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Darken’s equations can be applied to almost any scenario involving the diffusion of two different components that have different diffusion coefficients. This holds true except in situations where there is an accompanying volume change in the material because this violates one of Darken’s critical assumptions that atomic volume is constant. More complicated equations than presented must be used in cases where there is convection. One application in which Darken’s equations play an instrumental role is in analyzing the process of diffusion bonding. Diffusion bonding is used widely in manufacturing to connect two materials without using adhesives or welding techniques. Diffusion bonding works because atoms from both materials diffuse into the other material, resulting in a bond that is formed between the two materials. The diffusion of atoms between the two materials is achieved by placing the materials in contact with each other at high pressure and temperature, while not exceeding the melting temperature of either material. Darken’s equations, particularly Darken’s second equation, come into play when determining the diffusion coefficients for the two materials in the diffusion couple. Knowing the diffusion coefficients is necessary for predicting the flux of atoms between the two materials, which can then be used in numerical models of the diffusion bonding process, as, for example, was looked at in the paper by Orhan, Aksoy, and Eroglu when creating a model to determine the amount of time required to create a diffusion bond. In a similar manner, Darken’s equations were used in a paper by Watanabe et al., on the nickel-aluminum system, to verify the interdiffusion coefficients that were calculated for nickel aluminum alloys.
Application of Darken’s first equation has important implications for analyzing the structural integrity of materials. Darken’s first equation, , can be rewritten in terms of vacancy flux, . Use of Darken’s equation in this form has important implications for determining the flux of vacancies into a material undergoing diffusion bonding, which, due to the Kirkendall effect, could lead to porosity in the material and have an adverse effect on its strength. This is particularly important in materials such as aluminum nickel superalloys that are used in jet engines, where the structural integrity of the materials is extremely important. Porosity formation, known as Kirkendall porosity, in these nickel-aluminum superalloys have been observed when diffusion bonding has been used. It is important then to use Darken’s findings to predict this porosity formation. | 0 | Theoretical and Fundamental Chemistry |
The hydroamination reaction is approximately thermochemically neutral. The reaction however suffers from a high activation barrier, perhaps owing to the repulsion of the electron-rich substrate and the amine nucleophile. The intermolecular reaction also is accompanied by highly negative changing entropy, making it unfavorable at higher temperatures.
Consequently, catalysts are necessary for this reaction to proceed. As usual in chemistry, intramolecular processes occur at faster rates than intermolecular versions. | 0 | Theoretical and Fundamental Chemistry |
Polysulfides are compounds that have chains of sulfur atoms. This reactant has been tested on the field in treating TCE and in comparison to EHC. The use of polysulfides is a type of abiotic reduction and works best in anaerobic conditions where iron (III) is available. The benefit of using polysulfides is that they do not produce any biological waste products; however, the reaction rates are slow and they require more time to create the DVI (dual valent iron) minerals that are needed for the reduction to occur. | 1 | Applied and Interdisciplinary Chemistry |
Poolman pursued studies in Biochemistry and Microbiology at the University of Groningen, the Netherlands, and the University of Bern (Switzerland), obtaining a MSc degree in 1984. He gained his PhD in 1987 with a thesis on bioenergetics of streptococci, under the supervision of Wil Konings and Hans Veldkamp.
After a brief stint as a scientist at Genencor Inc (now Dupont Industrial Biosciences) in San Francisco (USA), he returned to the Netherlands in the end of 1989 to start his own research group on biochemistry and molecular biology of membrane transport at the University of Groningen, supported by a fellowship from the Royal Netherlands Academy of Arts and Sciences. He has been professor of biochemistry at the Groningen since 1998. In 2008 he was appointed Program Director of its Centre for Synthetic Biolog), and in 2013 he became Scientific Director of its Biomolecular Sciences and Biotechnology Institute.
In 1993 Poolman has done a sabbatical at Transgene SA, Strasbourg (France). Thanks to a Fulbright fellowship, he was visiting professor in biochemistry at California Institute of Technology, Pasadena (USA) in 2003.
Poolman has been Chair of the KNAW Earth and Life Sciences Board, and has been vice-chair of KNAW Council for Natural and Technical Sciences since 2017.
From 2016 to 2018, he was a member of the Dutch Council for Physics and Chemistry, and currently he is a member of the core team of the Council for Chemistry.
Since 2009 he led the focus area on ‘Biomolecular and Bioinspired Functionality’ at the Zernike Institute for Advanced Materials (University of Groningen, together with Nobel laureate Ben Feringa, and, from 2010 to 2017, he managed a national Synthetic Biology program of the University of Groningen. | 0 | Theoretical and Fundamental Chemistry |
Smelting has serious effects on the environment, producing wastewater and slag and releasing such toxic metals as copper, silver, iron, cobalt, and selenium into the atmosphere. Smelters also release gaseous sulfur dioxide, contributing to acid rain, which acidifies soil and water.
The smelter in Flin Flon, Canada was one of the largest point sources of mercury in North America in the 20th century. Even after smelter releases were drastically reduced, landscape re-emission continued to be a major regional source of mercury. Lakes will likely receive mercury contamination from the smelter for decades, from both re-emissions returning as rainwater and leaching of metals from the soil. | 1 | Applied and Interdisciplinary Chemistry |
In 1954, there was a program started at New York University called the Division of Research. It was a small program that included personnel from the Institute of Mathematical Sciences at New York University. | 0 | Theoretical and Fundamental Chemistry |
A polycatenane is a chemical substance that, like polymers, is chemically constituted by a large number of units. These units are made up of concatenated rings into a chain-like structure.
It consists of mechanically linked catenane structures, via topological Hopf links, resulting in a higher dimensionality than the repeating unit. They are a class of catenanes where the number of macrocycles is greater than two and as catenanes they belong to the big family of mechanically interlocked molecular architectures (MIMAs).
The characteristic feature of a polycatenane compound, that distinguishes it from other polymers, is the presence of mechanical bonds in addition to covalent bonds. The rings in this chain-like structure can be separated only when high energy is provided to break at least a covalent bond of the macrocycle. [n]-Catenanes (for large n), which consist solely of the mechanically interlocked cyclic components, can be viewed as “optimized” polycatenanes. The main difference between poly-[2]-catenanes and poly-[n]-catenanes is the repeating unit, as a monomer is for the polymer. In the first case the monomer is made of two interlocked rings that repeat continuously in the final polycatenane, while in the latter case there is only one ring that repeat the interlocking process for a large number of times. If the rings of the polycatenane are all of the same type, it can be defined as a homocatenane while if the subunits are different it is defined as heterocatenane.
As a chain, the degree of motion of these structures is very high, greater than the one of a usual polymer, because the rings possess a reciprocal rotational, elongational and rocking motion. This flexibility is retained even if the macrocycles themselves are very rigid units, because the mobility is given by the ability of the rings to move with respect to each other. This mobility influences the final properties of the material (mechanical, rheological and thermal), and provides a dynamic behavior. | 0 | Theoretical and Fundamental Chemistry |
Chandrasekhar–Friedman–Schutz instability or shortly CFS instability refers to an instability that can occur in rapidly rotating stars with which the instability arises for cases where the gravitational radiation reaction is unable to cope with the change in angular momentum associated with the perturbations. The instability was discovered by Subrahmanyan Chandrasekhar in 1970 and later a simple intuitive explanation for the instability was provided by John L. Friedman and Bernard F. Schutz. Specifically, the instability arises when a non-axisymmetric perturbation mode that appears co-rotating in the inertial frame (from which gravitational waves are observed), is in fact is counter-rotating with respect to the rotating star. | 1 | Applied and Interdisciplinary Chemistry |
Burks-Houck began her professional career in 1983 working as an environmental chemist at the Lawrence Livermore National Laboratory on environmental protection projects with an interest in ensuring worker safety. | 0 | Theoretical and Fundamental Chemistry |
In chemical thermodynamics, activity (symbol ) is a measure of the "effective concentration" of a species in a mixture, in the sense that the species' chemical potential depends on the activity of a real solution in the same way that it would depend on concentration for an ideal solution. The term "activity" in this sense was coined by the American chemist Gilbert N. Lewis in 1907.
By convention, activity is treated as a dimensionless quantity, although its value depends on customary choices of standard state for the species. Activity depends on temperature, pressure and composition of the mixture, among other things. For gases, the activity is the effective partial pressure, and is usually referred to as fugacity.
The difference between activity and other measures of concentration arises because the interactions between different types of molecules in non-ideal gases or solutions are different from interactions between the same types of molecules. The activity of an ion is particularly influenced by its surroundings.
Equilibrium constants should be defined by activities but, in practice, are often defined by concentrations instead. The same is often true of equations for reaction rates. However, there are circumstances where the activity and the concentration are significantly different and, as such, it is not valid to approximate with concentrations where activities are required. Two examples serve to illustrate this point:
*In a solution of potassium hydrogen iodate KH(IO) at 0.02 M the activity is 40% lower than the calculated hydrogen ion concentration, resulting in a much higher pH than expected.
*When a 0.1 M hydrochloric acid solution containing methyl green indicator is added to a 5 M solution of magnesium chloride, the color of the indicator changes from green to yellow—indicating increasing acidity—when in fact the acid has been diluted. Although at low ionic strength (< 0.1 M) the activity coefficient approaches unity, this coefficient can actually increase with ionic strength in a high ionic strength regime. For hydrochloric acid solutions, the minimum is around 0.4 M. | 0 | Theoretical and Fundamental Chemistry |
Optical particle measurements are emerging as an important technique for understanding the ocean carbon cycle, including contributions to estimates of their downward flux, which sequesters carbon dioxide in the deep sea. Optical instruments can be used from ships or installed on autonomous platforms, delivering much greater spatial and temporal coverage of particles in the mesopelagic zone of the ocean than traditional techniques, such as sediment traps. Technologies to image particles have advanced greatly over the last two decades, but the quantitative translation of these immense datasets into biogeochemical properties remains a challenge. In particular, advances are needed to enable the optimal translation of imaged objects into carbon content and sinking velocities. In addition, different devices often measure different optical properties, leading to difficulties in comparing results. | 0 | Theoretical and Fundamental Chemistry |
Knockdown of Alms1 by short interfering RNA in mouse inner medullary collecting duct cells caused defective ciliogenesis. Cilia were stunted and treated cells lacked the ability to increase calcium influx in response to mechanical stimuli. | 1 | Applied and Interdisciplinary Chemistry |
Many authors define dynamic pressure only for incompressible flows. (For compressible flows, these authors use the concept of impact pressure.) However, the definition of dynamic pressure can be extended to include compressible flows.
For compressible flow the isentropic relations can be used (also valid for incompressible flow):
Where: | 1 | Applied and Interdisciplinary Chemistry |
In 2000, with the help of plant breeders and the Organic Research Centre, the scientist Martin Wolfe crossed 20 varieties of wheat (selected for quality and yield) and crossed them to obtain 190 new crosses. These seeds were not further selected and planted, grown, harvested and reseeded together as a population.
Martin Wolfe called it YQ, for "yield" and "quality". Wolfe lobbied in Brussels and Westminster to receive an exception to the EU regulations that would allow YQ to be sold. In 2014, it was accepted and since 2017 the YQ seed, officially called the "ORC Wakelyns Population" was the first population wheat to go on sale in Europe. | 1 | Applied and Interdisciplinary Chemistry |
Induction heating is a non contact heating process which uses the principle of electromagnetism induction to produce heat in a work-piece. In this case thermal expansion is used in a mechanical application to fit parts over one another, e.g. a bushing can be fitted over a shaft by making its inner diameter slightly smaller than the diameter of the shaft, then heating it until it fits over the shaft, and allowing it to cool after it has been pushed over the shaft, thus achieving a shrink fit. By placing a conductive material into a strong alternating magnetic field, electric current can be made to flow in the metal thereby creating heat due to the IR losses in the material. The current generated flows predominantly in the surface layer. The depth of this layer being dictated by the frequency of the alternating field and the permeability of the material. Induction heaters for shrink fitting fall into two broad categories:
* Mains frequency (MF) units using magnetic cores (iron)
* Solid state MF and radio frequency (RF) heaters | 1 | Applied and Interdisciplinary Chemistry |
Spacecraft waste heat is ultimately rejected to space by radiator surfaces. Radiators can be of different forms, such as spacecraft structural panels, flat-plate radiators mounted to the side of the spacecraft, panels deployed after the spacecraft is on orbit, and droplets.
All radiators reject heat by infrared (IR) radiation from their surfaces. The radiating power depends on the surface's emittance and temperature.
The radiator must reject both the spacecraft waste heat plus any radiant-heat loads from the environment or other spacecraft surfaces.
Most radiators are therefore given surface finishes with high IR emittance ( > 0.8) to maximize heat rejection and low solar absorption ( < 0.2) to limit heat loads from the sun.
High-temperature radiators are preferred for better efficiency and size reduction considerations, however, fluid property and droplet cloud property are additional factors.
Droplet size formation and droplet density govern emission and reabsorption.
A smaller droplet is essential for obtaining effective radiation in the liquid droplet radiator. A droplet with a diameter of 1 μm has been calculated to cool from 500 K to 252 K in two seconds. A dense cloud of the droplet sheet will retard the cooling rate of the droplets because of the reabsorption of the emitted light.
A single droplet radiates heat as it travels through space and at any time this heat loss is given by:
where is the Stefan–Boltzmann constant,
is the droplet heat loss rate to space (joules/second),
is the droplet radius (meters),
is the average gray body view factor for droplet at stream center (less than one), and
is the absolute droplet temperature at any time (kelvin).
This equation models the droplet as a gray body with
constant average emissivity. The instantaneous radiation
rate is equal to the rate of energy loss resulting in this
equation:
where is the specific heat capacity,
is the density of droplet (kg/m),
is the droplet transit time (seconds). | 0 | Theoretical and Fundamental Chemistry |
The microbubbles used today are composed of a gas core and a surrounding shell. The makeup of these elements may vary depending on the preferred physical and chemical properties. Microbubble shells have been formed with lipids, galactose, albumin, or polymers. The gas core can be made up of air or heavy gases like nitrogen or perfluorocarbon. | 1 | Applied and Interdisciplinary Chemistry |
Thermal radiation is an important factor of many engineering applications, especially for those dealing with high temperatures. | 0 | Theoretical and Fundamental Chemistry |
Vilma Espín was an outspoken supporter of gender equality in Cuba, but distinctly separated herself and the goals of the Federation of Cuban Women from traditional feminism, insisting advocacy for feminine not feminist. Her involvement in the revolution helped transform the role of women in Cuba and in 1960, Espín became the president of the Federation of Cuban Women, and remained in that position until her death in 2007. The organization's primary goals were educating women, giving them the necessary skills to seek gainful employment, and above all encouraging them to participate in politics and support the revolutionary government. In 1960, when sugar mills and cane fields were under attack across Cuba shortly before the Bay of Pigs invasion, the Federation of Cuban Women created the Emergency Medical Response Brigades to mobilize women against counter-revolution. The Cuban government and the Federation encouraged women to join the labor force, even going so far as to pass the Cuban Family Code in 1975, a law mandating that men must help with household chores and childcare to lighten the workload for working mothers. | 1 | Applied and Interdisciplinary Chemistry |
NBS electrophilically brominates the amine, which is followed by decarboxylation and release of an imine. Further hydrolysis will yield an aldehyde and ammonia. (cf. non-oxidative PLP dependent decarboxylation) | 0 | Theoretical and Fundamental Chemistry |
The global cooling potential of various areas around the world varies primarily based on climate zones and the presence of weather patterns and events. Dry and hot regions generally have a higher radiative cooling power (estimated up to 120 W/m2), while colder regions or those with high humidity or cloud cover generally have lower global cooling potentials. The cooling potential of various regions can also change from winter to summer due to shifts in humidity and cloud cover. Studies mapping the daytime radiative cooling potential have been done for China and India, the United States, and on a continental scale across Europe. | 0 | Theoretical and Fundamental Chemistry |
One of the most well discussed, and detrimental, embrittlement is hydrogen embrittlement in metals. There are multiple ways that hydrogen atoms can diffuse into metals, including from environment or during processing (eg. electroplating). The exact mechanism that causes hydrogen embrittlement is still not determined, but many theories are proposed and are still undergoing verification. Hydrogen atoms are likely to diffuse to grain boundaries of metals, which becomes a barrier for dislocation motion and builds up stress near the atoms. When the metal is stressed, the stress is concentrated near the grain boundaries due to hydrogen atoms, allowing a crack to nucleate and propagate along the grain boundaries to relieve the built-up stress.
There are many ways to prevent or reduce the impact of hydrogen embrittlement in metals. One of the more conventional ways is to place coatings around the metal, which will act as diffusion barriers that prevents hydrogen from being introduced from the environment into the material. Another way is to add traps or absorbers in the alloy which takes into the hydrogen atom and forms another compound. | 1 | Applied and Interdisciplinary Chemistry |
Phase separation transfers impurities into a non-aqueous phase. Phase separation may occur at intermediate points in a treatment sequence to remove solids generated during oxidation or polishing. Grease and oil may be recovered for fuel or saponification. Solids often require dewatering of sludge in a wastewater treatment plant. Disposal options for dried solids vary with the type and concentration of impurities removed from water. | 1 | Applied and Interdisciplinary Chemistry |
Project GABRIEL was an investigation to gauge the impact of nuclear fallout resulting from nuclear warfare. The United States Atomic Energy Commission surmised that the radioactive isotope strontium-90 (Sr-90) presented the greatest hazard to life globally, which resulted in the commissioning of Project SUNSHINE: which sought to examine the levels of Sr-90 in human tissues and bones (with a special interest in infants) gathered from around the world. | 0 | Theoretical and Fundamental Chemistry |
Lithium is structurally similar to other cations such as sodium, potassium, magnesium and calcium, this causes lithium to activate potassium channels which inhibit neuromuscular transmission. Patients who take lithium can have a prolonged response to both depolarising and nondepolarising NMBAs. | 1 | Applied and Interdisciplinary Chemistry |
Embryo transfer techniques allow top quality female livestock to have a greater influence on the genetic advancement of a herd or flock in much the same way that artificial insemination has allowed greater use of superior sires. ET also allows the continued use of animals such as competition mares to continue training and showing, while producing foals. The general epidemiological aspects of embryo transfer indicates that the transfer of embryos provides the opportunity to introduce genetic material into populations of livestock while greatly reducing the risk for transmission of infectious diseases. Recent developments in the sexing of embryos before transfer and implanting has great potential in the dairy and other livestock industries.
Embryo transfer is also used in laboratory mice. For example, embryos of genetically modified strains that are difficult to breed or expensive to maintain may be stored frozen, and only thawed and implanted into a pseudopregnant dam when needed.
On February 19, 2020, the first pair of Cheetah cubs to be conceived through embryo transfer from a surrogate cheetah mother was born at Columbus Zoo in Ohio. | 1 | Applied and Interdisciplinary Chemistry |
In 1970 Iphigenia Vourvidou-Photaki was awarded the one-off Georgios Panopoulos Prize of the Academy of Athens, presented to her for "...her research on the chemical synthesis of polypeptide hormones and investigation of enzyme active sites, which constitute an internationally notable contribution of Greek science to the modern discipline of Chemistry".
During her lifetime, she was invited many times as a distinguished researcher in academic conferences related to her subject; some examples were the personal invitations she received to the 3rd European Peptide Symposium (EPS) (Basel, 1960), the 5th EPS (Oxford, 1962), 6th EPS (Athens, 1963 as organiser), 6th International Biochemistry Conference (New York, 1964), 7th EPS (Budapest, 1964), Symposium on Natural Sulfur Compounds (Copenhagen, 1966), NATO Seminar of Molecular Biology (Spetses, 1966), 8th EPS (Noordwijk, 1966), 9th EPS (Paris, 1968), 10th EPS (Abano, 1970), 11th EPS (Vienna, 1971), 3rd American Peptide Symposium (APS) (Boston, 1972), 13th EPS (Kiryat, 1974), 4th APS (New York, 1975), and the 14th EPS (Wépion, 1976) over which she presided. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the term "reagent" denotes a chemical ingredient (a compound or mixture, typically of inorganic or small organic molecules) introduced to cause the desired transformation of an organic substance. Examples include the Collins reagent, Fenton's reagent, and Grignard reagents. | 0 | Theoretical and Fundamental Chemistry |
In the Ca-looping process, a CaO-based sorbent, typically derived from limestone, reacts via the reversible reaction described in Equation () and is repeatedly cycled between two vessels.
The forward, endothermic step is called calcination while the backward, exothermic step is carbonation.
A typical Ca-looping process for post-combustion CO capture is shown in Figure 1, followed by a more detailed description.
Flue gas containing CO is fed to the first vessel (the carbonator), where carbonation occurs. The CaCO formed is passed to another vessel (the calciner). Calcination occurs at this stage, and the regenerated CaO is quickly passed back to the carbonator, leaving a pure CO stream behind. As this cycle continues, CaO sorbent is constantly replaced by fresh (reactive) sorbent. The highly concentrated CO from the calciner is suitable for sequestration, and the spent CaO has potential uses elsewhere, most notably in the cement industry. The heat necessary for calcination can be provided by oxy-combustion of coal below.
Oxy-combustion of coal: Pure oxygen rather than air is used for combustion, eliminating the large amount of nitrogen in the flue-gas stream. After particulate matter is removed, flue gas consists only of water vapor and CO, plus smaller amounts of other pollutants. After compression of the flue gas to remove water vapor and additional removal of air pollutants, a nearly pure CO stream suitable for storage is produced.
The carbonator's operating temperature of 650-700 °C is chosen as a compromise between higher equilibrium (maximum) capture at lower temperatures due to the exothermic nature of the carbonation step, and a decreased reaction rate. Similarly, the temperature of >850 °C in the calcinator strikes a balance between increased rate of calcination at higher temperatures and reduced rate of degradation of CaO sorbent at lower temperatures. | 1 | Applied and Interdisciplinary Chemistry |
Green rust is a generic name for various green crystalline chemical compounds containing iron(II) and iron(III) cations, the hydroxide () anion, and another anion such as carbonate (), chloride (), or sulfate (), in a layered double hydroxide structure. The most studied varieties are
* carbonate green rust – GR(): [()] · [·2].
* chloride green rust – GR(): [()] · [·n].
* sulfate green rust – GR(): [()] · [·2].
Other varieties reported in the literature are bromide , fluoride , iodide , nitrate , and selenate.
Green rust was first recognized as a corrosion crust on iron and steel surfaces. It occurs in nature as the mineral fougerite. | 1 | Applied and Interdisciplinary Chemistry |
Because these alloys are intended for high temperature applications their creep and oxidation resistance are of primary importance. Nickel (Ni)-based superalloys are the material of choice for these applications because of their unique γ' precipitates. The properties of these superalloys can be tailored to a certain extent through the addition of various other elements, common or exotic, including not only metals, but also metalloids and nonmetals; chromium, iron, cobalt, molybdenum, tungsten, tantalum, aluminium, titanium, zirconium, niobium, rhenium, yttrium, vanadium, carbon, boron or hafnium are some examples of the alloying additions used. Each addition serves a particular purpose in optimizing properties.
Creep resistance is dependent, in part, on slowing the speed of dislocation motion within a crystal structure. In modern Ni-based superalloys, the γ-Ni(Al,Ti) phase acts as a barrier to dislocation. For this reason, this γ; intermetallic phase, when present in high volume fractions, increases the strength of these alloys due to its ordered nature and high coherency with the γ matrix. The chemical additions of aluminum and titanium promote the creation of the γ phase. The γ phase size can be precisely controlled by careful precipitation strengthening heat treatments. Many superalloys are produced using a two-phase heat treatment that creates a dispersion of cuboidal γ particles known as the primary phase, with a fine dispersion between these known as secondary γ. In order to improve the oxidation resistance of these alloys, Al, Cr, B, and Y are added. The Al and Cr form oxide layers that passivate the surface and protect the superalloy from further oxidation while B and Y are used to improve the adhesion of this oxide scale to the substrate. Cr, Fe, Co, Mo and Re all preferentially partition to the γ matrix while Al, Ti, Nb, Ta, and V preferentially partition to the γ' precipitates and solid solution strengthen the matrix and precipitates respectively. In addition to solid solution strengthening, if grain boundaries are present, certain elements are chosen for grain boundary strengthening. B and Zr tend to segregate to the grain boundaries which reduces the grain boundary energy and results in better grain boundary cohesion and ductility. Another form of grain boundary strengthening is achieved through the addition of C and a carbide former, such as Cr, Mo, W, Nb, Ta, Ti, or Hf, which drives precipitation of carbides at grain boundaries and thereby reduces grain boundary sliding. | 1 | Applied and Interdisciplinary Chemistry |
Usually at moderately low energy, one or more nucleons are transferred between the projectile and target. These are useful in studying outer shell structure of nuclei. Transfer reactions can occur, from the projectile to the target; stripping reactions, or from the target to the projectile; pick-up reactions.
*(α,n) and (α,p) reactions. Some of the earliest nuclear reactions studied involved an alpha particle produced by alpha decay, knocking a nucleon from a target nucleus.
*(d,n) and (d,p) reactions. A deuteron beam impinges on a target; the target nuclei absorb either the neutron or proton from the deuteron. The deuteron is so loosely bound that this is almost the same as proton or neutron capture. A compound nucleus may be formed, leading to additional neutrons being emitted more slowly. (d,n) reactions are used to generate energetic neutrons.
*The strangeness exchange reaction (K, π) has been used to study hypernuclei.
*The reaction N(α,p)O performed by Rutherford in 1917 (reported 1919), is generally regarded as the first nuclear transmutation experiment. | 0 | Theoretical and Fundamental Chemistry |
Edward W Davis of the University of Minnesota is credited for devising the process of pelletizing iron ore.
Pelletizing iron ore is undertaken due to the excellent physical and metallurgical properties of iron ore pellets. Iron ore pellets are spheres of typically to be used as raw material for blast furnaces. They typically contain 64–72% Fe and various additional material adjusting the chemical composition and the metallurgic properties of the pellets. Typically limestone, dolomite and olivine is added and Bentonite is used as binder.
The process of pelletizing combines mixing of the raw material, forming the pellet and a thermal treatment baking the soft raw pellet to hard spheres. The raw material is rolled into a ball, then fired in a kiln or in travelling grate to sinter the particles into a hard sphere.
The configuration of iron ore pellets as packed spheres in the blast furnace allows air to flow between the pellets, decreasing the resistance to the air that flows up through the layers of material during the smelting. The configuration of iron ore powder in a blast furnace is more tightly-packed and restricts the air flow. This is the reason that iron ore is preferred in the form of pellets rather than in the form of finer particles. The quality of the iron ore pellets depends on different factors, which include feed particle size, amount of water used, disc rotating speed, inclination angle of the disc bottom, residence time in the disc as well as the quality and quantity of the binder(s) used. | 1 | Applied and Interdisciplinary Chemistry |
The simplest kind of magnetic phase is a paramagnet, where each individual spin behaves independently of the rest, just like atoms in an ideal gas. This highly disordered phase is the generic state of magnets at high temperatures, where thermal fluctuations dominate. Upon cooling, the spins will often enter a ferromagnet (or antiferromagnet) phase. In this phase, interactions between the spins cause them to align into large-scale patterns, such as domains, stripes, or checkerboards. These long-range patterns are referred to as "magnetic order," and are analogous to the regular crystal structure formed by many solids.
Quantum spin liquids offer a dramatic alternative to this typical behavior. One intuitive description of this state is as a "liquid" of disordered spins, in comparison to a ferromagnetic spin state, much in the way liquid water is in a disordered state compared to crystalline ice. However, unlike other disordered states, a quantum spin liquid state preserves its disorder to very low temperatures. A more modern characterization of quantum spin liquids involves their topological order, long-range quantum entanglement properties, and anyon excitations. | 0 | Theoretical and Fundamental Chemistry |
Mostly, SIRs have been investigated and used for the recovery of heavy metals. Applications include the removal of cadmium, vanadium, copper, chrome, iridium, etc. | 0 | Theoretical and Fundamental Chemistry |
Metallic nanofoams are a subcategorization of nanofoams; more specifically, there are nanofoams consisting of metals, often pure, that form interconnected networks of ligaments that make up the structure of the foam. A variety of metals are used, including copper, nickel, gold, and platinum. Metallic nanofoams may offer certain advantages over alternative polymer nanofoams; structurally, they retain the electrical conductivity of metals, offer increased ductility, as well as the higher surface area and nano-architecture properties offered by nanofoams. | 0 | Theoretical and Fundamental Chemistry |
* Magnesium aluminide, MgAl
* Titanium aluminide, TiAl
* Iron aluminides, including FeAl and FeAl
* Nickel aluminide, NiAl
See category for a list. | 1 | Applied and Interdisciplinary Chemistry |
* cyanide - ion, cyanide and isocyanide functional groups
* dicyanamide - or
* tricyanomethanide - or
* pentacyanoethanide - or
* pentacyanopropenide (pentacyanoallyl anion) -
* 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide
* tricyanomelaminate anion -
* melonate -
* anions - (n odd) and (n even)
* cyanoacetlyide - or
* cyanobutadiynylide - or
* cyanopolyynide anions - (n odd) | 0 | Theoretical and Fundamental Chemistry |
In molecular biology and pharmacology, a small molecule or micromolecule is a low molecular weight (≤ 1000 daltons) organic compound that may regulate a biological process, with a size on the order of 1 nm. Many drugs are small molecules; the terms are equivalent in the literature. Larger structures such as nucleic acids and proteins, and many polysaccharides are not small molecules, although their constituent monomers (ribo- or deoxyribonucleotides, amino acids, and monosaccharides, respectively) are often considered small molecules. Small molecules may be used as research tools to probe biological function as well as leads in the development of new therapeutic agents. Some can inhibit a specific function of a protein or disrupt protein–protein interactions.
Pharmacology usually restricts the term "small molecule" to molecules that bind specific biological macromolecules and act as an effector, altering the activity or function of the target. Small molecules can have a variety of biological functions or applications, serving as cell signaling molecules, drugs in medicine, pesticides in farming, and in many other roles. These compounds can be natural (such as secondary metabolites) or artificial (such as antiviral drugs); they may have a beneficial effect against a disease (such as drugs) or may be detrimental (such as teratogens and carcinogens). | 1 | Applied and Interdisciplinary Chemistry |
As of 2021, new laws do not directly include Armodafinil as a doping agent, but they do include Modafinil, as Armodafinil is an enantiomer of Modafinil it will show up on lab tests, but it can be debated if it is or not the same substance.
New laws state that simple possession is not a criminal offence and is punished with a fine and confiscation. Importing into Romania and exporting from Romania of the substance, without a valid medical prescription, is a criminal offence and is punished with jail time between two and seven years. | 0 | Theoretical and Fundamental Chemistry |
The general commercial availability of cadmium sulfide from the 1840s led to its adoption by artists, notably Van Gogh, Monet (in his London series and other works) and Matisse (Bathers by a River 1916–1919). The presence of cadmium in paints has been used to detect forgeries in paintings alleged to have been produced prior to the 19th century. | 0 | Theoretical and Fundamental Chemistry |
A number of publications, including H. H. Finlayson’s The Red Centre: Man and Beast in the Heart of Australia (1935), and Walkabout travel and geographical magazine (1934–1974), revised Australians concept of The Centre" from the picture presented in J. W. Gregorys The Dead Heart of Australia' (1909).
Leader-to-be of the Arnhem Land Expedition, Charles P. Mountford and his wife Bessie travelled over four months from Ernabella to Uluru in 1940, with Lauri Sheard and skilled cameleer Tommy Dodd undertaking an extensive study of the art and mythology surrounding Uluru and Kata Tjuta. The results of this endeavour were showcased through photographic exhibitions and a prize-winning film created in 1940, which subsequently became the foundation for Mountfords first publication Brown Men and Red Sand' (1948), and his 1945 lecture tour in the United States which paved the way for the establishment of the American-Australian Scientific Expedition to Arnhem Land.
The American-Australian Scientific Expedition to Arnhem Land, known as the last of the big expeditions, was not primarily about terrestrial exploration but aimed to advance knowledge. It focused on studying the natural environment and Aboriginal inhabitants. Taking place after World War II, it symbolized transformations in Australia and globally. The expedition served diplomatic objectives by showcasing collaboration between the United States and Australia, enhancing their trans-Pacific relationship. The missions public face hid negotiations that would shape this relationship for the 20th century. The expedition garnered domestic support due to Australias pro-American sentiments after WWII, as the nation adjusted to post-war changes and Britain's reduced global influence. The subsequent signing of the ANZUS Treaty by Robert Menzies continued this collaborative trajectory. | 1 | Applied and Interdisciplinary Chemistry |
Lipotoxicity in cardiac tissue is attributed to excess saturated fatty acids. The apoptosis that follows is believed to be caused by unfolded protein response in the endoplasmic reticulum. Researchers are working on treatments that will increase the oxidation of these fatty acids within the heart in order to prevent the lipotoxic effects. | 1 | Applied and Interdisciplinary Chemistry |
Antitermination was discovered in bacteriophage infections. A common feature in the control of phage infection is that very few of the phage genes can be transcribed by the bacterial host RNA polymerase. Among these genes, however, are regulators whose products allow the next set of phage genes to be expressed. One of these types of regulator is an antitermination protein. In the absence of the antitermination protein, RNA polymerase terminates at the terminator. When the antitermination protein is present, it continues past the terminator.
The best characterized example of antitermination is provided by lambda phage, in which the phenomenon was discovered. It is used at two stages of phage expression. The antitermination protein produced at each stage is specific for the particular transcription units that are expressed at that stage.
The host RNA polymerase initially transcribes two genes, which are called the immediate early genes (N and cro). The transition to the next stage of expression is controlled by preventing termination at the ends of the immediate early genes, with the result that the delayed early genes are expressed. The antitermination protein pN acts specifically on the immediate early transcription units. Later during infection, another antitermination protein pQ acts specifically on the late transcription unit, to allow its transcription to continue past a termination sequence.
The different specificities on pN and pQ establish an important general principle: RNA polymerase interacts with transcription units in such a way that an ancillary factor can sponsor antitermination specifically for some transcripts. Termination can be controlled with the same sort of precision as initiation.
The antitermination activity of pN is highly specific, but the antitermination event is not determined by the terminators t and t; the recognition site needed for antitermination lies upstream in the transcription unit, that is, at a different place from the terminator site at which the action eventually is accomplished.
The recognition sites required for pN action are called nut (for N utilization). The sites responsible for determining leftward and rightward antitermination are described as nut and nut, respectively.
When pN recognizes the nut site, it forms a persistent antitermination complex in cooperation with a number of E. coli host proteins. These include three host Nus proteins, NusA, B, and C. NusA is an interesting protein. By itself in E. coli, it is part of the transcription termination system. However, when co-opted by N, it participates in antitermination. The complex must act on RNA polymerase to ensure that the enzyme can no longer respond to the terminator. The variable locations of the nut sites indicate that this event is linked neither to initiation nor to termination, but can occur to RNA polymerase as it elongates the RNA chain past the nut site. Phages that are related to lambda have different N genes and different antitermination specificities. The region on the phage genome in which the nut sites lie has a different sequence in each of these phages, and each phage must therefore have characteristic nut sites recognized specifically by its own pN. Each of these pN products must have the same general ability to interact with the transcription apparatus in an antitermination capacity, but each product also has a different specificity for the sequence of DNA that activates the mechanism. | 1 | Applied and Interdisciplinary Chemistry |
Shneider-Miles scattering (also referred to as collisional scattering or quasi-Rayleigh scattering) is the quasi-elastic scattering of electromagnetic radiation by charged particles in a small-scale medium with frequent particle collisions. Collisional scattering typically occurs in coherent microwave scattering of high neutral density, low ionization degree microplasmas such as atmospheric pressure laser-induced plasmas. Shneider-Miles scattering is characterized by a 90° phase shift between the incident and scattered waves and a scattering cross section proportional to the square of the incident driving frequency (). Scattered waves are emitted in a short dipole radiation pattern. The variable phase shift present in semi-collisional scattering regimes allows for determination of a plasma's collisional frequency through coherent microwave scattering. | 0 | Theoretical and Fundamental Chemistry |
Curvibacter sp. is a gram-negative curved rod-formed bacterium which is the main colonizer of the epithelial cell surfaces of the early branching metazoan Hydra vulgaris. Sequencing the complete genome uncovered a circular chromosome (4.37 Mb), a plasmid (16.5 kb), and two operons coding each for an AHL (N-acyl-homoserine lactone) synthase (curI1 and curI2) and an AHL receptor (curR1 and curR2). Moreover, a study showed that these host associated Curvibacter bacteria produce a broad spectrum of AHL, explaining the presence of those operons. As mentioned before, AHL are the quorum sensing molecules of gram-negative bacteria, which means Curvibacter has a quorum sensing activity.
Even though their function in host-microbe interaction is largely unknown, Curvibacter quorum-sensing signals are relevant for host-microbe interactions. Indeed, due to the oxidoreductase activity of Hydra, there is a modification of AHL signalling molecules (3-oxo-homoserine lactone into 3-hydroxy-homoserine lactone) which leads to a different host-microbe interaction. On one hand, a phenotypic switch of the colonizer Curvibacter takes place. The most likely explanation is that the binding of 3-oxo-HSL and 3-hydroxy-HSL causes different conformational changes in the AHL receptors curR1 and curR2. As a result, there is a different DNA-binding motif affinity and thereby different target genes are activated. On the other hand, this switch modifies its ability to colonize the epithelial cell surfaces of Hydra vulgaris. Indeed, one explanation is that with a 3-oxo-HSL quorum-sensing signal, there is an up-regulation of flagellar assembly. Yet, flagellin, the main protein component of flagella, can act as an immunomodulator and activate the innate immune response in Hydra. Therefore, bacteria have less chance to evade the immune system and to colonize host tissues. Another explanation is that 3-hydroxy-HSL induces carbon metabolism and fatty acid degradation genes in Hydra. This allows the bacterial metabolism to adjust itself to the host growth conditions, which is essential for the colonization of the ectodermal mucus layer of Hydrae. | 1 | Applied and Interdisciplinary Chemistry |
A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. Blast refers to the combustion air being supplied above atmospheric pressure.
In a blast furnace, fuel (coke), ores, and flux (limestone) are continuously supplied through the top of the furnace, while a hot blast of air (sometimes with oxygen enrichment) is blown into the lower section of the furnace through a series of pipes called tuyeres, so that the chemical reactions take place throughout the furnace as the material falls downward. The end products are usually molten metal and slag phases tapped from the bottom, and waste gases (flue gas) exiting from the top of the furnace. The downward flow of the ore along with the flux in contact with an upflow of hot, carbon monoxide-rich combustion gases is a countercurrent exchange and chemical reaction process.
In contrast, air furnaces (such as reverberatory furnaces) are naturally aspirated, usually by the convection of hot gases in a chimney flue. According to this broad definition, bloomeries for iron, blowing houses for tin, and smelt mills for lead would be classified as blast furnaces. However, the term has usually been limited to those used for smelting iron ore to produce pig iron, an intermediate material used in the production of commercial iron and steel, and the shaft furnaces used in combination with sinter plants in base metals smelting.
Blast furnaces are estimated to have been responsible for over 4% of global greenhouse gas emissions between 1900 and 2015, but are difficult to decarbonize. | 1 | Applied and Interdisciplinary Chemistry |
Because surface tension manifests itself in various effects, it offers a number of paths to its measurement. Which method is optimal depends upon the nature of the liquid being measured, the conditions under which its tension is to be measured, and the stability of its surface when it is deformed. An instrument that measures surface tension is called tensiometer.
* Du Noüy ring method: The traditional method used to measure surface or interfacial tension. Wetting properties of the surface or interface have little influence on this measuring technique. Maximum pull exerted on the ring by the surface is measured.
*Wilhelmy plate method: A universal method especially suited to check surface tension over long time intervals. A vertical plate of known perimeter is attached to a balance, and the force due to wetting is measured.
* Spinning drop method: This technique is ideal for measuring low interfacial tensions. The diameter of a drop within a heavy phase is measured while both are rotated.
* Pendant drop method: Surface and interfacial tension can be measured by this technique, even at elevated temperatures and pressures. Geometry of a drop is analyzed optically. For pendant drops the maximum diameter and the ratio between this parameter and the diameter at the distance of the maximum diameter from the drop apex has been used to evaluate the size and shape parameters in order to determine surface tension.
* Bubble pressure method (Jaeger's method): A measurement technique for determining surface tension at short surface ages. Maximum pressure of each bubble is measured.
* Drop volume method: A method for determining interfacial tension as a function of interface age. Liquid of one density is pumped into a second liquid of a different density and time between drops produced is measured.
* Capillary rise method: The end of a capillary is immersed into the solution. The height at which the solution reaches inside the capillary is related to the surface tension by the equation discussed above.
* Stalagmometric method: A method of weighting and reading a drop of liquid.
* Sessile drop method: A method for determining surface tension and density by placing a drop on a substrate and measuring the contact angle (see Sessile drop technique).
*Du Noüy–Padday method: A minimized version of Du Noüy method uses a small diameter metal needle instead of a ring, in combination with a high sensitivity microbalance to record maximum pull. The advantage of this method is that very small sample volumes (down to few tens of microliters) can be measured with very high precision, without the need to correct for buoyancy (for a needle or rather, rod, with proper geometry). Further, the measurement can be performed very quickly, minimally in about 20 seconds.
* Vibrational frequency of levitated drops: The natural frequency of vibrational oscillations of magnetically levitated drops has been used to measure the surface tension of superfluid He. This value is estimated to be 0.375 dyn/cm at = 0 K.
* Resonant oscillations of spherical and hemispherical liquid drop: The technique is based on measuring the resonant frequency of spherical and hemispherical pendant droplets driven in oscillations by a modulated electric field. The surface tension and viscosity can be evaluated from the obtained resonant curves.
* Drop-bounce method: This method is based on aerodynamic levitation with a split-able nozzle design. After dropping a stably levitated droplet onto a platform, the sample deforms and bounces back, oscillating in mid-air as it tries to minimize its surface area. Through this oscillation behavior, the liquid's surface tension and viscosity can be measured. | 0 | Theoretical and Fundamental Chemistry |
Quantitative PCR is also used by microbiologists working in the fields of food safety, food spoilage and fermentation and for the microbial risk assessment of water quality (drinking and recreational waters) and in public health protection.
qPCR may also be used to amplify taxonomic or functional markers of genes in DNA taken from environmental samples. Markers are represented by genetic fragments of DNA or complementary DNA. By amplifying a certain genetic element, one can quantify the amount of the element in the sample prior to amplification. Using taxonomic markers (ribosomal genes) and qPCR can help determine the amount of microorganisms in a sample, and can identify different families, genera, or species based on the specificity of the marker. Using functional markers (protein-coding genes) can show gene expression within a community, which may reveal information about the environment. | 1 | Applied and Interdisciplinary Chemistry |
At boiling and higher temperatures the sum of the individual component partial pressures becomes equal to the overall pressure, which can symbolized as .
Under such conditions, Dalton's law would be in effect as follows:
:P = P + P + ...
Then for each component in the vapor phase:
:y = P / P, y = P / P, ... etc.
where P = partial pressure of component 1, = partial pressure of component 2, etc.
Raoults law is approximately valid for mixtures of components between which there is very little interaction other than the effect of dilution by the other components. Examples of such mixtures includes mixtures of alkanes, which are non-polar, relatively inert compounds in many ways, so there is little attraction or repulsion between the molecules. Raoults law states that for components 1, 2, etc. in a mixture:
:P = x P, P = x P, ... etc.
where P, P, etc. are the vapor pressures of components 1, 2, etc. when they are pure, and x, x, etc. are mole fractions of the corresponding component in the liquid.
Recall from the first section that vapor pressures of liquids are very dependent on temperature. Thus the P pure vapor pressures for each component are a function of temperature (T): For example, commonly for a pure liquid component, the Clausius–Clapeyron relation may be used to approximate how the vapor pressure varies as a function of temperature. This makes each of the partial pressures dependent on temperature also regardless of whether Raoults law applies or not. When Raoults law is valid these expressions become:
:PT = x PT, PT = x PT, ... etc.
At boiling temperatures if Raoult's law applies, the total pressure becomes:
:P = x PT + x PT + ... etc.
At a given P such as 1 atm and a given liquid composition, T can be solved for to give the liquid mixtures boiling point or bubble point, although the solution for T may not be mathematically analytical (i.e., may require a numerical solution or approximation). For a binary mixture at a given P, the bubble point T can become a function of x (or x') and this function can be shown on a two-dimensional graph like a binary boiling point diagram.
At boiling temperatures if Raoult's law applies, a number of the preceding equations in this section can be combined to give the following expressions for vapor mole fractions as a function of liquid mole fractions and temperature:
:y = x PT / P, y = x PT / P, ... etc.
Once the bubble point Ts as a function of liquid composition in terms of mole fractions have been determined, these values can be inserted into the above equations to obtain corresponding vapor compositions in terms of mole fractions. When this is finished over a complete range of liquid mole fractions and their corresponding temperatures, one effectively obtains a temperature T function of vapor composition mole fractions. This function effectively acts as the dew point T' function of vapor composition.
In the case of a binary mixture, x = 1 − x and the above equations can be expressed as:
:y = x PT / P, and
:y = (1 − x) PT / P
For many kinds of mixtures, particularly where there is interaction between components beyond simply the effects of dilution, Raoults law does not work well for determining the shapes of the curves in the boiling point or VLE diagrams. Even in such mixtures, there are usually still differences in the vapor and liquid equilibrium concentrations at most points, and distillation is often still useful for separating components at least partially. For such mixtures, empirical data is typically used in determining such boiling point and VLE diagrams. Chemical engineers have done a significant amount of research trying to develop equations for correlating and/or predicting VLE data for various kinds of mixtures which do not obey Raoults law well. | 0 | Theoretical and Fundamental Chemistry |
Like all other beta-lactam antibiotics, mezlocillin inhibits the third and last stage of bacterial cell wall synthesis by binding to penicillin binding proteins. This ultimately leads to cell lysis. | 0 | Theoretical and Fundamental Chemistry |
Typical aminophosphines undergo oxidation to the oxide. Alkylation, e.g. by methyl iodide, gives the phosphonium cation. | 0 | Theoretical and Fundamental Chemistry |
Fluorescence spectroscopy aka fluorometry or spectrofluorometry, is a type of electromagnetic spectroscopy which analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light of a lower energy, typically, but not necessarily, visible light. A complementary technique is absorption spectroscopy.
Devices that measure fluorescence are called fluorometers or fluorimeters. | 0 | Theoretical and Fundamental Chemistry |
Some organisms have lost mitochondrial DNA altogether. In these cases, genes encoded by the mitochondrial DNA have been lost or transferred to the nucleus. Cryptosporidium have mitochondria that lack any DNA, presumably because all their genes have been lost or transferred. In Cryptosporidium, the mitochondria have an altered ATP generation system that renders the parasite resistant to many classical mitochondrial inhibitors such as cyanide, azide, and atovaquone. Mitochondria that lack their own DNA have been found in a marine parasitic dinoflagellate from the genus Amoebophyra. This microorganism, A. cerati, has functional mitochondria that lack a genome. In related species, the mitochondrial genome still has three genes, but in A. cerati only a single mitochondrial gene — the cytochrome c oxidase I gene (cox1) — is found, and it has migrated to the genome of the nucleus. | 1 | Applied and Interdisciplinary Chemistry |
A portable, advanced sensor based on infrared spectroscopy in a hollow fiber matched to a silicon-micromachined fast gas chromatography column can analyze illegal stimulants and precursors with nanogram-level sensitivity.
Raman spectroscopy has been successfully tested to detect explosives and their precursors.
Technologies able to detect precursors in the environment could contribute to an early location of sites where illegal substances (both explosives and drugs of abuse) are produced. | 1 | Applied and Interdisciplinary Chemistry |
in which is the number of core samples, is the effective porosity, is the absolute permeability, is the interfacial tension or IFT, and is the imbibition or secondary drainage capillary pressure data vs. normalized water saturation. | 1 | Applied and Interdisciplinary Chemistry |
Anhydrous is a very polar liquid, having a dielectric constant of around 100. It has a high electrical conductivity, a consequence of autoprotolysis, i.e. self-protonation :
The equilibrium constant for autoprotolysis (25 °C) is:
The corresponding equilibrium constant for water, K is 10, a factor of 10 (10 billion) smaller.
In spite of the viscosity of the acid, the effective conductivities of the and ions are high due to an intramolecular proton-switch mechanism (analogous to the Grotthuss mechanism in water), making sulfuric acid a good conductor of electricity. It is also an excellent solvent for many reactions. | 0 | Theoretical and Fundamental Chemistry |
Every two anomers are designated alpha (α) or beta (β), according to the configurational relationship between the anomeric centre and the anomeric reference atom, hence they are relative stereodescriptors. The anomeric centre in hemiacetals is the anomeric carbon C-1; in hemiketals, it is the carbon derived from the carbonyl of the ketone (e.g. C-2 in -fructose). In aldohexoses the anomeric reference atom is the stereocenter that is farthest from anomeric carbon in the ring (the configurational atom, defining the sugar as or ). For example, in α--glucopyranose the reference atom is C-5.
If in the cyclic Fischer projection the exocyclic oxygen atom at the anomeric centre is cis (on the same side) to the exocyclic oxygen attached to the anomeric reference atom (in the OH group) the anomer is α. If the two oxygens are trans (on different sides) the anomer is β. Thus, the absolute configurations of the anomeric carbon and the reference atom are the same (both R or both S) in the α anomer and opposite (one R and the other S) in the β anomer. | 0 | Theoretical and Fundamental Chemistry |
In the same year that Brønsted and Lowry published their theory, G. N. Lewis created an alternative theory of acid–base reactions. The Lewis theory is based on electronic structure. A Lewis base is a compound that can give an electron pair to a Lewis acid, a compound that can accept an electron pair. Lewis's proposal explains the Brønsted–Lowry classification using electronic structure.
In this representation both the base, B, and the conjugate base, A, are shown carrying a lone pair of electrons and the proton, which is a Lewis acid, is transferred between them.
Lewis later wrote "To restrict the group of acids to those substances that contain hydrogen interferes as seriously with the systematic understanding of chemistry as would the restriction of the term oxidizing agent to substances containing oxygen." In Lewis theory an acid, A, and a base, B, form an adduct, AB, where the electron pair forms a dative covalent bond between A and B. This is shown when the adduct HN−BF forms from ammonia and boron trifluoride, a reaction that cannot occur in water because boron trifluoride reacts violently with water in a hydrolysis reaction.
These reactions illustrate that BF is an acid in both Lewis and Brønsted–Lowry classifications and show that both theories agree with each other.
Boric acid is recognised as a Lewis acid because of the reaction
In this case the acid does not split up but the base, HO, does. A solution of B(OH) is acidic because hydrogen ions are given off in this reaction.
There is strong evidence that dilute aqueous solutions of ammonia contain minute amounts of the ammonium ion
and that, when dissolved in water, ammonia functions as a Lewis base. | 0 | Theoretical and Fundamental Chemistry |
The periactive zone surrounds the active zone and is the site of endocytosis of the presynaptic terminal. In the periactive zone, scaffolding proteins such as intersectin 1 recruit proteins that mediate endocytosis such as dynamin, clathrin and endophilin. In Drosophila the intersectin homolog, Dap160, is located in the periactive zone of the neuromuscular junction and mutant Dap160 deplete synaptic vesicles during high frequency stimulation. | 1 | Applied and Interdisciplinary Chemistry |
Some reports have suggested that the extrinsic Fas pathway is sufficient to induce complete apoptosis in certain cell types through DISC assembly and subsequent caspase-8 activation. These cells are dubbed Type 1 cells and are characterized by the inability of anti-apoptotic members of the Bcl-2 family (namely Bcl-2 and Bcl-xL) to protect from Fas-mediated apoptosis. Characterized Type 1 cells include H9, CH1, SKW6.4 and SW480, all of which are lymphocyte lineages except the latter, which is a colon adenocarcinoma lineage. However, evidence for crosstalk between the extrinsic and intrinsic pathways exists in the Fas signal cascade.
In most cell types, caspase-8 catalyzes the cleavage of the pro-apoptotic BH3-only protein Bid into its truncated form, tBid. BH-3 only members of the Bcl-2 family exclusively engage anti-apoptotic members of the family (Bcl-2, Bcl-xL), allowing Bak and Bax to translocate to the outer mitochondrial membrane, thus permeabilizing it and facilitating release of pro-apoptotic proteins such as cytochrome c and Smac/DIABLO, an antagonist of inhibitors of apoptosis proteins (IAPs). | 1 | Applied and Interdisciplinary Chemistry |
The process by which the dosage and choice of flocculant are selected is called a jar test. The equipment used for jar testing consists of one or more beakers, each equipped with a paddle mixer. After the addition of flocculants, rapid mixing takes place, followed by slow mixing and later the sedimentation process. Samples can then be taken from the aqueous phase in each beaker. | 1 | Applied and Interdisciplinary Chemistry |
The reaction H + Br → 2 HBr proceeds by the following mechanism:
* Initiation
: Br → 2 Br• (thermal) or Br + hν → 2 Br• (photochemical)
: each Br atom is a free radical, indicated by the symbol "•" representing an unpaired electron.
* Propagation (here a cycle of two steps)
: Br• + H → HBr + H•
: H• + Br → HBr + Br•
: the sum of these two steps corresponds to the overall reaction H + Br → 2 HBr, with catalysis by Br• which participates in the first step and is regenerated in the second step.
* Retardation (inhibition)
: H• + HBr → H + Br•
: this step is specific to this example, and corresponds to the first propagation step in reverse.
* Termination 2 Br• → Br
: recombination of two radicals, corresponding in this example to initiation in reverse.
As can be explained using the steady-state approximation, the thermal reaction has an initial rate of fractional order (3/2), and a complete rate equation with a two-term denominator (mixed-order kinetics). | 0 | Theoretical and Fundamental Chemistry |
In thermodynamics, the excess chemical potential is defined as the difference between the chemical potential of a given species and that of an ideal gas under the same conditions (in particular, at the same pressure, temperature, and composition).
The chemical potential of a particle species is therefore given by an ideal part and an excess part.
Chemical potential of a pure fluid can be estimated by the Widom insertion method. | 0 | Theoretical and Fundamental Chemistry |
Most neuropeptides act on G-protein coupled receptors (GPCRs). Neuropeptide-GPCRs fall into two families: rhodopsin-like and the secretin class. Most peptides activate a single GPCR, while some activate multiple GPCRs (e.g. AstA, AstC, DTK). Peptide-GPCR binding relationships are highly conserved across animals. Aside from conserved structural relationships, some peptide-GPCR functions are also conserved across the animal kingdom. For example, neuropeptide F/neuropeptide Y signaling is structurally and functionally conserved between insects and mammals.
Although peptides mostly target metabotropic receptors, there is some evidence that neuropeptides bind to other receptor targets. Peptide-gated ion channels (FMRFamide-gated sodium channels) have been found in snails and Hydra. Other examples of non-GPCR targets include: insulin-like peptides and tyrosine-kinase receptors in Drosophila and atrial natriuretic peptide and eclosion hormone with membrane-bound guanylyl cyclase receptors in mammals and insects. | 1 | Applied and Interdisciplinary Chemistry |
Two limiting mechanisms, one operating under kinetic and the other thermodynamic control, have been identified for lateral lithiation reactions. The mechanisms of most lateral lithiations fall somewhere between these two limiting mechanisms, and the precise mechanism of a particular lithiation depends on two factors:
* The Lewis acidity of the organolithium reagent (RLi > LiNR)
* The Lewis basicity of the heteroatom substituent (N > O > S)
When both the Lewis acidity of the organolithium compound and the Lewis basicity of the substituent are high, as in lithiations of ortho-(dialkylamino)methyl toluenes with n-butyllithium in a non-coordinating solvent, coordination of the base to the heteroatom substituent takes place. Lithiation then occurs at the most kinetically accessible ortho benzylic position; ortho lithiation is slower in this case.
As either the Lewis acidity of the base or the coordinating ability of the substituent decrease, a mechanism involving purely inductive effects becomes more important. For instance, the lithiation of 1 with lithium di(isopropyl)amide (LDA) affords only the product of benzylic metalation 2; none of the ortho-lithiated product 3 is observed. This result is explained by a mechanism in which the amide substituent affects the acidity of the para benzylic position solely through inductive effects and coordination of the base is not operative. Deprotonation occurs to afford the most thermodynamically stable product.
In most cases, both mechanisms will lead to the same product, as the sites of kinetic and thermodynamic deprotonation will coincide. | 0 | Theoretical and Fundamental Chemistry |
Unlike DNA, which is a highly stable molecule, proteins are a heterogeneous class of molecules with different stability and physiochemical properties. Maintaining the proteins’ folding and function in an immobilized state over long periods of storage is a major challenge for protein microarrays. Cell-free methods provide the option to quickly obtaining protein microarrays on demand, thus eliminating any problems associated with long-term storage. | 1 | Applied and Interdisciplinary Chemistry |
Because the structure of the transition state is a first-order saddle point along a potential energy surface, the population of species in a reaction that are at the transition state is negligible. Since being at a saddle point along the potential energy surface means that a force is acting along the bonds to the molecule, there will always be a lower energy structure that the transition state can decompose into. This is sometimes expressed by stating that the transition state has a fleeting existence, with species only maintaining the transition state structure for the time-scale of vibrations of chemical bonds (femtoseconds). However, cleverly manipulated spectroscopic techniques can get us as close as the timescale of the technique allows. Femtochemical IR spectroscopy was developed for that reason, and it is possible to probe molecular structure extremely close to the transition point. Often, along the reaction coordinate, reactive intermediates are present not much lower in energy from a transition state making it difficult to distinguish between the two. | 0 | Theoretical and Fundamental Chemistry |
The approximate knife advance rate can be determined for a set of operating conditions using table 6 below. The table indicates the number of hours that the filter can operate in a one-inch pre coat cake; the required condition is that the advance blade must be at a constant position. This method can be used to check for optimum operation range.
If the operating parameter is higher than the optimum range, the user can reduce the knife advance rate and use a tighter grade of filter aid. This will result in less filter aid used (lower capital cost) and less filter aid being removed (lower disposal cost). However, if the operating parameter is lower than the optimum range, the user can increase the knife advanced rate (more production) and decrease the drum speed for less filter air usage (reduced operating cost). | 0 | Theoretical and Fundamental Chemistry |
3D cell-culture models exceed 2D culture systems by promoting higher levels of cell differentiation and tissue organization. 3D culture systems are more successful because the flexibility of the ECM gels accommodates shape changes and cell-cell connections – formerly prohibited by rigid 2D culture substrates. Nevertheless, even the best 3D culture models fail to mimic an organs cellular properties in many aspects, including tissue-to-tissue interfaces (e.g., epithelium and vascular endothelium), spatiotemporal gradients of chemicals, and the mechanically active microenvironments (e.g. arteries vasoconstriction and vasodilator responses to temperature differentials). The application of microfluidics in organs-on-chips enables the efficient transport and distribution of nutrients and other soluble cues throughout the viable 3D tissue constructs. Organs-on-chips are referred to as the next wave of 3D cell-culture models that mimic whole living organs' biological activities, dynamic mechanical properties and biochemical functionalities. | 1 | Applied and Interdisciplinary Chemistry |
In chemical terms, creatinine is a lactam and an imidazolidinone, so a spontaneously formed cyclic derivative of creatine.
Several tautomers of creatinine exist; ordered by contribution, they are:
*2-Amino-1-methyl-1H-imidazol-4-ol (or 2-amino-1-methylimidazol-4-ol)
*2-Amino-1-methyl-4,5-dihydro-1H-imidazol-4-one
*2-Imino-1-methyl-2,3-dihydro-1H-imidazol-4-ol (or 2-imino-1-methyl-3H-imidazol-4-ol)
*2-Imino-1-methylimidazolidin-4-one
*2-Imino-1-methyl-2,5-dihydro-1H-imidazol-4-ol (or 2-imino-1-methyl-5H-imidazol-4-ol)
Creatinine starts to decompose around 300 °C. | 1 | Applied and Interdisciplinary Chemistry |
A drive designed to read and write to 3D optical data storage media may have a lot in common with CD/DVD drives, particularly if the form factor and data structure of the media is similar to that of CD or DVD. However, there are a number of notable differences that must be taken into account when designing such a drive. | 0 | Theoretical and Fundamental Chemistry |
The gas centrifugation process uses a unique design that allows gas to constantly flow in and out of the centrifuge. Unlike most centrifuges which rely on batch processing, the gas centrifuge uses continuous processing, allowing cascading, in which multiple identical processes occur in succession.
The gas centrifuge consists of a cylindrical rotor, a casing, an electric motor, and three lines for material to travel. The gas centrifuge is designed with a casing that completely encloses the centrifuge. The cylindrical rotor is located inside the casing, which is evacuated of all air to produce a near frictionless rotation when operating. The motor spins the rotor, creating the centrifugal force on the components as they enter the cylindrical rotor. This force acts to separate the molecules of the gas, with heavier molecules moving towards the wall of the rotor, and the lighter molecules towards the central axis. There are two output lines, one for the fraction enriched in the desired isotope (in uranium separation, this is U-235), and one depleted in it. The output lines take these separations to other centrifuges to continue the centrifugation process. The process begins when the rotor is balanced in three stages. Most of the technical details on gas centrifuges are difficult to obtain because they are shrouded in "nuclear secrecy".
The early centrifuges used in the UK used an alloy body wrapped in epoxy impregnated glass fibre. Dynamic balancing of the assembly was accomplished by adding small traces of epoxy at the locations indicated by the balancing test unit. The motor was usually a pancake type located at the bottom of the cylinder. The early units were typically around 2 metres long (approx.), but subsequent developments gradually increased the length. The present generation are over 4 metres in length. The bearings are gas-based devices, as mechanical bearings would not survive at the normal operating speeds of these centrifuges.
A section of centrifuges would be fed with variable-frequency AC from an electronic (bulk) inverter, which would slowly ramp them up to the required speed, generally in excess of 50,000 rpm. One precaution was to quickly get past frequencies at which the cylinder was known to suffer resonance problems. The inverter is a high frequency unit capable of operating at frequencies around 1 kilohertz. The whole process is normally silent; if a noise is heard coming from a centrifuge, it is a warning of failure (which normally occurs very quickly). The design of the cascade normally allows for the failure of at least one centrifuge unit without compromising the operation of the cascade. The units are normally very reliable, with early models having operated continuously for over 30 years.
Later models have steadily increased the rotation speed of the centrifuges, as it is the velocity of the centrifuge wall that has the most effect on the separation efficiency.
A feature of the cascade system of centrifuges is that it is possible to increase plant throughput incrementally, by adding cascade "blocks" to the existing installation at suitable locations, rather than having to install a completely new line of centrifuges. | 0 | Theoretical and Fundamental Chemistry |
The history of gated drug delivery systems starts in the mid-1960s when the concept of zero order controlled drug delivery was first thought of. Researchers raced to be able to find a drug delivery platform that would be able to have perfectly sustained drug release. These efforts were initially on the macroscopic level with some of the first controlled drug delivery (CDD) devices being an ophthalmic insert, an intrauterine device, and a skin patch. In the 1970s the drug delivery field shifted from macroscopic systems and started to delve into microscopic systems. Ideas such as steroid loaded poly (lactic-co-glycolic acid), PLGA, microparticles came into existence. The next major jump came in the 1980s in the form of nanotherapeutics. There were some major technological advances that allowed this next generation of drug delivery systems to come along. Those ideas were PEGylation, active targeting, and the enhanced permeation and retention effect (EPR).
Some of the issues that had been seen with earlier renditions of nanoparticle drug delivery was that there were off target effects from drug being delivered to normal tissue, the delivery system wasnt highly controllable, and there wasnt optimal accumulation of drug in the targeted area. This is when the development of "smart drug delivery" originated. Encapsulated within the idea of smart drug delivery is the use of gated delivery systems. Researchers discovered that certain materials could be loaded and capped to prevent premature drug release. The caps could subsequently be removed using different external stimuli. This created a class of drug delivery systems that were able to solve a number of problems exhibited by normal nanoparticle drug delivery systems. These smart drug delivery systems are able to deliver the drug with minimal leakage, can be actively or passively targeted to different areas within the body, and will only release drug in the presence of certain triggers, creating a sustained local response and accumulation of drug at the disease area. | 1 | Applied and Interdisciplinary Chemistry |
Typically, shallow lakes are in one of two contrasting alternative stable states: a clear state with submerged macrophytes and piscivorous fish, or a turbid state dominated by phytoplankton and benthivorous fish. A switch from one state to the other is largely driven by the input of nutrients (phosphorus and nitrogen) to the ecosystem. If the nutrient loading exceeds a critical value, eutrophication causes a switch from the clear to the turbid state. As a result of urban water pollution and/or intensive agriculture in catchment areas, many of the world’s shallow lakes and ponds are in a eutrophic state with turbid waters and poor ecological quality. In this turbid state, the lake also becomes subject to algal blooms of toxic cyanobacteria (also called blue-green algae). Recovery of the clear state however is difficult as the critical nutrient loading for the switch back is often found to be lower than the critical loading towards the turbid state. Lowering the nutrient input thus does not automatically lead to a switch back to the clear water phase. Hence, the system shows hysteresis. | 1 | Applied and Interdisciplinary Chemistry |
The next part constructed the C ring starting from aldehyde 26, which was extended by one carbon atom to homologue 27 in a Wittig reaction with methoxymethylenetriphenylphosphine (Scheme 3). The acetonide group was removed by dilute hydrochloric acid and sodium iodide in dioxane and one hydroxyl group in the resulting diol 28 was protected as the triethylsilyl ether (TES) 29 with the corresponding silyl chloride and pyridine enabling oxidation of the remaining hydroxyl group to the ketone 30 with the Dess-Martin periodinane. Reaction with Eschenmoser's salt placed a methylene group (C20 in the Taxol framework) in the alpha position of the aldehyde to 31 and the next reaction introduced (the still lacking) C6 and C7 as the Grignard reagent of allyl bromide in a nucleophilic addition aided by zinc(II) chloride, which blocked the Grignard from attack on carbonate group, to alcohol 32. The newly formed alcohol was protected as the BOM ether 33 with BOMCl and N,N-diisopropylethylamine. After removal of the TES protecting group with ammonium fluoride, the carbonate group in 34 was converted to a hydroxybenzoate group by action of phenyllithium and the secondary alcohol to the acetate 35 by in situ reaction with acetic anhydride and DMAP. In the next step the acyloin group had its positions swapped by reaction with triazabicyclodecene (other amine bases fail) forming 36 and in the final steps ring closure of ring C was accomplished by ozonolysis at the allyl group to 37 and Aldol reaction with 4-pyrrolidinopyridine to 38. | 0 | Theoretical and Fundamental Chemistry |
Both enantiomers of pseudoephedrine are commercially available. Racemic pseudoephedrine has many medical uses. Because pseudoephedrine can be used to illegally make methamphetamine, the purchase of pseudoephedrine for use in academic or industrial research is rather regulated. As an alternative, Myers et al. reported the utility of pseudoephenamine chiral auxiliaries in alkylation reactions. While pseudoephenamine is not readily available from commercial sources, it can be synthesized with relative ease from benzil and cannot be used to make amphetamines.
Pseudoephedrine amides are typically prepared by acylation with an acyl chloride or anhydride.
<br /> | 0 | Theoretical and Fundamental Chemistry |
Two medals are awarded in Ørsted's name: the H. C. Ørsted Medal for Danish scientists, awarded by the Danish Society for the Dissemination of Natural Science (SNU), as founded by Ørsted, and the Oersted Medal for notable contributions in the teaching of physics in America, awarded by American Association of Physics Teachers.
The Technical University of Denmark hosts the H. C. Ørsted Lecture series for prominent and engaging researchers from around the world. | 1 | Applied and Interdisciplinary Chemistry |
Cegelski studied chemistry at SUNY Binghamton in New York and graduated summa cum laude and a member of Phi Beta Kappa in 1998. She then worked in the lab of Jacob Schaefer at Washington University in St. Louis (WUSTL), earning a PhD in Biophysical Chemistry in 2004. Her post-doctoral work was in Molecular Microbiology at the Washington University School of Medicine. | 0 | Theoretical and Fundamental Chemistry |
In cellular biology, paracrine signaling is a form of cell signaling, a type of cellular communication in which a cell produces a signal to induce changes in nearby cells, altering the behaviour of those cells. Signaling molecules known as paracrine factors diffuse over a relatively short distance (local action), as opposed to cell signaling by endocrine factors, hormones which travel considerably longer distances via the circulatory system; juxtacrine interactions; and autocrine signaling. Cells that produce paracrine factors secrete them into the immediate extracellular environment. Factors then travel to nearby cells in which the gradient of factor received determines the outcome. However, the exact distance that paracrine factors can travel is not certain.
Although paracrine signaling elicits a diverse array of responses in the induced cells, most paracrine factors utilize a relatively streamlined set of receptors and pathways. In fact, different organs in the body - even between different species - are known to utilize a similar sets of paracrine factors in differential development. The highly conserved receptors and pathways can be organized into four major families based on similar structures: fibroblast growth factor (FGF) family, Hedgehog family, Wnt family, and TGF-β superfamily. Binding of a paracrine factor to its respective receptor initiates signal transduction cascades, eliciting different responses. | 1 | Applied and Interdisciplinary Chemistry |
In thermochemistry, the Thomsen–Berthelot principle is a hypothesis in the history of chemistry which argued that all chemical changes are accompanied by the production of heat and that processes which occur will be ones in which the most heat is produced. This principle was formulated in slightly different versions by the Danish chemist Julius Thomsen in 1854 and by the French chemist Marcellin Berthelot in 1864. This early postulate in classical thermochemistry became the controversial foundation of a research program that would last three decades.
This principle came to be associated with what was called the thermal theory of affinity, which postulated that the heat evolved in a chemical reaction was the true measure of its affinity. | 0 | Theoretical and Fundamental Chemistry |
Carbohydrate-deficient transferrin is elevated in the blood of people with heavy alcohol consumption but elevated levels can also be found in a number of medical conditions. The limitations of the assay depend upon the methodology of the test. HPLC (High Performance Liquid Chromatography) can detect certain genetic variants and potential liver diseases affecting CDT.
Used with other tests, such as gamma glutamyl transferase (GGT), aspartate aminotransferase (AST), and alanine aminotransferase (ALT), carbohydrate-deficient transferrin can be a useful tool in identifying problem drinking, such as alcohol use disorder. However, it is less sensitive than phosphatidylethanol (PEth) in detecting current regular alcohol consumption. The ethanol conjugates ethyl glucuronide and ethyl sulfate remain positive for up to three days after ethanol consumption and are quite useful for detection of occult/denied alcohol use disorder. Both these substances are detectable clinically through urine drug testing by commercial toxicology labs.
CDT is measured by taking a sample of a patient's blood. Apparently healthy individuals with no or low reported alcohol consumption and a negative Alcohol Use Disorders Identification Test (AUDIT) will have a %CDT <1.7% (95th percentile for the social drinking population). Elevated levels of CDT suggest recent heavy alcohol consumption, especially if other liver-associated enzymes (such as GGT) are elevated. Although recent heavy alcohol use is most commonly associated with elevated CDT, certain rare liver disorders can also increase levels of CDT. CDT levels are less useful for detecting alcohol use disorder in people with other liver diseases. | 1 | Applied and Interdisciplinary Chemistry |
3D organ printing technology permits the fabrication of high degrees of complexity with great reproducibility, in a fast and cost-effective manner. 3D printing has been used in pharmaceutical research and fabrication, providing a transformative system allowing precise control of droplet size and dose, personalized medicine, and the production of complex drug-release profiles. This technology calls for implantable drug delivery devices, in which the drug is injected into the 3D printed organ and is released once in vivo. Also, organ printing has been used as a transformative tool for in vitro testing. The printed organ can be utilized in discovery and dosage research upon drug-release factors. | 1 | Applied and Interdisciplinary Chemistry |
The process itself is regulated through both positive and negative termination factors, usually through modification of the hairpin structure. This is accomplished through interactions with single stranded RNA that corresponds to the upstream area of the loop, resulting in disruption of the termination process. Furthermore, there is some implication that the nut site may also contribute to regulation, as it is involved in recruitment of some critical components in the formation of the hairpin. | 1 | Applied and Interdisciplinary Chemistry |
In poorly-managed soils, particularly on sloped ground, erosion and transport of soil sediment rich in POM can contaminate water bodies. Because POM provides a source of energy and nutrients, rapid build-up of organic matter in water can result in eutrophication. Suspended organic materials can also serve as a potential vector for the pollution of water with fecal bacteria, toxic metals or organic compounds. | 0 | Theoretical and Fundamental Chemistry |
Dew harvesting yields may be improved with passive daytime radiative cooling application. Selective PDRC emitters that have a high emissivity only at the atmospheric window (8–13 μm) and broadband emitters may produce varying results. In one study using a broadband PDRC, the research condensed "~8.5 mL day of water for 800 W m2 of peak solar intensity." Whereas selective emitters may be less advantageous in other contexts, they may be more advantageous for dew harvesting applications. PDRCs could improve atmospheric water harvesting by being combined with solar vapor generation systems to improve water collection rates. | 0 | Theoretical and Fundamental Chemistry |
The PKM1 isozyme is expressed in organs that are strongly dependent upon a high rate of energy regeneration, such as muscle and brain. | 1 | Applied and Interdisciplinary Chemistry |
When setting up their new comparative qPCR systems titled "Dots in Boxes" in 2017, New England Biolabs stated that they had designed the data collection portion around the MIQE guidelines so that the data fit all the minimum parameter checklists in the protocols. Other scientific instrument companies have assisted in guideline compliance by purposefully tailoring their devices for them, including Bio-Rad creating a mobile app that allows for active marking of the MIQE checklist as each step is completed.
An overview of the 10th anniversary since the publication of the MIQE guidelines was conducted in June 2020 and discussed the scientific studies that had produced better and more organized results when following the guidelines. In August 2020, an updated version of the guidelines for the digital PCR method was published to account for improvement in machinery, technologies, and techniques since the original 2013 release. Additional guideline steps were added for data analysis, while also providing a more simplified checklist table for researchers to use. An RT-qPCR targeting assay was developed alongside Stephen Bustin using the MIQE guidelines for clinical biomarkers in December 2020 in order to identify the clinical presence of COVID-19 viral particles during the COVID-19 pandemic. | 1 | Applied and Interdisciplinary Chemistry |
The addition of polyethylene glycol (PEG) to the process causes silica particles to aggregate into a macroporous continuous block, allowing access to a monolithic morphology. PEG polymers with allyl or silyl end groups with a molecular weight of greater than 2000 g mol are required. The Stöber process is initiated under neutral pH conditions, so that the PEG polymers will congregate around the outside of the growing particles, providing stabilization. Once the aggregates are sufficiently large, the PEG-stabilized particles will contact and irreversibly fuse together by "sticky aggregation" between the PEG chains. This continues until complete flocculation of all the particles has occurred and the monolith has been formed, at which point the monolith may be calcined and the PEG removed, resulting in a macroporous silica monolith. Both particle size and sticky aggregation can be controlled by varying the molecular weight and concentration of PEG. | 0 | Theoretical and Fundamental Chemistry |
Base excess is defined as the amount of strong acid that must be added to each liter of fully oxygenated blood to return the pH to 7.40 at a temperature of 37°C and a pCO of . A base deficit (i.e., a negative base excess) can be correspondingly defined by the amount of strong base that must be added.
A further distinction can be made between actual and standard base excess: actual base excess is that present in the blood, while standard base excess is the value when the hemoglobin is at 5 g/dl. The latter gives a better view of the base excess of the entire extracellular fluid.
Base excess (or deficit) is one of several values typically reported with arterial blood gas analysis that is derived from other measured data.
The term and concept of base excess were first introduced by Poul Astrup and Ole Siggaard-Andersen in 1958. | 1 | Applied and Interdisciplinary Chemistry |
The exact mechanism of the action of general anaesthetics has not been delineated. Halothane activates GABA and glycine receptors. It also acts as an NMDA receptor antagonist, inhibits nACh and voltage-gated sodium channels, and activates 5-HT and twin-pore K channels. It does not affect the AMPA or kainate receptors. | 0 | Theoretical and Fundamental Chemistry |
Halides are X-type ligands in coordination chemistry. The halides are usually good σ- and good π-donors. These ligands are usually terminal, but they might act as bridging ligands as well. For example, the chloride ligands of aluminium chloride bridge two aluminium centers, thus the compound with the empirical formula AlCl actually has the molecular formula of AlCl under ordinary conditions. Due to their π-basicity, the halide ligands are weak field ligands. Due to a smaller crystal field splitting energy, the halide complexes of the first transition series are all high spin when possible. These complexes are low spin for the second and third row transition series. Only [CrCl] is exchange inert.
Homoleptic metal halide complexes are known with several stoichiometries, but the main ones are the hexahalometallates and the tetrahalometallates. The hexahalides adopt octahedral coordination geometry, whereas the tetrahalides are usually tetrahedral. Square planar tetrahalides are known as are examples with 2- and 3-coordination.
Alfred Werner studied hexamminecobalt(III) chloride, and was the first to propose the correct structures of coordination complexes. Cisplatin, cis-Pt(NH)Cl, is a platinum drug bearing two chloride ligands. The two chloride ligands are easily displaced, allowing the platinum center to bind to two guanine units, thus damaging DNA.
Due to the presence of filled p orbitals, halide ligands on transition metals are able to reinforce π-backbonding onto a π-acid. They are also known to labilize cis-ligands. | 0 | Theoretical and Fundamental Chemistry |
The first bottle bank for non-deposit bottles (glasbak) was installed in Zeist in 1972. Glass is collected in three colours: white, green and brown.
There is a deposit for refillable beer bottles when returned to supermarkets. | 0 | Theoretical and Fundamental Chemistry |
The Antique Gas & Steam Engine Museum (AGSEM) is a living history museum founded in 1969. It is located on of county-owned land at 2040 N Santa Fe Ave. on the outskirts of Vista, California. The museum is a non-profit 501c(3) organization, run by several paid employees along with volunteer help.
The museum is open almost every day of the year and has two bi-annual shows, on the 3rd and 4th weekends of June and October. The museum also has other public and private events throughout the year.
Exhibits at the museum include: | 1 | Applied and Interdisciplinary Chemistry |
Different formulations of efficiency are possible depending on which outputs and inputs are considered. For instance, average quantum efficiency is the ratio between gross assimilation and either absorbed or incident light intensity. Large variability of measured quantum efficiency is reported in the literature between plants grown in different conditions and classified in different subtypes but the underpinnings are still unclear. One of the components of quantum efficiency is the efficiency of dark reactions, biochemical efficiency, which is generally expressed in reciprocal terms as ATP cost of gross assimilation (ATP/GA).
In photosynthesis ATP/GA depends mainly on and O concentration at the carboxylating sites of RuBisCO. When concentration is high and O concentration is low photorespiration is suppressed and assimilation is fast and efficient, with ATP/GA approaching the theoretical minimum of 3.
In photosynthesis concentration at the RuBisCO carboxylating sites is mainly the result of the operation of the concentrating mechanisms, which cost circa an additional 2 ATP/GA but makes efficiency relatively insensitive of external concentration in a broad range of conditions.
Biochemical efficiency depends mainly on the speed of delivery to the bundle sheath, and will generally decrease under low light when PEP carboxylation rate decreases, lowering the ratio of /O concentration at the carboxylating sites of RuBisCO. The key parameter defining how much efficiency will decrease under low light is bundle sheath conductance. Plants with higher bundle sheath conductance will be facilitated in the exchange of metabolites between the mesophyll and bundle sheath and will be capable of high rates of assimilation under high light. However, they will also have high rates of retro-diffusion from the bundle sheath (called leakage) which will increase photorespiration and decrease biochemical efficiency under dim light. This represents an inherent and inevitable trade off in the operation of photosynthesis. plants have an outstanding capacity to attune bundle sheath conductance. Interestingly, bundle sheath conductance is downregulated in plants grown under low light and in plants grown under high light subsequently transferred to low light as it occurs in crop canopies where older leaves are shaded by new growth. | 0 | Theoretical and Fundamental Chemistry |
The intrinsic hydrophobicity of a surface can be enhanced by being textured with different length scales of roughness. The red rose takes advantage of this by using a hierarchy of micro- and nanostructures on each petal to provide sufficient roughness for superhydrophobicity. More specifically, each rose petal has a collection of micropapillae on the surface and each papilla, in turn, has many nanofolds. The term "petal effect" describes the fact that a water droplet on the surface of a rose petal is spherical in shape, but cannot roll off even if the petal is turned upside down. The water drops maintain their spherical shape due to the superhydrophobicity of the petal (contact angle of about 152.4°), but do not roll off because the petal surface has a high adhesive force with water.
When comparing the "petal effect" to the "lotus effect", it is important to note some striking differences. The surface structure of the lotus leaf and the rose petal, as seen in Figure 9, can be used to explain the two different effects.
The lotus leaf has a randomly rough surface and low contact angle hysteresis, which means the water droplet is not able to wet the microstructure spaces between the spikes. This allows air to remain inside the texture, causing a heterogeneous surface composed of both air and solid. As a result, the adhesive force between the water and the solid surface is extremely low, allowing the water to roll off easily (i.e. "self-cleaning" phenomenon).
The rose petal's micro- and nanostructures are larger in scale than those of the lotus leaf, which allows the liquid film to impregnate the texture. However, as seen in Figure 9, the liquid can enter the larger-scale grooves, but it cannot enter into the smaller grooves. This is known as the Cassie impregnating wetting regime. Since the liquid can wet the larger-scale grooves, the adhesive force between the water and solid is very high. This explains why the water droplet will not fall off even if the petal is tilted at an angle or turned upside down. This effect will fail if the droplet has a volume larger than 10 µl because the balance between weight and surface tension is surpassed. | 0 | Theoretical and Fundamental Chemistry |
Recently it has been shown that a Michaelian signaling pathway can be converted to an ultrasensitive signaling pathway by the introduction of two positive feedback loops. In this synthetic biology approach, Palani and Sarkar began with a linear, graded response pathway, a pathway that showed a proportional increase in signal output relative to the amount of signal input, over a certain range of inputs. This simple pathway was composed of a membrane receptor, a kinase and a transcription factor. Upon activation the membrane receptor phosphorylates the kinase, which moves into the nucleus and phosphorylates the transcription factor, which turns on gene expression. To transform this graded response system into an ultrasensitive, or switch-like signaling pathway, the investigators created two positive feedback loops. In the engineered system, activation of the membrane receptor resulted in increased expression of both the receptor itself and the transcription factor. This was accomplished by placing a promoter specific for this transcription factor upstream of both genes. The authors were able to demonstrate that the synthetic pathway displayed high ultrasensitivity and bistability.
Recent computational analysis of the effects of a signaling proteins concentration on the presence of an ultrasensitive response has come to complementary conclusions about the influence of a signaling proteins concentration on the conversion of a graded response to an ultrasensitive one. Rather than focus on the generation of signaling proteins through positive feedback, however, the study instead focused on how the dynamics of a signaling proteins exit from the system influences the response. Soyer, Kuwahara, and Csika´sz-Nagy devised a signaling pathway composed of a protein (P) that possesses two possible states (unmodified P or modified P*) and can be modified by an incoming stimulus E. Furthermore, while the unmodified form, P, is permitted to enter or leave the system, P* is only allowed to leave (i.e. it is not generated elsewhere). After varying the parameters of this system, the researchers discovered that the modification of P to P* can shift between a graded response and an ultrasensitive response via the modification of the exit rates of P and P* relative to each other. The transition from an ultrasensitive response to E and a graded response to E was generated when the two rates went from highly similar to highly dissimilar, irrespective of the kinetics of the conversion from P to P* itself. This finding suggests at least two things: 1) the simplifying assumption that the levels of signaling molecules stay constant in a system can severely limit the understanding of ultrasensitivitys complexity; and 2) it may be possible to induce or inhibit ultrasensitivity artificially by regulating the rates of the entry and exit of signaling molecules occupying a system of interest. | 1 | Applied and Interdisciplinary Chemistry |
After completing his PhD, Berlin held numerous research positions at the N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences. In 1978, he became a senior research fellow under supervision of Vitalii Goldanski and a lecturer in the faculty of Chemical Physics at the Moscow Institute for Physics and Technology. In 1986, he was promoted to the position of the group leader and the head of the Laboratory of Non-Linear Physical and Chemical Processes. From 1986 until 1998, Berlin was a member of the Academic Council of the N. N. Semenov Institute of Chemical Physics.
In 2005, he became an elected member of the Executive Committee of the Miller Trust for Radiation Chemistry, UK. He also was an organizer, member of program committee and a co-chair of the Russian-French Seminar on Chemical Physics and a co-chair of the European Science Foundation Conference "Charge Transfer in Biosystems". In 1993-1994 Berlin was invited to teach PhD students and to perform scientific research in the Institute for Molecular Science in Okazaki, Japan. After working in Japan, he held the position of guest professor in Chemical Physics and Biophysics at the Institute of Theoretical Physics at Technical University of Munich (TUM), Germany. Following his appointment at TUM, Berlin joined the chemistry department of Northwestern University, where he is a research professor. Berlin was a member of the editorial boards of the scientific journals "Russian Chemical Bulletin", "Chemical Physics Report" and a guest editor of "Chemical Physics". | 0 | Theoretical and Fundamental Chemistry |
Additional materials are added to the iron ore (pellet feed) to meet the requirements of the final pellets. This is done by placing the mixture in the pelletizer, which can hold different types of ores and additives, and mixing to adjust the chemical composition and the metallurgic properties of the pellets. In general, the following stages are included in this period of processing: concentration / separation, homogenization of the substance ratios, milling, classification, increasing thickness, homogenization of the pulp and filtering. | 1 | Applied and Interdisciplinary Chemistry |
An elevated steatocrit is indicative of fat malabsorption resulting in steatorrhea. This generally results from pancreatic exocrine insufficiency but can also occur with severe small bowel disease i.e. celiac disease, liver diseases such as Primary Biliary Cirrhosis or medications that inhibit fat absorption such as orlistat. | 1 | Applied and Interdisciplinary Chemistry |
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