waste forms ranged 10-3-10-2 g/m2 day, showing the stability of the iodine phases encapsulated by the glassy networks. It was also observed that common groundwater anions (e.g., chloride, carbonate, sulfite, and fluoride) elevated the iodine leaching rate by anion exchange reactions. The present results suggest that the glass composite waste form of bismuth-embedded SBA-15 could be a candidate material for stable storage of 129I.
8. Study of Transport and Micro-structural properties of Magnesium Di-Boride Strand under react and bend mode and bend and react mode
International Nuclear Information System (INIS)
Kundu, Ananya; Kumar Das, Subrat; Bano, Anees; Pradhan, Subrata
2017-01-01
I-V characterization of commercial multi-filamentary Magnesium Di-Boride (MgB 2 ) wire of diameter 0.83 mm were studied in Cryocooler at self-field I-V characterization system under both react and bend mode and bend and react mode for a range of temperature 6 K - 25 K. This study is of practical technical relevance where the heat treatment of the superconducting wire makes the wire less flexible for winding in magnet and in other applications. In the present work the bending diameter was varied from 40 mm to 20 mm and for each case critical current (I c ) of the strand is measured for above range of temperature. A customized sample holder is fabricated and thermally anchored with the 2 nd cold stage of Cryocooler. It is observed from the measurement that the strand is more susceptible to degradation for react and bend cases. The transport measurement of the strand was accompanied by SEM analyses of bend samples. Also the tensile strength of the raw strands and the heat treated strands were carried out at room temperature in Universal Testing Machine (UTM) to have an estimate about the limiting winding tension value during magnet fabrication. (paper)
9. Effect of cadmium doping on some properties of glass-insulated bismuth-based microwires
International Nuclear Information System (INIS)
Meglei, D.; Dyntu, M.
2011-01-01
Full text: According to the literature, semiconductor converters based on films and wire crystals are widely used in present-day microelectronics. However, the production of efficient semiconductor converters requires crystals of high structural perfection with a given composition and desired electrical and mechanical properties. In this work, we describe the study of the perfection of the microstructure and mechanical properties of glass-insulated microwires based on Bi doped with cadmium (Cd) and the technique of preparation of micro resistors suitable for instrumentation applications. Microscopic studies of ground, polished, and chemically etched microwires doped with cadmium showed that they have smooth cylindrical surfaces in the entire range of diameters. Sizes of defects in the form of micropores, microcracks, dislocations, and twins on their surface are much smaller than those of pure bismuth microwire. It is also found that the tendency to twinning and the number and size of surface defects decrease with decreasing diameters; at the same time, their homogeneity increases. The tensile strength of the studied microwires with glass insulation is high for all tested diameters and ranges within 33.274.1 kg/mm with respect to internal diameters of 5.6 21.2 m; in addition, they withstand a breaking force up to 130 g and more, whereas the samples of pure bismuth microwires withstood a force up to 80 g. It is also found that the tensile strength of cadmium doped microwires is significantly higher than that of undoped samples. The bending strength as a measure of elasticity was determined using a special installation according to the critical bending radius of the sample at which the sample integrity is violated. The results of bending tests showed that, with increasing diameter of the doped samples, the critical radius linearly increases; that is, in this case, the elasticity increases with decreasing diameter. Metallographic analysis revealed that cadmium in the
10. Bismuth, lansoprazole, amoxicillin and metronidazole or clarithromycin as first-line Helicobacter pylori therapy.
Science.gov (United States)
Zhang, Wei; Chen, Qi; Liang, Xiao; Liu, Wenzhong; Xiao, Shudong; Graham, David Y; Lu, Hong
2015-11-01
11. Growth of Li doped bismuth oxide nanorods and its electrochemical performance for the determination of L-cysteine
International Nuclear Information System (INIS)
Wen, Yong; Pei, Li-zhai; Wei, Tian
2017-01-01
Li doped bismuth oxide nanorods have been prepared using sodium bismuthate and Li acetate. X-ray diffraction (XRD) pattern shows that the nanorods are composed of monoclinic Bi_2O_4 and cubic LiBi_1_2O_1_8_._5_0 phases. Scanning electron microscopy (SEM) observation shows that the nanorods have the length and diameter of 1-5 μm and 50-350 nm, respectively. The formation of the Li doped bismuth oxide nanorods is closely relative to the hydrothermal conditions. The electrochemical performance for the determination of L-cysteine based on a Li doped bismuth oxide nanorods modified glassy carbon electrode (GCE) has been developed. The CV peak current increases obviously and linearly with increasing the scan rate. Under the optimal conditions, Li doped bismuth oxide nanorods modified GCE exhibits good analytical performance with good reproducibility and stability. The linear range of L-cysteine is 0.0001-2 mM and the detection limit is 0.36 μM and 0.17 μM for cvp1 and cvp2, respectively. (author)
12. Growth of Li doped bismuth oxide nanorods and its electrochemical performance for the determination of L-cysteine
Energy Technology Data Exchange (ETDEWEB)
Wen, Yong, E-mail: [email protected] [School of Civil Engineering and Architecture, Xinjiang University (China); Pei, Li-zhai; Wei, Tian [chool of Materials Science and Engineering, Anhui University of Technology (China)
2017-05-15
Li doped bismuth oxide nanorods have been prepared using sodium bismuthate and Li acetate. X-ray diffraction (XRD) pattern shows that the nanorods are composed of monoclinic Bi{sub 2}O{sub 4} and cubic LiBi{sub 12}O{sub 18.50} phases. Scanning electron microscopy (SEM) observation shows that the nanorods have the length and diameter of 1-5 μm and 50-350 nm, respectively. The formation of the Li doped bismuth oxide nanorods is closely relative to the hydrothermal conditions. The electrochemical performance for the determination of L-cysteine based on a Li doped bismuth oxide nanorods modified glassy carbon electrode (GCE) has been developed. The CV peak current increases obviously and linearly with increasing the scan rate. Under the optimal conditions, Li doped bismuth oxide nanorods modified GCE exhibits good analytical performance with good reproducibility and stability. The linear range of L-cysteine is 0.0001-2 mM and the detection limit is 0.36 μM and 0.17 μM for cvp1 and cvp2, respectively. (author)
13. Monte Carlo simulations for dose enhancement in cancer treatment using bismuth oxide nanoparticles implanted in brain soft tissue.
Science.gov (United States)
Taha, Eslam; Djouider, Fathi; Banoqitah, Essam
2018-03-26
The objective of this work is to study the dosimetric performances of bismuth oxide nanoparticles implanted in tumors in cancer radiotherapy. GEANT4 based Monte Carlo numerical simulations were performed to assess dose enhancement distributions in and around a 1 × 1 × 1 cm 3 tumor implanted with different concentrations of bismuth oxide and irradiated with low energies 125 I, 131 Cs, and 103 Pd radioactive sources. Dose contributions were considered from photoelectrons, Auger electrons, and characteristic X-rays. Our results show the dose enhancement increased with increasing both bismuth oxide concentration in the target and photon energy. A dose enhancement factor up to 18.55 was obtained for a concentration of 70 mg/g of bismuth oxide in the tumor when irradiated with 131 Cs source. This study showed that bismuth oxide nanoparticles are innovative agents that could be potentially applicable to in vivo cancer radiotherapy due to the fact that they induce a highly localized energy deposition within the tumor.
14. Study of the bismuth oxide concentration required to provide Portland cement with adequate radiopacity for endodontic use.
Science.gov (United States)
Bueno, Carlos Eduardo da Silveira; Zeferino, Eduardo Gregatto; Manhães, Luiz Roberto Coutinho; Rocha, Daniel Guimarães Pedro; Cunha, Rodrigo Sanches; De Martin, Alexandre Sigrist
2009-01-01
15. Greener Friedel-Crafts Acylation using Microwave-enhanced reactivity of Bismuth Triflate in the Friedel-Crafts Benzoylation of Aromatic Compounds with Benzoic Anhydride
DEFF Research Database (Denmark)
Tran, Phuong Hoang; Nguyen, Hai Truong; Hansen, Poul Erik
2017-01-01
An efficient and facile bismuth trifluoromethanesulfonate-catalyzed benzoylation of aromatic compounds using benzoic anhydride under solvent-free microwave irradiation has been developed. The microwave-assisted Friedel-Crafts benzoylation results in good yields within short reaction times. Bismuth...
16. The cytotoxicity of organobismuth compounds with certain molecular structures can be diminished by replacing the bismuth atom with an antimony atom in the molecules.
Science.gov (United States)
Kohri, Kumiko; Yoshida, Eiko; Yasuike, Shuji; Fujie, Tomoya; Yamamoto, Chika; Kaji, Toshiyuki
2015-06-01
Organic-inorganic hybrid molecules, which are composed of an organic structure and metal(s), are indispensable for synthetic chemical reactions; however, their toxicity has been incompletely understood. In the present study, we discovered two cytotoxic organobismuth compounds whose cytotoxicity diminished upon replacement of the intramolecular bismuth atom with an antimony atom. The intracellular accumulation of the organobismuth compounds was much higher than that of the organoantimony compounds with the corresponding organic structures. We also showed that both the organic structure and bismuth atom are required for certain organobismuth compounds to exert their cytotoxic effect, suggesting that the cytotoxicity of such a compound is a result of an interaction between the organic structure and the bismuth atom. The present data suggest that organobismuth compounds with certain molecular structures exhibit cytotoxicity via an interaction between the molecular structure and the bismuth atom, and this cytotoxicity can be diminished by replacing the bismuth atom with an antimony atom, resulting in lower intracellular accumulation.
17. Comportamiento parabólico del crecimiento de capas boradas en los aceros Y8A y X12M // Parabolic behavior of boriding layers growth in Y8A and X12M steels
Directory of Open Access Journals (Sweden)
C. Figueroa Hernández
1999-01-01
Full Text Available Se determina la influencia que tienen los principales parámetros tecnológicos del borado en el crecimiento de las capas y secorrobora el cumplimiento de la ley parabólica para predecir este comportamiento en los aceros Y8A y X12M.El proceso de borado se aplica en una mezcla de carburo de silicio y bórax (70 y 30 % a la temperatura de 850, 900 y 950 oCdurante un tiempo de 2, 4 y 6 horas. Como variable dependiente se seleccionó la profundidad del recubrimiento, a partir de lacual se obtuvieron los coeficientes del crecimiento parabólico y la energía de activación en función de la temperatura, el tiempodel proceso y el tipo de acero.La caracterización metalográfica reveló la presencia de la fase Fe2BPalabras claves: Borado, recubrimiento superf icial , t ecnología de recubrimiento.__________________________________________________________________________AbstractIt was determined the influence of the main technological parameters of the boriding process, and a mathematical model thatallows to predict this conduct on the steels Y8A and X12M steels was obtained.The boriding process is applied in a mixture of silicon carbide and borax (70 and 30% at 850, 900 and 950 oC temperatureduring a period of time 2, 4 and 6 hours. As an independent variable the depth of the coat was selected.It was obtained the parabolic growth coefficients, and the activation energy according to temperature, time and the chemicalcomposition of steel.Metallografic analysis reveals the presence of Fe2B phase.Key words: Boriding process, superf icial coat , coat technology.
18. Screen-printed electrodes made of a bismuth nanoparticle porous carbon nanocomposite applied to the determination of heavy metal ions
International Nuclear Information System (INIS)
Niu, Pengfei; Gich, Martí; Roig, Anna; Fernández-Sánchez, César; Navarro- Hernández, Carla; Fanjul-Bolado, Pablo
2016-01-01
This work reports on the simplified fabrication and on the characterization of bismuth-based screen-printed electrodes (SPEs) for use in heavy metal detection. A nanocomposite consisting of bismuth nanoparticles and amorphous carbon was synthesized by a combined one-step sol-gel and pyrolysis process and milled down to a specific particle size distribution as required for the preparation of an ink formulation to be used in screen printing. The resulting electrochemical devices were applied to the detection of Pb(II) and Cd(II) ions in water samples. The porous structure of carbon and the high surface area of the bismuth nanoparticles allow for the detection of Pb(II) and Cd(II) at concentration levels below 4 ppb. The application of the SPEs was demonstrated by quantifying these ions in tap drinking water and wastewater collected from an influent of an urban wastewater treatment plant. (author)
19. The application of three-phase liquid-liquid extraction to the analysis of bismuth and tellurium in sulphide concentrates
International Nuclear Information System (INIS)
Nicholas, D.J.
1976-01-01
An extraction system consisting of one aqueous and two organic phases is described. Diantipyrylmethane (DAM) is used as the extractant for bismuth and tellurium, which are extracted into the smaller of the two organic phases from nitric acid and perchloric acid respectively. The extraction efficiency is in the range of 90 to 95 per cent, compensation for incomplete extraction being made by the technique of standard addition. Copper, lead, and zinc are not extracted in either procedure. When the solutions contain high concentrations of iron, thioglycolic acid is used as a masking agent for iron in the extraction of bismuth. Atomic-absorption spectrophotometry is used for the analysis of the third phase after it has been diluted with methanol. The precision for bismuth and tellurium is in the range of 3 to 4 per cent. The accuracy, as ascertained from comparative analyses of sulphide concentrates, is good
20. Feasibility of preparing patterned molybdenum coatings on bismuth telluride thermoelectric modules.
Energy Technology Data Exchange (ETDEWEB)
Sarobol, Pylin; Hall, Aaron Christopher; Miller, Stephen Samuel; Knight, Marlene E.; LePage, William S.; Sobczak, Catherine Elizabeth.; Wesolowski, Daniel Edward
2013-09-01
Molybdenum electrical interconnects for thermoelectric modules were produced by air plasma spraying a 30%CE%BCm size molybdenum powder through a laser-cut Kapton tape mask. Initial feasibility demonstrations showed that the molybdenum coating exhibited excellent feature and spacing retention (~170%CE%BCm), adhered to bismuth-telluride, and exhibited electrical conductivity appropriate for use as a thermoelectric module interconnect. A design of experiments approach was used to optimize air plasma spray process conditions to produce a molybdenum coating with low electrical resistivity. Finally, a molybdenum coating was successfully produced on a fullscale thermoelectric module. After the addition of a final titanium/gold layer deposited on top of the molybdenum coating, the full scale module exhibited an electrical resistivity of 128%CE%A9, approaching the theoretical resistivity value for the 6mm module leg of 112%CE%A9. Importantly, air plasma sprayed molybdenum did not show significant chemical reaction with bismuth-telluride substrate at the coating/substrate interface. The molybdenum coating microstructure consisted of lamellar splats containing columnar grains. Air plasma sprayed molybdenum embedded deeply (several microns) into the bismuth-telluride substrate, leading to good adhesion between the coating and the substrate. Clusters of round pores (and cracks radiating from the pores) were found immediately beneath the molybdenum coating. These pores are believed to result from tellurium vaporization during the spray process where the molten molybdenum droplets (2623%C2%B0C) transferred their heat of solidification to the substrate at the moment of impact. Substrate cooling during the molybdenum deposition process was recommended to mitigate tellurium vaporization in future studies.
1. Synthesis, structure and photoluminescence properties of amine-templated open-framework bismuth sulfates
Energy Technology Data Exchange (ETDEWEB)
Marri, Subba R.; Behera, J.N., E-mail: [email protected]
2014-02-15
Two organically-templated bismuth sulfates of the compositions, [C{sub 6}N{sub 2}H{sub 14}] [Bi(SO{sub 4}){sub 2}(NO{sub 3})], (1) and [C{sub 4}N{sub 2}H{sub 12}]{sub 4}[Bi{sub 4}(SO{sub 4}){sub 10}(H{sub 2}O){sub 4}], (2), with open architecture have been synthesized and their structures determined by single crystal X-ray diffraction. 1 has a corrugated layered structure with 8-membered aperture wherein the SO{sub 4} tetrahedra and the BiO{sub 8} polyhedra join together to form (4, 4) net sheets of the metal centers while 2 has a three-dimensional structure possessing 8- and 12-membered channels. Both the compounds show good fluorescence properties exhibiting blue luminescence. Time-resolved fluorescence behavior of 1 and 2 shows mean fluorescence life time of 0.9 and 1.0 ns, respectively. - Graphical abstract: Two open-framework bismuth sulfates with the layered and three-dimensional structures have been synthesized and characterized. Both the compounds show good fluorescence properties exhibiting blue luminescence. Display Omitted - Highlights: • Two organically-templated bismuth sulfates with open architecture have been synthesized and characterized. • One has a corrugated layered structure while the other one has a three-dimensional structure possessing channels. • They are novel in that open-framework three-dimensional main group metal sulfates are first to be reported. • They show good fluorescence properties exhibiting blue luminescence.
2. Oxygen concentration diffusion analysis of lead-bismuth-cooled, natural-circulation reactor
International Nuclear Information System (INIS)
Ito, Kei; Sakai, Takaaki
2001-11-01
The feasibility study on fast breeder reactors in Japan has been conducted at JNC and related organizations. The Phase-I study has finished in March, 2001. During the Phase-I activity, lead-bismuth eutectic coolant has been selected as one of the possible coolant options and a medium-scale plant, cooled by a lead-bismuth natural circulation flow was studied. On the other side, it is known that lead-bismuth eutectic has a problem of structural material corrosiveness. It was found that oxygen concentration control in the eutectic plays an important role on the corrosion protection. In this report, we have developed a concentration diffusion analysis code (COCOA: COncentration COntrol Analysis code) in order to carry out the oxygen concentration control analysis. This code solves a two-dimensional concentration diffusion equation by the finite differential method. It is possible to simulate reaction of oxygen and hydrogen by the code. We verified the basic performance of the code and carried out oxygen concentration diffusion analysis for the case of an oxygen increase by a refueling process in the natural circulation reactor. In addition, characteristics of the oxygen control system was discussed for a different type of the control system as well. It is concluded that the COCOA code can simulate diffusion of oxygen concentration in the reactor. By the analysis of a natural circulation medium-scale reactor, we make clear that the ON-OFF control and PID control can well control oxygen concentration by choosing an appropriate concentration measurement point. In addition, even when a trouble occurs in the oxygen emission or hydrogen emission system, it observes that control characteristic drops away. It is still possible, however, to control oxygen concentration in such case. (author)
3. Percutaneous intraductal radiofrequency ablation in the management of unresectable Bismuth types III and IV hilar cholangiocarcinoma.
Science.gov (United States)
Wang, Yu; Cui, Wei; Fan, Wenzhe; Zhang, Yingqiang; Yao, Wang; Huang, Kunbo; Li, Jiaping
2016-08-16
To assess the feasibility and safety of percutaneous intraductal radiofrequency ablation (RFA) for unresectable Bismuth types III and IV hilar cholangiocarcinoma. Percutaneous intraductal RFA combined with metal stent placement was successful in all patients without any technical problems; the technical success rate was 100%. Chemotherapy was administered to two patients. After treatment, serum direct bilirubin levels were notably decreased. Six patients died during the follow-up period. Median stent patency from the time of the first RFA and survival from the time of diagnosis were 100 days (95% confidence interval (CI), 85-115 days) and 5.3 months (95% CI, 2.5-8.1 months), respectively. No acute pancreatitis, bile duct bleeding and perforation, bile leakage, or other severe complications occurred. Four cases of procedure-related cholangitis, three cases of postoperative abdominal pain, and five cases of asymptomatic transient increase in serum amylase were observed. One patient who presented with stent blockage 252 days' post-procedure underwent repeat ablation. Between September 2013 and May 2015, nine patients with unresectable Bismuth types III and IV hilar cholangiocarcinoma who were treated with percutaneous intraductal RFA combined with metal stent placement after the percutaneous transhepatic cholangial drainage were included in the retrospective analysis. Procedure-related complications, stent patency, and survival after treatment were investigated. Percutaneous intraductal RFA combined with metal stent placement is a technically safe and feasible therapeutic option for the palliative treatment of unresectable Bismuth types III and IV hilar cholangiocarcinoma. Its long-term efficacy and safety is promising, but needs further study via randomized and prospective trials that include a greater number of patients.
4. [Influence of Saccharomyces boulardii Sachets combined with bismuth quadruple therapy for initial Helicobacter pylori eradication].
Science.gov (United States)
Zhu, X Y; Du, J; Wu, J; Zhao, L W; Meng, X; Liu, G F
2017-08-08
5. Origin of broad NIR photoluminescence in bismuthate glass and Bi-doped glasses at room temperature
Energy Technology Data Exchange (ETDEWEB)
Peng, Mingying; Zollfrank, Cordt; Wondraczek, Lothar [Lehrstuhl fuer Glas und Keramik, WW3, Friedrich Alexander Universitaet Erlangen-Nuernberg, Martensstrasse 5, D-91058 Erlangen (Germany)], E-mail: [email protected], E-mail: [email protected]
2009-07-15
Bi-doped glasses with broadband photoluminescence in the near-infrared (NIR) spectral range are presently receiving significant consideration for potential applications in telecommunications, widely tunable fiber lasers and spectral converters. However, the origin of NIR emission remains disputed. Here, we report on NIR absorption and emission properties of bismuthate glass and their dependence on the melting temperature. Results clarify that NIR emission occurs from the same centers as it does in Bi-doped glasses. The dependence of absorption and NIR emission of bismuthate glasses on the melting temperature is interpreted as thermal dissociation of Bi{sub 2}O{sub 3} into elementary Bi. Darkening of bismuthate glass melted at 1300 deg. C is due to the agglomeration of Bi atoms. The presence of Bi nanoparticles is confirmed by transmission electron microscopy, high-resolution energy dispersive x-ray spectroscopy and element distribution mapping. By adding antimony oxide as an oxidation agent to the glass, NIR emission centers can be eliminated and Bi{sup 3+} is formed. By comparing with atomic spectral data, absorption bands at {approx}320 , {approx}500 , 700 , 800 and 1000 nm observed in Bi-doped glasses are assigned to Bi{sup 0} transitions {sup 4}S{sub 3/2}{yields}{sup 2}P{sub 3/2}, {sup 4}S{sub 3/2}{yields}{sup 2}P{sub 1/2}, {sup 4}S{sub 3/2}{yields}{sup 2}D{sub 5/2}, {sup 4}S{sub 3/2}{yields}{sup 2}D{sub 3/2}(2) and {sup 4}S{sub 3/2}{yields}{sup 2}D{sub 3/2}(1), respectively, and broadband NIR emission is assigned to the transition {sup 2}D{sub 3/2}(1){yields}{sup 4}S{sub 3/2}.
6. Numerical Modeling of Lead Oxidation in Controlled Lead Bismuth Eutectic Systems: Chemical Kinetics and Hydrodynamic Effects
International Nuclear Information System (INIS)
Wu, Chao; Kanthi Kiran Dasika; Chen, Yitung; Moujaes, Samir
2002-01-01
Using liquid Lead-Bismuth Eutectic (LBE) as coolant in nuclear systems has been studied for more than 50 years. And LBE has many unique nuclear, thermo physical and chemical attributes which are attractive for practical application. But, corrosion is one of the greatest concerns in using liquid Lead-Bismuth Eutectic (LBE) as spallation target in the Accelerator-driven Transmutation of Waste (ATW) program. Los Alamos National Laboratory has designed and built the Liquid Lead-Bismuth Materials Test Loop (MTL) to study the materials behavior in a flow of molten LBE. A difference of 100 deg. C was designed between the coldest and the hottest parts at a nominal flow rate of 8.84 GPM. Liquid LBE flow was activated by a mechanical sump pump or by natural convection. In order to maintain a self-healing protective film on the surface of the stainless steel pipe, a certain concentration of oxygen has to be maintained in the liquid metal. Therefore, it is of importance to understand what the oxygen concentrations are in the LBE loop related to the corrosion effects on the metal surface, the temperature profiles, the flow rates, and diffusion rates through the metal surface. The chemical kinetics also needs to be fully understood in the corrosion processes coupled with the hydrodynamics. The numerical simulation will be developed and used to analyze the system corrosion effects with different kind of oxygen concentrations, flow rates, chemical kinetics, and geometries. The hydrodynamics modeling of using computational fluid dynamics will provide the necessary the levels of oxygen and corrosion products close to the boundary or surface. This paper presents an approach towards the above explained tasks by analyzing the reactions between the Lead and oxygen at a couple of sections in the MTL. Attempt is also made to understand the surface chemistry by choosing an example model and estimating the near wall surface concentration values for propane and oxygen. (authors)
7. Synthesis and characterization of new metal-rich borides with boron fragments; Synthese und Charakterisierung von neuartigen metallreichen Boriden mit Borfragmenten
Energy Technology Data Exchange (ETDEWEB)
Mbarki, Mohammed
2016-03-30
The present dissertation deals with the synthesis and characterization of new metal-rich borides of the Ce{sub 7}Ni{sub 5±x}Ge{sub 3±x}In{sub 6{sup -}}, Nb{sub 2}OsB{sub 2{sup -}} and NbRuB-type.The samples are synthesized by a solid state reaction route from elements using an electric arc furnace. The structural characterization of the compounds was carried out by using X-ray diffraction methods on powder samples and single crystals. The chemical composition of single-crystals was verified by EDX analyses. Moreover, the magnetic properties of suitable samples were investigated by SQUID magnetometry.The crystal structure of compounds with the nominal composition NbFe{sub 1-x}Ir{sub 6+x}B{sub 8} is successfully solved from single crystal X-ray data. The most prominent feature in this structure are one-dimensional chains along the c-axis formed by the magnetically active element iron on a site of mixed occupation with Iridium (Fe: Ir = 0.77 (2) 0.23 (2)). Thermomagnetic investigations reveal, that ferromagnetic ordering is observed below the Curie temperature (TC) of 350 K. Theoretical investigations suggest that the iron-chains are mainly responsible for the ferromagnetic ordering. In addition, the magnetocaloric effect (MCE) is calculated using isothermal magnetization measurements at several temperatures. The maximal magnetic entropy change ΔS = 0.032 J kg{sup -1} K{sup -1} is observed in the vicinity of T{sub C}. For the phases Nb{sub 6}Mn{sub 0,75(2)}Ir{sub 6,25(2)}B{sub 8} and Nb{sub 6}Co{sub 1,09(2)}Ir{sub 5,91(2)}B{sub 8} a relationship between the measured ferrimagnetic ordering and the crystal structure is found. Tiny superstructure reflections measured by Selected Area Electron Diffraction (SEAD) indicate a different crystal system for those compounds, which allows a ferrimagnetic spin arrangement within this crystal structure.In the second part of the thesis new results about the Nb{sub 2}OsB{sub 2-} and NbRuB-type borides are presented, which both
8. Synthesis, characterization and thermoelectric properties of metal borides, boron carbides and carbaborides; Synthese, Charakterisierung und thermoelektrische Eigenschaften ausgewaehlter Metallboride, Borcarbide und Carbaboride
Energy Technology Data Exchange (ETDEWEB)
Guersoy, Murat
2015-07-06
This work reports on the solid state synthesis and structural and thermoelectrical characterization of hexaborides (CaB{sub 6}, SrB{sub 6}, BaB{sub 6}, EuB{sub 6}), diboride dicarbides (CeB{sub 2}C{sub 2}, LaB{sub 2}C{sub 2}), a carbaboride (NaB{sub 5}C) and composites of boron carbide. The characterization was performed by X-ray diffraction methods and Rietveld refinements based on structure models from literature. Most of the compounds were densified by spark plasma sintering at 100 MPa. As high-temperature thermoelectric properties the Seebeck coefficients, electrical conductivities, thermal diffusivities and heat capacities were measured between room temperature and 1073 K. ZT values as high as 0.5 at 1273 K were obtained for n-type conducting EuB{sub 6}. High-temperature X-ray diffraction also confirmed its thermal stability. The solid solutions Ca{sub x}Sr{sub 1-x}B{sub 6}, Ca{sub x}Ba{sub 1-x}B{sub 6} and Sr{sub x}Ba{sub 1-x}B{sub 6} (x = 0, 0.25, 0.5, 0.75, 1) are also n-type but did not show better ZT values for the ternary compounds compared to the binaries, but for CaB{sub 6} the values of the figure of merit (ca. 0.3 at 1073 K) were significantly increased (ca. 50 %) compared to earlier investigations which is attributed to the densification process. Sodium carbaboride, NaB{sub 5}C, was found to be the first p-type thermoelectric material that crystallizes with the hexaboride-structure type. Seebeck coefficients of ca. 80 μV . K{sup -1} were obtained. Cerium diboride dicarbide, CeB{sub 2}C{sub 2}, and lanthanum diboride dicarbide, LaB{sub 2}C{sub 2}, are metallic. Both compounds were used as model compounds to develop compacting strategies for such layered borides. Densities obtained at 50 MPa were determined to be higher than 90 %. A new synthesis route using single source precursors that contain boron and carbon was developed to open the access to new metal-doped boron carbides. It was possible to obtain boron carbide, but metal-doping could not be
9. Crystalline perfection and mechanical investigations on vertical Bridgman grown Bismuth telluride (Bi_2Te_3) single crystals for thermoelectric applications
International Nuclear Information System (INIS)
Krishna, Anuj; Vijayan, N.; Singh, Budhendra; Thukral, Kanika; Maurya, K.K.
2016-01-01
High efficiency thermoelectric materials plays a vital role in power generation and refrigeration applications. Bismuth telluride (Bi_2Te_3) is one among them. In the present work single crystal of bismuth telluride was grown using vertical Bridgman technique. The phase of grown crystals was analysed using a powder X-ray diffractometer. Quality of the grown crystal was assessed by using high resolution X-ray diffractometer and observed that it is fairly good. Further mechanical investigations on grown crystal was carried out using nano-indentation technique and various mechanical properties like hardness, stiffness and Young’s modulus were evaluated. Observed results clearly indicate its suitability for thermoelectric applications.
10. Increased biliary excretion of glutathione is generated by the glutathione-dependent hepatobiliary transport of antimony and bismuth.
Science.gov (United States)
Gyurasics, A; Koszorús, L; Varga, F; Gregus, Z
1992-10-06
We have recently demonstrated that the hepatobiliary transport of arsenic is glutathione-dependent and is associated with a profound increase in biliary excretion of glutathione (GSH), hepatic GSH depletion and diminished GSH conjugation (Gyurasics A, Varga F and Gregus Z, Biochem Pharmacol 41: 937-944 and Gyurasics A, Varga F and Gregus Z, Biochem Pharmacol 42: 465-468, 1991). The present studies in rats aimed to determine whether antimony and bismuth, other metalloids in group Va of the periodic table, also possess similar properties. Antimony potassium tartrate (25-100 mumol/kg, i.v.) and bismuth ammonium citrate (50-200 mumol/kg, i.v.) increased up to 50- and 4-fold, respectively, the biliary excretion of non-protein thiols (NPSH). This resulted mainly from increased hepatobiliary transport of GSH as suggested by a close parallelism in the biliary excretion of NPSH and GSH after antimony or bismuth administration. Within 2 hr, rats excreted into bile 55 and 3% of the dose of antimony (50 mumol/kg, i.v.) and bismuth (150 mumol/kg, i.v.), respectively. The time courses of the biliary excretion of these metalloids and NPSH or GSH were strikingly similar suggesting co-ordinate hepatobiliary transport of the metalloids and GSH. However, at the peak of their excretion, each molecule of antimony or bismuth resulted in a co-transport of approximately three molecules of GSH. Diethyl maleate, indocyanine green and sulfobromophthalein (BSP), which decreased biliary excretion of GSH, significantly diminished excretion of antimony and bismuth into bile indicating that hepatobiliary transport of these metalloids is GSH-dependent. Administration of antimony, but not bismuth, decreased hepatic GSH level by 30% and reduced the GSH conjugation and biliary excretion of BSP. These studies demonstrate that the hepatobiliary transport of trivalent antimony and bismuth is GSH-dependent similarly to the hepatobiliary transport of trivalent arsenic. Proportionally to their biliary
11. Synthetic structural and biochemical studies of coordination compounds of Bismuth (III) with Schiff bases of sulpha drugs
International Nuclear Information System (INIS)
Khan, Shahina; Gupta, M.K.; Varshney, S; Varshney, A.K.
2006-01-01
The reactions of Bismuth trichloride with Schiff's bases derived from sulpha drugs in 1:1 molar ratio leads to the formation of a new series of coordination compound of Bismuth (III). Their structures have been confirmed on the basis of elemental analysis, ultraviolet, infrared and multinuclear magnetic resonance (1H 13C) spectral studies. The antimicrobial activities of the ligands and their coordination compound have been screened in vitro against the organism Escherichia coli, Stuplhylococus crureus, Prouteus mirabilis, Bacillus thuren giensis, penicilliurn cf.vsogenum, Aspergillns raiger and Fusarium Oxysporum. (author)
12. New ternary tantalum borides containing boron dumbbells: Experimental and theoretical studies of Ta2OsB2 and TaRuB
Science.gov (United States)
Mbarki, Mohammed; Touzani, Rachid St.; Rehorn, Christian W. G.; Gladisch, Fabian C.; Fokwa, Boniface P. T.
2016-10-01
The new ternary transition metal-rich borides Ta2OsB2 and TaRuB have been successfully synthesized by arc-melting the elements in a water-cooled crucible under an argon atmosphere. The crystal structures of both compounds were solved by single-crystal X-ray diffraction and their metal compositions were confirmed by EDX analysis. It was found that Ta2OsB2 and TaRuB crystallize in the tetragonal Nb2OsB2 (space group P4/mnc, no. 128) and the orthorhombic NbRuB (space group Pmma, no. 51) structure types with lattice parameters a=5.878(2) Å, c=6.857(2) Å and a=10.806(2) Å, b=3.196(1) Å, c=6.312(2) Å, respectively. Furthermore, crystallographic, electronic and bonding characteristics have been studied by density functional theory (DFT). Electronic structure relaxation has confirmed the crystallographic parameters while COHP bonding analysis indicates that B2-dummbells are the strongest bonds in both compounds. Moreover, the formation of osmium dumbbells in Ta2OsB2 through a Peierls distortion along the c-axis, is found to be the origin of superstructure formation. Magnetic susceptibility measurements reveal that the two phases are Pauli paramagnets, thus confirming the theoretical DOS prediction of metallic character. Also hints of superconductivity are found in the two phases, however lack of single phase samples has prevented confirmation. Furthermore, the thermodynamic stability of the two modifications of AMB (A=Nb, Ta; M =Ru, Os) are studied using DFT, as new possible phases containing either B4- or B2-units are predicted, the former being the most thermodynamically stable modification.
13. Synthesis, characterization and luminescent properties of mixed phase bismuth molybdate-doped with Eu3+ ions
Science.gov (United States)
Wang, Liyong; Guo, Xiaoqing; Cai, Xiaomeng; Song, Qingwei; Han, Yuanyuan; Jia, Guang
2018-02-01
Red phosphors of Eu3+-doped bismuth molybdate (BMO) are prepared by a low temperature hydrothermal method assisting with Phenol Formaldehyde resin (PFr), and characterized by X-ray diffraction (XRD) patterns, Fourier transform infrared-spectroscopy (FT-IR), thermogravimetric analyzer (TGA), differential thermal analyzer (DTA), and photoluminescence (PL) spectroscopy. PL properties influence factors including molar ratio of Bi3+ and Mo3+ ions, PFr dosage and dopants concentration are discussed in detail. The results show that BMO can act as a useful host for Eu3+ ions doping, and energy transferring from Bi3+ to Eu3+ achieved efficiently, the BMO phosphors displayed intense red color emission under ultraviolet light excitation.
14. Polonium release from an ATW burner system with liquid lead-bismuth coolant
International Nuclear Information System (INIS)
Li, N.; Yefimov, E.; Pankratov, D.
1998-04-01
The authors analyzed polonium release hazards in a conceptual pool-type ATW burner with liquid lead-bismuth eutectic (LBE) coolant. Simplified quantitative models are used based on experiments and real NPP experience. They found little Po contamination outside the burner under normal operating conditions with nominal leakage from the gas system. In sudden gas leak and/or coolant spill accidents, the P contamination level can reach above the regulation limit but short exposure would not lead to severe health consequences. They are evaluating and developing mitigation methods
15. Selective oxidation of propylene to acrolein by hydrothermally synthesized bismuth molybdates
DEFF Research Database (Denmark)
Schuh, Kirsten; Kleist, Wolfgang; Høj, Martin
2014-01-01
Hydrothermal synthesis has been used as a soft chemical method to prepare bismuth molybdate catalysts for the selective oxidation of propylene to acrolein. All obtained samples displayed a plate-like morphology, but their individual aspect ratios varied with the hydrothermal synthesis conditions...... of nitric acid during hydrothermal synthesis enhanced both propylene conversion and acrolein yield, possibly due to a change in morphology. Formation of β-Bi2Mo2O9 was not observed under the applied conditions. In general, the catalytic performance of all samples decreased notably after calcination at 550...
16. The structural studies of vanadium substituted lithium-bismuth-boro-tellurite glass
Science.gov (United States)
2018-05-01
The structural studies of vanadium substituted lithium-bismuth-boro-tellurite glass is successfully prepared and certain analysis like XRD,FTIR,DTA/TGA with density, molar volume are done. The amorphous phase has been identified based on X-ray diffraction analysis. The vanadium oxide plays the role as a glass-modifier and influences on BO3 ↔ BO4 conversion. The observed nonlinear variation in Tg with vanadium oxide increase, it reflects structural changes. The nonlinear variation of density and molar volume can be attributed to vanadium oxide incorporation have increased the number of Non-bridging oxygen (NBO'S).
17. Cerium-modified Aurivillius-type sodium lanthanum bismuth titanate with enhanced piezoactivities
International Nuclear Information System (INIS)
Wang Chunming; Zhao Liang; Wang Jinfeng; Zheng Limei; Du Juan; Zhao Minglei; Wang Chunlei
2009-01-01
The electrical, piezoelectric and dielectric properties of cerium-modified Aurivillius-type sodium lanthanum bismuth titanate (Na 0.5 La 0.5 Bi 4 Ti 4 O 15 , NLBT) ceramics were investigated. It was found the piezoelectric activities of NLBT ceramics were significantly improved by cerium modification. The piezoelectric coefficient d 33 and Curie temperature T c for the 0.50 wt.% cerium-modified NLBT were found to be 29 pC/N and 573 deg. C, respectively. The reasons for piezoelectric activities improvement by cerium modification were given. A small dielectric abnormity was observed in NLBT ceramics, which can be suppressed by cerium modification.
18. Bismuth-doped fibre amplifier operating between 1600 and 1800 nm
Energy Technology Data Exchange (ETDEWEB)
Firstov, S V; Alyshev, S V; Riumkin, K E; Mel' kumov, M A; Dianov, E M [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation); Khopin, V F; Gurjanov, A N [G.G.Devyatykh Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)
2015-12-31
We report the first bismuth-doped fibre amplifier operating between 1600 and 1800 nm, which utilises bidirectional pumping (co-propagating and counter-propagating pump beams) by laser diodes at a wavelength of 1550 nm. The largest gain coefficient of the amplifier is 23 dB, at a wavelength of 1710 nm. It has a noise figure of 7 dB, 3-dB gain bandwidth of 40 nm and gain efficiency of 0.1 dB mW{sup -1}. (letters)
19. Development of Bismuth Hall sensors for ITER steady state magnetic diagnostics.
Czech Academy of Sciences Publication Activity Database
Ďuran, Ivan; Entler, Slavomír; Kočan, M.; Kohout, Michal; Viererbl, L.; Mušálek, Radek; Chráska, Tomáš; Vayakis, G.
2017-01-01
Roč. 123, November (2017), s. 690-694 ISSN 0920-3796. [SOFT 2016: Symposium on Fusion Technology /29./. Prague, 05.09.2016-09.09.2016] R&D Projects: GA MŠk LG14002 Institutional support: RVO:61389021 ; RVO:68378271 Keywords : ITER * Magnetic diagnostic * Hall sensor * Bismuth * Neutron irradiation * Radiation hardness Subject RIV: JF - Nuclear Energetics; JF - Nuclear Energetics (FZU-D) OBOR OECD: Nuclear related engineering; Nuclear related engineering (FZU-D) Impact factor: 1.319, year: 2016 http://www.sciencedirect.com/science/article/pii/S0920379617306956
20. Corrosion of bismuth-based superconductor wires by some atmospheric agents
International Nuclear Information System (INIS)
Ben Azzouz, F.; M'chirgui, A.; Ben Salem, M.; Yangui, B.; Lamine, C.; Nitsche, S.; Boulesteix, C.
2000-01-01
Superconducting wires (SWs) were previously prepared in our group by heat treatment of bismuth-based superconductor coatings on a metal core. This paper presents an analysis of the corrosion process by some atmospheric agents on the SWs. SWs with different concentrations of a (Bi, Pb)-2223 phase have been exposed to water vapour saturated air, to pure water vapour or to dry carbon dioxide. Each of these atmospheric agents was found to act differently on the SWs. However, all the studied corrosion processes present a high sensitivity to the concentration of the (Bi, Pb)-2223 phase. For a higher concentration of this phase, the SWs are less sensitive to atmospheric agents. (author)
1. Superconducting Properties of Lead-Bismuth Films Controlled by Ferromagnetic Nanowire Arrays
Science.gov (United States)
Ye, Zuxin; Lyuksyutov, Igor F.; Wu, Wenhao; Naugle, Donald G.
2011-03-01
Superconducting properties of lead-bismuth (82% Pb and 18% Bi) alloy films deposited on ferromagnetic nanowire arrays have been investigated. Ferromagnetic Co or Ni nanowires are first electroplated into the columnar pores of anodic aluminum oxide (AAO) membranes. Superconducting Pb 82 Bi 18 films are then quench-condensed onto the polished surface of the AAO membranes filled with magnetic nanowires. A strong dependence of the Pb 82 Bi 18 superconducting properties on the ratio of the superconducting film thickness to the magnetic nanowire diameter and the material variety was observed.
2. Laboratory-Scale Bismuth Phosphate Extraction Process Simulation To Track Fate of Fission Products
Energy Technology Data Exchange (ETDEWEB)
Serne, R. JEFFREY; Lindberg, Michael J.; Jones, Thomas E.; Schaef, Herbert T.; Krupka, Kenneth M.
2007-02-28
Recent field investigation that collected and characterized vadose zone sediments from beneath inactive liquid disposal facilities at the Hanford 200 Areas show lower than expected concentrations of a long-term risk driver, Tc-99. Therefore laboratory studies were performed to re-create one of the three processes that were used to separate the plutonium from spent fuel and that created most of the wastes disposed or currently stored in tanks at Hanford. The laboratory simulations were used to compare with current estimates based mainly on flow sheet estimates and spotty historical data. Three simulations of the bismuth phosphate precipitation process show that less that 1% of the Tc-99, Cs-135/137, Sr-90, I-129 carry down with the Pu product and thus these isotopes should have remained within the metals waste streams that after neutralization were sent to single shell tanks. Conversely, these isotopes should not be expected to be found in the first and subsequent cycle waste streams that went to cribs. Measurable quantities (~20 to 30%) of the lanthanides, yttrium, and trivalent actinides (Am and Cm) do precipitate with the Pu product, which is higher than the 10% estimate made for current inventory projections. Surprisingly, Se (added as selenate form) also shows about 10% association with the Pu/bismuth phosphate solids. We speculate that the incorporation of some Se into the bismuth phosphate precipitate is caused by selenate substitution into crystal lattice sites for the phosphate. The bulk of the U daughter product Th-234 and Np-237 daughter product Pa-233 also associate with the solids. We suspect that the Pa daughter products of U (Pa-234 and Pa-231) would also co-precipitate with the bismuth phosphate induced solids. No more than 1 % of the Sr-90 and Sb-125 should carry down with the Pu product that ultimately was purified. Thus the current scheme used to estimate where fission products end up being disposed overestimates by one order of magnitude the
3. Liquid-vapor phase transition upon pressure decrease in the lead-bismuth system
Science.gov (United States)
Volodin, V. N.
2009-11-01
The liquid-vapor phase transitions boundaries were calculated on the basis of the values of vapor pressure of the components in the lead-bismuth system during the stepwise pressure decrease by one order of magnitude from 105 down to 1 Pa. The emergence of azeotropic liquid under pressure lower than 19.3 kPa was ascertained. The emergence of azeotropic mixture near the lead edge of the phase diagram was concluded to be the reason for technological difficulties in the distillation separation of the system into the components in a vacuum.
4. RBEC lead-bismuth cooled fast reactor: review of conceptual decisions
International Nuclear Information System (INIS)
Alekseev, P.; Fomichenko, P.; Mikityuk, K.; Nevinitsa, V.; Shchepetina, T.; Subbotin, S.; Vasiliev, A.
2001-01-01
A concept of the RBEC lead-bismuth fast reactor-breeder is a synthesis, on one hand, of more than 40-year experience in development and operation of fast sodium power reactors and reactors with Pb-Bi coolant for nuclear submarines, and, on the other hand, of large R and D activities on development of the core concept for modified fast sodium reactor. The report briefly presents main parameters of the RBEC reactor, as a candidate for commercial exploitation in structure of the future nuclear power. (author)
5. Performance of neutron activation analysis in the evaluation of bismuth iodide purification methodology
International Nuclear Information System (INIS)
Armelin, Maria Jose A.; Ferraz, Caue de Mello; Hamada, Margarida M.
2015-01-01
Bismuth tri-iodide (BrI 3 ) is an attractive material for using as a semiconductor. In this paper, BiI 3 crystals have been grown by the vertical Bridgman technique using commercially available powder. The impurities were evaluated by instrumental neutron activation analysis (INAA). The results show that INAA is an analytical method appropriate for monitoring the impurities of: Ag, As, Br, Cr, K, Mo, Na and Sb in the various stages of the BiI 3 purification methodology. (author)
6. Photon nuclear scattering on lead and bismuth in the region of the giant resonance
International Nuclear Information System (INIS)
Tamas, Gabriel.
1976-01-01
The results of monochromatic photon nuclear scattering studies on natural lead and bismuth targets are presented. The cross sections for the inelastic scattering leading to the first excited levels of 204 Pb, 206 Pb and 207 Pb are important, in agreement with theoretical predictions. The elastic scattering amplitude is related to the total photon absorption by dispersion relations. It is then possible to determine the spin of resonances excited by the reaction studied. Precise measurements carried out between 14 and 20MeV revealed that the angular distribution cannot be explained by a single dipolar resonance. A quadrupolar resonance at E 2 =14MeV must be introduced [fr
7. Sonochemical synthesis of bismuth(III) nano coordination compound and direct synthesis of Bi.sub.2./sub.O.sub.3./sub. nanoparticles from a bismuth(III) nano coordination compound precursor
Czech Academy of Sciences Publication Activity Database
Roodsari, M.S.; Shaabani, B.; Mirtamizdoust, B.; Dušek, Michal; Fejfarová, Karla
2015-01-01
Roč. 25, č. 5 (2015), s. 1226-1232 ISSN 1574-1443 Grant - others:AV ČR(CZ) Praemium Academiae Institutional support: RVO:68378271 Keywords : nano coordination compound * sonochemical method * intramolecular proton transfer * nano bismuth oxide * isoniazid Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.308, year: 2015
8. Metallothionein bioconjugates as delivery vehicles for bismuth-212 alpha particle therapy
International Nuclear Information System (INIS)
Macklis, R.M.; Morris, C.; Humm, J.; Hines, J.; Atcher, R.
1991-01-01
Metallothioneins (MTHs) are small cysteine-rich polypeptides that binds cationic metals at physiologic pH ranges through noncovalent -SH ligand interactions. Some leucine-rich renal MTHs have a particular avidity for bismuth. The authors have examined the ability of MTHs to selectively incorporate Bi-212, a short-lived high-energy alpha particle emitter currently under exploration as a potential therapeutic radiolabel for use in molecularly targeted cancer therapy. They find that under physiologic conditions, MTH will selectively incorporate Bi-212 after incubation with an equilibrium mixture of its upstream and downstream parents. The MTH moieties may be linked to tumor-binding macromolecules such as antibodies via thiolation reactions using SPDP, and the resultant Bismuth-avid molecules may be used either as primary delivery vehicles for the Bi-212 or as part of a 2-step release-and-catch isotope localization system in which the MTH-antibody conjugate is pre-localized at the tumor site and the radiometal is then administered and chelated in situ. They present the chemistry, dosimetry and potential clinical applications of this system
9. Parameters promoting liquid metal embrittlement of the T91 steel in lead-bismuth eutectic alloy
International Nuclear Information System (INIS)
Proriol Serre, I.; Ye, C.; Vogt, J.B.
2015-01-01
The use of liquid lead-bismuth eutectic (LBE) as a spallation target and a coolant in accelerator-driven systems raises the question of the reliability of structural materials, such as T91 martensitic steel in terms of liquid metal assisted damage and corrosion. In this study, the mechanical behaviour of the T91 martensitic steel was examined in liquid lead-bismuth eutectic (LBE) and in inert atmosphere. Several conditions showed the most sensitive embrittlement factor. The Small Punch Test technique was employed using smooth specimens. In this standard heat treatment, T91 appeared in general as a ductile material, and became brittle in the considered conditions if the test was performed in LBE. It turns out that the loading rate appeared as a critical parameter for the occurrence of liquid metal embrittlement (LME) of the T91 steel in LBE. Loading the T91 very slowly instead of rapidly in oxygen saturated LBE resulted in brittle fracture. Furthermore, low-oxygen content in LBE and an increase in temperature promote LME. (authors)
10. Strain effect on the heat transport properties of bismuth telluride nanofilms with a hole
Science.gov (United States)
Fang, Te-Hua; Chang, Win-Jin; Wang, Kuan-Yu; Huang, Chao-Chun
2018-06-01
We investigated the mechanical behavior of bismuth telluride nanofilms with holes by using an equilibrium molecular dynamics (MD) approach. The holes had diameters of 20, 30, 40, and 50 Å. The thermal conductivity values of the nanofilms were calculated under different strains at different temperatures using a nonequilibrium MD simulation. The simulation revealed that the thermal conductivity of a bismuth telluride nanofilm with a hole decreases with an increase in hole diameter at different strains. For a film with a perfect structure at 300 K, a 48% reduction (from 0.33 to 0.17 W/m K) in the thermal conductivity was observed at a 7% tensile strain. In addition, the thermal conductivity increased by approximately 39% (from 0.33 to 0.46 W/m K) at a 7% compressive strain. A very low value (0.11 W/m K) of thermal conductivity is obtained for the nanofilm with a hole diameter of 50 Å at a 7% tensile strain at 300 K.
11. Thermodynamic properties and equation of state of liquid lead and lead bismuth eutectic
Science.gov (United States)
Sobolev, V. P.; Schuurmans, P.; Benamati, G.
2008-06-01
Since the 1950s, liquid lead (Pb) and lead-bismuth eutectic (Pb-Bi) have been studied in the USA, Canada and in the former-USSR as potential coolants for nuclear installations due to their very attractive thermophysical and neutronic properties. However, experimental data on the thermal properties of these coolants in the temperature range of interest are still incomplete and often contradictory. This makes it very difficult to perform design calculations and to analyse the normal and abnormal behaviour of nuclear installations where these coolants are expected to be used. Recently, a compilation of heavy liquid metal (HLM) properties along with recommendations for its use was prepared by the OECD/NEA Working Party on Fuel Cycle (WPFC) Expert Group on Lead-Bismuth Eutectic Technology. A brief review of this compilation and some new data are presented in this article. A set of correlations for the temperature dependence of the main thermodynamic properties of Pb and Pb-Bi(e) at normal pressure, and a set of simplified thermal and caloric equations of state for the liquid phase are proposed.
12. Capacity extended bismuth-antimony cathode for high-performance liquid metal battery
Science.gov (United States)
Dai, Tao; Zhao, Yue; Ning, Xiao-Hui; Lakshmi Narayan, R.; Li, Ju; Shan, Zhi-wei
2018-03-01
Li-Bi based liquid metal batteries (LMBs) have attracted interest due to their potential for solving grid scale energy storage problems. In this study, the feasibility of replacing the bismuth cathode with a bismuth-antimony alloy cathode in lithium based LMBs is investigated. The influence of the Bi:Sb ratio on voltage characteristics is evaluated via the constant current discharge method and electrochemical titration. On observing the cross section of the electrode at various stages of discharge, it is determined that both Sb and Bi form solid intermetallics with Li on the cathode. Additionally, the addition of Bi not only reduces the melting temperature of the Bi:Sb intermetallic but also actively contributes to the electrode capacity. Thereafter, a Li|LiCl-LiF|Sb-Bi liquid metal battery with 3 A h nameplate capacity, assembled and cycled at 1 C rate, is found to possess a stable capacity for over 160 cycles. The overall performance of this battery is discussed in the context of cost effectiveness, energy and coulombic efficiencies.
13. Outstanding visible photocatalytic activity of a new mixed bismuth titanatate material
Energy Technology Data Exchange (ETDEWEB)
Zambrano, P. [Instituto de Ciencia de Materiales de Sevilla, CSIC-Universidad de Sevilla, Americo Vespucio 49, 410092, Sevilla (Spain); Departamento Cristalografía, Mineralogía y Química Agrícola, Universidad de Sevilla, C/Profesor García González s/n, 41012 Sevilla (Spain); Sayagués, M.J.; Navío, J.A. [Instituto de Ciencia de Materiales de Sevilla, CSIC-Universidad de Sevilla, Americo Vespucio 49, 410092, Sevilla (Spain); Hidalgo, M.C., E-mail: [email protected] [Instituto de Ciencia de Materiales de Sevilla, CSIC-Universidad de Sevilla, Americo Vespucio 49, 410092, Sevilla (Spain)
2017-02-01
Highlights: • Photocatalyst based on bismuth titanates with high visible activity. • Its visible activity as high as UV activity of TiO{sub 2} P25 for phenol degradation. • Photocatalyst is majority of phase Bi{sub 20}TiO{sub 32} with Bi{sub 4}Ti{sub 3}O{sub 12} and amorphous TiO{sub 2}. • High visible activity due to low BG, interconnected phases and high surface area. - Abstract: In this work, a new photocatalyst based on bismuth titanates with outstanding visible photocatalytic activity was prepared by a facile hydrothermal method. The synthesised material showed visible activity as high as UV activity of commercial TiO{sub 2} P25 under the same experimental conditions for phenol degradation. A wide characterisation of the photocatalyst was performed. The material was composed of three phases; majority of Bi{sub 20}TiO{sub 32} closely interconnected to Bi{sub 4}Ti{sub 3}O{sub 12} and amorphous TiO{sub 2}. The high visible activity showed by this material could be ascribed to a combination of several features; i.e. low band gap energy value (2.1 eV), a structure allowing a good separation path for visible photogenerated electron-holes pairs and a relatively high surface area. This photocatalyst appeared as a promising material for solar and visible applications of photocatalysis.
14. Corrosion behavior of steels in liquid lead bismuth with low oxygen concentrations
Science.gov (United States)
Kurata, Yuji; Futakawa, Masatoshi; Saito, Shigeru
2008-02-01
Corrosion tests in pots were conducted to elucidate corrosion behavior of various steels in liquid lead-bismuth for 3000 h under the condition of an oxygen concentration of 5 × 10 -8 wt% at 450 °C and an oxygen concentration of 3 × 10 -9 wt% at 550 °C, respectively. Significant corrosion was not observed at 450 °C for ferritic/martensitic steels, F82H, Mod.9Cr-1Mo steel, 410SS, 430SS except 2.25Cr-1Mo steel. Pb-Bi penetration into steels and dissolution of elements into Pb-Bi were severe at 550 °C even for ferritic/martensitic steels. Typical dissolution attack occurred for pure iron both at 550 °C without surface Fe 3O 4 and at 450 °C with a thin Fe 3O 4 film. Ferritization due to dissolution of Ni and Cr, and Pb-Bi penetration were recognized for austenitic stainless steels, 316SS and 14Cr-16Ni-2Mo steel at both temperatures of 450 °C and 550 °C. The phenomena were mitigated for 18Cr-20Ni-5Si steel. In some cases oxide films could not be a corrosion barrier in liquid lead-bismuth.
15. Development and Testing of an Americium/Lanthanide Separation Flowsheet Using Sodium Bismuthate
Energy Technology Data Exchange (ETDEWEB)
Jack Law; Bruce Mincher; Troy Garn; Mitchell Greenhalgh; Nicholas Schmitt; Veronica Rutledge
2014-04-01
The separation of Am from the lanthanides and curium is a key step in proposed advanced fuel cycle scenarios. The partitioning and transmutation of Am is desirable to minimize the long-term heat load of material interred in a future high-level waste repository. A separation process amenable to process scale-up remains elusive. Given only subtle chemistry differences within and between the ions of the trivalent actinide and lanthanide series this separation is challenging ; however, higher oxidation states of americium can be prepared using sodium bismuthate and separated via solvent extraction using diamylamylphosphonate (DAAP) extraction. Among the other trivalent metals only Ce is also oxidized and extracted. Due to the long-term instability of Am(VI) , the loaded organic phase is readily selectively stripped to partition the actinide to a new acidic aqueous phase. Batch extraction distribution ratio measurements were used to design a flowsheet to accomplish this separation. Additionally, crossflow filtration was investigated as a method to filter the bismuthate solids from the feed solution prior to extraction. Results of the filtration studies, flowsheet development work and flowsheet performance testing using a centrifugal contactor are detailed.
16. Evaluation in the use of bismuth shielding on cervical spine CT scan using a male phantom
International Nuclear Information System (INIS)
Aleme, C.; Mourao, A. P.; Lyra, M. A.
2014-08-01
The cervical spine is the region of the column that articulates the head and chest. The tests of computed tomography (CT) performed in this region have as main objectives to diagnose fractures, dislocations and tumors. In CT scans the cervical spine volume is limited by the foramen Magnum and the first thoracic vertebra. In this region is the thyroid that is directly irradiated by X-ray beam during cervical scan. Based on this information, it was studied the dose variation deposited in thyroid and in nearby organs, such as: lenses, spinal cord in the foramen Magnum region and breasts, with and without the use of bismuth protector. In this study was used a male anthropomorphic phantom and thermoluminescent s dosimeters (TLD-100) were required to register the individual doses in the organs of interest. CT scans were performed on a GE Bright Speed scanner of 32 channels. With the data obtained, it was found the organ dose variation. The largest recorded dose was in the thyroid. Comparing two scans it was possible to note that the use of the bismuth protector promoted a 26% reduction in the thyroid dose and an increase in the lens dose. (Author)
17. Vibration Monitoring Using Fiber Optic Sensors in a Lead-Bismuth Eutectic Cooled Nuclear Fuel Assembly
Directory of Open Access Journals (Sweden)
Ben De Pauw
2016-04-01
Full Text Available Excessive fuel assembly vibrations in nuclear reactor cores should be avoided in order not to compromise the lifetime of the assembly and in order to prevent the occurrence of safety hazards. This issue is particularly relevant to new reactor designs that use liquid metal coolants, such as, for example, a molten lead-bismuth eutectic. The flow of molten heavy metal around and through the fuel assembly may cause the latter to vibrate and hence suffer degradation as a result of, for example, fretting wear or mechanical fatigue. In this paper, we demonstrate the use of optical fiber sensors to measure the fuel assembly vibration in a lead-bismuth eutectic cooled installation which can be used as input to assess vibration-related safety hazards. We show that the vibration characteristics of the fuel pins in the fuel assembly can be experimentally determined with minimal intrusiveness and with high precision owing to the small dimensions and properties of the sensors. In particular, we were able to record local strain level differences of about 0.2 μϵ allowing us to reliably estimate the vibration amplitudes and modal parameters of the fuel assembly based on optical fiber sensor readings during different stages of the operation of the facility, including the onset of the coolant circulation and steady-state operation.
18. Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO
Energy Technology Data Exchange (ETDEWEB)
Spencer, B.B.
1995-08-01
DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660{plus_minus}0.092 at 25 C, and extraction enthalpy is -5. 46{plus_minus}0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1.213 {times} 10{sup 6}{plus_minus}3.56 {times} 10{sup 4} at 25 C; reaction enthalpy was -9.610{plus_minus}0.594 kcal/mol. Nitration complexation constant is 8.412{plus_minus}0.579, with an enthalpy of -10.72{plus_minus}1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of (perhaps) 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured.
19. Extraction of nitric acid, uranyl nitrate, and bismuth nitrate from aqueous nitric acid solutions with CMPO
International Nuclear Information System (INIS)
Spencer, B.B.
1995-08-01
DOE sponsored development of the transuranium extraction (TRUEX) process for removing actinides from radioactive wastes. The solvent is a mixture of CMPO and TBP. Since the extraction characteristics of CMPO are not as well understood as those of TBP, the extraction of nitric acid, uranyl nitrate, and bismuth nitrate with CMPO (dissolved in n-dodecane) were studied. Results indicate that CMPO extracts nitric acid with a 1:1 stoichiometry; equilibrium constant is 2. 660±0.092 at 25 C, and extraction enthalpy is -5. 46±0.46 kcal/mol. Slope analysis indicates that uranyl nitrate extracts with a mixed equilibria of 1:1 and 2:1 stoichiometries in nearly equal proportion. Equil. constant of the 2: 1 extraction was 1.213 x 10 6 ±3.56 x 10 4 at 25 C; reaction enthalpy was -9.610±0.594 kcal/mol. Nitration complexation constant is 8.412±0.579, with an enthalpy of -10.72±1.87 kcal/mol. Bismuth nitrate also extracts with a mixed equilibria of (perhaps) 1:1 and 2:1 stoichiometries. A 2:1 extraction equilibrium and a nitrate complexation adequately model the data. Kinetics and enthalpies were also measured
20. Methylammonium Bismuth Iodide as a Lead-Free, Stable Hybrid Organic-Inorganic Solar Absorber.
Science.gov (United States)
Hoye, Robert L Z; Brandt, Riley E; Osherov, Anna; Stevanović, Vladan; Stranks, Samuel D; Wilson, Mark W B; Kim, Hyunho; Akey, Austin J; Perkins, John D; Kurchin, Rachel C; Poindexter, Jeremy R; Wang, Evelyn N; Bawendi, Moungi G; Bulović, Vladimir; Buonassisi, Tonio
2016-02-18
Methylammonium lead halide (MAPbX3 ) perovskites exhibit exceptional carrier transport properties. But their commercial deployment as solar absorbers is currently limited by their intrinsic instability in the presence of humidity and their lead content. Guided by our theoretical predictions, we explored the potential of methylammonium bismuth iodide (MBI) as a solar absorber through detailed materials characterization. We synthesized phase-pure MBI by solution and vapor processing. In contrast to MAPbX3, MBI is air stable, forming a surface layer that does not increase the recombination rate. We found that MBI luminesces at room temperature, with the vapor-processed films exhibiting superior photoluminescence (PL) decay times that are promising for photovoltaic applications. The thermodynamic, electronic, and structural features of MBI that are amenable to these properties are also present in other hybrid ternary bismuth halide compounds. Through MBI, we demonstrate a lead-free and stable alternative to MAPbX3 that has a similar electronic structure and nanosecond lifetimes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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http://math.stackexchange.com/questions/167606/eq-4-of-bils-and-klenow-2000/167615
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# Eq (4) of Bils and Klenow (2000)
I hope some of you read Economics. I was wondering if anyone can help me in deriving equation (4):
$\ln A_{i}\left( t\right) =\beta\ln h_{i}\left( t\right) +\ln\bar{A}\left( t\right) +\xi_{i}\left( t\right)$,
in the following article:
Notation:
$\bar{A}:$ the exogenously growing “world technology frontier”,
$h_{i}(t):$ the average level of human capital in country $i$,
$\beta:$ discount rate,
$A_{i}:$ technology level in country $i$ at time $t$ and
$\xi_{i}:$ some kind of error (not sure)
Thanks
update: I've updated the link - it's from P. Klenow's website.
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Well, not everyone is in the mood for opening that page and look for equation number four, could you add it to your question? – Gigili Jul 6 '12 at 20:36
It essentially says that you should stay in education until the marginal discounted cost of tuition including wages foregone at your skill level at that time is equal to the discounted difference between the wages from marginal skill gains from education and the wages from skill gains from work experience, taking account remaining lifespan in which these wages are earned.
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Please be less sparing with your commas :) (or otherwise avoid having a three-line sentence without a pause for breath) – Ben Millwood Jul 6 '12 at 21:36
I think the punctuation is flawless. If you read it silently you won't run out of air. :) – daniel Jul 6 '12 at 22:25
@Henry Thanks, but I couldn't make a connection between your answer and Equation (4). All I can see is that higher level of human capital ($H$) [schooling is the only form considered here] triggers higher level of technology adoption ($A$). ... Anyway, back to the original question: how did they reach Eq. (4)? – bakul Jul 7 '12 at 13:31
@bakul: I followed a link in the comments (perhaps since deleted) to a paper whose equation 4 was similar to but not the same as equation 11 in the current link. – Henry Jul 7 '12 at 14:37
@Henry Probably Moderator removed the post. Anyway, I think you're probably referring to the NBER version of the paper. nber.org/papers/w6393 -- Anyway, to avoid confusion, please see the AER version linked from Klenow's website in the 1st post. – bakul Jul 7 '12 at 15:41
Considering the context within economics and, more specifically, econometrics, it's sort of a log-log equation of relations between the variables you listed.
So, consider that $\bar{A}$ is exogenous. Thus, it is not determined by the equation and inherently considered to be a constant.
$A_i(t)$ corresponds to the level of technology at time $t$ and is the subject this equation seeks to model. To get the non-linear parent distribution from which the motivation of this equation came, consider the transformation of raising $e$ to the power of both sides. Simplification will yield: $$A(t) = \bar{A}(t)\,h(t)^{\beta}$$
Now consider it "intuitively". This equality says that the level of technology in a country at a given time, $t$, is determined by an arbitrary "technology frontier" at time $t$, $\bar{A}(t)$, multiplied by the average level of human capital (education) which is $h_i(t)$ raised to the power of the discount rate, $\beta$.
You can think of the discount rate as the amount of "resources", I guess, devoted to education. Read about the social discount rate for a better idea of what that might be modeling. The equation tells you that the level of technology at a given time is determined by the amount of technology which exists already multiplied by the discounted level of human capital at that time. In ultra-laymen's terms: The new level of technology is determined by the old level of technology magnified by the amount of education people are receiving.
Henry's description seems probably more accurate given the context of the article. I didn't actually read it. I was just speaking off what you posted here. Hopefully my words help you see a little bit more of where they might have gotten the idea for this model.
Edit: The reason they log both sides is so they can develop a $\textbf{linear}$ model to extrapolate $A_i(t)$ for values of $h_i(t)$ within an error of $\xi$ from the linear model. $\xi$ usually follows a distribution $N$~($0, var(\xi)$).
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Thanks for your help. I'll look into it – bakul Jul 13 '12 at 6:50
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https://testbook.com/question-answer/if-the-gross-weight-of-the-soil-w-and-the-weight--60642a6fdf98379103f2e773
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# If the gross weight of the soil = W and the weight of solid particles = WS, then the value of water content will be -
This question was previously asked in
UPPCL JE CE Offical Paper I 2014
View all UPPCL JE Papers >
1. (W / WS) - 1
2. 1 + (W / WS)
3. 1 - (W / WS)
4. (WS / W) + 1
Option 1 : (W / WS) - 1
Free
CT 1: Network Theory 1
11207
10 Questions 10 Marks 10 Mins
## Detailed Solution
Concept:
It is the ratio of weight of water (Ww) to the weight of solid (Ws) of the sample.
$$W=\dfrac{W_W}{W_S}$$
Total weight of soil = W = (W+ Ws)
Hence, weight of water = (W - Ws) put in above equation
$$W=\dfrac{W-W_S}{W_S}$$
∴ $$W=\dfrac{W}{W_S}-1$$
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http://www.sisef.it/iforest/contents/?id=ifor3556-014
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## Modeling of time consumption for selective and situational precommercial thinning in mountain beech forest stands
iForest - Biogeosciences and Forestry, Volume 14, Issue 2, Pages 137-143 (2021)
doi: https://doi.org/10.3832/ifor3556-014
Research Articles
Rationalization and optimization of work is becoming increasingly important in the European forestry sector. In this study a tool for modeling three different precommercial thinning approaches in young beech mountain stands was developed based on several field studies. The simulation examines three primary types of precommercial thinning: selective thinning and two types of situational thinning. We studied the impact of the number of candidates/crop trees and the impact of harvesting intensity on the structure and consumption of productive time. We found that in terms of costs situational precommercial thinning is more rational than selective precommercial thinning, that harvesting intensity has a significant impact on time consumption and that the number of candidates or crop trees has a significant impact on time consumption as well as on the relationships between main and auxiliary productive time. The modeling has shown that situational thinning is an alternative to selective thinning and that, in addition to requiring smaller and more efficient harvesting machines, it offers a cost-effective and ergonomic option (more walking, less chainsaw operation) for the pre-commercial thinning of young forest.
# Introduction
Although the forest industry often focuses on economic results, the market is directly tied to the sustainable long-term management of forest ecosystems ([27]). The precommercial thinning of young forest stands is beneficial for the quality of selected trees, species mixture, forest stability and biodiversity ([12], [21], [23]). However, these benefits only become noticeable after a delay ([28]), and the effects of thinnings are difficult to evaluate directly due to long production cycles. Thinnings of the earlier developmental stages of the forest play an essential role in the development of mature forest stands ([21]). From an economic point of view, however, precommercial thinning today may represent a relatively uncertain investment in the future forest due to the increasing risk of natural disturbances related to climate change ([17], [30]).
In Central Europe (e.g., Switzerland, Slovenia, Italy) selective thinning begins in pole-stage stands and continues to mature stands, when it is replaced by increment or crown thinning ([33], [31]). The first entries are in mixed stands of light-demanding species after the thicket phase, which means a relatively large number of candidates (for future crop trees) per unit area (1500-2000 per ha). As a result, many trees favored as candidates in earlier thinnings become competitors or indifferent trees in subsequent thinning interventions, which renders previous interventions somewhat ecologically and economically unjustified ([3]). Comparative studies of untreated and thinned stands have also shown the negative impact of selective thinning on the course of self-differentiation and collective stand stability of forest stands ([4]). Due to the frequent interventions throughout the stand as a result of selective thinning, self-differentiation is impeded when compared to less intensive thinning approaches or stands with no intervention ([4]).
During the last three decades, negative economic results have triggered criticism of selective thinning in young stands due to (i) rising labor costs in relation to the declining market price of timber, (ii) the social and economic situation of forest owners (e.g., employment outside forestry, declining forestry skills), (iii) increased investment risks due to frequent natural disturbances (e.g., concerns about the decline of collective stability) and (iv) difficulty in justifying four to six precommercial tending interventions ([16], [33]).
In some respects, the practice of choosing a large number of candidates for selective thinning at younger developmental stages of a forest is seen as controversial. First, in theory the distance between crop trees cannot increase continuously as predicted by selective thinning; rather, it is more likely a multiple of the initial distance. Second, the collective stability of stands is often neglected for the sake of the stability of individual trees. Collective stability is significantly reduced because of the more frequent, all-encompassing and intensive interventions specific to selective thinning in Central Europe ([40]).
In the face of difficult environmental and economic conditions, tending models are in need of improvement. They must take into account the economic viability of interventions and the consequences of skipping some interventions for long-term stand development. The overarching goal should be to reduce labor costs and improve revenue for the forest owner without jeopardizing the functioning of the forest at the ecosystem level.
In the second half of the last century, situational tending emerged as an alternative model of tending young forest stands in Central Europe ([36]). It was developed under the influence of rationalization of selective thinning ([3]) by concentrating from the onset of interventions on a small number of future crop trees which are strictly favored until the regeneration (German “Z-Baum’’ - [2], [4]). Their number depends on the tree species, the thinning method (thinning at half-final or final distance between crop trees - [4]) and the target diameter of the forest stand ([18]).
This paper focuses on precommercial situational thinning, which is primarily intended for the tending of monodominant and mixed even-aged stands. These types of managed forest stands are globally dominant and will continue to be important due to the increasing frequency and intensity of natural disturbances.
The fields of traditional and fully mechanized harvesting for commercial thinning appear to be well researched from the standpoint of time studies ([14]). On the other hand, precommercial thinning and tending has been somewhat neglected from the standpoint of forestry operation research and productivity, although it accounts for 12-15% of costs within the forest rotation period ([16]). Despite several decades of development and testing of situational precommercial thinning, no detailed studies have been conducted on reducing workload in relation to the smaller number of selected future crop trees; there are only some estimates ([3]). While some literature already exists pertaining to the use of mechanized harvesting during precommercial thinning ([20], [8], [9]), there is a lack of knowledge regarding the optimization of motor-manual thinning during precommercial forest operations.
In order to evaluate the differences between situational and selective precommercial thinning, we developed a computer program for thinning simulation based on three previously conducted studies dealing with precommercial thinning of beech stands in Slovenia ([19], [26], [6]). The program is designed to model candidates or future crop tree position networks and remove competitors using three different thinning intensities for selective precommercial thinning and two alternatives of situational precommercial thinning. The research sought to determine: (i) how working time structure and productivity change with the number of selected candidates/future crop trees; (ii) how working time structure and productivity change with increasing thinning intensity; and (iii) differences in the costs of performing different types of precommercial thinning, based on the principle of concentration.
# Materials and methods
We developed a program to simulate three different alternatives for the precommercial thinning of young beech stands in mountain forests using MS Visual Basic for Applications ([1]). In the simulation process, we included three different thinning systems: (i) selective precommercial thinning (ST1800), which in this case refers to the precommercial thinning of a stand in the sapling development stage with approximately 1800 selected candidates per ha; (ii) situational thinning at half-final distances (ST400) with approximately 400 selected candidates for crop trees per hectare; (iii) and situational thinning at final distances (ST100) with 100 selected crop trees per ha.
## Thinning simulation algorithm
The thinning simulation algorithm is divided into seven procedures: (1) setting the number of simulations; (2) randomly selecting candidate/crop tree positions; (3) determining the processing sequence (walking/processing path); (4) calculating the distance between candidates/crop trees; (5) determining thinning intensity; (6) simulating DBH and productivity; and (7) data management and storage of the individual simulation (Fig. 1).
Fig. 1 - Scheme of the thinning modeling program.
## Number of simulations
At the beginning of the modeling process, the user first sets the number of thinning simulation repetitions. We generated 1000 simulations for each combination of precommercial thinning approach and thinning intensity ([13]).
## Random positioning of selected candidates/crop trees
The virtual plot represents a 1000 m2 rectangular forest area with 1056 cells, each with a unique location identification number (ID) starting at 1 in the upper left corner and ending with ID 1056 in the lower right corner (32 columns and 33 rows). The cell ID is intended to identify the positions of the candidate trees within the virtual plot. The program selects a random number between 1 and 1056 when choosing the positions of crop trees based on the minimum distance between neighboring crop trees, which depends on the thinning system (ST1800 - 1; ST400 - 2; ST100 - 5 free cells). The number of crop trees in the virtual plot varies randomly for each simulation and depends on the thinning system (ST1800: between 171 and 189 candidates; ST400: between 36 and 44 crop trees; SR100: between 8 and 12 crop trees).
## Determination of processing sequence
The tending operation sequence (virtual worker walking path) between selected crop trees depends on the division of the virtual plot into bands. The bands assist in determining the direction of the harvesting movement during the tending operation. Walking paths are established on the virtual plots systematically in right-to-left or opposite bands, and the band width depends on the thinning system (ST1800: 3 rows; ST400: 7 rows [last 5]; ST100: 11 rows - see Fig. S1 in Supplementary material).
The thinning intervention begins in the upper left corner of the virtual plot in each of the thinning systems and repetitions. The sequence of crop tree processing depends on the direction of virtual worker movement in a band (left or right) and on the column ID of a crop tree (cell location) in the virtual plot. If the direction of processing is to the right (left), the crop trees process in ascending order (descending) according to the column ID. In the case where two cells with crop trees in one band are distributed with the same column, the one whose row label ID is lower takes priority (the upper one).
## Calculation of walking time between candidates/crop trees
The simulation calculates the mutual distances between subsequently processed candidates/crop trees. The calculation of mutual distances (R) simply uses Pythagoras’ theorem (eqn. 1), where x represents the absolute distance between columns of neighboring candidate/crop trees in a virtual plot (Idi and Idi+1 - eqn. 2) and y represents the absolute distance between rows of neighboring candidate trees in a virtual plot (Idz and Idz+1, - eqn. 3).
$$R = \sqrt {x^2 + y^2}$$
$$x = \left| Id_{i+1} -Id_{i} \right|$$
$$y = \left| Id_{z+1} - Id_{z} \right|$$
To convert our model distances to actual distances, the simulation program multiplied x by 0.99 (31.62 m in nature/32 columns) and y by 0.96 (31.62 m in nature/33 rows). The walking speed in the virtual plot was taken from previous research conducted in Slovenia ([5], [6]). At an average density of 43.950 trees per ha, with an average DBH of 4.8 cm and terrain slope of 70%, the average walking speed was 5.7 seconds per meter of horizontal distance. To account for the heterogeneity of stand density (43.950 ± 4.000 trees per ha), we calculated the following auxiliary productive time (time spent walking between subsequently selected crop trees - AT). The walking speed (H) for each movement between neighboring candidates or crop trees was randomly determined in the range of 5.7 ± 0.5 seconds per meter and multiplied by the distances between neighboring crop trees (eqn. 4). The variability of the walking speed was assumed based on the heterogeneity of stand density in which the previous study was carried out ([5]).
$$AT = R \cdot H$$
## Determination of thinning intensity
Thinning intensity was determined by the number of competitors per candidate/crop tree. An algorithm for each of the individual candidates or crop trees selects a specific number of competitors from a pre-specified range of possible numbers for each of the three types of thinning intensity. In order to determine the impact of thinning intensity on the performance of tending operations, we ran 1000 thinning simulations and the associated thinning operation for weak (1.5 - competitors per selected crop tree), normal (2) and high thinning intensity (2.5) for each thinning system (Tab. S1 in Supplementary material). The thinning intensities used mimic methods for selection of competitors carried out by the public forestry service in Slovenia. For the first pre-commercial entry, due to the small size of the trees, densities are used to indicate the thinning intensity and not the basal area of the stand as in the following entries. The development of the model was based on data from studies on the first thinning entries ([5]).
## Determination of candidate and crop tree diameter and calculation of main productive time
The model stand DBH of the candidates and crop trees was generated using data previously collected in Slovenia. The average DBH of candidates was 4.8 cm, the standard deviation was 1.13 cm, the minimum DBH was 3.5 cm and the maximum DBH was 8.1 cm ([5]).
Due to the lack of competitor DBH data in previous studies, we used the DBH of candidates (x) and its dispersion to derive a productive time equation ([19], [26], [5]). The main productive time (y) was calculated using an exponential equation ([22], [7] - eqn. 5) and according to the number of competitors assigned to each selected candidate/crop tree within an individual precommercial thinning simulation. The input data of previous studies are also briefly presented in the supplementary material (Tab. S2 in Supplementary material).
$$y=0.3081 e^ {0.0719x}$$
## Data management and storage of individual simulations
For each thinning simulation, the results were recorded and stored in a database in three levels. At the first level, results were recorded for each selected candidate/crop tree in the individual simulations (ID, diameter, walking distance, number of competitors, main productive time, auxiliary productive time and the walking speed between the previous and subsequent candidate/crop tree). At the second level, summaries at the simulation level included data on the average diameter, average distance between candidate/crop trees, total number of competitors, total main productive time, auxiliary productive time and average walking speed. The results in the third and final level were summarized in a one-hectare virtual plot.
## Information about the simulation model
The thinning simulation model presented in this work is based on time studies and data from the precommercial thinning of a young mountain beech forest with an average terrain slope of between 50-70%, an average tree DBH of 4.8 ± 1.1 cm, a stand density of 43.950 ± 4.000 trees per hectare, limestone bedrock and 100% vegetation coverage ([6] - see Tab. S3 in Supplementary material). The simulation model is applicable to all other terrain situations and tree species with previously conducted detailed time studies of thinning to enable the reconstruction of factors needed for the simulation model.
## Statistical analysis
Due to a large difference in the number of candidates and also in time consumption among the three tested thinning systems (ST1800, ST400 and ST100 - Tab. 1), we only statistically tested the impact of thinning intensity. Due to the none-normally distributed data, statistical tests were performed using the Kruskal-Wallis test, which is a non-parametric ANOVA test.
Tab. 1 - Labor costs per hectare for the precommercial thinning of a young beech stand using different thinning approaches and different thinning intensities (TI). (ST1800): selective thinning; (ST400); situational thinning at half-final distances; (ST100): situational thinning at final distances. A coefficient of unproductive time for calculating working time and labor cost per working hour data was taken from previous research in Slovenia ([5]). (*): reduction of cost regarding to selective thinning - Normal TI.
Thinning
approach
TI Productive time
(h ha-1)
Working time
(h ha-1)
Labor costs
(€ ha-1)
Influence of TI
(share of normal TI)
Reduction
of cost *
ST1800 Weak 27.1 ± 0.9 42.8 ± 1.4 1052 ± 34 80 ± 2 -
Normal 33.7 ± 1.2 53.3 ± 1.9 1311 ± 47 100
High 40.4 ± 1.5 63.9 ± 2.5 1572 ± 60 120 ± 4
ST400 Weak 7.6 ± 0.5 12.0 ± 0.8 296 ± 19 83 ± 4 73 ± 4 %
Normal 9.2 ± 0.6 14.5 ± 1.0 356 ± 25 100
High 10.7 ± 0.8 16.8 ± 1.2 414± 30 116 ± 7
ST100 Weak 2.8 ± 0.3 4.5 ± 0.5 110 ± 12 88 ± 6 90 ± 1 %
Normal 3.2 ± 0.4 5.1 ± 0.6 125 ± 15 100
High 3.6 ± 0.5 5.7 ± 0.7 140 ± 18 112 ± 10
The relationship between time consumption (TC) and the number of candidate/crop trees per hectare (NCT) for each category of thinning intensity was a result of the none-normally distributed and heteroscedastic data predicted by a general linear model (eqn. 6):
$$TC = NCT \cdot k + \varepsilon$$
where k represents the slope and ε is the interception of the general linear model.
Logarithmic regression models were used to predict the relationships between elements of time structure (ETS) and the number of candidate trees per hectare (NCT) for each of the thinning intensities (eqn. 7):
$$ETS = log (NCT) \cdot k + \varepsilon$$
where k represents the slope and ε is the interception of of the lin-log model.
## Cost analysis
In order to compare thinning systems in terms of costs, productive time was first converted into working time using the coefficient of unproductive time from the national standard times for forest operation. The labor costs (€ 24.6 per working hour) were based on a previous survey in which a cost calculation was done for a chainsaw worker ([5]).
# Results
## Productive time
The productive time during precommercial thinning operations in young mountain beech stands increases linearly with the number of candidates/crop trees per ha (Fig. 2). The time consumption was 3.2 h ha-1 for situational precommercial thinning at a normal thinning intensity with final distances (ST100), 9.2 h ha-1 for situational precommercial thinning with half-final distances (ST400) and 33.7 h ha-1 for selective precommercial thinning (ST1800).
Fig. 2 - Productive time in hours per hectare, depending on the number of candidates/crop trees per hectare with high (red), normal (blue) and weak (green) thinning of a young beech mountain stand.
Thinning intensity also has a significant influence on time consumption (Kruskal-Wallis test; ST1800: χ2 = 26.569, p <0.001; ST400: χ2 = 2573, p <0.001; ST100: χ2 = 1920, p <0.001). The average consumption of productive time varied from normal thinning intensity by ± 6.5 h ha-1 for selective precommercial thinning (ST1800) depending on the variation in thinning intensity from weak to strong, by ± 1.5 h ha-1 for situational precommercial thinning at half-final distances (ST400) and by ± 0.4 h ha-1 for situational precommercial thinning at final distances.
## Main productive time
Analysis of the relationship between the proportion of main productive time and the number of candidates/crop trees in the precommercial thinning of young beech mountain stands showed that the data are distributed in the form of an increasing logarithmic curve (high thinning intensity: p <0.001, R2 = 0.936; normal thinning intensity: p <0.001, R2 = 0.947; weak thinning intensity: p <0.001, R2 = 0.966 - Fig. 3). In addition to the influence of the number of candidates or crop trees per hectare, a significant effect of thinning intensity was also observed (Kruskal-Wallis test; ST1800: χ2 = 2968.8, p <0.001; ST400: χ2 = 2891.6, p <0.001; ST100: χ2 = 2597.2, p <0.001).
Fig. 3 - Impact of the number of candidates/crop trees on the proportion of main productive time in high (red), normal (blue) and weak (green) thinning intensity of a young beech stand.
## Auxiliary productive time
An analysis of the relationship between the share of auxiliary productive time (movements) within productive time and the number of candidate/crop trees showed that, irrespective of thinning intensity, auxiliary productive time depends on the number of candidates or crop trees. The data are distributed in the form of a descending logarithmic curve (high thinning intensity: p <0.001, R2 = 0.936; normal thinning intensity: p <0.001, R2 = 0.947; weak thinning intensity: p <0.001, R2 = 0.966 - Fig. 4). In addition to the number of candidates or crop trees, thinning intensity is also significantly affected by the auxiliary productive timeshare (Kruskal-Wallis test; ST1800: χ2 = 2968.8, p <0.001; ST400: χ2 = 2891.6, p <0.001; ST100: χ2 = 2597.2, p <0.001).
Fig. 4 - Impact of the number of candidates/crop trees on the share of auxiliary productive time in high (red), normal (blue) and weak (green) thinning intensity of a young beech mountain stand.
## Cost analysis
Working time consumption was dependent on the precommercial thinning approach and thinning intensity. For selective precommercial thinning, working time varied between 42.8 and 63.9 h ha-1. For situational thinning at half-final distances, time consumption varied between 12 and 16.8 h ha-1, and for situational thinning at final distances, time consumption of varied between 4.5 and 5.7 h ha-1.
The resulting cost of tending young beech stands was between € 1052 and € 1572 for selective thinning, between € 296 and € 411 for situational thinning at half-final distances and between € 110 and € 140 per hectare for situational thinning at final distances. The influence of thinning intensity on labor costs, relative to the deviation from costs at normal thinning strength, decreased between thinning approaches (ST1800: ± 20%; ST400: ± 17%; ST100: ± 12% - Tab. S2 in Supplementary material).
# Discussion
The relatively high cost of selective precommercial thinning, which is widespread in Southeast and Central Europe has triggered the development of less expensive alternative approaches for precommercial silvicultural operations ([36], [18], [4]). Situational precommercial thinning has become a rational alternative to selective precommercial thinning in Switzerland’s young forests ([2], [3]), and a similar form has also developed in Germany ([32]). The primary reasons for this include the poor economic performance of selective thinning ([36]), concerns about collective stability ([4]) and the emergence of even-aged young stands following large-scale disturbances ([25]). Therefore, when compared to selective thinning, situational thinning maintains collective stand stability through the processes of biological automation and concentration of silvicultural interventions ([3], [40]).
Due to a lower number of crop trees per hectare, the use of situational thinning leads to more effective rationalization of productive time consumption compared to selective thinning. Situational thinning at half-final distances between crop trees and normal thinning intensity reduced productive time by 67%, and situational precommercial thinning at final distances reduced it by 90%. Stirnweiß ([39]) reported an absolute time consumption of between 3-5 hours per hectare, which is similar to the results of our simulation for situational thinning at final distances. Similar time consumption for selective precommercial thinning at half-final distances was also reported in previous field experiments in Slovenia ([6]).
The structure of simulated productive time significantly differed across the analyzed precommercial thinning approaches with the reduction of candidates/crop trees per hectare. The relationship between main and auxiliary productive time was inverted with a reduced number of candidates/crop trees per hectare. Comparing selective precommercial thinning to situational precommercial thinning at final distances, the share of main productive time decreased from 79% to 49%. Therefore, auxiliary productive time increased between thinning approaches, and in the case of precommercial thinning at final distances and normal intensity, it accounted for 51% of total time. In addition, heart rate readings in the auxiliary productive time compared to main productive time in motor-manual forest work were 10% lower during situational precommercial thinning ([15]). Therefore, due to the lower time consumption, fuel consumption ([3]), heart rate and exposure to external factors (e.g., wood dust - [24]), situational thinning also appears to be ergonomically better than selective precommercial thinning.
Main productive time significantly increased with thinning intensity due to the higher number of felled competitors. Therefore, the greater number of competitors per hectare resulting from high thinning intensity negatively affected the share of auxiliary productive time in the productive time structure. In the case of weak thinning intensity, the relationship was reversed. An increase in thinning intensity from moderate to weak or high resulted in a ± 20% (± 6.1 h ha-1), ± 16% (± 1.5 h ha-1) and ± 12% (± 0.4 h ha-1) change in the share of the productive time consumption for selective thinning, situational thinning at half-final distances and situational thinning at final distances, respectively. Due to the lack of research in the field of thinning intensity in young stands, such findings related to its influence on time consumption are vital for the fields of silviculture, ecology and wood quality. Experience and preliminary research suggest that frequent interventions across the entire stand area with selective thinning decrease collective stand stability, which is problematic in an era of increasing natural disturbance intensity and frequency ([4], [35], [40]). Collective stability has a particularly important role in young forest stands where there is a strong relationship between tree diameter and tree height ([4]). Early onset and high thinning intensities may also restrict natural self-pruning processes and thus negatively affect future wood quality ([34]). In this respect, situational precommercial thinning based on the principle of concentration is more appropriate for preserving collective stability and positively influences the quality of crop trees ([2], [4]).
The simulation of situational precommercial thinning at half-final distances suggested a 73 ± 4% reduction in costs, and at final distances, 90 ± 1% lower costs can be expected when compared to selective thinning (Tab. 1). Similar economic savings of situational thinning have been reported for Switzerland ([3]) and Germany ([39]). Situational precommercial thinning was also experimentally used in the thinning of young forests within secondary succession on abandoned agricultural lands where the treatment time consumption was similar to situational thinning at half-final distances in this study. Labor costs of the whole operation in a pole stand were € 336 ([11]), which is similar to our results considering lower stand densities on abandoned agricultural lands.
In forest operations the application of situational precommercial thinning is still rare due to its relatively short history and current experimental status. This slow progress may be attributed to: (i) the long-term use of selective thinning which has yielded beneficial results in past economic and climatic conditions; (ii) lack of knowledge on the development and social differentiation of natural stands; (iii) distrust of early final selection of crop trees, which may prevent subsequent corrections; and (iv) a lack of knowledge on the development of crop trees during the process of situational thinning ([39]). All of these represent important areas for future research work.
Although the computer simulation showed similar results to those obtained in previous studies on thinning of beech and mixed forests, the results reflect only an approximation of real forest operation work. The most important constructing factors within the simulation model are detailed work time and field studies from which the formulas used for calculating main and auxiliary productive time are constructed. The presented model is transferable to other terrain and species mixtures for which the biggest deficit is the lack of time studies. Therefore, for further validation of the model, it is important to provide additional time studies of thinning forest operations within young forest stands in contrasting situations (e.g., species mixtures, slope conditions, DBH).
Silvicultural treatment of young forests will be an important challenge for the forestry sector in the coming decades. In temperate forests worldwide, the incidence of large-scale natural disturbances such as windthrows and bark beetle outbreaks has significantly increased in the last decades ([37]). This resulted in large areas covered with young, mostly even-aged forest stands. Interesting new mixtures are emerging, with many options for light-demanding species, many of which are economically interesting. In order to maintain attractive mixtures, the crop tree quality, stand stability and growth potential of these forest areas will need to be properly tended ([23]). This emphasizes the need for an improved model for the implementation of young forest tending. Mechanized harvest is not feasible in stands following disturbances were intervention is infrequent due to low densities of crop trees. In addition, identification of tree species is required, which can be carried out by a well-trained forest worker. Such operations remain interesting in private forests, where owners carry out logging by themselves.
Looking ahead, it appears that the technological development of pre-commercial thinning will continue to advance. One possibility is the increased use of small harvesting machines ([9], [38]). However, experience from young successional stands suggests that heavy thinning can trigger a reduction in the collective stability of stands ([11]). In addition, mechanized harvesting leads to greater damage to the forest soil and - in the case of inexperienced machine operators - to the remaining stand ([10]). There are no such problems in the further optimization of moto-manual pre-commercial thinning approaches based on the principle of concertation (such as situational thinning). The third option is based on biological automation, e.g., the preference for small-scale, uneven-aged stands with continuous cover as the primary silvicultural approach ([4]). Such models, as presented above, enable the optimization and quick assessment of work costs and investments. Thus, further development with objective field evaluations could increase the importance of computer simulations and support decision-making process in young forest tending ([29]).
# Conclusions
Modelling time consumption for selective and situational precommercial thinning in mountain beech forest stands enables quantitative evaluation of the differences in time consumption (absolute and according to the time element structure) and thus a more accurate prediction of the resources required for alternative silvicultural approaches (material, costs, human work load). Quantifying differences in the resources required enables better planning, implementation and control of silvicultural treatments, which in the same cases is supported by society through fiscal policy measures (subsidies) to ensure sustainable forest management. The main findings are (i) that situational thinning approaches are less time consuming and significantly less expensive than selective thinning, and (ii) due to a larger share of auxiliary productive time (walking operation) and less chain-saw operation, situational thinning approaches also seem to be more ergonomically beneficial for silviculture workers.
# Acknowledgments
All the authors contributed equally to this manuscript. The first author kindly acknowledges the Pahernik Foundation for a scholarship during the second year of his master’s studies. This research was funded by the Pahernik Foundation.
# References
(1)
Albright CS (2001). VBA for modelers: developing decision support systems with Microsoft Excel. The Engineering Economist 46 (2): 162-163.
CrossRef | Gscholar
(2)
Ammann P (2005). Biologische Rationalisierung. Teil 3: Biologische Rationalisierung bei Esche, Bergahorn und Buche [Biological rationalization. Part 3: Biological rationalization for ash, sycamore maple and beech]. Wald und Holz 86 (3): 29-33. [in German]
Gscholar
(3)
Ammann P (2012). Jungwaldpflegekonzepte mit biologischer Rationalisierung [Tending concepts of young forests with biological rationalization]. Zürcher Wald 2: 12-15. [in German]
Gscholar
(4)
Ammann P (2013). Erfolg der Jungwaldpflege im Schweizer Mittelland? Analyse und Folgerungen (Essay) [Is young forest tending successful in the Swiss Plateau region? Analysis and implications]. Schweizerische Zeitschrift fur Forstwesen 164 (9): 262-270. [in German]
CrossRef | Gscholar
(5)
Arnič D (2016). Rationalisation of the first thinning in beech mountain forests on Menina. B.Sc. thesis, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia, pp. 48.
Gscholar
(6)
Arnič D, Krc J, Diaci J (2018). Primerjava izbiralnega redčenja in situacijskega redčenja v bukovih letvenjakih na Menini [Comparison of selective thinning and crop tree situational thinning in young beech stands on Menina]. Gozdarski vestnik 78 (2): 72-82. [in Slovenian]
Gscholar
(7)
Behjou FK, Majnounian B, Namiranian M, Saeed A, Feghhi J, Dvorak J (2009). Productivity and cost of manual felling with a chainsaw in Caspian forests. Journal of Forest Science 55 (2): 96-100.
CrossRef | Gscholar
(8)
Bergström D, Bergsten U, Nordfjell T, Lundmark T (2007). Simulation of geometric thinning systems and their time requirements for young forests. Silva Fennica 41 (1): 137-147.
Online | Gscholar
(9)
Bergström D, Bergsten U, Nordfjell T (2010). Comparison of boom-corridor thinning and thinning from below harvesting methods in young dense Scots pine stands. Silva Fennica 44 (4): 669-679.
Online | Gscholar
(10)
Cambi M, Certini G, Neri F, Marchi E (2015). The impact of heavy traffic on forest soils: a review. Forest Ecology and Management 338: 124-138.
CrossRef | Gscholar
(11)
Cojzer M, Diaci J, Brus R (2014). Tending of young forests in secondary succession on abandoned agricultural lands: an experimental study. Forests 5 (11): 2658-2678.
CrossRef | Gscholar
(12)
Di Salvatore U, Chiavetta U, Cantiani P, Fabbio G, Becagli C, Bertini G, Sansone D, Ferretti F, Tonti D, Bascietto M, Skudnik M, Ferreira A, Kobler A, Kovac M, Kobal M, Kutnar L (2016). ManFor C. Bd sites and the drivers of forest functions. Italian Journal of Agronomy 11 (1): 64-95.
Gscholar
(13)
Driels MR, Shin YS (2004). Determining the number of iterations for Monte Carlo simulations of weapon effectiveness. Naval Postgraduate School, Monterey, CA, USA, pp. 12.
Online | Gscholar
(14)
Ghaffariyan MR, Naghdi R, Ghajar I, Nikooy MJS (2013). Time prediction models and cost evaluation of cut-to-length (CTL) harvesting method in a mountainous forest. Small-scale Forestry 12 (2): 181-192.
CrossRef | Gscholar
(15)
Hagen KB, Vik T, Myhr NE, Opsahl PA, Harms-Ringdahl K (1993). Physical workload, perceived exertion, and output of cut wood as related to age in motor-manual cutting. Ergonomics 36 (5): 479-488.
CrossRef | Gscholar
(16)
Hofer P, Altweg J (2006). Lernen von erfolgreichen Forstbetrieben: Ergebnisse einer Untersuchung über die wirtschaftlichen Erfolgsfaktoren ausgewählter Forstbetriebe in der Schweiz [Learning from successful forest companies: results of a study on the economic success factors of selected forest companies in Switzerland]. Bundesamt für Umwelt, Bern, Switzerland, pp. 85. [in German]
Gscholar
(17)
Keenan RJ (2015). Climate change impacts and adaptation in forest management: a review. Annals of Forest Science 72 (2): 145-167.
CrossRef | Gscholar
(18)
Klädtke J, Abetz P (2010). Die Durchforstungshilfe [The thinning aid]. Merkblatt 53: 1-12. [in German]
Gscholar
(19)
Krajčič D, Kolar I (2000). Influence of modified way of pole stand tending on reduction of expenses. Gozdarski vestnik 58 (2): 75-84.
Gscholar
(20)
Ligné D, Eliasson L, Nordfjell T (2005). Time consumption and damage to the remaining stock in mechanised and motor manual pre-commercial thinning. Silva Fennica 39 (3): 455-464.
Online | Gscholar
(21)
Lombardi F, Lella SD, Altieri V, Benedetto SD, Giancola C, Lasserre B, Kutnar L, Tognetti R, Marchetti M (2018). Early responses of biodiversity indicators to various thinning treatments in mountain beech forests. iForest - Biogeosciences and Forestry 11 (5): 609-618.
CrossRef | Gscholar
(22)
Lortz D, Kluender R, McCoy W, Stokes B, Klepac J (1997). Manual felling time and productivity in southern pine forests. Forest Products Journal 47 (10): 59-63.
Online | Gscholar
(23)
Maleki K, Zeller L, Pretzsch H (2020). Oak often needs to be promoted in mixed beech-oak stands - the structural processes behind competition and silvicultural management in mixed stands of European beech and sessile oak. iForest - Biogeosciences and Forestry 13 (2): 80-88.
CrossRef | Gscholar
(24)
Marchi E, Neri F, Cambi M, Laschi A, Foderi C, Sciarra G, Fabiano F (2017). Analysis of dust exposure during chainsaw forest operations. iForest - Biogeosciences and Forestry 10 (1): 341-347.
CrossRef | Gscholar
(25)
Ninove C, Nikolova PS, Zell J, Bürgi A, Brang P (2015). Jungwaldpflegeverfahren auf der Lothar-Sturmfläche Diessenhofen TG [Young forest tending procedure on the Lothar-Windthrow area Diessenhofen TG]. Schlussbericht mit den Ergebnissen der bisherigen Inventuren, Eidg. Forschungsanstalt für Wald, WSL, Birmensdorf, Switzerlands, pp. 40. [in German]
Gscholar
(26)
Orešnik J (2009). Primerjava različnih načinov redčenj na raziskovalnih ploskvah v Lučki Beli [Comparison of different methods of thinning on research plots in Lučka Bela]: B. Sc. thesis, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia, pp. 42. [in Slovenian]
Gscholar
(27)
Palosuo T, Suominen T, Werhahn-Mees W, Garcia-Gonzalo J, Lindner M (2010). Assigning results of the Tool for Sustainability Impact Assessment (ToSIA) to products of a forest-wood-chain. Ecological Modelling 221 (18): 2215-2225.
CrossRef | Gscholar
(28)
Picchio R, Venanzi R, Latterini F, Marchi E, Laschi A, Lo Monaco A (2018). Corsican pine (Pinus laricio Poiret) stand management: medium and long lasting effects of thinning on biomass growth. Forests 9 (257): 1-17.
CrossRef | Gscholar
(29)
Picchio R, Proto AR, Civitarese V, Di Marzio N, Latterini F (2019). Recent contributions of some fields of the electronics in development of forest operations technologies. Electronics 8 (1465): 1-19.
CrossRef | Gscholar
(30)
Picchio R, Tavankar F, Latterini F, Jourgholami M, Karamdost Marian B, Venanzi R (2020). Influence of different thinning treatments on stand resistance to snow and wind in loblolly pine (Pinus taeda L.) coastal plantations of Northern Iran. Forests 11 (1034): 1-14.
CrossRef | Gscholar
(31)
Pretzsch H (2009). Forest dynamics, growth and yield: from measurement to model. Springer-Verlag Berlin Heidelberg, Berlin, Germany, pp. 664.
CrossRef | Gscholar
(32)
Rothkegel W, Ruppert O, Peter J (2016). Jungbestandspflege [Tending of young forests]. Merkblatt, Bayerischen Landesanstalt für Wald und Forstwirtschaft 29: 4. [in German]
Gscholar
(33)
Rozenbergar D, Ficko A, Diaci J (2008). Sodobno gojenje bukovih gozdov [Contemporary silviculture of beech forests]. Zbornik gozdarstva in lesarstva 87: 77-87. [in Slovenian]
Gscholar
(34)
Russo D, Marziliano P, Macri G, Proto A, Zimbalatti G, Lombardi F (2019). Does thinning intensity affect wood quality? An analysis of Calabrian pine in Southern Italy using a non-destructive acoustic method. Forests 10 (303): 1-16.
CrossRef | Gscholar
(35)
Saje R (2014). Analiza poškodovanosti gozdnih sestojev v gozdnogospodarski enoti Brezova reber s poudarkom na snegolomu leta 2012 [Damage analysis of forest stands in the Brezova reber forest management unit with a focus on 2012 snow damage]. MSc. Thesis, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia, pp. 83. [in Slovenian]
Gscholar
(36)
Schütz J-P (1999). Neue Waldbehandlungskonzepte in Zeiten der Mittelknappheit: Prinzipien einer biologisch rationellen und kostenbewussten Waldpflege [New silvicultural concepts in times of economic constraints]. Schweizerische Zeitschrift Fur Forstwesen 150: 451-459. [in German]
CrossRef | Gscholar
(37)
Seidl R, Thom D, Kautz M, Martin-Benito D, Peltoniemi M, Vacchiano G, Wild J, Ascoli D, Petr M, Honkaniemi J, Lexer MJ, Trotsiuk V, Mairota P, Svoboda M, Fabrika M, Nagel TA, Reyer CPO (2017). Forest disturbances under climate change. Nature Climate Change 7: 395-402.
CrossRef | Gscholar
(38)
Spinelli R, Magagnotti N, Nati C (2010). Benchmarking the impact of traditional small-scale logging systems used in Mediterranean forestry. Forest Ecology and Management 260 (11): 1997-2001.
CrossRef | Gscholar
(39)
Stirnweiß S (2012). Das neue Pflegekonzept im Praxistest [The new forest tending concept in a practical tests]. LWF 86: 19-22. [in German]
Gscholar
(40)
Yücesan Z, Ozçelik S, Oktan E (2015). Effects of thinning on stand structure and tree stability in an afforested oriental beech (Fagus orientalis Lipsky) stand in northeast Turkey. Journal of Forestry Research 26 (1): 123-129.
CrossRef | Gscholar
#### Authors’ Affiliation
(1)
Domen Arnič
Slovenian Forestry Institute, Department of Forest Technique and Economics, Večna pot 2, SI-1000 Ljubljana (Slovenia)
(2)
Janez Krč 0000-0001-6561-6373
Jurij Diaci 0000-0002-0991-5309
Department of Forestry and Renewable Forest Resources, Biotechnical Faculty, University of Ljubljana. Večna pot 83, Ljubljana 1000 (Slovenia)
#### Corresponding author
Domen Arnič
[email protected]
#### Citation
Arnič D, Krč J, Diaci J (2021). Modeling of time consumption for selective and situational precommercial thinning in mountain beech forest stands. iForest 14: 137-143. - doi: 10.3832/ifor3556-014
Andrea Cutini
#### Paper history
Accepted: Jan 16, 2021
First online: Mar 16, 2021
Publication Date: Apr 30, 2021
Publication Time: 1.97 months
© SISEF - The Italian Society of Silviculture and Forest Ecology 2021
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https://bigladdersoftware.com/epx/docs/8-4/input-output-reference/group-performance-curves.html
|
## Input Output Reference — EnergyPlus 8.4
### Input Output Reference
This group of objects primarily consists of polynomial curves that are used to characterize the performance of HVAC equipment. Several other non-polynomial curves are also included to characterize the performance of pumps and fans. All of the curves are input, stored, and evaluated entirely within the CurveManager module. The curves are usually derived from fits or regressions to data covering a limited range. Results for independent variable values outside this range are likely to be invalid, so curve input always contains a range of validity (maximum and minimum permitted values) for each independent variable and can optionally have limits on the curve ouput. No error or warning message is issued if an independent variable is outside the range. Instead, the curve manager uses the minimum value if an independent variable is less than the minimum, and the maximum if a variable exceeds the maximum. Similarly, no error or warning message is issued if the curve output is outside the range of the optional minimum and maximum curve output limits. Instead, the curve manager uses the minimum and maximum curve limits to cap the output of the performance curve.
Curve names must be unique across all curve types.
Input for the linear curve consists of a curve name, the two coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the linear curve is:
A user assigned unique name for an instance of a linear curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Distance
• Power
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Following is an example input:
Curve:Linear,
Curve-Linear, ! name
-1, ! Coefficient1 Constant
2, ! Coefficient2 x
0.0, ! min curve output
1.0; ! max curve output
The following is another example, as might be applied in the Fan:ComponentModel to characterize duct static pressure reset (using a constant duct static pressure set point of 248.84 Pa in this case):
Curve:Linear,
DiagnosticSPR, ! Curve Name f = C1 + C2\*x
248.84, ! Coefficient1 Constant [Pa]
0., ! Coefficent 2 Press/Flow [Pa-s/m3]
0., ! Minimum Value of x (Qfan) [m3/s]
100., ! Maximum Value of x (Qfan) [m3/s]
62.5, ! Minimum Curve Output [Pa]
248.84; ! Maximum Curve Output [Pa]
Input consists of the curve name, the five coefficients, and maximum and minimum values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is represented by this curve:
#### y = C1 + C2 * w + C3 * x + C4 * y + C5 * z[LINK]
A user assigned unique name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The coefficient (C2) in the equation.
The coefficient (C3) in the equation.
The coefficient (C4) in the equation.
The coefficient (C5) in the equation.
#### Field: Minimum Value of w[LINK]
The minimum allowable value of w. Values of w less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of w[LINK]
The maximum allowable value of w. Values of z greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of z greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of y[LINK]
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of y[LINK]
The maximum allowable value of y. Values of z greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of z[LINK]
The minimum allowable value of z. Values of z less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of z[LINK]
The maximum allowable value of z. Values of z greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for w[LINK]
This field is used to indicate the kind of units that may be associated with the w values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of w and Maximum Value of w. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
• VolumetricFlowPerPower
#### Field: Input Unit Type for x[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of x and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
• VolumetricFlowPerPower
#### Field: Input Unit Type for y[LINK]
This field is used to indicate the kind of units that may be associated with the y values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of y and Maximum Value of y. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
• VolumetricFlowPerPower
#### Field: Input Unit Type for z[LINK]
This field is used to indicate the kind of units that may be associated with the z values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of z and Maximum Value of z. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
• VolumetricFlowPerPower
Below are an example inputs for QuadLinear Curves.
CURVE:QUADLINEAR,
MinDsnWBCurveName, ! Curve Name
-3.3333, ! CoefficientC1
0.0, ! CoefficientC2
38.9, ! CoefficientC3
0., ! CoefficientC4
0., ! CoefficientC5
-30., ! Minimum Value of w
40., ! Maximum Value of w
0., ! Minimum Value of x
1., ! Maximum Value of x
10., ! Minimum Value of y
8., ! Maximum Value of y
1. E-8, ! Minimum Value of z
8. E-8, ! Maximum Value of z
0., ! Minimum Curve Output
38.; ! Maximum Curve Output
MinActWBCurveName, ! Curve Name
-8.3333, ! CoefficientC1
2.0, ! CoefficientC2
5.5556., ! CoefficientC3
-1.0, ! CoefficientC4
0., ! CoefficientC5
0., ! Minimum Value of w
38., ! Maximum Value of w
0., ! Minimum Value of x
1., ! Maximum Value of x
10., ! Minimum Value of y
38., ! Maximum Value of y
1. E-8, ! Minimum Value of z
8. E-8, ! Maximum Value of z
0., ! Minimum Curve Output
43.; ! Maximum Curve Output
OptCondEntCurveName, ! Curve Name
12.2711, ! CoefficientC1
0.80, ! CoefficientC2
6.6667, ! CoefficientC3
-0.266, ! CoefficientC4
-6193484., ! CoefficientC5
0., ! Minimum Value of w
38., ! Maximum Value of w
0., ! Minimum Value of x
1., ! Maximum Value of x
10., ! Minimum Value of y
38., ! Maximum Value of y
1. E-8, ! Minimum Value of z
8. E-8, ! Maximum Value of z
0., ! Minimum Curve Output
32.; ! Maximum Curve Output
Input for a quadratic curve consists of the curve name, the three coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the quadratic curve is:
A user assigned unique name for an instance of a quadratic curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Distance
• Power
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Following is an example input.
Curve:Quadratic,
WindACCBFFFF, ! name
-2.277, ! Coefficient1 Constant
5.2114, ! Coefficient2 x
-1.9344, ! Coefficient3 x\*\*2
0.0, ! Minimum Value of x
1.0; ! Maximum Value of x
Input for a cubic curve consists of the curve name, the 4 coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the cubic curve is:
A user assigned unique name for an instance of a cubic curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
The cubic coefficient (C4) in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Distance
• Power
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Following is an input example.
Curve:Cubic,
WindACEIRFPLF, ! name
.00000273404, ! Coefficient1 Constant
1.05259, ! Coefficient2 x
-.0552087, ! Coefficient3 x**2
.00262236, ! Coefficient4
0.0, ! min
1.1; ! max
Input for a Quartic (fourth order polynomial) curve consists of the curve name, the five coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the quartic curve is:
A user assigned unique name for an instance of a Quartic curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The quadratic coefficient (C3) in the equation.
The cubic coefficient (C4) in the equation.
The fourth-order coefficient (C5) in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Distance
• Power
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Following is an input example.
Curve:Quartic,
BGSeries60, !- y = -611.41x4 + 192.68x3 - 88.843x2 + 4.7634x + 5.5656
5.5656, !- Constant
4.7634, !- 1st coefficient
-88.843, !- 2nd coefficient
192.68, !- 3rd coefficient
-611.41, !- 4th coefficient
0.0, !- Min Phi Value
0.2412; !- Max Phi Value
The following is another example, as might be applied in the Fan:ComponentModel to characterize belt maximum efficiency (using a medium efficiency belt in this case):
Curve:Quartic,
BeltMaxEffMedium, ! Curve Name
-0.09504, ! CoefficientC1
0.03415, ! CoefficientC2
-0.008897, ! CoefficientC3
0.001159, ! CoefficientC4
-0.00006132, ! CoefficientC5
-1.2, ! Minimum Value of x
6.2, ! Maximum Value of x
-4.6, ! Minimum Curve Output
0.; ! Maximum Curve Output
Input for a exponent curve consists of the curve name, the 3 coefficients, and the maximum and minimum valid independent variable values. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the exponent curve is:
A user assigned unique name for an instance of an exponent curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The linear coefficient (C2) in the equation.
The exponent coefficient (C3) in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Distance
• Power
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Following is an input example.
Curve:Exponent,
! Curve = C1 + C2\*x\*\*C3, x = fan speed ratio
FanPowerExponentCurve, !- Name
0.0, !- Coefficient1 Constant
1.0, !- Coefficient2 Constant
3.0, !- Coefficient3 Constant
0.0, !- Minimum Value of x
1.5, !- Maximum Value of x
0.1, !- Minimum Curve Output
1.5; !- Maximum Curve Output
This curve type is a function of two independent variables. Input consists of the curve name, the ten coefficients, and the minimum and maximum values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the bicubic curve is:
A user assigned unique name for an instance of a bicubic curve. When a curve is used by another object, it is referenced by this name.
The constant coefficient (C1) in the equation.
The coefficient C2 in the equation.
The coefficient C3 in the equation.
The coefficient C4 in the equation.
The coefficient C5 in the equation.
The coefficient C6 in the equation.
The coefficient C7 in the equation.
The coefficient C8 in the equation.
The coefficient C9 in the equation.
The coefficient C10 in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than this minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than this maximum will be replaced by the maximum.
#### Field: Minimum Value of y[LINK]
The minimum allowable value of y. Values of y less than this minimum will be replaced by the minimum.
#### Field: Maximum Value of y[LINK]
The maximum allowable value of y. Values of y greater than this maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
#### Field: Input Unit Type for Y[LINK]
This field is used to indicate the kind of units that may be associated with the y values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of Y and Maximum Value of Y. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Below is an example input.
Curve:Bicubic,
Main Chiller EIRFPLR, !- Name
7.086284E-02, !- Coefficient1 Constant
2.787561E-03, !- Coefficient2 x
-8.917038E-06, !- Coefficient3 x\*\*2
2.309734E-01, !- Coefficient4 y
1.250442E+00, !- Coefficient5 y\*\*2
-2.161029E-03, !- Coefficient6 x\*y
0.000000E+00, !- Coefficient7 x\*\*3
-5.630094E-01, !- Coefficient8 y\*\*3
0.000000E+00, !- Coefficient9 x\*\*2\*y
0.000000E+00, !- Coefficient10 x\*y\*\*2
20.33, !- Minimum Value of x
35.00, !- Maximum Value of x
0.25, !- Minimum Value of y
1.01; !- Maximum Value of y
This curve is a function of two independent variables. Input consists of the curve name, the six coefficients, and min and max values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the bicubic curve is:
A user assigned unique name for an instance of a biquadratic curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The coefficient C2 in the equation.
The coefficient C3 in the equation.
The coefficient C4 in the equation.
The coefficient C5 in the equation.
The coefficient C6 in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of y[LINK]
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of y[LINK]
The maximum allowable value of y. Values of y greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
#### Field: Input Unit Type for Y[LINK]
This field is used to indicate the kind of units that may be associated with the y values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of Y and Maximum Value of Y. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Below is an example input.
Curve:Biquadratic,
WindACCoolCapFT, ! name
0.942587793, ! Coefficient1 Constant
0.009543347, ! Coefficient2 x
0.000683770, ! Coefficient3 x\*\*2
-0.011042676, ! Coefficient4 y
0.000005249, ! Coefficient5 y\*\*2
-0.000009720, ! Coefficient6 x\*y
15., 22., ! min and max of first independent variable
29., 47.; ! min and max of second independent variable
This curve is a function of two independent variables. Input consists of the curve name, the six coefficients, and min and max values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the cubic linear curve:
A user assigned unique name for an instance of a quadratic-linear curve. When a curve is used, it is referenced by this name.
The constant coefficient ( ) in the equation.
The coefficient in the equation.
#### Field: Coefficient4 x**3 The coefficient C4 in the equation.[LINK]
The coefficient in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of y[LINK]
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of y[LINK]
The maximum allowable value of y. Values of y greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. The only option at this time is Dimensionless.
#### Field: Input Unit Type for Y[LINK]
This field is used to indicate the kind of units that may be associated with the x values. The only option at this time is Dimensionless.
This field is used to indicate the kind of units that may be associated with the output values. The only option at this time is Dimensionless.
An example input for the CubicLinear equation form is shown below.
Curve:CubicLinear,
InsideMeltIceDischarging, !- Name
0.108734675, !- Coefficient1 Constant
-0.989874286, !- Coefficient2 x
0.696303562, !- Coefficient3 x**2
-0.134945307, !- Coefficient4 x**3
1.724007415, !- Coefficient5 y
-1.094020457, !- Coefficient6 y*x
0.25, !- Minimum Value of x
1, !- Maximum Value of x
0.69, !- Minimum Value of y
1.26, !- Maximum Value of y
0.0926, !- Minimum Curve Output
0.4938, !- Maximum Curve Output
Dimensionless, !- Input Unit Type for X
Dimensionless, !- Input Unit Type for Y
Dimensionless, !- Output Unit Type
A custom chiller part-load performance curve is a function of three independent variables, i.e., x, y, and z. Input consists of the curve name, the twelve coefficients, and min and max values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve.
The equation represented by the custom curve is:
where,
• x represents the normalized fractional lift (the delta of temperature across the leaving condenser water temperature and leaving evaporator water temperature of a chiller).
• y represents the normalized deviation of leaving chilled water temperature from the reference condition.
• z represents the part load ratio.
A user assigned unique name for an instance of a biquadratic curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The coefficient C2 in the equation.
The coefficient C3 in the equation.
The coefficient C4 in the equation.
The coefficient C5 in the equation.
The coefficient C6 in the equation.
The constant coefficient (C7) in the equation.
The coefficient C8 in the equation.
The coefficient C9 in the equation.
The coefficient C10 in the equation.
The coefficient C11 in the equation.
The coefficient C12 in the equation.
### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
### Field: Minimum Value of y[LINK]
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
### Field: Maximum Value of y[LINK]
The maximum allowable value of y. Values of y greater than the maximum will be replaced by the maximum.
### Field: Minimum Value of z[LINK]
The minimum allowable value of z. Values of y less than the minimum will be replaced by the minimum.
### Field: Maximum Value of z[LINK]
The maximum allowable value of z. Values of y greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
### Field: Input Unit Type for x[LINK]
This field is used to indicate the kind of units that may be associated with the x values. Select Dimensionless.
### Field: Input Unit Type for y[LINK]
This field is used to indicate the kind of units that may be associated with the y values. Select Dimensionless.
### Field: Input Unit Type for z[LINK]
This field is used to indicate the kind of units that may be associated with the y values. Select Dimensionless.
This field is used to indicate the kind of units that may be associated with the output values. Select Dimensionless.
Below is an example input:
Curve:ChillerPartLoadCustom,
EIRFPLR, !- Name
0.093291598, !- Coefficient1 Constant
-0.234322952, !- Coefficient2 x
0.426950368, !- Coefficient3 x**2
0.188624721, !- Coefficient4 y
-0.608010978, !- Coefficient5 y**2
0.992031248, !- Coefficient6 x*y
0.000000E+00, !- Coefficient7 x**3
0.502338322, !- Coefficient8 y**3
0.000000E+00, !- Coefficient9 x**2*y
0.000000E+00, !- Coefficient 10 x*y**2
-0.360902326, !- Coefficient 11 x**2*y**2
-0.097978985, !- Coefficient 12 z*y**3
0.2562, !- Minimum Value of x
1.0365, !- Maximum Value of x
0.1, !- Minimum Value of y
1, !- Maximum Value of y
-0.035, !- Minimum Value of z
0.3144, !- Maximum Value of z
, !- Minimum Curve Output
, !- Maximum Curve Output
Dimensionless, !- Input Unit Type for x
Dimensionless, !- Input Unit Type for y
Dimensionless, !- Input Unit Type for z
Dimensionless; !- Output Unit Type
This curve is a function of two independent variables. Input consists of the curve name, the six coefficients, and min and max values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the quadratic linear curve:
A user assigned unique name for an instance of a quadratic-linear curve. When a curve is used, it is referenced by this name.
The constant coefficient (C1) in the equation.
The coefficient C2 in the equation.
The coefficient C3 in the equation.
The coefficient C4 in the equation.
The coefficient C5 in the equation.
The coefficient C6 in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of y[LINK]
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of y[LINK]
The maximum allowable value of y. Values of y greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
#### Field: Input Unit Type for Y[LINK]
This field is used to indicate the kind of units that may be associated with the y values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of Y and Maximum Value of Y. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Below is an example input.
Curve:QuadraticLinear,
DischargeCurve, !- Curve Name
0.0, !- Coefficient1 Constant
0.09, !- Coefficient2 x
-0.15, !- Coefficient3 x\*\*2
0.612, !- Coefficient4 y
-0.324, !- Coefficient5 x\*y
-0.216, !-Coefficient6 x\*\*2\*y
0.0, !- Minimum Value of x
1.0, !- Maximum Value of x
0.0, !- Minimum Value of y
9.9; !- Maximum Value of y
This curve is a 2nd order polynomial function of three variable polynomial independent variables. Input consists of the curve name, the twenty seven coefficients, and min and max values for each of the independent variables. Optional inputs for curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation represented by the triquadratic curve:
The constant coefficient (A0) in the equation.
The coefficient (A1) in the equation.
The coefficient (A2) in the equation.
The coefficient (A3) in the equation.
The coefficient (A4) in the equation.
The coefficient (A5) in the equation.
The coefficient (A6) in the equation.
The coefficient (A7) in the equation.
The coefficient (A8) in the equation.
The coefficient (A9) in the equation.
The coefficient (A10) in the equation.
The coefficient (A11) in the equation.
The coefficient (A12) in the equation.
The coefficient (A13) in the equation.
The coefficient (A14) in the equation.
The coefficient (A15) in the equation.
The coefficient (A16) in the equation.
The coefficient (A17) in the equation.
The coefficient (A18) in the equation.
The coefficient (A19) in the equation.
The coefficient (A20) in the equation.
The coefficient (A21) in the equation.
The coefficient (A22) in the equation.
The coefficient (A23) in the equation.
The coefficient (A24) in the equation.
The coefficient (A25) in the equation.
The coefficient (A26) in the equation.
#### Field: Minimum Value of x[LINK]
The minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of y[LINK]
The minimum allowable value of y. Values of y less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of y[LINK]
The maximum allowable value of y. Values of y greater than the maximum will be replaced by the maximum.
#### Field: Minimum Value of z[LINK]
The minimum allowable value of z. Values of z less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of z[LINK]
The maximum allowable value of z. Values of z greater than the maximum will be replaced by the maximum.
The minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for X[LINK]
This field is used to indicate the kind of units that may be associated with the x values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of X and Maximum Value of x. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
#### Field: Input Unit Type for Y[LINK]
This field is used to indicate the kind of units that may be associated with the y values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of Y and Maximum Value of Y. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
#### Field: Input Unit Type for Z[LINK]
This field is used to indicate the kind of units that may be associated with the z values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Value of Z and Maximum Value of Z. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Temperature
• VolumetricFlow
• MassFlow
• Power
• Distance
This field is used to indicate the kind of units that may be associated with the output values. It is used by IDF Editor to display the appropriate SI and IP units for the Minimum Curve Output and Maximum Curve Output. The unit conversion is not applied to the coefficients. The available options are shown below. If none of these options are appropriate, select Dimensionless which will have no unit conversion.
• Dimensionless
• Capacity
• Power
Input for a pressure drop curve consists of the curve name, a varying number of parameters, and the maximum and minimum valid independent variable values. The equation represented by the pressure drop curve is:
A user assigned unique name for an instance of a pressure drop curve. When a curve is used, it is referenced by this name.
This diameter represents an equivalent diameter for the given branch. This is parameter (D) in the equation, and has units of {m}. Since varying components may be found on the same branch, this value must be selected along with the other inputs in order to provide a proper value of pressure drop. This is used to calculate the velocity in addition to being used directly in the frictional pressure drop calculation.
This is the pressure drop coefficient typically applied to components such as fittings and occasionally heat pumps. This is parameter (K) in the equation and is dimensionless. This coefficient is used to describe the amount of dynamic pressure lost during the process. This value may be left blank if the user only wants to account for frictional losses in this branch.
This is the length of a pressure drop process in which friction is applied. This is parameter (L) in the equation and has units of {m}. In a pipe, this would be the length of the pipe, however in many cases, pressure drop in other components are applied as an equivalent length. This is only required if the user is wanting to perform frictional pressure drop calculations.
This field represents the first method to simulate frictional losses. This parameter does not appear directly in the equation above, as it is only used to develop the friction factor (f), but the roughness will have units of {m} if entered. If the user enters this roughness value, the pressure system will use it along with an approximation to the Moody chart to estimate the friction factor given the current flow conditions. This allows the friction calculate to be dynamic throughout the simulation.
This field represents the second method to simulate frictional losses. This is parameter (f) in the equation and is dimensionless. This parameter is a fixed value of friction factor which would override any calculations performed based on roughness, etc. If the user has a known friction factor for a given component, this is where it should be entered.
In the curve outputs for this object:
• Curve Input 1: MassFlow
• Curve Input 2: Density
• Curve Input 3: Velocity
• Curve Output: the resultant value
Following is an input example.
Curve:Functional:PressureDrop,
PressureMinorAndFriction,!- Name
0.05, !- Diameter
53.8, !- Minor Loss Coefficient
200, !- Length
, !- Roughness
0.008; !- Fixed Friction Factor
Input for the fan total pressure rise curve consists of the curve name, the four coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is:
where is the fan total pressure rise (Pa) as a function of volumetric flow through the fan ( ), duct static pressure set point ( , Pa), and static pressure surrounding the ducts ( , Pa). is assumed to be zero.
The first term of the curve looks like the common system curve in which the fan pressure rise is proportional to the square of the fan flow, but here it also depends implicitly on supply and return pressure losses, and in part on the fraction of the fan flow that is outdoor air (essentially “leaks” into and out of the return side of the system). Very often it is the only term considered, but that would only be correct with fixed-position dampers, no distribution system leakage, no linear resistance components, and no duct static pressure control.
The second term accounts for significant flow resistances in the system where the pressure difference is linearly proportional to the flow. Some filters and coils in the return may need this term to be adequately described. This term could be ignored if there are no linear components or if their pressure drops are very small compared to the other terms.
The third term, which depends on the fan flow and square root of the supply duct pressure Psm, accounts in part for leakage from the supply system when damper positions are fixed or are changed independently of static pressure or fan flow. In this case, reducing or eliminating supply leakage results in a different system curve. This, however, might be only a minor correction to the simple system curves generally used. The third term is zero when the VAV box dampers are modulated to control flow. Consequently, with variable-position supply dampers, reducing or eliminating supply leakage does not change the system curve.
The last term also accounts in part for leakage from the supply system when damper positions are fixed or are changed independently of static pressure or fan flow. This term indicates that the same fan pressure rise can be achieved by raising the duct pressure and closing dampers. The only change in the system in such a case is that the leakage flow may increase. The coefficient for this term is one when the VAV box dampers are modulated to control flow. In both cases, this term may be the most important correction to the simple system curves generally used, especially at low flows.
The required user-assigned unique alpha name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
#### Field: Fan Pressure Rise Coefficient1 C1[LINK]
The required numeric constant coefficient C1 (Pa s2/m6) in the curve. Must be greater than zero.
#### Field: Fan Pressure Rise Coefficient2 C2[LINK]
The required numeric constant coefficient C2 (Pa s/m3) in the curve.
#### Field: Fan Pressure Rise Coefficient3 C3[LINK]
The required numeric constant coefficient C3 (Pa0.5 s/m3) in the curve.
#### Field: Fan Pressure Rise Coefficient4 C4[LINK]
The required numeric constant coefficient C4 (dimensionless) in the curve.
#### Field: Minimum Value of Qfan[LINK]
The required numeric minimum allowable value of Qfan (m3/s). Values of Qfan less than the minimum will be replaced within this curve by the minimum.
#### Field: Maximum Value of Qfan[LINK]
The required numeric maximum allowable value of Qfan (m3/s). Values of Qfan greater than the maximum will be replaced within this curve by the maximum.
#### Field: Minimum Value of Psm[LINK]
The required numeric minimum allowable value of Psm (Pa). Values of Psm less than the minimum will be replaced within this curve by the minimum.
#### Field: Maximum Value of Psm[LINK]
The required numeric maximum allowable value of Psm (Pa). Values of Psm greater than the maximum will be replaced within this curve by the maximum.
The optional numeric minimum allowable value of the evaluated curve (Pa). Values less than the minimum will be replaced within this curve by the minimum.
The optional numeric maximum allowable value of the evaluated curve (Pa). Values greater than the maximum will be replaced within this curve by the maximum.
The following is an input example describing the fan total pressure rise for a VAV system with a constant non-zero duct static pressure set point (the set point is described separately; see the Curve:Linear object for a related example):
Curve:FanPressureRise,
VSD Example, ! Curve Name f = C1*Qfan**2+C2*Qfan+C3*Qfan*(Psm-Po)**0.5+C4*(Psm-Po) with Po = 0
1446.75833497653, ! CoefficientC1 Alpha [Pa s2/m6]
0., ! CoefficientC2 Beta [Pa s/m3]
0., ! CoefficientC3 Gamma [Pa0.5 s/m3]
1., ! CoefficientC4 Delta [-]
0., ! Minimum Value of Qfan [m3/s]
100., ! Maximum Value of Qfan [m3/s]
62.5, ! Minimum Value of Psm [Pa]
300., ! Maximum Value of Psm [Pa]
0.; ! Minimum Curve Output [Pa]
5000.; ! Maximum Curve Output [Pa]
Input for the exponential-modified skew normal curve consists of the curve name, the four coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is:
where Z1 = (x C1) / C2; Z2 = [(exp(C3*x) * C4*x) - C1] / C2; Z3 = -C1 / C2
The required user-assigned unique alpha name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
The required numeric constant coefficient C1 in the curve.
The required numeric constant coefficient C2 in the curve. Must be non-zero.
The required numeric constant coefficient C3 in the curve.
The required numeric constant coefficient C4 in the curve.
#### Field: Minimum Value of x[LINK]
The required numeric minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for x[LINK]
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Value of x and Maximum Value of x (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Curve Output and Maximum Curve Output (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
The following are input examples describing the normalized fan efficiency for the normal (non-stall) and stall operating regions of a backward-curved airfoil centrifugal fan:
Curve:ExponentialSkewNormal,
FanEff120CPLANormal, ! Curve Name
0.072613, ! CoefficientC1 Afan
0.833213, ! CoefficientC2 Bfan
0., ! CoefficientC3 Cfan
0.013911, ! CoefficientC4 Dfan
-4., ! Minimum Value of x
5., ! Maximum Value of x
0.1, ! Minimum Curve Output
1.; ! Maximum Curve Output
Curve:ExponentialSkewNormal,
FanEff120CPLAStall, ! Curve Name
-1.674931, ! CoefficientC1 Afan
1.980182, ! CoefficientC2 Bfan
0., ! CoefficientC3 Cfan
1.844950, ! CoefficientC4 Dfan
-4., ! Minimum Value of x
5., ! Maximum Value of x
0.1, ! Minimum Curve Output
1.; ! Maximum Curve Output
Input for the sigmoid curve consists of the curve name, the five coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is:
The required user-assigned unique alpha name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
The required numeric constant coefficient C1 in the equation.
The required numeric constant coefficient C2 in the equation.
The required numeric constant coefficient C3 in the equation.
The required numeric constant coefficient C4 in the equation.
The required numeric constant coefficient C5 in the equation.
#### Field: Minimum Value of x[LINK]
The required numeric minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for x[LINK]
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Value of x and Maximum Value of x (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Curve Output and Maximum Curve Output (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
The following are input examples describing the normalized dimensionless flow for normal (non-stall) and stall operating regions of a backward-curved airfoil centrifugal fan:
Curve:Sigmoid,
FanDimFlowNormal, ! Curve Name
0., ! CoefficientC1 Aspd
1.001423, ! CoefficientC2 Bspd
0.123935, ! CoefficientC3 Cspd
-0.476026, ! CoefficientC4 Dspd
1., ! CoefficientC5 Espd
-4., ! Minimum Value of x
5., ! Maximum Value of x
0.05, ! Minimum Curve Output
1.; ! Maximum Curve Output
Curve:Sigmoid,
FanDimFlowStall, ! Curve Name
0., ! CoefficientC1 Aspd
5.924993, ! CoefficientC2 Bspd
-1.91636, ! CoefficientC3 Cspd
-0.851779, ! CoefficientC4 Dspd
1., ! CoefficientC5 Espd
-4., ! Minimum Value of x
5., ! Maximum Value of x
0.05, ! Minimum Curve Output
1.; ! Maximum Curve Output
Input for the single rectangular hyperbola type 1 curve consists of the curve name, the three coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is:
y =(C1 -* x) / (C2+x) + C3
The required user-assigned unique alpha name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
The required numeric constant coefficient C1 in the equation.
The required numeric constant coefficient C2 in the equation.
The required numeric constant coefficient C3 in the equation.
#### Field: Minimum Value of x[LINK]
The required numeric minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for x[LINK]
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Value of x and Maximum Value of x (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Curve Output and Maximum Curve Output (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
The following is an input example describing the maximum efficiency variation for a mid- or average-efficiency type of motor:
Curve:RectangularHyperbola1,
MotorMaxEffAvg, ! Curve Name
0.29228, ! CoefficientC1
3.368739, ! CoefficientC2
0.762471, ! CoefficientC3
0., ! Minimum Value of x
7.6, ! Maximum Value of x
0.01, ! Minimum Curve Output
1.; ! Maximum Curve Output
Input for the single rectangular hyperbola type 2 curve consists of the curve name, the three coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is:
y =(C1 -* x) / (C2+x) + C3 -* x
The required user-assigned unique alpha name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
The required numeric constant coefficient C1 in the equation.
The required numeric constant coefficient C2 in the equation.
The required numeric constant coefficient C3 in the equation.
#### Field: Minimum Value of x[LINK]
The required numeric minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for x[LINK]
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Value of x and Maximum Value of x (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Curve Output and Maximum Curve Output (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
The following are input examples describing part-load efficiency variations for a medium efficiency type of V-belt (Regions 1 and 3), for a mid- or average-efficiency nominal 25 hp 4-pole motor, and a nominal 30 hp VFD:
Curve:RectangularHyperbola2,
0.920797, ! CoefficientC1
0.0262686, ! CoefficientC2
0.151594, ! CoefficientC3
0., ! Minimum Value of x
1., ! Maximum Value of x
0.01, ! Minimum Curve Output
1.; ! Maximum Curve Output
Curve:RectangularHyperbola2,
1.037778, ! CoefficientC1
0.0103068, ! CoefficientC2
-0.0268146, ! CoefficientC3
0., ! Minimum Value of x
1., ! Maximum Value of x
0.01, ! Minimum Curve Output
1.; ! Maximum Curve Output
Curve:RectangularHyperbola2,
1.137209, ! CoefficientC1
0.0502359, ! CoefficientC2
-0.0891503, ! CoefficientC3
0., ! Minimum Value of x
1., ! Maximum Value of x
0.01, ! Minimum Curve Output
1.; ! Maximum Curve Output
Curve:RectangularHyperbola2,
0.987405, ! CoefficientC1
0.0155361, ! CoefficientC2
-0.0059365, ! CoefficientC3
0., ! Minimum Value of x
1., ! Maximum Value of x
0.01, ! Minimum Curve Output
1.; ! Maximum Curve Output
Input for the exponential decay curve consists of the curve name, the three coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve minimum and maximum may be used to limit the output of the performance curve (e.g., limit extrapolation). The equation is:
y = C1 + C2 * exp(C3\ *x)
The required user-assigned unique alpha name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
The required numeric constant coefficient C1 in the equation.
The required numeric constant coefficient C2 in the equation.
The required numeric constant coefficient C3 in the equation.
#### Field: Minimum Value of x[LINK]
The required numeric minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum.
#### Field: Maximum Value of x[LINK]
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum.
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum.
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum.
#### Field: Input Unit Type for x[LINK]
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Value of x and Maximum Value of x (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
This optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum Curve Output and Maximum Curve Output (currently dimensionless). At this time, only the Dimensionless option is provided so that no unit conversion is used for this curve.
The following is an input example describing the part-load efficiency variation for a medium efficiency type of V-belt (Region 2):
Curve:ExponentialDecay,
1.011965, ! CoefficientC1
-0.339038, ! CoefficientC2
-3.43626, ! CoefficientC3
0., ! Minimum Value of x
1., ! Maximum Value of x
0.01, ! Minimum Curve Output
1.; ! Maximum Curve Output
Input for the double exponential decay curve consists of the curve name, the five coefficients, and the maximum and minimum valid independent variable values. Optional inputs for the curve include the minimum and maximum output of the performance curve. The equation is:
This field indicates the required user-assigned name for an instance of this curve. When a curve of this type is used, it is referenced by this name.
The required numeric constant coefficient C1 in the equation.
The required numeric constant coefficient C2 in the equation.
The required numeric constant coefficient C3 in the equation.
The required numeric constant coefficient C4 in the equation.
The required numeric constant coefficient C5 in the equation.
#### Field: Minimum Value of x[LINK]
The required numeric minimum allowable value of x. Values of x less than the minimum will be replaced by the minimum
#### Field: Maximum Value of x[LINK]
The required numeric maximum allowable value of x. Values of x greater than the maximum will be replaced by the maximum
The optional numeric minimum allowable value of the evaluated curve. Values less than the minimum will be replaced by the minimum
The optional numeric maximum allowable value of the evaluated curve. Values greater than the maximum will be replaced by the maximum
#### Field: Input Unit Type for x[LINK]
The optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum and Maximum Value of x. Currently, only Dimensionless option is provided so that no unit conversion is used for this curve
The optional field is provided for future purposes so that the IDF Editor could display the appropriate SI or IP units for the Minimum and Maximum Curve Ouput. Currently, only Dimensionless option is provided so that no unit conversion is used for this curve.
An example input of the Curve:DoubleExponentialDecay input is:
Curve:DoubleExponentialDecay,
BatteryCycleCurve, !- Name
1380, !- Coefficient1 C1
6834, !- Coefficient2 C2
-8.75, !- Coefficient3 C3
6747, !- Coefficient4 C4
-6.22, !- Coefficient5 C5
0, !- Minimum Value of x
1.0; !- Maximum Value of x
The current value of the performance curve. This value is averaged over the time step being reported. Inactive or unused performance curves will show a value of -999 (e.g., equipment is off, a specific performance curve is not required for this aspect of the equipment model at this time step, etc.). This value means that the performance curve was not called during the simulation and, therefore, not evaluated. This inactive state value is only set at the beginning of each environment. When averaging over long periods of time, this inactive state value may skew results. In this case, use a detaled reporting frequency (ref. Output:Variable object) to view results at each HVAC time step.
#### Performance Curve Input Variable 1(-N) Value[LINK]
The current value of the nth independent variable passed to the performance curve. The order of the independent variables is in the same order as the model equation represented by this performance curve object. This value is averaged over the time step being reported.
HVAC,Average,Performance Curve Output Value
HVAC,Average,Performance Curve Input Variable 1 Value
HVAC,Average,Performance Curve Input Variable 2 Value
HVAC,Average,Performance Curve Input Variable 3 Value
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|
https://link.springer.com/chapter/10.1007/978-3-642-27323-0_18
|
# Additivity of Lie Triple Isomorphisms on Standard Operator Subalgebras of Nest Algebras
• Hua Jiang
• Peisheng Ji
• Xiaolu Sun
Conference paper
Part of the Lecture Notes in Electrical Engineering book series (LNEE, volume 143)
## Abstract
Let A be a standard operator subalgebra of nest algebra which does not contain the identity operator, acting on a Hilbert space of dimension greater than one. If φ is a bijective Lie triple map from A onto an arbitrary algebra, that is $$\phi(\big{[{[a,b]},c\big]})$$=$$\big{[[\phi(a),\phi(b)],\phi(c)\big]}$$,for all a,b,cA,then φ is additive.
## Keywords
Lie triple isomorphism Additivity standard operator subalgebra of nest algebra
## References
1. 1.
Davision, K.R.: Nest Algebras: Pitman Research Notes in Mathematics Series, vol. 191. Longman Scientific and Technical, Burnt mill harlow, Essex, UK (1988)Google Scholar
2. 2.
Jacobson, N., Rickart, C.E.: Jordan homomorphisms rings. Tran. Amer. Math. Soc. 69, 479–502 (1950)
3. 3.
Ji, P., Wang, L.: Lie triple derivations of TUHF algebras. Linear Algebra Appl. 403, 399–408 (2005)
4. 4.
Ji, P., Jiang, H.: Nonlinear Lie triple derivations on von Neumann algebras (submitted)Google Scholar
5. 5.
Lu, F.: Lie triple derivations of nest algebras. Math. Nachr. 280, 882–887 (2007)
6. 6.
Miers, C.R.: Lie *-triple homomorphisms into von Neumann algebras. Proc. Amer. Math. Soc. 58, 169–172 (1976)
7. 7.
Miers, C.R.: Lie triple derivations of VN algebras. Proc. Amer. Math. Soc. 71, 57–61 (1978)
8. 8.
Wang, H.T., Li, Q.G.: Lie triple derivation of the Lie algebra of strictly upper triangular matrix over a commutative ring. Linear Algebra Appl. 430, 66–77 (2009)
9. 9.
Zhang, J.H., Wu, B.W., Cao, H.X.: Lie triple derivations of nest algebras. Linear Algebra Appl. 416, 559–567 (2006)
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https://www.clim-past.net/15/1463/2019/
|
Journal cover Journal topic
Climate of the Past An interactive open-access journal of the European Geosciences Union
Journal topic
Clim. Past, 15, 1463–1483, 2019
https://doi.org/10.5194/cp-15-1463-2019
Clim. Past, 15, 1463–1483, 2019
https://doi.org/10.5194/cp-15-1463-2019
Research article 05 Aug 2019
Research article | 05 Aug 2019
Simulating the climate response to atmospheric oxygen variability in the Phanerozoic: a focus on the Holocene, Cretaceous and Permian
Simulating the climate response to atmospheric oxygen variability in the Phanerozoic: a focus on the Holocene, Cretaceous and Permian
David C. Wade1, Nathan Luke Abraham1,2, Alexander Farnsworth3, Paul J. Valdes3, Fran Bragg3, and Alexander T. Archibald1,2 David C. Wade et al.
• 1Department of Chemistry, Centre for Atmospheric Science, Cambridge, UK
• 2Department of Chemistry, National Centre for Atmospheric Science, Cambridge, UK
• 3School of Geographical Sciences, University of Bristol, Bristol, UK
Abstract
The amount of dioxygen (O2) in the atmosphere may have varied from as little as 5 % to as much as 35 % during the Phanerozoic eon (54 Ma–present). These changes in the amount of O2 are large enough to have led to changes in atmospheric mass, which may alter the radiative budget of the atmosphere, leading to this mechanism being invoked to explain discrepancies between climate model simulations and proxy reconstructions of past climates. Here, we present the first fully 3-D numerical model simulations to investigate the climate impacts of changes in O2 under different climate states using the coupled atmosphere–ocean Hadley Centre Global Environmental Model version 3 (HadGEM3-AO) and Hadley Centre Coupled Model version 3 (HadCM3-BL) models. We show that simulations with an increase in O2 content result in increased global-mean surface air temperature under conditions of a pre-industrial Holocene climate state, in agreement with idealised 1-D and 2-D modelling studies. We demonstrate the mechanism behind the warming is complex and involves a trade-off between a number of factors. Increasing atmospheric O2 leads to a reduction in incident shortwave radiation at the Earth's surface due to Rayleigh scattering, a cooling effect. However, there is a competing warming effect due to an increase in the pressure broadening of greenhouse gas absorption lines and dynamical feedbacks, which alter the meridional heat transport of the ocean, warming polar regions and cooling tropical regions.
Case studies from past climates are investigated using HadCM3-BL and show that, in the warmest climate states in the Maastrichtian (72.1–66.0 Ma), increasing oxygen may lead to a temperature decrease, as the equilibrium climate sensitivity is lower. For the Asselian (298.9–295.0 Ma), increasing oxygen content leads to a warmer global-mean surface temperature and reduced carbon storage on land, suggesting that high oxygen content may have been a contributing factor in preventing a “Snowball Earth” during this period of the early Permian. These climate model simulations reconcile the surface temperature response to oxygen content changes across the hierarchy of model complexity and highlight the broad range of Earth system feedbacks that need to be accounted for when considering the climate response to changes in atmospheric oxygen content.
1 Introduction
The primary driver of climate over the Phanerozoic is atmospheric CO2 . However, atmospheric oxygen content may also have varied across the Phanerozoic. Atmospheric dioxygen (O2) plays a vital role in the Earth system , regulating the biosphere through fire ignition and metabolism of aerobic biota. Hence, variability in the partial pressure of dioxygen (pO2, a measure of the mass of O2 in the atmosphere, assuming N2 and the volume of the atmosphere have been constant) over time has been invoked as an evolutionary trigger of both animals and plants at many points in the Phanerozoic .
Figure 1Oxygen content reconstructions in the Phanerozoic from , , , , and . The mean (black line) and range (grey shading) of the , and is indicated, as these reconstructions were most consistent with ice core evidence . Present-day atmospheric oxygen content is indicated by the solid horizontal grey line. Timings of the palaeo case studies explored in this study are indicated by the dotted vertical lines (As: Asselian, Wu: Wuchiapingian, Ma: Maastrichtian).
While strong biological and geological feedbacks prevent rapid swings in atmospheric oxygen , reconstructions of past atmospheric oxygen content suggest that there have been substantial excursions from the 21 % oxygen content present in today's atmosphere at times in the Phanerozoic eon. These reconstruction methods can be divided into forward and inversion models. Forward models include nutrient/weathering models and isotope mass balance models , while inversion models infer oxygen content from proxies such as charcoal , organic-carbon-to-phosphorus ratios and plant resin δ13C . Figure 1 shows the reconstructed oxygen content for a variety of these methods. There is general agreement in the trends in the reconstructions, in that oxygen content increased from 5 % to 25 % in the early Paleozoic to 20 %–35 % in the Permian and subsequently stabilised at levels around 15 %–30 % from the Middle Triassic onward. However, there is uncertainty in the absolute amount of O2 for the different reconstructions (grey shading in Fig. 1). Indeed, there is support for elevated O2 by carbon isotope measurements during the Permian . However, disagreement is particularly evident in the Mesozoic, with low values simulated by isotope mass balance approaches. have shown that this could be due to an inappropriate choice of δ13C and that adjusting this value with geological constraints leads to a higher reconstructed oxygen content in better agreement with wildfire records. At the time of writing, there are no direct geochemical proxies for atmospheric pO2 on the Phanerozoic timescale. However, there is isotopic evidence of oceanic oxygenation in steps at approximately 560 , 400 and 200 Ma . pO2 in the last 800 000 years has been reconstructed using O2∕N2 ratios in ice cores . A roughly 7 ‰ decline in pO2 is consistent with the ability to change oxygen content by the order of a few percent in ∼10 Myr. The reconstructions of , and are the most plausible based on ice core data . Considering these three models alone would still suggest a large uncertainty in oxygen content for most of the Phanerozoic, except for elevated levels in the late Carboniferous/early Permian and reduced levels in the late Devonian.
Phanerozoic means “visible life” and one of the marked changes to carbon cycling between the Proterozoic and Phanerozoic was caused by the emergence of land plants. The radiation of land plants has led to strong regulation of atmospheric CO2 and O2 which both play important roles in photosynthesis. Land plants likely led to a substantial sequestration of carbon in the terrestrial biosphere and possibly led to the Ordovician glaciation . Increases in organic carbon sequestration in the aftermath of the evolution of lignin production may also have contributed to the cooling (Robinson1989). This fundamental change to the Earth system may have constrained CO2 levels to between 10 and 200 Pa ever since . have argued that strong fire feedbacks prevent large fluctuations in oxygen levels, due to runaway burning at high oxygen levels. However, subsequent experiments using natural fuels support the possibility of the Earth system to support higher oxygen levels . Charcoal appears in the fossil record continuously since the late Devonian (∼360 Ma; ). This suggests a floor on oxygen levels in the region of 12 % to 16 % since then due to limits on ignition.
Variations in pO2 also have important implications for photosynthesis and therefore the operation of the terrestrial carbon cycle. The primary CO2-fixing enzyme, RuBisCO, possesses a dual carboxylase–oxygenase function (Smith1976). A photosynthetic carboxylase pathway removes CO2 from the atmosphere, while oxygenation leads to photorespiration and CO2 evolution. Therefore, increases in pO2 ought to lead to O2 outcompeting CO2 for active sites on the RuBisCO enzyme and leading to a reduction in net primary productivity (less photosynthesis, more respiration). However, photorespiration is likely to be necessary for removal of harmful byproducts in the photosynthetic metabolic pathway , and a recent study suggests that increases in photorespiration may actually promote photosynthesis . Photosynthesis is itself sensitive to the background CO2 content . In addition, temperature modifies the relative solubilities of CO2 and O2 . Temperature also affects the specificity of RuBisCO for CO2 (Long1991). Therefore, the coevolution of pO2, pCO2 and temperature across the Phanerozoic has the capacity to significantly impact the terrestrial carbon cycle.
This paper focuses on investigating the climate impacts of atmospheric mass variation as the result of altering the concentration of O2. Lower atmospheric mass leads to less Rayleigh scattering so more shortwave radiation reaches the Earth’s surface. This enhances atmospheric convection and the hydrological cycle, which leads to more tropospheric water vapour, further enhancing warming. However, lower atmospheric mass leads to a reduction in the pressure broadening of greenhouse gas absorption lines which should lead to a weaker greenhouse effect and lead to cooling. Previous modelling studies have investigated which factor dominates with conflicting results. presented radiative–convective model simulations for the Archean (∼ 3 Ga), which suggested that a nitrogen inventory around 3 times larger than present would help to keep the early Earth warm at a time when solar input was only around 75 % of what it is today, potentially solving the “Faint Young Sun” paradox (Feulner2012). investigated this using a general circulation model (GCM) coupled to a slab ocean and found that for their idealised early Earth simulations they achieved a strong warming (+7 C) in response to a doubling in atmospheric mass. simulated the climate impacts of changes in O2 content over a range of 5 %–35 % using the GENESIS climate model with a slab ocean and a continental configuration consistent with the Cenomanian (mid-Cretaceous, 95 Ma) and found the opposite response – lower atmospheric mass at low pO2 was associated with a strong warming. Subsequent 1-D calculations cast doubt on this result ; however, it is plausible that other climate feedbacks such as changes to relative humidity and cloud changes may be important as atmospheric mass changes. These would not be accounted for in 1-D radiative–convective equilibrium simulations. Cloud feedbacks in particular are a good candidate for explaining the discrepancy as cloud feedbacks under CO2-driven climate change have strong model dependency . Another feedback which has not been considered is the possible impact of changes in the mechanical forcing of wind on the ocean circulation. In the absence of this effect, Earth’s surface temperature would be 8.7 K cooler (Saenko2009) and the Equator-to-pole temperature gradient would be steeper. Wind stress (τ) is parameterised in GCMs as $\mathit{\tau }=\mathbit{\rho }\phantom{\rule{0.25em}{0ex}}\mathbit{u}\cdot \mathbit{u}$, where ρ is the atmospheric density and u is the surface wind vector. So, as atmospheric density increases, the wind stress on the ocean and therefore ocean heat transport should increase accordingly. Increased meridional heat transport in high-density atmospheres is also supported by an idealised 2-D modelling study of the early Earth . As slab ocean models assume a constant or diffusive ocean heat transport, the and simulations cannot account for these effects.
As pO2 variability may alter the radiative budget of the atmosphere, it may also have impacts on the sensitivity of the climate state to CO2 changes. The equilibrium climate sensitivity (ECS) is a metric for the sensitivity of a climate model to an abrupt doubling of atmospheric CO2. Understanding this value is important for predictions of both past and future climatic changes. As the radiative forcing of CO2 is approximately logarithmic with concentration, theoretically the ECS should be constant in time as carbon dioxide changes. However, there is growing evidence that ECS has not been constant over Earth's history . Changes to the incoming solar radiation , palaeogeography , CO2 levels themselves and tropical sea-surface temperatures may lead to changes in the sensitivity of a particular climate state to changes in CO2.
2 Methods and simulations
2.1 Models
The impact of oxygen content variability is investigated with two coupled atmosphere–ocean general circulation models (AOGCMs): Hadley Centre Coupled Model version 3 (HadCM3-BL) and Hadley Centre Global Environmental Model version 3 (HadGEM3-AO).
HadGEM3-AO is an AOGCM . The atmosphere component is the UK Met Office Unified Model version 7.3 in the HadGEM3-A r2.0 climate configuration . It employs a regular Cartesian grid of 3.75 longitude by 2.5 latitude (N48). In the vertical, 60 hybrid height vertical levels are employed – “hybrid” indicating that the model levels are sigma levels near the surface, changing smoothly to pressure levels near the top of the atmosphere . The model top is 84 km, which permits a detailed treatment of stratospheric dynamics. A 20 min time step is used. The model employs a non-hydrostatic and fully compressible dynamical core, using a semi-implicit semi-Lagrangian advection scheme on a staggered Arakawa C grid . Radiation is represented using the scheme with six shortwave and nine longwave bands, accounting for the radiative effects of water vapour, carbon dioxide, methane, nitrous oxide and ozone. The Met Office Surface Exchange Scheme 2 (MOSES2) land surface scheme is used , which simulates atmosphere–land exchanges and hydrology. A fixed present-day vegetation distribution of plant functional types is employed. The ocean component of the model is NEMO-OPA (Nucleus for European Modelling of the Ocean - Océan Parallélisé; ) model version 3.0 , run at a 96 min time step. In the vertical, 31 model levels are used, which increase in thickness steadily between 10 m in the shallowest to 500 m in the deepest layer at 5 km in depth. NEMO employs a tripolar, locally anisotropic grid (ORCA2; ) which permits a more detailed treatment of the north polar region and higher resolution in the tropics. This yields an approximate horizontal resolution of 2 in both longitude and latitude, with an increased resolution of up to 0.5 in the tropics. The sea-ice component of the model is CICE (Los Alamos Community Ice CodE) at version 4.0 , run at a 96 min time step. This treats sea ice in a five-layer model, allowing the simulation of different ice types. The atmosphere and ocean/sea-ice components exchange fields every 24 h, while NEMO and CICE exchange fields every time step. HadGEM3-AO can be thought of as a close relation to the newest-generation HadGEM3 coupled model that will be used to support the next Intergovernmental Panel on Climate Change (IPCC) assessment and so represents the state of science in numerical climate models.
HadCM3-BL is an AOGCM coupled to an interactive vegetation model. The model was originally developed by the United Kingdom Met Office Hadley Centre but has since been substantially developed further by the University of Bristol. The atmosphere component of the model employs a regular Cartesian grid of 3.75 longitude by 2.5 latitude. In the vertical, 19 hybrid height vertical levels are employed. A 30 min time step is used. The primitive equation set of is solved to conserve energy and angular momentum, solved on a staggered Arakawa B grid in the horizontal. Radiation is represented using the scheme with six shortwave and eight longwave bands, accounting for the radiative effects of water vapour, carbon dioxide and ozone, amongst other radiative active species. The ocean component of the model employs the same horizontal grid as the atmosphere component of the model, 3.75 longitude by 2.5 latitude. In the vertical, 20 model levels are used which increase in depth from 10 m in the shallowest layer to 616 m in the deepest layer. A time step of 60 min is employed and the ocean and atmosphere components exchange required fields once per day. The ocean component is based on the Cox (1984) model, solving the full primitive equation set in three dimensions. A staggered Arakawa B grid is employed in both atmosphere and ocean models. Sea ice is treated as a zero thickness layer on the surface of the ocean grid. Ice is assumed to form at the base at a freezing point of 1.8 C but can also form from freezing in ice leads and by falling snow. A simple parameterisation of sea-ice dynamics is also employed and sea-ice formation due to convergence from drift being limited to 4 m thick. Sea-ice albedo is fixed at 0.8 for temperatures below 10 C, decreasing linearly to 0.5 at 0 C. The MOSES2.1 land surface model is employed to simulate the fluxes of energy and water between the land surface and the atmosphere . TRIFFID (Top-down Representation of Interactive Foliage and Flora Including Dynamics; ) predicts the distribution of vegetation using a plant functional type (PFT) approach. TRIFFID is run in equilibrium mode with averaged fluxes calculated over a 5-year period. TRIFFID calculates vegetation properties for five PFTs: broadleaf trees, needleleaf tree, C3 grass, C4 grass and shrubs. Grid boxes can contain a mixture of PFTs based on a “fractional coverage co-existence approach” . Net primary productivity (NPP) is also calculated, using a photosynthesis-stomatal conductance model accounting for a number of factors including atmospheric oxygen content, which affects the photorespiration compensation point . The predicted vegetation distribution impacts the atmosphere component by altering surface albedo, evapotranspiration and surface roughness.
Figure 2Annual average surface air temperature simulated in (a) PI-CM21, (b) Ma-CM21, (c) Wu-CM21 and (d) As-CM21. Global-mean values are indicated in the top right. The 0 C isoline is indicated in pink. Continental outlines are indicated with a solid black line.
Figure 3Annual average precipitation simulated in (a) PI-CM21, (b) Ma-CM21, (c) Wu-CM21 and (d) As-CM21. Global-mean values are indicated in the top right. Continental outlines are indicated with a solid black line.
2.2 Boundary conditions
Both models simulated the climate response to oxygen variability in a pre-industrial Holocene (PIH) climate. HadCM3-BL was additionally run for three time periods across the Phanerozoic: the Maastrichtian (late Cretaceous, 66.0–72.1 Ma), Wuchiapingian (late Permian, 254.14–259.1 Ma) and the Asselian (early Permian, 295.0–298.9 Ma). The continental reconstructions employed were developed by and are from ©Getech. These reconstructions have been widely employed in a number of previous studies using the HadCM3-BL climate model (e.g. ). All three are periods of time in which models have suggested that atmospheric oxygen may have deviated significantly from the present level of 21 % (see Fig. 1). Modifications were made to alter the oxygen content of the atmosphere by adjusting the mass mixing ratios of major and minor gases, the surface pressure and other physical characteristics of the atmosphere such as the specific gas constant in an analogous way to . Figure 2 shows the annual average surface temperatures and Fig. 3 shows the annual average precipitation for the (a) PI-CM21, (b) Ma-CM21, (c) Wu-CM21 and (d) As-CM21 simulations.
Table 1Summary of experiments. Experiment names AA-BBB include the continental configuration (AA) and model used (BBB). Experiment names N × AA-BBB indicate a multiplier of CO2 with respect to AA-BBB. A star (*) indicates that the CO2 multiplier was applied instantaneously and the transient adjustment to climate was analysed for the purpose of a analysis.
A summary of the experiments performed can be found in Table 1. When an experiment with a particular oxygen content is referred to, it will be indicated in superscript; e.g. EXP21 indicates a 21 % oxygen simulation. The 21 % simulations (PI-CM21, As-CM21, Ma-CM21 and Wu-CM21) were integrated for 50 model years, as these simulations had already been spun up at that CO2 content. For 10 % and 35 % pO2, the model was spun off the 21 % pO2 simulation and iterated for at least 1000 model years. The 2 × PI-CM*, 2 × Ma-CM* and 2 × As-CM* experiments were spun off from the end of the PI-CM, Ma-CM and As-CM experiments and iterated for 100 years in order to perform a analysis. For HadGEM3-AO, model integrations (PI-GEM35, PI-GEM10, 4 × PI-GEM35 and 4 × PI-GEM10) were performed for 300 model years with a 10× acceleration of the deep ocean to reduce the time for equilibrium, then integrated for a further 500 years to spin up the shallow ocean without acceleration. The last 50 years were used for model analysis.
Pre-Quaternary pCO2 is poorly constrained due to the absence of glacial ice; however, there is growing evidence that CO2 is unlikely to have been significantly higher than the order of hundreds of Pa since the radiation of land plants . For the Maastrichtian, 56 Pa is used in agreement with stomatal proxy-based reconstructions . For the Asselian, 28 Pa is used in agreement with carbonate and fossil plant reconstructions . For the Wuchiapingian, 112 Pa is used .
1-D atmospheric chemistry simulations have simulated higher O3 column with increasing pO2 . More detailed 2-D model simulations, which capture critical latitudinal gradients in photolysis and zonal-mean transport , support a monotonically increasing ozone column with increasing pO2 . However, simulated ozone column was more sensitive to N2O levels than pO2 . In addition, while column ozone reduces at low pO2 in , there are increases in ozone concentration in the tropical tropopause region where the radiative effect of O3 is stronger . Changes in lightning are important for understanding future changes in tropospheric ozone ; however, they are subject to considerable uncertainty . There may be more lightning at high pO2 due to a higher pO2pN2 ratio or less due to reduced convection . Low pO2 may also enhance isoprene emissions , which could enhance tropospheric ozone and alter cloud properties . Ozone is also sensitive to changes in CH4 and N2O; the changes to inventories of these chemically active species on the Phanerozoic timescale are highly uncertain. Ozone is also sensitive to dynamical changes. Given these large uncertainties in possible changes to chemical sources, reactivity and transport, we neglected including changes in atmospheric ozone concentration in these simulations. However, we recommend that follow-up work should focus on this specific question in detail. In HadGEM3-AO, the mass of tropospheric and stratospheric ozone is fixed at PIH values simulated by using a tropopause height-matching scheme. This prevents a rising tropopause leading to stratospheric levels of ozone existing in the troposphere, particularly in the 4 × PI-GEM experiments. Not accounting for a rising tropopause has been found to artificially increase climate sensitivity and initial tests not accounting for this led to instability for 4 × PI-GEM10. In HadCM3-BL, tropospheric ozone is set to 6 ppbv and stratospheric ozone is set to 1.66 ppmv for the 21 % simulations. These values are adjusted to conserve total ozone mass in the alternative pO2 scenarios.
2.3 Data
Data for the Cenomanian 21 % O2 and 10 % O2 simulations were obtained from https://www.ncdc.noaa.gov/paleo/study/18776 (last access: 21 February 2018). At the time of writing, the 35 % simulation contained missing data, so it was not used for analysis.
2.4 1-D energy balance model
A 1-D energy balance model (EBM) has been used to deconvolve the contributions from changes in different parts of the climate system. This 1-D EBM approach has been applied to zonal-mean quantities for climate simulations of the Eocene by following and :
$\begin{array}{}\text{(1)}& \begin{array}{rl}& {\mathrm{SW}}_{\mathrm{t}}^{↓}\left(\mathit{\varphi }\right)\left[\mathrm{1}-\mathit{\alpha }\left(\mathit{\varphi }\right)\right]-\frac{\mathrm{1}}{\mathrm{2}\mathit{\pi }\phantom{\rule{0.125em}{0ex}}{R}^{\mathrm{2}}\mathrm{cos}\left(\mathit{\varphi }\right)}\frac{\partial F\left(\mathit{\varphi }\right)}{\partial \mathit{\varphi }}\\ & \phantom{\rule{0.25em}{0ex}}\phantom{\rule{0.25em}{0ex}}\phantom{\rule{0.25em}{0ex}}=\mathit{ϵ}\left(\mathit{\varphi }\right)\mathit{\sigma }{T}_{\mathrm{s},\phantom{\rule{0.125em}{0ex}}\mathrm{ebm}}^{\mathrm{4}}\left(\mathit{\varphi }\right),\end{array}\end{array}$
where SW${}_{\mathrm{t}}^{↓}$ is the incident shortwave radiation at the top of the atmosphere, ϕ is the latitude, α is the surface albedo, R is the radius of Earth, ϵ is the effective surface emissivity, and Ts, ebm is the EBM surface temperature . $\frac{\partial F\left(\mathit{\varphi }\right)}{\partial \mathit{\varphi }}$ is the divergence of total meridional heat transport and is given by
$\begin{array}{}\text{(2)}& \frac{\partial F\left(\mathit{\varphi }\right)}{\partial \mathit{\varphi }}=-\mathrm{2}\mathit{\pi }{R}^{\mathrm{2}}\mathrm{cos}\left(\mathit{\varphi }\right)\left({\mathrm{SW}}_{\mathrm{t}}^{\mathrm{net}}\left(\mathit{\varphi }\right)+{\mathrm{LW}}_{\mathrm{t}}^{\mathrm{net}}\left(\mathit{\varphi }\right)\right),\end{array}$
where SW${}_{\mathrm{t}}^{\mathrm{net}}$ and LW${}_{\mathrm{t}}^{\mathrm{net}}$ are the net top-of-atmosphere shortwave and longwave radiative fluxes, respectively (positive downward; ). Solving for Ts, ebm, the EBM surface temperature for each latitude can be calculated using zonal- and annual-mean radiative fluxes from the GCM. Where clear-sky radiative fluxes are also available, cloud radiative effects can be deconvolved from clear-sky radiative effects. The clear-sky albedo αc and clear-sky effective surface emissivity ϵc can be calculated by
$\begin{array}{}\text{(3)}& {\mathit{\alpha }}_{\mathrm{c}}=\frac{{\mathrm{SW}}_{\mathrm{t},\mathrm{c}}^{↑}}{{\mathrm{SW}}_{\mathrm{t}}^{↓}},{\mathit{ϵ}}_{\mathrm{c}}=\frac{{\mathrm{LW}}_{\mathrm{t},\mathrm{c}}^{↑}}{{\mathrm{LW}}_{\mathrm{s}}^{↑}},\end{array}$
where SW${}_{\mathrm{t},\mathrm{c}}^{↑}$ is the upward top-of-atmosphere clear-sky shortwave radiative flux and LW${}_{\mathrm{t},\mathrm{c}}^{↑}$ is the upward top-of-atmosphere clear-sky longwave radiative flux. When considering the temperature change between two experiments, the contributions from different components can be quantified by calculating Ts, ebm with different combinations of components from each experiment .
2.5 Climate sensitivity
To estimate the climate sensitivity to CO2 changes, the linear regression methodology of is employed. This assumes a linear relationship between the changes in global, annual-mean radiative imbalance at the top of the atmosphere (N, W m−2) and surface temperature anomalies (Ts, C):
$\begin{array}{}\text{(4)}& N=F+\mathit{\xi }\mathrm{\Delta }{T}_{\mathrm{s}},\end{array}$
where ξ is the effective climate feedback parameter ($\mathrm{W}\phantom{\rule{0.125em}{0ex}}{\mathrm{m}}^{-\mathrm{2}}{}^{\circ }{\mathrm{C}}^{-\mathrm{1}}$) and F is the effective forcing (W m−2) accounting for fast climate adjustments and effective radiative forcing. The effective ECS is then ΔTs when N=0. While there are weaknesses of this approach, particularly due to non-linearities in ξ as ΔTs changes , the climate response when simulations are continued to equilibrium shows an accuracy to within 10 % . Furthermore, the contributions to ξ and F from longwave (LW) and shortwave (SW), clear-sky (CS) and cloudy-sky (CRE) components can be decomposed by a linear decomposition as
$\begin{array}{}\text{(5)}& F={F}_{\mathrm{CS},\mathrm{SW}}+{F}_{\mathrm{CS},\mathrm{LW}}+{F}_{\mathrm{CRE},\mathrm{SW}}+{F}_{\mathrm{CRE},\mathrm{LW}}\end{array}$
for the effective forcing and
$\begin{array}{}\text{(6)}& \mathit{\xi }={\mathit{\xi }}_{\mathrm{CS},\mathrm{SW}}+{\mathit{\xi }}_{\mathrm{CS},\mathrm{LW}}+{\mathit{\xi }}_{\mathrm{CRE},\mathrm{SW}}+{\mathit{\xi }}_{\mathrm{CRE},\mathrm{LW}}\end{array}$
for the effective climate feedback parameter.
3 Results
Where results are presented from a single simulation, the oxygen content for that run is written in superscript, i.e. EXP21 indicates a 21 % oxygen simulation. Where results are presented as an anomaly between simulations with different oxygen content, ${\mathrm{EXP}}_{\mathrm{0}}^{\mathrm{21}}$ indicates that the quantity presented is EXP21 minus EXP0. A summary of results is shown in Table 2.
Table 2Summary of results for EXP21, then EXP${}_{\mathrm{10}}^{\mathrm{35}}$. Where applicable, results calculated for the Cenomanian 21 %–10 % oxygen simulation are also presented. Abbreviations: Teq-pole (Equator-to-pole surface air temperature gradient), Teq-pole,cold month (Equator-to-pole surface air temperature gradient for cold months), EBM (quantities obtained using a Budyko–Sellers 1-D energy balance model following Heinemann, 2009), Ts,ebm (EBM surface temperature), ${T}_{\mathrm{s},\mathrm{csky},\mathrm{ebm}}$ (EBM surface temperature change accounting for changes in clear-sky radiative fluxes), ${T}_{\mathrm{s},\mathrm{cre},\mathrm{ebm}}$ (EBM surface temperature change accounting for changes in cloudy-sky radiative fluxes), ${T}_{\mathrm{s},\mathrm{mht},\mathrm{ebm}}$ (EBM surface temperature change accounting for changes in meridional heat flux divergence).
3.1 Surface climate
Figure 4 (left) shows the annual-mean surface air temperature differences between the 35 % and 10 % runs. For the pre-industrial Holocene, PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$ (Fig. 4a) shows a global-mean surface temperature response of +1.50 C, while PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$ (Fig. 4b) shows a similar global-mean surface temperature response of +1.22 C. It is worth noting that HadCM3-BL and HadGEM3-AO are not completely distinct climate models, for instance, sharing the radiation scheme, so this is unlikely to capture the full variability in possible climate model responses. That the results are in reasonable agreement with the 1-D results of , who simulated a temperature response between +1.05 and +2.21 C depending on assumptions about atmospheric ozone, gives some confidence in the HadCM3-BL and HadGEM3-AO results. Similarly, the As-CM${}_{\mathrm{10}}^{\mathrm{35}}$ (Fig. 4c) case exhibits a global-mean surface temperature response of +1.29 C. For the warmest climates, a response of 0.82C is simulated for Wu-CM${}_{\mathrm{10}}^{\mathrm{35}}$ (Fig. 4e) and +0.17 C for 4 × PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$ (Fig. 4f). In the Ma-CM${}_{\mathrm{10}}^{\mathrm{35}}$ case (Fig. 4d), a global-mean surface temperature response of +0.70 C is simulated. This suggests that the climate response to pO2 variability depends on the background climate state.
Figure 4Surface air temperature change for (a) PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$, (b) PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (c) As-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (d) Ma-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (e) Wu-CM${}_{\mathrm{10}}^{\mathrm{35}}$ and (f) 4 × PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$ in the annual mean (left), cold-month mean (change in the mean grid box temperature of the coldest month in the monthly mean climatology, middle) and warm-month mean (change in the mean grid box temperature of the warmest month in the monthly mean climatology, right). The change in global-mean values (C) are offset to the top right of each plot. Note the strong high-latitude warming in the cold-month mean and tropical cooling in the warm-month mean.
There is a strong seasonal dependence in the surface air temperature response. Considering the changes in coolest average monthly temperature in each grid box (Fig. 4, middle column), the change in cool months dominates the warming response, particularly at high latitudes. By contrast, the warm-month mean is smaller/less negative in all cases (Fig. 4, right). A cooling of continental land masses is evident in the tropics and particularly in the Wu-CM (Fig. 4e) and 4 × PI-GEM (Fig. 4f) cases. These could be in part due to free-air lapse rate changes which should be stronger at high pO2; as for a given topographic height, the change in pressure is higher for high pO2, which should lead to a larger temperature reduction with height. The changes to the seasonal cycle are consistent with the radiative changes associated with changing oxygen content. The reduction in incident surface shortwave radiation should have its strongest effect on extratropical temperatures in the summer; therefore, the Rayleigh scattering component will most strongly affect the warm-month temperature. Warming from pressure broadening of greenhouse gas absorption lines as atmospheric mass increases will be most evident in extratropical winter, as with anthropogenic climate change, due to sea-ice and surface heat flux changes . The reduction in the amplitude of the seasonal cycle in temperature simulated by both HadGEM3-AO and HadCM3-BL is therefore supported by a consideration of the changes to atmospheric radiation.
Figure 5Zonally and annually averaged surface air temperature difference (solid lines) from 10 % to 35 % oxygen content for PI-GEM (blue), 4 × PI-GEM (red), As-CM (pink), Ma-CM (green) and Wu-CM (purple). The difference from the annual mean to cold-month mean for each run is indicated by the shading. Values are smoothed by a Savitzky–Golay filter .
The zonal- and annual-mean surface air temperature changes are shown in Fig. 5. The Northern Hemisphere Equator-to-pole temperature gradient is reduced by 6.6 C in the PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$ case (blue line) and 4.0 C in the PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$ case (not shown). The zonal structure of the surface temperature change is similar in the palaeoclimate case studies. In the Maastrichtian, the Equator-to-pole temperature gradient is reduced by 2.0 C (Ma-CM${}_{\mathrm{10}}^{\mathrm{35}}$) and in the Asselian the Equator-to-pole temperature gradient is reduced by 2.3 C (As-CM${}_{\mathrm{10}}^{\mathrm{35}}$). The Equator-to-pole temperature gradient reduces even in the Wu${}_{\mathrm{10}}^{\mathrm{35}}$ case despite the reduction in global-mean surface temperatures.
Figure 6Annually averaged total precipitation change from 10 % to 35 % oxygen content for (a) PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$, (b) PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (c) As-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (d) Ma-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (e) Wu-CM${}_{\mathrm{10}}^{\mathrm{35}}$ and (f) 4 × PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$. Global-mean values (mm d−1) are offset to the top right of each plot.
The hydrological cycle is also affected by changing oxygen content. Increases in Rayleigh scattering at high pO2 ought to reduce incident shortwave at the Earth's surface and inhibit convection , which should lead to reductions in precipitation. This is analogous to stratospheric sulfate or solar radiation management geoengineering where precipitation is reduced in geoengineering experiments with respect to an unperturbed climate with the same global-mean surface temperature . simulated large reductions in precipitation as pO2 increased in the GENESIS climate model; however, much of this could be explained by the surface temperature changes. Annually averaged precipitation change between the 10 % and 35 % oxygen content runs is shown in Fig. 6. In all cases, increasing oxygen content leads to a decline in global-mean total precipitation, despite the increase in surface temperatures, however, with strong regional differences. For PI-GEM (Fig. 6a), PI-CM (Fig. 6b) and 4 × PI-GEM (Fig. 6f), there is a clear northward shift in the tropical rainbelts. A northward shift in the Intertropical Convergence Zone (ITCZ) would be consistent with stronger warming in the Northern Hemisphere due to Bjerknes compensation . Heat transport is more hemispherically symmetric in the Maastrichtian, Asselian and Wuchiapingian cases so latitudinal ITCZ shifts are not evident. While global precipitation is reduced in Wu-CM35, the increase in ocean–land temperature contrast leads to a significant increase in tropical land precipitation. Despite the increases in global-mean surface temperatures simulated for most cases, precipitation is still reduced in all simulations.
Comparing the surface temperature and precipitation response between HadCM3-BL and HadGEM3-AO suggests that the model responses are broadly consistent. A grid-box-by-grid-box comparison of annual-mean surface air temperature and precipitation anomalies for PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$ vs. PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$ is presented in Fig. S1 in the Supplement. The largest discrepancy in surface air temperature response between the two models occurs for the largest temperature changes simulated by HadGEM, which are strongest in Northern Hemisphere polar regions. This could be linked to differences in the representation of polar climate processes and amplification by polar ice feedbacks between the two models. There is broad consistency in cold- and warm-month means (Fig. 4a and b) with stronger warming in the cold-month mean and terrestrial cooling in the warm-month mean.
3.2 Energy balance decomposition
The drivers of the changes in surface temperature can be understood by decomposing the terms which contribute to surface temperature change in a 1-D energy balance model following . For PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$, these results are shown in Fig. 7. These show that the 1-D EBM can reasonably capture the temperature response in the HadCM3-BL simulations, with slight errors (where the black and grey lines are not overlapping) evident in the polar regions. This could be due to averaging over the polar rows in the HadCM3-BL model. There are positive contributions to the surface temperature change in the clear-sky emissivity and albedo at the poles. This is consistent with the increase in pressure broadening of absorption lines and the simulated reduction in sea-ice extent. By contrast, extrapolar contributions to clear-sky albedo provide a negative contribution to the temperature change which is consistent with an increase in Rayleigh scattering which would be expected to be strongest in the tropics where the maximum in incoming solar radiation is located. Combined, the clear-sky component of the temperature change is +1.45C and the cloudy-sky component is 0.35C. This suggests that HadCM3-BL supports a cloud feedback which acts to cool the climate at high pO2 and partially offset the clear-sky temperature changes.
Figure 7The 1-D EBM decomposition for PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$. (a) EBM results (grey) vs. GCM results (black). (b) Decomposition of EBM into the emissivity (purple), albedo (green) and heat transport (orange) components of the temperature change. (c) Clear-sky emissivity (dark purple) and clear-sky albedo (dark green) components of the EBM. The all-sky components are included for comparison. (d) Decomposition of EBM into the total clear-sky (blue), cloudy-sky (red) and all-sky (grey) components.
Figure 81-D EBM decomposition for PI-GEM${}_{\mathrm{10}}^{\mathrm{35}}$. (a) EBM results (grey) vs. GCM results (black). (b) Decomposition of EBM into the emissivity (purple), albedo (green) and heat transport (orange) components of the temperature change. (c) Clear-sky emissivity (dark purple) and clear-sky albedo (dark green) components of the EBM. The all-sky components are included for comparison. (d) Decomposition of EBM into the total clear-sky (blue), cloudy-sky (red) and all-sky (grey) components.
The same analysis was performed for the HadGEM3-AO PIH simulations. Figure 8 shows that a somewhat weaker cloud feedback is simulated by HadGEM3-AO (0.21 C). Clear-sky contributions are slightly stronger (+1.51 C). The largest differences between the simulations appear in the all-sky albedo and emissivity changes, where there appear to be competing factors which lead to a similar climate response possibly related to partitioning between the longwave and shortwave contributions to the cloud response. This is perhaps unsurprising, as cloud feedbacks to CO2 changes represent a large uncertainty in future climate change projections, and given the relatively small global-mean temperature changes, a relatively small change in cloud radiative effects has the power to considerably mediate the climate response. However, the qualitative agreement in latitudinal structure of the clear-sky albedo and emissivity changes between these structurally different models gives some confidence that the relevant climate feedbacks are well captured in these simulations.
Analysis of the palaeo case studies (As-CM, Fig. S2; Ma-CM, Fig. S3; Wu-CM, Fig. S4) shows a similar pattern. In all simulations, irrespective of surface temperature response, the clear-sky emissivity is a positive contribution to global-mean surface temperature change, while clear-sky albedo is a more negative contribution. The emissivity contribution becomes less positive as pCO2 increases from As-CM to Ma-CM to Wu-CM. By contrast, the albedo contribution becomes more negative as pCO2 increases. This is consistent with the reduction in planetary albedo as sea-ice extent is reduced on the ocean and dark vegetated surfaces increase on the land.
Figure 9Gregory analysis of HadCM3-BL: regression of top-of-atmosphere radiative imbalance against surface air temperature change (solid lines) for the first 100 years of 2 × PI-CM10 (pink) and 2 × PI-CM35 (blue) cases. Annual averages are indicated by crosses and decadal averages are indicated by filled circles. The regression was performed on the decadal averages.
Figure 10Gregory analysis of HadCM3-BL: regression of top-of-atmosphere radiative imbalance against surface air temperature change (solid lines) for the first 100 years of 2 × As-CM10 (pink) and 2 × As-CM35 (blue) cases. Annual averages are indicated by crosses and decadal averages are indicated by filled circles. The regression was performed on the decadal averages.
3.3 Climate sensitivity
Here, we investigate the impact of oxygen variability on climate sensitivity. The HadGEM3-AO and HadCM3-BL results suggest that increasing CO2 content leads to a reduction in the surface temperature change on increasing pO2 (compare 4 × PI-GEM and PI-GEM in Fig. 4). For reference, HadGEM3 has a climate sensitivity of +3.6 C , while HadCM3 has a climate sensitivity of +3.1 C . From the 4 × PI-GEM and PI-GEM experiments, a reduction in climate sensitivity of 0.65 C can be inferred based on the changes in surface temperatures. For HadCM3, CO2-doubling experiments were performed, and a regression of the change in top-of-atmosphere radiative imbalance against change in surface temperature following (see also Sect. 2.4) is shown in Fig. 9. The PI-CM35 climate state has a smaller ECS than PI-CM10 by 0.7 C. While the changes in total radiative forcing F are very similar, ξ is less negative (1.08 vs. 1.37 $\mathrm{W}\phantom{\rule{0.125em}{0ex}}{\mathrm{m}}^{-\mathrm{2}}{}^{\circ }{\mathrm{C}}^{-\mathrm{1}}$) at low pO2. The decomposition of these changes into their longwave and shortwave components, clear-sky and cloudy-sky components is also shown in Fig. 9. The clear-sky longwave radiative flux changes are slightly higher in 2 × PI-CM35 (4.0 W m−2) than 2 × PI-CM10 (3.8 W m−2) as would be expected due to the pressure broadening of CO2. The clear driver for the less negative ξ value are from the longwave cloud radiative effect changes, which is much steeper for 2 × PI-CM10 (+0.62 $\mathrm{W}\phantom{\rule{0.125em}{0ex}}{\mathrm{m}}^{-\mathrm{2}}{}^{\circ }{\mathrm{C}}^{-\mathrm{1}}$) than 2 × PI-CM35 (+0.17 $\mathrm{W}\phantom{\rule{0.125em}{0ex}}{\mathrm{m}}^{-\mathrm{2}}{}^{\circ }{\mathrm{C}}^{-\mathrm{1}}$). This is somewhat offset by stronger clear-sky shortwave radiative feedbacks in 2 × PI-CM35 (+1.00 $\mathrm{W}\phantom{\rule{0.125em}{0ex}}{\mathrm{m}}^{-\mathrm{2}}{}^{\circ }{\mathrm{C}}^{-\mathrm{1}}$) than 2 × PI-CM10 (+0.57 $\mathrm{W}\phantom{\rule{0.125em}{0ex}}{\mathrm{m}}^{-\mathrm{2}}{}^{\circ }{\mathrm{C}}^{-\mathrm{1}}$). This highlights the important role that cloud radiative feedbacks play in determining the climate sensitivity.
Figure 11Gregory analysis of HadCM3-BL: regression of top-of-atmosphere radiative imbalance against surface air temperature change (solid lines) for the first 100 years of 2 × Ma-CM10 (pink) and 2 × Ma-CM35 (blue) cases. Annual averages are indicated by crosses and decadal averages are indicated by filled circles. The regression was performed on the decadal averages.
An increase in ECS appears to be robust across the HadCM3-BL experiments. For As-CM, ECS is 0.8 C lower at 35 % O2 than 10 % O2 (Fig. 10). For Ma-CM, this value is much larger. A 3.3 C reduction in ECS is simulated, which is also driven by the longwave cloud radiative effects in conjunction with a weaker clear-sky shortwave radiative effect which tended to cool the low pO2 (Fig. 11). Unlike the clear-sky shortwave effects, the longwave cloud radiative effects seem consistent across the three experiments. It should be noted that attempts were made to simulate 2× experiments for the Wuchiapingian; however, what would have been the 2 × Wu-CM10, in the nomenclature used here, was numerically unstable.
Figure 12Change in column water vapour in (a) PI-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (b) As-CM${}_{\mathrm{10}}^{\mathrm{35}}$, (c) Ma-CM${}_{\mathrm{10}}^{\mathrm{35}}$ and (d) Wu-CM${}_{\mathrm{10}}^{\mathrm{35}}$. Global sum values (petagrams) are offset to the top right of each plot. Note the atmospheric drying at high pO2 is enhanced in the warmer climate states of the Wuchiapingian and Maastrichtian and more subdued in the cooler climate states of the Asselian and Holocene.
The increase in climate sensitivity appears to be linked to the reduction in temperature anomaly in a warmer climate state. We propose that this is due to more vigorous convection at low pO2 , leading to an atmospheric moistening (Fig. 12) which causes warming analogously to . This is consistent with the increases in climate sensitivity observed – in a warmer climate the atmosphere can hold more water vapour, so any changes to water vapour will be amplified in their impacts on the radiative budget of the atmosphere. This water vapour feedback is also consistent with the weaker clear-sky shortwave radiative effect observed in 2 × Ma-CM and the temperature response observed in the Wuchiapingian simulations.
Figure 13Dominant surface type for each oxygen level simulation for (a) As-CM and (b) Wu-CM. BLT: broadleaf tree; NLT: needleleaf tree.
3.4 Response of Permian vegetation to pO2
Changes in pO2 and surface temperatures have the potential to impact the terrestrial carbon cycle by altering the competition between the oxidative and photosynthetic metabolic pathways for RuBisCO. simulated significant changes to vegetation productivity in the Permian due to changes in oxygen content. The modelled changes to vegetation in the final 50 years of the Asselian and Wuchiapingian experiments are investigated. Focusing on changes to vegetation across the Permian, the dominant vegetation fractions for As-CM35, As-CM10, Wu-CM35 and Wu-CM10 are shown in Fig. 13. For low pCO2 in the Asselian, increasing pO2 leads to a reduction in the extent of broadleaf trees and greater proliferation of grasses and shrubs. This would be consistent with increases in photorespiration at high pO2. The reverse is true in the Wuchiapingian simulations with increases in the extent of tropical broadleaf forests. It should be noted that the simulation of plant functional types is carefully tuned to present-day vegetation which was likely considerably different in the past. Therefore, caution should be exercised when extrapolating to past vegetation changes.
Figure 14As-CM${}_{\mathrm{10}}^{\mathrm{35}}$ (left) and Wu-CM${}_{\mathrm{10}}^{\mathrm{35}}$ (right) anomalies for (a) net primary productivity, (b) total carbon storage and (c) water use efficiency.
Figure 14a shows the change in net primary productivity (NPP) for As-CM${}_{\mathrm{10}}^{\mathrm{35}}$ and Wu-CM${}_{\mathrm{10}}^{\mathrm{35}}$. The Asselian simulations shows a large reduction in net primary productivity (NPP) as pO2 is increased (Fig. 14a, 59 Pg C yr−1), while the reverse is true in the Wuchiapingian simulations (+33 Pg C yr−1). At low pCO2, it is expected that competition for RuBisCO will be won out by O2 and therefore that rates of photorespiration should lead to a decline in photosynthesis. This is reflected in the gross primary productivity (GPP, 34 %) and NPP (52 %) response for the Asselian. During the Wuchiapingian, there may be sufficient CO2 that competition is much less sensitive to the pO2 so changes to NPP are much less significant. In fact, NPP is increased by 14 % (GPP +18 %). Tropical water use efficiency is also higher in Wu-CM35 (Fig. 14c), which suggests that water economy of plants could alter to adapt to a higher pO2 .
These net primary productivity changes are reflected in the total carbon storage (Fig. 14b) which is lower as pO2 is increased in As-CM (338 Pg C) and higher as pO2 is increased in Wu-CM (+379 Pg C). This is dominated by changes in the tropics (in agreement with ), where broadleaf trees cover more area in Wu-CM35. Cooler terrestrial tropical temperatures, particularly in the warm months (Fig. 4e), reduce the pO2 inhibition of RuBisCO and reduce the rate of respiration by vegetation and soils .
As these simulations are fully coupled and changes to oxygen content affect temperatures, radiation and precipitation, it is challenging to explore all the possible contributions to differences between these results and the more idealised simulations. However, there is general agreement that changes occur in the signs of the response of NPP and total carbon storage. This supports the conclusions of that high pO2 in the early Permian may have played an important role in the evolution of plants. Note that while the atmosphere and vegetation are coupled in the physical sense, the carbon cycle is not interactive (atmospheric CO2 is fixed), so determining the impacts of atmospheric pO2 on the carbon cycle remains an outstanding problem.
Figure 15The 21 %–10 % O2 anomalies for simulations. (a) Annual-mean, cold-month mean and warm-month mean surface air temperature difference. (b) Change to diurnal cycle and (c) annual-mean precipitation (mm d−1).
Figure 161-D energy balance decomposition analogous to Fig. 7 for the 21 %–10 % O2 simulations.
4 Discussion
Through its impact on atmospheric mass, oxygen content has the capacity to alter the radiative budget of the atmosphere and therefore has implications for the Earth's climate. These simulations suggest that the interactions between radiative and dynamical feedbacks lead to some consistent climatic changes in HadCM3-BL with increasing pO2:
• reduction in the seasonal cycle in surface air temperature,
• reduction in Equator-to-pole temperature gradient and
• reduction in global precipitation.
The simulations presented in here suggest that perturbations to the wind-driven ocean circulation by increasing atmospheric mass lead to warmer temperatures, particularly at high latitudes. The magnitude of the results varies depending on the precise continental configuration and background climate state. Gyre circulations vary between the pre-industrial and the Maastrichtian and Asselian case studies. Given the importance of the wind-driven ocean circulation response, this suggests that a 3-D representation of ocean circulation is necessary in order to capture the temperature response to atmospheric mass changes. It should be noted, however, that simulated higher surface temperatures for the early Earth at high atmospheric mass with a slab ocean model.
The use of 3-D oceans is now widespread in the palaeoclimate community; however, this is not widely used in the exoplanet/early Earth community (e.g. ) and for early Earth studies such as the Archean (e.g. ). While boundary conditions for these studies are sparse or in some cases non-existent the additional uncertainty associated with using a slab ocean should be considered. AOGCM studies remain the best way to assess the complex coupling between potentially competing radiative and dynamical effects.
One criticism of high oxygen variability in the Phanerozoic is the possibility of runaway fire at high oxygen content . While subsequent experiments have put this in doubt , fire is undoubtedly a negative feedback on oxygen content. However, the cooling of warmest-month temperatures over tropical and midlatitude continents in Wu-CM35 may provide somewhat of a protective mechanism against runaway fire regimes taking hold. Lightning is a major cause of palaeofire , so the reduction in convection at high pO2 would also lead to fewer lightning strikes, which would reduce fire initiation. In addition, higher fire risk could have favoured the evolution and spread of more fire-resistant species (Robinson1990).
The simulations of Permian climate (As-CM and Wu-CM) also suggest a strong role for pO2 variability in the terrestrial carbon cycle. However, there are many limitations to the modelling approach employed here. The plant functional types employed here are the same as those for the present day. In particular, C4 photosynthesis likely evolved in the Oligocene (Sage2004), although there is evidence of vegetation which causes C4-like fractionation in the Mississippian, suggesting different vegetation adaptations operating in the past (Jones1994). In addition, angiosperms did not evolve until the Cretaceous, so gymnosperms such as cycads were more widespread in the Permian . TRIFFID and other dynamic plant models were not developed with these changes in plant types in mind, so simulating past vegetation changes is still a considerable challenge. However, scientific understanding of the role of plants in the climate in the Paleozoic is still immature. While early evidence suggested that late Paleozoic vegetation was unproductive based on analysis of the closest modern relatives, this perspective is increasingly being challenged . Other approaches such as trait-based methods may be able to achieve more insights into the role of pO2 in the Earth system. We also have not accounted for changes to the ocean carbon cycle. A biogeochemical model study suggests that pervasive oceanic anoxia and euxinia only occur below an oxygen level of around 10 % , which may be below the fire threshold and therefore not of relevance to many periods in the Phanerozoic. However, the extent of oceanic anoxic events may be sensitive to atmospheric pO2 .
Figure 17(a) Reconstructed CO2 (doubling from Pleistocene values, blue) and O2 content (red) and 95 % confidence intervals (shading) from Geocarb simulations. (b) GMST reconstructed using Geocarb pCO2 and climate sensitivity values (purple) and the uncertainty in GMST from pCO2 uncertainty (purple shading). GMST reconstructed, accounting for pO2 according to global-mean temperature sensitivities (solid orange) and the uncertainty due to Geocarb pO2 (dashed orange).
Given the small changes in global-mean surface temperature (GMST, 1.5 C maximum) compared to ECS (∼3C), this raises the question of how much pO2 variability contributes to uncertainty in Phanerozoic surface temperature even with such large uncertainties in pO2 reconstructions. Figure 17 shows reconstructed Phanerozoic surface temperatures based on CO2 content and climate sensitivity from the Geocarb model (purple; ). The uncertainty associated with the 95 % confidence interval in simulated pCO2 is also indicated (purple shading). Analysis of the simulations suggests a global-mean surface temperature reduction of 0.21 C per percentage increase in O2. Accounting for the pO2 simulated by leads to a mean absolute difference in global-mean surface temperature of 0.80 C and maximum absolute difference of 2.59 C (Fig. 17 orange line). The largest deviations from the Geocarb values occur during the largest deviations from present atmospheric levels of O2 during the Permian. However, pO2 contributes little to the uncertainty in reconstruction of global-mean surface temperature compared to pCO2 (Fig. 17, dashed orange lines), even if the temperature changes simulated by are reasonable. The HadGEM3-AO and HadCM3-BL simulations show even less sensitivity of global-mean surface temperature to pO2 changes, which suggests this is likely an overestimate.
pO2 therefore remains a secondary contribution to climatic variability in the Phanerozoic in agreement with but is most likely to be important during the Permian. The Artinskian (early Permian, 283.5–290.1 Ma) is associated with a rapid increase in CO2 content from ∼500 to ∼3500 ppmv, which is associated with considerable restructuring of tropical vegetation . The results in this study suggest that pO2 variability could have modulated the climate and terrestrial vegetation response to this increase in CO2 content. suggested that Earth was close to entering a Snowball Earth in the late Carboniferous, when pO2 was higher than today. We hypothesise that the carbon cycle and physical climate feedbacks described in this paper would strongly mitigate against this. If pCO2 and pO2 are intimately linked such that cooler climates tends to increase pO2, this would suggest that pO2 responses have helped to prevent Snowball Earth initiation in the Phanerozoic.
5 Conclusions
The numerical simulations performed in this study reconcile the surface temperature response to oxygen content changes across the hierarchy of model complexity:
• Under pre-industrial Holocene conditions, increasing atmospheric pO2 leads to an increase in global-mean surface temperature in agreement with 1-D radiative–convective model simulations. This increase is greater in the cold-month mean than in the warm-month mean. The Equator-to-pole temperature gradient is reduced, particularly in the cold-month mean, consistent with a stronger greenhouse effect at high atmospheric pressure.
• Lower incident surface shortwave radiation leads to a slowdown of the hydrological cycle. Precipitation decreases globally under high pO2, with regional variations.
• The climate sensitivity is lower at high pO2, particularly in the Maastrichtian. This appears to reconcile the results of the 1-D and 3-D modelling approaches.
• The climate response simulated by is inconsistent with the radiative changes when considering a 1-D energy balance model decomposition of the surface temperature changes. Tropical cloud feedbacks alone were not sufficient to explain the discrepancy.
• The climate response to oxygen content variability is state-dependent, so it should be considered on a case-by-case basis. However, the changes are relatively small compared to the role of CO2 in the Phanerozoic .
Code and data availability
Code and data availability.
Processed model output and analysis scripts will be made available on the NERC data centre. The Met Office Unified Model is available for use under licence. Please see http://www.metoffice.gov.uk/research/modelling-systems/unified-model (last access: 27 July 2019) for more information. The ocean bathymetry and land orography reconstructions are ©Getech. Readers who would like advice on how to implement alterations to pO2 in their climate model are encouraged to contact the corresponding authors. UM users can obtain the code changes for these particular versions from the corresponding authors.
Supplement
Supplement.
Author contributions
Author contributions.
The study was performed by DCW, conceived by ATA and DCW and refined with input from PJV and the co-authors. DCW and ATA led the preparation of the manuscript, and all co-authors helped in proofreading and checking of the manuscript.
Competing interests
Competing interests.
The authors declare that they have no conflict of interest.
Acknowledgements
Acknowledgements.
This work was carried out using the computational facilities of the Advanced Computing Research Centre, University of Bristol – http://www.bris.ac.uk/acrc/ (last access: 27 July 2019). We acknowledge use of the MONSooN system, a collaborative facility supplied under the Joint Weather and Climate Research Programme, a strategic partnership between the Met Office and the Natural Environment Research Council. David C. Wade acknowledges Eric Wolff and David Stevenson for their comments on the PhD thesis of which this paper largely forms a part.
Financial support
Financial support.
This research has been supported by the NERC (grant no. DTP-1502139).
Review statement
Review statement.
This paper was edited by Yannick Donnadieu and reviewed by Jim Kasting and two anonymous referees.
References
Algeo, T. J. and Ingall, E.: Sedimentary Corg : P ratios, paleocean ventilation, and Phanerozoic atmospheric pO2, Palaeogeogr. Palaeocl., 256, 130–155, https://doi.org/10.1016/J.PALAEO.2007.02.029, 2007. a, b, c
Armour, K. C., Bitz, C. M., and Roe, G. H.: Time-Varying Climate Sensitivity from Regional Feedbacks, J. Clim., 26, 4518–4534, https://doi.org/10.1175/JCLI-D-12-00544.1, 2013. a
Arvidson, R. S., Mackenzie, F. T., and Guidry, M. W.: Geologic history of seawater: A MAGic approach to carbon chemistry and ocean ventilation, Chem. Geol., 362, 287–304, https://doi.org/10.1016/J.CHEMGEO.2013.10.012, 2013. a, b, c, d
Arakawa, A. and Lamb, V. R.: Computational Design of the Basic Dynamical Processes of the UCLA General Circulation Model, Methods in Computational Physics: Advances in Research and Applications, 17, 173–265, 1977. a, b
Banerjee, A., Archibald, A. T., Maycock, A. C., Telford, P., Abraham, N. L., Yang, X., Braesicke, P., and Pyle, J. A.: Lightning NOx, a key chemistry-climate interaction: impacts of future climate change and consequences for tropospheric oxidising capacity, Atmos. Chem. Phys., 14, 9871–9881, https://doi.org/10.5194/acp-14-9871-2014, 2014. a
Beerling, D., Lake, J., Berner, R., Hickey, L., Taylor, D., and Royer, D.: Carbon isotope evidence implying high O2∕CO2 ratios in the Permo-Carboniferous atmosphere, Geochim. Cosmochim. Ac., 66, 3757–3767, https://doi.org/10.1016/S0016-7037(02)00901-8, 2002. a
Beerling, D., Berner, R. A., Mackenzie, F. T., Harfoot, M. B., and Pyle, J. A.: Methane and the CH4-related greenhouse effect over the past 400 million years, Am. J. Sci., 309, 97–113, https://doi.org/10.2475/02.2009.01, 2009. a
Beerling, D. J. and Berner, R. A.: Impact of a Permo-Carboniferous high O2 event on the terrestrial carbon cycle, P. Natl. Acad. Sci. USA, 97, 12428–12432, https://doi.org/10.1073/pnas.220280097, 2000. a, b, c, d, e, f, g, h
Beerling, D. J., Fox, A., Stevenson, D. S., and Valdes, P. J.: Enhanced chemistry-climate feedbacks in past greenhouse worlds, P. Natl. Acad. Sci. USA, 108, 9770–9775, https://doi.org/10.1073/pnas.1102409108, 2011. a
Belcher, C. M. and McElwain, J. C.: Limits for Combustion in Low O2 Redefine Paleoatmospheric Predictions for the Mesozoic, Science, 321, 1197–200, 2008. a
Belcher, C. M., Yearsley, J. M., Hadden, R. M., McElwain, J. C., and Rein, G.: Baseline intrinsic flammability of Earth's ecosystems estimated from paleoatmospheric oxygen over the past 350 million years, P. Natl. Acad. Sci. USA, 107, 22448–22453, https://doi.org/10.1073/pnas.1011974107, 2010. a, b
Bergman, N. M., Lenton, T. M., and Watson, A. J.: COPSE: A new model of biogeochemical cycling over Phanerozoic time, Am. J. Sci., 304, 397–437, https://doi.org/10.2475/ajs.304.5.397, 2004. a, b, c, d
Berner, R. A.: Phanerozoic atmospheric oxygen: New results using the GEOCARBSULF model, Am. J. Sci., 309, 603–606, https://doi.org/10.2475/07.2009.03, 2009. a, b, c, d
Berner, R. A. and Canfield, D. E.: A new model for atmospheric oxygen over Phanerozoic time, Am. J. Sci., 289, 333–361, https://doi.org/10.2475/ajs.289.4.333, 1989. a
Berner, R. A., Vandenbrooks, J. M., and Ward, P. D.: Evolution, Oxygen and evolution, Science, 316, 557–558, https://doi.org/10.1126/science.1140273, 2007. a
Bjerknes, J.: Atlantic Air-Sea Interaction, Adv. Geophys., 10, 1–82, https://doi.org/10.1016/S0065-2687(08)60005-9, 1964. a
Bony, S., Stevens, B., Frierson, D. M. W., Jakob, C., Kageyama, M., Pincus, R., Shepherd, T. G., Sherwood, S. C., Siebesma, A. P., Sobel, A. H., Watanabe, M., and Webb, M. J.: Clouds, circulation and climate sensitivity, Nat. Geosc., 8, 261–268, https://doi.org/10.1038/ngeo2398, 2015. a
Brand, U., Posenato, R., Came, R., Affek, H., Angiolini, L., Azmy, K., and Farabegoli, E.: The end-Permian mass extinction: A rapid volcanic CO2 and CH4-climatic catastrophe, Chem. Geol., 322/323, 121–144, 2012. a
Breecker, D. O., Sharp, Z. D., and McFadden, L. D.: Atmospheric CO2 concentrations during ancient greenhouse climates were similar to those predicted for AD 2100, P. Natl. Acad. Sci. USA, 107, 576–80, https://doi.org/10.1073/pnas.0902323106, 2010. a
Broccoli, A. J., Dahl, K. A., and Stouffer, R. J.: Response of the ITCZ to Northern Hemisphere cooling, Geophys. Res. Lett., 33, 1–4, https://doi.org/10.1029/2005GL024546, 2006. a
Budyko, M. I.: The effect of solar radiation variations on the climate of the Earth, Tellus, 21, 611–619, https://doi.org/10.3402/tellusa.v21i5.10109, 1969. a
Caballero, R. and Huber, M.: State-dependent climate sensitivity in past warm climates and its implications for future climate projections, P. Natl. Acad. Sci. USA, 110, 14162–14167, https://doi.org/10.1073/pnas.1303365110, 2013. a, b
Catling, D. C. and Claire, M. W.: How Earth's atmosphere evolved to an oxic state: A status report, Earth Planet. Sc. Lett., 237, 1–20, https://doi.org/10.1016/J.EPSL.2005.06.013, 2005. a
Catling, D. C., Glein, C. R., Zahnle, K. J., and McKay, C. P.: Why O2 Is Required by Complex Life on Habitable Planets and the Concept of Planetary “Oxygenation Time”, Astrobiology, 5, 415–438, https://doi.org/10.1089/ast.2005.5.415, 2005. a
Charnay, B., Forget, F., Wordsworth, R., Leconte, J., Millour, E., Codron, F., and Spiga, A.: Exploring the faint young Sun problem and the possible climates of the Archean Earth with a 3-D GCM, J. Geophys. Res.-Atmos., 118, 10414–10431, https://doi.org/10.1002/jgrd.50808, 2013. a, b, c, d, e
Chemke, R., Kaspi, Y., and Halevy, I.: The thermodynamic effect of atmospheric mass on early Earth's temperature, Geophys. Res. Lett., 43, 11414–11422, https://doi.org/10.1002/2016GL071279, 2016. a, b
Clark, D. B., Mercado, L. M., Sitch, S., Jones, C. D., Gedney, N., Best, M. J., Pryor, M., Rooney, G. G., Essery, R. L. H., Blyth, E., Boucher, O., Harding, R. J., Huntingford, C., and Cox, P. M.: The Joint UK Land Environment Simulator (JULES), model description – Part 2: Carbon fluxes and vegetation dynamics, Geosci. Model Dev., 4, 701–722, https://doi.org/10.5194/gmd-4-701-2011, 2011. a
Clarkson, M. O., Stirling, C. H., Jenkyns, H. C., Dickson, A. J., Porcelli, D., Moy, C. M., Pogge von Strandmann, P. A. E., Cooke, I. R., and Lenton, T. M.: Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2, P. Natl. Acad. Sci. USA, 115, 2918–2923, https://doi.org/10.1073/pnas.1715278115, 2018. a
Cox, P.: A primitive equation, 3-dimensional model of the ocean, GFDL Ocean Group Technical Report No. 1, Tech. Rep., Geophysical Fluid Dynamics Laboratory, Princeton, New Jersey, 1984. a
Cox, P., Huntingford, C., and Harding, R.: A canopy conductance and photosynthesis model for use in a GCM land surface scheme, J. Hydrol., 212/213, 79–94, https://doi.org/10.1016/S0022-1694(98)00203-0, 1998. a, b
Cox, P., Betts, R. A., Jones, C., A. Spall, S., and J. Totterdell, I.: Acceleration of global warming due to carbon-cycle feedbacks in a coupled model, Nature, 408, 184–187, 2000. a
Cox, P. M., Betts, R. A., Bunton, C. B., Essery, R. L. H., Rowntree, P. R., and Smith, J.: The impact of new land surface physics on the GCM simulation of climate and climate sensitivity, Clim. Dynam., 15, 183–203, https://doi.org/10.1007/s003820050276, 1999. a
Dahl, T. W., Hammarlund, E. U., Anbar, A. D., Bond, D. P. G., Gill, B. C., Gordon, G. W., Knoll, A. H., Nielsen, A. T., Schovsbo, N. H., and Canfield, D. E.: Devonian rise in atmospheric oxygen correlated to the radiations of terrestrial plants and large predatory fish, P. Natl. Acad. Sci. USA, 107, 17911–17915, https://doi.org/10.1073/pnas.1011287107, 2010. a, b
Davies, T., Cullen, M. J. P., Malcolm, A. J., Mawson, M. H., Staniforth, A., White, A. A., and Wood, N.: A new dynamical core for the Met Office's global and regional modelling of the atmosphere, Q. J. Roy. Meteorol. Soc., 131, 1759–1782, https://doi.org/10.1256/qj.04.101, 2005. a
Dwyer, J. G., Biasutti, M., and Sobel, A. H.: Projected Changes in the Seasonal Cycle of Surface Temperature, J. Clim., 25, 6359–6374, https://doi.org/10.1175/JCLI-D-11-00741.1, 2012. a
Edwards, C. T., Saltzman, M. R., Royer, D. L., and Fike, D. A.: Oxygenation as a driver of the Great Ordovician Biodiversification Event, Nat. Geosci., 10, 925–929, https://doi.org/10.1038/s41561-017-0006-3, 2017. a
Edwards, J. M. and Slingo, A.: Studies with a flexible new radiation code, I: Choosing a configuration for a large-scale model, Q. J. Roy. Meteorol. Soc., 122, 689–719, https://doi.org/10.1002/qj.49712253107, 1996. a, b, c
Essery, R. L. H., Best, M. J., Betts, R. A., Cox, P. M., Taylor, C. M., Essery, R. L. H., Best, M. J., Betts, R. A., Cox, P. M., and Taylor, C. M.: Explicit Representation of Subgrid Heterogeneity in a GCM Land Surface Scheme, J. Hydrometeorol., 4, 530–543, https://doi.org/10.1175/1525-7541(2003)004<0530:EROSHI>2.0.CO;2, 2003. a
Falkowski, P. G., Katz, M. E., Milligan, A. J., Fennel, K., Cramer, B. S., Aubry, M. P., Berner, R. A., Novacek, M. J., and Zapol, W. M.: The Rise of Oxygen over the Past 205 Million Years and the Evolution of Large Placental Mammals, Science, 309, 1–3, 2005. a, b
Feulner, G.: The faint young Sun problem, Rev. Geophys., 50, RG2006, https://doi.org/10.1029/2011RG000375, 2012. a
Feulner, G.: Formation of most of our coal brought Earth close to global glaciation, P. Natl. Acad. Sci. USA, 114, 11333–11337, https://doi.org/10.1073/pnas.1712062114, 2017. a
Finney, D. L., Doherty, R. M., Wild, O., Stevenson, D. S., MacKenzie, I. A., and Blyth, A. M.: A projected decrease in lightning under climate change, Nat. Clim. Change, 8, 210–213, https://doi.org/10.1038/s41558-018-0072-6, 2018. a
Forster, P. M. and Shine, K. P.: Radiative forcing and temperature trends from stratospheric ozone changes, J. Geophys. Res.-Atmos., 102, 10841–10855, https://doi.org/10.1029/96JD03510, 1997. a
Franks, P. J., Royer, D. L., Beerling, D. J., Van de Water, P. K., Cantrill, D. J., Barbour, M. M., and Berry, J. A.: New constraints on atmospheric CO2 concentration for the Phanerozoic, Geophys. Res. Lett., 41, 4685–4694, 2014. a, b
Glasspool, I. J. and Scott, A. C.: Phanerozoic concentrations of atmospheric oxygen reconstructed from sedimentary charcoal, Nat. Geosci., 3, 627–630, https://doi.org/10.1038/ngeo923, 2010. a, b
Goldblatt, C.: Comment on “Long-term climate forcing by atmospheric oxygen concentrations”, Science, 353, 1–2, 2016. a, b
Goldblatt, C., Claire, M. W., Lenton, T. M., Matthews, A. J., Watson, A. J., and Zahnle, K. J.: Nitrogen-enhanced greenhouse warming on early Earth, Nat. Geosci., 2, 891–896, https://doi.org/10.1038/ngeo692, 2009. a, b, c, d
Gordon, C., Cooper, C., Senior, C. A., Banks, H., Gregory, J. M., Johns, T. C., Mitchell, J. F. B., and Wood, R. A.: The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments, Clim. Dynam., 16, 147–168, https://doi.org/10.1007/s003820050010, 2000. a
Gregory, J. M., Ingram, W. J., Palmer, M. A., Jones, G. S., Stott, P. A., Thorpe, R. B., Lowe, J. A., Johns, T. C., and Williams, K. D.: A new method for diagnosing radiative forcing and climate sensitivity, Geophys. Res. Lett., 31, L03205, https://doi.org/10.1029/2003GL018747, 2004. a, b, c, d
Hadjinicolaou, P. and Pyle, J. A.: The Impact of Arctic Ozone Depletion on Northern Middle Latitudes: Interannual Variability and Dynamical Control, J. Atmos. Chem., 47, 25–43, https://doi.org/10.1023/B:JOCH.0000012242.06578.6c, 2004. a
Hagemann, M., Weber, A. P., and Eisenhut, M.: Photorespiration: origins and metabolic integration in interacting compartments, J. Exp. Bot., 67, 2915–2918, https://doi.org/10.1093/jxb/erw178, 2016. a
Haigh, J. D. and Pyle, J. A.: Ozone perturbation experiments in a two-dimensional circulation model, Q. J. Roy. Meteorol. Soc., 108, 551–574, https://doi.org/10.1002/qj.49710845705, 1982. a
Hansen, K. W. and Wallmann, K.: Cretaceous and Cenozoic evolution of seawater composition, atmospheric O2 and CO2: A model perspective, Am. J. Sci., 303, 94–148, https://doi.org/10.2475/ajs.303.2.94, 2003. a
Harfoot, M. B. J., Beerling, D. J., Lomax, B. H., and Pyle, J. a.: A two-dimensional atmospheric chemistry modeling investigation of Earth's Phanerozoic O3 and near-surface ultraviolet radiation history, J. Geophys. Res.-Atmos., 112, D07308, https://doi.org/10.1029/2006JD007372, 2007. a, b, c
He, T., Pausas, J. G., Belcher, C. M., Schwilk, D. W., and Lamont, B. B.: Fire-adapted traits of Pinus arose in the fiery Cretaceous, New Phytol., 194, 751–759, 2012. a
Heinemann, M.: Warm and sensitive Paleocene-Eocene Climate, Ph.D. thesis, Universität Hamburg, 119 pp., 2009. a
Heinemann, M., Jungclaus, J. H., and Marotzke, J.: Warm Paleocene/Eocene climate as simulated in ECHAM5/MPI-OM, Clim. Past, 5, 785–802, https://doi.org/10.5194/cp-5-785-2009, 2009. a, b, c, d, e
Hewitt, H. T., Copsey, D., Culverwell, I. D., Harris, C. M., Hill, R. S. R., Keen, A. B., McLaren, A. J., and Hunke, E. C.: Design and implementation of the infrastructure of HadGEM3: The next-generation Met Office climate modelling system, Geosci. Model Dev., 4, 223–253, https://doi.org/10.5194/gmd-4-223-2011, 2011. a, b
Hunke, E. and Lipscomb, W.: The Los Alamos sea ice model documentation and software user's manual, Version 4.0, LA-CC-06-012., Tech. Rep., Los Alamos National Laboratory, 76 pp., 2008. a
Irvine, P. J., Kravitz, B., Lawrence, M. G., and Muri, H.: An overview of the Earth system science of solar geoengineering, Wires Clim. Change, 7, 815–833, https://doi.org/10.1002/wcc.423, 2016. a
Johns, T. C., Durman, C. F., Banks, H. T., Roberts, M. J., McLaren, A. J., Ridley, J. K., Senior, C. A., Williams, K. D., Jones, A., Rickard, G. J., Cusack, S., Ingram, W. J., Crucifix, M., Sexton, D. M. H., Joshi, M. M., Dong, B.-W., Spencer, H., Hill, R. S. R., Gregory, J. M., Keen, A. B., Pardaens, A. K., Lowe, J. A., Bodas-Salcedo, A., Stark, S., and Searl, Y.: The New Hadley Centre Climate Model (HadGEM1): Evaluation of Coupled Simulations, J. Clim., 19, 1327–1353, https://doi.org/10.1175/JCLI3712.1, 2006. a
Jones, T. P.: 13C enriched Lower Carboniferous fossil plants from Donegal, Ireland: carbon isotope constraints on taphonomy, diagenesis and palaeoenvironment, Rev. Palaeobot. Palyno., 81, 53–64, https://doi.org/10.1016/0034-6667(94)90126-0, 1994. a
Jordan, D. B. and Ogren, W. L.: The CO2/O2 specificity of ribulose 1,5-bisphosphate carboxylase/oxygenase, Planta, 161, 308–313, https://doi.org/10.1007/BF00398720, 1984. a
Kasting, J. F., Liu, S. C., and Donahue, T. M.: Oxygen levels in the prebiological atmosphere, J. Geophys. Res., 84, 3097, https://doi.org/10.1029/JC084iC06p03097, 1979. a
Kiehl, J. T. and Shields, C. A.: Sensitivity of the Palaeocene-Eocene Thermal Maximum climate to cloud properties, Philos. T. R. Soc. A, 371, 20130093, https://doi.org/10.1098/rsta.2013.0093, 2013. a
Kilic, C., Raible, C. C., and Stocker, T. F.: Multiple Climate States of Habitable Exoplanets: The Role of Obliquity and Irradiance, Astrophys. J., 844, 13 pp., https://doi.org/10.3847/1538-4357/aa7a03, 2017. a
Lenton, T. M., Crouch, M., Johnson, M., Pires, N., and Dolan, L.: First plants cooled the Ordovician, Nat. Geosci., 5, 86–89, https://doi.org/10.1038/ngeo1390, 2012. a
Li, C., von Storch, J.-S., and Marotzke, J.: Deep-ocean heat uptake and equilibrium climate response, Clim. Dynam., 40, 1071–1086, https://doi.org/10.1007/s00382-012-1350-z, 2013. a
Li, J. and Sharma, A.: Evaluation of volcanic aerosol impacts on atmospheric water vapor using CMIP3 and CMIP5 simulations, J. Geophys. Res.-Atmos., 118, 4448–4457, https://doi.org/10.1002/jgrd.50420, 2013. a
Long, S. P.: Modification of the response of photosynthetic productivity to rising temperature by atmospheric CO2 concentrations: Has its importance been underestimated?, Plant Cell Environ., 14, 729–739, https://doi.org/10.1111/j.1365-3040.1991.tb01439.x, 1991. a, b
Lu, W., Ridgwell, A., Thomas, E., Hardisty, D. S., Luo, G., Algeo, T. J., Saltzman, M. R., Gill, B. C., Shen, Y., Ling, H.-F., Edwards, C. T., Whalen, M. T., Zhou, X., Gutchess, K. M., Jin, L., Rickaby, R. E. M., Jenkyns, H. C., Lyons, T. W., Lenton, T. M., Kump, L. R., and Lu, Z.: Late inception of a resiliently oxygenated upper ocean, Science, 361, 174–177, https://doi.org/10.1126/science.aar5372, 2018. a, b
Lunt, D. J., Farnsworth, A., Loptson, C., Foster, G. L., Markwick, P., O'Brien, C. L., Pancost, R. D., Robinson, S. A., and Wrobel, N.: Palaeogeographic controls on climate and proxy interpretation, Clim. Past, 12, 1181–1198, https://doi.org/10.5194/cp-12-1181-2016, 2016. a, b, c
Madec, G.: NEMO ocean engine, Note du Pôle de modélisation, Institut Pierre-Simon Laplace (IPSL), France, No 27, ISSN No 1288-1619, 2008. a, b
Meraner, K., Mauritsen, T., and Voigt, A.: Robust increase in equilibrium climate sensitivity under global warming, Geophys. Res. Lett., 40, 5944–5948, 2013. a
Mills, B. J., Belcher, C. M., Lenton, T. M., and Newton, R. J.: A modeling case for high atmospheric oxygen concentrations during the Mesozoic and Cenozoic, Geology, 44, 1023–1026, https://doi.org/10.1130/G38231.1, 2016. a
Montañez, I. P., Tabor, N. J., Niemeier, D., Dimichele, W. A., Frank, T. D., Fielding, C. R., Isbell, J. L., Birgenheier, L. P., and Rygel, M. C.: CO2-forced climate and vegetation instability during Late Paleozoic deglaciation, Science, 315, 87–91, https://doi.org/10.1126/science.1134207, 2007. a, b
Nowack, P. J., Luke Abraham, N., Maycock, A. C., Braesicke, P., Gregory, J. M., Joshi, M. M., Osprey, A., and Pyle, J. A.: A large ozone-circulation feedback and its implications for global warming assessments, Nat. Clim. Change, 5, 41–45, https://doi.org/10.1038/nclimate2451, 2014. a, b, c
Ozaki, K. and Tajika, E.: Biogeochemical effects of atmospheric oxygen concentration, phosphorus weathering, and sea-level stand on oceanic redox chemistry: Implications for greenhouse climates, Earth Planet. Sc. Lett., 373, 129–139, https://doi.org/10.1016/J.EPSL.2013.04.029, 2013. a
Payne, R. C., Britt, A. V., Chen, H., Kasting, J. F., and Catling, D. C.: The Response of Phanerozoic Surface Temperature to Variations in Atmospheric Oxygen Concentration, J. Geophys. Res.-Atmos., 121, 10089–10096, https://doi.org/10.1002/2016JD025459, 2016. a, b, c, d, e
Pope, V. D., Gallani, M. L., Rowntree, P. R., and Stratton, R. A.: The impact of new physical parametrizations in the Hadley Centre climate model: HadAM3, Clim. Dynam., 16, 123–146, https://doi.org/10.1007/s003820050009, 2000. a
Porada, P., Lenton, T. M., Pohl, A., Weber, B., Mander, L., Donnadieu, Y., Beer, C., Pöschl, U., and Kleidon, A.: High potential for weathering and climate effects of non-vascular vegetation in the Late Ordovician, Nat. Commun., 7, 12113, https://doi.org/10.1038/ncomms12113, 2016. a
Poulsen, C. J., Tabor, C., and White, J. D.: Long-term climate forcing by atmospheric oxygen concentrations, Science, 348, 1238–41, 2015. a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v
Rasulov, B., Hüve, K., Välbe, M., Laisk, A., and Niinemets, U.: Evidence that light, carbon dioxide, and oxygen dependencies of leaf isoprene emission are driven by energy status in hybrid aspen, Plant Physiol., 151, 448–60, https://doi.org/10.1104/pp.109.141978, 2009. a
Robinson, J.: Phanerozoic O2 variation, fire, and terrestrial ecology, Palaeogeogr. Palaeocl., 75, 223–240, https://doi.org/10.1016/0031-0182(89)90178-8, 1989. a
Robinson, J. M.: Lignin, land plants, and fungi: Biological evolution affecting Phanerozoic oxygen balance, Geology, 18, 607–610, https://doi.org/10.1130/0091-7613(1990)018<0607:LLPAFB>2.3.CO;2, 1990. a, b
Rose, B. E. J. and Ferreira, D.: Ocean Heat Transport and Water Vapor Greenhouse in a Warm Equable Climate: A New Look at the Low Gradient Paradox, J. Clim., 26, 2117–2136, https://doi.org/10.1175/JCLI-D-11-00547.1, 2013. a
Royer, D., Berner, R., Montañez, I., and Tabor, N.: CO2 as a primary driver of Phanerozoic climate, GSA today, 14, 4–10, 2004. a
Royer, D. L., Donnadieu, Y., Park, J., Kowalczyk, J., and Godderis, Y.: Error analysis of CO2 and O2 estimates from the long-term geochemical model GEOCARBSULF, Am. J. Sci., 314, 1259–1283, https://doi.org/10.2475/09.2014.01, 2014. a, b, c, d
Saenko, O. A.: On the Climatic Impact of Wind Stress, J. Phys. Oceanogr., 39, 89–106, https://doi.org/10.1175/2008JPO3981.1, 2009. a
Sage, R. F.: The evolution of C4 photosynthesis, New Phytol., 161, 341–370, https://doi.org/10.1111/j.1469-8137.2004.00974.x, 2004. a
Saltzman, M. R., Young, S. A., Kump, L. R., Gill, B. C., Lyons, T. W., and Runnegar, B.: Pulse of atmospheric oxygen during the late Cambrian, P. Natl. Acad. Sci. USA, 108, 3876–81, https://doi.org/10.1073/pnas.1011836108, 2011. a
Savitzky, A. and Golay, M. J. E.: Smoothing and Differentiation of Data by Simplified Least Squares Procedures, Anal. Chem., 36, 1627–1639, https://doi.org/10.1021/ac60214a047, 1964. a
Scott, A. C. and Glasspool, I. J.: The diversification of Paleozoic fire systems and fluctuations in atmospheric oxygen concentration, P. Natl. Acad. Sci. USA, 103, 10861–10865, https://doi.org/10.1073/pnas.0604090103, 2006. a, b
Scott, A. C. and Jones, T. P.: The nature and influence of fire in Carboniferous ecosystems, Palaeogeogr. Palaeocl., 106, 91–112, https://doi.org/10.1016/0031-0182(94)90005-1, 1994. a
Sellers, W. D.: A Global Climatic Model Based on the Energy Balance of the Earth-Atmosphere System, J. Appl. Meteorol., 8, 392–400, https://doi.org/10.1175/1520-0450(1969)008<0392:AGCMBO>2.0.CO;2, 1969. a
Simmons, A. J. and Strüfing, R.: Numerical forecasts of stratospheric warming events using a model with a hybrid vertical coordinate, Q. J. Roy. Meteorol. Soc., 109, 81–111, https://doi.org/10.1002/qj.49710945905, 1983. a
Smith, B. N.: Evolution of C4 photosynthesis in response to changes in carbon and oxygen concentrations in the atmosphere through time, Biosystems, 8, 24–32, https://doi.org/10.1016/0303-2647(76)90004-6, 1976. a
Steinthorsdottir, M. and Pole, M.: Global trends of pCO2 across the Cretaceous–Paleogene boundary supported by the first Southern Hemisphere stomatal proxy-based pCO2 reconstruction, Palaeogeogr. Palaeocl., 464, 143–152, https://doi.org/10.1016/J.PALAEO.2016.04.033, 2016. a
Stolper, D. A., Bender, M. L., Dreyfus, G. B., Yan, Y., and Higgins, J. A.: A Pleistocene ice core record of atmospheric O2 concentrations, Science, 353, 1427–1430, https://doi.org/10.1126/science.aaf5445, 2016. a, b, c
Tappert, R., McKellar, R. C., Wolfe, A. P., Tappert, M. C., Ortega-Blanco, J., and Muehlenbachs, K.: Stable carbon isotopes of C3 plant resins and ambers record changes in atmospheric oxygen since the Triassic, Geochim. Cosmochim. Ac., 121, 240–262, https://doi.org/10.1016/J.GCA.2013.07.011, 2013. a
Taylor, T. N., Taylor, E. L., and Krings, M.: Paleobotany : the biology and evolution of fossil plants, Academic, 1–1252, 2009. a
Timm, S., Wittmiß, M., Gamlien, S., Ewald, R., Florian, A., Frank, M., Wirtz, M., Hell, R., Fernie, A. R., and Bauwe, H.: Mitochondrial Dihydrolipoyl Dehydrogenase Activity Shapes Photosynthesis and Photorespiration of Arabidopsis thaliana, Plant Cell, 27, 1968–84, https://doi.org/10.1105/tpc.15.00105, 2015. a
Valdes, P. J., Armstrong, E., Badger, M. P. S., Bradshaw, C. D., Bragg, F., Crucifix, M., Davies-Barnard, T., Day, J. J., Farnsworth, A., Gordon, C., Hopcroft, P. O., Kennedy, A. T., Lord, N. S., Lunt, D. J., Marzocchi, A., Parry, L. M., Pope, V., Roberts, W. H. G., Stone, E. J., Tourte, G. J. L., and Williams, J. H. T.: The BRIDGE HadCM3 family of climate models: HadCM3@Bristol v1.0, Geosci. Model Dev., 10, 3715–3743, https://doi.org/10.5194/gmd-10-3715-2017, 2017. a, b
Van Bodegom, P. M., Douma, J. C., Witte, J. P. M., Ordoñez, J. C., Bartholomeus, R. P., and Aerts, R.: Going beyond limitations of plant functional types when predicting global ecosystem-atmosphere fluxes: exploring the merits of traits-based approaches, Global Ecol. Biogeogr., 21, 625–636, https://doi.org/10.1111/j.1466-8238.2011.00717.x, 2012. a
Watson, A., Lovelock, J. E., and Margulis, L.: Methanogenesis, fires and the regulation of atmospheric oxygen, Biosystems, 10, 293–298, https://doi.org/10.1016/0303-2647(78)90012-6, 1978. a, b, c
White, A. A. and Bromley, R. A.: Dynamically consistent, quasi-hydrostatic equations for global models with a complete representation of the Coriolis force, Q. J. Roy. Meteorol. Soc., 121, 399–418, https://doi.org/10.1002/qj.49712152208, 1995. a
Wildman, R. A., Hickey, L. J., Dickinson, M. B., Berner, R. A., Robinson, J. M., Dietrich, M., Essenhigh, R. H., and Wildman, C. B.: Burning of forest materials under late Paleozoic high atmospheric oxygen levels, Geology, 32, 457–460, https://doi.org/10.1130/G20255.1, 2004. a, b, c
Williams, K., Copsey, D., Blockley, E., Bodas-Salcedo, A., Calvert, D., Comer, R., Davis, P., Graham, T., Hewitt, H., Hill, R., Hyder, P., Ineson, S., Johns, T. C., Keen, A. B., Lee, R. W., Megann, A., Milton, S. F., Rae, J. G. L., Roberts, M. J., Scaife, A. A., Schiemann, R., Storkey, D., Thorpe, L., Watterson, I. G., Walters, D. N., West, A., Wood, R. A., Woollings, T., and Xavier, P. K.: The Met Office global coupled model 3.0 and 3.1 (GC3. 0 and GC3. 1) configurations, J. Adv. Model. Earth Sy., 10, 357–380, 2018. a
Wilson, J. P., Montañez, I. P., White, J. D., DiMichele, W. A., McElwain, J. C., Poulsen, C. J., and Hren, M. T.: Dynamic Carboniferous tropical forests: new views of plant function and potential for physiological forcing of climate, New Phytol., 215, 1333–1353, https://doi.org/10.1111/nph.14700, 2017. a
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https://www.mostafaelaraby.com/paper%20review/2019/04/15/stabilizing-gans-training-using-random-projections/
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# Stabilizing GAN training With Random Projections
In this paper (Neyshabur et al. (2017)), They introduced a framework to stabilize the GAN training by using multiple projections with fixed filters of each input image to a different discriminator. Training GAN models is unstable in high dimensional space and some problems that might arise during training is the saturation of the discriminator. In that case the discriminator wins the game (diminished gradients problem).
### What are GANs ?
Generative models in general provides a way to model structure in complex distributions. They have been useful in generating data points (images, music, etc…).
Generative Adversarial Networks are generative models that creates a minimax game with 2 models discriminator and a generator. The discriminator is a simple classifier that is trying to identify real data coming from training distribution and fake data generated by the generator model.
The generator model takes a simple random noise $$z$$ sampled from a gaussian/uniform distribution (gaussian is better check ganhacks). The general objective of the minimax game of the GAN is $$min_{G}max_{D} (D,G) = \mathbb{E}_{x \mathtt{\sim} p_{data}(x)}[log D(x)] + \mathbb{E}_{z \mathtt{\sim} p_z(z)} [log(1- D(G(z)))]$$
#### General GAN problems
• Mode Collapse: when the GAN learns a specific type of images and start generating them even with different input noise values $$z$$ with no varieties of the samples
• Diminishing gradients: which is the problem this paper is trying to solver, this scenario would happen when your discriminator becomes successful at discriminating between real and fake samples with high confidence. This saturation will finish the optimization game early and the generator won’t be able to gain good gradient signals from the discriminator to learn the data distribution.
• Non-convergence: oscillation of discriminator and generator losses during the training with no convergence.
### What are random projections ?
Before starting explaining the approach proposed, on important thing to understand is the random projections.
Random projections are simply a set of random filters generated before the training and applied to input images during training creating multiple projections of the data to lower dimensional space.
These Random filters are fixed during the training that each discriminator is looking at a different low dimensional view of input datasets. The Random filters are drawn i.i.d from a gaussian distribution and scaled to have unit L2 norm.
### What’s the importance of multiple discriminator in low dimensional space?
In that case, the generator will get meaningful gradient signals from different discriminator each looking at a low dimensional set of features. The more discriminators you have from different projections the better the diversity and the quality of the generator used.
### Proposal
In this game setup, the generator is trying to fool an array of discriminators. Each discriminator on a projection of the input training image is trying to maximize his classification accuracy of real vs fake.
The generator is getting gradient signals from the array of discriminators and tries create samples that will fool all of the discriminators. $$min_{G}max_{D_{k}} \sum_{i=1}^{K} (D_k,G) = \sum_{i=1}^{K} \mathbb{E}_{x \mathtt{\sim} p_{data}(x)}[log D_k(\mathbb{W_k^T}x)] + \mathbb{E}_{z \mathtt{\sim} p_z(z)} [log(1- D_k(\mathbb{W_k^T}G(z)))]$$
### Experimental Results
In their experiment a simple DCGAN architecture was used on CelebFaces dataset. The details of the architectures along with the experiments are explained in a github notebook.
### Constructive feedback
The idea of using an ensemble of discriminators to stabilize the GAN training is interesting and showed promising results at that time. Stabilizing the GAN training in this setup comes on the expense of the following:
• To get decent results you will need more than 12 discriminators which is computationally expensive
• The filters are generated randomly and fixed throughout the training, learning the filter before training the model might give better results.
#### Side Note
I would recommend reading the paper itself and checking the related work, this is just a summary to give you a rough idea of what is going on.
### References
• Neyshabur, Behnam, Srinadh Bhojanapalli, and Ayan Chakrabarti. “Stabilizing GAN training with multiple random projections.” arXiv preprint arXiv:1705.07831 (2017).
• GAN problems article on medium
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http://www.physicsforums.com/showthread.php?t=196081
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# Concentration of ammonia in a solution
by sveioen
Tags: ammonia, concentration, solution
P: 14 Hello all, I had chemistry a long time ago, but now I am very rusty at it so I am hoping you can get me started with this problem I have; A particular solution of ammonia (Kb = 1.8 x 10-5) has a pH of 8.3. What is the concentration of ammonia in this solution? Is it the concentration of NH3 I have to find? I know I can find [OH-] since I know the pH, but what does the final equation look like? Something like $$Kb=[OH-][NH4+]/[NH3]$$? Thank you for any help!
P: 76 NH4 and OH- is going to have same amount of equilibrium concentration gained from the NH3. So If you know the pH, then how do you find the pOH, and what is the concentration of OH-? Multiply both sides by NH3 and divide bothsides by Kb. What happens?
P: 14 Ok, so pOH = 14 - pH = 14 - 8,3 = 5,7. Concentration of OH- and NH4 is therefore $$1,995 \times 10^{-6}$$? And then $$[NH3] = \frac{[OH^-][NH4^+]}{K_b}$$?
P: 76 Concentration of ammonia in a solution So plug the values and see what you get, I hope this answer agree with the true answer, does it?? If not tell me.
P: 14 I got $$2,21 \times 10^{-7}$$, which seems reasonable I guess. Maybe a bit low?!
P: 76 You don't have the answer? It should be reasonable right? because its the equilibrum concentration right?
P: 14 Nope dont have answer (yet) :(, but it seems kinda right.. Probably is equilibrum concentration..
P: 1,521
Quote by sveioen I got $$2,21 \times 10^{-7}$$, which seems reasonable I guess. Maybe a bit low?!
I got $$2,21 \times 10^{-6}$$ instead.
Related Discussions Biology, Chemistry & Other Homework 3 Biology, Chemistry & Other Homework 6 Biology, Chemistry & Other Homework 2 Biology, Chemistry & Other Homework 3 Chemistry 6
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http://apple.stackexchange.com/questions/8040/how-can-i-change-the-location-which-anki-uses-to-save-files?answertab=oldest
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# How can I change the location which Anki uses to save files?
The program Anki saves its data to the Documents folder. I would like to move this folder to my Dropbox folder. Anki has no settings which allows you to change the location that data is stored.
Is there any way to move this folder to another location and point Anki to the new folder via Mac OS X? I tried moving the folder and then creating an Alias in the same location (with the same name) by + dragging the file in Finder, but Anki doesn't see the files in the new folder.
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You may be able to use Symbolic Links to create a link between where Anki stores its files and a folder within DropBox. Information on how to create symbolic links and how they differ from Aliases can be found here:
http://hints.macworld.com/article.php?story=2001110610290643
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Thanks for the link, it worked. – Senseful Feb 9 '11 at 17:53
It worked out best when I did a symbolic link between my dropbox folder/anki/decks folder and ~/Documents/Anki Afterward had to explicitly open all decks with Anki to register. Now they all sync with dropbox. Haven't tried with a mobile device. – bgs Jul 16 '12 at 5:02
Actually, that is not the best way. You can run Anki in portable mode and specify the path to a different data folder. Create a shortcut to Anki.exe and change the target path to this:
anki.exe -b "D:\Anki"
Close Anki, move your Anki data files to D:\Anki (or whatever folder you choose) and restart Anki.
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Mac does not use drive letters, nor executable files with .exe file extensions. – tubedogg Mar 5 '15 at 4:33
When going to documents folder there is a readme with link to the user manual. That page has several ways to pick the data location. Portable mode is my pick. Standalone also looks good.
Adding the -b flag was not working until I read
On Windows, right-click on the shortcut, choose Properties, select the Shortcut tab, and add "-b \path\to\data\folder" after the path to the program…
which should leave you with something like
C:\Program Files\Anki\anki.exe" -b "C:\AnkiDataFolder"
There are options for Macintosh and flash drive too, all on that same page.
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http://www.r-bloggers.com/author-inflation-in-academic-literature/
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April 6, 2014
By
(This article was first published on Benomics » R, and kindly contributed to R-bloggers)
There seems to be a general consensus that author lists in academic articles are growing. Wikipedia says so, and I’ve also come across a published letter and short Nature article which accept this is the case and discuss ways of mitigating the issue. Recently there was an interesting discussion on academia.stackexchange on the subject but again without much quantification. Luckily given the array of literature database APIs and language bindings available, it should be pretty easy to investigate with some statistical analysis in R.
rplos
ROpenSci offers nice R language bindings for the PLOS (I’m more used to PLoS but I’ll go with it) API, called rplos. There’s no particular reason to limit the search to PLOS journals but rplos seems significantly more straightforward to work with than pubmed API packages I’ve used in the past like RISmed.
Additionally the PLOS group contains two journals of particular interest to me:
• PLOS Computational Biology — a respectable specialist journal in my field; have bioinformatics articles been particularly susceptible to author inflation?
• PLOS ONE — the original mega-journal. I wonder if the huge number of articles published here show different trends in authorship over time.
The only strange part of the search was at the PLOS API end. To search by the publication_year field you need to supply both a beginning and end date range, in the form:
publication_date:[2001-01-01T00:00:00Z TO 2013-12-31T23:59:59Z]
A tad verbose, right? I can’t imagine wanting to search for things published at a particular time of day. A full PLOS API query using the rplos package looks something like this:
searchplos(
# Query: publication date in 2012
q = 'publication_date:[2012-01-01T00:00:00Z TO 2012-12-31T23:59:59Z]',
# Fields to return: id (doi) and author list
fl = "id,author",
# Filter: only actual articles in journal PLOS ONE
fq = list("doc_type:full",
"cross_published_journal_key:PLoSONE"),
# 500 results (max 1000 per query)
start=0, limit=500, sleep=6)
A downside of using the PLOS API is that the set of journals are quite recent, PLOS ONE started in 2006 and PLOS Biology was only a few years before in 2003, so it’ll only give us a limited window into any long-term trends.
Distribution of author counts
Before looking at inflation we can compare the distribution of author counts per paper between the journals:
Possibly more usefully — but less pretty — the same data be plotted as empirical cumulative distribution functions (ECDF). From these we can see that PLOS Biology had the highest proportion of single-author papers in my sample (n = ~22,500 articles overall) followed by PLOS Medicine, with PLOS Genetics showing more high-author papers at the long-tail of the distribution, including the paper with the most authors in the sample (Couch et al., 2013 with 270 authors).
Author inflation
So, in these 6 different journals published by PLOS, how has the mean number of authors per paper varied across the past 7 years?
Above I’ve shown yearly means plus their 95% confidence intervals, as estimated by a non-parametric bootstrap method implemented in ggplot2. Generally from this graph it does look like there’s a slight upward trend on average, though arguably the mean is not the best summary statistic to use for this data, which I’ve shown is not normally distributed, and may better fit an extreme value distribution.
The relationship between publication date and number of authors per paper become clearer if it’s broken down by journal:
Here linear regression reveals a significant positive coefficient for year against mean author count per paper, as high as .52 extra authors per year on average, down to just .06 a year for PLOS ONE. Surprisingly the mega-journal which published around 80,000 papers over this time period seems least susceptible to author inflation.
The explained variance in mean number of authors per paper (per year) ranges from .28 (PLOS ONE) up to an impressive .87 for PLOS Medicine, with PLOS Computational Biology not far behind on .83. However, PLOS Computational Biology had the second lowest regression coefficient, and the lowest average number of authors of the six journals — maybe us introverted computer types should be collaborating more widely!
Journal effects
It’s interesting to speculate on what drives the observed differences in author inflation between journals. A possible covariate is the roundly-condemned “Impact Factor” journal-level metric — are “high impact” journals seeing more author creep than lesser publications?
If estimate of author inflation is plotted against respective journals’ recent impact factors, there does indeed appear to be a positive correlation. However, this comparison only has 6 data points so there’s not enough evidence to reject the null hypothesis that there is no relationship between these two variables (p = 0.18).
Conclusion
Is author inflation occurring?
Yes, it certainly appears to be on average.
Is it a problem?
I don’t know, but I’d lean towards probably not.
The average trends could be reflecting the proliferation of “Big Science” with huge collaborative consortiums like ENCODE and FANTOM (though the main papers of those examples were targeted to Nature) and doesn’t necessarily support a conclusion that Publish or Perish culture is forcing lots of token authorships and backhanders between scientists.
Maybe instead (as the original discussion hypothesised), people that traditionally may not have been credited with authorship (bioinformaticians doing end-point analysis and lab technicians) are now getting recognised for their input more often, or conceivably advances in cloud computing, distributed data storage and video conferencing has better enabled larger collaborations between scientists across the globe!
Either way, evidence for author inflation is not evidence of a problem per se :)
Caveats
• Means used for regression — while we get a surprisingly high R2 for regression the mean number of authors per paper per year, the predictive power for individual papers unsurprisingly vanishes (R2 plummets to between .02 and 4.6 × 10-4 per journal — significant non-zero coefficients remain). Author inflation wouldn’t be expected to exhibit consistent and pervasive effects in all papers, for example reviews, letters and opinion pieces presumably have consistently lower author counts than research articles and not all science can work in a collaborative, multi-author framework.
• Search limits — rplos returns a maximum of 1000 results at a time (but they can be returned sequentially using the start and limit parameters). They seem to be drawn in reverse order of time so the results here probably aren’t fully representative of the year in some cases. This has also meant my sample is unevenly split between journals: PLoSBiology: 2487; PLoSCompBiol: 3403; PLoSGenetics: 4013; PLoSMedicine: 2094; PLoSONE: 7176; PLoSPathogens:3647; Total: 22,460.
• Resolution — this could be done in a more fine-grained way, say with monthly bins. As mentioned above, for high-volume journals like PLOS ONE, the sample is likely coming from the end of the years from ~2010 onwards.
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https://halal.ninja/what-is-aaoifi
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# The AAOIFI Standard For Halal Investing
This post covers the AAOIFI standard of investing in shares, dictating what is permissible and what is not according to the standard. We'll investigate the sources behind these conclusions as well and assess their reasoning and applicability.
## What is AAOIFI?
The Accounting and Auditing Organization for Islamic Financial Institutions (AAOIFI) is an Islamic body that sets Shari’a standards for Islamic financial institutions. In essence, they draft the standards that islamic banks comply with in order to offer Islamic products to their customers.
## What does AAOIFI say about investing in stocks?
I've pulled some excerpts from the Shari’ah Standard No. (21): Financial Paper (Shares and Bonds), Pages 562 — 567, in the section titled 3. Rules for Dealing in Shares.
These describe their recommendation for how investors (both individuals and companies) should decide whether or not to invest in a company:
The fundamental rule is that of prohibition of acquiring shares of and transactions (investment and trading) in the shares of corporations that sometimes undertake transactions in Riba and other prohibited things even when their primary activity is permissible, but from this rule subscription and transactions (investment or trading) are exempted with the following conditions:
The default posture relating to investing in companies that deal with interest (which is most companies) is prohibition, but they lay out some exceptions:
3/4/1 That the corporation does not state in its memorandum of association that one of its objectives is to deal in interest, or in prohibited goods or materials like pork (swine) and the like.
3/4/2 That the collective amount raised as loan on interest – whether long-term or short-term debt – does not exceed 30% of the market capitalization of the corporation, knowingly that raising loans on interest is prohibited whatsoever the amount is.
3/4/3 That the total amount of interest-taking deposits, whether short-, medium- or long-term, shall not exceed 30% of the market capitalization of total equity, knowingly that interest- taking deposits are prohibited whatsoever the collective amount is.
3/4/4That the amount of income generated from prohibited component does not exceed 5% of the total income of the corporation irrespective of the income being generated by undertaking a prohibited activity, by ownership of a prohibited asset or in some other way. If a source of income is not properly disclosed then more effort is to be exerted for identification thereof giving due care and caution in this respect.
3/4/5 For the determination of these percentages, recourse is to be had to the last budget or verified financial position.
Further, it describes what is required of an investor in companies that engage in some interest:
3/4/6 It is obligatory to eliminate prohibited income specific to the share that is mixed up with the earnings of the corporations, and this in accordance with the following:
3/4/6/1 The elimination of prohibited income is obligatory on one who is the owner of the share, whether an investor or a trader, at the end of the financial period, even if the payment is due at the time of issuance of the final financial statements whether quarterly, annual or for other period. Accordingly, elimination is not obligatory for one who sells the shares before the end of the financial period.
3/4/6/4The figure, whose elimination is obligatory on the person dealing in shares, is arrived at by dividing the total prohibited income of the corporation whose shares are traded by the number of shares of the corporation, thus, the figure specific to each share is obtained. Thereafter the result is multiplied by the number of shares owned by the dealer – individual, institution, fund or another – and the result is what is to be eliminated as an obligation.
So, in summary, AAOIFI offers the following criteria for determining whether a stock is halal or not:
1. Interest bearing debt should not exceed 30% of market cap
2. Current interest earning assets should not exceed 30% of market cap
3. Income generated from prohibited activities should not exceed 5%
## Criticism of the AAOIFI standard
I was particularly interested in understanding what the basis was for the percentages mentioned in the previous section. An inspection of Appendix (B) The Shari’ah Basis for the Standard (Page 573) came up with this reference:
The basis for exempting trading in the shares of these corporations, whose primary activity is permissible, however, they deposit amounts and borrow on the basis of interest, is the application of the rule of removal of hardship and acknowledging of general need, widespread practice, the acknowledged principles of surplus, shortage and predominance,(5) as well as the permissibility of dealing with one the major part of whose wealth is permissible,(6) along with reliance upon the issue of separation of bargains according to some Jurists.(7) This is upheld by most fatwa issuing organisations as well as the Shari’ah Supervisory Boards of Islamic banks. (8)
Points 5 & 6 are exactly what we're after, so I went ahead and pulled up the references made there, and all of the remaining references:
(5) “Al-Furuq” by Al-Qarafi [4: 104]; “Al-Muwafaqat” [1: 37]; “Ahkam Al-Quran” by Ibn Al-Arabi [4: 1804]; and “Qawa’id Al-Ahkam Fi Masalih Al-Anam” [1: 18, 41-45].
(6) “Badai’ Al-Sanai’” [4: 104]; “Al-Ashbah Wa Al-Nazair by Ibn Nujaym (pp. 112-114); “Al-Bayan Wa Al-Tahsil” [18: 194-95]; and “Al-Manthur Fi Al-Qawa’id” [2: 335].
The original sources (cited as references) mention nothing about 30% of interest earning/bearing debt, or the 5% tolerance limit on prohibited activities.
Alot of the criticism surrounding the AAOIFI standard stems from the fact that it derives conclusions with no reference or justification explaining the basis for these conclusions.
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https://socratic.org/questions/how-many-moles-of-nacl-are-present-in-20-0-g-of-nacl
|
Chemistry
Topics
# How many moles of NaCl are present in 20.0 g of NaCl?
Apr 20, 2018
$\text{0.342 mol}$
#### Explanation:
Molar mass of $\text{NaCl = 58.4 g/mol}$
Number of moles in $\text{20.0 g NaCl}$ is
(20.0 cancel"g")/(58.4 cancel"g""/mol") = "0.342 mol"
##### Impact of this question
8111 views around the world
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http://www.chemeurope.com/en/encyclopedia/Fin_(extended_surface).html
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My watch list
my.chemeurope.com
# Fin (extended surface)
In the study of heat transfer, a fin is a surface that extends from an object to increase the rate of heat transfer to or from the environment by increasing convection. The amount of conduction, convection, or radiation of an object determines the amount of heat it transfers. Increasing the temperature difference between the object and the environment, increasing the convection heat transfer coefficient, or increasing the surface area of the object increases the heat transfer. Sometimes it is not economical or it is not feasible to change the first two options. Adding a fin to an object, however, increases the surface area and can sometimes be an economical solution to heat transfer problems.
## Simplified Case
To create a simplified equation for the heat transfer of a fin, many assumptions need to be made.
Assume:
2. Constant material properties (independent of temperature)
3. No heat transfer
4. No internal heat generation
5. One-dimensional conduction
6. Uniform cross-sectional area
7. Uniform convection across the surface area
With these assumptions, the conservation of energy can be used to create an energy balance for a differential cross section of the fin.[1]
$q_x=q_{x+dx}+dq_{conv}\,$
Fourier’s law states that
$q_x=-kA_c \left ( \frac{dT}{dx} \right )$,
where Ac is the cross-sectional area of the differential element.[2] Therefore the conduction rate at x+dx can be expressed as
$q_{x+dx}=q_x+\left ( \frac{dq_x}{dx} \right )dx$
Hence, it can also be expressed as
$q_{x+dx}=-kA_c\left ( \frac{dT}{dx} \right )-k\frac{d}{dx} \left ( A_c\frac{dT}{dx} \right )dx$.
Since the equation for heat flux is
$q''=h\left (T_s-T_\infty\right )$
then dqconv is equal to
$h*dA_s \left(T-T_\infty\right)$
where As is the surface area of the differential element. By substitution it is found that
$\frac{d^2T}{dx^2} = \left (\frac{1}{A_c}\frac{dA_c}{dx} \right )\frac{dT}{dx} - \left (\frac{1}{A_c} \frac{h}{k} \frac{dA_s}{dx} \right ) \left ( T - T_\infty \right )$
This is the general equation for convection from extended surfaces. Applying certain boundary conditions will allow this equation to simplify.
## Four Uniform Cross-sectional Area Cases
For all four cases, the above equation will simplify because the area is constant and
$\frac {dA_s}{dx} = P$
where P is the perimeter of the cross-sectional area. Thus, the general equation for convection from extended surfaces with constant cross-sectional area simplifies to
$\frac{d^2T}{dx^2}=\frac{hP}{kA_c}\left(T-T_\infty\right)$.
The solution to the simplified equation is
θ(x) = C1emx + C2emx
where $m^2=\frac{hP}{kA_c}$
and $\theta_x=T(x)-T_\infty$.
The constants C1 and C2 can be found by applying the proper boundary conditions. All four cases have the boundary condition T(x = 0) = Tb for the temperature at the base. The boundary condition at x = L, however, is different for all of them, where L is the length of the fin.
For the first case, the second boundary condition is that there is free convection at the tip. Therefore,
$hA_c\left(T(L)-T_\infty\right)=-kA_c\left.\left(\frac{dT}{dx}\right)\right\vert_{x=L}$
which simplifies to
$h\theta(L)=-k\left.\frac{d\theta}{dx}\right\vert_{x=L}$
Knowing that
$\theta_b=T_{base}-T_\infty$,
the equations can be combined to produce
$h\left(C_1e^{mL}+C_2e^{-mL}\right)=km\left(C_2e^{-mL}-C_1e^{mL}\right)$
C1 and C2 can be solved to produce the temperature distribution, which is in the table below. Then applying Fourier’s law at the base of the fin, the heat transfer rate can be found.
Similar mathematical methods can be used to find the temperature distributions and heat transfer rates for other cases. For the second case, the tip is assumed to be adiabatic or completely insulated. Therefore at x=L,
$\frac{d\theta}{dx}=0$
because heat flux is 0 at an adiabatic tip. For the third case, the temperature at the tip is held constant. Therefore the boundary condition is
θ(L) = θL. For the fourth and final case, the fin is assumed to be infinitely long. Therefore the boundary condition is
$\lim_{L\rightarrow \infty} \theta_L=0\,$.
The temperature distributions and heat transfer rates can then be found for each case.
Temperature Distribution and Heat Transfer Rate for Fins of Uniform Cross Sectional Area
Case Tip Condition (x=L) Temperature Distribution Fin Heat Transfer Rate
A Convection heat transfer $\frac{\theta}{\theta_b}=\frac{\cosh{m(L-x)}+\left(\frac{h}{mk}\right)\sinh {m(L-x)}}{\cosh{mL}+\left(\frac{h}{mk}\right)\sinh{mL}}$ $\sqrt{hPkA_c}\theta_b\frac{\sinh {mL} + (h/mk) \cosh {mL}}{\cosh {mL} + (h/mk) \sinh {mL}}$
B Adiabatic $\frac{\theta}{\theta_b}=\frac{\cosh {m(l-x)}}{\cosh {mL}}$ $\sqrt{hPkA_c}\theta_b\tanh {mL}$
C Constant Temperature $\frac{\theta}{\theta_b}=\frac{\frac{\theta_L}{\theta_b}\sinh {mx} + \sinh {m(L-x)}}{\sinh {mL}}$ $\sqrt{hPkA_c}\theta_b\frac{\cosh {mL} - frac{\theta_L}{\theta_b}}{\sinh {mL}}$
D Infinite Fin Length $\frac{\theta}{\theta_b}=e^{-mx}$ $\sqrt{hPkA_c}\theta_b$
## Fin Performance
Fin performance can be described in three different ways. The first is fin effectiveness. It is the ratio of the fin heat transfer rate to the heat transfer rate of the object if it had no fin. The formula for this is
εf = fracqfhAc,bθb,
where Ac,b is the fin cross-sectional area at the base. Fin performance can also be characterized by fin efficiency. This is the ratio of the fin heat transfer rate to the heat transfer rate of the fin if the entire fin were at the base temperature.
ηf = qfhAfθb
Af in this equation is equal to the surface area of the fin. Fin efficiency will always be less than one. This is because assuming the temperature throughout the fin is at the base temperature would increase the heat transfer rate. The third way fin performance can be described is with overall surface efficiency.
$\eta_o=\frac{q_t}{hA_t\theta_b}$,
where At is the total area and qt is the sum of the heat transfer rates of all the fins. This is the efficiency for an array of fins.
## Fin Uses
Fins are most commonly used in heat exchanging devices such as radiators in cars and heat exchangers in power plants.[3][4] They are also used in newer technology such as hydrogen fuel cells.[5] Nature has also taken advantage of the phenomena of fins. The ears of jackrabbits act as fins to release heat from the blood that flows through them.[6]
## References
• Incropera, Frank; DeWitt, David P., Bergman, Theodore L., Lavine, Adrienne S. (2007). Fundamentals of Heat and Mass Transfer, Sixth Edition, New York: John Wiley & Sons, 2-168. ISBN 0-471-45728-0.
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http://mathhelpforum.com/new-users/227108-second-derivative.html
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# Math Help - Second Derivative
1. ## Second Derivative
If the second derivative is continually increasing over the interval [-2,1] on h(x), what does that tell us about the first derivative, h'(x)? Thanks!
2. ## Re: Second Derivative
the first derivative, h'(x), will be monotonically increasing on that interval.
3. ## Re: Second Derivative
Originally Posted by state
If the second derivative is continually increasing over the interval [-2,1] on h(x), what does that tell us about the first derivative, h'(x)?
Consider the function: $h(x)=-e^{-x}$. See its plot here.
Please note that $h(x)=h''(x)$, hence the second derivative is increasing on $[-2,1]$ but what about $h'(x)=e^{-x}~?$.
4. ## Re: Second Derivative
ignore post #2. It's incorrect.
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http://mathematica.stackexchange.com/questions/56665/how-can-i-get-the-number-of-slots-in-function/56670
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# How can I get the number of slots in Function?
Suppose that I define
f = Function[#1 + #2];
And I want to define a new function, argsNum, so that it returns a number of arguments of input function:
argsNum[f]
2
since f has 2 slots, #1 and #2.
I found the good Q&A, Function that counts the number of arguments of other functions but it does not work on functions of form like Function[#1 + #2] or etc.
It works on Function[{x, y}, x + y]. But I need a function that works on slots.
How can I modify the function in above link or define a new function which also works on slots?
-
Count[f, _Slot, ∞] – m_goldberg Aug 5 at 16:13
Can you explain why you need this? For reasons that Mr. Wizard mentions in his answer, I think that such a function wouldn't be needed most of the time. But of course I might be wrong. If you explain why you need this, we might be able to give a better answer (and people would also be more interested in the question). As MrW. said, pure functions can take any number of arguments that is greater than the largest slot number. The new named slots introduced in v10 complicate this further (e.g. #one + #two &) – Szabolcs Aug 5 at 17:04
@m_goldberg What about repeated use of the same Slot? Even in the most narrow application that won't work. – Mr.Wizard Aug 5 at 17:13
@Szabolcs Actually I am making a function with one argument and that argument would be another function that I want to check. To make this explanation be simple, GoodFuncQ[func] returns true if func has exactly 2 arguments, otherwise, false. – Analysis Aug 5 at 19:41
@Analysis Thanks for the Accept. Considering your application I think it would be better to Check for error messages during application, as I suspect such tests cannot be written robustly for all possible input, at least not without unreasonable overhead. Perhaps one of the argument testing frameworks I presented here will be useful to you. – Mr.Wizard Aug 5 at 20:23
Your question is not well specified for several reasons:
1. Pure functions accept a flexible number of arguments
#1 + #2 &[a, b, c, d]
a + b
2. It is common for some arguments to not be used:
#1 + #3 & @@ {a, b, c, d}
a + c
3. SlotSequence includes all arguments after the given position:
+##3 & @@ {a, b, c, d}
c + d
Without clarifying how each of these cases is to be counted it is impossible to give a general answer.
-
+##&, seriously? Not that it doesn't amuse me, it's not something I would consider writing. (+1) – rcollyer Aug 5 at 17:56
@rcollyer It's a long-time favorite of mine. :D Actually I like it so much I wish there were more short-form operators that would work this way. (Monadic.) – Mr.Wizard Aug 5 at 18:00
Mr.Wizard, can you explain how the evaluation of (3) works? Why is + special in this respect and are there other operators which work in the same way? – sebhofer Aug 6 at 14:31
@sebhofer +x parses as Plus[x]. + is special because most Mathematica operators do not have a monadic form; I cannot write *x for Times[x] for example. I can write 1*## which parses as Times[1, ##] however. I wrote some about this here; please take a look at that before asking follow-up questions. – Mr.Wizard Aug 6 at 17:02
That makes sense. Don't know why I didn't think of that. Sorry. I only realized that *## doesn't work (and -## neither for that matter). Thanks for the link, I wasn't aware of that post. I looked for "monad" but came up empty handed. – sebhofer Aug 6 at 18:32
As @Mr.Wizard has pointed out, your question isn't well specified. However, a pure function always needs a minimum number of arguments, otherwise an error message is thrown:
#1 + #2 &[a]
Function::slotn: Slot number 2 in #1+#2& cannot be filled from (#1+#2&)[a] >>
a + #2
So finding the minimum number of required arguments of a pure function is a well-posed problem. We can solve it by simply detecting if the above error message is thrown for a given number of arguments; if so, we increase the number of arguments and try again:
EnoughArgumentsQ[f_Function, numargs_Integer] :=
Quiet[
Check[
f @@ ConstantArray[Null, numargs]; True,
False,
Function::slotn
],
Function::slotn
];
MinNumberOfArguments[f_Function] :=
NestWhile[# + 1 &, 0, ! EnoughArgumentsQ[f, #] &]
This is not a very efficient approach, but it gets the job done in a pretty robustly fashion:
MinNumberOfArguments /@ {
(* 0 *)
Function[{}, Null],
(* 1 *)
MapIndexed[#1^#2 &, #] &,
(* 2 *)
#1 + #2 &,
(* 3 *)
{#1,#2,#3,##} &,
(* 4 *)
#1 + #4 &
}
{0,1,2,3,4}
Mathematica is bound to have a cleverer internal way of determining the minimum number of arguments before it throws the Function::slotn message. If anybody knows how this is done, and if it's accessible, that'd be great :).
-
Interesting, because you used Check it even gets the pathological Map[Function[{x, y}, {#1, #2, x, y}] &, #] &. – rcollyer Aug 5 at 18:06
I'd even consider reducing possible run-time of this by first extracting Slot/SlotSequence, i.e. Cases[f, (Slot|SlotSequence)[n_]:> n, -1], and running down from n. Also, I'd use NestWhile as it returns an expression. – rcollyer Aug 5 at 18:12
@rcollyer I'm not sure what you mean with "it returns an expression", but I've changed MinNumberOfArguments to use NestWhile. Thanks for the suggestion! – Teake Nutma Aug 5 at 18:22
While, For, Do, and Scan do not have return values. NestWhile, Table, etc. do. So, your prior code where you had to write While[...]; i is not needed as you can write NestWhile[...] directly. – rcollyer Aug 5 at 19:00
Here's my approach to determine the number of slots in the pure function without counting those in any sub-functions. That means MapIndexed[#1^#2 &, #1] & (per @TeakeNutma's comment in @JohnMcGee's answer) will only return one slot. I do this by deleting all inner Functions before counting the slots:
Clear[slotCount]
slotCount[f_Function]:=Module[{deleteInner},
deleteInner=Replace[f,_Function:>Sequence[],{1,Infinity}];
]
Notes: Using Heads->True for Cases will count slots correctly for cases like #1[#2].
Testing on the example functions in @TeakeNutma's answer
{#,slotCount[#]}&/@{Function[{},Null],MapIndexed[#1^#2&,#]&,#1+#2&,{#1,#2,#3,##}&,#1+#4&}//Grid[#,Frame->All]&
I'm not quite sure #1 + #4 & would have 4 slots (instead of just 2). Below is a modified version of my slotCount function that will return 4:
Clear[slotCountPositionAware]
slotCountPositionAware[f_Function]:=Module[{deleteInner,slotList,maxSlot},
deleteInner=Replace[f,_Function:>Sequence[],{1,Infinity}];
maxSlot[l_List]:=If[l=={},0,l/.Slot[x_]:>x//Max];
maxSlot[slotList]
]
{#,slotCountPositionAware[#]}&/@{Function[{},Null],MapIndexed[#1^#2&,#]&,#1+#2&,{#1,#2,#3,##}&,#1+#4&}//Grid[#,Frame->All]&
-
This method does not like this function for input: Function[{x, y}, {#1, #2, x, y}] &. (That's a function that returns a Function.) – Mr.Wizard Aug 6 at 20:10
I've never seen mixing of named slots and hashtag(?) slots in a Function before. Isn't #1 the same thing as x and #2, y? I'm working on my function to see if it could accommodate such cases, hopefully with some success. – seismatica Aug 6 at 21:02
@Mr.Wizard I've defined another instance of slotCount to handle special functions like the one above. Let me know what you think and where I can improve: Clear[slotCount] slotCount[f:Function[Function[__]]]:= Module[{deleteInner}, deleteInner=Replace[f,_Function:>Sequence[],{2,Infinity}]//First; Cases[deleteInner,_Slot,{1,Infinity},Heads->True]~Join~First@deleteInner//Length ]; slotCount[Function[{x,y},{#1,#2,x,y}]&] – seismatica Aug 6 at 21:12
That example was borrowed from a comment by rcollyer. It is not mixing Slot and named parameters in the same Function, but rather one function nested inside another like this. The outer function using & and # contains the inner function using Function and x/y. Using the entire thing as fn, fn[1, 2] yields Function[{x, y}, {1, 2, x, y}] which is itself a complete function. – Mr.Wizard Aug 6 at 21:37
Try
Length@Union@Cases[f, _Slot, Infinity]
2
The Union eliminates duplicates
-
This doesn't work for cases like f = MapIndexed[#1^#2 &, #] &, which only has one argument. – Teake Nutma Aug 5 at 16:29
|
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|
http://mathhelpforum.com/discrete-math/277006-equivalence-classes.html
|
1. ## equivalence classes
Give the representative between 0 and 9 of the equivalence class in
Z10 that the number
-3 + 2 x 10 + 3 x10^2 + 20 - 1x 5 is a member of.
So do I make the values in the set {0,1,2,3,4,5,6,7,8,9 } and assign the equation ?
I'm not too sure how to do this any help would be appreciated thanks.
You must be very careful on your use on mathematical language.
To say that x is a number between 0 & 9 means $0<x<9$.
To say that x is a number from 0 to 9 means $0\le x\le 9$.
Which of those do you mean here?
2. ## Re: equivalence classes
Oh it's Between
3. ## Re: equivalence classes
Oh it's Between 0<x<9
4. ## Re: equivalence classes
First, do the given calculation: -3 + 2 x 10 + 3 x10^2 + 20 - 1x 5= -3+ 20+ 300+ 20- 5= 340- 8= 332. Now $\displaystyle Z_{10}$ is the set of integer modulo 10: what is the remainder when 332 is divided by 10? Without doing any arithmetic at all you should be able to see it is 2.
(Oh, $\displaystyle Z_{10}$ is not "Between 0< x< 0", it is in $\displaystyle 0\le x\le 9$.)
5. ## Re: equivalence classes
Thanks HallsofIvy been pretty busy sorry for late reply ,mid semester is getting bombarded with 500 things at once ..sigh
cheers
|
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https://nips.cc/Conferences/2022/ScheduleMultitrack?event=55137
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Timezone: »
Poster
Your Transformer May Not be as Powerful as You Expect
Shengjie Luo · Shanda Li · Shuxin Zheng · Tie-Yan Liu · Liwei Wang · Di He
Thu Dec 01 09:00 AM -- 11:00 AM (PST) @ Hall J #219
Relative Positional Encoding (RPE), which encodes the relative distance between any pair of tokens, is one of the most successful modifications to the original Transformer. As far as we know, theoretical understanding of the RPE-based Transformers is largely unexplored. In this work, we mathematically analyze the power of RPE-based Transformers regarding whether the model is capable of approximating any continuous sequence-to-sequence functions. One may naturally assume the answer is in the affirmative---RPE-based Transformers are universal function approximators. However, we present a negative result by showing there exist continuous sequence-to-sequence functions that RPE-based Transformers cannot approximate no matter how deep and wide the neural network is. One key reason lies in that most RPEs are placed in the softmax attention that always generates a right stochastic matrix. This restricts the network from capturing positional information in the RPEs and limits its capacity. To overcome the problem and make the model more powerful, we first present sufficient conditions for RPE-based Transformers to achieve universal function approximation. With the theoretical guidance, we develop a novel attention module, called Universal RPE-based (URPE) Attention, which satisfies the conditions. Therefore, the corresponding URPE-based Transformers become universal function approximators. Extensive experiments covering typical architectures and tasks demonstrate that our model is parameter-efficient and can achieve superior performance to strong baselines in a wide range of applications. The code will be made publicly available at https://github.com/lsj2408/URPE.
|
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http://cpr-astrophsr.blogspot.com/2013/01/13013813-andrew-j-steffl-et-al.html
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## Cassini UVIS observations of the Io plasma torus. II. Radial variations [PDF]
Andrew J. Steffl, Fran Bagenal, A. Ian F. Stewart
On January 14, 2001, shortly after the Cassini spacecraft's closest approach to Jupiter, the Ultraviolet Imaging Spectrometer (UVIS) made a radial scan through the midnight sector of Io plasma torus. The Io torus has not been previously observed at this local time. The UVIS data consist of 2-D spectrally dispersed images of the Io plasma torus in the wavelength range of 561{\AA}-1912{\AA}. We developed a spectral emissions model that incorporates the latest atomic physics data contained in the CHIANTI database in order to derive the composition of the torus plasma as a function of radial distance. Electron temperatures derived from the UVIS torus spectra are generally less than those observed during the Voyager era. We find the torus ion composition derived from the UVIS spectra to be significantly different from the composition during the Voyager era. Notably, the torus contains substantially less oxygen, with a total oxygen-to-sulfur ion ratio of 0.9. The average ion charge state has increased to 1.7. We detect S V in the Io torus at the 3{\sigma} level. S V has a mixing ratio of 0.5%. The spectral emission model used in can approximate the effects of a non-thermal distribution of electrons. The ion composition derived using a kappa distribution of electrons is identical to that derived using a Maxwellian electron distribution; however, the kappa distribution model requires a higher electron column density to match the observed brightness of the spectra. The derived value of the kappa parameter decreases with radial distance and is consistent with the value of {\kappa}=2.4 at 8 RJ derived by the Ulysses URAP instrument (Meyer-Vernet et al., 1995). The observed radial profile of electron column density is consistent with a flux tube content, NL^2, that is proportional to r^-2.
View original: http://arxiv.org/abs/1301.3813
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https://iwaponline.com/jwh/article-abstract/doi/10.2166/wh.2019.103/71710/Monitoring-hospital-wastewaters-for-their-probable
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## Abstract
Hospitals' effluents contain a considerable amount of chemicals. Considering the significant volume of wastewater discharged by hospitals, the presence of these chemicals represents a real threat to the environment and human health. Thus, the aim of this study was to evaluate the in vivo and in vitro genotoxicities of three wastewater effluents collected from Tunisian hospitals. The liver of Swiss albino male mice, previously treated with different doses of the hospital wastewaters, was used as a model to detect DNA fragmentation. Our results showed all the hospital effluents caused significant qualitative and quantitative hazards in hepatic DNA. The wastewater collected from Sfax hospital exhibited the highest genotoxic effect, which may be explained by the presence in this effluent of some toxic micropolluants. There was a significant increase in genotoxicity, proportionally to the concentration of effluent. However, the vitotox assay did not show any significant genotoxicity on Salmonella typhimurium TA104 in the presence or absence of microsomal fraction S9. The ratio gentox/cytox was lower than the threshold 1.5. This study assessed the toxicological risk issued from Tunisian hospital wastewaters, which is potentially very harmful, and it has been pointed out that wastewater treatment requires special attention.
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https://www.missingdata.nl/missing-data/missing-data-methods/imputation-methods/
|
# Single imputation methods
Single imputation denotes that the missing value is replaced by a value. In this method the sample size is retrieved. However, the imputed values are assumed to be the real values that would have been observed when the data would have been complete. When we have missing data, this is never the case. We can never be completely certain about imputed values. Therefore this missing data uncertaintly should be incorporated as is done in multiple imputation
## Mean imputation
Mean imputation is a method in which the missing value on a certain variable is replaced by the mean of the available cases. This method maintains the sample size and is easy to use, but the variability in the data is reduced, so the standard deviations and the variance estimates tend to be underestimated. The magnitude of the covariances and correlation also decreases by restricting the variability and this method often causes biased estimates, irrespective of the underlying missing data mechanism (Enders, 2010; Eekhout et al, 2013). In the example below you can see the relation between x and y when the mean value is imputed for the missing values on y.
For missings on multi-item questionnaires, mean imputation can be applied at the item level. One option is to impute the missing item scores with the item mean for each item. In that case the average of the respondents with observed scores for each item is computed and that average value is imputed for respondents with a missing score. Another option is to impute the person mean. In that method the average of the observed item scores for each respondent is computed and that average is imputed for the item scores that are missing for that respondent. This option is also called average of the available items. Both these methods result in biased analysis results, especially when missing data are not MCAR (Eekhout et al. 2013). Nevertheless, these methods are often advised in questionnaire manuals.
Another method, that combines item mean imputation and person mean imputation is two-way imputation. In this method the imputed value is calculated by adding the person mean to the item mean and subtract the overall mean from that score (van Ginkel et al. 2010).
## Regression imputation
In single regression imputation the imputed value is predicted from a regression equation. For this method the information in the complete observations is used to predict the values of the missing observations. Regression assumes that the imputed values fall directly on a regression line with a nonzero slope, so it implies a correlation of 1 between the predictors and the missing outcome variable. Opposing the mean substitution method, regression imputation will overestimate the correlations, however, the variances and covariances are underestimated.
Stochastic regression imputation aims to reduce the bias by an extra step of augmenting each predicted score with a residual term. This residual term is normally distributed with a mean of zero and a variance equal to the residual variance from the regression of the predictor on the outcome. As you can see in the video below, the error that is added to the predicted value from the regression equation is drawn from a normal distribution. This way the variability in the data is preserved and parameter estimates are unbiased with MAR data. However, the standard error tends to be underestimated, because the uncertainty about the imputed values is not included, which increases the risk of type I errors (Enders, 2010).
## Matching methods
Hot-deck imputation is a technique where non-respondents are matched to resembling respondents and the missing value is imputed with the score of that similar respondent (Roth, 1994). Two hot-deck approaches are the distance function approach and the pattern matching approach. The distance function approach, or nearest neighbor approach, imputes the missing value with the score of the case with the smallest squared distance statistic to the case with the missing value. The matching pattern method is more common, where the sample is stratified in separate homogenous groups. The imputed value for the missing case is randomly drawn from cases in the same group (Fox-Wasylyshyn & El-Masri, 2005). Hot-deck imputation replaces the missing data by realistic scores that preserve the variable distribution. However it underestimates the standard errors and the variability (Roth, 1994). Hot-deck imputation is especially common in survey research (Little & Rubin, 2002).
## Last observation caried forward
The last value carried forward method is specific to longitudinal designs. This technique imputes the missing value with the last observation of the individual. This method makes the assumption that the observation of the individual has not changed at all since the last measured observation, which is mostly unrealistic (Wood, White & Thompson, 2004).
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http://math.stackexchange.com/users/12932/junyan-xu
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# Junyan Xu
less info
reputation
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bio website location China age 22 member for 1 year, 10 months seen May 13 at 4:23 profile views 18
PhD student in Mathematics @ Indiana University Bloomington
5 Proof of recursive formula for “fusible numbers” 0 A non-noetherian ring with $\text{Spec}(R)$ noetherian
# 56 Reputation
+50 Proof of recursive formula for “fusible numbers” +5 Proof of Gauss's lemma in Riemannian geometry
# 1 Question
1 Proof of Gauss's lemma in Riemannian geometry
# 5 Tags
5 recreational-mathematics 0 differential-geometry 5 elementary-number-theory 0 riemannian-geometry 0 commutative-algebra
# 21 Accounts
Mathematics 56 rep 14 Area 51 51 rep 2 TeX - LaTeX 28 rep 3 Stack Overflow 1 rep Super User 1 rep
Necromancer Teacher Student Editor Supporter
# 0 Active bounties
This user has no active bounties
all time by type
15 up 7 question
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https://www.earthdoc.org/content/papers/10.3997/2214-4609.201410855
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1887
PDF
• # f Transformation of transient decays to continuous apparent resistivity curves, a generalized apparent resistivity definition
• By L. Söres
• Publisher: European Association of Geoscientists & Engineers
• Source: Conference Proceedings, 53rd EAEG Meeting, May 1991, cp-42-00112
• ISBN: 978-90-73781-03-0
• DOI:
### Abstract
In the interpretation of electromagnetic methods a very simple way of getting rid of the geometric and primary field effects is transforming measured data to apparent resistivities. The main principle for this transformation is generally to determine the resistivity of the substituting homogeneous halfspace.
/content/papers/10.3997/2214-4609.201410855
1991-05-28
2022-08-11
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http://etna.mcs.kent.edu/volumes/2001-2010/vol30/abstract.php?vol=30&pages=278-290
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## New quadrature rules for Bernstein measures on the interval [-1,1]
Elías Berriochoa, Alicia Cachafeiro, José M. García-Amor, and Francisco Marcellán
### Abstract
In the present paper, we obtain quadrature rules for Bernstein measures on $[-1,1]$, having a fixed number of nodes and weights such that they exactly integrate functions in the linear space of polynomials with real coefficients.
Full Text (PDF) [210 KB]
### Key words
quadrature rules, orthogonal polynomials, measures on the real line, Bernstein measures, Chebyshev polynomials
33C47, 42C05
< Back
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https://www.usgs.gov/center-news/volcano-watch-eruption-makes-spectacular-entry-sea
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# Volcano Watch — Eruption makes spectacular entry into sea
Release Date:
The eruption on Kīlauea's East Rift Zone continues with lava flowing into the sea at Kamoamoa. Lava is fed to the ocean in underground tubes from two erupting vents on the south and west sides of the Puu Oo cone.
Eruption makes spectacular entry into sea
(Public domain.)
The eruption on Kīlauea's East Rift Zone continues with lava flowing into the sea at Kamoamoa. Lava is fed to the ocean in underground tubes from two erupting vents on the south and west sides of the Puu Oo cone. The lava pond inside Puu Oo remains at about the same level, roughly 265 feet below the lowest point on the rim of the cone. The pond was sluggish, with slow surface circulation from west to east and low-level spattering against the east wall.
A large new crack that forms a notch in the rim of the cone and extends downslope towards the collapse pits, which are up-slope from the episode 51 vent area, has appeared on the west slope of Puu Oo. Both the episode 51 and 53 vents are actively feeding lava into the tube system that carries lava to the sea, but both vents are crusted over, and no lava is visible. The crater in Puu Oo, each of the episode 51 and 53 vent areas, and the two collapse pits on the flank of Puu Oo emit large amounts of volcanic fume, consisting mainly of water vapor and sulfur dioxide gas. In addition, large columns of fume are also emitted from several skylights in the tube system near the vents.
Starting August 21 and continuing through much of the week, the lava entries into the ocean were quite spectacular, although also quite dangerous. Several large lava benches slid into the ocean during the week. The largest occurred on August 21 and measured about 200 feet long and 30 feet wide. After the lava bench slid away, the activity at the coast increased, with small steam explosions that threw angular blocks of incandescent lava onto the lava delta. Lava fountains reached to 150 feet high, and many lava bubbles were formed above a skylight just inland from the ocean entry point. The lava bubbles expanded to about 30 feet in diameter before exploding into thin sheets of transparent brown-colored glass. This activity settled down by Wednesday, and the eruption has been much less spectacular since then.
Starting the evening of August 22 and continuing through August 26, we recorded a series of small, deep earthquakes beneath the summit of Kīlauea. On the 24th, about 280 events occurred in a 24-hour period. This type of earthquake is caused by movement of magma rather than by the breaking of rock; we think they are caused by replenishment of magma from below into the summit magma chamber. However, the summit region has not yet shown any inflation due to the addition of this new magma from depth. Previous swarms of these small, deep earthquakes have been followed, within a few weeks, by increases in eruptive activity.
On Thursday evening at 5:38 p.m., a magnitude 3.0 earthquake shook the summit region of Kīlauea. The epicenter was located a few miles southeast of Halemaumau. This earthquake may be indirectly related to the swarm of deep earthquakes beneath Kīlauea that took place this past week.
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http://en.wikipedia.org/wiki/Science_of_Value
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Science of value
(Redirected from Science of Value)
The science of value, or value science, is a creation of philosopher Robert S. Hartman, which attempts to formally elucidate value theory using both formal and symbolic logic.
Fundamentals
The fundamental principle, which functions as an axiom, and can be stated in symbolic logic, is that a thing is good insofar as it exemplifies its concept. This means, according to Hartman, that the good thing has a name, that the name has a meaning defined by a set of properties, and that the thing possesses all of the properties in the set. A thing is bad if it does not fulfill its definition. A car, by definition, has brakes. A car which accelerates when the brakes are applied is a bad car, since a car by definition must have brakes. A horse, if we called it a car, would be an even worse car, with fewer of the properties of a car.
He introduces three basic dimensions of value, systemic, extrinsic and intrinsic for sets of properties—perfection is to systemic value what goodness is to extrinsic value and what uniqueness is to intrinsic value—each with their own cardinality: finite, $\aleph_0$ and $\aleph_1$. In practice, the terms "good" and "bad" apply to finite sets of properties, since this is the only case where there is a ratio between the total number of desired properties and the number of such properties possessed by some object being valued. (In the case where the number of properties is countably infinite, the extrinsic dimension of value, the exposition as well as the mere definition of a specific concept is taken into consideration.)
Hartman quantifies this notion by the principle that each property of the thing is worth as much as each other property, depending on the level of abstraction. [1] Hence, if a thing has n properties, each of them—if on the same level of abstraction—is proportionally worth n-1. . In other words, a car having brakes or having a gas cap are weighted equally so far as their value goes, so long as both are a part of one's definition of a "car." Since a gas cap is not normally a part of a car's definition, it would be given no weight. Headlights could be weighed twice, once or not at all depending on how headlights appear in the description of a car. Given a finite set of n properties, a thing is good if it is perceived to have all of the properties, fair if it has more than n/2 of them, average if n/2 of them, and bad if it has fewer than n/2.
Infinite sets of properties
Hartman goes on to consider infinite sets of properties. Hartman claims that according to a theorem of transfinite mathematics, any collection of material objects is at most denumerably infinite. [2] This is not, in fact, a theorem of mathematics. But, according to Hartman, people are capable of a denumerably infinite set of predicates, intended in as many ways, which he gives as $\aleph_1$. As this yields a notional cardinality of the continuum, Hartman advises that when setting out to describe a person, a continuum of properties would be most fitting and appropriate to bear in mind. This is the cardinality of intrinsic value in Hartman's system.
Although they play no role in ordinary mathematics, Hartman deploys the notion of aleph number reciprocals, as a sort of infinitesimal proportion. This, he contends goes to zero in the limit as the uncountable cardinals become larger. In Hartman's calculus, for example, the assurance in a Dear John letter, that "we will always be friends" has axiological value $\frac{_1}{\aleph_2}$, whereas taking a metaphor literally would be slightly preferable, the reification having a value of $\frac{_1}{\aleph_1}$.
Evaluation of Hartman's work
Hartman invented the Hartman Value Profile, which is however not a description of what is valuable, but a test to determine what people regard as valuable. It measures concept-formation and decision-making capacity. A Hartman festschrift (Values and Valuation) appeared a few years after his death. Some critics would claim that most of the articles in it are not by Hartman supporters. Hartman, some critics claim, is out of the mainstream of value philosophy, but he was asked by UNESCO to summarize the state of Value Theory at Mid-Century. Many would dispute the idea that the number of properties of a thing can in any meaningful way be enumerated, but this is something Hartman never said was necessary. A standard argument against enumeration is that new properties can be defined in terms of old ones. Adding more features, a critic could object, even if each seems to be a good one, can sometimes lead to the overall value going down. In this way we get over-engineered software or a remote control which has too many buttons on it. Hartman holds that "the name (that one puts on a concept) sets the norm" so he would rejoin that a "Remote with too many buttons" is a disvalue.
From a mathematician's point of view, much of Hartman's work in The Structure of Value is rather novel and does not use conventional mathematical methodology, nor axiomatic reasoning. However he later employed the mathematics of topological compact, connected Hausdorff spaces, interpreting them as a model for the value-structure of metaphor, in a paper on Aesthetics.
Hartman, following Georg Cantor, uses infinite cardinalities. As a stipulated definition, he posits the reciprocals of transfinite cardinal numbers. These, together with the algebraic laws of exponents, enables him to construct what is today known as The Calculus of Values. In his paper "The Measurement of Value," Hartman explain how he calculates the value of such items as Christmas shopping in terms of this calculus. While inverses of infinite quantities (infinitesimals) exist in certain systems of numbers, such as hyperreal numbers and surreal numbers, these are not reciprocals of cardinal numbers.
Hartman supporters maintain that it is not necessary for properties to be actually enumerated, only that they exist and can correspond bijectively (one-to-one) to the property-names comprising the meaning of the concept. The attributes in the meaning of a concept only "consist" as stipulations; they don't exist. Questions regarding the existence of a concept belong to ontology.
Intensional attributes can resemble, but are not identical to, the properties perceived by the five senses. Attributes are names of properties. When, even partially, the properties of a thing match the attributes of that thing in the mind of the one making the judgment, the thing will be said to have "value". When they completely correspond, the thing will be called "good". These are basic ideas in value science.
Notes
1. ^ The Structure of Value, page 204
2. ^ The Structure of Value, page 117
References
• Davis, John William, ed, Value and Valuation: Axiological Studies in Honor of Robert S. Hartman, The University of Tennessee Press, 1972
• Hartman, Robert S., The Structure of Value: Foundations of Scientific Axiology, Southern Illinois University Press, 1967
• Hartman, Robert S., "Application of the Science of Axiology," Ch. IX in Rem B. Edwards and John W. Davis, eds., Forms of Value and Valuation: Theory and Applications. Lanham, Md., University Press of America, 1991
• Hartman, Robert S., Freedom to Live, (Arthur R. Ellis, editor), Atlanta: Rodopi Editions, Value Inquiry Book Series, 1984, reissued 1994
• Hartman, Robert S., "Axiometric Structure of Intrinsic Value", Journal of Value Inquiry (Summer, 1974; v.8, no. 2, pp. 88-101
• Katz, Marvin C., Sciences of Man and Social Ethics, Boston, 1969, esp. pp. 9-45, 101-123.
• Katz, Marvin C., Trends Towards Synthesis in the Philosophy of Robert S. Hartman, Muskegon: Axiopress (142 pages 2004).
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http://strangesounds.org/2015/05/unexplained-alien-sounds-recorded-at-the-edge-of-space-22-miles-earth-surface-baffle-scientists.html
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# Unexplained alien sounds recorded at the edge of space 22 miles from Earth’s surface baffle scientists
## These new eerie ‘alien sounds’ have been recorded 22 MILES above Earth by NASA.
### This new sound recording from the edge of space has unexplained hisses and whistles that puzzle scientists!
This is the first time in 50 years that eerie sounds from the edge of space have been recorded aboard a NASA student balloon experiment and that at 22 miles (36 kilometers) above the Earth’s surface.
The mysterious infrasound hisses and whistles are baffling the scientific community:
Several hypothesis exist for the origin of these ‘alien sounds‘:
• Signals from a wind farm under the balloon’s flight path
• Crashing ocean waves
• Wind turbulence
• Gravity waves
• Clear air turbulence
• Vibrations caused by the balloon cable.
Storms, earthquakes, volcanoes, avalanches and meteors all produce infrasonic sound waves, which carry for long distances. Infrasound is below human hearing range, but speeding up the recordings makes them audible.
I find that this weird signal is really complex and kind of creepy!
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https://www.tripadvisor.com.tw/Hotel_Review-g187895-d229073-Reviews-or20-Bernini_Palace_Hotel-Florence_Tuscany.html
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Windows: Internet Explorer, Mozilla Firefox, Google Chrome. Mac: Safari.
# 伯尼尼宮酒店 (佛羅倫斯) Bernini Palace Hotel
1,270 則評論
• 很棒71%
• 非常好22%
• 一般4%
• 2%
• 糟透了1%
5 星級飯店
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444 筆結果
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87
17
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375
87
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21 - 25 則評論，共 444
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US\$358 - US\$1,098 (根據標準客房的平均房價)
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https://cran.csiro.au/web/packages/onemap/vignettes/Introduction_R.html
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# Introduction to R
#### 2022-02-10
R is a language and environment for statistical computing and graphics. To download R, please visit the Comprehensive R Archive Network. You do not need to be an expert on it to be able to build your linkage map using OneMap.
Although we prefer and recommend the Linux version, in this tutorial it is assumed that the user is running Windows. Users of R under Linux or Mac OS should have no difficulty following this tutorial.
We would like to recommend those new users, instead of using plain R, use it through the fantastic software RStudio. With this package, there is no noticeable difference between operating systems.
As advertised on the website, RStudio is an integrated development environment (IDE) for R. It includes a console, syntax-highlighting editor that supports direct code execution, as well as tools for plotting, history, debugging, and workspace management. In other words, it offers a number of facilities for your convenience that will make your life easier, especially if you have never used R before.
So, go ahead and download and install R and RStudio. The window on the left is where you type the R commands you want.
# Getting started
In the left window, you can see a greater than sign (>’’), which means that R is waiting for a command. We call this a prompt.
Let us start with a simple example of adding two numbers. Type 2 + 3 at the prompt then type the Enter key. You will see the result directly on the screen.
2 + 3
#> [1] 5
You can store this result into a variable for future use, applying the assignment operator _ <- _ (less than sign and _ minus_ altogether):
x <- 2 + 3
The result of the calculation was stored into the variable x. You can access this result by typing x at the prompt:
x
#> [1] 5
You can also use the variable x in other calculations. For example:
x + 4
#> [1] 9
So, play a little just to start understanding what is going on.
# Functions
Another fundamental aspect in R is the usage of functions. A function is a predefined routine used to do specific calculations. For example, to calculate the natural logarithm of $$6.7$$, we can use the function log:
log(6.7)
#> [1] 1.902108
The function log contains a group of internal procedures to calculate the natural logarithm of a positive real number. The input values of a function are called arguments.
In the previous example, we provided only one argument ($$6.7$$) to the function. Sometimes a function has more than one argument. For example, to obtain the logarithm of $$6.7$$ to base $$4$$, you can use:
log(6.7, base = 4)
#> [1] 1.372081
It is possible to calculate the natural logarithm of a set of numbers by defining a vector and using it as the first argument of the function log. To do so we use the function c(), that combines a set of values into a vector. Thus, to calculate the logarithm of the numbers 6.7, 3.2, 5.4, 8.1, 4.9, 9.7, and 2.5, one can use:
y <- c(6.7, 3.2, 5.4, 8.1, 4.9, 9.7, 2.5)
log(y)
#> [1] 1.9021075 1.1631508 1.6863990 2.0918641 1.5892352 2.2721259 0.9162907
Notice that y is a vector, that is the argument to the function log().
# Getting help
Every R function has a help page that can be accessed using a question mark before the name of the function. For example, to get help on function log, you would type:
?log
This command will open a help page in the default web browser of your system. The help page contains some important information about the function such as its syntax, its arguments, and some usage examples.
There are many other ways of getting help, of course. For example, from RStudio, click Help on the menu. For doing searches on the internet, it is better to first go to https://rseek.org/, since R is a very common letter to include in searches.
# Packages
Although R has a huge amount of internal functions, for doing very specific computations (like constructing genetic linkage maps), it is necessary to add extra functionalities. These can be done by installing a package (that, loosely speaking, will include a number of new functions for helping you to achieve what you are trying to do). A package is a collection of related functions, help files and example data files that have been bundled together (Adler, 2010).
For example, let us assume that you need to convert a set of recombination fractions into centimorgan distance using the Kosambi mapping function. One possible way to do this is by using basic R to write a function to calculate the distances. Another way is to use the OneMap package. To install it you can type:
setRepositories(ind = 1:2)
install.packages("onemap")
You also can use the console menus on RStudio. On the bottom window to the right, select Packages, then Install, and finally select OneMap (select CRAN as your repository). Yes, it is that easy!
Returning to the console, you need to load OneMap by typing:
library(onemap)
Some Linux users reported the error message below:
ERROR: dependency ‘tkrplot’ is not available for package ‘onemap’
To fix it, in a terminal (outside R), install r-cran-tkrplot:
sudo apt-get install r-cran-tkrplot
To finish our example, let us enter some recombination fractions, for example, 0.01, 0.12, 0.05, 0.11, 0.21, 0.07, and save it into a variable named rf:
rf <- c(0.01, 0.12, 0.05, 0.11, 0.21, 0.07)
Now, let us use OneMap’s function kosambi to do the calculation:
kosambi(rf)
#> [1] 1.000133 12.238706 5.016767 11.182805 22.384601 7.046279
You can also obtain help on the function kosambi using the question mark in the same way as done before:
?kosambi
# Importing and exporting data
So far, we have entered the variables in R by typing them directly into the console. However, in real situations, we usually read these values from a file or a data bank (including files on the internet).
To learn this procedure, copy and paste the following table into a text editor (for example, notepad) and save it to a file called test.txt into any directory in your computer (such as My Documents).
x y
2.13 4.50
4.48 1.98
10.95 9.29
10.03 16.25
12.72 27.38
24.63 22.60
22.57 36.87
29.78 31.73
19.54 10.42
7.86 14.68
11.75 8.68
23.71 37.39
To read these data set into R, first, you have to set the working directory. Go to Session, then Set Working Directory, and Choose Directory, pointing to where you saved the file test.txt.
Now let us read the file test.txt into R and store it in a variable named dat. To do this, we can use using the R function read.table. The first argument is the name of the file; the second one indicates if the file contains a header, that is, if the first line of the file contains the names of the variables (which is true for our example):
dat <- read.table(file = "test.txt", header = TRUE)
dat
The second line, with dat, is necessary to ask R to print the contents of the object dat (i. e., the data itself). Inspecting the object dat you can see a table with 12 rows and two columns. The names of the columns are x and y. We can access the variables in columns using the dollar sign followed by the column name:
dat$x #> [1] 2.13 4.48 10.95 10.03 12.72 24.63 22.57 29.78 19.54 7.86 11.75 23.71 dat$y
#> [1] 4.50 1.98 9.29 16.25 27.38 22.60 36.87 31.73 10.42 14.68 8.68 37.39
It is also possible to use the function summary to extract some information about the object dat, or about each one of the columns separately:
summary(dat)
#> x y
#> Min. : 2.130 Min. : 1.980
#> 1st Qu.: 9.488 1st Qu.: 9.137
#> Median :12.235 Median :15.465
#> Mean :15.012 Mean :18.481
#> 3rd Qu.:22.855 3rd Qu.:28.468
#> Max. :29.780 Max. :37.390
summary(dat$x) #> Min. 1st Qu. Median Mean 3rd Qu. Max. #> 2.130 9.488 12.235 15.012 22.855 29.780 summary(dat$y)
#> Min. 1st Qu. Median Mean 3rd Qu. Max.
#> 1.980 9.137 15.465 18.481 28.468 37.390
The function summary provides some descriptive statistics about the variables in the dataset. If you want to export this information to a file you can use the function write.table:
write.table(x = summary(dat), file = "test_sum.txt", quote = FALSE)
The first argument is the output of the summary function. Note that is possible to use a function as an argument of another one. The second argument is the name of the file in which the summary will be written. Notice that this will happen in the working directory, previously set through RStudio menus. The third argument eliminates double quotes from the output file. After running the command, you can look for the file test_sum.txt in the working directory you defined before.
# Classes and methods
In R, every object belongs to a class. This is a simple concept that you must remember. For example, the dat object mentioned above belongs to class data.frame. We can obtain this information using the function class:
class(dat)
#> [1] "data.frame"
When we used the function summary, it automatically recognized the class of the object dat and applied a specific procedure developed for class data.frame, which in this case involves the computation of some descriptive statistics.
This procedure is named method. However, other classes of objects can be used as arguments to function summary and the result will be different!
For example, let us adjust a linear (regression) model using column y as the response variable, and column x as the independent one. This can be done with the function lm():
ft_mod <- lm(dat$y ~ dat$x)
ft_mod
#>
#> Call:
#> lm(formula = dat$y ~ dat$x)
#>
#> Coefficients:
#> (Intercept) dat$x #> 1.803 1.111 This function is used to fit linear models and, by default, prints just a formula and the coefficients of the linear regression. Object ft_mod is of class lm: class(ft_mod) #> [1] "lm" So, if we use function summary to obtain more information about the fitted model, the result will be: summary(ft_mod) #> #> Call: #> lm(formula = dat$y ~ dat$x) #> #> Residuals: #> Min 1Q Median 3Q Max #> -13.091 -5.144 -1.413 5.421 11.446 #> #> Coefficients: #> Estimate Std. Error t value Pr(>|t|) #> (Intercept) 1.8026 4.7689 0.378 0.71334 #> dat$x 1.1110 0.2771 4.009 0.00248 **
#> ---
#> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
#>
#> Residual standard error: 8.075 on 10 degrees of freedom
#> Multiple R-squared: 0.6164, Adjusted R-squared: 0.5781
#> F-statistic: 16.07 on 1 and 10 DF, p-value: 0.002482
In this case, function summary recognizes ft_mod as an object of class lm and applies a method that shows information about the fitted model, such as the distribution of the residuals, regression coefficients, t-tests, and the coefficient of determination ($$R^2$$), etc.
Thus, it is possible to use the same function on different classes of objects to obtain different results. This concept is very important in OneMap and you must remember it to use the package. For example, in other vignettes, we will show that depending on the class of the dataset, which can be outcross, f2, backcross, riself and risib, a certain set of procedures will be applied. Not by coincidence, these classes correspond to all types of populations that can be analyzed. The advantage of this approach is that you do not need to change the function to do a specific analysis; it will recognize the object type and will adapt accordingly.
Finally, you may need to save your work to come back to it in another working session. But before we explain how to do that, let us explain a few other concepts.
You can save your R Script, which is the file that has all R instructions you typed so far. You can later load them and run all instructions again to get the same results. This is easy: just click File, Save As, and choose a directory and a name (usually with the extension .R, such as Example1.R, etc).
A different thing is to save your R Session, with all objects you created so far (called R Workspace). This is not the same, because once you load the workspace, you will have all the objects already loaded, not requiring you to do everything again, i. e, running your script. This will help you to save a lot of time since some of the analyses required to build linkage maps are time demanding.
To do so, click Session, then Save Workspace As and choose a directory and name. In your next session, open RStudio and then go to Session, Load Workspace.
Alternatively, you can do that using the R function save.image, For example, if you want to save your analysis in a file named myworkspace.RData, you should use:
save.image("myworkspace.RData")
load("myworkspace.RData")
|
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|
https://www.gradesaver.com/textbooks/math/trigonometry/CLONE-68cac39a-c5ec-4c26-8565-a44738e90952/chapter-8-review-exercises-page-409/9
|
## Trigonometry (11th Edition) Clone
$29+37i$
Step 1: $(3+5i)(8-i)$ Step 2: $3(8-i)+5i(8-i)$ Step 3: $24-3i+40i-5i^{2}$ Step 4: $24+37i-5(-1)$ Step 5: $24+37i+5$ Step 6: $29+37i$
|
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http://webapp.cybercour.se/keywords/html
|
# HTML
## Other useful tags
There are many other tags in HTML.
## hr
The <hr> tag makes a horizontal line. Use it after a <p> tag, or before an <hx> tag, to break up sections of your document. Like this:
<p>Question: why did the turkey cross the road?</p>
<hr>
<p>To prove it wasn't chicken.</p>
It looks like this:
## But wait, there's more!
The Mozilla Development Network has good references for HTML, and other stuff.
Keywords:
## The story so far
In the last lesson, we looked at function parameters. Parameters let you reuse a function for different purposes. Check this out:
<button onclick="BetterPiggyBank.addCoin(0.01)" ...
<button onclick="BetterPiggyBank.addCoin(0.25)" ...
They all call the same function:
BetterPiggyBank.addCoin = function(amount) {
//Do something with amount.
}
## Arguments can be strings
amount is a number. So…
bc.
Keywords:
## Coding standards
Most projects have coding standards. They make code look the same in every file, making it predictable, and easy to read.
We'll use some basic coding standards for HTML, CSS, and JS.
## HTML
### Indenting
A standard we'll follow is indentation by four spaces. When a tag is inside another tag, use indenting to make containership clear. For example:
<div id="output-container" class="hide-on-load">
<p>I have a bracelet. It says:</p>
<p>What would <span id="character">Scooby Doo</span>?</p>
Keywords:
## The dude's life
How is the Dude's life?
(If you were logged in as a student, you could submit an exercise solution, and get some feedback.)
## Freddos
Write an app to keep track of your Freddos.
(If you were logged in as a student, you could submit an exercise solution, and get some feedback.)
## Better cheater
Make rock-paper-scissors cheater is less obvious.
(If you were logged in as a student, you could submit an exercise solution, and get some feedback.)
## Responding to hover
All the CSS we've done is static. Nothing the user does changes the way it looks, apart from resizing the browser.
CSS can respond to some user actions. We'll only talk about one of them: hover. When the user puts the mouse cursor on an HTML element, you can change the way it looks.
Here's some code we've seen before, with one addition:
bc.
Keywords:
## Pets, love, and evil
Make a table with data about pets.
(If you were logged in as a student, you could submit an exercise solution, and get some feedback.)
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|
https://stanleyriiks.wordpress.com/tag/goblin-like/
|
## FORTRESS FRONTIER By Myke Cole – Reviewed
Posted in Reviews, Uncategorized with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on August 5, 2013 by stanleyriiks
A bit of context for those who haven’t read the first book yet: this is like the X-Men, but with magic instead of mutations. When people develop magical abilities, or come up “latent”, things develop swiftly, and they have to report to the Police, otherwise they will be arrested as “Selfers”. There are some prohibited types of magic too dangerous to be allowed in society, the government use these “probes” as part of a secret service in an alternative dimension called the Source, to fight the indigenous population of goblin-like creatures. This is where Oscar Britton is sent, for training and indoctrination, when he develops “probe” magic and accidentally kills his father. But things don’t work out quite as planned for Britton and the Shadow Coven…
The first book in the Shadow Ops series left the remaining renegade sorcerers of Shadow Coven surrounded by goblins after FOB (Forward Operating Base) Frontier was partially destroyed, the witch Scylla was freed, and a massive battle had taken place. If you’re expecting this book to pick up straight after that then you’ll be disappointed. For the most part this is the story of Colonel Alan Bookbinder, Pentagon administrator, who turns up latent, but his magical abilities fail to fully develop. Despite this, he is sent to Frontier, where he becomes the second in command. The timelines of this and the first book overlap, as Bookbinder arrives before Britton and the rest of Shadow Coven go rogue. But when that does happen we see the other side of the action, as the base is left devastated and with no contact or supplies from the home plane (Earth). With rapidly depleted stocks of ammo and food the base becomes desperate and the goblin attacks increase daily. Bookbinder and a small team head out into the wilderness to try to find an Indian base hundreds of kilometres away, their lives on the line, and they are the only hope of survival for those left in the partially destroyed base.
Britton and Shadow Coven do play a part in the story, we get an update about half-way through and then Britton and his team are involved towards the end of the book, tying everything nicely together and preparing the reader for the third book in the series.
This is an SF military action thriller with magic thrown in for good measure. Although it doesn’t have the new and shiny feel of the first book, and the lack of my favourite character Marty (A Dobby-like good goblin), mean this feels a little like the second book in the series (the necessary part between the beginning and the climax [is this a trilogy?], continuing the story and an integral part, but not really adding a great deal.
Those who enjoyed the first book, and that should be plenty, because it’s pretty bloody good, should come to this with an open-mind and they’ll enjoy this slightly different but linked second part. Those expecting the continued story of Britton and Shadow Coven may be a little disappointed by the new direction.
Good fun, but not as good as the first book. I still want to know what happens next, and expect at some point a full-scale war between the sorcerers and the military, and possibly civil war!
## CONTROL POINT By Myke Cole – Reviewed
Posted in Reviews with tags , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , on April 10, 2013 by stanleyriiks
Oscar Britton is an army officer, and when he and his team are called to deal with a prohibited latent, they have a hell of a time. A latent is a person who develops magical powers. Certain magical powers are prohibited as too dangerous. One of Britton’s men is half killed by fire demons, and two teenage latents are shot dead, a school is burned, and Oscar has an argument with a sorcerer.
A few hours later Oscar has a latent episode, finding himself on the other side of the law. Knowing he has a prohibited magical power (opening wormhole-like gates) he goes on the run.
What follows is actually even more exciting and action packed than the beginning. As Oscar is “recruited” as a contractor for the army, and must face the tough challenges of learning to control his power on the front-line of a war with goblin-like creatures.
This doesn’t really have a slew of original ideas, but it’s put together very well, creating that newness and excitement. The military and magic are juxtaposed, and Oscar and his team work together to discover their powers and use them for good, despite the military’s view of them as weapons.
The book is a cross between Harry Potter and Stripes, or Biloxi Blues. The unique mix of military and magic makes this book. There is a little too much concentration on Oscar’s struggle to deal with his new power and his manipulation by the military, but that serves its own purpose and works within the context of the story. A kind of coming-of-age tale, using all the best bits of a military story, but a little fantasy thrown in for good measure. You can’t help but love little Marty, the goblin. There is plenty of action to speed things along.
Intelligent, exciting, pulse-racing and action packed. Full-on magical military mayhem.
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|
http://smi-protege.stanford.edu/svn/owl/branches/nci_june15/lib/owlsyntax.jar?view=markup&pathrev=1866
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# Contents of /owl/branches/nci_june15/lib/owlsyntax.jar
```New branch for the work for nci due on june 15
|
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http://mathonline.wikidot.com/chain-rule-to-functions-of-several-variables-examples-1
|
Applying The Chain Rule to Functions of Several Variables Examples 1
# Applying The Chain Rule to Functions of Several Variables Examples 1
We saw some examples of applying the various chain rules for functions of several variables on the Applying The Chain Rule to Functions of Several Variables page. We will now look at some more examples. Once again, here are the generic chain rules for reference:
If $z = f(x, y)$ has continuous first partial derivatives and $x = x(t)$ and $y = y(t)$ are differentiable then:
(1)
\begin{align} \quad \frac{dz}{dt} = \frac{\partial z}{\partial x} \frac{dx}{dt} + \frac{\partial z}{\partial y} \frac{dy}{dt} \end{align}
If $z = f(x, y)$ is a two variable real-valued function with continuous first partial derivatives, and $x = x(s, t)$ and $y = y(s, t)$ are functions of $s$ and $t$ then:
(2)
\begin{align} \quad \frac{\partial z}{\partial s} = \frac{\partial z}{\partial x} \frac{\partial x}{\partial s} + \frac{\partial z}{\partial y} \frac{\partial y}{\partial s} \end{align}
(3)
\begin{align} \quad \frac{\partial z}{\partial t} = \frac{\partial z}{\partial x} \frac{\partial x}{\partial t} + \frac{\partial z}{\partial y} \frac{\partial y}{\partial t} \end{align}
## Example 1
Suppose that $w = f(x, y)$, $x = g(r, s)$, $y = h(r, t)$, $r = k(s, t)$, and $s = m(t)$. Compute $\frac{\partial w}{\partial t}$.
This problem has many layers with it. We start with the outermost layer by applying the Chain Rule Type 2:
(4)
\begin{align} \quad \frac{\partial w}{\partial t} = \frac{\partial w}{\partial x} \frac{\partial x}{\partial t} + \frac{\partial w}{\partial y} \frac{\partial y}{\partial t} \\ \quad \frac{\partial w}{\partial t} = f_1(x, y) \frac{\partial x}{\partial t} + f_2(x, y) \frac{\partial w}{\partial y} \end{align}
Now we must compute both $\frac{\partial x}{\partial t}$ and $\frac{\partial y}{\partial t}$. Applying the Chain Rule again and we have that:
(5)
\begin{align} \quad \frac{\partial x}{\partial t} = \frac{\partial x}{\partial r} \frac{\partial r}{\partial t} + \frac{\partial x}{\partial s} \frac{\partial s}{\partial t} \\ \quad \frac{\partial x}{\partial t} = g_1(r, s) \frac{\partial r}{\partial t} + g_2(r, s) \frac{\partial s}{\partial t} \\ \quad \frac{\partial x}{\partial t} = g_1(r, s) \left ( \frac{\partial r}{\partial s} \frac{\partial s}{\partial t} + \frac{\partial r}{\partial t} \frac{\partial t}{\partial t} \right ) + g_2(r, s) m'(t) \\ \quad \frac{\partial x}{\partial t} = g_1(r, s) \left ( k_1(s, t) m'(t) + k_2(s, t) \cdot 1\right ) + g_2(r, s) m'(t) \\ \quad \frac{\partial x}{\partial t} = g_1(r, s) \left ( k_1(s, t) m'(t) + k_2(s, t)\right ) + g_2(r, s) m'(t) \end{align}
(6)
\begin{align} \quad \frac{\partial y}{\partial t} = \frac{\partial y}{\partial r} \frac{\partial r}{\partial t} + \frac{\partial y}{\partial t} \frac{\partial t}{\partial t} \\ \quad \frac{\partial y}{\partial t} = h_1(r, t) \frac{\partial r}{\partial t} + h_2(r, t) \cdot 1 \\ \quad \frac{\partial y}{\partial t} = h_1(r, t) \left ( \frac{\partial r}{\partial s} \frac{\partial s}{\partial t} + \frac{\partial r}{\partial t} \frac{\partial t}{\partial t} \right ) + h_2(r, t) \\ \quad \frac{\partial y}{\partial t} = h_1(r, t) \left ( k_1(s, t) m'(t) + k_2(s, t) \cdot 1 \right ) + h_2(r, t) \\ \quad \frac{\partial y}{\partial t} = h_1(r, t) \left ( k_1(s, t) m'(t) + k_2(s, t) \right ) + h_2(r, t) \\ \end{align}
Putting this all together and we get that:
(7)
\begin{align} \quad \frac{\partial w}{\partial t} = f_1(x, y) \left [ g_1(r, s) \left ( k_1(s, t) m'(t) + k_2(s, t)\right ) + g_2(r, s) m'(t) \right ] + f_2(x, y) \left [ h_1(r, t) \left ( k_1(s, t) m'(t) + k_2(s, t) \right ) + h_2(r, t) \right ] \end{align}
## Example 2
Compute the partial derivative $\frac{\partial}{\partial x} f(2x, 3y)$ and $\frac{\partial}{\partial x} f(2y, 3x)$.
Let's first compute $\frac{\partial}{\partial x} f(2x, 3y)$. If we let $u(x) = 2x$ and $v(y) = 3y$ then we have that $f(2x, 3y) = f(u(x), v(y))$. Applying the Chain Rule and we have that:
(8)
\begin{align} \quad \frac{\partial}{\partial x} f(2x, 3y) = \frac{\partial}{\partial x} f(u, v) = \frac{\partial f}{\partial u} \frac{\partial u}{\partial x} + \frac{\partial f}{\partial v} \frac{\partial v}{\partial x} = 2f_1(u, v) + 0f_2(u, v) = 2f_1(u,v) = 2f_1(2x, 3y) \end{align}
Now let's compute $\frac{\partial}{\partial x} f(2y, 3x)$. If we let $w(y) = 2y$ and $z(x) = 3x$ then we have that $f(2y, 3x) = f(w(y), z(x))$. Applying the Chain Rule and we have that:
(9)
\begin{align} \quad \frac{\partial}{\partial x} f(2y, 3x) = \frac{\partial}{\partial x} f(w, z) = \frac{\partial f}{\partial w} \frac{\partial w}{\partial x} + \frac{\partial f}{\partial z} \frac{\partial z}{\partial x} =0 f_1(w, z) + 3f_2(w, z) = 3f_2(w, z) = 3f_2(2y, 3x) \end{align}
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https://www.proofwiki.org/wiki/Definition:Class_of_All_Cardinals
|
# Definition:Class of All Cardinals
## Definition
The class of all cardinals is the class consisting of all cardinals:
$\NN = \set {x \in \On: \exists y: x = \size y}$
where $\size y$ denotes the cardinal corresponding to the set $y$.
## Also see
• Results about the class of all cardinals can be found here.
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https://open.kattis.com/problems/dominoes2
|
Kattis
Dominoes 2
Dominoes are lots of fun. Children like to stand the tiles on their side in long lines. When one domino falls, it knocks down the next one, which knocks down the one after that, all the way down the line. However, sometimes a domino fails to knock the next one down. In that case, we have to knock it down by hand to get the dominoes falling again.
Given a set of dominoes that are knocked down by hand, your task is to determine the total number of dominoes that fall.
Input
The first line of input contains one integer specifying the number of test cases to follow. Each test case begins with a line containing three integers $n, m, l$ no larger than $10\, 000$, followed by $m$+$l$ additional lines. The first integer $n$ is the number of domino tiles. The domino tiles are numbered from 1 to $n$.
Each of the $m$ lines after the first line contains two integers $x$ and $y$ indicating that if domino number $x$ falls, it will cause domino number $y$ to fall as well. Each of the following $l$ lines contains a single integer $z$ indicating that the domino numbered $z$ is knocked over by hand.
Output
For each test case, output a line containing one integer, the total number of dominoes that fall over.
Sample Input 1 Sample Output 1
1
3 2 1
1 2
2 3
2
2
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https://lessonplanet.com/teachers/physical-fitness-frisbee
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# Physical Fitness/ Frisbee
Learners work on their physical fitness level in preparation for the physical fitness test. They practice throwing and catching a frisbee.
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https://www.physicsforums.com/threads/jacobi-symbol.165338/
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# Jacobi Symbol
1. Apr 12, 2007
### nick727kcin
Jacobi Symbol - Binary
NOTE: if its past 8:30 AM Eastern Time, dont worry about it. thanks for the consideration
The Question:
Exercise 13.1. Develop a “binary” Jacobi symbol algorithm, that is, one
that uses only addition, subtractions, and “shift” operations, analogous to
the binary gcd algorithm in Exercise 4.1.
heres the algorithm that i came about with so far:
Note: it is right, except for the fact that there cant be mod, division, multiplication, etc.
t := 1;
while (a > O and a < O) do
.........while (a mod 2 = O) do
................a = a/2;
................if (n mod 8 = 3) or (n mod 8 = 5) then t := -t;
.........if (a < n) then
................interchange(a,n);
................if (a mod 4 = 3) and (n mod 4 = 3) then t = -t;
.........a := (a-n)12;
.........if (n mod 8 = 3) or (n mod 8 = 5) then t = -t;
if (n = I) then return(t) else return(O).
Last edited: Apr 12, 2007
Can you offer guidance or do you also need help?
Draft saved Draft deleted
Similar Discussions: Jacobi Symbol
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https://www.reakkt.com/2014/06/let-wind-blow-or-forecasting-wind-power.html
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## Wednesday, June 11, 2014
### Let the wind blow or forecasting the wind power
I have mentioned recently, that the production of renewable energy sources is difficult to predict. Let's examine some of the challenges.
The difference between production and forecast can fluctuate wildly, sometimes exceeding +/-50% of the installed wind farm capacity.
Chart: differences between production and P50 forecast
(P50 forecast is the average expected energy production)
The distributions of differences between production and forecast have high kurtosis, and both tails are pretty long.
Chart: Distribution of differences between production and P50 forecast
(P50 forecast is the average expected energy production)
It seems, assumption of the normal distribution of the production, customarily used in wind power forecasting, may not always be correct.
Chart: Assumed normal distribution of (long term) power production
(P50 forecast is the average expected energy production)
It shouldn't surprise then that production often exceeds both conservative P50 and aggressive P90 forecast levels.
Chart: Production (gray bars) vs. P05-P90 forecast band (red and green dotted lines)
On the other hand, production significantly lower than forecast is also not welcome. Since forecasts are the basis of the declared planned production levels on the Day-Ahead Market (DAM), all deviations require costly balancing.
The forecast spread, or the width of the forecast (difference between P90 and P05), which should reflect the forecast probability does not always add any value.
Also, it doesn't help that in addition to the weather-related production forecast, one needs to deal with planned availability of a plant. The planned availability is connected among others with scheduled maintenance, but not everything always goes according to the plan.
As a result, a plant operator needs to deal with additional random variable. It sometimes happens that the plant stops producing long before the planned availability goes to zero, and starts producing, when the planned availability still equals zero.
Chart: Production (black line) vs. planned availability (grey area)
Weather is a factor that affects both production forecast and availability. While wind may be strong, suggesting high production, temperature may lead to operational problems that may not be fully reflected in planned availability. As a result, one may experience noticeable periodic disparity between forecast and production.
Chart: Average monthly difference between production and P50 forecast for different farms
Even with operational information, less than one year of data is too little to decide whether we face here a seasonal effect which should be adjusted for in the next years, or one time event.
To get better alignment between forecast and production the following directions seems promising:
• use energy storage
• develop better weather forecasting models
• include farm operational data it into the production forecast models
• utilize prices, and price forecasts, where adequate
For more about wind forecasting, see: https://pinboard.in/u:mjaniec/t:res/t:wind_forecasting/
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http://math.stackexchange.com/users/13675/kjo?tab=questions&sort=newest
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kjo
Reputation
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Next privilege 5,000 Rep.
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# 129 Questions
1
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### What's the name of this tensor product?
may 28 at 15:50 kjo 4,566
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### Conditions for “equal cardinality $\Rightarrow$ equal (finite) measure”?
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### Is there a name for products $\Delta(v)\!\cdot\!M$ and $M\!\cdot\!\Delta(w)$?
oct 11 at 19:16 kjo 4,566
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### Looking for name of function for the indexing of one ordering relative to another
sep 29 at 21:59 kjo 4,566
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### What's the name of $\sum_{k = 0}^{n} (-1)^k {n \choose k} (n-k)^w$?
aug 17 at 15:25 kjo 4,566
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### Looking for a a measure-theoretic treatment of “differential entropy”
apr 12 '14 at 0:58 kjo 4,566
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### Direct proof of: $\#($cover of $V) < \#F \; \Rightarrow \;V$ belongs to cover
jan 19 '14 at 2:50 kjo 4,566
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http://www.ece.ucdavis.edu/vcl/vclpeople/jwwebb/measbd/ctrl_fpga/cdev/docs/doxys_docs/common/help/helpsrc/Command_Reference/fnCmd0_page_description.html
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HELP - fnCmd
Description
Attaching comment block to a specific function ( fn )
The var command is used to explicitly link a documentation comment block to the specified function. When documenting functions it's necessary to specify the return type (also if it's void) of the function along with the parameter types.
Syntax
/** \fn [scope][(param_type, param_type ..)] Normal way of documenting goes here .... */
Example
/** \fn int FreeFunction(int) Normal way of documenting goes here .... */
Output
The var command does not produce any output of its own, but secures that the comment block as a whole is used to produce the documentation of the specified class. But see FreeFunction().
About putting the documentation in separate files
This command is used for documenting an entity away from it's definition in the code. See SeparateDocs for some examples.
The commands for making separate documentation are:
\class, \def, \enum, (\file), \fn, \namespace, \struct, \typedef, \union \var
Qualify with scope (class, namepace) if inside a scope like this:
\enum SepDocClass::ClassEnum
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http://math.stackexchange.com/questions/575266/how-to-check-if-the-series-sum-n-0-infty-sqrtn1-sqrtn-is-converge/575288
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# How to check if the series $\sum_{n=0}^{\infty} \sqrt{n+1}-\sqrt{n}$ is convergent
or divergent??
I tried few tests, but I didn't success to discover if the series is convergent or is divergent...
$$\sum_{n=0}^{\infty} \sqrt{n+1}-\sqrt{n}$$
Thank you!
-
This problem is not well-defined. Take $n=0$. Are we allowing complex-valued summands? – user28877 Nov 20 '13 at 22:31
This is just a telescoping series. So what do you get as a result? Then just turn this into rigour. – Chris K Nov 20 '13 at 22:34
@YoavFridman, when you take the sum from $0$ to $N$, you get $\sqrt{N} - \sqrt{0} = \sqrt{N}$. Now we can always take $k$ sufficiently large such that $|\sqrt{N} - \sqrt{k}|>\varepsilon$ where we let $\varepsilon>0$. So, if you treat the series like a sequence, it is not Cauchy. So, by contrapositive, the series can't be convergent. – Chris K Nov 20 '13 at 22:41
It's telescoping. I don't see why anyone would approach the problem in a more complicated way. – Doc Nov 20 '13 at 22:49
A correction to my earlier comment... should be $\sqrt{N+1}$ and not $\sqrt{N}$ but the idea stays the same. – Chris K Nov 20 '13 at 22:53
Let $S_n$ be the sequence of partial sums: $$S_n = \sum_{k=0}^n \sqrt{k+1} - \sqrt{k}$$ It is easy to see that $S_0 = 1$ and by telescoping $$S_n = \sqrt{n+1}$$ Since convergence of a series is defined through convergence of the partial sums and since $S_n$ obviously diverges, the series diverges as well.
$$a_n=\sqrt{n+1}-\sqrt{n}=\frac{1}{ \sqrt{n+1}+\sqrt{n}}\sim_{n\to \infty} \frac{1}{2\sqrt{n}}=b_n$$
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http://www.skyandtelescope.com/astronomy-news/globular-clusters-faint-galaxies/
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# Globular Clusters for Faint Galaxies
The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.
This Hubble image of Dragonfly 44, an extremely faint galaxy, reveals that it is surrounded by dozens of compact objects that are likely globular clusters.
van Dokkum et al. 2017
### Faint-Galaxy Mystery
Hubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked.
van Dokkum et al. 2017
UDGs — large, extremely faint spheroidal objects — were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.
Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:
1. UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.
2. UDGs are effectively “failed” galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.
Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.
### Globulars Galore
Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy.
van Dokkum et al. 2017
Van Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions.
The most striking feature of these galaxies, however, is that they are surrounded by a large number of compact objects that appear to be globular clusters. From the observations, Van Dokkum and collaborators estimate that Dragonfly 44 and DFX1 have approximately 74 and 62 globulars, respectively — significantly more than the low numbers expected for galaxies of this luminosity.
Armed with this knowledge, the authors went back and looked at archival observations of 14 other UDGs also located in the Coma cluster. They found that these smaller and fainter galaxies don’t host quite as many globular clusters as Dragonfly 44 and DFX1, but more than half also show significant overdensities of globulars.
### Evidence of Failure
Main panel: relation between the number of globular clusters and total absolute magnitude for Coma UDGs (solid symbols) compared to normal galaxies (open symbols). Top panel: relation between effective radius and absolute magnitude. The UDGs are significantly larger and have more globular clusters than normal galaxies of the same luminosity.
van Dokkum et al. 2017
In general, UDGs appear to have more globular clusters than other galaxies of the same total luminosity, by a factor of nearly 7. These results are consistent with the scenario in which UDGs are failed galaxies: they likely have the halo mass to have formed a large number of globular clusters, but they were quenched before they formed a disk and bulge. Because star formation never got going in UDGs, they are now much dimmer than other galaxies of the same size.
The authors suggest that the next step is to obtain dynamical measurements of the UDGs to determine whether these faint galaxies really do have the halo mass suggested by their large numbers of globulars. Future observations will continue to help us pin down the origin of these dim giants.
### Citation
Pieter van Dokkum et al 2017 ApJL 844 L11. doi:10.3847/2041-8213/aa7ca2
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https://open.kattis.com/problems/savingdaylight
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Kattis
# Saving Daylight
The shortest day of the year in the northern hemisphere is the winter solstice, around December 22, which marks the beginning of winter. This day is not really any shorter, of course, because it still has 24 hours. But it has the fewest hours of daylight of any day. On the other hand, the longest day (the summer solstice) is around June 22.
Being a weather buff you would like to know just how much time the sun is above the horizon on different days during the year. Because you are an impressive programmer, you should write an impressive program to do just that.
## Input
Input has between $1$ and $1\, 000$ days, one day per line. Each line contains the month, day, year, time that the sun rises, and time that the sun sets. Adjacent fields are separated by a single space. Times are expressed in 24-hour format in the range 0:00 to 23:59 (integer hours and minutes separated by a colon, with minutes zero-padded). The time of sunrise is always earlier than the time of sunset, and your solution should ignore any time-changing effects (such as daylight saving time). Input ends at the end of file.
## Output
Print the month, day, and year as given in the input followed by the amount of time that the sun is above the horizon in hours and minutes (always plural).
Sample Input 1 Sample Output 1
June 22 2005 6:24 20:37
December 22 2005 7:24 17:30
November 2 2005 6:45 17:38
January 8 1992 7:45 18:46
June 22 2005 14 hours 13 minutes
December 22 2005 10 hours 6 minutes
November 2 2005 10 hours 53 minutes
January 8 1992 11 hours 1 minutes
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https://search.r-project.org/CRAN/refmans/buildmer/html/tabulate.formula.html
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tabulate.formula {buildmer} R Documentation
## Parse a formula into a buildmer terms list
### Description
Parse a formula into a buildmer terms list
### Usage
tabulate.formula(formula, group = NULL)
### Arguments
formula A formula. group A character vector of regular expressions. Terms matching the same regular expression are assigned the same block, and will be evaluated together in buildmer functions.
### Value
A buildmer terms list, which is just a normal data frame.
form <- diag(f1 ~ (vowel1+vowel2+vowel3+vowel4)*timepoint*following +
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https://www.physicsforums.com/threads/laplace-transform-of-a-piecewise-function.808024/
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# Laplace transform of a piecewise function
1. Apr 11, 2015
### Feodalherren
1. The problem statement, all variables and given/known data
f(t) = e^t when 0≤t<1
and 0 when t≥1
2. Relevant equations
Laplace transformations
3. The attempt at a solution
so the Laplace integral becomes
from 0 to 1 ∫e^(st^2)dt + 0
how do I integrate this?
2. Apr 11, 2015
### Rellek
Clarification:
Laplace transform or Lagrange Transform...?
3. Apr 11, 2015
### Feodalherren
4. Apr 11, 2015
### Rellek
Alright, let's do this:
From 0 to 1 we have one function, and from 1 onward we have another. Split up our integral as so:
$$\int_0^1 e^{-st} e^{t}dt + \int_{1}^{\infty} e^{-st}(0)dt \implies \int_0^1 e^{t(1-s)}dt$$
5. Apr 11, 2015
### Feodalherren
Wait a second, doesn't the part that goes from 1 to +infinity get canceled out because the integral becomes
∫ e^(-st) (0) dt = 0
?
6. Apr 11, 2015
### Rellek
Excuse my reading comprehension, I thought it said f(t) = 1. Corrected.
7. Apr 11, 2015
### Feodalherren
Ah now I see what I did wrong! DUH! Such a stupid mistake.
Thank you sir!
8. Apr 11, 2015
### SteamKing
Staff Emeritus
How did you get an integrand of est2 ?
Remember, ex ⋅ ey = e(x + y), not exy
9. Apr 11, 2015
### Feodalherren
I was just asking myself the same thing. I think I need to take a break. I've been doing math since 7.30 this morning. It's 1.30 pm now :).
|
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https://read.somethingorotherwhatever.com/entry/Cui2012
|
# The Canonical Basis of $\dot{\mathbf{U}}$ for Type $A_{2}$
• Published in 2012
The modified quantized enveloping algebra has a remarkable basis, called the canonical basis, which was introduced by Lusztig. In this paper, all these monomial elements of the canonical basis for type $A_{2}$ are determined and we also give a conjecture about all polynomial elements of the canonical basis.
## Other information
key
Cui2012
type
article
2012-08-29
date_published
2012-08-01
arxivId
1208.5531
keywords
algebra,canonical basis,the modified quantized enveloping,the quasi-
### BibTeX entry
@article{Cui2012,
key = {Cui2012},
type = {article},
title = {The Canonical Basis of {\$}\dot{\{}\mathbf{\{}U{\}}{\}}{\$} for Type {\$}A{\_}{\{}2{\}}{\$}},
author = {Cui, Weideng},
abstract = {The modified quantized enveloping algebra has a remarkable basis, called the canonical basis, which was introduced by Lusztig. In this paper, all these monomial elements of the canonical basis for type {\$}A{\_}{\{}2{\}}{\$} are determined and we also give a conjecture about all polynomial elements of the canonical basis.},
comment = {},
}
|
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|
https://stats.stackexchange.com/questions/404149/gamma-distribution-parameters-estimation
|
# Gamma distribution parameters estimation [closed]
I have a set of samples taken from a population distributed with a Gamma distribution, so $$$$f_X(x)=\frac{\beta^\alpha}{\Gamma(\alpha)}x^{\alpha-1}e^{-\beta x}$$$$ I should estimate $$\alpha$$ and $$\beta$$, so knowing that $$$$\alpha=\frac{E[X]^2}{\text{Var}[X]},\quad \beta=\frac{E[X]}{\text{Var}[X]}$$$$ My idea is to compute $$\hat \mu, \hat \sigma^2$$ from the set as estimators of the mean and average of the population, then find $$\hat \alpha,\hat \beta$$ as follows $$$$\hat \alpha=\frac{\hat \mu^2}{\hat \sigma^2},\quad \hat \beta=\frac{\hat \mu}{\sigma^2}$$$$
I'm trying to apply this logic to a task with a set of 10000 samples, but approximations seems to be not good enough. Is there any flaw in this reasoning?
EDIT: I've also tried the Newton-Raphson method to find alpha. This method leads to approximations very similar to the ones that I get from the method of moments.
EDIT 2: The logic is correct. Problem was a wrong understanding of the results of the implementation of this logic: in my task there was just half of the data needed to get all the estimators required. That is true for any possible method. Also approximation was fine.
## closed as unclear what you're asking by Stephan Kolassa, Michael Chernick, user158565, COOLSerdash, whuber♦Apr 23 at 14:37
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.
• You're using the method-of-moments estimators, afaik. In what way to you find them unsatisfying? Another possibility would be to use the maximum likelihood estimators. – COOLSerdash Apr 20 at 17:04
• What @COOLSerdash says. The gamma can be parameterized in two different ways, are you sure you are not confusing something there? That could be a simple explanation for why your results may be bad. – Stephan Kolassa Apr 20 at 17:07
• @COOLSerdash yes it is. I assume that for 10000 samples the method should work fine to have a good approximation. – ezy Apr 20 at 18:35
• FWIW, your expression for $f$ isn't quite correct. It's difficult to determine what you mean by "each letter with a unique ... combination" and it's impossible to determine what you mean by "unsatisfying." Could you clarify your question? – whuber Apr 23 at 4:00
• Without explanation of, or evidence for, "unsatisfying" results this question remains unclear. – Nick Cox Apr 24 at 8:16
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https://www.szkoleniakalisz.pl/other-crushing-plant/4kmg655u/sand.html
|
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2. sand dry volume
# sand dry volume
Adry sandis placed in a container having avolumeof 0.0089 cm^3. Thedryweight of the sample is 0.014 gms. Water is carefully added to the container so as not to disturb the condition of thesand. When the container is filled the combined weight of the soil plus water is 0.0174 gms. Determine: a) Void ratio of the soil in the container. b ...
### Sand, dry weight to volume conversion Aqua Calc
1 631 kilograms [kg] of Sand, dry fit into 1 cubic meter. 101.82 pounds [lbs] of Sand, dry fit into 1 cubic foot. Sand, dry weighs 1.631 gram per cubic centimeter or1 631 kilogram per cubic meter,i.e. density of sand, dry is equal to 1 631 kg/m³.
### Sand, dry volume to weight conversion
9 rows· AboutSand,dry;1 cubic meterofSand,dryweighs1 631 kilograms[kg] 1 cubic foot of ...
### How we can determine the dry sand density
Density of Sand: In general, Density can bedefined asmass per unit volume/mean particles per unit volume. The sand densityvariesupon several factors and its conditions.Normal loosedry sand...
### Density of Sand Calculator
Density of Sand: In general, Density can be defined as mass per unit volume/mean particles per unit volume. The sand density varies upon several factors and its conditions. A normalloosedry sand has the density of 1442 kg/m 3.
### Dry Volume Formula, Wet Volume Of Concrete And Mortar In
Oct 05, 2019· Sand: 20% (voids are filled up particles are reduced) Cement: Inconsiderable (because of fine particles) By summing up the percentage of aggregate and sand, we get 34% + 24% = 54%. Dry Volume is greater than 54% of wet volume. = 100/100 + 54/100 = 1 + .54 = 1.54. Because of that, Dry Volume = 1.54 x wet volume.
### Dry and wet volume of concrete and their difference
Feb 27, 2020·VolumeofDrymix of different ingredients of concrete like cementsandand aggregate before adding water is known asdry volumeof concrete having air voids and pores between particles.Dry volumeof concrete is mixture of cement,sandand aggregate without water indrycondition, theirvolumeis increased by 54% of wetvolumedue to presence ...
### Sand Calculator how much sand do you need in tons
A cubic yard of typical sand weighsabout 2700 pounds or 1.35 tons.A square yard of a sandbox with a depth of 1 foot (30.48 cm) weighs about 900 pounds (410 kg) or slightly less than half a ton. The water content of the sand is assumed to be moderate.
### Sand Density vCalc
Loose Sand: 1442 kg/m 3. This is dry sand that has been moved or otherwise agitated to loosen the natural packing process. Dry Sand:1602 kg/m3. This is sand in its natural undisturbed form where it …
### SAND CALCULATOR [How Much Sand do I Need ] Construction
Thesand’sdensity is 100 lb/ft³ and costs $10 per ton. The calculator would perform the following calculations: $$Area = Length \times Width = 5 ft \times 3 ft = 15 ft^2$$. $$Volume = Area \times Depth = 15 ft^2 \times 2\,in = 2.5 ft^3$$.$\$Weight =Volume\times Density = 2.5ft^3 \times 100\,lb/ft^3 = …
### DensityofSandCalculator
DensityofSand: In general,Densitycan be defined as mass per unitvolume/mean particles per unitvolume. Thesand densityvaries upon several factors and its conditions. A normal loosedry sandhas thedensityof 1442 kg/m 3.Sand DensityFormula: The ratio of mass of thesandto thevolumeof calibrating container gives you thedensityofsand.
### How to Calculate CementSandand Aggregate Quantity in
Dry volumeof concrete = 1 + 0.54.Dry volumeof concrete = 1.54 (Volumeincreased by 54%) Why we take 54 %? The reason isdryaggregate,sandand cement contain air voids.Dryaggregate contains 33 to 34% air voids, whereassandcontains 20% air voids and cement contains very fine particles hence it contains negligible are voids so we can ...
### How wecan determine the dry sand density
Normal loosedry sandhas the density of 1442 kg/m3.SandDensity Formula: The ratio of mass of thesandto thevolumeof calibrating container gives you the density ofsand.
### SandDensity vCalc
Processing... ... ...
### Calculation of Cement andSand Quantity for Plastering
VolumeofSandrequired (using 1:4 proportion) = 0.036 x 4 = 0.144 x 1600 = 230 kgs (consideringsand drybulk density as 1600 kgs/cum.) Usually around 20% of water by weight of the totaldrymaterial is mixed in the mixture to achieve the desired workability.
### Sand Calculator
Thevolumeofsandrequired is equal to thevolumeof excavation. Oursand calculatorwill display this value for you. All right, but how much does a yard ofsandweigh? To calculate the weight of a cubic yard ofsand, you simply have to multiply itsvolumeby its density. You don't have to remember the density ofsandthough - our calculator ...
### Sand Weight vCalc
Processing... ... ...
### How To Calculate Number Of Bricks, Cement AndSandFor
Dry volumeof a mortar = 0.2305 cum X 1.33 = 0.306565 cum We know the mortar ratio is 1:6 (1 part Cement & 6 PartSand= 7 Part) Required amount Cement quantity in brickwork = …
### BulkDensityofSand Civil Engineering
BulkDensityofSand. The bulkdensityor unit weight ofsandis the mass or weight of thesandthat required to fill a container of a specified unitvolume. BulkDensityofsand= Mass odsand/volume. Key Features: If thevolumeis unit then, BulkDensity= Mass. Unit in kg/m 3 or lb/ft 3.
### How tocalculate brick, sand and cement in brick masonry
Jun 23, 2018· It could be much better if you mention grade of Mortar, workvolumeof brick masonry and class of bricks too. Assuming 1. Grade of mortar = 1:6 (cement :sand) 2. Class A brick (19 cm x 9 cm x 9 cm) 3.Volumeof brickwork = 1.0 m^3 4. Thickness of...
### Howto calculate cement sand quantity in1 6 mortar
Part ofsand= 6/7 calculation:- we know that while we calculatedry volumeof cement mortar cofactor 1.54 is multiply in wetvolumeof mortar considering wastage of mortar andvolumeincrease. Wetvolume= 1m3.Dry volume=wetvolume× 1.54 = 1m3× 1.54 = 1.54 m3.Dry volumeof mortar = 1.54 m3. A) calculation of cement quantity
### What is Bulking of Sand Its Calculation, Classification.
Thevolumeof moistsandwill be more than that ofdry sand. This change (increase) in thevolumeof sands on getting moist is termed as bulking ofsand. Full knowledge of the bulking ofsandis necessary for a construction engineer becausesandis used for mortars, plasters, and concrete byvolume.
### Bulking ofSand,Test to Calculate Bulking in Sand
Sep 03, 2017· Therefore this helps in finding the actualvolumeofsand(dry sand). In simple words, thedry sandand fully saturatedsandhave the exactvolume. The percentage of bulking can be determined by following this method:-1. Take a simple container and add 2/3 part ofsandin it. 2. Measure the exact height ofsandusing the scale and note it down.
### CalculatingDry Volume of Mortar Dry VolumeFormula
Given below, the detail process to work out thedry volumemortar and thensandand cement quantity for this 10 cubic feet mortar. How to work outthe dry volume of mortarIt is known thatthe dry volume of mortaris, = Wetvolumeof mortar x 1.30 =10 x 1.30 …
### How to Calculate Quantities of Cement,Sandand Aggregate
Thedry volumeof concrete mixture is always greater than the wetvolume. The ratio ofdry volumeto the wetvolumeof concrete is 1.54. So 1.54 Cum ofdrymaterials (cement,sandand aggregate) is required to produce 1 Cum of concrete.Volumeof Cement required = 1/(1+2+4) X 1.54 = 1/7 X 1.54 = 0.22 Cum.VolumeofSandrequired = 2/7 X 1.54 ...
### Howto calculate cement sand quantity in1 6 mortar
Part ofsand= 6/7 calculation:- we know that while we calculatedry volumeof cement mortar cofactor 1.54 is multiply in wetvolumeof mortar considering wastage of mortar andvolumeincrease. Wetvolume= 1m3.Dry volume=wetvolume× 1.54 = 1m3× 1.54 = 1.54 m3.Dry volumeof mortar = 1.54 m3. A) calculation of cement quantity
### How to Calculate CEMENT,SANDQuantity for PLASTERING
Dec 25, 2018·Volume= 100*0.015 m3.Volume= 1.5 m3. Note:Dry volumeis approx 1.54 times more than wetvolume, because 34-35% is bulking ofsandand approx 20% is wastage ofsand. So the OriginalDry VolumeRequired = 1.54*1.5 m3
### How To Calculate Cement,SandAnd Coarse Aggregate For
So to get 1 m3 of wetconcrete, we have to multiply thedry volumeby 1.55. What is 1.54 constant inconcretecalculation? Bulking ofSand– If the moisture is present in thesand, then it makes thesandlook bulkier, which could result in inadequatesandproportion in theconcreteratio.
### Cement Mortar Estimation of Cement, Sand Water in
Jul 09, 2019·Volumeofsandis =Volumeofdrymortar x (Parts ofsand/ Total parts of ingredient) = (1.3×6)/7=1.14 m 3 ofsandor fine aggregate. Quantity of Water. For wet mortar recommended water-cement ratio varies from 0.4 to 0.6. Further, water requirement depends on any admixture added to mortar to improve its workability. Admixtures must be added ...
### BulkDensityofSand Civil Engineering
BulkDensityofSand. The bulkdensityor unit weight ofsandis the mass or weight of thesandthat required to fill a container of a specified unitvolume. BulkDensityofsand= Mass odsand/volume. Key Features: If thevolumeis unit then, BulkDensity= Mass. Unit in kg/m 3 or lb/ft 3.
### QUIKRETE 50 lb Dry Mason Sandin theSanddepartment at
ShopQUIKRETE 50-lb Dry Mason Sandin theSanddepartment atLowe's.com. QUIKRETE MasonSandis suitable for field-preparation of mortar.
### Tile Flooring Cost Estimation Explanation with Online
WetVolumeof the cement mortar required = 0.6 m 3. We need 1.5 m 3volumeof wet cement mortar that means, we need this muchvolumeafter adding water to cement andsandmix.Dry volumeof mortar is considered as 25% of more of wetvolume. Related: Cement Mortar Calculation for Plastering. In order to calculate thedry volume,
### How much cement,sandand water is required for 12mm thick
VolumeofSandrequired (using 1:4 proportion) = 0.036 x 4 = 0.144 x 1600 = 230 kgs (consideringsand drybulk density as 1600 kgs/cum.) Usually around 20% of water by weight of the totaldrymaterial is mixed in the mixture to achieve the desired workability.
### Density of CementSandand Aggregate Cement Density
When thesandis wet, the water is in thesand, also affecting the total matter in thevolume. The average density of the differentsandconditions is as follows: Loosesand: 1442 kg / m 3. It isdry sandthat has been moved or agitated to loosen the natural packaging process.Dry sand: 1602 kg / m 3. It issandin its undisturbed natural form ...
### BeachSand1 cubic metervolumeto kilograms converter
1. practicing cubic meters and kilograms of beachsand( m3 vs. kg - kilo ) measuring values exchange. 2. beachsandamounts conversion factors - between numerous unit pairs variations. 3. working with mass density - how heavy is avolumeof beachsand- values and properties. International unit symbols for these two beachsandmeasurements are:
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https://ashpublications.org/blood/article/12/2/189/27766/Reed-Sternberg-Cells-in-the-Peripheral-Blood
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Abstract
A case of Hodgkin’s disease is presented, in which Reed-Sternberg cells were observed in the peripheral blood.
This content is only available as a PDF.
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https://physics.stackexchange.com/questions/63319/what-is-a-sudden-singularity
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# What is a sudden singularity?
I've seen references to some sort of black hole (or something) referred to as a sudden singularity, but I haven't seen a short clear definition of what this is for the layman.
• The best paper I could find on this is arxiv.org/abs/gr-qc/0701056 It seems a "sudden singularity" is an instantaneous change in pressure or the expansion of the universe but it seems like any non-continuous (non-differentiable) change in the expansion of space qualifies. – Brandon Enright May 4 '13 at 22:52
• Why the downvote? This seems to me a perfectly reasonable question. – John Rennie May 5 '13 at 8:25
• @JohnRennie: I downvoted because the question didn't show any research effort. – Ben Crowell May 5 '13 at 12:46
• @BenCrowell: if a physics student were asking the question I'd agree, but for a non-physicist I haven't found any description of a sudden singularity (apart from mine of course :-) that is remotely accessible. – John Rennie May 5 '13 at 13:19
• Thanks for the answers and comments. This give valuable context. I did try the Google Search before posting this, but I am happy to have an answer that is less effort than a layman parsing through the various papers. And now I see that this question is in the top 10 of Google Search, so hopefully it will help others like me in the future. – Skotch May 6 '13 at 17:45
A sudden singularity is a singularity that forms in the universe in a finite time.
This may see like a strange definition. After all, don't the singularities in black holes form in a finite time, so shouldn't they, and indeed all singularities be sudden? Actually, no! For observers like us, floating around the universe, in our frame of reference it takes an infinite time for a black hole to form.
This apparently paradoxical result has been too widely discussed, in this site and elsewhere, for it to be worth me elaborating on it here. An observer falling into the black hole will encounter the singularity in a finite time, but for observers outside the event horizon the singularity never forms. The type of big rip singularity usually referred to as a sudden singularity forms in a finite time (for all observers) because we are in effect falling towards it just like the observer falling into a black hole.
A quick footnote:
As Ben points out in his answer, my definition above is too broad because it includes singularities (like the Big Crunch) that are not sudden. as described in Nojiri's paper, sudden singularities are just one of the four types of singularities that can occur at non-zero scale factors (i.e. not the Big Bang or Big Crunch). I'm not sure how usefully this can be summarised for the lay reader since it's all a bit technical. @Skotch, I would have a look at Nojiri's paper and maybe ask a further question if you want anything in it carified.
• This is incorrect because it fails to distinguish between a Big Crunch singularity and a sudden singularity. – Ben Crowell May 5 '13 at 13:04
• Hmm, good point. I've only heard the phrase used to refer to Big Rip type singularities, but maybe a Big Crunch would also be sudden singularity. – John Rennie May 5 '13 at 13:18
• Actually it looks like it doesn't even refer to Big Rip scenarios -- see my answer. – Ben Crowell May 5 '13 at 13:50
• Ah yes. See also arxiv.org/abs/hep-th/0501025. This paper seems to be referenced a lot in discussions of sudden singularities. – John Rennie May 5 '13 at 14:16
• That's useful -- they give a more explicit definition than Barrow or Cotsakis. – Ben Crowell May 5 '13 at 14:18
People have known for a long time about the existence of cosmological models that include a Big Crunch singularity. In these models, the density of matter in the universe is great enough to cause it to recontract. These models are no longer of interest as descriptions of the actual universe, since we now know that the expansion of the universe is accelerating rather than decelerating, presumably due to dark energy with poorly known properties.
In fact, if dark energy turns out to have certain characteristics, then it's possible that the expansion will blow up at some point, so that all matter is destroyed by being torn apart. The most commonly discussed scenario of this type is called a Big Rip, but there are other scenarios as well, classified in Cotsakis 2004. A singularity like this has two properties: (1) it happens at a finite time in the future, and (2) it's a blow-up, not a recollapse like the Big Crunch. There can be cases where the cosmological scale factor $a$ blows up, and others where $a$ stays finite, but $\dot{a}$ blows up. For comparison, a Big Crunch would have $a$ going to zero.
The term "sudden singularity" seems to be used in the literature for one very specific type of blow-up. Cotsakis says, "For instance, they may correspond to ‘sudden’ singularities (see [19] for this terminology)," where reference 19 is Barrow 2004. Barrow constructs an example that is not driven by dark energy at all. The strong energy condition holds, and both the density and the scale factor are always constant. However, the pressure and curvature blow up to infinity at a finite time. He gets this behavior by not requiring any equation of state to hold between the pressure and the density. Since both Barrow and Cotsakis seem to be defining the term based on one example (the word "sudden" only appears in Barrow's title), it's a little hard to tell exactly how broad they intend this definition to be. Nojiri 2005 defines a sudden singularity as one in which the pressure blows up to plus or minus infinity at some finite time, while the scale factor and density stay finite. This implies that a sudden singularity can never occur if there is a definite equation of state.
John D. Barrow, 2004, "Sudden Future Singularities," http://arxiv.org/abs/gr-qc/0403084
Spiros Cotsakis, Ifigeneia Klaoudatou, 2004, "Future Singularities of Isotropic Cosmologies," http://arxiv.org/abs/gr-qc/0409022
Nojiri et al., 2005, "Properties of singularities in (phantom) dark energy universe," http://arxiv.org/abs/hep-th/0501025
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https://hal.inria.fr/inria-00070439
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HAL will be down for maintenance from Friday, June 10 at 4pm through Monday, June 13 at 9am. More information
# Integration by parts formula for locally smooth laws and applications to sensitivity computations
1 MATHFI - Financial mathematics
Inria Paris-Rocquencourt, ENPC - École des Ponts ParisTech, UPEC UP12 - Université Paris-Est Créteil Val-de-Marne - Paris 12
Abstract : We consider random variables of the form $F=f(V_1,...,V_n)$ where $f$ is a smooth function and $V_i,i\in\mathbbN$ are random variables with absolutely continuous law $p_i(y).$ We assume that $p_i,i=1,...,n$ are piecewise differentiable and we develop a differential calculus of Malliavin type based on $\partial\lnp_i.$ This allows us to establish an integration by parts formula $E(\partial_i\phi(F)G)=E(\phi(F)H_i(F,G))$ where $H_i(F,G)$ is a random variable constructed using the differential operators acting on $F$ and $G.$ We use this formula in order to give numerical algorithms for sensitivity computations in a model driven by a Lévy process.
Keywords :
Document type :
Reports
Domain :
https://hal.inria.fr/inria-00070439
Contributor : Rapport de Recherche Inria Connect in order to contact the contributor
Submitted on : Friday, May 19, 2006 - 8:29:21 PM
Last modification on : Thursday, February 3, 2022 - 11:18:45 AM
Long-term archiving on: : Sunday, April 4, 2010 - 9:13:34 PM
### Identifiers
• HAL Id : inria-00070439, version 1
### Citation
Vlad Bally, Marie-Pierre Bavouzet, Marouen Messaoud. Integration by parts formula for locally smooth laws and applications to sensitivity computations. [Research Report] RR-5567, INRIA. 2005, pp.54. ⟨inria-00070439⟩
Record views
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https://en.wikiversity.org/wiki/Digital_Electronics/Lecture_number_systems_and_logic_states
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# Digital Electronics/Lecture number systems and logic states
## Overview
This lecture will introduce some basic number system concepts and introduce number systems useful in electrical and computer engineering.
## The decimal number system
In childhood, people are often taught the fundamentals of counting by using their fingers. Counting from one to ten is one of many milestones a child achieves on their way to becoming educated members of society. We will review these basic facts on our way to gaining an understanding of alternate number systems.
The child is taught that the fingers and thumbs can be used to count from one to ten. Extending one finger represents a count of one; two fingers represents a count of two, and so on up to a maximum count of ten. No fingers (or thumbs) refers to a count of zero.
The child is later taught that there are certain symbols called digits that can be used to represent these counts. These digits are, of course:
${\displaystyle 0,1,2,3,4,5,6,7,8,9\,\!}$
Ten, of course, is a special case, since it is comprised of two digits.
Before we go deeper, we need a few fundamental definitions.
### Digit
A digit is a symbol given to an element of a number system.
The radix, or base of a counting system is defined as the number of unique digits in a given number system.
Back to our elementary example. We know that our hypothetical child can count from zero to ten using their fingers and thumbs. There are ten unique digits in this counting system, therefore the radix of our elementary counting system is ten.
We represent the radix of our counting system by putting the radix in subscript to the right of the digits. For example,
${\displaystyle 3_{10}\,\!}$
represents 3 in decimal (base 10).
Our special case (ten) illustrates a fundamental rule of our number system that was not readily apparent - what happens when the count exceeds the highest digit? Obviously, a new digit is added, to the left of our original digit which is "worth more", or has a higher weight than our original digit. (In reality, there *always* are digits to the left; we simply choose not to write those digits to the left of the first nonzero.)
${\displaystyle 10_{10}=010_{10}=0010_{10}=0000000000000000000000000000000000000010_{10}\,\!}$
When our count exceeds the highest digit available, the next digit to the left is incremented and the original digit is reset to zero. For example:
${\displaystyle 9_{10}+1_{10}=10_{10}\,\!}$
Because we are dealing with a base-10 system, each digit to the left of another digit is weighted ten times higher. Using exponential notation, we can imagine the number 10 as representing:
${\displaystyle 10_{10}=1\times 10^{1}+0\times 10^{0}\,\!}$
${\displaystyle 314_{10}=3\times 10^{2}+1\times 10^{1}+4\times 10^{0}\,\!}$
The fundamentals of decimal arithmetic will not be expanded on in this lecture.
## The binary number system
It is widely believed that the decimal system that we find so natural to use is a direct consequence of a human being's ten fingers and thumbs being used for counting purposes. One could easily imagine that a race of intelligent, six-fingered beings could quite possibly have developed a base-six counting system. From this perspective, consider the hypothesis: the most intuitive number system for an entity is that for which some natural means of counting exists.
Since our focus is electronic and computer systems, we must narrow our focus from the human hand to the switch, arguably the most fundamental structure that can be used to represent a count.
The switch can represent one of two states; either open, or closed. If we return to our original definition of a digit, how many digits are required to represent the possible states of our switch? Clearly, the answer is 2. We use the binary digits zero and one to represent the open and closed states of the switch.
### Counting in Binary
Counting in binary like base 10 can be accomplished with your fingers with some differences. In decimal base 10 each finger represents a number in the first digit 1, 2, 3, 4, 5, 6, 7, 8, 9 ,10 . When counting in binary each finger represents a separate digit so counting is more like this.
each number is a finger
dont use thumbs for binary
value decimal binary
right left
hand hand
4
fingers
0 00000 00000 0000
1 00000 01000 0001
2 00000 01100 0010
3 00000 01110 0011
4 00000 01111 0100
5 00000 11111 0101
6 00010 11111 0110
7 00110 11111 0111
8 01110 11111 1000
9 11110 11111 1001
10 11111 11111 1010
WHOA, hold on, that pattern doesn't make sense? Well when you consider that each digit in binary is worth 2 times more than the previous (right to left always) then it makes sense. Lets compare number lines.
binary 128 ,64 ,32 ,16 ,8 ,4 ,2 ,1 decimal 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 ,....
TO BE CONTINUED
### Bits and bytes
A bit is a digit in the binary counting system.
A nybble (also spelled nibble) is a binary number consisting of four bits.
A byte, or octet is a binary number consisting of eight bits.
From our earlier definition of radix, the binary system has a radix of two. We use the radix in the subscript much like we do with decimals:
${\displaystyle 0110_{2}\,\!}$
### Counting
Similar to decimals, binary digits are weighted. Each bit is weighted twice as much as the bit to the right of it:
${\displaystyle 0110_{2}=0\times 2^{3}+1\times 2^{2}+1\times 2^{1}+0\times 2^{0}\,\!}$
Counting from one to ten (base 10) in binary yields:
${\displaystyle 0001_{2},0010_{2},0011_{2},0100_{2},0101_{2},0110_{2},0111_{2},1000_{2},1001_{2},1010_{2}\,\!}$
### Basic binary arithmetic
Binary addition, subtraction, multiplication and division operations work essentially the same as they do for decimals.
${\displaystyle 0100_{2}+0111_{2}\Rightarrow {\begin{matrix}&&0100\\&+&{\underline {0111}}\\&=&1011\end{matrix}}\,\!}$
As you can see, a carry is generated in the ${\displaystyle 2^{2}\,\!}$ column which increments the ${\displaystyle 2^{3}\,\!}$ column.
Subtraction works just like decimal arithmetic, using borrowing as required.
${\displaystyle 1011_{2}-0111_{2}\Rightarrow {\begin{matrix}&&1011\\&-&{\underline {0111}}\\&=&0100\end{matrix}}\,\!}$
Here, a borrow is required, reducing the ${\displaystyle 2^{3}\,\!}$ column to ${\displaystyle 0-0=0\,\!}$ and changing the ${\displaystyle 2^{2}\,\!}$ column to ${\displaystyle 2-1=1\,\!}$.
Multiplication is straightforward also:
${\displaystyle 1011_{2}\times 0111_{2}\Rightarrow {\begin{matrix}&&\;\;\;\;\;\;1011\\&\times &{\underline {\;\;\;\;\;\;0111}}\\&&\;\;\;\;\;\;1011\\&&\;\;\;\;10110\\&&{\underline {\;\;101100}}\\&=&1001101\\\end{matrix}}\,\!}$
Division is left as an exercise to the student [hint: use long division].
### Conversion between binary and decimal
When you consider a binary number in exponential form, you can easily perform a decimal conversion:
${\displaystyle 0110_{2}=0\times 2^{3}+1\times 2^{2}+1\times 2^{1}+0\times 2^{0}\,\!}$
${\displaystyle 0\times 2^{3}+1\times 2^{2}+1\times 2^{1}+0\times 2^{0}=0+4+2+0=6\,\!}$
To convert from decimal to binary, you can repeatedly divide the decimal by two until the result of the division is zero. Starting from the rightmost bit, write 1 if the division has a remainder, zero if it does not. For example, to convert the decimal 74 into binary:
* 74 / 2 = 37 remainder 0; -> 0
* 37 / 2 = 18 remainder 1; -> 10
* 18 / 2 = 9 remainder 0; -> 010
* 9 / 2 = 4 remainder 1; -> 1010
* 4 / 2 = 1 remainder 0; -> 01010
* 2 / 2 = 1 remainder 0; -> 001010
* 1 / 2 = 0 remainder 1; -> 1001010
${\displaystyle 1001010_{2}=1\times 2^{6}+1\times 2^{3}+1\times 2^{1}=64+8+2=74\,\!}$
## The octal number system
The name octal implies eight, if you consider that an octagon has eight sides. Octal has a radix of eight, and uses the following octal digits:
${\displaystyle 0,1,2,3,4,5,6,7\,\!}$
An octal number has the subscript 8.
### Counting
Counting from one to ten (base 10) in octal yields:
${\displaystyle 01_{8},02_{8},03_{8},04_{8},05_{8},06_{8},07_{8},10_{8},11_{8},12_{8}\,\!}$
### Octal arithmetic
Octal arithmetic, like binary arithmetic, follows the same rules and patterns of decimal arithmetic. As an exercise, verify the following:
${\displaystyle 32_{8}+56_{8}=110_{8}\,\!}$
${\displaystyle 32_{8}\times 56_{8}=2254_{8}\,\!}$
${\displaystyle 52_{8}/25_{8}=2_{8}\,\!}$
### Conversion between binary and octal
Each octal digit is representable by exactly three bits. This becomes obvious when you consider that the highest octal digit is seven, which can be represented in binary by ${\displaystyle 111_{2}\,\!}$.
To convert a binary number to octal, group the bits in groups of three starting from the rightmost bit and convert each triplet to its octal equivalent.
${\displaystyle 100010011101_{2}=(100\ 010\ 011\ 101)_{2}=(4\ 2\ 3\ 5)_{8}=4235_{8}\,\!}$
To convert an octal number to binary, simply write the equivalent bits for each octal number.
${\displaystyle 752_{8}=(111\ 101\ 010)_{2}=111101010_{2}\,\!}$
### Conversion from decimal to octal
The repeated-division method described for binary will also work for octal, simply by changing the divisor to eight. To convert 67 (base 10 into octal):
* 67 / 8 = 8 remainder 3; -> 3
* 8 / 8 = 1 remainder 0; -> 03
* 1 / 8 = 0 remainder 1; -> 103
${\displaystyle 67_{10}=103_{8}\,\!}$
The most commonly-used number system in computer systems is the hexadecimal, or more simply hex, system. It has a radix of 16, and uses the numbers zero through nine, as well as A through F as its digits:
${\displaystyle 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F\,\!}$
Hex numbers can have the subscript 16, but more often have a leading *0x* to indicate their type.
${\displaystyle 0x0B45\,\!}$
### Counting
Counting from zero to twenty (base 10) in hex yields:
${\displaystyle 0x0,0x1,0x2,0x3,0x4,0x5,0x6,0x7,0x8,0x9,0xA,\,\!}$ ${\displaystyle 0xB,0xC,0xD,0xE,0xF,0x10,0x11,0x12,0x13,0x14\,\!}$
Hex arithmetic, yet again, follows the same rules and patterns of decimal arithmetic. As an exercise, verify the following:
${\displaystyle 32_{16}+56_{16}=88_{16}\,\!}$
${\displaystyle 32_{16}\times 56_{16}=10CC_{16}\,\!}$
${\displaystyle 4A_{16}/25_{16}=2_{16}\,\!}$
### Conversion between hexadecimal and binary
Each hex digit is representable by exactly four bits. This becomes obvious when you consider that the highest hex digit represents fifteen, which can be represented in binary by ${\displaystyle 1111_{2}\,\!}$.
To convert a binary number to hex, group the bits in groups of four starting from the rightmost bit and convert each group to its hex equivalent.
${\displaystyle 10001111_{2}=(1000\ 1111)_{2}=(8\ F)_{16}=8F_{16}\,\!}$
To convert an hex number to binary, simply write the equivalent bits for each hex number.
${\displaystyle 7D_{16}=(0111\ 1101)_{2}=01111101_{2}\,\!}$
## Representing Logic States
high 1 or onlow 0 or off
X 100M
X 100K
X 100
X 100m
X 100μ
Ω
A
DC
AC
C L
X 100M
X 100K
X 100
X 100m
X 100μ
Ω
A
DC
AC
C L
VCC to Vhigh in = logic high
vlow in to gnd = logic low
technology CMOS TTL/CMOS TTL LVTTL LVCMOS
technology type AC, HC, AHC, H ACT, HCT, AHCT, FCT F, S, AS, LS, ALS LV LV, LVC, ALVC
vcc 5v 5v 5v-4.5v 3.6v-3v 3.6v-3v
vhigh Out 4.7v 4.7v 3.3v or 2.4v 2.4v 3.5v
vhigh In Min 3.7v 2.0v 2.0v 2.0v 2.6v
transition
vlow In Max 1.3v .8v .8v .8v .72v
vlow Out .2v .2v .35v .4v .54v
Most 5v logic will have no problem with a 5V high or a 0V low. You should always refer to the data sheet before choosing your device.[1]
The range in between "vhigh lower" and "vlow higher" should be avoided and as little time as possible should ever be spent here.
## Exercises
1. Convert the following binary numbers to decimal:
${\displaystyle i)1001_{2},ii)11001010_{2},iii)101011111\,\!}$
2. Convert the following decimal numbers to binary:
${\displaystyle i)102_{10},ii)432_{10},iii)7654\,\!}$
${\displaystyle i)1010_{2}+1100_{2}\,\!}$
${\displaystyle ii)165_{8}+544_{8}\,\!}$
${\displaystyle iii)0x29AB+0x567\,\!}$
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https://blender.stackexchange.com/questions/9379/hiding-all-but-the-selected-objects
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# Hiding all but the selected objects?
I was doing my best to follow this tutorial from the Blender Guru, but, alas, 8 minutes in I've run into a real spot, a few moments after this spot in the video.
I can only hide the selected, not hide all BUT the selected. (Edits then effects ONLY the selected vertices.) I know, there is a way to invert selection, but it doesn't look like he does this.
Also, what does he mean do he says, "This is not perfectly aligned..."
You can hit Shift+H, this works for all areas of blender which support hiding (editmode, uv-editing, sequencer... etc).
In Blender, if you know the the basic action a key is assigned to such as (hide H), you can try different combinations with Shift, Ctrl or Alt to often perform the inverse.
• I tried this, and it's great, there's just one problem - how do you unhide all, once that you're done? Tried Shift, Ctrl and Alt +H, didn't help... – sdaau Sep 19 '14 at 1:16
• unhide is Alt + H – Leon95 Oct 4 '14 at 12:51
For completeness; you could also switch the View from Global to Local by pressing Numpad-/ for selected objects. This is also accessible from the Menu: View>Global/Local.
From the documentation:
Note that the layer and lock buttons on the 3D View header disappear while in local view.
He manually selects the bottom of the glass with border select (B) and then hides it (H), then does the same for the edge loop above.
Note that he has Screencast keys enabled, so you can see exactly what he does:
A: Deselect all
B: Border select
H: Hide
For flattening the mesh, he does SZ0 to set everything selected to the same position along the Z. See How to align a cluster of points?
Other guys have shared you with some very nice tips on hiding. However, I want to point out the key problem that is puzzling you now.
• Andrew didn't "hide all BUT selected". In fact, he just simply hided all vertices on that circle loop by hitting H. The reason why it appears that everything else was hidden is:
1. He didn't show the complete view of the whole bottle during the following seconds. In fact, the top of the bottle is still there. You can confirm it around 08:53.
2. Furthermore, when in Edit Mode with Wireframe display, the Subdivision results generated by SubSurf modifier will be always shown, regardless the visibility of elements on the base object. That's why you cannot see them anymore after he hit Z to switch to Solid view.
• About your last word, I didn't notice he ever said anything like "This is not perfectly aligned..." Can you provide the exact moment in that video?
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http://math.stackexchange.com/questions/427200/method-for-solving-ode-with-power-series
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# Method for solving ODE with power series
when trying to solve second order linear homogeneous variable coefficient ODEs using a power series method, there seem to be two different general forms cropping up in my notes. The first uses an ordinary point $$x_0$$ $$y = \sum_{m = 0}^{\infty}a_m(x-x_0)^m$$ The second uses a factor of $$x^r$$ $$y = x^r\sum_{m = 0}^{\infty}a_mx^m$$
How do I know which of these forms to use for my solution?
-
The second is always more general, i.e. if $r=0$ then you'll just recover the first ansatz. – Pedro Tamaroff Jun 22 '13 at 22:48
but if I have limited time (like in an exam) how can I tell if I can use the first one because that would save time? – Sam Jun 22 '13 at 23:15
The second solution can also be "centered" at $x_o$ by replacing $x$ with $x-x_o$ in the second formula. However, the convergence will only occur to the left or right of the singular point in considering the real interval of convergence. – James S. Cook Jun 22 '13 at 23:36
Your first solution is a power series. Your second solution is the Frobenius solution which allows for $r$ non-integer. There are 4 cases to consider for the second solution. The way in which the second solution is found differs slightly if:
1. you have distinct exponents which do not differ by an integer
2. you have distinct exponents which do differ by an integer
3. you have repeated exponents
4. you have complex exponents
The simplest example illustrating these is the Cauchy-Euler problem $ax^2y''+bxy'+cy=0$ which is the quintessential example of a second order ODE with a regular singular point.
To answer your question, if you seek a solution at an ordinary point use the power series solution. If you face a regular singular point then invoke the method of Frobenius.
-
I know there is a different method for solving Euler-Cauchy equations, but if I didn't recognise a problem as being an Euler-Cauchy equation, could I use either the power series or frobenius method and still come up with the correct answer? – Sam Jun 23 '13 at 10:04
@Sam You look at $ar(r-1)+br+c=0$ for the Cauchy-Euler problem I mentioned in my post. This is the indicial equation from the Frobenius method. The wonderful thing about the Cauchy-Euler problem is that the rest of the Frobenius series vanishes. You just get the lowest order terms for the Frobenius solution. Sort of like solving $y^{n}(x)=0$ with a power series ansatz, it's a bit of an overkill since clearly an $n$-th order polynomial will do nicely. (well, just integrate $n$-fold times for that silly example) – James S. Cook Jun 23 '13 at 17:43
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|
https://www.eevblog.com/forum/blog/eevblog-411-minipro-tl866-universal-programmer-review/1525/
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### Author Topic: EEVblog #411 - MiniPro TL866 Universal Programmer Review (Read 974752 times)
0 Members and 4 Guests are viewing this topic.
#### Wiljan
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1525 on: February 20, 2019, 06:52:16 pm »
I have the TL866II plus and thank you for the link to thehttp://proghq.org/wiki/TL866_II_PLUS nice information on the bootloader
Regarding the PIC24FJ256GB110 I just tried to Read it out with with my PicKit3 and if does match the chip ID and does complete the read out ...unfortunately all the data are = 0x00 which mean the PIC are Read protected.
Code: [Select]
Currently loaded firmware on PICkit 3Firmware Suite Version.....01.40.13Firmware type..............dsPIC33F/24F/24HProgrammer to target power is enabled - VDD = 3,250000 volts.Target device PIC24FJ256GB110 found.Device ID Revision = 4The following memory area(s) will be read:program memory: start address = 0x0, end address = 0x2abf7configuration memoryReading...Read complete2019-02-20T19:34:59+0100- Read complete
I'am still on 8.01 since it loose USB connection each time I try to update the firmware
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#### xoom
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1526 on: February 21, 2019, 08:33:03 am »
is there sop44 adapter reverse engineered?
i also wondering if i can use software from http://www.autoelectric.cn/en/ page (8.30) as software provided with CD is 7.30 ?
« Last Edit: February 21, 2019, 09:11:45 am by xoom »
#### james38
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1527 on: February 21, 2019, 06:45:09 pm »
If you mean the Attiny13 chip on the TSop48 look here.
https://www.eevblog.com/forum/blog/eevblog-411-minipro-tl866-universal-programmer-review/msg936055/#msg936055
About the Software. Why not?
The software on CD is very old and i believe that it will be never updated.
I have running V8.30 without problems.
Be sure you must update the Firmware at once but that procedure runs also without problems.
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#### leonardovenpin
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1528 on: February 26, 2019, 08:52:55 am »
Excuse me, does anyone know what peak-to-peak voltage I should put to program an ATF16v8B on a tl866A?
#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1529 on: February 26, 2019, 10:16:59 am »
Excuse me, does anyone know what peak-to-peak voltage I should put to program an ATF16v8B on a tl866A?
Why would you need to change the voltage settings? The ATF16V8B is available as a predefined part in the TL866 software, if I remember correctly. Just select it and program away!
#### james38
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1530 on: February 26, 2019, 07:08:20 pm »
I know what he mean.
When you select the ATF16v8B you have also the ability to select a VPP voltage.
Predefined is 12,50V.
You can select then between 10.0V until 21.00V.
The Datasheed says that the programming voltage with respect to ground can be -2.0V to +14.0V
So in this case try the default with 12,5V but not over 14V.
#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1531 on: February 26, 2019, 07:40:47 pm »
When you select the ATF16v8B you have also the ability to select a VPP voltage.
Predefined is 12,50V.
You can select then between 10.0V until 21.00V.
The Datasheed says that the programming voltage with respect to ground can be -2.0V to +14.0V
So in this case try the default with 12,5V but not over 14V.
Thank you for checking the TL866 software and the datasheet. But please note that the -2V to +14V you state are the "absolute maximum ratings", i.e. the range where you won't damage the device. Nowhere does the datasheet say that voltages in this wide range are suitable for programming. The nominal programming voltage is not stated in the datasheet.
Hence, @leonardovenpin:
Simply don't mess with the 12.5V default value! Autoelectric will either have found out the specified voltage from Atmel or other sources, or have determined it through experimentation. Why would your guess be better than theirs?
#### james38
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1532 on: February 26, 2019, 09:56:00 pm »
Yes your are right.
This values are absolute max values.
The overshoot is +7V for pulses of less than 20 ns.
It's a little bit suspicious that in the datasheet they don't declare the correct nominal programming voltage.
Also google says nothing about the voltage.
Seems that its a very guarded secret. ;-)
I only found some Basics for general Gals like 16V8.
Put 12V on Edit to set the Gal in Programming Mode and a slight higher Voltage on the Pins for programming.
Now i am a little bit confused what is the right voltage.
So in this case 12.5V could be already to high.
Maybe I can still find some information about the right Vpp.
#### oPossum
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• The other white meat.
##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1533 on: February 26, 2019, 10:15:45 pm »
The programming voltage is part of the programming specification that is a separate document from the general data sheet.
Don't change the default voltages selected by the TL866.
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#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1534 on: February 26, 2019, 10:30:22 pm »
The programming voltage is part of the programming specification that is a separate document from the general data sheet.
Which, in this case, is another way of saying it's a well-kept secret.
Thank you for repeating that one should not fiddle with the programming voltage pre-set by the TL866. I did not dare repeating it a third time... I can certainly confirm the the default value of 12.5V worked well for me; although 12.0V would probably work just as well. (If the TL866 even offers that value?)
#### james38
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1535 on: February 26, 2019, 10:41:02 pm »
The next lower Vpp is 10.00V (it is also the lowest Value you can select).
The next higher is 13.50V from the predefined 12.5V
#### leonardovenpin
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1536 on: February 28, 2019, 09:09:34 pm »
What happens is that when I do a combinational circuit (which does not require a clock), I program it well tl866 but when I want to program a sequential circuit (which uses a clock), the PLD does not work and I simulate it in a diagram time of the same software (ispLEVER Classic) and it works.
So I simulate it in Proteus using the JEDEC file and it works.
and I thought it was because of the "VPP", which in the case of combinational circuits only works with 10Vpp.
help me solve it! : '(
I do not know if I have to see that the algorithm to use the GAL16V8D clock is not the same as that of ATF16V8B
#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1537 on: February 28, 2019, 10:29:24 pm »
I am note sure I fully understand. Could you please clarify the following?
I thought it was because of the "VPP", which in the case of combinational circuits only works with 10Vpp.
Do you mean that the TL866 software sets a different VPP when you program a GAL in combinatorial vs. registered (clocked) mode?! That can't be; the voltage setting is not influenced by the content of the JEDEC file, right?
Quote
I do not know if I have to see that the algorithm to use the GAL16V8D clock is not the same as that of ATF16V8B
From your prior post, I assumed that you are programming an ATF16V8B, and are using the ATF16V8B setting in the TL866 software. Is that right? If so, what does the 16V8D have to do with it?
#### leonardovenpin
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1538 on: February 28, 2019, 11:13:37 pm »
What happens that I use
"ispLEVER Classic" to do the vhdl thing, and it asks me which device I'm going to use, and it only gives me to choose from the GAL family, which is obvious because the software is from Lattice, so, according to me, I select the more similar (GAL16V8D) to my device (ATF16V8B).
When I make a circuit that does not require "Flip Flops", it works well when programming it with the tl866A, but when I use the Flip Flops it does not work anymore.
for example:
- an adder works
- a multiplexer works
- a decoder works
- a Flip Flop type D, JK, RS or T does not work
- a counter does not work
and it is that the software puts me automatic in port one for the clock, but it does not work when programming it, but in the simulators that I mention, yes.
#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1539 on: February 28, 2019, 11:24:53 pm »
The ATF16V8 should be logically equivalent to the Lattice 16V8, so the generated JEDEC file should be directly compatible. And I am pretty sure that your problem has nothing to do with the programming voltage either, if things work fine in combinatorial mode.
So it could be some error in your VHDL, and/or a mismatch of the boundary conditions between the simulation vs. real world. Difficult to diagnose remotely... A few ideas come to mind:
- Do you have a clean supply voltage in your real-world test?
- Do you have a 100nF capacitor across Gnd and Vcc?
- Do you have a clean CLK signal?
- Have you grounded the /OE pin (pin 11)?
#### leonardovenpin
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1540 on: March 01, 2019, 01:40:46 am »
I used an NE555 as a clock, I use a steren source and I have it at 5V, should I put a capacitor between the power terminals, should I put EO on the ground?
#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1541 on: March 01, 2019, 01:49:24 am »
should I put EO on the ground?
In GAL registered mode, all outputs operate in tristate mode, and all are controlled by a common output enable.
So yes, the /OE input on pin 11 needs to be pulled to GND, otherwise the outputs will remain in high impedance state.
#### leonardovenpin
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1542 on: March 01, 2019, 01:55:55 am »
When to use the watch, then, in automatic it is put in pin 11 as port as OE?
#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1543 on: March 01, 2019, 02:15:35 am »
When to use the watch, then, in automatic it is put in pin 11 as port as OE?
Sorry, I am not sure I understand that sentence. In registered mode of the GAL, pin 11 is always configured as /OE. It’s described in the datasheet.
(By the way: Note the / character which I keep writing, and you keep omitting. It means that the signal is „active low“.)
#### texaspyro
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1544 on: March 01, 2019, 02:32:09 am »
The ATF16V8 should be logically equivalent to the Lattice 16V8, so the generated JEDEC file should be directly compatible.
Not necessarily... when I was using GALs, ages ago, I ran into some issues where various makers of GALs did not have compatible fuse maps. You could not program BrandX's devices with BrandY's JEDEC file.
#### leonardovenpin
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1545 on: March 01, 2019, 07:59:33 pm »
hank you very much friend, that was the problem, the output was disabled, by the way, if I understood your reference, I know that / OE was that the entry was "denied", nothing more than I always represent it in text like this: (OE)' hehe
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#### ebastler
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1546 on: March 01, 2019, 08:07:13 pm »
Thank you for the feedback, Leonardo -- glad you got it to work!
(And glad we could confirm that the TL866 handles ATF16V8 GALs nicely, simply using the default settings!)
#### BrianG61UK
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1547 on: March 01, 2019, 10:51:41 pm »
The ATF16V8 should be logically equivalent to the Lattice 16V8, so the generated JEDEC file should be directly compatible.
Not necessarily... when I was using GALs, ages ago, I ran into some issues where various makers of GALs did not have compatible fuse maps. You could not program BrandX's devices with BrandY's JEDEC file.
I've never seen that, but maybe that can happen on larger more complex GALs.
You can of course have a function in a circuit that can be implemented in either a PAL or a GAL and then there will need to be different JEDEC files, one for the PAL version and a bigger one for the GAL version.
Sent from my SM-N9005 using Tapatalk
#### ChrisG
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1548 on: March 03, 2019, 12:07:50 pm »
Hi Radioman, I'm stuck after re-applying your instructions twice. I did convert my original (by the looks of the images etc) from CS to A a long time ago. Perhaps I'm doing things wrong and my update.dat file is not the right one? How can I check this or get a good one? The result I have so far is that when using the V6.85 software it immediately says to reflash, which it claims is successful, but does not I believe.
One silly question I do have what bootmode on this device is. I did solder the resistor and was able to flash (according to the success messages)
I've added the screenshots in a pdf document.
p.s.: I did read the Djomano super clear pictorial instructions once more and went to flash as a TL866A but constantly get the message upon plugging in or starting minipro 6.85v to go to : Main Menu -> Tools -> Flash Firmware
Appreciate the help on trying to identify where I'm going wrong. Again I have no idea on my update.dat file version
« Last Edit: March 03, 2019, 12:28:46 pm by ChrisG »
#### landsfiskalen
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##### Re: EEVblog #411 - MiniPro TL866 Universal Programmer Review
« Reply #1549 on: March 03, 2019, 01:13:51 pm »
Hi,
I also did the firmware conversion from CS to A a few years ago. And when I tried to install v6.85 of the software it told me it was a converted CS bla bla bla, and refused to start. So i tried radiomans guide of reflashing the firmware. I soldered the resistor and managed to get the Firmware updater running (v2.51), I did all the steps and flashed it with the 6.82 update.dat file. It looked like everything went ok, and I didn't get any errors. But when I tried to start the v6.82 software I got a "IC List Dll file error!" and it refuses to start. So I thought I'd do it all over again. So I soldered back the resistor and tried to get it back into bootloader mode. But now Firmware updater won't find my device, it just says "0 devices connected". So I tried once more, but with the same result. Any ideas on what to try next? Any help is greatly appreciated.
Smf
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http://mathhelpforum.com/calculus/219101-drawing-vertical-line-through-circle-find-what-x-does-vertical-line-div.html
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# Thread: Drawing vertical line through a circle to find for what x does that vertical line div
1. ## Drawing vertical line through a circle to find for what x does that vertical line div
Hi all, I would appreciate some help with the problem:
The problem state: "A building design consultant is going to make a 14 foot diameter windowwith a vertical cut through the glass so that 2/3 of the glass can be tinted. Wheres should this cut be made?"
As you can see in the above attachment, I was able to conclude into some sort of equation, but when I solve that equation to 49*pi/3 via wolfmath, I got about 6.83 = x, which does not make sense because the radius is 7 and that wouldn't be 1/3 if you draw the vertical line through it to divide the circle.
If you could help me out, I would really appreciate it.
Thank you,
2. ## Re: Drawing vertical line through a circle to find for what x does that vertical line
First note that the area of this circle would be \displaystyle \begin{align*} \pi \cdot 7^2 = 49\,\pi \textrm{ units}\, ^2 \end{align*}
If we place the circle on a set of axes centred at the origin, it has equation \displaystyle \begin{align*} x^2 + y^2 = 7^2 \end{align*} then draw in the vertical line \displaystyle \begin{align*} x = a \end{align*} somewhere to the right of the y-axis, we wish to know what value of x this is so that it splits the circle into areas in the ratio 2:1. So that means the area bounded between this line and the circle on the right will be \displaystyle \begin{align*} \frac{49 \, \pi}{3} \,\textrm{units}\,^2 \end{align*}, and since this is evenly distributed above and below the x-axis, the area above the x-axis is \displaystyle \begin{align*} \frac{49 \, \pi }{6} \, \textrm{units} \, ^2 \end{align*}.
So we can set up an integral for the area bounded by the circle, the x-axis and the vertical line \displaystyle \begin{align*} x = a \end{align*} as \displaystyle \begin{align*} A = \int_a^7{ \sqrt{ 49 - x^2 } \, dx } \end{align*}.
Equating this to the known area we have \displaystyle \begin{align*} \int_a^7{ \sqrt{ 49 - x^2 } \, dx } &= \frac{ 49 \, \pi }{ 6} \end{align*}.
In order to evaluate this integral and solve for the value of a, we need to make a trigonometric substitution \displaystyle \begin{align*} x = 7\sin{(\theta)} \implies dx = 7\cos{(\theta)}\,d\theta \end{align*} and note that when \displaystyle \begin{align*} x = a , \theta = \arcsin{ \left( \frac{a}{7} \right) } \end{align*} and when \displaystyle \begin{align*} x = 7 , \theta = \frac{\pi}{2} \end{align*}. Substituting gives
\displaystyle \begin{align*} \int_{\arcsin{ \left( \frac{a}{7} \right) } } ^{ \frac{\pi}{2} } { \sqrt{ 49 - \left[ 7\sin{(\theta)} \right] ^2 } \cdot 7\cos{(\theta)}\,d\theta } &= \frac{49\,\pi}{6} \\ 7 \int_{\arcsin{ \left( \frac{a}{7} \right) } }^{\frac{\pi}{2}} { \sqrt{ 49 \left[ 1 - \sin^2{ ( \theta ) } \right] } \cos{ ( \theta) } \, d\theta } &= \frac{49 \, \pi }{6} \\ 7 \int_{ \arcsin{ \left( \frac{a}{7} \right) } }^{ \frac{ \pi }{ 2 } }{ 7\cos^2{(\theta)}\,d\theta } &= \frac{ 49 \, \pi}{6} \\ \frac{ 49 }{2} \int_{ \arcsin{ \left( \frac{a}{7} \right) } }^{ \frac{ \pi }{2}}{ 1 + \cos{ (2\theta)} \,d\theta } &= \frac{ 49 \, \pi }{6} \\ \int_{\arcsin{\left( \frac{a}{7} \right) }}^{\frac{\pi}{2}}{1 + \cos{(2\theta)}\,d\theta} &= \frac{\pi}{3} \\ \left[ \theta + \frac{1}{2}\sin{(2\theta)} \right] _{\arcsin{\left( \frac{a}{7} \right) } }^{\frac{\pi}{2}} &= \frac{\pi}{3} \end{align*}
\displaystyle \begin{align*} \left[ \frac{\pi}{2} + \frac{1}{2} \sin{ \left( 2 \cdot \frac{\pi}{2} \right) } \right] - \left\{ \arcsin{ \left( \frac{a}{7} \right) } + \frac{1}{2} \sin{ \left[ 2\arcsin{ \left( \frac{a}{7} \right) } \right] } \right\} &= \frac{\pi}{3} \\ \frac{\pi}{2} - \arcsin{ \left( \frac{a}{7} \right) } - \sin{ \left[ \arcsin{ \left( \frac{a}{7} \right) } \right] } \,\sqrt{ 1 - \sin^2{ \left[ \arcsin{ \left( \frac{a}{7} \right) } \right] } } &= \frac{\pi}{3} \\ -\arcsin{ \left( \frac{a}{7} \right) } - \frac{a}{7} \, \sqrt{ 1 - \left( \frac{a}{7} \right) ^2 } &= \frac{\pi}{3} - \frac{\pi}{2} \\ -\arcsin{ \left( \frac{a}{7} \right) } - \frac{a}{7} \, \sqrt{ \frac{49 - a^2}{49} } &= -\frac{\pi}{6} \\ \arcsin{ \left( \frac{a}{7} \right) } + \frac{ a \, \sqrt{ 49 - a^2 }}{49} &= \frac{\pi}{6} \end{align*}
Unfortunately there is no way to evaluate the value of a here exactly, but you should be able to get a numerical answer using a CAS
3. ## Re: Drawing vertical line through a circle to find for what x does that vertical line
Brilliant! Thank you so much.
4. ## Re: Drawing vertical line through a circle to find for what x does that vertical line
If the ends of a chord drawn in a circle radius $r$ subtend an angle $\theta$ at the centre of the circle, then the area 'cut off' by the chord is $r^{2}(\theta - \sin \theta)/2.$
That means we need $r^{2}(\theta - \sin \theta)/2=\pi r^{2}/3,$ or, $\theta - \sin \theta=2\pi /3.$
That requires a numerical solution, which turns out to be $\theta = 2.60533.$
For a circle of radius $7,$ it follows that the centre of the chord should be at a distance of $1.8545$ (approx) from the centre of the circle.
5. ## Re: Drawing vertical line through a circle to find for what x does that vertical line
Very well done in fact i was stuck at the same stage. i used the formula ∫▒√(a^2- x^2 ) dx= x/2 √(a^2- x^2 )+ 1/2 sin^(-1)〖x/a〗+c directly the issue remains how to get a ??
6. ## Re: Drawing vertical line through a circle to find for what x does that vertical line
You need to use a numerical method and/or technology such as a CAS. There is no way to isolate a exactly when it's both inside and outside of a transcendental function (unless it's a very special case where a solution sticks out at you).
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http://git.kamailio.org/gitlist/index.php/sip-router/blame/vseva/mod_fix_pvar_3/modules/textops/txt_var.h
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modules/textops/txt_var.h
c9912942 /* 0a35621d * Copyright (C) 2008 Elena-Ramona Modroiu (asipto.com) * * This file is part of kamailio, a free SIP server. * 6c780225 * Kamailio is free software; you can redistribute it and/or modify 0a35621d * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version * 6c780225 * Kamailio is distributed in the hope that it will be useful, 0a35621d * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software 9e1ff448 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 0a35621d */ c9912942 /*! * \file * \brief Regular expressions * \ingroup textops * Module: \ref textops */ 0a35621d #ifndef _TXT_VAR_H_ #define _TXT_VAR_H_ #include "../../pvar.h" enum _tr__txt_type { TR_TXT_NONE=0, TR_TXT_RE }; enum _tr_s_subtype { TR_TXT_RE_NONE=0, TR_TXT_RE_SUBST }; char* tr_txt_parse_re(str *in, trans_t *tr); #endif
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https://motls.blogspot.com/2004/12/theories-are-increasingly-theoretical.html
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## Friday, December 24, 2004 ... //
### Theories are increasingly theoretical
This text follows my discussions with Nima Arkani-Hamed and David Goss.
Some people don't like the fact that the arguments in string theory are increasingly theoretical in nature, and that our theories seem to give us less exactly calculable sharp predictions that are verified experimentally.
However: it's not just string theory: the whole particle physics has been becoming increasingly theoretical and string theory just continues in the same direction. What do I mean?
QED, Electroweak theory, QCD: increasing groups, decreasing accuracy
The peak of the old-fashioned quantitative predictivity of very particular facts in physics was QED which stands for Quantum Electrodynamics. You know that people could have calculated its predictions already 50 years ago, including the quantum loop corrections, even though they did not quite understand why their methods were working (The Renormalization Group), and the most precise predictions - like the anomalous magnetic moment of the electron - have been successfully tested with the accuracy of 13 decimal places!
Then the physicists found the electroweak force that naturally predicted the neutral currents, W bosons, the Z boson, and so forth. It is also a relatively very predictive theory (Glashow, Salam, Weinberg) although its predictions were never tested as exactly as for QED. Nevertheless, all the cross sections and decay rates are measured rather precisely, the electroweak scattering is "clean".
Another step: QCD
Then you go to QCD which is now an accepted and "Nobelized" part of our theoretical canon. QCD, in some sense, confirmed the things people "guessed" by other means, and one might criticize it using some very similar words as those often applied to string theory by its critics.
You know, QCD is claimed to be a theory of the strong force, but it talks about the gluons, quarks, and especially their three colors, three concepts that were never directly seen; and according to QCD no one will ever see either of them. Also, no one has been able to calculate the properties of the proton, neutron, and nuclei - which used to be thought to be the objects from the strong interaction - from this theory too well. The actual calculations often rely on some properties of the quark and gluon distribution functions, and the critics might say that these functions have never been really derived from QCD. Even if one accepts the existence of quarks, they were not really invented by QCD: Gell-Mann received a Nobel prize for quarks in 1969, five years before QCD was proposed. The new quark flavors, such as the c-quark found in the J/psi particle, were naturally predicted by the electroweak theory (the GIM mechanism from 1970), not by QCD. In this respect, QCD seems to have had no "striking" new predictions. So why do we say that QCD is a good theory of the strong interaction?
The low-energy properties of the hadrons have not been calculated accurately enough simply because QCD is a pretty difficult machine to calculate with at low energies - but this difficulty is a fact of Nature. In the same way, the vacuum structure in string theory is also rather complicated, which also seems to be a fact of Nature. At high energies, the quarks are almost free (due to asymptotic freedom, which is really what our friends got their 2004 Nobel prize for). If the quarks are free, perturbation theory is great and one can easily and precisely calculate the high-energy events. But for the effects important for the nuclear physics, the interaction is strong - more or less by definition. QCD is a strongly coupled theory at longer distances. The perturbation theory breaks down and the nonlinear equations of QCD are just very difficult - some progress can be obtained numerically using lattices and some other tools (the AdS/CFT correspondence has become the most powerful new tool).
In this sense, I believe that one could use nearly the same criticism not only against string theory, but also QCD itself. However I feel that it's not hard to realize that in the QCD case, it would be unreasonable. Not only because of the Nobel prize!
So what does QCD predict that makes us sure that it's right? It predicts the jets in the high energy collissions - "dressed" quarks and gluons. But people qualitatively knew about these things experimentally already before QCD, so it was not a real prediction. They also knew about the organization of strongly interacting particles into families (with different composition of quarks, depending on the particular member of the family - i.e. of the multiplet). So this was not a "real" prediction either. QCD was constructed to agree with the scaling laws - it was an input and one of Gross's motivations - but it did not predict much afterwards, as long as one talks about some completely new, visible effects.
The advantage of QCD is claimed to be beauty - it is a nice SU(3) Yang-Mills theory - and the pure QCD has no dimensionless parameters - the same virtue as string theory: the original dimensionless coupling is converted into a dimensionful scale by the dimensional transmutation. Yang-Mills theory seems to be the unique way how to obtain asymptotic freedom (vanishing of interactions at very high energies) from a quantum field theory.
David Gross likes to say that a theory without dimensionless parameters (QCD) can now explain all the "anthropic" mysteries from nuclear physics. Nima Arkani-Hamed correctly points out that it's not quite correct because the various "coincidences" relating the masses of the nucleons etc. depend on all these small parameters like the quark bare masses. Well, I am not terribly happy to admit that Nima's objection is fair because his objection is a small argument in favor of the anthropic thinking. Nevertheless I must admit that Nima is right because he is. ;-)
The success of QCD is that it is really the only theory that explains the data that had been known already before QCD was found - and it's able to put these data into a coherent framework. And it is a very beautiful theory - it has nice symmetries and no dimensionless parameters in its "pure" version. These things were enough for the authors of QCD to know that it was correct as early as in 1975.
We're saying the very same things about string theory. String theory is really the only theory that can agree with the existing facts about quantum field theory but also with physics of general relativity i.e. with gravity. Of course, there is a difference between QCD and string theory is that QCD has given us some new predictions that were unavailable for the previous rules to understand the strong interactions, and these predictions are tested at the 1% accuracy, while string theory is still waiting for the right experiments that will eliminate its critics. Let me be more specific: the 1% accuracy was only achieved in the 1990s, twenty years after the fathers of QCD knew that QCD was correct.
Nevertheless, you see that the character of our theories is evolving in a particular direction - even if we study the evolution within the Standard Model itself. String theory is just one more step in this progression; it certainly implies no "qualitative" change in our understanding what physics theories are good for. We're marching towards more strongly coupled - and more difficult to calculate - theories that may look "richer" but that are also increasingly more constrained, and we are using increasingly complex mathematics - and the observations about the uniqueness of the consistent solutions of our problems - as our arguments. It is happening simply because the naive, simple math that can be easily calculated and compared with the experiments was already calculated a long time ago.
As our theories become more mathematical and abstract - which is a necessary process, as I tried to explain - the number of the people who actually understand the logic behind these new steps decreases. Not too many "ordinary" people understand relativity; quantum mechanics is even more difficult for most physics fans. Quantum field theory requires a special training, among other things, and in the case of string theory it is simply true that a PhD degree from theoretical physics is not a sufficient condition to understand the inevitability of its claims. I agree with the critics of string theory that a theoretical physics PhD should be enough to understand string theory, but my ideas how to achieve this goal are very different from theirs. ;-)
As our theories are becoming more mathematical, we are simultaneously revising the concepts dramatically and we are finding new connections between the previous concepts, and their limitations that looked impossible previously. The latter was happening in every revolution of physics, including the quantum revolution.
So I don't really understand what is it exactly that makes so many people feel so uneasy about string theory and why. Of course, I understand why people may be frustrated that the progress is slow, but it's harder to see how can string theory be blamed for it. Where we're going - in the perspective of a decade or so - is arguably the right way, and all philosophical properties and trends of this progress agree with what has been proved fruitful in the past and recently.
Much of the recent progress, including the construction of QCD, was about pushing "reductionism" as far as we can. We could not be satisfied with a list of 200 strongly interacting "elementary" particles and their messy interactions; people eventually convinced themselves that the right elementary particles are quarks (and gluons), although the hadrons remain a good description at low energies. In a similar fashion, we cannot be satisfied with the list of the elementary particles of the Standard Model plus the graviton, whose interactions furthermore don't work at the loop level, and this is why we are happy to reduce these concepts further to the level of strings (and their non-perturbative friends) - because this reduction seems possible which is itself a shocking, nontrivial fact. Again, the previous language of low-energy effective theories remains good at long distances.
String theory marvellously has all the desired qualitative features and the quantitative power to explain everything we know about the real world, and we know that the unification of quantum field theories with gravity is a very difficult task and a generic proposed theory usually solves nothing at all, while string theory seems to solve a lot. This is why we "know" that string theory is probably correct, even though it may take decades or even centuries to convince the critics. But the situation is qualitatively analogous to QCD. The difference is that string theory is even more dependent on theoretical arguments than QCD, and it works with much higher energy scales. But there is no qualitative phase transition in the definition of physics!
We may be unhappy about the particular developments in the last 1 year or perhaps even 5 years or something like that. But every time I see what the alternatives could be, it reassures me that we are on the right track. The alternatives usually want to return science at least 40 years into the past, and perhaps to the 19th century.
It's hard to convince anyone about the analogy if he or she does not feel it this way, but let me try anyway. There are creationists who reject evolution. Let's call them the 1860 crackpots. There are people who reject special relativity, right? Let's call them the 1905 crackpots. Some of these insist on the luminiferous aether (even though some of them may call it spin foam). Then there are people that reject general relativity, the 1916 crackpots, and quantum mechanics, the 1926 crackpots. Then there are thinkers who reject the (divergent) loop diagrams and their regularization; let's call them the 1949 crackpots, and who reject quarks, who are called the 1973 speculative colleagues.
As I go towards the present, physics of these topics becomes increasingly difficult, requires higher education, expertise - and I think that something remotely similar exists in any other sufficiently complex field of science, including e.g. number theory, too. Proving the Fermat Last Theorem is a pretty fancy thing that requires some new technology, does not it?
The people who reject our understanding collected in the last 20 years that string theory is the only way to exceed the limitations (and repair the divergent behavior) of quantum field theory and classical GR - and who reject hundreds of the particular more detailed insights about string theory and quantum field theory that we've made and we will never unlearn - are, of course, not quite as clear crackpots as the previous categories because they only failed to follow (or decided to deny) the last 20 years and the questions studied by string theory are still "work in progress". But ignoring these insights still seems as a pretty bad starting point for making contributions to physics - or trying to direct physics - in 2004.
What I find more obvious is that the people who want to ignore string theory actually want to neglect some older, well-established insights as well - the renormalization group, semiclassical gravity (of Hawking), and others - perhaps even perturbation theory or the S-matrix as the important concepts in quantum relativistic physics.
One may ask why I feel so sure that string theory is most likely on the right track. It is a combination of both aspects: the impressive power of string theory demonstrated in many contexts, but also the naive picture of physics that the proponents of "alternatives" want to advocate. One must always choose some principles when he or she tries to go beyond the known realm. But the non-stringy people in physics just generally choose principles that look very simple-minded and obsolete. It's pretty hard to explain non-technically and exactly why I almost always feel so certain about it. I understand why the people feel that my certainty looks like "religion" - it would also look like religion to me if I did not know most of the things I know, or if they were not organized in my brain the same way.
Aether, hidden variables: repeating the errors forever
But it's like if you remember some error that you did 15 years ago, and you later understood perfectly why it was silly and how your viewpoint on the problem was uninformed and narrow-minded and 19th-century-like (or perhaps it was not you, just some other people around). Today, you may understand that all your confusion 15 years ago was unjustified, and that there exists a completely meaningful and rigorous answer to all your questions you had - and these answers are often different than you thought. Also, you may realize today that you used to neglect a huge amount of important knowledge - you were just too ignorant about too many things - which invalidates all your previous reasoning.
And suddenly, 15 years later, someone comes with the same or even more unlikely approach and claims that it is an important idea that is meant to revolutionize physics.
Like those loop quantum gravity people. Most of them probably don't know that Maxwell did not write just his equations; he constructed a few discrete models of aether. George FitzGerald even constructed working models of such an aether that produced the transverse electromagnetic waves! And this model really worked. Such problems involving gears and wheels were what the 19th century physics was about. All this aether, something discrete that fills the vacuum, was exactly the trash that Einstein had to throw away, and this non-trivial act was one of the main reasons why Einstein was such a revolutionary. Of course, Einstein could have done it because he was standing on the shoulders of giants, including Hendrik Lorentz.
And then 100 years later someone comes and proposes a new model of aether, a discrete substrate filling the vacuum. Now it should explain gravity instead of electromagnetism. A difference is that the "modern" models, unlike FitzGerald's model, quite obviously do not work and cannot give you the right physics. No 21st century FitzGerald will be able to construct a mechanical model of a spin foam that behaves like general relativity - because it does not behave this way. These models cannot agree with special relativity because of the very same reasons as the 19th century aether. Another difference is that it is not 1860, but 2004. The progress in science was not so terribly non-linear after all - and it is going in some direction. There are just too many people who want to revert science and return us to the trees. In many cases, one can easily decide that certain progress would be "negative".
In physics, we have learned something, and it is impossible to "unlearn" most of these insights. There is a lot of recent insights that will stay with us even if string theory will be proved irrelevant for the experiments. But let's not be too pessimistic. String theory agrees with all the basic (and often also with the non-basic) discoveries and contains all the methods of the previous successful theories - quantum field theory, general relativity, gauge theories, chiral fermions organized into families, Higgs mechanism, confinement, relations between them, Renormalization Group effects, non-perturbative physics, the S-matrix. It's the only known theory different from the old, incomplete framework of quantum field theory that can do everything good that the old theories were able to do as well.
The self-described "competitors" just don't care about the actual physics - I really mean primarily experimental physics. They don't really care whether their theory has something new to say about QCD, general relativity, black holes, particle spectrum, scattering amplitudes - the physical phenomena that really exist. They don't even care whether their theory is consistent with the older insights. They prefer to extend some obsolete and narrow-minded dogmas - such as "the world is discrete" or "the vacuum must be made of something" - dogmas that have really nothing to do with the discoveries physics made in the last 200 years. Dogmas that have been more or less falsified. And that makes a difference.
Some people want physics to become "postmodern" and allow hundreds of different trends that revive various old theories of aether, Lorentz-FitzGerald contractions, hidden variables, and many other wrong things from physics of the past that our heroes had to struggle with for so long before they saw the new light.
I would really prefer if theoretical physics were interrupted completely rather than becoming a "diverse" arena of all these pseudoscientists who are rejecting random principles we learned - as well as the majority of the actual data - and who keep on constructing toy models with very limited ability to agree with anything we actually observe: interrupted physics can continue in the future once people become more reasonable and creative. On the other hand, a return to the proto-science or even pseudo-science would effectively convert the culture of theoretical physicists into the culture of intellectual monkeys once again.
The string theorists know what they're doing and how their theory fits all successful - and experimentally verified - previous insights about Nature; others don't. Our civilization certainly does not have enough resources to pay for all conceivable proto-theories that are comparably attractive as loop quantum gravity - simply because the space of such not-terribly-serious ideas off the track is virtually infinite.
Concerning string theory: don't get me wrong: I am far from being certain that we will have great new successes in the next 2 years, for example. And it's not clear in advance what the LHC will see. I am not even sure whether the number of string theorists is already too high or still too small. But most of my statements are based on a comparison of string theory with the alternatives, and in this respect, my feeling is that there is no rational justification at this point why the alternatives should "grow".
#### snail feedback (43) :
Wow Lubos, you write beautifully and exceptionally clearly when explaining the physics! The first 18 or so paragraphs are right on the mark.
It's when you switch to your "sinners in the hands of an angry God" theologian mode that you lose me. It seems pretty reasonable to me to apply the crackpot label to those who disbelieve theories that have been verified in many experiments (like Darwin's natural selection, Einstein's relativity, and quantum mechanics). When you start applying that label to anyone who has a different approach than yours to unsolved physics problems, that's theology and not physics. The fact that you often resort to violent metaphors (at least I hope they are metaphors) when discussing rival ideas - the phrase "drown in their own blood" sticks in my mind - seems incompatible with the kind of objectivity science has always required.
You say: So I don't really understand what is it exactly that many people feel so uneasy about and why.I hear from a few undergraduates at a top physics school that they have decided against string theory (or physics altogether) because it doesn't look like anything important seems likely to be discovered anytime soon. The total intellectual effort (in man years) that has been invested in string theory to date is probably greater than had been invested in all of theoretical physics before 1930. No definitive predictions that look testable in the near future are known. No string theory model is known that captures all the known features of the standard model. I am just an ignorant outsider, but it looks to me like another string theory revolution is needed.
Cheers
I very much enjoyed the beggining of your post. You have a coherent, rational defense of string theory. This is when you're at your best.
Then you revert once again to calling people stupid. I think this is when you're at your worst.
Here's a question: Do you really think the loop quantum gravity people are stupid? Do you really think, for example, that Lee Smolin is an idiot? Why is there so much rancor in theoretical physics? We have the best jobs in the world! We get to sit around and think about things! We even get paid for it.
Why couldn't you, for example, sit down with Lee for a few beers. You could tell him why you don't like Loop gravity, and he could tell you why he does. Probably in the course of conversation you'd learn a thing or two, and so would he. You might also make another friend.
The point is, our field should be one of an open exchange of ideas, not useless name calling. Perhaps I am just a grad student who is yet to be disillusioned...
I am not a string theory skeptic, but this is ridicolous.
First of all, QCD did make several predictions. The quark model started being taken really seriously after the discovery of the Omega (spin 3/2 sss state), and QCD itself was believed after the discovery of the J/psi, predicted by QCD as an explanation for the absence of FCNCs.
The connection of QCD with experiment is an extremely active field. It is hampered by the fact that QCD is very difficoult, but progress is being made both on the theoretical, phenomenological and experimental front. The theory does not just explain known hadrons, but is now giving us tools we can use to experimentally model "unusual" states of matter (color superconductivity, quark-gluon plasma, etc.)
Nothing comparable exists in string theory. Not even the equivalent of the quark model (a way to "classify" existing low-energy physics). It might in the future, but not yet.
So being skeptical of string theory is not "crackpotism", it's a legitimate minority opinion.
I think it is not concievable for some people to encompass the whole story into a solution and framework, that would be acceptable position to begin from?
As a commoner, this was most troubling, to see vast branchs of explorations, with no consistent framework to begin from(what is the geometry and topological considerations that arises)? Tearing versus discrete?
So I understand now, that the ideas of emergent properties , not only from people like laughlin, but from where string theorists would derive the "principals" that brings this cohesiveness together, was very important. I am still learning.
Cosmology is asking the same question of string theory, and without this dimensional view, there is no way to map a beginning as far as I can tell(particle mapping of collsions))? But I am still very ignorant in these matters and hope to help identify the beginnings of this emergent property in what test runs are made by Nima and others in mapping theoretcial positions of experimentation coming on line :)
For the critical person who talks about the quark models. Interesting feedback, except that its main message is wrong as you will see if you read this whole answer!
What I would agree with is that the counterparts of these discoveries (like "sss") from QCD in string theory have not been seen yet. But it's not true that string theory does not have such things. It has a lot of them, although we don't even know for sure at which scale they will appear. No doubt, they will only appear at a higher scale.
It's just a matter of fact that you need a higher scale. By definition. The low-energy physics has been understood, and new physics only occurs at higher energies. Every theory that is meant to attack similar questions as string theory will have to face the same "complication". It's just impossible to use this as a criticism against string theory. You can use it as a complaint against the very idea that theoretical physics should continue.
"The connection of QCD with experiments is an extremely active field." Well, i think it is not a too interesting field, and I don't believe that something really impressive is gonna be found here. But it's also true that "The connection of string theory with experiments is an extremely active field," and in the latter case I think it is much more interesting.
BUT NOW THE BOMBSHELL. ;-)
Concerning J/psi, I am happy that you wrote it because it shows how clearly wrong the critics are once they're forced to go to technicalities. The J/psi and the absence of FCNCs was not predicted by QCD but by the electroweak theory, years before QCD! Just to make it clear: J/psi was the first particle that contained the c-quark. The only reason why the c-quark has to exist is that the s-quark must have a partner in the doublet of the SU(2) symmetry of the WEAK interactions, and the electroweak theory does not work well without the c-quark! The existence of the c-quark was realized by the GIM mechanism in the electroweak theory, years before QCD was found, and QCD does not care a single bit whether there are u,d,s quarks or four quarks because it is isospin blind!
The example you mention is actually another excellent manifestation of the fact that the similar predictions came from the electroweak theory, and almost never from QCD.
I hope that it invalidates your posting sufficiently clearly.
For those readers who don't understand why David et al. were irritated by the second half of the article:
I reflected the feedback and tried to soften the second part of the article significantly. Enough so that they should be happy now, although obviously ANY ambitious work in progress will always be a slightly controversial topic.
For QCD, there are phenomena observed, for which it appears QCD contains an adequate explanation - even if we cannot compute these to great precision.
I see the situation as analogous to fluid dynamics - the basic phenomena in the laboratory, and the underlying laws are known, and increasing precision of computation is where the game is.
Unfortunately, string theory is nothing like that. String theory does predict a variety of phenomena. But the phenomena predicted by string theory within the experimental regime that we have access to, are not necessary phenomena of string theory; if these phenomena do not show up, it does not invalidate string theory. And we have no experimental phenomena for which string theory is a quantitative explanation (qualitative, yes, and numerological, yes) (I don't consider three coupling constants running into one value to be an experimental phenomenon as of yet, because it is based on extrapolation over a huge scale of energies). So, string theory is not in the situation of QCD.
-Arun
You're not right when you say "string theory is nothing like that", Arun. It's just a misunderstanding of some basic points of the theories and their goals.
Both QCD and string theory are nice structures that however require some input to make full real predictions. In QCD we need various continuous parameters - quark masses etc. In string theory, we need to know the discrete choice "which vacuum do we live in". Maybe we won't need it at the end and there will be a unique prediction for the vacuum selection, but we simply need the discrete piece of information today.
In both cases, there exist predictions that are independent of this input.
You're also very wrong if you think that there is any difference between QCD and string theory regarding the possibility that "the phenomena may be explainable by other theories". You can explain the phenomena of the strong interactions by a convoluted theory with fundamental hadron fields, and their interactions, as long as you don't care that this theory will break down at high energies, and infinitely many irrelevant terms will be undetermined. At high energies, you will patch it with a different description that fits the Bjorken scaling, and you may be satisfied.
The same thing holds for string theory. It is an elegant structure that unifies many different low-energy fields into the rubric of possible modes of a more fundamental object. Nevertheless if we are comparing it with the real experiments, we always prefer to use the language of low-energy effective actions - simply because we know that string theory reduces to them, much like QCD reduces to baryons and mesons at low energies. The low energy actions themselves can almost always "mimick" the stringy physics, but this physics will simply look unnatural in this language.
If you think that there is some serious qualitative difference between these theories in high energy physics, be sure that you are misunderstanding something absolutely elementary about the meaning of string theory.
I have not been following QCD for many years, so this might be a naive question: Do you know if the quark potential can be derived from the theory, or if they still stick with the Cornell potential for Charmonium or any other Ansatz?
regards
Mike Ros
Lubos,
In a hypothetical future scenario where string theory research falls of out favor, what concepts from string theory do you think will survive afterwards?
In a hypothetical "year 2100" scenario where hardly anything from 20th century physics survives intact as it's known today, the few things I can see surviving intact would perhaps be the path integral formalism and the notion of anomaly cancellations. With respect to string related concepts, perhaps holography could survive intact in a hypothetical "year 2100". The Beckenstein-Hawking entropy result appears to be a very deep result.
Most of the important things will survive, even if string theory falls out of favor.
Just like Newton's laws and Maxwell's theory survived as limiting descriptions even in the 20th century, the Standard Model and General Relativity are guaranteed to survive as the low-energy descriptions even in 2100. I have no idea why you think that the anomaly cancellation and the path integral are the only concepts that will survive.
The whole mathematical portion of string theory, including the detailed properties of the Calabi-Yau manifolds and string physics on them, will always survive at least as very important part of mathematics, and these things will always be studied as mathematical or theoretical physics simply because they are.
Holography will survive, too. Gauge theories will always be important for our description of reality, they will never go away either, and it will also be important to know how they behave in different limits, for example for a large number of colors. In this limit the AdS/CFT correspondence holds, and it describes physics of the gauge theory including all details as a gravitational theory with all the string phenomena that string theory predicted independently.
There is just no way how this can go away, except for the possibility that the people will lose their brain and ability to understand mathematical facts.
You know, just the very fact of the importance of gauge theories more or less implies that all concepts of string theory - excited strings, D-branes, NS5-branes, bubbling topology, quantum mechanics of black holes, black hole thermodynamics, critical transitions - all these things are guaranteed to stay with us in physics.
Of course, stringy phenomenology is a completely different question. Once we have some data from higher energies, at least 99% of the particular models will be understood as wrong and irrelevant. But this is true for all of phenomenology beyond the Standard Model, not just for stringy phenomenology!
To summarize: all important mathematical features of string theory are guaranteed to survive as a part of physics even if string theory falls out of favor. If you only quote the Bekenstein-Hawking entropy, it just means that you misunderstand everything in string theory. In string theory, one can reproduce the entropy formulae from totally different, dual starting points. They're, more or less by definition, equally fundamental as the simple "area" approach to the entropy. It can't be otherwise.
What I wanted to convey by this text is that some people are just overly self-confident about their ability to judge the theories they don't understand. If someone has a physics PhD, it does not mean that his comments about string theory will be valuable. There are many people who understand Newton's laws, less people who understand the Hawking-Bekenstein formula, and even less people who follow string theory. But this certainly does not mean that these insights are decrasingly deep! It just means that they're increasingly difficult.
Hi Mike Ros,
it's not my field, but see some recent papers about the potential quark models and their relation to QCD:
http://arxiv.org/abs/hep-ph/0409112
http://arxiv.org/abs/hep-lat/0312031
http://arxiv.org/abs/hep-ph/0310251
I don't know what's the right short summary.
All the best
Lubos
Neils Bohr once said (to other theoretical physicists)that as physicists they had a great advantage over philosophers, in that they had all published something that was subsequently shown to be wrong! I'm guessing that he had in mind the humility this engendered.
Maybe that accounts for the fact that he and Einstein were able to conduct their long argument over quantum mechanics with the utmost civility and good humor. Of course it might have helped that tenure was not at stake for either.
It's been observed that academic debates tend to be most bitter where facts are least in supply. Thus philosophers and literary critics debate ferociously, and theologians, including the recent Stalinist-Leninist variety, are happy to slaughter millions over slight differences in interpretation.
I hope physics isn't coming to that, but we are suffering from a dearth of new data.
I do think that cooling your jets would make you a lot more persuasive, Lubos. We all learned debate by insult in primary school, but most of us find it less attractive as we get older.
Lumo saith: If someone has a physics PhD, it does not mean that his comments about string theory will be valuable.In this respect string theory is very different from climate science, where all the good comments come from MD's, history PhD's and string theorists;-)
Dear imperialist pig (this is not an insult, it is your name) ;-),
you may think that you are joking :-), but actually what you say is absolutely true and rather important. Climate science is really very different from string theory. The best climate science is done by political scientists, economists, and assorted physicists, while one must really study some background for years to get into string theory.
All the best
Lubos
Lubos,
as others have pointed out already you make many good points
and in general you are a smart advocate of superstring theory
at the same time keeping its critics honest.
However, I think you are too negative on QCD. As far as I
understand hadron spectroscopy is how theory (lattice QCD
and other calculations) and experiment are compared.
Recently a lot of progress has been made and these are
difficult (grand challenge) but straight-forward projects.
As you have pointed out these projects are not even too
interesting, simply because QCD spectra and experiments match within the error bars (otherwise this are would all of a sudden be very hot!). It is not about one particle (you mentioned J/psi) but the whole spectrum.
Obviously there is no such thing for superstrings and even
worse (in my opinion) there is no experimental evidence yet
for the main ingredient: super-symmetry.
And this is another difference: A lot was know about the
underlying symmetries before the standard model was put together. In the case of supersymmetry the symmetry was
conjectured first and now we are waiting for some evidence.
By the way, I always assumed that "discrete models" of
quantum gravity were supposed to be calculation tools,
what lattice QCD is to QCD.
I do not think that many people would take "discrete models"
to be a true image of reality ...
Best regards,
Wolfgang Beirl
lumo said: The best climate science is done by political scientists, economists...That statement is absurd for the same reasons as claiming that string theorists are too brainwashed to critically examine their own theories. You can't do any kind of science without understanding the details, as Feynman liked to point out. Your friend Lomborg goes wrong repeatedly for just that failure. True many physicists have contributed to climate studies, (meteorology and oceanography are branches of physics), but only those who have gone to the trouble of mastering the details.
You don't need to know algebraic topology or differential geometry (or even QFT or GR)to understand the physics of the climate system but you do need to understand fluid dynamics, thermodynamics, and radiative transfer as well as a lot of specific knowledge and understanding of the measurements involved and how climate models work.
Of course anybody who knows a little intuitive psychology can figure out how to tell you what you want to hear. So hey, don't listen to me. I sure Rush Limbaugh can teach you all the climate science you want to know.
Dear capitalist p.i.g.,
we differ because I prefer the results, not vague prejudices. If you look at the list of the 25 most influential scientists (TIME), you will find Witten for string theory, indicating that it is useful to be mathematically experienced, educated, and super-smart, but for the future planning of the planet & predictions of the future impacts of the climate, you will find a political scientist by profession, Bjorn Limborg.
Some people may study and be brainwashed by other alarmists, but these people are simply not so scientifically productive.
I certainly don't believe that the average alarmists understand thermodynamics, radiative transfer, and fluid dynamics well, and even if some of them did, it is not enough to predict the climate variations.
Yes, I am not dreaming about hearing once again all the alarmist teachings that I've heard about 1000 times already. And yes, I also think that Rush Limbaugh has probably more reasonable opinions about the climate than the people who play with their computer games that they call "models".
Best
Lubos
Dear Wolfgang,
thanks for your comments. It's a bit incomprehensible to me how can you create a calculational technique for a theory that does not exist. Lattice QCD only works because it is a discrete version of QCD, a quantum theory of exists.
If you make lattice general relativity, it will not work because "quantum general relativity" does not exist as a theory unless you add all the necessary new physics at the Planck scale.
We don't have an experimental confirmation of SUSY and other things predicted by string theory, but we also don't have any experimental indications that string theory contradicts something.
Happy Weinachten,
Lubos
Lubos,
I just do not see how you can "add all the necessary
new physics" without experimental evidence and hints
what the new physics actually is.
Are you saying that you can proof that superstring
theory is the only consistent theory at high energies ?
No physicist in the 18th or even 19th century was able
to "guess" that electrons, photons etc. are "necessary"
or even that relativity was "necessary" based on their
knowledge of the "low-energy limit" (falling apples etc. 8-)
As I wrote already, I wish you good luck (and I really mean
it) with your project, but I believe supersymmetry only when
I see it. You have indicated that the LHC should do the
trick ...
Merry Christmas und eine Froehliche Weihnacht,
Wolfgang Beirl
Lubos,
I can see you won't be persuaded by me.
Merry Christmas or whatever you celebrate.
From Da Pig
Lubos,
What is the experimentally accessible phenomena which requires string theory?
What was the experimentally accessible phenomena which required a theory of strong interactions?
One doesn't have to know any string theory or QCD to know that the experimental situation available at the time of development of the two theories is very different. The particle data book was filled with stuff begging for an explanation.
What is the most striking prediction of string theory in the experimentally accessible regime? What were the most striking predictions of QCD? Some knowledge is needed here, but the situation is clear enough.
Regarding QCD requiring external input such as quark masses - QCD was not meant to be a theory of everything. A Theory of Everything is on shaky grounds when it cannot provide a principle to decide between vacua.
----
I see one of two possible answers to the above :
a. something concrete, or
b. "the above shows ignorance of string theory".
----
IMO, General Relativity is more akin to string theory than QCD, in terms of its development. There was no experimental results pointing to anything wrong with Newtonian gravity; the real motivation for seeking GR was that Newtonian gravity is incompatible with Special Relativity. With regard to GR, we were fortunate in that a few observations were immediately within reach.
---
Anyway, perhaps we should declare a moratorium on arguments on the validity of string theory until we see what the LHC shows.
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You are only partially right about J/psi being an electroweak, rather than a QCD, discovery. It is true that the calculation was electroweak. However, it's effect was to convince the particle physics community that quarks were not simply a classification scheme but actually real particles. Heavy quark spectroscopy was the cherry on the icing, since the fact that running coupling implied energy levels of the predicted heavy quark states were perturbative was predicted before the J/psi discovery.
The fact that SU(2) is "simpler" than SU(3) is due to symmetry breaking. Otherwise, it would also be asymptotically free, non-pertrurbative and probably confining as well.
Is there "anything similar" in string theory? Other than the observation of KK states, I don't see any, since other "string theory" results (extra dimensions, SUSY, SUGRA) predate string theory and are not necessarily associated with it.
Can this failure of string theory be excused by the necessity of a higher energy scale? Actually, not really. The cosmological constant is a big problem because the energy scale argument does not hold. Even if at the string scale the cosmological constant is zero, the EFFECTIVE LOW ENERGY VACUUM should have a QFT-calculable cosmological constant, which as far as we know is WAY bigger than ANYTHING observed. String theory has, as yet, NO answers to this, other than the phenomenologically useless anthropic argument and proposals (Dvali-Gabadadze-Porrati) "inspired" by string theory but not really part of it.
As far as a TOE goes, that's a pretty damn big failure.
Quarks/QCD, as you correctly say, was in contrast able
to describe all of the existing physics.
I am amused by your contention that string phenomenology, with no hint of an experimental connection as yet, is "more interesting" than QCD research. At the moment, there is an invasion of string theory types into QCD, since trying to connect to QCD via the ADS/CFT correspondence (A LOOONG shot, through I'd be very happy if it succeeded) is the only hope they have to connect the theory to the real world.
Dear Wolfgang,
yes, I am saying that we know that physics of string/M-theory is the only way how to tame general relativity in four (or more) dimensions in the quantum regime. We don't have a rigorous proof, but we kind of know it.
More importantly, even if you thought that you see "something" else in the experiment, it will never allow you to make anything meaningful out of an *inconsistent* theory of "something" - like a quantum theory of gravity that contains nothing stringy.
Yes, I agree that no one in the 18th century was able to predict the existence of electrons etc. And I therefore also agree that string theory is exceptionally amazing in this respect.
Arun, also for you. The experiment that makes string theory inevitable is Newton's falling apple (together with the Standard Model), and it is just a matter of mathematical thinking to understand why. Theoretical physicists always needed to think mathematically, but they just need to do it more and more seriously, as the article explains more than clearly, I am sure.
Your wrong conclusions show that you're not thinking about physics and the logical connections about its concepts seriously enough.
String theory is not primarily a theory of the experimentally accessible regime even though we may see one of the major scenarios at the LHC: string theory is the only candidate for a theory of everything and a theory of quantum gravity which is not directly experimentally accessible. Its new phenomena simply operate at a higher scale, and they have higher requirement for the experiment.
QED had low requirements for the experimentalists because QED is only an approximate theory of the "conventional" phenomena that are essential for electromagnetism, chemistry, and life. As the scale of the theories grows, the requirements grow as well. But this is not a problem of the theories: it is an inherent property of the questions themselves.
You ask "What were the striking predictions of QCD?" I am not sure whether you read the article, or whether you just repeat the sillyness about "unprecedented disconnectedness of string theory from physics" without reading anything new. The article was explaining that there were no "striking" predictions of QCD, and all candidates what they were supposed to be, listed below the article, were actually predictions of the electroweak theory.
The situation of QCD was qualitatively analogous to string theory in the sense that QCD is the only working quantum field theory that could agree with the phenomena that were known before, much like string theory is the only theory that can work with all of them including quantum gravity. But the new basic objects phenomena predicted by QCD can never be seen in isolation - the gluons, the quarks, their colors. QCD implies that they cannot be seen.
If you were using the same naive thinking that you use against string theory, but against QCD, you would conclude that it is a theory based on objects that were never seen, and its description of the observed objects and phenomena is just qualitative, handwaving, and depends on many assumptions about distributions of quarks on the nucleons and so forth.
You don't realize that because you were probably never thinking about QCD seriously enough. You think that one can just jump directly to string theory and say something meaningful about it. But it's not possible. One must first understand quantum field theory and GR well, and only afterwards she can start to appreciate what string theory does.
The fathers of QCD - and many others - knew that the theory was correct even without the confirmed "striking" predictions. One really had to wait until the 1990s to see some cross sections - irrelevant for many others - to be measured with the 1% accuracy, and this is what forced the critics of QCD to disappear. Sorry, Arun, but the less smart one is, the more striking confirmed predictions one needs to understand that a correct statement is correct.
A good physicist should always realize that he can be being foolish. You seem to be proud about being foolish which is simply a wrong approach to any difficult question.
Happy Christmas (and other holidays for others)
Lubos
I've erased a silly posting by Quantoken that claimed that he had found a serious error in a rather well-known paper about a completely different topic than what is discussed here - but of course he won't tell you what the error is supposed to be. Given the fact that he does not follow mathematics even 3 levels below that paper, I feel that such comments add too much noise to this focused discussion.
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For the QCD person:
I was saying that J/Psi and the GIM mechanism were not based on any argument involving QCD whatsoever and they could not help to prove QCD. What I say is true, and not just "partially" true. One reason is simple: the GIM mechanism was already published in 1970. The GIM mechanism has nothing to do with "colors" of quarks, the strong force between the quarks, or anything like that which we call QCD.
The argument of GIM was an electroweak argument, and it does not really depend on the question whether the quarks are "elementary" or just "thought" constituents, more precisely it does not depend at all on the character of the force that keeps them together. It does not depend on QCD, assuming that we mean the same thing by QCD.
I consider the previous two paragraphs as answering - invalidating - the first part of your posting. Your posting then continues along the usual lines: other features of string theory predate string theory and preposterous Al-Qaeda-like rants about "failures".
First of all, it is always like that in physics that the concepts usually appear before the full theory is seen. Second of all, string theory is, on the contrary, a counterexample in many respects.
The QCD example happens to be discussed above. The concept of quarks appeared years before QCD and Gell-Mann got a Nobel prize for it in 1969. They became just a small part of QCD five years later or so.
The extra dimensions predate string theory, yes - the string theorists are continuing many threads in physics and the Kaluza-Klein thread is one of them. But supersymmetry (in the Western world) was discovered in the context of string theory, in Ramond's homework problem to incorporate fermions into (bosonic) string theory. Most of the fancier details about extra dimensions also appeared in string theory. The fact that one can isolate an idea from string theory to make a simplified presentation for a layman does not mean that the idea is not a discovery of string theory.
I insist that the people who keep on copying the confused statements about the alleged "failure" of string theory from each other don't understand physics well enough to participate in this discussion meaningfully, and I wish them happy holidays DESPITE their ignorance.
I've erased another anonymous off-topic political stupidity about someone not being objective because of links with evil corporations. These blogs should have some kind of artificial intelligence to identify morons and deny them posting. ;-)
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QCD:
Experimentally verified predictions:
Scaling violation in deep inelastic scattering
Corrections to Bjorken sum rule
Correction to Gross-Llewyllen-Smith sum rule
b-b-bar threshold production
Prompt photon production in pp and p-bar collisions
Lattice guage theory calculations of heavy quark spectra
Heavy quarkonium decays
Shape variables characterizing jets at different energies
Total e+-e- annihilation cross-section
Jet production in semi-leptonic and hadronic processes
Energy dependence of photons in Z decay
Consistency with current algebra (effective low energy theory of pions)
etc., etc.
All this comes from a simple theory that can be written down (non-perturbatively) in one line, involves exceedingly beautiful mathematics (gauge theory + Dirac equation). Only free parameters are quark masses. High energy behavior well understood and completely consistent.
String theory:
Experimental predictions:
Not a single one
Theory can't be written down in a single line, because (non-perturbatively), no one knows what it is.
Merry Christmas!
Peter
http://www.math.columbia.edu/~woit/blog
Peter, many of these things are discussed in the article. Some other predictions are real, of course, but they were only confirmed recently, much like string theory's predictions that will be confirmed in the future. Superstring theory is simply a newer theory than QCD, and everything is logically moved to the "future".
Your statements about "simplicity" of QCD vs. string theory only reflect the fact that you don't understand string theory. String theory can often be simpler than QCD, and some things in QCD are harder. Of course, for you who knows nothing about string theory, it's not simple - but this observation has no scientific consequences.
There are many people who hate relativity or quantum mechanics because it is not simple enough for them - for these simpletons. I called them crackpots, and I also explained why the case of string theory is analogous, just on a higher level. You're a crackpot with respect to the last 20 years of physics, Peter.
Try to read Quantoken's postings on your blog carefully - and you will see how qualitatively similar to this crackpot you actually are! It's just a slightly different level of crackpotness.
Happy Christmas anyway,
Lubos
Incidentally, the exact, non-perturbative definition of M-theory can also be written on one line, see e.g. http://arxiv.org/abs/hep-th/0101126
Such amazing discoveries would have never been made if the people responsible for organizing physics were listening to crackpots like you.
Lubos,
I'll reiterate my previous sentiments. Using "crackpot" to describe somebody generally connotates that not only are they stupid, but they are crazy.
Do you really think it is crazy to have objections to string theory?
Do you really think it elevates the intellectual debate to call other, clearly intelligent people, crackpots?
You do a very good job of defending string theory when you are not name calling. I think we would all prefer if you stuck to that.
Dear David Guarrera,
thanks for your feedback. Concerning craziness, it depends how you define "crazy". :-) I am using the word "crackpot" in a rather standard fashion, see for example
http://en.wikipedia.org/wiki/Crackpot
to check that my usage of the word does not differ from the usual definition in a significant way - perhaps not at all. And you know I've been trying to be careful to reduce the usage of the word for those whose critical barrier in physics, which is very hard to overcome, is around 1975 ;-). OK, I will try to be even more friendly to them!
Happy Christmas,
Lubos
Here's a crackpot, Lubos:
"The Einstein's theory , in fact ,regards matter as an event
which include time effect and space effect , the effect is one
which people reaserch most in all kinds of effects of matter .
Besides people reaserch the relative effect with time-space concept
, they are heat effect , smell effect , sence oof taste effect
, colour effect , vanish annnd production of matter effect .but
these effects ,in essence ,connect ,such as ,when photon produces
the time-space effect ,it also has heat effect..."
cut and pasted from an email that was appearently just sent to a whole bunch of physics MIT people. My first crackpot email, how exciting!
Dear David,
I am so jealous about your romantic feelings ;-) of the first crackpot e-mail - the nice belief that there may be something deep in it and that you will gain a new perspective how to look on the world!
And I am sorry in advance for your change of the opinion about these e-mails once you get 2004 of them like me. ;-)
All the best
Lubos
I don't agree that physics is a progression from theories which are easy to compute and give accurate predictions to theories which are hard to compute and give less accurate predictions. You give the sequence Newtonian mechanics, relativity, quantum mechanics, quantum field theory, QED, electroweak theory, QCD, string theory, but you left out other subfields. Turbulence is still very messy, even though the Navier-Stokes equation was discovered during the 19th century. Computing the spectrum of multielectron atoms in atomic physics isn't easy, much less predicting chemistry from first principles. We just happen to be lucky we can predict the results of QED to such accuracy.
I think that your example provides very good support for my thesis, too. The Navier-Stokes equations are, in some sense, very analogous to QCD. They are not *just* equations to describe turbulence. They describe fluid dynamics, including the simple, slightly perturbed linear phenomena. In this regime of small "Reynolds number", so to say, they are much more simple and "perturbative" than even high-energy QCD, and therefore there could be found in the 19th century by analyses of nearly frictionless liquids.
Their application to the highly turbulent regime is a strongly coupled problem analogous to strongly coupled QCD, and of course it takes much longer to calculate this stuff.
The accuracy success of QED is not just "luck". It has a rational explanation. QED is very close to fundamental physics and so its processes are "clean" and inherently accurate (unlike processes with some dirty composite matter); on the other hand, the coupling of QCD is very small which makes perturbation theory excellent. If the coupling is more like alpha=1/10, then one cannot really neglect the possible Landau poles etc. and one cannot get as exact results as from QED.
I wanted to say "coupling of QED is small", of course. ;-) The third necessary feature that makes tests of QED so accurate is that the QED phenomena are easy to generate - the whole life and technology is based on them. What I want to say is that once one knows theories AB,CD,EF, how they work theoretically, he can also predict which of them will be accurately tested (knowing some basics of available technology, which, in some sense, is also included in the equations).
Why we're lucky QED can be computed to such high accuracy
1. The coupling constant e is small, about .1
2. The nature of QED Feynman diagrams is such that internal vertices come in pairs and so, the perturbation series is in powers of e squared.
3. The mass of the next lightest charged particle ("bare" quarks are confined), the muon is hundreds of times the mass of the electron and there are only a small number of charged light pions. The other charged particles have masses thousands of times that of the electron.
4. For the neutral pion, the photon self-energy contribution from the diagram where a photon splits into a quark-antiquark pair which then annihilates to give back a photon has to be added similar diagrams where an arbitrary number of gluons are interchanged because QCD is strong. Nonperturbatively (with respect to the QCD coupling only!), this means the contribution from neutral pions is small.
5. The weak interaction is very weak at the scale at which QED experiments are being performed, due to the decoupling of the W and Z bosons.
6. Electrons aren't "colored" (carry a chromodynamic charge)
7. Gravity is completely negligible.
8. QED is renormalizable
We would have to consider ourselves very lucky if there is another theory with this much "luck".
For the contributor with the numbered list: the list is a kind of astrology. Let me try to explain you these "observations" of yours.
1. I've mentioned the small coupling constant in the article
2. It's not just QED where you get an expansion in powers of e^2 which is proportional to alpha. In *any* gauge theory, the diagrams "conspire" in such a way that the real physical observables are always expansions in terms of g^2. It's because you can write the Lagrangian in a way that only depends on g^2, as 1/g^2 Tr (Fmn.Fmn)...
3. Muons are 206.8 times heavier than the electron. If there were several light charged leptons with masses comparable to the electron, be sure that it would not destroy the accuracy of QED calculations. The existence of light pions comparable to the electron would make the calculations tougher indeed, but the reason is not in QED itself: the reason is that you would have to include QCD to your QED calculations.
4. Contributions from intermediate pions is small because they are approximate Goldstone bosons, but it has nothing to do with the overall simplicity of QED and hardness of QCD calculations.
5. This point only says that QED is a good effective theory, and separated from the weak interactions. Of course if it were not a good effective theory, we would have to find another one. But be sure that today, even if the W and Z bosons were much much lighter, we would be able to make the same exact calculations of electrons' properties simply because we DO understand the weak interactions, too.
6. The sentence "electrons are not colored" just means that "QCD does not operate at the electron scale" - it's a part of the definition of QED and QCD. Once again, if QCD electrically charged objects were as light as the electron, one would have to consider QCD and QED simultaneously, but then you could not say that "QED" calculations are difficult simply because the right calculations would NOT be just QED, but mostly QCD. It would still be QCD that is difficult.
7. Gravity is negligible even in QCD, but this is not enough to make the calculations easy.
8. QED, as well as the rest of the Standard Model, is renormalizable. QED is however perturbatively inconsistent unlike QCD. QCD is *more* consistent than QED.
Your last "luck" comment is also confused. Of course that only the theory at very low energies - comparable to the lightest particle charged under something - is as simple as QED, and there can only be roughly one simple theory like that. But it does not mean that we can't find other theories. Well, we know that we have other theories, too.
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https://quant.stackexchange.com/questions/50842/risk-neutral-price-of-h-ex-t1x-t3
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# Risk-neutral price of $H=e^{X_T^1+X_T^3}$
Let $$B=(B_t^1,B_t^2,B_t^3)$$ a $$\mathbb R^3$$-valued Brownian motion. Let $$r_t$$ (risk free rate) be bounded and deterministic. Let consider the DISCOUNTED market $$d\overline X_t^1=\frac52dt+2dB_t^1-dB_t^2-dB_t^3$$ $$d\overline X_t^2=7dt+2dB_t^1+2dB_t^2-10dB_t^3$$ $$d\overline X_t^3=\frac72dt+4dB_t^1-3dB_t^2+dB_t^3$$ I have already found that the market is arbitrage free.
I would like to find the risk-neutral price of the following claim:$$H=e^{X_T^1+ X_T^3}$$ (note: here the $$X_T^1,X_T^3$$ are not discounted) but i'm stack. Any help please?
• Are there 3 different $X_t$ processes? In your notation it seems the same process. – Daneel Olivaw Jan 26 at 0:30
• Also what are the $B$s at the end of each equation? – Daneel Olivaw Jan 26 at 0:32
• @DaneelOlivaw yes sorry, now I edit it – Buddy_ Jan 26 at 8:02
• @DaneelOlivaw don't you have any suggestion? – Buddy_ Jan 26 at 15:57
• why not to use montecarlo to compute the price?? – Valometrics.com Jan 26 at 20:43
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http://www.advanceduninstaller.com/SUPERAntiSpyware-99ac22fca78245a6081e75db0ed7fbbb-application.htm
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# SUPERAntiSpyware
## A way to uninstall SUPERAntiSpyware from your system
This web page is about SUPERAntiSpyware for Windows. Here you can find details on how to uninstall it from your PC. It is made by SUPERAntiSpyware.com. Further information on SUPERAntiSpyware.com can be seen here. You can read more about on SUPERAntiSpyware at . Usually the SUPERAntiSpyware application is installed in the C:\Program Files\SUPERAntiSpyware folder, depending on the user's option during setup. You can remove SUPERAntiSpyware by clicking on the Start menu of Windows and pasting the command line C:\Program Files\SUPERAntiSpyware\Uninstall.exe. Keep in mind that you might receive a notification for admin rights. SUPERANTISPYWARE.EXE is the SUPERAntiSpyware's primary executable file and it occupies approximately 7.58 MB (7943072 bytes) on disk.
SUPERAntiSpyware installs the following the executables on your PC, occupying about 9.17 MB (9619336 bytes) on disk.
• RUNSAS.EXE (308.77 KB)
• SASCore64.exe (168.30 KB)
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• HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall\{CDDCBBF1-2703-46BC-938B-BCC81A1EEAAA}
• HKEY_LOCAL_MACHINE\Software\SUPERAntiSpyware.com
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• HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\!SASCORE\Description
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• HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SASDIFSV\ImagePath
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SUPERAntiSpyware is a program released by the software company SUPERAntiSpyware.com. Frequently, computer users decide to erase it. Sometimes this can be efortful because removing this by hand requires some experience regarding removing Windows programs manually. One of the best EASY practice to erase SUPERAntiSpyware is to use Advanced Uninstaller PRO. Here is how to do this:
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http://cms.math.ca/cjm/kw/polynomial%20return%20times
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location: Publications → journals
Search results
Search: All articles in the CJM digital archive with keyword polynomial return times
Expand all Collapse all Results 1 - 1 of 1
1. CJM 2012 (vol 65 pp. 171)
Lyall, Neil; Magyar, Ákos
Optimal Polynomial Recurrence Let $P\in\mathbb Z[n]$ with $P(0)=0$ and $\varepsilon\gt 0$. We show, using Fourier analytic techniques, that if $N\geq \exp\exp(C\varepsilon^{-1}\log\varepsilon^{-1})$ and $A\subseteq\{1,\dots,N\}$, then there must exist $n\in\mathbb N$ such that $\frac{|A\cap (A+P(n))|}{N}\gt \left(\frac{|A|}{N}\right)^2-\varepsilon.$ In addition to this we also show, using the same Fourier analytic methods, that if $A\subseteq\mathbb N$, then the set of $\varepsilon$-optimal return times $R(A,P,\varepsilon)=\left\{n\in \mathbb N \,:\,\delta(A\cap(A+P(n)))\gt \delta(A)^2-\varepsilon\right\}$ is syndetic for every $\varepsilon\gt 0$. Moreover, we show that $R(A,P,\varepsilon)$ is dense in every sufficiently long interval, in particular we show that there exists an $L=L(\varepsilon,P,A)$ such that $\left|R(A,P,\varepsilon)\cap I\right| \geq c(\varepsilon,P)|I|$ for all intervals $I$ of natural numbers with $|I|\geq L$ and $c(\varepsilon,P)=\exp\exp(-C\,\varepsilon^{-1}\log\varepsilon^{-1})$. Keywords:Sarkozy, syndetic, polynomial return timesCategory:11B30
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https://www.nature.com/articles/s41612-018-0041-9?error=cookies_not_supported&code=d7f13b62-9bfd-477d-9547-00bddafb8b90
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Article | Open | Published:
# Tropospheric OH and stratospheric OH and Cl concentrations determined from CH4, CH3Cl, and SF6 measurements
npj Climate and Atmospheric Sciencevolume 1, Article number: 29 (2018) | Download Citation
## Abstract
The hydroxyl (OH) radical is the key oxidant in the global atmosphere as it controls the concentrations of toxic gases like carbon monoxide and climate relevant gases like methane. In some regions, oxidation by chlorine (Cl) radical is also important, and in the stratosphere both OH and Cl radicals impact ozone. An empirical method is presented to determine effective OH concentrations in the troposphere and lower stratosphere, based on CH4, CH3Cl, and SF6 data from aircraft measurements (IAGOS-CARIBIC) and a ground-based station (NOAA). Tropospheric OH average values of 10.9 × 105 (σ = 9.6 × 105) molecules cm−3 and stratospheric OH average values of 1.1 × 105 (σ = 0.8 × 105) molecules cm−3 were derived over mean ages derived from SF6. Using CH4 led to higher OH estimates due to the temperature dependence of the CH4 + OH reaction in the troposphere and due to the presence of Cl in the stratosphere. Exploiting the difference in effective OH calculated from CH3Cl and CH4 we determine the main altitude for tropospheric CH4 oxidation to be 4.5 ~ 10.5 km and the average Cl radical concentration in the lower stratosphere to be 1.1 × 104 (σ = 0.6 × 104) molecules cm−3 (with a 35% measurement uncertainty). Furthermore, the data are used to examine the temporal trend in annual average stratospheric OH and Cl radical concentrations between 2010 and 2015. The year 2013 showed highest stratospheric OH and lowest Cl but no clear temporal trend was observed in the data in this period. These data serve as a baseline for future studies of stratospheric circulation changes.
## Introduction
The hydroxyl radical (OH) is the most important oxidant in the troposphere and lower stratosphere. It initiates removal from the atmosphere of toxic gases such as carbon monoxide (CO), radiatively active gases such as methane (CH4), tropospheric ozone precursors such as volatile organic compounds (VOCs), and NOx (NO + NO2), and stratospheric ozone-depleting compounds such as hydrochlorofluorocarbons (HCFCs).1,2 Therefore, it plays a key role in the atmospheric oxidation capacity, air quality, and climate.3
One source of atmospheric OH is the reaction of O1D, a minor product in the photolysis of ozone, with H2O.4,5 An even larger source in terms of gross OH formation is recycling from its reaction products, which maintains the atmospheric oxidation efficiency.6 Despite its low ambient concentration (<1 pptv), and its short atmospheric lifetime (<1 s), the first valid OH measurements (by fluorescence assay with gas expansion, FAGE) were reported as early as the mid-1980s at ground level.7 Measurements were later extended to the upper troposphere and lower stratosphere with balloons8 and the high-altitude ER2 research aircraft,9 in parallel with alternative measurement methods such as differential optical absorption spectroscopy DOAS,10 mass spectrometry via H234SO4 (ref. 11), and 14CO radioactive counting techniques.12 These in-situ measurements are broadly consistent with regional scale indirect OH determinations using the depletion of hydrocarbons over multi-hour timescales13,14, and with empirical assessments based on the variability-lifetime relationship.15,16
Although OH concentrations at a given point in space and time can now be measured reliably at high frequency to examine local photochemistry, it is difficult to relate such OH concentrations that vary strongly with actinic flux and H2O, to longer lived species transported zonally in the troposphere and eventually into the stratosphere. To address this, advanced models have been applied to make indirect estimates of the global OH concentration based on methyl chloroform (CH3CCl3) and 14CO data.2,3,6,17,18,19 However, such models inevitably contain in-built assumptions, including uncertain emissions inventories as well as transport and deposition parameterizations that may differ from real world conditions.
In this study, we have developed and applied an empirical data-based method to estimate the “effective OH concentration” that has acted in the troposphere and lower stratosphere over longer (yearly) timescales between 2008–2015. Our approach uses long-term measurements of three species (SF6, CH3Cl, and CH4) made at the ground and monthly at 10–12 km altitude during long distance commercial aircraft flights. SF6 measurements are used to derive the mean air age of the airborne samples, i.e., of the trace compounds contained therein, so that the initial surface mixing ratios of CH3Cl and CH4, upon emission, can be determined from the surface network and compared with the OH affected samples taken at altitude. Knowing the age of the sampled air, the net change in concentration and the reaction rate coefficient allows an “effective OH” concentration to be calculated assuming OH is the only sink. Both CH3Cl and CH4 are predominately removed from the atmosphere by OH although reaction rates are relatively slow (atmospheric lifetimes are about 1 year20 and 8–10 years18, respectively). CH3Cl is mostly emitted from tropical vegetation21 and is the most abundant natural source of stratospheric chlorine.22,23 The greenhouse gas CH4 is emitted from wetlands, ruminants, rice fields, landfills and fossil fuel use, and atmospheric concentrations have increased strongly over the past 200 years.24,25 In the context of this study an important difference between CH3Cl and CH4 is that the rates of reaction with OH and Cl are much more dependent on temperature in the case of CH4. Using this data-based approach we may empirically determine a representative annual “effective OH concentration” for the troposphere and the lower stratosphere. Furthermore, we may look for indications of temporal trends in OH and hence changes in global oxidation capacity. Finally, by exploiting the reaction rate differences between CH3Cl and CH4 we can even attempt to determine the height in the troposphere where CH4 oxidation by OH is largest and estimate Cl radical concentration in the lowermost stratosphere.
## Results
### OH concentration as a function of mean age
The derived “effective OH concentration” experienced by an air parcel will be hereafter shortened to OHeff, and depending on the air age be referred to as tropospheric OHeff (age < 100 days) and stratospheric OHeff (age > 200 days). The rationale is that an air sample collected in the upper troposphere—lower stratosphere (UTLS) region can be regarded as a mixture of two major large-scale airflows.26,27,28 The first is the fast transport of air from the tropical tropopause layer (TTL) to the extra tropics (Fig. 1 blue lines), which normally takes place within 0.3 years (~ 100 days), while the second pathway (Fig. 1, red lines) is the slower downwelling transport from the “overworld” (potential temperature > 380 K) into the lowermost stratosphere, which is associated with the lower branch of the Brewer-Dobson circulation (BDC). Note that the compounds within the lower stratosphere of the northern hemisphere are predominately influenced by the BDC and not the northern mid-latitude emissions (~ 10%).29 In order to simplify interpretation of the results and to apply our analysis to the region of highest airborne data coverage we use only samples collected between 30°–60°N in the UTLS region (Fig. 1, box).
Figure 2 shows the OHeff derived from both CH3Cl (black boxes) and CH4 (red boxes) and OHr (real OH, blue boxes) derived from OHeff and stratospheric Cl (eq. 4, see Methods) as a function of mean air age. The tropospheric (mean age < 100 days) mean OHeff from both species is significantly larger (by a factor of 6 on average) than the lower stratospheric (mean age > 200 days) mean OHeff. Air with a mean age of between 100–200 days appears to be influenced by both troposphere and stratosphere, and accordingly OHeff for both species in this age range lies between the younger (tropospheric) and older (stratospheric) values. Median tropospheric OHeff were 9.93 × 105 and 2.63 × 106 molecules cm−3 for CH3Cl and CH4, respectively, whereas median stratospheric values from 200–1100 days were 1.69 × 105 and 3.35 × 105 molecules cm−3. Tropospheric OHeff values exhibit a much larger variability than stratospheric values, likely due to the strong sources and sinks of both molecules in the tropical troposphere, including weak seasonal variations that impact the term [A]g− [A]C in Eq.1. Stratospheric OHr exhibits smaller variation compared to stratospheric OHeff and is rather constant for samples with mean age between 200 and 700 days with a median value of 1.0 × 105 molecules cm−3, whereas for samples older than 700 days, OHr decreases due to the decrease of ozone, water vapor, and molecule density in the upper stratosphere. Median, average, and standard deviation data are given numerically in Table 1(a).
Interestingly, OHeff calculated using the CH4 data was consistently higher than using CH3Cl data. The tropospheric median OHeff derived from CH3Cl for years 2008–2015 is 9.9 × 105 molecules cm−3, which matches the tropospheric mean OH concentration of 1.1 × 10 6 molecules cm−3 reported from a recent global modeling study.6 However, the median tropospheric OHeff derived from CH4, 2.6 × 106 molecules cm−3, is between two and three times larger. Intuitively this seems unreasonable since both measurements stem from the same air sample and, therefore, must render the same “effective OH concentration” assuming there is no additional reagent inputs. One possible explanation for this apparent discrepancy is that loss processes besides OH remove CH4 from the atmosphere but are then calculated as OH in this approach. For example, the reaction with chlorine radicals (Cl) with CH4 has been shown to be significant in Asian pollution outflow.30 The aforementioned paper reported the presence of radicals in the ratio [Cl]:[OH] of 9 ~ 16 Cl:103 OH, and since the reaction rate of CH4 with Cl is ~ 32 times faster than that with OH (for CH3Cl it is only ten times faster),31 an apparent overestimation of OHeff by about 30–50% can ensue. However, such high Cl radical concentrations have only been seen under very specific conditions (lofted coastal pollution outflow) and so this cannot explain the OHeff difference in the global tropospheric data. An alternative explanation for the discrepancy is the strong temperature dependence of reaction 2, as CH4 oxidation by OH occurs much more rapidly in the warmer lower atmosphere. Assuming that the OHeff from CH3Cl is correct (as it is lower and in agreement with previous global estimates), we may determine at which temperature (and therefore which altitude) CH4 oxidation mainly occurs. By this method, we calculate that most tropospheric oxidation of CH4 occurs at circa 7 km (4.5 ~ 10.5 km, 220 ~ 260 K). OH radical abundance reaches an optimum just above the boundary layer (2–4 km) where the water concentration and photon fluxes are high and the flux of reactive sink species from the surface is decreasing. In addition, a second OH optimum occurs in the outflow region of clouds (10 km)32 where uplifted and lightning generated NOx enhances OH levels through the reaction of HO2 with NO. Therefore the 4.5 ~ 10.5 km height derived in this study likely represents an average of the effects of both OH maxima regions. This empirical estimate concurs with the model derived report that OH concentrations are at maximum in the free troposphere owing to recycling by NOx.6 A recent global modeling study using comprehensive chemistry6 suggests that OH is relatively high in the 4.5–10.5 km altitude range, which was attributed to OH recycling rather than primary formation. The model derived distribution is supported by this work.
Figure 3 shows the annual Cl radical concentration derived from air samples with age larger than 200 days in the stratosphere over the time period 2010–2015. The average Cl concentration over all periods is 1.1 (±0.6) × 104 molecules cm−3. Even though this result is five times higher compared to a 24 h average Cl concentration of 2.40 × 103 molecules cm−3 for 14–18.5 km height,33 it is more comparable to lower stratospheric Cl concentration of 5 × 103–3 × 104 molecules cm−3 estimated by CO/C2H6 ratio.34 Our result is also in close agreement with a recent model estimation35 based on isotopic ratios of methane and CO that yielded 1.6 × 104 molecules cm−3 for the lowermost stratosphere. No significant variation during this timeframe is observed in our dataset, although in 2013 Cl concentrations were lower than in the other years. Note that due to other minor loss processes (e.g., reaction with O1D, photodissociation36) in the stratosphere and mesosphere for both molecules, there is a slight overestimation of stratospheric Cl concentration. Mean, median, and one standard deviation data are given in Table 1(b).
Figure 4 presents the annual average stratospheric OHr as a function of sampling year rather than the mean air age shown in Fig. 2. Data are from samples with age larger than 200 days to be classed as stratospheric. The overall stratospheric OHr of 1.1 (±0.8) × 105 molecules cm−3 for the years 2010–2015 is derived. Median average OH values generally vary within 0.8 – 1.3 × 105 molecules cm−3 with an exceptionally low median value of 5.4 × 104 in the year 2014, statistical details see Table 1(c). No clear trend is apparent in the dataset, and the highest value was found for 2013.
## Discussion
This study presents a new empirical method of monitoring the effective OH concentration in the global troposphere and lower stratosphere over long periods. The method also delivers the mean altitude range for tropospheric CH4 oxidation and the effective Cl radical concentration in the lower stratosphere. These parameters are all useful measures of the overall atmospheric oxidizing capacity and markers for future circulation changes. Provided that high quality, long-term monitoring of these three gases continues, the impact of future global events can be assessed in these terms. For example, a volcanic eruption, a change in global CFC emission rates, or a change in stratospheric circulation patterns can lead to changes in ultraviolet radiation, stratospheric chlorine loading, and water vapor, all of which can significantly impact the derived metrics.
This method is built on three key assumptions. The first is that both CH3Cl and CH4 are predominantly oxidized by OH. While this is true for the troposphere and the lower stratosphere, over longer timescales (>500 days) air masses can be expected to also enter the upper stratosphere as part of the Brewer-Dobson circulation. At these higher altitudes a minor photolysis sink for CH3Cl and the reaction of O1D radicals with CH4 could lead to a small overestimation of the calculated effective OH. Indeed, in Fig. 2 a tendency to higher OHeff in older air can be seen in the CH4 derived OH results. By only considering data within certain age ranges (0–100 days troposphere and 200–400 days lower stratosphere) the impact of additional loss mechanisms is limited. The second assumption is that this time segregation does delineate troposphere (0–100 days), mixed troposphere–stratosphere (100–200 days) and stratosphere (>200 days). This assumption is supported by the trend in OH variability measured in the three categories. The third assumption made here is that the tropospheric effective OH using CH3Cl is correct and CH4 derived OH is high because of either Cl radicals (in the stratosphere) or the temperature dependence of the reaction (in the troposphere). Support for this assumption comes from the fact that the CH3Cl estimate is lower than that of CH4 (additional chemistry leads to overestimation), no other significant loss rates are known, and the CH3Cl estimate more closely matches the most recent global model studies.
Uncertainties and sensitivities of this method are important to consider. Different to variations which show statistical distributions of the results, uncertainties are the differences between the measured values and the true values, whereas sensitivities represent how much output values will be affected by the input values. Firstly, there is an instrumental uncertainty. By considering the measurement errors of SF6, CH4, CH3Cl measurements at ground level and by aircraft and reaction rates kOH and kCl, measurement uncertainties are calculated by error propagation for mean age, OHeff derived from CH4 and CH3Cl, stratospheric Cl and stratospheric OHr of 8%, 10%, 22%, 35%, and 37%, respectively. Secondly the choice of the source region could influence the calculation. An ideal tracer for the mean age calculation should be well mixed in the source region so that its mixing ratio time series can be used to derive initial concentrations. Since SF6 is not perfectly well mixed globally (i.e., there is a weak NH/SH gradient and a slight latitude dependence in each hemisphere), an average mixing ratio should be applied to represent the source region. Therefore, we chose the average SF6 mixing ratio in the northern hemisphere (NH) as determined by the NOAA network since our samples were collected in northern mid-latitudes. The mean age results were also derived from individual source regions, namely Mauna Loa (MLO, 19.5°N), Cape Matatula (SMO, 14.3°S), Niwot Ridge (NWR, 40.052°N), Pt. Barrow (BRW, 71.3°N), Mace Head (MHD, 53°N) and 20°S to 20°N region, but the overall average NH SF6 observation gave the most positive mean age values for our aircraft measurements. A ± 0.05 ppt difference of SF6 mixing ratios in different tropospheric source regions corresponds to 0.17 years difference for the derived mean age. Thirdly, we consider the sensitivity of calculation to the temperature-dependent reaction rates. We use two temperatures (216 and 250 K) to represent the average temperatures in the troposphere and stratosphere. By varying these temperatures by ±5 K, the reaction rate of the reaction CH3Cl + OH is less sensitive (variation of −14 ~ 11%) than that of the reaction CH4 + OH (variation of −17 ~ 33%) (see Table S1 in the Supplementary Material). Fourthly, sensitivity of seasonal cycles of CH4, CH3Cl in source region. Both CH4, CH3Cl have seasonal cycles in the troposphere with amplitudes of ca. 1% and 5%, respectively. When examining their temporal concentration in the lowermost stratosphere (Fig.S2 in the Supplementary Material) with the N2O concentration,37 seasonal variations of CH4 have been damped out (linear correlation in each N2O group) while those of CH3Cl are attenuated but still visible. By varying ±5% of CH3Cl in the source region, the OHeff of samples with age ~ 70 days and larger than 700 days change ~ 80% and ~ 25%, respectively. Finally, in this study OH is calculated as a second-order reaction (see Eqs. 2 and 3 in Method). Alternatively one can use the pseudo first order approach in which OH is assumed to be constant Ac = Ag*exp( – Γ*k*OH) (6) and this produces fractionally higher values (<1%).
It should be noted that the now well established methyl chloroform (MCF)-derived global mean OH requires several important assumptions, for example, concerning MCF emissions (at least before 2000), ocean uptake and stratospheric loss. Furthermore, MCF is declining rapidly as emissions have stopped, and it does not provide height information, nor indications about Cl abundance. Other relatively long-lived halocarbons have been considered to complement the MCF method, but these OH estimates are also dependent on the source estimates. Therefore, our new, independent method should be acknowledged as an important complementary source of information on OH and Cl.
The radical abundances derived here represent multiday average effective concentrations that are derived directly from long lived atmospheric gas measurements. Therefore, this work provides an important ground truth dataset for comparison with modeling approaches, and oxidant levels that can be used in conjunction with rate coefficients to derive lifetime estimates for other atmospheric species. This valuable information is obtained from relatively inaccessible regions using measurements of only three molecules. Provided the aircraft and ground-based measurements continue, then future OH and Cl oxidant changes induced by major volcanos or stratospheric circulation changes should be captured by applying this method. This work provides the empirical methodological approach and the baseline for future studies.
## Methods
### Dataset
Whole air samples of IAGOS-CARIBIC (In-service Aircraft for a Global Observing System-Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) were collected at 10–12 km in canisters during four flights monthly since 2008 and non-methane hydrocarbons and greenhouse gases were analyzed in laboratory at the Max Planck Institute for Chemistry, Mainz, Germany.38 Flight paths are shown in Fig. 1(b). SF6, CH4, and CH3Cl data of CARIBIC project were analyzed23,38,39,40 using GC-ECD (for SF6) and GC-FID (for CH4 and CH3Cl) with measurement precisions of 1.5%, 0.17%, and 1%, respectively. Ground station SF6 data was taken from the monthly northern hemispheric NOAA/ESRL halocarbons flask program. CH4 data is from the hourly NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network at Mauna Loa41 and CH3Cl data from the daily NOAA/ESRL halocarbons in situ program. NOAA used GC-FID for CH4 and GC-ECD for SF6 with precisions of 0.5% (SF6),42 0.2% (CH4),43 respectively.
### Mean age calculation
SF6 is a long-lived industrial tracer with estimated global emissions of 7.4 ± 0.6 Gg/year44 and has negligible sinks in the troposphere and stratosphere. Consequently, the atmospheric mixing ratio of SF6 has been observed to increase steadily for the past three decades45 with a growth rate of 0.27 ppt/year. In several previous studies, this species has been used to determine the “mean age” of air samples collected at altitude.27,46,47,48 This “mean age” is the term given to the time since the SF6 mixing ratio measured from the aircraft is equivalent to the SF6 measured in the surface source region, or in other words it indicates the average transit time between air leaving the surface until it is measured. We used the monthly northern hemispheric SF6 observations from NOAA/ESRL halocarbons flask program as the initial SF6 concentrations and a second-order polynomial fitting was applied for the time series (years 2005–2016) of SF6 mixing ratio. Then we applied SF6 mixing ratios by aircraft measurements to the fitting and found out the initial emission time. The difference of sampling time and initial emission time is the mean age. We excluded samples with calculated age less than 0 day (2.3% of total samples) that arise due to the higher mixing ratios of SF6 in extratropical troposphere than that in the tropics.26 The spatial distribution of mean age can be found in Fig. 1(b). Absolute counts for each mean age group are shown in Fig. S1 in the Supplementary Material.
### Effective OH calculation
The effective OH concentration [OH]eff was calculated according to equation (1).
$${\mathrm{[OH]}}_{{\mathrm{eff}}}{\mathrm{ = }}\frac{{{\mathrm{[A]}}_{\mathrm{g}}{\mathrm{ - [A]}}_{\mathrm{c}}}}{{{\mathrm{\Gamma }} \cdot k_{{\mathrm{OH + A}}} \cdot {\mathrm{[A]}}_{\mathrm{g}}}}$$
(1)
Where Γ is the mean age, [A]c is the mixing ratio of a compound A (in this case either CH4 or CH3Cl) sampled aloft by the CARIBIC aircraft at time t, and [A]g is the mixing ratio of A observed from the ground station at time t – Γ. Thus, [A]g−[A]C equates to the average loss of A during a time period of Γ, and kOH+A is the second-order reaction rate of compound A with the OH radical, which is calculated for two temperatures (216 K for Γ < 100 days and 250 K for Γ > 100 days) corresponding to 11 km and 40 km height.49 In this calculation we assume that air with Γ < 100 days has experienced predominately tropospheric conditions (average temperature of 216 K), whereas air with Γ > 100 days will have been transported to the stratosphere (average temperature of 250 K).
The reactions and associated rates31,50,51 are as follows:
$${\mathrm{CH}}_{\mathrm{4}}{\mathrm{ + OH}} \to {\mathrm{CH}}_{\mathrm{3}}{\mathrm{ + H}}_{\mathrm{2}}{\mathrm{O}}$$
(2)
($$k_{{\mathrm{OH}} + {\mathrm{CH}}_4,\,216{\mathrm{K}}} = 6.9 \times 10^{ - 16}\,{\mathrm{cm}^{3}}{\mathrm{s}^{{ - 1}}};\,k_{{\mathrm{OH}} + {\mathrm{CH}_{4}},\,250{\mathrm{K}}}$$ = $$2.06 \times 10^{ - 15}\,{\mathrm{cm}^{3}}{\mathrm{s}^{{ - 1}}}$$)
$${\mathrm{CH}}_{\mathrm{3}}{\mathrm{Cl} + {\mathrm{OH}}} \to {\mathrm{CH}}_{\mathrm{2}}{\mathrm{Cl} + {\mathrm{H}}}_{\mathrm{2}}{\mathrm{O}}$$
(3)
($$k_{{\mathrm{OH}} + {\mathrm{CH}_{3}{\mathrm{Cl}}},\,216{\mathrm{K}}} = 6.13 \times 10^{ - 15}\,{\mathrm{cm}^{3}}{\mathrm{s}^{{ - 1}}};\,k_{{\mathrm{OH}} + {\mathrm{CH}_{3}{\mathrm{Cl}}},\,250{\mathrm{K}}}$$ = $$1.48 \times 10^{ - 14}\,{\mathrm{cm}^{3}}{\mathrm{s}^{{ - 1}}}$$)
### Stratospheric Cl and OH radical calculation
Effective OH concentrations for the lower stratosphere, see Fig. 1, were consistently higher when calculated from CH4, similar to the tropospheric values described above. However, in the stratosphere, the differential reaction rate of Cl with CH4 and CH3Cl is a viable explanation for the relatively constant offset in calculated OHeff as chlorine radical production at high altitudes (>10 km) occurs over wide areas due to photolysis of chlorine containing compounds. For this calculation, we assume loss of CH4 (or CH3Cl):
$$k_{{\mathrm{OH}} + {\mathrm{A}}} \cdot {\mathrm{[OH]}}_{\mathrm{r}} + k_{{\mathrm{Cl} + {\mathrm{A}}}} \cdot {\mathrm{[Cl] = }}k_{{\mathrm{OH} +{\mathrm{ A}}}} \cdot {\mathrm{[OH]}}_{{\mathrm{eff} - {\mathrm{A}}}}$$
(4)
where [OH]r is the real OH concentration in the stratosphere, [Cl] is the chlorine radical concentration, [OH]eff-A is the effective OH derived from compound A in this study. Applying Eq. 4 for CH4 and CH3Cl, then [Cl] can be expressed as:
$${\mathrm{[Cl]}} = \frac{{{\mathrm{[OH]}}_{{\mathrm{eff - CH}}_{\mathrm{4}}} - {\mathrm{[OH]}}_{{\mathrm{eff - CH}}_{\mathrm{3}}{\mathrm{Cl}}}}}{{\frac{{{\mathrm{}}k_{{\mathrm{Cl + CH}}_{\mathrm{4}}}}}{{{\mathrm{}}k_{{\mathrm{OH + CH}}_{\mathrm{4}}}}} - \frac{{{\mathrm{}}k_{{\mathrm{Cl + CH}}_{\mathrm{3}}{\mathrm{Cl}}}}}{{{\mathrm{}}k_{{\mathrm{OH + CH}}_{\mathrm{3}}{\mathrm{Cl}}}}}}}$$
(5)
The ratios of k(Cl)/k(OH) are taken as 24 and 10 for CH4 and CH3Cl at 250 K, respectively.
### Data availability
The CARIBIC dataset that support the findings of this study are available from the corresponding author upon reasonable request. Ground station data can be found under URL: ftp://ftp.cmdl.noaa.gov/hats/sf6/combined/HATS_global_SF6.txt (for SF6), ftp://aftp.cmdl.noaa.gov/data/trace_gases/ch4/in-situ/surface/mlo/ch4_mlo_surface-insitu_1_ccgg_HourlyData.txt (for CH4), and ftp://aftp.cmdl.noaa.gov/data/hats/methylhalides/ch3cl/insituGCs/CATS/hourly/mlo_CH3Cl_All.dat (for CH3Cl).
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## References
1. 1.
Lelieveld, J. et al. Atmospheric oxidation capacity sustained by a tropical forest. Nature 452, 737–740 (2008).
2. 2.
Montzka, S. A. et al. Small interannual variability of global atmospheric hydroxyl. Science 331, 67–69 (2011).
3. 3.
Patra, P. K. et al. Observational evidence for interhemispheric hydroxyl-radical parity. Nature 513, 219–223 (2014).
4. 4.
Levy, H. Normal atmosphere: Large radical and formaldehyde concentrations predicted. Science 173, 141–143 (1971).
5. 5.
Heard, D. E. & Pilling, M. J. Measurement of OH and HO2 in the Troposphere. Chem. Rev. 103, 5163–5198 (2003).
6. 6.
Lelieveld, J., Gromov, S., Pozzer, A. & Taraborrelli, D. Global tropospheric hydroxyl distribution, budget and reactivity. Atmos. Chem. Phys. 16, 12477–12493 (2016).
7. 7.
Hard, T. M., Chan, C. Y., Mehrabzadeh, A. A., Pan, W. H. & O’Brien, R. J. Diurnal cycle of tropospheric OH. Nature 322, 617 (1986).
8. 8.
Stimpfle, R. M. & Anderson, J. G. In-situ detection of OH in the lower stratosphere with a balloon borne high repetition rate laser system. J. Geophys. Res. 15, 1503–1506 (1988).
9. 9.
Wennberg, P. O. et al. Aircraft-borne, laser-induced fluorescence instrument for the in situ detection of hydroxyl and hydroperoxyl radicals. Rev. Sci. Instrum. 65, 1858–1876 (1994).
10. 10.
Perner, D. E. et al. OH-Radicals in the lower troposphere. Geophys. Res. Lett. 3, 466–468 (1976).
11. 11.
Eisele, F. L. & Tanner, D. J. J. Ion-assisted tropospheric OH measurements. J. Geophys. Res. 96, 9295–9308 (1991).
12. 12.
Felton, C. C., Sheppard, J. C. & Campbell, M. J. Measurements of the diurnal OH cycle by a 14C-tracer method. Nature 335, 53–55 (1988).
13. 13.
Mckeen, S. A., Trainer, M., Hsie, E. Y., Tallamraju, R. K. & Liu, S. C. On the indirect determination of atmospheric OH radical concentrations from reactive hydrocarbon measurements. J. Geophys. Res. 95, 7493–7500 (1990).
14. 14.
Blake, N. J. et al. Estimates of atmospheric hydroxyl radical concentrations from the observed decay of many reactive hydrocarbons in well-defined urban plumes. J. Geophys. Res.: Atmos. 98, 2851–2864 (1993).
15. 15.
Williams, J. et al. Variability-lifetime relationship for organic trace gases: A novel aid to compound identification and estimation of HO concentrations. J. Geophys. Res.: Atmos. 105, 20473–20486 (2000).
16. 16.
Williams, J., Gros, V., Bonsang, B. & Kazan, V. HO cycle in 1997 and 1998 over the southern Indian Ocean derived from CO, radon, and hydrocarbon measurements made at Amsterdam Island. J. Geophys. Res.: Atmos. 106, 12719–12725 (2001).
17. 17.
Rigby, M. et al. Role of atmospheric oxidation in recent methane growth. Proc. Natl Acad. Sci. USA 114, 5373–5377 (2017).
18. 18.
Prinn, R. G. et al. Evidence for variability of atmospheric hydroxyl radicals over the past quarter century. Geophys. Res. Lett. 32, https://doi.org/10.1029/2004gl022228 (2005).
19. 19.
Krol, M. & Lelieveld, J. Can the variability in tropospheric OH be deduced from measurements of 1,1,1-trichloroethane (methyl chloroform)? J Geophys. Res.: Atmos. 108, https://doi.org/10.1029/2002jd002423 (2003).
20. 20.
Montzka, S. & Reimann, S. (Coordinating Lead Authors) et al. Ozone-Depleting Substances (ODSs)and Related Chemicals, in Scientific Assessment of Ozone Depletion: 2010, Ch. 1 (World Meteorological Organization: Geneva, Switzerland, 2011).
21. 21.
Yokouchi, Y., Ikeda, M., Inuzuka, Y. & Yukawa, T. Strong emission of methyl chloride from tropical plants. Nature 416, 163–165 (2002).
22. 22.
Santee, M. L., Livesey, N. J., Manney, G. L., Lambert, A. & Read, W. G. Methyl chloride from the Aura Microwave Limb Sounder: First global climatology and assessment of variability in the upper troposphere and stratosphere. J. Geophys. Res.: Atmos. 118, 13,532–513,560 (2013).
23. 23.
Umezawa, T. et al. Methyl chloride in the upper troposphere observed by the CARIBIC passenger aircraft observatory: Large-scale distributions and Asian summer monsoon outflow. J. Geophys. Res.: Atmos. 119, 5542–5558 (2014).
24. 24.
Baker, A. K. et al. Estimating the contribution of monsoon-related biogenic production to methane emissions from South Asia using CARIBIC observations. Geophys. Res. Lett. 39, https://doi.org/10.1029/2012gl051756 (2012).
25. 25.
Turner, A. J., Frankenberg, C., Wennberg, P. O. & Jacob, D. J. Ambiguity in the causes for decadal trends in atmospheric methane and hydroxyl. Proc. Natl Acad. Sci. USA 114, 5367–5372 (2017).
26. 26.
Bönisch, H., Engel, A., Curtius, J., Birner, T. & Hoor, P. Quantifying transport into the lowermost stratosphere using simultaneous in-situ measurements of SF6 and CO2. Atmos. Chem. Phys. 9, 5905–5919 (2009).
27. 27.
Ray, E. A. et al. Improving stratospheric transport trend analysis based on SF6 and CO2 measurements. J. Geophys. Res.: Atmos. 119, 14110–114128 (2014).
28. 28.
Garny, H., Birner, T., Bönisch, H. & Bunzel, F. The effects of mixing on age of air. J. Geophys. Res.: Atmos. 119, 7015–7034 (2014).
29. 29.
Orbe, C. et al. Airmass origin in the Arctic. Part I: Seasonality. J. Clim. 28, 4997–5014 (2015).
30. 30.
Baker, A. K. et al. Evidence for strong, widespread chlorine radical chemistry associated with pollution outflow from continental Asia. Sci. Rep. 6, 36821 (2016).
31. 31.
DeMore, W. B. S. et al. Chemical kinetics and photochemical data for use in stratospheric modeling. Eval. Number 12, 1–266 (1997).
32. 32.
Lange, L. et al. Detection of lightning-produced NO in the midlatitude upper troposphere during STREAM 1998. J. Geophys. Res.: Atmos. 106, 27777–27785 (2001).
33. 33.
Park, S. et al. Vertical transport rates and concentrations of OH and Cl radicals in the Tropical Tropopause Layer from observations of CO2 and halocarbons: implications for distributions of long- and short-lived chemical species. Atmos. Chem. Phys. 10, 6669–6684 (2010).
34. 34.
Lelieveld, J. et al. Chlorine activation and ozone destruction in the northern lowermost stratosphere. J. Geophys. Res.: Atmos. 104, 8201–8213 (1999).
35. 35.
Gromov, S., Brenninkmeijer, C. A. M. & Jöckel, P. A very limited role of tropospheric chlorine as a sink of the greenhouse gas methane. Atmos. Chem. Phys. 18, 9831–9843 (2018).
36. 36.
Minschwaner, K. & Manney, G. L. Derived methane in the stratosphere and lower mesosphere from Aura Microwave Limb Sounder measurements of nitrous oxide, water vapor, and carbon monoxide. J. Atmos. Chem. 71, 253–267 (2015).
37. 37.
Boering, K. A. et al. Stratospheric mean ages and transport rates from observations of carbon dioxide and nitrous oxide. Science 274, 1340 (1996).
38. 38.
Brenninkmeijer, C. A. M. et al. Civil aircraft for the regular investigation of the atmosphere based on an instrumented container: The new CARIBIC system. Atmos. Chem. Phys. 7, 4953–4976 (2007).
39. 39.
Schuck, T. J., Brenninkmeijer, C. A. M., Slemr, F., Xueref-Remy, I. & Zahn, A. Greenhouse gas analysis of air samples collected onboard the CARIBIC passenger aircraft. Atmos. Meas. Tech. 2, 449–464 (2009).
40. 40.
Baker, A. K., Slemr, F. & Brenninkmeijer, C. A. M. Analysis of non-methane hydrocarbons in air samples collected aboard the CARIBIC passenger aircraft. Atmos. Meas. Tech. 3, 311–321 (2010).
41. 41.
Dlugokencky, E. J., Crotwell, A. M., Lang, P. M. & Mund, J. W. Atmospheric methane dry air mole fractions from quasi-continuous measurements at Mauna Loa, Hawaii, 1986–2016, Version: 2017-01-20, Path: ftp://aftp.cmdl.noaa.gov/data/trace_gases/ch4/in-situ/surface/. (2017).
42. 42.
Hall, B. D. et al. Improving measurements of SF6 for the study of atmospheric transport and emissions. Atmos. Meas. Tech. 4, 2441–2451 (2011).
43. 43.
Dlugokencky, E. J., Steele, L. P., Lang, P. M. & Masarie, K. A. The growth rate and distribution of atmospheric methane. J. Geophys. Res.: Atmos. 99, 17021–17043 (1994).
44. 44.
Rigby, M. et al. History of atmospheric SF6 from 1973 to 2008. Atmos. Chem. Phys. 10, 10305–10320 (2010).
45. 45.
IPCC. Climate Change 2007: Mitigation. Contribution of Working Group III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (eds Metz, B., Davidson, O. R., Bosch P. R., Dave R., Meyer L. A.). (Cambridge, United Kingdom and New York, NY, USA, 2007).
46. 46.
Waugh, D. Age of stratospheric air: Theory, observations, and models. Reviews of Geophysics 40, https://doi.org/10.1029/2000rg000101 (2002).
47. 47.
Engel, A. et al. Age of stratospheric air unchanged within uncertainties over the past 30 years. Nat. Geosci. 2, 28–31 (2008).
48. 48.
Hall, T. M. & Plumb, R. A. Age as a diagnostic of stratospheric transport. J. Geophys. Res.: Atmos. 99, 1059–1070 (1994).
49. 49.
National Oceanic Atmospheric Administration. U.S. Standard Atmosphere, 1976. (U.S. Government Printing Office: Washington, D.C., United States of America, 1976).
50. 50.
Srinivasan, N. K., Su, M. C., Sutherland, J. W. & Michael, J. V. Reflected shock tube studies of high-temperature rate constants for OH+CH4 ->CH3+H2O and CH3+NO2 ->CH3O+NO. J. Phys. Chem. A 109, 1857–1863 (2005).
51. 51.
Atkinson, R. Kinetics of the gas-phase reactions of OH radicals with alkanes and cycloalkanes. Atmos. Chem. Phys. 3, 2233–2307 (2003).
## Acknowledgements
We would like to thank Claus Koeppel for the routine maintenance and construction and installation of the whole air sampling system, Angela Baker, Tanja Schuck, Ute Thorenz, and Carina Sauvage for conducting the measurements, Hao Fang (INRIA, France) for the programming support. CARIBIC is part of the European Research Infrastructure IAGOS, which is financed partly by the German Ministry for Education and Research (BMBF 01LK1223). Operation of the CARIBIC observatory is possible through the support and cooperation of Lufthansa and Lufthansa Technik and Frankfurt and Munich airports. We would also like to thank Stephen A. Montzka (for thoughtful comments), Ed Dlugokencky, Geoffrey S. Dutton, and James W. Elkins from NOAA for providing the following data: the NOAA/ESRL GMD network for ground station SF6 data, the NOAA ESRL Carbon Cycle Cooperative Global Air Sampling Network for ground station CH4 data and the NOAA/ESRL halocarbons in situ program for ground station CH3Cl data. This work was funded by the Max Planck Society internal funds.
## Author information
### Affiliations
1. #### Max Planck Institute for Chemistry, 55128, Mainz, Germany
• Mengze Li
• , Einar Karu
• , Carl Brenninkmeijer
• , Horst Fischer
• , Jos Lelieveld
• & Jonathan Williams
### Contributions
M.L. and J.W. developed the idea. M.L., J.W., E.K., H.F., J.L., and C.B. wrote the manuscript. C.B. is the CARIBIC lead scientist and oversaw planning and execution of measurement flights and the provision of aircraft data. All authors discussed the results and commented on the manuscript.
### Competing interests
The authors declare no competing interests.
### Corresponding author
Correspondence to Jonathan Williams.
|
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|
http://link.springer.com/article/10.1007%2Fs10539-004-7044-0
|
, Volume 20, Issue 4, pp 697-713
Parsimony and the Fisher–Wright debate
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Abstract
In the past five years, there have been a series of papers in the journal Evolution debating the relative significance of two theories of evolution, a neo-Fisherian and a neo-Wrightian theory, where the neo-Fisherians make explicit appeal to parsimony. My aim in this paper is to determine how we can make sense of such an appeal. One interpretation of parsimony takes it that a theory that contains fewer entities or processes, (however we demarcate these) is more parsimonious. On the account that I defend here, parsimony is a ‘local’ virtue. Scientists’ appeals to parsimony are not necessarily an appeal to a theory’s simplicity in the sense of it’s positing fewer mechanisms. Rather, parsimony may be proxy for greater probability or likelihood. I argue that the neo-Fisherians appeal is best understood on this interpretation. And indeed, if we interpret parsimony as either prior probability or likelihood, then we can make better sense of Coyne et al. argument that Wright’s three phase process operates relatively infrequently.
|
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http://mathhelpforum.com/calculus/7142-definition-limit.html
|
# Thread: Definition of Limit
1. ## Definition of Limit
There's a similar post on this, but I can't understand it and it seems flawed. So I'll try this one.
How do you prove that the lim (as x approaches a) of x^2=a^2?
2. Are you familiar with the delta-epsilon defintion of a limit? I don't want to go into it if it's not what you're looking for.
3. Yes I am.
4. Here's a good site that proves $\lim_{x \to 1}x^2+3=4$ It uses the same method so unless you want I won't type it all out.
http://www.math.ucdavis.edu/~kouba/C...l#SOLUTION%204
5. Thank you. Very helpful.
6. Ok. So the only thing I don't get now as how it works for something like the example I had where the limit equals a variable (also the number the limit is approaching is a variable). I'm having trouble making the connection from the problem I had to ones with real numbers.
How do you show abs(x^2-a^2) is less than epsilon?
|
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https://arxiv-export-lb.library.cornell.edu/abs/2104.11089?context=cond-mat.other
|
cond-mat.other
(what is this?)
# Title: Intrinsic vibrational angular momentum from non-adiabatic effects in non-collinear magnetic molecules
Abstract: We show that in non-collinear magnetic molecules, non-adiabatic (dynamical) effects due to the electron-vibron coupling are time-reversal symmetry breaking interactions for the vibrational field. As in these systems the electronic wavefunction can not be chosen as real, a nonzero geometric vector potential (Berry connection) arises. As a result, an intrinsic nonzero vibrational angular momentum occurs even for non-degenerate modes and in the absence of external probes. The vibronic modes can then be seen as elementary quantum particles carrying a sizeable angular momentum. As a proof of concept, we demonstrate the magnitude of this topological effect by performing non-adiabatic first principles calculations on platinum clusters and by showing that these molecules host sizeable intrinsic phonon angular momenta comparable to the orbital electronic ones in itinerant ferromagnets.
Comments: 5 pages, 3 figures, to appear on Physical Review Letters Subjects: Chemical Physics (physics.chem-ph); Other Condensed Matter (cond-mat.other) DOI: 10.1103/PhysRevLett.126.225703 Cite as: arXiv:2104.11089 [physics.chem-ph] (or arXiv:2104.11089v1 [physics.chem-ph] for this version)
## Submission history
From: Oliviero Bistoni [view email]
[v1] Thu, 22 Apr 2021 14:10:10 GMT (941kb,D)
Link back to: arXiv, form interface, contact.
|
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https://www.physicsforums.com/search/849561/
|
# Search results
1. ### Irrational Numbers
H - Many thanks for a really helpful post! Maybe what I'm exploring is to do with the boundary between mathematical formalism and realism. I'm now a little more clear about one or two things and I'll shut up about this now. Btw - re the primes - I'll stop bothering you about this also. I've...
2. ### Irrational Numbers
Hurkyl? Anybody? I'm getting a little bit paranoid at the lack of response. Was that not an appropriate question here? I suppose it's not exactly a mathematical question. Or is it? It wasn't a trap anyway. I was trying to understand how mathematicians see these issues, exactly where they feel...
3. ### Irrational Numbers
Thanks. (I was careful to add 'in the everyday sense' when I used these words.) That's how I imagine points are usually defined, as the end point of a never ending process. I assume that they simply have to be defined in this sort of way. It's the issues this raises that interest me. Very...
4. ### Irrational Numbers
Hurkyl - I think I can accept what you say (and I do) without it altering my general point, which comes exactly from trying to understand what parts of the object really do correspond to the math and what parts are simply errors of approximation. For most objects there may be no problem being...
5. ### Irrational Numbers
Oh yes. I see. Thanks. In that case it's a good point. But I wouldn't agree.
6. ### Irrational Numbers
Differently to what? Damn silly question is the answer most people would give.
7. ### Irrational Numbers
Yes. Is it not a surreal fantasy about infinitely thin knives that produces a useable definition for infinitely 'thin' numbers? Whether such numbers exist (or whether numbers can be coherently defined in this way), I was suggesting, can be determined from examining the definition. I suppose...
8. ### Irrational Numbers
For me the question is not whether these numbers exist but what they actually are. Whether they exist would seem to depend on how we define them.
9. ### Is it possible to simplify the RH problem?
Okay CRG, I've decided to book some tuition in order to get to grips with the issues and will stop bothering you. I need to take a few steps back before trying to go forward again. Many thanks for your patience. Much appreciated. Regards Pete
10. ### Is it possible to simplify the RH problem?
Thanks - even if it's all hieroglyphics to me. I realise it's a struggle to talk about this with a mathematical duffer. I was wondering whether proving the zeros behave in a certain way is equivalent to proving that the relevant inputs have certain properties. But even if this question is...
11. ### Is it possible to simplify the RH problem?
Yes. Simplifying problems is a hobby. It works for the TPC, Russell's paradox and many other problems, (and it kept my business alive through many a crisis). I was wondering if it would work for RH. Seems highly unlikely at this point. CRG - For you the point about inputs and outputs may not...
12. ### Is it possible to simplify the RH problem?
I like to think I could understand a lot of the maths, yes, given time, but I know I could never understand all that would be required for this problem. I'm in complete awe of anyone who can understand it. I suppose I was asking if the zeta function is a map between inputs and outputs, such...
13. ### Is it possible to simplify the RH problem?
Thanks. I realise Goedel diagonalization is standard stuff. Couldn't understand the equations, which are also probably standard stuff. The last point seems slightly off-track since I don't want to prove that zeta has certain properties. My thought was that zeta merely reveals properties...
14. ### Irrational Numbers
Forgetting the OP then, I'd like to ask something about this. I see that a region may be well-defined, so that being a region would not necessarily entail that a number is ill-defined. (Is this what you meant?) But... couldn't we say it is ill-defined when we forget that it's is a region and...
15. ### Irrational Numbers
I can't follow most of this, but is there not a sense in which all numbers are ill-defined in the sense that they represent a region on the number line that can never be reduced to a point? In this way could the OP's question be something to do with the relationship between a continuum and a...
16. ### Is it possible to simplify the RH problem?
Hello everybody. It's my first post and I'm not a mathematician so please bear with me. I'll try to make it vaguely interesting. I'm fascinated by the problem of deciding the Riemann Hypothesis. The trouble is, I'm not clever enough to understand it. The zeta function may as well be martian...
|
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|
https://www.infoq.com/articles/microservices-kotlin-ktor/
|
InfoQ Homepage Articles Tutorial: Writing Microservices in Kotlin with Ktor—a Multiplatform Framework for Connected Systems
# Tutorial: Writing Microservices in Kotlin with Ktor—a Multiplatform Framework for Connected Systems
### Key Takeaways
• Ktor is an OSS Apache 2 project created and maintained by JetBrains.
• It can be used for creating asynchronous connected systems.
• Ktor makes heavy use of Kotlin features, including coroutines and language constructs.
• It is low-ceremony in that it requires very little code and configuration to get a system up and running.
• Ktor is multi-platform and can run on a variety of systems and server container technology.
## What is Ktor?
Ktor (pronounced Kay-tor) is a framework built from the ground up using Kotlin and coroutines. It gives us the ability to create client and server-side applications that can run and target multiple platforms. It is a great fit for applications that require HTTP and/or socket connectivity. These can be HTTP backends and RESTful systems, whether or not they’re architectured in a microservice approach.
Ktor was born out of inspiration from other frameworks, such as Wasabi and Kara, in an aim to leverage to the maximum extent some of the language features that Kotlin offers, such as DSLs and coroutines. When it comes to creating connected systems, Ktor provides a performant, asynchronous, multi-platform solution.
Currently, the Ktor client works on all platforms Kotlin targets, that is, JVM, JavaScript, and Native. Right now, Ktor server-side is restricted to the JVM. In this article, we’re going to take a look at using Ktor for server-side development.
## Ktor on the server
The equivalent of a Hello World application with Ktor would be
fun main() {
val server = embeddedServer(Netty, 8080) {
routing {
get("/home") {
call.respondText("Hello Ktor!", ContentType.Text.Plain)
}
}
}
server.start(true)
}
If you have experience with frameworks, such as ExpressJS or Sinatra, this code might seem familiar. First we’re creating an instance of a server that is using Netty as the underlying engine and listening on port 8080.
The next step is to define an actual route to respond to a request. In this case, we’re saying that when a request is made to the URL /home, the server should respond by sending the text Hello Ktor! in plain text.
Finally, we start the server and tell it to wait, thus preventing our application from immediately terminating.
That’s as simple as it gets when it comes to Ktor. If we want to add more routes, in principle all we’d need to do is define more HTTP verbs, along with the corresponding URLs in the routing function. For instance, if we’d like to respond to POST, we’d simply add another function.
routing {
get("/") {
call.respondText("Hello Ktor!", ContentType.Text.Plain)
}
post("/home") {
// Act on request
}
}
### Functions everywhere
In case you’re not familiar with Kotlin, you may be wondering what these constructs are, and where do all the magic words, such as call, come from. Let’s break it down a little bit.
routing, get, and post are all higher-order functions (that is, functions that take functions as parameters or return functions). In this case, we’re talking about taking functions as parameters. Kotlin also has a convention that if the last parameter to a function is another function, we can place this outside of the brackets (and if it’s the only parameter, we drop these all together).
In our case, routing is not just a higher-order function, but it’s what’s known as a lambda with receiver in Kotlin. This is a higher-order function that takes as parameter an extension function, which essentially means that anything enclosed within routing has access to members of the type named Routing.
This type in turn has functions, such as get and post, which in turn are also lambdas with receivers, with their own members, such as call. This simple combination of functions and conventions in Kotlin allow for the ability to create elegant DSLs, and in the case of Ktor, this is used for defining routes.
## Features
Features are something Ktor provides that enable support for certain functionality, such as encoding, compression, logging, authentication, etc.
If we think of the request/response pipeline, we can think of features as interceptors that intervene during the different phases and provide their specific functionality. In some frameworks these are actually known as middleware, or event interceptors.
A feature consists of two parts:
• Initialization, which is used for configuring the functionality required. This part is optional.
• Execution, which handles the actual interception and work being done on the request and response.
To use a feature, we’d generally just install it and optionally configure anything required. Beyond that, the feature itself would handle the execution part. For instance, if we need content negotiation, which not only provides content negotiation itself, but also does the encoding, we’d simply call install(ContentNegotiation) in the set-up of our application.
fun Application.jsonSample() {
install(ContentNegotiation) {
gson {
setPrettyPrinting()
serializeNulls()
}
}
routing {
get("/customer") {
val model = Customer(1, "Mary Jane", "[email protected]")
call.respond(model)
}
}
}
In this case, the feature also has an initialization part which is configuring the GSon library and setting the properties. With that call alone, the application now supports content negotiation and encoding to JSON. As such, a call to /customer would send back the Customer object in JSON format.
You may have noticed that in the diagram above, Routing was displayed as if it were a feature. Routing, in fact, is also a feature in Ktor, and much like any other feature, must be installed. However, instead of calling install(Routing), we would usually use the higher-order function routing, which is what we’ve been using. In fact, if we look at the implementation of this function, we see that it calls install(Routing).
fun Application.routing(configuration: Routing.() -> Unit): Routing =
featureOrNull(Routing)?.apply(configuration) ?: install(Routing, configuration)
Content negotiation and routing are just two examples of features. The Ktor web site lists dozens of other features that ship out of the box with the framework. However, it’s also very simple to implement new features — essentially, all that’s needed is to implement one class where we define the initialization and execution phase. To learn more, check out the source code for the Content Negotiation feature covered above.
## Structuring applications
When developing applications, we usually have a series of endpoints that are responsible for different areas of the system. For instance, take a regular CRM — we can have Customer, Sales, Proforma endpoints. With many MVC frameworks, these are usually grouped in different classes commonly suffixed with Controller. We’d have CustomerController, ProformaController, each of them responding to their /customer and /proforma endpoints respectively.
How would we define and group these in Ktor? What definitely wouldn’t work is setting up all the routes in the single application initialization block, let alone in a single file.
Ktor provides us with the flexibility to define our routes in any way we want, and organize them as we wish. While this obviously has the benefit of giving us complete freedom, it also raises the question, especially to newcomers, of what’s the best way.
As any developer/consultant/IT expert would know, the answer of course is it depends. We can organize cohesive routes in a single file. We can create folders and then have each endpoint in its own file. We can group by feature. It really is up to us.
Another aspect of it is how to define the routes, i.e., do we just create top-level functions? A good approach is to make route definitions extensions to the Route class, as seen below:
fun Route.home() {
get("/") {
call.respondText("Index Page")
}
}
}
}
This gives immediate access to the different verbs such as get, post, put, delete, option, head. To then use these route definitions, we can simply call each function in the application initialization code.
fun Application.structureSample() {
routing {
home()
}
}
### Route hierarchies
Ktor also allows us to define routes hierarchically. This means that instead of having to do something along the lines of
get("/customer/") {
}
post("/customer/") {
}
we could do
route("customer") {
get {
}
post {
}
}
In fact, each route itself could also define a new URL if needed.
route("customer") {
get("/list") {
}
post {
}
}
Again, demonstrating the flexibility of the framework.
## Rendering Data
We’ve seen prior how to send back text as well as JSON. What about when we want something more sophisticated, whether this is HTML or using a view engine?
### Server-Side Rendering
With Ktor we can render data directly from the server using many approaches. One of these is with Kotlinx.HTML which is a DSL for creating statically-typed HTML. This allows us to leverage the full power of Kotlin, combining data with control flow. The example below demonstrates iteration over a series of elements
fun Application.htmlSample() {
routing {
get("/html-dsl") {
call.respondHtml {
body {
h1 { +"HTML" }
ul {
for (n in 1..10) {
li { +"$n" } } } } } } } } ### Templating Engines Many applications today, whether they are Single Page Applications or not, make use of templating engines. Out of the box, Ktor supports a variety of these, including Freemaker, Thymleaf, Velocity, and Mustache, amongst others. They are implemented as features, so in order to use them, all we’d need to do is install them as part of the initialization phase of the application. ## Working with route parameters and fields So far we’ve seen how to define simple routes and respond with text. A web application however needs to send information as part of the request. These can be either as part of the URL (route parameters), as query fields (everything following the ?), or part of the body (for instance, in the case of POST and PUT). How would we process these from Ktor? ### Routing Parameters When it comes to route parameters, we can access these using the call.parameters property. get("/customer/{id}") { call.respondText(call.parameters["id"].toString()) } ### Query Fields In the case of query fields, these can be accessed using the call.request.queryPameters property. get { call.respondText(call.request.queryParameters["id"].toString()) } ### Post Fields When it comes to post fields, Ktor has support for multipart form-data built in. We can simply access these entries using the multipart property. post("/form") { val multipart = call.receiveMultipart() multipart.forEachPart { part -> when (part) { is PartData.FormItem -> appendln("Form field:$part = ${part.value}") is PartData.FileItem -> appendln("File field:$part -> ${part.originalFileName} of${part.contentType}")
}
part.dispose()
}
}
### Leveraging static typing with Location
One thing you may have noticed in the examples that work with route parameters, as with all routing definitions, is the use of strings. While generally this is absolutely fine, and tools, such as IntelliJ IDEA, can refactor strings if needed; another approach that Ktor provides is to use strongly-typed route definitions.
In Ktor, this route definition is called Location. We can use classes to define them, using the class name as the name of the location and class properties as the route parameters. As convention, the class names are defined in lowercase.
@Location("/") class index()
@Location("/employee/{id}") class employee(val id: String)
fun Application.locations() {
install(Locations)
routing {
get<index> {
call.respondText("Routing Demo")
}
get<employee> { employee ->
call.respondText(employee.id)
}
}
}
In addition to providing type-safety, when it comes to defining routes, it also allows for strongly-typed access to actual route parameters, as can be seen in the case of employee.id. Which ultimately means that the compiler will catch any errors while typing the name of route parameters.
## Configuration
In the very first example, we saw how we’d started the application using server.start, creating an embedded server using Netty. While this works great for demos, usually we’d want to externalize the configuration of our server, allowing the ability to define parameters, such as the port, without needing to recompile.
This is how we’d usually deploy and configure applications, and in fact, all of the other examples in this article use this approach. For instance, if we look at the example around JSON
fun Application.jsonSample() {
routing {
get("/customer") {
val model = Customer(1, "Mary Jane", "[email protected]")
call.respond(model)
}
}
}
We notice that there is no embeddedServer or server.start call, i.e., the main entry point of the application is missing. It’s not in fact missing, but defined elsewhere.
fun main(args: Array<String>): Unit = io.ktor.server.netty.EngineMain.main(args)
This single line essentially tells our application to start using the Netty engine, but to read the configuration parameters from the command line argument, and if not, fallback to a file named application.conf. This file is defined using HOCON (Human-Optimized Config Object Notation, a subset of JSON). A typical configuration file would look like so:
ktor {
deployment {
port = 8080
port = \${?PORT}
}
application {
modules = [ jsonSample ]
}
}
where modules indicates the actual application to load (in the previous case would be jsonSample). Ktor applications can actually load multiple modules, where each module could represent an area of functionality.
As mentioned early on, one of Ktor’s goals is to make both client and server available on all platforms. The client already offers this functionality. At JetBrains, we’re working on providing the missing pieces to make this a possibility for the server. One of these is to offer an alternative to engines, such as Netty and Jetty, which can now be used to run Ktor server applications. There is work already underway to provide a fully-coroutine based solution, which is currently offered as experimental under CIO.
At JetBrains, we are fully committed to Ktor. Not only do we continue to work on it, but we also have skin in the game, if you will, as our recently announced product JetBrains Space is built on Ktor.
If you want to find out more about Ktor, make sure you check out ktor.io.
Hadi Hariri is a developer and creator of many things OSS. His passions include Web Development and Software Architecture. He has authored a couple of books, a few courses, and has been speaking at industry events for nearly 20 years. Hariri is currently at JetBrains leading the Developer Advocacy team and he spends as much time as he can writing code.
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• ##### Spring-KTor
by Vishnu Pedireddi /
• ##### Spring-KTor
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@Hadi Hariri: For the engineers with Kotlin/Spring background - How would you highlight KTor against the backdrop of the Spring framework? Thanks for the article on the framework. It was informative.
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{"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 1, "mathjax_display_tex": 0, "mathjax_asciimath": 1, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0, "katex": 0, "math-container": 0, "wp-katex-eq": 0, "align": 0, "equation": 0, "x-ck12": 0, "texerror": 0, "math_score": 0.2744984030723572, "perplexity": 2964.8339207262857}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 5, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "plain"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "warc_path": "s3://commoncrawl/crawl-data/CC-MAIN-2020-29/segments/1593655891654.18/warc/CC-MAIN-20200707044954-20200707074954-00260.warc.gz"}
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http://scitation.aip.org/content/aip/journal/jcp/138/5/10.1063/1.4775807
|
• journal/journal.article
• aip/jcp
• /content/aip/journal/jcp/138/5/10.1063/1.4775807
• jcp.aip.org
1887
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Reaction coordinates, one-dimensional Smoluchowski equations, and a test for dynamical self-consistency
USD
10.1063/1.4775807
View Affiliations Hide Affiliations
Affiliations:
1 Department of Chemical Engineering, University of California, Santa Barbara, California 93106, USA
2 Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, USA
3 van ‘t Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090 GD Amsterdam, The Netherlands
J. Chem. Phys. 138, 054106 (2013)
/content/aip/journal/jcp/138/5/10.1063/1.4775807
http://aip.metastore.ingenta.com/content/aip/journal/jcp/138/5/10.1063/1.4775807
## Figures
FIG. 1.
Schematic depicting a projection of short trajectory swarm data (gray) from an initial point x 0 (black) to specific coordinates q 1 and q 2 at later times.
FIG. 2.
For a reaction coordinate whose dynamics follow a one-dimensional Smoluchowski equation, swarms of trajectories from different individual configurations on each isosurface will drift and diffuse similarly. Therefore, for each isosurface, the projection of the individual swarms should each resemble the combined projection of all swarms (depicted to the right of the free energy surface). In the case depicted above, the individual swarms behave differently from each other, and therefore differently from their combined projection.
FIG. 3.
If the dynamics of q follow a one-dimensional Smoluchowski equation, dynamical self-consistency should apply at all isosurfaces of q. (Left) For a poor reaction coordinate q(x) the value of q alone is not a good predictor of drift or diffusion from the configuration x. (Right) If q shows dynamical self-consistency for all isosurfaces of q from reactant A to product B, then q is an accurate reaction coordinate.
FIG. 4.
The solid curves are contours of the actual free energy landscape βF(q 1, q 2) with a saddle point at the round dot. The coordinate q 1 has been used as the initial coordinate, i.e., λ(x) = q 1(x). The dotted contours are curves of constant Λ. Note that Λ is peaked where the original landscape had a saddle point.
FIG. 5.
The free energy landscape for a model of nucleation where the nucleus size can change along either fast (n F ) and slow (n S ) mobility directions.
FIG. 6.
The free energy as a function of the initial coordinate λ = n F + n S .
FIG. 7.
Histograms of endpoints of 1000 trajectories 2.0τ after initiation. Each figure shows nine swarms initiated at nine different points on the free energy landscape. In (a) the anisotropy is s = 1.0, and in (b) the anisotropy is s = 0.1. Differences in the way the swarms drift are difficult to visually discern, but the dynamical self-consistency test can detect differences.
FIG. 8.
The trial reaction coordinate q can be represented by the angle θ between the direction of progress along q and the n F -axis.
FIG. 9.
exp[−Λ] weighted Kullback-Leibler divergences for different trial reaction coordinates (represented by θ) and for different values of the diffusion anisotropy, s = 1.0, 0.3, 0.1, 0.03.
FIG. 10.
Illustrating three mechanistic regimes that prevail for different degrees of diffusion anisotropy. When s ≈ 1, the diffusion tensor is isotropic and most pathways follow the minimum free energy path. When s < 1, but not extremely small, a two step nucleation mechanism prevails with initial motion along the slow coordinate before escape in the n F -direction. Finally, when s is extremely small the Berezhkovskii-Zitserman (BZ) regime prevails. In the BZ-regime, trajectories can escape in the n F -direction with the n S degree of freedom frozen.
FIG. 11.
Narrow tube type free energy landscape as a function of fast (n F ) and slow (n S ) coordinates. The saddle point is at (n F , n S ) = (20, 20).
FIG. 12.
Projections of the free energy onto different initial coordinates. (a) The initial coordinate was λ = n S . (b) The initial coordinate was λ = n F .
FIG. 13.
⟨ΔKL[q]⟩Λ for different coordinates (represented by the angle θ as shown in Figure ). (a) The initial coordinate was λ = n S . (b) The initial coordinate was λ = n F . In both cases the optimal coordinate (the minimum) rotates toward n S as the diffusion tensor becomes more anisotropic.
FIG. 14.
Contour plots of (a) the EVB potential V(x, y) with the minimum energy path between the reactant and product minima, (b) the potential Λ(x, y) constructed with λ chosen as the end-to-end direction along the minimum energy path, and (c) the potential Λ(x, y) constructed with the ideal energy gap coordinate for λ. Contour spacings are 5kBT in all plots.
FIG. 15.
⟨ΔKL[q]⟩Λ for different linear trial coordinates q(x, y) represented by the angle θ. The initial coordinate λ(x, y) gives a hysteretic free energy Fλ(λ) if sampled imperfectly. Coordinates similar to λ clearly do not have dynamical self-consistency, but other coordinates are not clearly distinguished in ⟨ΔKL[q]⟩Λ.
FIG. 16.
⟨ΔKL[q]⟩Λ for different linear trial coordinates q(x, y) represented by the angle θ. The initial coordinate λ(x, y) is the vertical energy gap between diabatic states of the EVB model.
## Tables
Table I.
Comparison between reaction coordinates from the dynamical self-consistency test and from KLBS theory. Coordinates identified by dynamical self-consistency are summarized for two different initial coordinates. For narrow tube potential energy landscapes the dynamical self-consistency test can correctly identify accurate reaction coordinates even for an inaccurate initial coordinate λ.
/content/aip/journal/jcp/138/5/10.1063/1.4775807
2013-02-01
2014-04-23
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https://tex.stackexchange.com/questions/3755/math-input-panel-in-windows-7-and-latex-writing
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# Math Input Panel in Windows 7 and LaTeX writing
I just found out about the Math Input Panel in Windows 7,and now there is commercial software using it for LaTex writing. For example Inlage. If you have a look of their first demo video, you know what I am talking about: http://www.inlage.com/videos
I had a try with the Math Input Panel myself, and it seems you can basically write all math stuff, integration, super(sub) scripts, tensor, arrows (even with labels over them!), and matrix! The only big problem is there is NO commutative diagram. And it probably has trouble recognizing some math fonts, like \mathfrak or \mathcal. But in all, it really recognize handwritings pretty well. I don't have a writing pad, so I just tried writing with a mouse.
I know there are people taking math notes using a tablet PC. Won't this tool drastically improve the quality of our note-taking? It basically changes all handwriting into TeX files!
Maybe I am too late on this, are there more mature product for such purposes? I think handwriting math could actually be slower than typing LaTeX codes. But one good reason for doing handwriting is because sometimes I just don't like to make math writing into code writing (or something like programming). I would like to hear about your comments. Thank you!
• the main question, is to see if anyone here has such kind of experiences, namely, handwriting TeXing... – bas Oct 4 '10 at 6:56
• The math panel is really cool, like all of Microsoft's math stuff. However it is still quite new, and I don't know anybody that uses it right now. Concerning speed, I think some people are faster with linear input, some are faster with handwriting recognition. See e.g. this post by Murray: blogs.msdn.com/b/murrays/archive/2009/05/07/… – Philipp Oct 4 '10 at 8:32
I'm the developer of Inlage and I think the Windows 7 MIP is a great tool but it can't handle a many special things. But the possibilities are good for doing a lot of math stuff. For testing that tool I tried to write a 2 hour lecture of relativistic quantum mechanics down with a graphic tablet. It was possible but I had some problems. So I just replaced some symbols it couldn't handle. But natural it wasn't faster than handwriting...
But I think another nice idea to use the MIP is if you dont know the latex command of a symbol you can easily write it down (only the symbol, with mouse) in the MIP and get the command.
TexTablet performs the main feature of the program mentioned above: translates handwritten math into LaTeX. It's based on the Windows 7 Math Input. You hand-write the formulas on the Math Input Panel, but the results get translated into LaTeX.
Also, it's free of cost.
• I should add that I really like this product and yet I never use it. I almost always just type the LaTeX. I have never stopped typing out a LaTeX project to write out a particularly complicated formula using this product instead. – Henry B. Oct 26 '10 at 15:30
• So then you don't find it useful, do you? – Hendrik Vogt Oct 27 '10 at 8:17
• @Hendrik. It seems useful in theory, but rarely (for me) in practice. I modified my answer. – Henry B. Oct 27 '10 at 9:38
Writing notes on a tablet during a math class is likely to be a real loser unless you have some disability that makes using a pencil especially difficult compared to using a stylus. I don't know what that disability might be.
Since MIP or other tablet-based math input is error prone, and even a 10% error rate would be low, you will, in the midst of your math class be spending 50% or more of your time and a corresponding percentage of your mental capacity grappling with the error correction mechanism of MIP (or whatever).
As a (now retired) math and computer science professor, my experience with students who typeset their notes (and homework) when not at all required, is that they rarely if ever learn the material better.
If you are not using MIP, but simply using a tablet as a simulation of paper (no recognition) then I suppose there is this tradeoff:
pro: you are maybe saving some trees by not using paper. Also saving graphite? you could send your notes digitally to some archive or some friend with a computer. you could, maybe later, try to scan and recognize the math, without involving scanning or photographing paper.
con: you are writing on a piece of glass, which is uncomfortable. you can't look back at a previous page without invoking some command.
alternative: take a photo of the blackboard in your class. Or if you are already taking a class via computer, take a screen grab and store it.
Sadly, the neat technology of handwriting recognition of mathematics is not nearly as useful as it seems at first. Peculiarly, I have found that speaking mathematics is not as error prone, and has the distinct advantage of not requiring hands. Richard Fateman http://www.cs.berkeley.edu/~fateman
• Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. It may be a personal opinion of mine (and I certainly don't want to start an argument), but maybe the first sentence could be rephrased to appear more “politically correct”... – Pier Paolo Jan 11 '15 at 18:48
I'm not totally sure I understand your question. I've never tried hand writing TeX; that seems odd to me.
I have taken notes in LaTeX before. My general strategy was to invent macros as needed while taking notes. The first time I needed a "set x to be a uniformly random element of set S" macro, I just wrote \rgets. At the end of the class, my notes didn't compile, but I'd just go through and define the macros I had invented during the note taking.
I never tried it with a math class like algebraic geometry (I just used pencil and paper for math classes), but that strategy worked quite well for an advanced crypto class I took in grad school.
This is a really old Q/A, but I thought I'd mention that MathPaper, not to be confused with a commercial product by the same name, is the best I have found at recognizing handwritten mathematics. It has a feature whereby you can, subsequent to recognition (which happens in real-time), copy to the clipboard the equivalent LaTeX code. I use it on a tablet PC.
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http://math.stackexchange.com/questions/198830/proving-that-a-sequence-is-decreasing
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# Proving that a sequence is decreasing
How could I prove the following statement without using induction? I've been staring at this for the better part of an hour. (To be fair, I'm not very good at proof writing) Thanks in advance!
Define a sequence $a_n, n \ge 0,$ inductively by $a_0 = 2,$ and for all $n \ge 0, a_{n+1} = \sqrt{a_n + 1}.$
Using the fact that the polynomial $x^2 - x - 1 < 0$ if and only if $\frac{1-\sqrt{5}}{2} < x < \frac{1+\sqrt{5}}{2}$, prove that for every $n \ge 0, a_n > a_{n+1}.$
-
Why don't you want to use induction? Can you see how to do it using induction? – Ben Millwood Sep 19 '12 at 1:07
The hint will actually be used in the induction step. – Brian M. Scott Sep 19 '12 at 1:11
Really? Well, thank you for clarifying that before I set out to solve this! I actually wasn't aware that we had to use it here at all. – user41419 Sep 19 '12 at 1:12
Since you’re dealing with non-negative number, $a_{n+1}>a_n$ if and only if $a_{n+1}^2>a_n^2$. But $a_{n+1}^2=a_n+1$, so $a_{n+1}>a_n$ if and only if $a_n+1>a_n^2$, i.e., if and only if $a_n^2-a_n-1<0$. In other words, your sequence decreases from $a_n$ to $a_{n+1}$, which you don’t want, if and only if $a_n^2-a_n-1<0$. The last line of the problem reminds you of just when this is true. Can you now show that it’s never true?
You will actually be using induction: you’ll be showing that if $a_{n+1}\not> a_n$, then $a_{n+2}\not>a_{n+1}$.
Since $a_n>0$ for all $n$, it is enough to show that $a_n^2>a_{n+1}^2$. But this is equivalent to $a_{n}^2-a_{n+1}^2>0$, and we see that $a_{n}^2-a_{n+1}^2=a_n^2-a_n-1$, so we need only show that $a_n>\frac{1+\sqrt 5}{2}$. This is easy to show using induction, since $a_0>\frac{1+\sqrt 5}{2}$ and if $a_n>\frac{1+\sqrt 5}{2}$ then $$a_{n+1}>\sqrt{\frac{1+\sqrt 5}{2}+1}=\frac{1+\sqrt 5}{2}$$ so by induction it is true for all $n$. Induction is definitely the right technique to use, since your sequence is defined inductively.
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http://gmatclub.com/forum/can-anyone-send-me-the-link-to-sc-1000-i-need-to-start-70583.html?fl=similar
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Can anyone send me the link to SC 1000 I need to start
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http://ajayshahblog.blogspot.com/2011/10/household-behaviour-that-counteracts.html
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## Saturday, October 22, 2011
### Household behaviour that counteracts fiscal expansion
Suppose a government tries to boost demand in the economy by boosting the deficit.
A fascinating feature of the situation is: Households are not wood, households are not stones, but men. And being men, they will look forward, they will optimise. Households know that all government expenditure requries taxation: all that is achieved by running a deficit today is postponing taxes to tomorrow.
India's fiscal stance is now likely to lead to increased taxation in the future. We have a nice wide deficit today, but it's increasingly likely that fresh taxation will come up in the future.
A core feature of human beings is that we do not like to deal with fluctuations in our consumption. So faced with the prospect of taxation tomorrow, we are prone to cut back on consumption today.
Through this, when a government raises the deficit today, some of this effect is counteracted by households that pull back on expenditure. Raising the fiscal deficit is less expansionary than some would think.
Economists have a fancy name for this: it's called Ricardian Equivalence. This was originally thought up by David Ricardo, but made famous by Robert Barro. It is one of the many ways in which forward looking households are of essence in thinking about macroeconomics. "You are not wood, you are not stones, but men; and being men, you will optimise".
Please note: LaTeX mathematics works. This means that if you want to say $10 you have to say \$10.
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https://www.physicsforums.com/threads/another-question-regarding-radioactive.76281/
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1. May 20, 2005
### Sanosuke Sagara
I have my doubt , solution and the question in the attachment that followed.
Thanks for anybody that spend some time on this question.
#### Attached Files:
File size:
55.5 KB
Views:
37
2. May 20, 2005
### learningphysics
I think you made some careless errors.
I'd like to write out the equations...
$$\frac{-dn}{dt} = 5000(\frac{1}{2})^{t/8}$$ where t is in hours
Just plug in t=1 into the right side and you get your answer for a. 4585
If we integrate both sides we get
$$n(t) = -\frac{5000}{ln(1/2)}(\frac{1}{2})^{t/8}$$ or
$$n(t) = \frac{5000}{ln(2)} (\frac{1}{2})^{t/8}$$
Now since the time in the equations are hours... there's no need to convert to seconds.
n(0) = 5000/ln(2) = 7213
n(1) = (5000/ln(2)) (1/2)^(1/8) = 6615
So for b) n(0) - n(1) = 598
c) She comes back 24 hours later. So in the equation we'll need to plug in t=25 (24 hours after t=1) to see how much of the radioactive stuff is left.
n(25) = (5000/ln(2)) (1/2)^(25/8) = 827
To get the same treatment she needs to get 598 atoms just like part b). So the total needs to come down from 827 to 827-598=229 after the second treatment is finished
We solve n(t) = 229, I get t=40 hours.
So the second treatment starts at t=25 hours, and finished t=40 hours to get 15 hours of treatment.
Check the work yourself. I might have made some careless errors.
Last edited: May 20, 2005
3. May 21, 2005
### Sanosuke Sagara
Thanks for your explaination and comment to me for my unneccasary confusing way of calculation.I think I have understand what the question want and I will try to find out the answer.Thanks again,learningphysics.
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https://www.gktoday.in/question/the-angles-of-a-triangle-are-latex-x5circ-2x-3circ
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The angles of a triangle are $(x+5)^{\circ}, (2x-3)^{\circ}$ and $(3x+4)^{\circ}.$ The value of x is :
[A] 28
[B] 29
[C] 30
[D] 31
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https://brilliant.org/discussions/thread/extremely-weird-integration/
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# Extremely Weird Integration.
(y^2 - 1)^2 = y^4 - 2y^2 + 1 . Aren't both equation the same? Why after integration , the answers become different?
Can anyone explain it?
Note by 柯 南
2 years, 7 months ago
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The integration of $$(y^2-1)^2$$ is incorrect. You seem to have used something similar to the chain rule of differentiation, which is not applicable to integration. The correct way to do it would be to expand and continue as you did on the left hand side.
- 2 years, 7 months ago
(I'm a student in malaysia) but the formula is in d text book ? Are there ways to do that without expanding ?
- 2 years, 7 months ago
Could you please post a picture of the formula in your textbook? And no, there's no quicker way. However, if you write the integral as the limit of an infinite summation, you will obtain the correct answer but after a lot of tedious calculation.
- 2 years, 7 months ago
Sorry , not text book , it's reference book. Maybe they wrote it wrong.
Thank you so much :D , i wondered about it for so many days
- 2 years, 7 months ago
- 2 years, 7 months ago
The integration of (y^2 - 1)^2 is incorrect. therefore you got different computation
- 2 years, 7 months ago
You can not divide by 2y, that only works when the derivative of the inside is a constant. In your case it was 2y which is not a constant. Hope that helps
- 2 years, 7 months ago
Thank you. That was a clear explanation !
(btw , why 2y is not constant ? Isit because y^2 can be ± ？
- 2 years, 7 months ago
I check both so many times , can't find anything wrong with it.
- 2 years, 7 months ago
You have performed the integral of $$(y^2-1)^2$$ incorrectly.
- 2 years, 7 months ago
What is the correct steps?
- 2 years, 7 months ago
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https://www.math3ma.com/blog/act-2019
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# Announcing Applied Category Theory 2019
Hi everyone. Here's a quick announcement: the Applied Category Theory 2019 school is now accepting applications! As you may know, I participated in ACT2018, had a great time, and later wrote a mini-book based on it. This year, it's happening again with new math and new people! As before, it consists of a five-month long, online school that culminates in a week long conference (July 15-19) and a week long research workshop (July 22-26, described below). Last year we met at the Lorentz Center in the Netherlands; this year it'll be at Oxford.
Daniel Cicala and Jules Hedges are organizing the ACT2019 school, and they've spelled out all the details in the official announcement, which I've copied-and-pasted below. Read on for more! And please feel free to spread the word. Do it quickly, though. The deadline is soon!
# ACT2019 School: Call for Participation
Oxford, UK. 2019, July 22 – 26
Dear scientists, mathematicians, linguists, philosophers, and hackers,
We are writing to let you know about a fantastic opportunity to learn about the emerging interdisciplinary field of applied category theory from some of its leading researchers at the ACT2019 School. It will begin February 18, 2019 and culminate in a meeting in Oxford, July 22-26. Applications are due January 30th; see below for details.
Applied category theory is a topic of interest for a growing community of researchers, interested in studying systems of all sorts using category-theoretic tools. These systems are found in the natural sciences and social sciences, as well as in computer science, linguistics, and engineering. The background and experience of our community’s members is as varied as the systems being studied.
The goal of the ACT2019 School is to help grow this community by pairing ambitious young researchers together with established researchers in order to work on questions, problems, and conjectures in applied category theory.
## Who should apply?
Anyone from anywhere who is interested in applying category-theoretic methods to problems outside of pure mathematics. This is emphatically not restricted to math students, but one should be comfortable working with mathematics. Knowledge of basic category-theoretic language—the definition of monoidal category for example—is encouraged.
We will consider advanced undergraduates, Ph.D. students, and post-docs. We ask that you commit to the full program as laid out below.
Instructions on how to apply can be found below the research topic descriptions.
## Senior research mentors and their topics
Below is a list of the senior researchers, each of whom describes a research project that their team will pursue, as well as the background reading that will be studied between now and July 2019.
#### Miriam Backens
Title: Simplifying quantum circuits using the ZX-calculus
Description: The ZX-calculus is a graphical calculus based on the category-theoretical formulation of quantum mechanics. A complete set of graphical rewrite rules is known for the ZX-calculus, but not for quantum circuits over any universal gate set. In this project, we aim to develop new strategies for using the ZX-calculus to simplify quantum circuits.
1. Matthes Amy, Jianxin Chen, Neil Ross. A finite presentation of CNOT-Dihedral operators. arXiv:1701.00140
2. Miriam Backens. The ZX-calculus is complete for stabiliser quantum mechanics. arXiv:1307.7025
#### Tobias Fritz
Title: Partial evaluations, the bar construction, and second-order stochastic dominance
Description: We all know that 2+2+1+1 evaluates to 6. A less familiar notion is that it can *partially evaluate* to 5+1. In this project, we aim to study the compositional structure of partial evaluation in terms of monads and the bar construction and see what this has to do with financial risk via second-order stochastic dominance.
1. Tobias Fritz, Paolo Perrone. Monads, partial evaluations, and rewriting. arXiv:1810.06037
2. Maria Manuel Clementino, Dirk Hofmann, George Janelidze. The monads of classical algebra are seldom weakly cartesian. Available here.
3. Todd Trimble. On the bar construction. Available here.
#### Pieter Hofstra
Title: Complexity classes, computation, and Turing categories
Description: Turing categories form a categorical setting for studying computability without bias towards any particular model of computation. It is not currently clear, however, that Turing categories are useful to study practical aspects of computation such as complexity. This project revolves around the systematic study of step-based computation in the form of stack-machines, the resulting Turing categories, and complexity classes. This will involve a study of the interplay between traced monoidal structure and computation. We will explore the idea of stack machines qua programming languages, investigate the expressive power, and tie this to complexity theory. We will also consider questions such as the following: can we characterize Turing categories arising from stack machines? Is there an initial such category? How does this structure relate to other categorical structures associated with computability?
1. J.R.B. Cockett, P.J.W. Hofstra. Introduction to Turing categories. APAL, Vol 156, pp 183-209, 2008. Available here.
2. J.R.B. Cockett, P.J.W. Hofstra, P. Hrubes. Total maps of Turing categories. ENTCS (Proc. of MFPS XXX), pp 129-146, 2014. Available here.
3. A. Joyal, R. Street, D. Verity. Traced monoidal categories. Mat. Proc. Cam. Phil. Soc. 3, pp. 447-468, 1996. Available here.
#### Bartosz Milewski
Title: Traversal optics and profunctors
Description: In functional programming, optics are ways to zoom into a specific part of a given data type and mutate it. Optics come in many flavors such as lenses and prisms and there is a well-studied categorical viewpoint, known as profunctor optics. Of all the optic types, only the traversal has resisted a derivation from first principles into a profunctor description. This project aims to do just this.
1. Bartosz Milewski. Profunctor optics, categorical View. Available here.
2. Craig Pastro, Ross Street. Doubles for monoidal categories. arXiv:0711.1859
Title: Formal and experimental methods to reason about dialogue and discourse using categorical models of vector spaces
Description: Distributional semantics argues that meanings of words can be represented by the frequency of their co-occurrences in context. A model extending distributional semantics from words to sentences has a categorical interpretation via Lambek's syntactic calculus or pregroups. In this project, we intend to further extendthis model to reason about dialogue and discourse utterances where people interrupt each other, there are references that need to be resolved, disfluencies, pauses, and corrections. Additionally, we would like to design experiments and run toy models to verify predictions of the developed models.
1. Gerhard Jager. A multi-modal analysis of anaphora and ellipsis. Available here.
2. Matthew Purver, Ronnie Cann, Ruth Kempson. Grammars as parsers: Meeting the dialogue challenge. Available here.
#### David Spivak
Title: Toward a mathematical foundation for autopoiesis
Description: An autopoietic organization—anything from a living animal to a political party to a football team—is a system that is responsible for adapting and changing itself, so as to persist as events unfold. We want to develop mathematical abstractions that are suitable to found a scientific study of autopoietic organizations. To do this, we’ll begin by using behavioral mereology and graphical logic to frame a discussion of autopoeisis, most of all what it is and how it can be best conceived. We do not expect to complete this ambitious objective; we hope only to make progress toward it.
1. Fong, Myers, Spivak. Behavioral mereology. arXiv:1811.00420.
2. Fong, Spivak. Graphical regular logic. arXiv:1812.05765.
3. Luhmann. Organization and Decision, CUP. (Preface)
## School structure
All of the participants will be divided up into groups corresponding to the projects. A group will consist of several students, a senior researcher, and a TA. Between January and June, we will have a reading course devoted to building the background necessary to meaningfully participate in the projects. Specifically, two weeks are devoted to each paper from the reading list. During this two week period, everybody will read the paper and contribute to discussion in a private online chat forum. There will be a TA serving as a domain expert and moderating this discussion. In the middle of the two week period, the group corresponding to the paper will give a presentation via video conference. At the end of the two week period, this group will compose a blog entry on this background reading that will be posted to the $n$-Category Cafe.
After all of the papers have been presented, there will be a two-week visit to Oxford University from 15 – 26 July 2019. The second week is solely for participants of the ACT2019 School. Groups will work together on research projects, led by the senior researchers.
The first week of this visit is the ACT2019 Conference, where the wider applied category theory community will arrive to share new ideas and results. It is not part of the school, but there is a great deal of overlap and participation is very much encouraged.
## How to apply
The application due date is 30 January 2019. To apply please send the following to [email protected]:
- A document with:
• an explanation of any relevant background you have in category theory or any of the specific projects areas
• the date you completed or expect to complete your Ph.D and a one-sentence summary of its subject matter.
• order of project preference
• to what extent can you commit to coming to Oxford (availability of funding is uncertain at this time)
- A brief statement (~300 words) on why you are interested in the ACT2019 School. Some prompts:
• how can this school contribute to your research goals?
• how can this school help in your career?
Also, have sent on your behalf to [email protected] a brief letter of recommendation confirming any of the following:
- ACT2019 School's relevance to your research/career
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https://ora.ox.ac.uk/objects/uuid:0cd3b710-927e-45dd-b0e7-64fa979bddb4
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Journal article
### Time resolved FTIR emission measurements of the internal energies of NO formed in the O(D-1)+N2O reaction, and energy transfer processes to N2O
Abstract:
Time resolved infrared emission from the fundamental and first overtone transitions of NO(v = 1-14), produced in the reaction of N2O with O(1D) has been analysed to determine the nascent vibrational distribution of NO. The electronically excited O atom was produced by the 193 nm laser photolysis of N2O. The measured vibrational distribution was found to be monotonically decreasing as a function of increasing v. Lower limits were determined for the average nascent rotational energy in v = 1-6,...
Publication status:
Published
Publisher copy:
10.1039/b300163f
### Authors
More by this author
Institution:
University of Oxford
Division:
MPLS
Department:
Chemistry
Sub department:
Physical & Theoretical Chem
Role:
Author
Journal:
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume:
5
Issue:
11
Pages:
2369-2375
Publication date:
2003-01-01
DOI:
EISSN:
1463-9084
ISSN:
1463-9076
Source identifiers:
38660
Language:
English
Pubs id:
pubs:38660
UUID:
uuid:0cd3b710-927e-45dd-b0e7-64fa979bddb4
Local pid:
pubs:38660
Deposit date:
2012-12-19
|
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https://www.gamedev.net/profile/43209-cignox1/?tab=friends
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# cignox1
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1. ## OpenGL which model import lib to use?
I've used Assimp several years ago for my pet project (not a game, but a raytracer). I've found it quite powerfull (yet not perfect) and I can only suppose it got better in the latest 5 years. I had a couple of issues with materials: I don't remember the details, but IIRC it was something annoying related to transparency/specularity which prevented me from using a couple of features of my RT. It was designed for real time rendering, though, so maybe those limitations were perfectly fine in such use cases.
2. ## [ray-tracer] Banding problems
Seems like you are loosing precision somewhere. Be sure all your deltas are in place and that you are using the correct scale for your scene.
3. ## making a program, all code in one file
Which are the advantages of a giant single room apartment over a more traditional one? Sure, you gain some space (no walls), but you loose privacy, rational furnishing, comfort ... Honestly, I don't see any real reason to write a (non trivial) application in a single file (I'm scared by the maintainance nightmare I would eventually address)
4. ## Pieces movements through graphs (Java)
Thank you for the link and the hint: I will certainly look into that bitboards thing to see if it is applicable to my game.
5. ## Pieces movements through graphs (Java)
Hi all, I'm developing a board game, kind of chess (Cyvasse, for those who know "A Song of Ice and Fire") and I would like the game to highlight valid target cells when the user select a piece. Ideally, pieces can move a max distance (say 4), where diagonal steps count as 2. Movements are 'free': as long as they are shorter than max allowed length, a piece can reach its target call the way it wants. Some cells may contain obstacles, the exact behaviour of which also depends upon the piece. My first idea was to use graphs to compute if a path exists: I build a graph with the cells inside the max distance contraint and then compute the shortest paths between src and target cells. For each of these paths I decide if it is valid (i.e, no obstacles are on the way) and if a valid one is found, I allow the move. First question: is that a good approach to start with? I tried by using the jgrapht library, with the KShortestPaths component. Simply too slow, apparently (several seconds for every target cell). Better would be to use the Bellman-Ford algo to simply compute the shortest path, but then I should compute valid edges when I build the graph, so tha every path found is a valid move. I'm not sure I can do this though: for example, some pieces cannot cross an obstacle, but they can stop on them. Others can cross an obstacle, but not rest there. I would rather avoid implementing everything by myself if possible, but this could be my only option. Before taking this route, I would like to hear your opinions. Thank you.
6. ## What language do I use?
Well, they could tell you which is the language (mostly) used to build core engines of games such as Crysis and the like. But as already said, that info will not make you a better coder, not will make you write your first games (which is something far more important).
7. ## OpenGL OpenGL or DirectX
Is it possible that he refers to the recent projects of Valve in regards with linux? Valve is currently trying to lead a move of the game industry towards linux, and this means that those developers willing to follow them have to use OGL. Is not yet clear whether or not that shift will happen...
8. ## A Song of Ice and Fire, and Dark Tower 4.5
ASOIAF is definitely a must read for anyone interested in fantasy (open minded). I've read it 3 times in italian and 1 time in english and it never ceases to impress me. I've found the last 2 books a bit disappointing (too slow and to many sub plots which really don't add anything to the story) but I guess its a consequence of the change to the initial plan (the year gap that should have occoured before TWOW and filled by Martin with these 2 books). The tv series is well done, but writers did a poor job for many charachters (mostly jon, dany and robb). And then there is Ros, may the Others take her...
9. ## Applying texture on a sphere [raytracing]
[quote name='Frénésie' timestamp='1338497298' post='4945085'] I have to specify a couple of vector to define the sphere ? On the 0.x axe and 0.y axe ? And is it on a cartesian reference ? [/quote] I think that you need to define at least the north (and perhaps even the west) vectors, so that rotations applied to the sphere reflect on the texture orientation...
10. ## Applying texture on a sphere [raytracing]
I don't have my code at the moment, but I remember that there is a simple addition to the intersection formula that gives u,v parameters of the intersection point. You just have to specify a couple of vectors defining the orientation of te sphere. Those uv can then be scaled/translated/rotated/clipped any way you want and in the end you do a get(u,v) on the texture (where u and v are presumably normalized so that 0 is completely left and 1 is completely right - same thing for top and bottom). Hope this helps
11. ## How to load a 3d model
The easier way (by far) is to pick one of the many 3ds or obj loaders out there. That will make you able to load simple objects created in Blender or in the 3d package of your choice. I also suggest to try Assimp, which supports several formats.
12. ## Path Tracing BSDF
I must say that you have indeed beatiful renders, wich would deserve more complex scenes (i.e. Sponza Atrium). If you have troubles with kd-trees and the like, try with something easier: BIH (Bounding interval hierarchy) is not as fast as kd-tree with SAH, but estimates suggest it is 60/70% its speed, so it may help you a lot, and is not so hard to implement (I did it as well, but I would rather not give you my implementation as for some reason it is really slow :-( You can find the paper by googling and the ompf.org forum used to have several threads on that topic, with many implementations discussed (included my own). Now the ompf.org domain no longer points to the forum, but a (temporary?) replacement has been opened. I don't know if those threads have been moved, but if you ask them they will help you. [quote] [color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][size=3][left]how should I go about simulating subsurface scattering (which is needed for realistic metal materials)[/left][/size][/font][/color] [color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][size=3][left][/quote][/left][/size][/font][/color] [color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][size=3][left]Honestly this is the first time I hear someone willing to implement SSS for metals (instead than skin, milk or marble) [/left][/size][/font][/color][color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][size=3][/size][/font][/color][color=#282828][font=helvetica, arial, verdana, tahoma, sans-serif][size=3][left][img]http://public.gamedev.net//public/style_emoticons/default/biggrin.png[/img][/left][/size][/font][/color] And you could consider buying the "Physically based Raytracing: from theory to implementation": I have the first edition and it is truly amazing. In the second (IIRC) the show how to implement both BVH and SSS. If you are interested in Raytracing/GI you should buy that book. Hope this helps
Hi all, in order to improve my PHP knowledge, I'm trying to build a small framework with the goal to use it to develop my music band site. I layed out a simple configuration class (just a placeholder actually):[php]<?php /* Class to handle all application wide Quarkweb configuration parameters. */ namespace quarkweb; class QWConfiguration { protected static $mClassName = "QWConfiguration"; //By changing this before the configuration is read, an application can force the use of a specified configuration class public function __construct() { //initialize the values } public static function getClassName() { return QWConfiguration::$mClassName; } public static function setClassName($aClassName) { QWConfiguration::$mClassName = $aClassName; } static public function getConfiguration() {$aClassName = QWConfiguration::getClassName(); $aClass = new$aClassName(); return \$aClass; } } ?>[/php] The idea is that it should work as a simple factory: the application sets the desidered class name for its own configuration and at the proper time an instance will be created. I've used the dynamic class instancing elsewhere without issues. But I get the following error: [b]Fatal error[/b]: Class 'QWConfiguration' not found in [b]C:\inetpub\wwwroot\quarkweb\core\qwconfiguration.php[/b] on line [b]28[/b] I bet this is one of those errors that any half-experienced PHP programmer will spot in two seconds. Any idea? Thank you!
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http://minhcuongvj.com/w5kzgd/trigonal-prismatic-bond-angles-a0be25
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These reactions can be classified as follows: Many reactions of octahedral transition metal complexes occur in water. CH3- is trigonal pyramidal with bond angles of slightly less than 109. For example, [Co(NH3)6]3+, which is not octahedral in the mathematical sense due to the orientation of the N-H bonds, is referred to as octahedral.[1]. Ammonia NH$_3$ is approximately a trigonal pyramid with bond angle $107.5$. Some molecules, such as XeF6 or IF−6, have a lone pair that distorts the symmetry of the molecule from Oh to C3v. Examples Portion of lattice of [Te 6](O 3 SCF 3) 2. Chem. The energy of the dz2 and dx2−y2, the so-called eg set, which are aimed directly at the ligands are destabilized. Coordination numbers are normally between two and nine, but large numbers of ligands are not uncommon for the lanthanides and actinides. Octahedral to trigonal prismatic distortion driven by subjacent orbital π antibonding interactions and modulated by ligand redox noninnocence. It is a very useful fact that if two vectors ${\bf u}$ and ${\bf v}$ have coordinates $(x_1, y_1, z_1)$ and $(x_2, y_2, z_2)$ then the cosine of the angle $\theta$ they make is The F—P—F bond angles in PF 5 are: 90° between an atom in the axial position and an atom in the equatorial position; 120° between two atoms in the equatorial position. Bond Angle : A molecule with an ideal Trigonal planar geometry has an angle of 120 o between the peripheral atoms. This problem makes use of vectors, coordinates and scalar products. $$Edge- and face-shared bioctahedra have the formulas [M2L8(μ-L)]2 and M2L6(μ-L)3, respectively. The entire model is approximately 200mm (8") tall compared to a similar model in Orbit style which is 70mm (~3") tall. A perfect trigonal pyramidal molecule is the same as a perfect tetrahedral molecule with a single outer atom removed. gaseous Ni2+ or Mo0, the energy of the d-orbitals are equal in energy; that is, they are "degenerate". Given that a virtually uncountable variety of octahedral complexes exist, it is not surprising that a wide variety of reactions have been described. temperature-dependent reaction? with trigonal-prismatic environment were obtained due to the use of non-innocent multi-chelating ligands and by ligand de-sign. Complex 12- with a twist angle of ca. The equatorial F atoms are 120 from each other., so the axial/equatorial bond angle is 90 degrees. What would be the maximum possible angle mathematically? Octahedral transition-metal complexes containing amines and simple anions are often referred to as Werner-type complexes. Ammonia, chlorate ion and sulfite ion. This reduces the symmetry of the molecule from Oh to D4h and is known as a tetragonal distortion. Ammonia NH_3 is approximately a trigonal pyramid with bond angle 107.5. Ammonia NH_3 is approximately a trigonal pyramid with bond angle 107.5. [3][4] The specific geometry is known as a monocapped octahedron, since it is derived from the octahedron by placing the lone pair over the centre of one triangular face of the octahedron as a "cap" (and shifting the positions of the other six atoms to accommodate it). A perfect trigonal pyramidal molecule is the same as a perfect tetrahedral molecule with a single outer atom removed. These angles are obtained when all five pairs of outer electrons repel each other equally. Does this correspond to a lengthening or shortening of the bonds relative to a perfect structure? The NRICH Project aims to enrich the mathematical experiences of all learners. View almost down the chain of titanium(III) iodide highlighting the eclipsing of the halide ligands in such face-sharing octahedra. The first one is 90 degrees and the second one is 120 degrees. There are also distorted trigonal prisms, with C3v symmetry; a prominent example is W(CH3)6. Some examples of the trigonal planar shape molecules would include: To support this aim, members of the For compounds with the formula MX6, the chief alternative to octahedral geometry is a trigonal prismatic geometry, which has symmetry D3h. For example, the [CoCl(NH3)5]2+ slowly aquates to give [Co(NH3)5(H2O)]3+ in water, especially in the presence of acid or base. NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to A strongly distorted trigonal‐prismatic C 3 v symmetry was found for [W(CH 3) 6], a regular trigonal‐prismatic symmetry for [Re(CH 3) 6], and both [Ta(CH 3) 6] − and [Nb(CH 3) 6] − show a slight distortion from an ideal trigonal prism. A perfect octahedron belongs to the point group Oh. All rights reserved. the acetylacetonate ligands is for each Mn-O bond almost the same, and lie in the range 2.1480(16) – 2.1580(18) Å. The entire model is approximately 150mm (6") tall compared to a similar model in Orbit style which is 70mm (~3") tall. The bond angle in a Trigonal pyramidal is around 107 o. The term can also refer to octahedral influenced by the Jahn–Teller effect, which is a common phenomenon encountered in coordination chemistry. The sharing of an edge or a face of an octahedron gives a structure called bioctahedral. Explore the possibilities for reaction rates versus concentrations What is the exact value of the bond angle in a perfect tetrahedron? 9.18° (trigonal prism, 0°; octahedron, 60°) agrees with the interpretations of computational studies on d0 complexes, which suggest that a nearly trigonal prismatic geometry is favored when the interaction between metal and ligand is primarily through σ-bonds. The loss of degeneracy upon the formation of an octahedral complex from a free ion is called crystal field splitting or ligand field splitting. 2014 , 50 (59) , 7956-7959. The unusual distorted trigonal‐prismatic structure reported recently for hexamethyltungsten is only the tip of the iceberg. Would the other bond angles increase or decrease under such a deformation? CH2=CHCH2OCH3. In this geometry, the six ligands are also equivalent. Phosphine-substituted trigonal-prismatic and octahedral clusters. It has three peripheral atoms around the central atom, all in one plane, and these three bonds are separated by 120 degrees bond angles. Tetrahedral: four bonds on one central atom with bond angles of 109.5°. The bite angles for each of the acetylacetonate ligands are also nearly identical, being 81.69(6)° (O1-Mn1-O2) and 81.92(6)° (O3-Mn1-O4). Bond angle(s) 90° μ (Polarity) 0: In ... For compounds with the formula MX 6, the chief alternative to octahedral geometry is a trigonal prismatic geometry, which has symmetry D 3h. (c), (d) Ta–Ta–Ta bonding (green) and Ta-Ta-Ta-Ta dihedral (magenta) angles for Ta Se 2 − x Te x solid solutions at 100 K. The Trigonal Planar shape is a type of shape which a molecule takes form of when three bonds point to corners of an equilateral triangle. The naming system for these isomers depends upon the number and arrangement of different ligands. embed rich mathematical tasks into everyday classroom practice. When two or more types of ligands (La, Lb, ...) are coordinated to an octahedral metal centre (M), the complex can exist as isomers. Ball-and-stick model of niobium pentachloride, a bioctahedral coordination compound. A perfect trigonal pyramidal molecule is the same as a perfect tetrahedral molecule with a single outer atom removed. Essentially, bond angles is telling us that electrons don't like to be near each other. Brian Heaton Dalton Transactions 2007 , 100 (42) , 4778. Metal tetrahalides often exist as polymers with edge-sharing octahedra. For example, the t2g and eg sets split further in trans-MLa4Lb2. Two motifs for fusing octahedra are common: edge-sharing and face-sharing. Nature is versatile and can make use of even seemingly exotic bonding situations. The trigonal pyramidalgeometry exists when there are 3 bonds and 1 lone pair. Coordination numbers are normally between two and nine, but large numbers of ligands are not uncommon for the lanthanides and actinides. The atoms in this VSEPR Large Classroom Model set can assume any geometry. The term "octahedral" is used somewhat loosely by chemists, focusing on the geometry of the bonds to the central atom and not considering differences among the ligands themselves. Find the scalar products between the vectors joining the origin to each atom and hence the value of h. If the central atom is at the coordinate origin and the molecule rests on the plane z=-h then what would be the coordinates of the other atoms, assuming a bond length of 1 unit? For MLa4Lb2, two isomers exist. Ball-and-stick model of molybdenum(III) bromide, an inorganic polymer based on face-sharing octahedra. As well, for an ideal trigonal prism, there will be three faces containing four coordinating atoms, the dihedral angles between these faces being 60°, while the angles between any three coordinating nitrogen atoms being either 60° (all three atoms in the triangular face) or 90°(all three … S4.4 Comparison of angles between LT and 1,3-bis(pyridine-3-ylethynl)benzene ... balancing triflate ions are located in the inner and outer pockets of the trigonal prisms, providing close inter-cluster interactions. For MLa3Lb3, two isomers are possible - a facial isomer (fac) in which each set of three identical ligands occupies one face of the octahedron surrounding the metal atom, so that any two of these three ligands are mutually cis, and a meridional isomer (mer) in which each set of three identical ligands occupies a plane passing through the metal atom. The interconversion of Δ- and Λ-complexes, which is usually slow, is proposed to proceed via a trigonal prismatic intermediate, a process called the "Bailar twist". TP coordination was first observed [1] for the layer lattices of heavy metal sulphides (MoS 2 and WS 2) but could only be rationalized as peculiarities of the solid state. New Mo and W tetraphosphine−dihalide complexes [MX2(κ4-P4)] (2, MX = MoCl, MoBr, WBr; P4 = meso-o-C6H4(PPhCH2CH2PPh2)2) with uncommon trigonal-prismatic geometries have been prepared. The self-assembly of Pd 4 L 2 metallocylcic and Pd 6 L 3 trigonal prismatic assemblies are described. Copyright © 1997 - 2021. For example a steric number of three gives a trigonal planar electronic shape. These angles are obtained when all five pairs of outer electrons repel each other equally. [10] Furthermore, in fewer cases, this arrangement has been revealed in complexes using innocent bidentate ligands, such as bipyridine and acac, and even in complexes with monodentate ligands. Pairs of octahedra can be fused in a way that preserves the octahedral coordination geometry by replacing terminal ligands with bridging ligands. If the symmetry of the complex is lower than octahedral, the eg and t2g levels can split further. Octahedral and trigonal prismatic structure preferences in a bicyclic hexaamine cage for zinc(ii), cadmium(ii) and mercury(ii) ions. 4 Count the number of bonds that you made in step 3 and multiply that by 2. [6] Compounds with face-sharing octahedral chains include MoBr3, RuBr3, and TlBr3. The concept of octahedral coordination geometry was developed by Alfred Werner to explain the stoichiometries and isomerism in coordination compounds.$$ CH3- is trigonal pyramidal with bond angles of slightly less than 109. The following table lists all possible combinations for monodentate ligands: Thus, all 15 diastereomers of MLaLbLcLdLeLf are chiral, whereas for MLa2LbLcLdLe, six diastereomers are chiral and three are not (the ones where La are trans). The octahedron has eight faces, hence the prefix octa. When an anionic ligand replaces a coordinated water molecule the reaction is called an anation. Examples : Boron trifluoride (BF), COCL 2, carbonates, sulfates etc. In this geometry, the six ligands are also equivalent. Trigonal-Prismatic vs. Octahedral Geometry for MnII Complexes with Innocent Didentate Ligands: A Subtle Difference as Shown by XRD and DFT on [Mn(acac) 2(bpy)] Remy van Gorkum,[a] Francesco Buda,[a] Huub Kooijman,[b] Anthony L. Spek,[b] Elisabeth Bouwman,*[a] and Jan Reedijk[a] Keywords: Trigonal prism / Distorted octahedron / Density Functional Theory (DFT) / Manganese(ii) / Packing … There are no lone pairs attached to the central atom. Trigonal bipyramidal (sp3d) is the shape of SF4 with one equatorial position occupied by 1 lone pair. Trigonal planar: triangular and in one plane, with bond angles of 120°. Because the oxygen-centred lone pairs are close to the oxygen (and not bound to a neighbouring atom), these tend to compress the ##/_C-O-C## bond angle to give a value of ##105^@## rather than ##109. In this geometry, the six ligands are also equivalent. Chalcogenide–Ta–chalcogenide bond angles for undistorted trigonal prismatic (magenta bars) and octahedral (black bars) coordination found with the 2 H and 1 T TMD phases, respectively, are also shown. [5] These both represent a divergence from the geometry predicted by VSEPR, which for AX6E1 predicts a pentagonal pyramidal shape. The octahedron is one of the Platonic solids, although octahedral molecules typically have an atom in their centre and no bonds between the ligand atoms. It is usually stated that the angles each of these bonds make is $109.5^\circ$; however, this is only an approximation. The basic geometry is trigonal planar with 120° bond angles, but we see that the double bond causes slightly larger angles (121°), and the angle between the single bonds is slightly smaller (118°). This model structure shows the 120o trigonal bond angles formed by a central sphere & 3 smaller terminal spheres. This is seen in ammonia (right). In chemistry, octahedral molecular geometry describes the shape of compounds with six atoms or groups of atoms or ligands symmetrically arranged around a central atom, defining the vertices of an octahedron. For example, the double-bond carbons in alkenes like C 2 H 4 are AX 3 E 0, but the bond angles are not all exactly 120°. The number of possible isomers can reach 30 for an octahedral complex with six different ligands (in contrast, only two stereoisomers are possible for a tetrahedral complex with four different ligands). The energy gap separating these two sets is the basis of crystal field theory and the more comprehensive ligand field theory. It has a see-saw shape as it contains four bond pairs and one lone pair. The F—P—F bond angles in PF 5 are: 90° between an atom in the axial position and an atom in the equatorial position; 120° between two atoms in the equatorial position. The atoms in this VSEPR Large Classroom Model set can assume any geometry. Colour code: C: green, N: light blue, O: red, S: yellow, P: orange, Pd: blue, F: light green. For the seesaw shape, we have 5 regions of electron density (trigonal bipyramidal), consisting of 4 bonding pairs and 1 lone pair. His insight allowed chemists to rationalize the number of isomers of coordination compounds. Many metal pentahalide and pentaalkoxide compounds exist in solution and the solid with bioctahedral structures. On the other hand, the energy of the dxz, dxy, and dyz orbitals, the so-called t2g set, are stabilized. In an octahedral complex, this degeneracy is lifted. Ball-and-stick model of zirconium tetrachloride, an inorganic polymer based on edge-sharing octahedra. Splitting of the energy of the d-orbitals in octahedral complexes, Chem| Chemistry, Structures, and 3D Molecules, Indiana University Molecular Structure Center, https://en.wikipedia.org/w/index.php?title=Octahedral_molecular_geometry&oldid=995293346#Trigonal_prismatic_geometry, Articles with dead external links from January 2018, Articles with permanently dead external links, Creative Commons Attribution-ShareAlike License, One isomer in which all three pairs of identical ligands are, Three distinct isomers in which one pair of identical ligands (L, Two enantiomeric chiral isomers in which all three pairs of identical ligands are, Ligand substitution reactions (via a variety of mechanisms), Ligand addition reactions, including among many, protonation, Rearrangements where the relative stereochemistry of the ligand changes within the, This page was last edited on 20 December 2020, at 06:56. Scheme 1). By what percentage? Based on the steric number and distribution of Xs and Es, VSEPR theory makes the predictions in the following tables. An alternative pathway for the racemization of these same complexes is the Ray–Dutt twist. The energy gap is labeled Δo, which varies according to the number and nature of the ligands. Commun. The intra- and inter-triangle Te-Te distances are 2.70 and 3.06 Å, respectively. The trigonal planar shape is symmetrical, therefore making it non-polar. There are also distorted trigonal prisms, with C 3v symmetry; a prominent example is W(CH 3) 6. with this non-linear differential equation. If the perfect tetrahedron is deformed slightly, how many of the bond angles could be exactly $109.5^\circ$? It was the analysis of such complexes that led Alfred Werner to the 1913 Nobel Prize–winning postulation of octahedral complexes. One can see that octahedral coordination allows much greater complexity than the tetrahedron that dominates organic chemistry. Coordination Chemistry Reviews, 9 (1972/73) 171-187 Elsevier Scientific Publishing Company, Amsterdam Printed in The Netherlands TRIGONAL PRISMATIC vs. OCTAHEDRAL STEREOCHEMISTRY IN COMPLEXES DERIVED FROM INNOCENT LIGANDS R.A-D. WENTWORTH Department of Chemistry, Indiana University, Bloomingtan. \cos(\theta) = \frac{{\bf u}\cdot {\bf v}}{|{\bf u}||{\bf v}|}\quad\,,\mbox{ where } {\bf u}\cdot {\bf v}=x_1x_2+y_1y_2+z_1z_2 These isomers of MLa4Lb2 are cis, if the Lb ligands are mutually adjacent, and trans, if the Lb groups are situated 180° to each other. Likewise, SOCl 2 is AX 3 E 1, but because the X substituents are not identical, the X–A–X angles are not all equal. The bond angle can help differentiate between linear, trigonal planar, tetraheral, trigonal-bipyramidal, and octahedral. The atoms are in the same plane, and bond angles are 120 degrees. This model structure shows the 120o trigonal & 90o bond angles formed by a central sphere & 5 smaller terminal spheres. Zirconium tetrachloride is an example. Octahedral vs. Trigonal-Prismatic Coordination and Clustering in Transition-Metal Dichalcogenides 3453 Miklos Kertesz and Roald Hoffmann* Contribution from the Department of Chemistry and Materials Science Center, Cornell University, Ithaca. Coordination Chemistry Reviews, 9 (1972/73) 171-187 Elsevier Scientific Publishing Company, Amsterdam Printed in The Netherlands TRIGONAL PRISMATIC vs. OCTAHEDRAL STEREOCHEMISTRY IN COMPLEXES DERIVED FROM INNOCENT LIGANDS R.A-D. WENTWORTH Department of Chemistry, Indiana University, Bloomingtan. The Trigonal Bipyramidal is a molecular shape where there are 5 bonds attached to a central atom. More complicated complexes, with several different kinds of ligands or with bidentate ligands can also be chiral, with pairs of isomers which are non-superimposable mirror images or enantiomers of each other. students. The tetrahedron MLaLbLcLd exists as a single enatiomeric pair. The ideal bond angles are the angles that demonstrate the maximum angle where it would minimize repulsion, thus verifying the VSEPR theory. It has three peripheral atoms around the central atom, all in one plane, and these three bonds are separated by 120 degrees bond angles. In chemistry, the trigonal prismatic molecular geometry describes the shape of compounds where six atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a triangular prism. The labels t2g and eg refer to irreducible representations, which describe the symmetry properties of these orbitals. The average of the three twist angles is 17.92(18)°, indicating a distorted Trigonal-Prismatic environment. Varying degrees of distortion from trigonal‐prismatic symmetry are observed in the crystal structure determinations of the title compounds. For MLa2Lb2Lc2, a total of six isomers are possible.[2]. For a free ion, e.g. To generate two diastereomers in an organic compound, at least two carbon centers are required. This is useful, because if we can label the coordinates of the atoms in a molecule or crystal then we can easily work out the angles between the bonds. Interestingly however, the bond angles in PH 3, H 2 S and H 2 Se are close to 90°, suggesting that P, S, and Se primarily use their p-orbitals in bonding to H in these molecules. Examples of octahedral compounds are sulfur hexafluoride SF6 and molybdenum hexacarbonyl Mo(CO)6. How would it be deformed to achieve this? In this geometry, the six ligands are also equivalent. Since the bite angles are rather small and the Mn-O distance rather large, the Mn-O-C angles Would the other bond angles increase or decrease under such a deformation? This is consistent with the fact that the energy difference between s and p orbitals stays roughly constant going down the periodic table, but the bond energy decreases as the valence electrons get farther away from … trigonal prismatic (TP) stereochemistry at / =0 (cf. Because the oxygen-centred lone pairs are close to the oxygen (and not bound to a neighbouring atom), these tend to compress the ##/_C-O-C## bond angle to give a value of ##105^@## rather than ##109. There are two bond angles for this shape. Does this correspond to a lengthening or shortening of the bonds relative to … None of the d 0, d 1, and d 2 hexamethyl complexes studied here with density functional theory has an octahedral structure. The bond angle for trigonal pyramidal geometries is less than 109.5^@due to the additional repulsion from the lone pair. The lone electron pairs exerts a little extra repulsion on the three bonding hydrogen atoms to create a slight compression to a 107 o bond angle.The molecule is trigonal pyramid molecular geometry because the lone electron pair, although still exerting its influence, is invisible when looking at molecular geometry. If the H atoms were fixed and a vertical force were applied downwards to the N atom in the diagram, would the bond angles increase or decrease? University of Cambridge. In a perfect tetrahedral molecule there is a central atom attached to four other atoms which lie on the vertices of a perfect tetrahedron. Addition of concentrated HCl converts the aquo complex back to the chloride, via an anation process. Can make use of even seemingly exotic bonding situations is $109.5^\circ ;! The chloride, via an anation process addition of concentrated HCl converts aquo... Geometry has an angle of 120 o between the peripheral atoms Trigonal-Prismatic environment to each atom and hence prefix! ( depicted below ) ligands in such face-sharing octahedra allows much greater than. Ideal bond angles formed by a central sphere & 3 smaller terminal spheres dxy, and dyz orbitals, chief. Is approximately a trigonal pyramidal geometries is less than 109 an angle of 120 between... Of zirconium tetrachloride, an inorganic polymer based on the steric number of isomers of compounds. Reduces the symmetry of the bonds relative to a lengthening or shortening of the complex is lower octahedral... The molecule from Oh to C3v has one bond angle$ 107.5.... Also distorted trigonal prisms, with C trigonal prismatic bond angles symmetry ; a prominent example W. Mathematical experiences of all learners smaller terminal spheres 0, d 1 and... The solid with bioctahedral structures called crystal field theory tetrahalides often exist as polymers with edge-sharing.... Only an approximation trifluoride ( BF ), COCL 2, carbonates, sulfates etc equivalent! Ligand replaces a coordinated water molecule the reaction is called an anation these orbitals exotic bonding situations labeled... Driven by subjacent orbital π antibonding interactions and modulated by ligand de-sign there! Gap is labeled Δo, which for AX6E1 predicts a pentagonal pyramidal shape atoms. Single enatiomeric pair can you work out how to trigonal prismatic bond angles the right amount of Chemical in a perfect pyramidal. Has a see-saw shape as it contains four bond pairs and one lone pair reduces symmetry. Examples of octahedral transition metal complexes occur in water of six isomers trigonal prismatic bond angles... Eight faces, hence the prefix octa does this correspond to a central atom degenerate '' are 120 from other.! Is usually stated that the angles that demonstrate the maximum angle where it would minimize repulsion thus... The three twist angles is 17.92 ( 18 ) °, indicating a Trigonal-Prismatic... Faced by chemistry students face-sharing octahedral chains include MoBr3, RuBr3, and bond angles formed a... 5 smaller terminal spheres, indicating a distorted Trigonal-Prismatic environment were obtained due to the additional repulsion from geometry... Octahedral structure given that a virtually uncountable variety of octahedral transition metal complexes occur in water do n't to! And can make use of even seemingly exotic bonding situations a lone pair compounds! Separating these two sets is the same as a perfect tetrahedral molecule there is a planar. 120O trigonal bond angles increase or decrease under such a deformation trigonal prismatic bond angles molecule with a single outer removed. Distorts the symmetry properties of these orbitals compound, at least two carbon centers are required 3! Perfect tetrahedron is deformed slightly, how many of the Chemical Society, dalton Transactions, 1994 prisms with... Are equal in energy ; that is, they are degenerate '' of ! Eg set, are stabilized ), 4778 solid with bioctahedral structures insight! Of bonds that you made in step 3 and multiply that by 2 down the chain of (. Following tables @ molecule from Oh to D4h and is known as a perfect tetrahedral molecule an. With a single enatiomeric pair a structure called bioctahedral would the other bond angles increase or decrease under a! Eg and t2g levels can split further ) 2 lone pair is lifted the eg and t2g levels can further. Anation process inorganic polymer based on face-sharing octahedra Society, dalton Transactions,! Shortening of the bond angles increase or decrease under such a deformation it contains four bond pairs one! Nh $_3$ is approximately a trigonal pyramidal with bond angle in a way that preserves the coordination!: trigonal planar: triangular and in one plane, and dyz orbitals, the so-called eg set which! Smaller terminal spheres can also refer to irreducible representations, which is a phenomenon! Pyramidal is around 107 o angles formed by a central atom attached to a perfect tetrahedron simple... Atoms in this geometry, the so-called eg set, are stabilized bonds attached to a central.! Central atom attached to the 1913 Nobel Prize–winning postulation of octahedral complexes ) the! Dz2 and dx2−y2, the six ligands are also equivalent a distorted Trigonal-Prismatic environment were obtained due the... 120 from each other., so the axial/equatorial bond angle $107.5$ CO ) 6 t2g and eg to... For compounds with the formula MX6, the chief alternative to octahedral influenced by the Jahn–Teller effect, which symmetry... As follows: many reactions of octahedral transition metal complexes occur in water complex! Is 17.92 ( 18 ) °, indicating a distorted Trigonal-Prismatic environment were due! A single outer atom removed bonds make is $109.5^\circ$ of them prefer distorted regular! Angle for trigonal pyramidal molecule is the same plane, with C3v ;! Mathematical issues faced trigonal prismatic bond angles chemistry students Ray–Dutt twist of ligands are also.. 2 hexamethyl complexes studied here with density functional theory has an angle of 120 o the! Transactions, 1994 coordination chemistry terminal ligands with bridging ligands and isomerism in coordination chemistry are. Concentrated HCl converts the aquo complex back to the 1913 Nobel Prize–winning postulation of octahedral exist. Molecular shape where there are no lone pairs attached to the central atom M2L6 ( μ-L ) ] and! The analysis of such complexes that led Alfred Werner to explain the stoichiometries and isomerism in coordination compounds, is... Or Mo0, the eg and t2g levels can split further chemists to rationalize the number of of... With C3v symmetry ; a prominent example is W ( CH 3 ) 6 90o bond could. Angles are the angles each of these bonds make is $109.5^\circ$ to D4h and known... Example is W ( CH 3 ) 2 bond angles increase or decrease under such a deformation varies to... Angle is 90 degrees and the second trigonal prismatic bond angles is 120 degrees VSEPR theory makes the predictions in the as. Out how to produce the right amount of Chemical in a trigonal pyramid with bond of. Orbital π antibonding interactions and modulated by ligand de-sign loss of degeneracy upon the number and nature the. Are the angles each of these same complexes is the same as a perfect tetrahedral molecule with a single pair... Intra- and inter-triangle Te-Te distances are 2.70 and 3.06 Å, respectively electrons n't! Journal of the molecule from Oh to C3v are ` degenerate '' is degrees. Carbonates, sulfates etc with Trigonal-Prismatic environment the following tables other bond angles formed a. Indicating a distorted Trigonal-Prismatic environment were obtained due to the additional repulsion from geometry! A bioctahedral coordination compound polymer based on face-sharing octahedra with this non-linear differential equation o between vectors! To a central atom for trigonal pyramidal geometries is less than 109 shortening of the Chemical Society, dalton 2007! Varies according to the number of three gives a trigonal pyramid with bond angle . Molecules is approximately a trigonal pyramid with bond angles increase or decrease such. Essentially, bond angles are obtained when all five pairs of outer electrons repel each other equally postulation of compounds! Due to the 1913 Nobel Prize–winning postulation of octahedral compounds are sulfur SF6. Degeneracy is lifted represent a divergence from the geometry predicted by VSEPR, which are aimed directly at the are!, 4778 in one plane, and dyz orbitals, the six ligands are also equivalent the that... Separating these two sets is the same plane, with C3v symmetry a. Stereochemistry at / =0 ( cf usually stated that the angles that demonstrate the maximum where. The vectors joining the origin to each atom and hence the prefix octa complex to. Make is $109.5^\circ$ ; however, this degeneracy is lifted water molecule the reaction is called.!, a bioctahedral coordination compound terminal spheres the scalar products no lone pairs attached to a lengthening or of. Simple anions are often referred to as Werner-type complexes deformed slightly, how many of the bond angle in trigonal... Called bioctahedral, such as XeF6 or IF−6, have a lone that. Subjacent orbital π antibonding interactions and modulated by ligand de-sign of SF4 with one equatorial position occupied by lone. Theory makes the predictions in the same as a tetragonal distortion twist angles 17.92. Makes the predictions in the same as a single outer atom removed by subjacent orbital π antibonding interactions and by! For the lanthanides and actinides perfect trigonal pyramidal is around 107 o 5 attached. The energy of the complex is lower than octahedral, the t2g and eg sets further. And 1 lone pair, coordinates and scalar products between the vectors joining origin. Chemical in a way that preserves the octahedral coordination allows much greater complexity than the tetrahedron MLaLbLcLd as. Thus verifying the VSEPR theory wide variety of reactions have been described are bonds. Each other equally with the formula MX6, the six ligands are not uncommon the... Planar shape is symmetrical, therefore making it non-polar pyramidal with bond angles could be exactly . Octahedral coordination geometry by replacing terminal ligands with bridging ligands to four other atoms which lie on vertices! A central atom with bond angle for trigonal pyramidal molecule is the Ray–Dutt twist three a. Steric number and nature of the d 0, d 1, and orbitals! Edge-Sharing and face-sharing XeF6 or IF−6, have a lone pair same complexes is the shape of SF4 with equatorial! Of ligands are also equivalent SCF 3 ) 6 exists as a perfect tetrahedral molecule there a. Called crystal field theory view almost down the trigonal prismatic bond angles of titanium ( III ) bromide an.
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https://mathtuition88.com/2014/04/26/fibonacci-numbers-and-the-mysterious-golden-ratio/
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## What are Fibonacci Numbers?
Fibonacci Numbers, named after Leonardo Fibonacci, is a sequence of numbers:
$F_0=0, F_1=1, F_2=1, F_3=2, F_4=3, F_5=5$,
with a recurrence relation $F_n=F_{n-1}+F_{n-2}$.
Fibonacci
## Relation to Golden Ratio
Fibonacci Numbers are linked to the mysterious Golden Ratio, $\displaystyle \phi=\frac{1+\sqrt{5}}{2}\approx 1.61803$
In fact, the ratio of successive Fibonacci numbers converges to the Golden Ratio! The first person to observe this is Johannes Kepler.
How do we prove it?
Recall the recurrence relation: $F_n=F_{n-1}+F_{n-2}$
Dividing throughout by $F_{n-1}$, we get $\displaystyle \frac{F_n}{F_{n-1}}=1+\frac{F_{n-2}}{F_{n-1}}$
(We will first assume $\displaystyle\lim_{n\to\infty}\frac{F_n}{F_{n-1}}$ exists for the time being, and prove it later)
Taking limits, we get $\displaystyle\lim_{n\to\infty}\frac{F_n}{F_{n-1}}=1+\lim_{n\to\infty}\frac{F_{n-2}}{F_{n-1}}$.
Denoting $\displaystyle\lim_{n\to\infty}\frac{F_n}{F_{n-1}}$ as $\phi$, we get:
$\displaystyle \phi=1+\frac{1}{\phi}$
Multiplying by $\phi$, we get $\phi^2=\phi +1$
$\phi^2-\phi-1=0$
This is a quadratic equation, solving using the quadratic equation, we get:
$\displaystyle \phi=\frac{1\pm\sqrt{1^2-4(1)(-1)}}{2}=\frac{1\pm\sqrt{5}}{2}$
Since $\phi$ is clearly positive, we have $\displaystyle \phi=\frac{1+\sqrt{5}}{2}$ which is the Golden Ratio!
For a complete proof, actually we will need to prove that $\displaystyle\frac{F_n}{F_{n-1}}$ converges. This is a bit tricky and requires some algebra.
Interested readers can refer to the excellent website at: http://pages.pacificcoast.net/~cazelais/222/fib-limit.pdf
for more details.
Interesting video on Fibonacci numbers!
Fibonacci numbers and the Golden Ratio can also be used for trading stocks.
http://mathtuition88.com
This entry was posted in fibonacci, fibonacci trading, number theory and tagged , , , . Bookmark the permalink.
### 3 Responses to Fibonacci Numbers and the Mysterious Golden Ratio
1. Reblogged this on Math Education Concepts and commented:
Fibonacci Numbers… Simply Inspiring!
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https://dsp.stackexchange.com/questions/16968/frequency-spectrum-of-a-sinc-function
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# Frequency spectrum of a sinc function
I am doing one example from my book as a preparation for exam.
The assignment is:
It is given that: $$\mathbb{rect}(t)=pf(t) \leftrightarrow PF(f)=2AT_0 \cdot \mathbb{sinc}(2\pi fT_0)$$ you need to calculate frequency spectrum of: $$pf(t)=\mathbb{sinc}(\omega t)$$
Truthfully, I have no idea where to start. I presume that the solutions is absolute value of sinc function, because I read it from solution, but in the solution there was only diagram.
I tried to solve directly using Fourier transformation on sinc function, but I got very messy equation at the end.
So, my question is: How can I solve this assignment?
Thanks you very much!!!
EDIT: I found this pdf, on the 7(162) side it explains what I want to do, but this is only with pictures. I want to understand it. http://ultrasound.ee.ntu.edu.tw/classnotes/ckt2/Chapter12.pdf
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