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IR photodesorption is a type of desorption that occurs when an infrared light hits a surface and activates processes involving the excitation of an internal vibrational mode of the previously absorbed molecules followed by the desorption of the species into the gas phase. One can selectively excite electrons or vibrations of the adsorbate or of the adsorbate-substrate coupled system. This relaxation of the bonds together with a sufficient energy exchange from the incident light to the system will eventually lead to desorption.
Generally, the phenomenon is more effective for weaker-bound physisorbed species, which have a smaller adsorption potential depth compared to that of the chemisorbed ones. In fact, a shallower potential requires lower laser intensities to set a molecule free from the surface and make IR-photodesorption experiments feasible, because the measured desorption times are usually longer than the inverse of the other relaxation rates in the problem. | 0 | Theoretical and Fundamental Chemistry |
The multiplication factor, , is defined as (see Nuclear chain reaction):
* If is greater than 1, the chain reaction is supercritical, and the neutron population will grow exponentially.
* If is less than 1, the chain reaction is subcritical, and the neutron population will exponentially decay.
* If , the chain reaction is critical and the neutron population will remain constant.
In an infinite medium, neutrons cannot leak out of the system and the multiplication factor becomes the infinite multiplication factor, , which is approximated by the four-factor formula. | 0 | Theoretical and Fundamental Chemistry |
A steam turbine generator consists of a series of steam turbines interconnected to each other and a generator on a common shaft. | 1 | Applied and Interdisciplinary Chemistry |
Hsalen may be synthesized by the condensation of ethylenediamine and salicylaldehyde.
Complexes of salen with metal cations may be made without isolating it from the reaction mixture. This is possible because the stability constant for the formation of the metal complexes are very high, due to the chelate effect.
:HL + M → ML + 2 H
where L stands for the ligand. The pyridine adduct of the cobalt(II) complex Co(salen)(py) (salcomine) has a square-pyramidal structure; it can act as a dioxygen carrier by forming a labile, octahedral O complex.
The name "salen ligands" is used for tetradentate ligands which have similar structures. For example, in salpn there is a methyl substituent on the bridge. It is used as a metal deactivation additive in fuels. The presence of bulky groups near the coordination site may enhance the catalytic activity of a metal complex and prevent its dimerization. Salen ligands derived from 3,5-di-tert-butylsalicylaldehyde fulfill these roles, and also increase the solubility of the complexes in non-polar solvents like pentane. Chiral "salen" ligands may be created by proper substitution of the diamine backbone, the phenyl ring, or both. An example is the ligand obtained by condensation of the C-symmetric trans-1,2-diaminocyclohexane with 3,5-di-tert-butylsalicylaldehyde. Chiral ligands may be used in asymmetric synthesis reactions, such as the Jacobsen epoxidation: | 0 | Theoretical and Fundamental Chemistry |
The δSi value of sediment porewater may be affected by post-depositional (diagenetic) precipitation or dissolution of Si. It is important to understand the extent and isotopic fractionations of these processes, as they alter the δSi values of the originally deposited sediments, and determine the δSi preserved in the rock record. Generally, precipitation of Si prefers the light isotope (Si) and leads to Si-enriched dissolved Si in the hosting solution. The isotopic effect of Si dissolution in porewater is yet to be clear, as some studies report a preference for Si during dissolution, while other studies document that isotopic fractionation was not expressed during dissolution of sediments. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, dAlemberts paradox (or the hydrodynamic paradox) is a contradiction reached in 1752 by French mathematician Jean le Rond dAlembert. dAlembert proved that – for incompressible and inviscid potential flow – the drag force is zero on a body moving with constant velocity relative to the fluid. Zero drag is in direct contradiction to the observation of substantial drag on bodies moving relative to fluids, such as air and water; especially at high velocities corresponding with high Reynolds numbers. It is a particular example of the reversibility paradox.
d’Alembert, working on a 1749 Prize Problem of the Berlin Academy on flow drag, concluded: "It seems to me that the theory (potential flow), developed in all possible rigor, gives, at least in several cases, a strictly vanishing resistance, a singular paradox which I leave to future Geometers [i.e. mathematicians - the two terms were used interchangeably at that time] to elucidate". A physical paradox indicates flaws in the theory.
Fluid mechanics was thus discredited by engineers from the start, which resulted in an unfortunate split – between the field of hydraulics, observing phenomena which could not be explained, and theoretical fluid mechanics explaining phenomena which could not be observed – in the words of the Chemistry Nobel Laureate Sir Cyril Hinshelwood.
According to scientific consensus, the occurrence of the paradox is due to the neglected effects of viscosity. In conjunction with scientific experiments, there were huge advances in the theory of viscous fluid friction during the 19th century. With respect to the paradox, this culminated in the discovery and description of thin boundary layers by Ludwig Prandtl in 1904. Even at very high Reynolds numbers, the thin boundary layers remain as a result of viscous forces. These viscous forces cause friction drag on streamlined objects, and for bluff bodies the additional result is flow separation and a low-pressure wake behind the object, leading to form drag.
The general view in the fluid mechanics community is that, from a practical point of view, the paradox is solved along the lines suggested by Prandtl. A formal mathematical proof is lacking, and difficult to provide, as in so many other fluid-flow problems involving the Navier–Stokes equations (which are used to describe viscous flow). | 1 | Applied and Interdisciplinary Chemistry |
Many d complexes of the first row metals exist in tetrahedral or square planar geometry. In some cases these geometries exist in measurable equilibria. For example, dichlorobis(triphenylphosphine)nickel(II) has been crystallized in both tetrahedral and square planar geometries. | 0 | Theoretical and Fundamental Chemistry |
* ATMOS observations. The [http://remus.jpl.nasa.gov/atmos/atmos.html Atmospheric Trace Molecule Spectroscopy] experiment (ATMOS) is an infrared spectrometer (a Fourier transform interferometer) that is designed to study the chemical composition of the atmosphere. In this section you will be able to read both general and detailed information as to why and how the instrument works. The ATMOS instrument has flown four times on the Space Shuttle since 1985. The predecessor to ATMOS, flown on aircraft and high-altitude balloon platforms, was born in the early 1970s out of concern for the effects of Super Sonic Transport exhaust products on the ozone layer. The experiment was redesigned for the Space Shuttle when the potential for ozone destruction by man-made chlorofluorocarbons was discovered and the need for global measurements became crucial.
* CRISTA observations. [https://archive.today/20011201094454/http://www.crista.uni-wuppertal.de/introduction.shtml CRISTA] is short for CRyogenic Infrared Spectrometers and Telescopes for the Atmosphere. It is a limb-scanning satellite experiment, designed and developed by the University of Wuppertal to measure infrared emissions of the Earth's atmosphere. Equipped with three telescopes and four spectrometers and cooled with liquid helium, CRISTA acquires global maps of temperature and atmospheric trace gases with very high horizontal and vertical resolution. The design enables the observation of small scale dynamical structures in the 15–150 km altitude region. | 1 | Applied and Interdisciplinary Chemistry |
The stationary phase comes in the form of a packed syringe-shaped cartridge, a 96 well plate, a 47- or 90-mm flat disk, or a microextraction by packed sorbent (MEPS) device, a SPE method that uses a packed sorbent material in a liquid handling syringe. These can be mounted on its specific type of extraction manifold. The manifold allows multiple samples to be processed by holding several SPE media in place and allowing for an equal number of samples to pass through them simultaneously. In a standard cartridge SPE manifold up to 24 cartridges can be mounted in parallel, while a typical disk SPE manifold can accommodate 6 disks. Most SPE manifolds are equipped with a vacuum port, where vacuum can be applied to speed up the extraction process by pulling the liquid sample through the stationary phase. The analytes are collected in sample tubes inside or below the manifold after they pass through the stationary phase.
Solid phase extraction cartridges and disks can be purchased with several stationary phases, each of which separates analytes depending on different chemical properties. The basis of most stationary phases is silica that has been bonded to a specific functional group. Some of these functional groups include hydrophobic alkyl or aryl chains chains of variable length (for reversed phase), quaternary ammonium or amino groups (for anion exchange), and aliphatic sulfonic acid or carboxyl groups (for cation exchange). | 0 | Theoretical and Fundamental Chemistry |
Figure 4 shows two examples of heterodyne autocorrelation functions of scattered light from sodium polystyrene sulfate solution (NaPSS; MW 400,000; 4 mg/mL in 10 mM NaCl). The oscillating correlation function shown by Fig. 4a is a result of interference between the scattered light and the modulated reference light.
The beat of Fig. 4b includes additionally the contribution from the frequency changes of light scattered by PSS molecules under an electrical field of 40 V/cm.
Figure 5 shows heterodyne power spectra obtained by Fourier transform of the autocorrelation functions shown in Fig. 4.
Figure 6 shows plots of Doppler shift frequencies measured at various cell depth and electric field strengths, where a sample is the NaPSS solution.
These parabolic curves are called profiles of electro-osmotic flow and indicate that the velocity of the particles changed at different depth.
The surface potential of the cell wall produces electro-osmotic flow.
Since the electrophoresis chamber is a closed system, backward flow is produced at the center of the cell.
Then the observed mobility or velocity from Eq. (7) is a result of the combination of osmotic flow and electrophoretic movement.
Electrophoretic mobility analysis has been studied by Mori and Okamoto [16], who have taken into account the effect of electro-osmotic flow at the side wall.
The profile of velocity or mobility at the center of the cell is given approximately by Eq. (11) for the case where k>5.
where
: cell depth
: apparent electrophoretic velocity of particle at position z.
: true electrophoretic velocity of the particles.
: thickness of the cell
: average velocity of osmotic flow at upper and lower cell wall.
: difference between velocities of osmotic flow at upper and lower cell wall.
: , a ratio between two side lengths of the rectangular cross section.
The parabolic curve of frequency shift caused by electro-osmotic flow shown in Fig. 6 fits with Eq. (11) with application of the least squares method.
Since the mobility is proportional to a frequency shift of the light scattered by a particle and the migrating velocity of a particle as indicated by Eq. (7), all the velocity, mobility, and frequency shifts are expressed by parabolic equations.
Then the true electrophoretic mobility of a particle, the electro-osmotic mobility at the upper and lower cell walls, ware obtained.
The frequency shift caused only by the electrophoresis of particles is equal to the apparent mobility at the stationary layer.
The velocity of the electrophoretic migration thus obtained is proportional to the electric field as shown in Fig. 7.
The frequency shift increases with increase of the scattering angle as shown in Fig. 8.
This result is in agreement with the theoretical Eq. (7). | 0 | Theoretical and Fundamental Chemistry |
Arrhenius plots, which are used to represent the effects of temperature on the rates of chemical and biophysical processes and on various transport phenomena in materials science, may exhibit deviations from linearity. Account of curvature is provided here by a formula, which involves a deformation of the exponential function, of the kind recently encountered in treatments of non-extensivity in statistical mechanics. | 0 | Theoretical and Fundamental Chemistry |
Brownian motion is the random motion of particles suspended in a medium (a liquid or a gas).
This motion pattern typically consists of random fluctuations in a particles position inside a fluid sub-domain, followed by a relocation to another sub-domain. Each relocation is followed by more fluctuations within the new closed volume. This pattern describes a fluid at thermal equilibrium, defined by a given temperature. Within such a fluid, there exists no preferential direction of flow (as in transport phenomena). More specifically, the fluids overall linear and angular momenta remain null over time. The kinetic energies of the molecular Brownian motions, together with those of molecular rotations and vibrations, sum up to the caloric component of a fluid's internal energy (the equipartition theorem).
This motion is named after the botanist Robert Brown, who first described the phenomenon in 1827, while looking through a microscope at pollen of the plant Clarkia pulchella immersed in water. In 1900, the French mathematician Louis Bachelier modeled the stochastic process now called Brownian motion in his doctoral thesis, The Theory of Speculation (Théorie de la spéculation), prepared under the supervision of Henri Poincaré. Then, in 1905, theoretical physicist Albert Einstein published a paper where he modeled the motion of the pollen particles as being moved by individual water molecules, making one of his first major scientific contributions.
The direction of the force of atomic bombardment is constantly changing, and at different times the particle is hit more on one side than another, leading to the seemingly random nature of the motion. This explanation of Brownian motion served as convincing evidence that atoms and molecules exist and was further verified experimentally by Jean Perrin in 1908. Perrin was awarded the Nobel Prize in Physics in 1926 "for his work on the discontinuous structure of matter".
The many-body interactions that yield the Brownian pattern cannot be solved by a model accounting for every involved molecule. Consequently, only probabilistic models applied to molecular populations can be employed to describe it. Two such models of the statistical mechanics, due to Einstein and Smoluchowski, are presented below. Another, pure probabilistic class of models is the class of the stochastic process models. There exist sequences of both simpler and more complicated stochastic processes which converge (in the limit) to Brownian motion (see random walk and Donsker's theorem). | 0 | Theoretical and Fundamental Chemistry |
Unlike NAPPA, PISA completely bypasses DNA immobilization as the DNA template is added as a free molecule in the reaction mixture. In 2006, another group refined and miniaturized this method by using multiple spotting technique to spot the DNA template and cell-free transcription and translation mixture on a high-density protein microarray with up to 13,000 spots. This was made possible by the automated system used to accurately and sequentially supply the reagents for the transcription/translation reaction occurs in a small, sub-nanolitre droplet. | 1 | Applied and Interdisciplinary Chemistry |
In alkanes, optimum overlap of atomic orbitals is achieved at 109.5°. The most common cyclic compounds have five or six carbons in their ring. Adolf von Baeyer received a Nobel Prize in 1905 for the discovery of the Baeyer strain theory, which was an explanation of the relative stabilities of cyclic molecules in 1885.
Angle strain occurs when bond angles deviate from the ideal bond angles to achieve maximum bond strength in a specific chemical conformation. Angle strain typically affects cyclic molecules, which lack the flexibility of acyclic molecules.
Angle strain destabilizes a molecule, as manifested in higher reactivity and elevated heat of combustion. Maximum bond strength results from effective overlap of atomic orbitals in a chemical bond. A quantitative measure for angle strain is strain energy. Angle strain and torsional strain combine to create ring strain that affects cyclic molecules.
Normalized energies that allow comparison of ring strains are obtained by measuring per methylene group (CH) of the molar heat of combustion in the cycloalkanes.
: per CH − 658.6 kJ = strain per CH
The value 658.6 kJ per mole is obtained from an unstrained long-chain alkane.
Cycloalkanes generally have less ring strain than cycloalkenes, which is seen when comparing cyclopropane and cyclopropene. | 0 | Theoretical and Fundamental Chemistry |
Archimedes reportedly exclaimed "Eureka" after he realized how to detect whether a crown is made of impure gold. While he did not use Archimedes principle in the widespread tale and used displaced water only for measuring the volume of the crown, there is an alternative approach using the principle: Balance the crown and pure gold on a scale in the air and then put the scale into water. According to Archimedes principle, if the density of the crown differs from the density of pure gold, the scale will get out of balance under water. | 1 | Applied and Interdisciplinary Chemistry |
The EPA defines hazardous waste as the following: A subset of solid wastes that pose substantial or potential threats to public health or the environment and meet any of the following criteria identified 40 CFR 260 and 261:
*It is specifically listed as a hazardous waste by EPA
*It exhibits one or more of the characteristics of hazardous waste (ignitability, corrosivity, reactivity, and/or toxicity);
*It is generated by the treatment of hazardous waste; or is contained in a hazardous waste. | 0 | Theoretical and Fundamental Chemistry |
Following the 2018 presidential election, Drahoš vowed to remain in public life, and in March 2018 announced his bid for the Prague 4 Senate seat in the 2018 election, nominated by Mayors and Independents and supported by TOP 09, KDU–ČSL and the Green Party. He won the election outright in the first round, with 52.65% of the vote. | 0 | Theoretical and Fundamental Chemistry |
Mycosubtilin is a natural lipopeptide with antifungal and hemolytic activities and isolated from Bacillus species. It belongs to the iturin lipopeptide family. | 0 | Theoretical and Fundamental Chemistry |
* Insertional mutagenesis uses the features of a TE to insert a sequence. In most cases, this is used to remove a DNA sequence or cause a frameshift mutation.
** In some cases the insertion of a TE into a gene can disrupt that gene's function in a reversible manner where transposase-mediated excision of the DNA transposon restores gene function.
** This produces plants in which neighboring cells have different genotypes.
** This feature allows researchers to distinguish between genes that must be present inside of a cell in order to function (cell-autonomous) and genes that produce observable effects in cells other than those where the gene is expressed. | 1 | Applied and Interdisciplinary Chemistry |
Mixed anion compounds exist that contain hydride with other anions. These include boride hydrides, carbohydrides, hydridonitrides, oxyhydrides and others. | 0 | Theoretical and Fundamental Chemistry |
One of the analogs of interest was made by isoindolinone replacement of the phthaloyl ring. It was given the name EM-12 (Figure 3). This replacement was thought to increase the bioavailability of the substance because of increased stability. The molecule had been reported to be an even more potent teratogenic agent than thalidomide in rats, rabbits and monkeys. Additionally, these analogs are more potent inhibitors of angiogenesis than thalidomide. As well, the amino-thalidomide and amino-EM-12 were potent inhibitors of TNF-α. These two analogs later got the name lenalidomide, which is the EM-12 amino analog, and pomalidomide, the thalidomide amino analog. | 1 | Applied and Interdisciplinary Chemistry |
Some polymers containing sulfone groups are useful engineering plastics. They exhibit high strength and resistance to oxidation, corrosion, high temperatures, and creep under stress. For example, some are valuable as replacements for copper in domestic hot water plumbing. Precursors to such polymers are the sulfones bisphenol S and 4,4′-dichlorodiphenyl sulfone. | 0 | Theoretical and Fundamental Chemistry |
Chlorosulfonated polyethylene (CSPE) is produced industrially by chlorosulfonation of polyethylene. CSPE is noted for its toughness, hence its use for roofing shingles.
An industrially important derivative is benzenesulfonyl chloride. In the laboratory, useful reagents include tosyl chloride, brosyl chloride, nosyl chloride and mesyl chloride. | 0 | Theoretical and Fundamental Chemistry |
As a type of emergency contraception, levonorgestrel is used after unprotected intercourse to reduce the risk of pregnancy. However, it can serve different hormonal purposes in its different methods of delivery. It is available for use in a variety of forms: | 0 | Theoretical and Fundamental Chemistry |
The fugacity of a condensed phase (liquid or solid) is defined the same way as for a gas:
and
It is difficult to measure fugacity in a condensed phase directly; but if the condensed phase is saturated (in equilibrium with the vapor phase), the chemical potentials of the two phases are equal (). Combined with the above definition, this implies that
When calculating the fugacity of the compressed phase, one can generally assume the volume is constant. At constant temperature, the change in fugacity as the pressure goes from the saturation press to is
This fraction is known as the Poynting factor. Using , where is the fugacity coefficient,
This equation allows the fugacity to be calculated using tabulated values for saturated vapor pressure. Often the pressure is low enough for the vapor phase to be considered an ideal gas, so the fugacity coefficient is approximately equal to 1.
Unless pressures are very high, the Poynting factor is usually small and the exponential term is near 1. Frequently, the fugacity of the pure liquid is used as a reference state when defining and using mixture activity coefficients. | 0 | Theoretical and Fundamental Chemistry |
Drag reducing agents have been found useful in reducing turbulence in the shipbuilding industry, for fire-fighting operations, oil-well fracturing processes, in irrigation systems and in central heating devices. Drag reducers can work in a couple of different fields. The most popular are crude oil, refined products and non-potable water. Currently there are several studies with ongoing tests in rats looking to see if drag reducers can help with blood flow. | 1 | Applied and Interdisciplinary Chemistry |
DNA is almost ideally suited for UV LD detection. The molecule is very long and very thin, making it very easy to orient in flow. This gives rise to a strong LD signal. DNA systems that have been studied using UV LD include DNA-enzyme complexes and DNA-ligand complexes, the formation of the latter being easily observable through kinetic experiments. | 0 | Theoretical and Fundamental Chemistry |
Constructed wetlands are manmade wetlands, which work as a bio-filtration system. They contain wetland vegetation and are mostly built on uplands and floodplains. Constructed wetlands are built this way to avoid connection or damage to natural wetlands and other aquatic resources. There are two main categories of constructed wetlands: subsurface flow system and free water surface system. Proper planning and operating can help avoid possible harm done to the wetlands, which are caused by alteration of natural hydrology and introduction of invasive species.
;Benefits
* Water efficiency: Constructed wetlands try to replicate natural wetland ecosystems. They are built to improve water efficiency and water quality. They also create wildlife habitats by using natural processes of plants, soils, and associated microorganisms. In these types of wetlands, vegetation can trap parts of suspended solids and slow down water flow; the microorganisms that live there process some other pollutants.
* Cost-effective: Wetlands have low operating and maintenance costs. They can also help with fluctuating water levels. Aesthetically, constructed wetlands are able to add greenery to its surrounding environment. It also helps to reduce unpleasing odors of wastewater. | 1 | Applied and Interdisciplinary Chemistry |
Fertilizer is often applied when field conditions are not optimal, particularly in large scale operations. Most studies, indicate that nitrogen losses can be reduced in these situations when a urease inhibitor is applied to the fertilizer.
Urease inhibitors prevent the urease enzyme from breaking down the urea. This increases the probability that urea will be absorbed into the soil after a rain event rather than volatilized into the atmosphere. This causes subsequent hydrolyzation to occur below the soil surface and decreases atmospheric losses. The use of inhibitors also decreases the localized zones of high pH common with untreated urea. | 0 | Theoretical and Fundamental Chemistry |
Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid or the liquid content of a substance, usually due to cooling.
For most substances, the melting and freezing points are the same temperature; however, certain substances possess differing solid-liquid transition temperatures. For example, agar displays a hysteresis in its melting point and freezing point. It melts at 85 °C (185 °F) and solidifies from 32 °C to 40 °C (89.6 °F to 104 °F). | 1 | Applied and Interdisciplinary Chemistry |
For scalars (most notably temperature), the self-similar logarithmic law of the wall has been theorized (first formulated by B. A. Kader) and observed in experimental and computational studies. In many cases, extensions to the original law of the wall formulation (usually through integral transformations) are generally needed to account for compressibility, variable-property and real fluid effects. | 1 | Applied and Interdisciplinary Chemistry |
α-Hydroxyketones, or acyloins, are an important synthetic motifs present in many natural products. α-Hydroxyketones have been synthesized in many ways, including reduction of α-diketones, substitution of a hydroxyl for a leaving group and direct oxidation of an enolate. Oxodiperoxymolybdenum(pyridine)-(hexamethylphosphoric triamide) (MoOPH) and N-sulfonyloxaziridines are the most common electrophilic sources of oxygen implemented in this process. One advantage of using N-sulfonyloxaziridines is that higher chiral induction is almost invariably observed relative to MoOPH and other oxidants. High yield (77–91%) and dr (95:5 – 99:1) are reported for α-hydroxylation with the Evans chiral auxiliary with N'-sulfonyloxaziridine as the electrophile. Chiral induction has been demonstrated with many other chiral ketones and ketones with chiral auxiliaries, including [http://upload.wikimedia.org/wikipedia/commons/0/03/SAMP_RAMP_Struktur.svg SAMP and RAMP].
Extensive work has been reported on asymmetric hydroxylation of prochiral enolates with camphorsulfonyloxaziridine derivatives, achieving moderate to high enantiomeric excess. The commonly accepted proposed transition state that justifies this stereochemical outcome involves an open transition state where the steric bulk of R determines the face of approach.
The selectivity of some hydroxylations may be drastically improved in some cases with the addition of coordinating groups alpha to the oxaziridine ring as oxaziridines 3b and 3c in the table above. In these instances it is proposed that the reaction proceeds through a closed transition state where the metal oxyanion is stabilized by chelation from the sulfate and coordinating groups on the camphor skeleton.
α-Hydroxylation with oxaziridines has been widely implemented in total synthesis. It is a key step in both the Holton Taxol total synthesis and the Wender Taxol total synthesis. Additionally, Forsyth implemented the transformation in his synthesis of the C3-C14 (substituted 1,7-Dioxaspiro[5.5]undec-3-ene) System of okadaic acid. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, intercalation is the reversible inclusion or insertion of a molecule (or ion) into layered materials with layered structures. Examples are found in graphite and transition metal dichalcogenides. | 0 | Theoretical and Fundamental Chemistry |
Even though consumption of food stimulates acid secretion and acid secretion activates PPIs, PPIs cannot inhibit all pumps. About 70% of pump enzyme is inhibited, as PPIs have a short half-life and not all pump enzymes are activated. It takes about 3 days to reach steady-state inhibition of acid secretion, as a balance is struck between covalent inhibition of active pumps, subsequent stimulation of inactive pumps after the drug has been eliminated from the blood, and de novo synthesis of new pumps. | 1 | Applied and Interdisciplinary Chemistry |
The IUPAC Gold Book defines an intermediate as a compound that has a lifetime greater than a molecular vibration, is formed (directly or indirectly) from the reactants, and reacts further to give (either directly or indirectly) the products of a chemical reaction. The lifetime condition distinguishes true, chemically distinct intermediates, both from vibrational states and from transition states (which, by definition, have lifetimes close to that of molecular vibration).
The different steps of a multi-step reaction often differ widely in their reaction rates. Where the difference is significant, an intermediate consumed more quickly than another may be described as a relative intermediate. A reactive intermediate is one which due to its short lifetime does not remain in the product mixture. Reactive intermediates are usually high-energy, are unstable and are seldom isolated. | 0 | Theoretical and Fundamental Chemistry |
The word ion was coined from neuter present participle of
Greek ἰέναι (ienai), meaning "to go". A cation is something that moves down (, kato, meaning "down") and an anion is something that moves up (, ano, meaning "up"). They are so called because ions move toward the electrode of opposite charge. This term was introduced (after a suggestion by the English polymath William Whewell) by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday did not know the nature of these species, but he knew that since metals dissolved into and entered a solution at one electrode and new metal came forth from a solution at the other electrode; that some kind of substance has moved through the solution in a current. This conveys matter from one place to the other. In correspondence with Faraday, Whewell also coined the words anode and cathode, as well as anion and cation as ions that are attracted to the respective electrodes.
Svante Arrhenius put forth, in his 1884 dissertation, the explanation of the fact that solid crystalline salts dissociate into paired charged particles when dissolved, for which he would win the 1903 Nobel Prize in Chemistry. Arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions, he proposed that ions formed even in the absence of an electric current. | 0 | Theoretical and Fundamental Chemistry |
Bacterial two hybrid methods (B2H or BTH) are usually carried out in E. coli and have some advantages over yeast-based systems. For instance, the higher transformation efficiency and faster rate of growth lends E. coli to the use of larger libraries (in excess of 10). The absence of requirements for a nuclear localisation signal to be included in the protein sequence and the ability to study proteins that would be toxic to yeast may also be major factors to consider when choosing an experimental background organism.
The methylation activity of certain E. coli DNA methyltransferase proteins may interfere with some DNA-binding protein selections. If this is anticipated, the use of an E. coli strain that is defective for a particular methyltransferase may be an obvious solution. The B2H may not be ideal when studying eukaryotic protein-protein interactions (e.g. human proteins) as proteins may not fold as in eukaryotic cells or may lack other processing. | 1 | Applied and Interdisciplinary Chemistry |
Most fluoride salts dissolve to give the bifluoride () anion. Sources of true F anions are rare because the highly basic fluoride anion abstracts protons from many, even adventitious, sources. Relative unsolvated fluoride, which does exist in aprotic solvents, is called "naked". Naked fluoride is a strong Lewis base, and a powerful nucleophile. Some quaternary ammonium salts of naked fluoride include tetramethylammonium fluoride and tetrabutylammonium fluoride. Cobaltocenium fluoride is another example. However, they all lack structural characterization in aprotic solvents. Because of their high basicity, many so-called naked fluoride sources are in fact bifluoride salts. In late 2016 imidazolium fluoride was synthesized that is the closest approximation of a thermodynamically stable and structurally characterized example of a "naked" fluoride source in an aprotic solvent (acetonitrile). The sterically demanding imidazolium cation stabilizes the discrete anions and protects them from polymerization. | 1 | Applied and Interdisciplinary Chemistry |
The alloys of tantalum–tungsten have high corrosion resistance, and refractory properties. The crystalline structure of the material is body-centered cubic with a substitutional solid solution with atoms of tungsten. The alloy also has a high melting point and can reach high elastic modulus and high tensile strength. | 1 | Applied and Interdisciplinary Chemistry |
Hyperpolarization is the nuclear spin polarization of a material in a magnetic field far beyond thermal equilibrium conditions determined by the Boltzmann distribution. It can be applied to gases such as Xe and He, and small molecules where the polarization levels can be enhanced by a factor of 10-10 above thermal equilibrium levels. Hyperpolarized noble gases are typically used in magnetic resonance imaging (MRI) of the lungs.
Hyperpolarized small molecules are typically used for in vivo metabolic imaging. For example, a hyperpolarized metabolite can be injected into animals or patients and the metabolic conversion can be tracked in real-time. Other applications include determining the function of the neutron spin-structures by scattering polarized electrons from a very polarized target (He), surface interaction studies, and neutron polarizing experiments. | 0 | Theoretical and Fundamental Chemistry |
Melzers reagent (also known as Melzers iodine reagent, Melzers solution or informally as Melzers) is a chemical reagent used by mycologists to assist with the identification of fungi, and by phytopathologists for fungi that are plant pathogens. | 0 | Theoretical and Fundamental Chemistry |
In spite of the second law of thermodynamics, crystallization of pure liquids usually begins at a lower temperature than the melting point, due to high activation energy of homogeneous nucleation. The creation of a nucleus implies the formation of an interface at the boundaries of the new phase. Some energy is expended to form this interface, based on the surface energy of each phase. If a hypothetical nucleus is too small, the energy that would be released by forming its volume is not enough to create its surface, and nucleation does not proceed. Freezing does not start until the temperature is low enough to provide enough energy to form stable nuclei. In presence of irregularities on the surface of the containing vessel, solid or gaseous impurities, pre-formed solid crystals, or other nucleators, heterogeneous nucleation may occur, where some energy is released by the partial destruction of the previous interface, raising the supercooling point to be near or equal to the melting point. The melting point of water at 1 atmosphere of pressure is very close to 0 °C (32 °F, 273.15 K), and in the presence of nucleating substances the freezing point of water is close to the melting point, but in the absence of nucleators water can supercool to before freezing. Under high pressure (2,000 atmospheres) water will supercool to as low as before freezing. | 1 | Applied and Interdisciplinary Chemistry |
Beerstone is a buildup that forms when oxalate, proteins, and calcium or magnesium salts from the grains and water in the beer brewing process precipitate and form scale on kegs, barrels and tap lines. The minerals adsorb to the surface of the container first, driven by charge attractions. Proteins are often coordinated to these minerals in the solution and can bind with them to the surface. In other cases proteins also adsorb to the minerals on the surface, making deposits difficult to remove, as well as providing a surface that can easily harbor microorganisms. If built-up beer stone inside tap lines flakes off, it can negatively affect the quality of the finished product by making beer hazy and contributing "off" flavors. It is also harmful from a nutritional standpoint: oxalates can decrease absorption of calcium in the body, in addition to increasing risk of kidney stone formation. | 1 | Applied and Interdisciplinary Chemistry |
Wind may have some effect on altering the efficiency of passive radiative cooling surfaces and technologies. Liu et al. proposes using a "tilt strategy and wind cover strategy" to mitigate effects of wind. The researchers found regional differences in regard to the impacts of wind cover in China, noting that "85% of China's areas can achieve radiative cooling performance with wind cover" whereas in northwestern China wind cover effects would be more substantial. Bijarniya et al. similarly proposes the use of a wind shield in areas susceptible to high winds. | 0 | Theoretical and Fundamental Chemistry |
This technique utilizes a high voltage () with a 0.5× Tris-borate buffer run across an agarose gel. This method differs from the traditional agarose gel electrophoresis by utilizing a higher voltage to facilitate a shorter run time as well as yield a higher band resolution. Other factors included in developing the technique of rapid agarose gel electrophoresis are gel thickness, and the percentage of agarose within the gel. | 1 | Applied and Interdisciplinary Chemistry |
*dextran, α-1,6-glucan
*glycogen, α-1,4- and α-1,6-glucan
*pullulan, α-1,4- and α-1,6-glucan
*starch, α-1,4- (such as amylose) and α-1,6-glucan (including amylopectin) | 1 | Applied and Interdisciplinary Chemistry |
A semi-circular bund (also known as a demi-lune or half-moon) is a rainwater harvesting technique consisting in digging semilunar holes in the ground with the opening perpendicular to the flow of water. | 1 | Applied and Interdisciplinary Chemistry |
The Leblanc-Deacon process is a modification of the Leblanc process. The Leblanc process was notoriously environmentally unfriendly, and resulted in some of the first Air and Water pollution acts. In 1874, Henry Deacon had derived a process to reduce HCl emissions as mandated by the Alkali Act. In this process, hydrogen chloride is oxidized by oxygen over a copper chloride catalyst, resulting in the production of chlorine. This was widely used in the paper and textile industries as a bleaching agent, and as a result sodium carbonate was no longer the primary product of these plants, and henceforth sold at a loss. | 0 | Theoretical and Fundamental Chemistry |
There are several steps in the HIV life cycle that may be interfered with, thus stopping the replication of the virus. A very critical step is the proteolytic cleavage of the polypeptide precursors into mature enzymes and structural proteins catalyzed by HIV protease. HIV protease inhibitors are peptide-like chemicals that competitively inhibit the action of the virus aspartyl protease. These drugs prevent proteolytic cleavage of HIV Gag and Pol polyproteins that include essential structural and enzymatic components of the virus. This prevents the conversion of HIV particles into their mature infectious form.
Protease inhibitors can alter adipocyte metabolism causing lipodystrophy, a common side effect associated with the use of most HIV protease inhibitors. Many mechanisms have been proposed, for example inhibition of adipocyte differentiation, triglyceride accumulation and increased lipolysis. Theories considering the effect of protease inhibitors on insulin-stimulated glucose uptake have also been linked to the lipodystrophic syndrome. It is possible that protease inhibitors can cause a decrease in insulin-stimulated tyrosine phosphorylation of IRS-1, representing inhibition of early steps in insulin signaling. Decreased adiponectin secretion and induced expression of interleukin-6 associated with HIV protease inhibitors may also contribute to inhibition of insulin-stimulated glucose uptake. | 1 | Applied and Interdisciplinary Chemistry |
In the United States, the General Mining Law of 1872 gave rights to explore and mine on public domain land; the original law did not require post-mining reclamation (Woody et al. 2011). Mined land reclamation requirements on federal land depended on state requirements until the passage of the Federal Land Policy and Management Act in 1976. Currently, mining on federal land must have a government-approved mining and reclamation plan before mining can start. Reclamation bonds are required. Mining on either federal, state, or private land is subject to the requirements of the Clean Air Act and the Clean Water Act.
One solution proposed to reclamation problems is the privatization of the land to be mined (Woody et al. 2011). | 1 | Applied and Interdisciplinary Chemistry |
The phenomenon of bipolar electrochemistry is known since the 1970s and is used in industry in some electrolytic reactors. The interest of the scientific community for this concept seems to increase a lot since Martin Fleischmann and co-workers demonstrated that water splitting was possible using micrometer-sized bipolar electrodes. Recently, several applications in such domains as synthesis of dissymmetrical micro- and nano-structures analytical chemistry material science, microelectronics and microobject propulsion have been developed. | 0 | Theoretical and Fundamental Chemistry |
For most stable isotopes, the magnitude of fractionation from kinetic and equilibrium fractionation is very small; for this reason, enrichments are typically reported in "per mil" (‰, parts per thousand). These enrichments (δ) represent the ratio of heavy isotope to light isotope in the sample over the ratio of a standard. That is, | 0 | Theoretical and Fundamental Chemistry |
If the master equation possesses nonlinear transition rates, it may be impossible to solve it analytically. The system size expansion utilises the ansatz that the variance of the steady-state probability distribution of constituent numbers in a population scales like the system size. This ansatz is used to expand the master equation in terms of a small parameter given by the inverse system size.
Specifically, let us write the , the copy number of component , as a sum of its "deterministic" value (a scaled-up concentration) and a random variable , scaled by :
The probability distribution of can then be rewritten in the vector of random variables :
Consider how to write reaction rates and the step operator in terms of this new random variable. Taylor expansion of the transition rates gives:
The step operator has the effect and hence :
We are now in a position to recast the master equation.
This rather frightening expression makes a bit more sense when we gather terms in different powers of . First, terms of order give
These terms cancel, due to the macroscopic reaction equation
The terms of order are more interesting:
which can be written as
where
and
The time evolution of is then governed by the linear Fokker–Planck equation with coefficient matrices and (in the large- limit, terms of may be neglected, termed the linear noise approximation). With knowledge of the reaction rates and stoichiometry , the moments of can then be calculated.
The approximation implies that fluctuations around the mean are Gaussian distributed. Non-Gaussian features of the distributions can be computed by taking into account higher order terms in the expansion. | 0 | Theoretical and Fundamental Chemistry |
IEC/RP MMC combines the advantages of RPLC and IEC. For example, WAX/RP has increased separation power and degree of freedom in adjusting the separation selectivity when compared with single WAX or RPLC. | 0 | Theoretical and Fundamental Chemistry |
Following his PhD, Mansfield was invited to postdoctoral research with Charlie Slichter at the University of Illinois at Urbana–Champaign, where he carried out an NMR study of doped metals.
In 1964, Mansfield returned to England to take up a place as a lecturer at Nottingham University where he could continue his studies in multiple-pulse NMR. He was successively appointed Senior Lecturer in 1968 and Reader in 1970. During this period his team developed the MRI equipment with the help of grants from the Medical Research Council. It was not until the 1970s with Paul Lauterburs and Mansfields developments that NMR could be used to produce images of the body. In 1979 Mansfield was appointed Professor of the Department of Physics until his retirement in 1994.
* 1962: Research Associate, Department of Physics, University of Illinois
* 1964: Lecturer, Department of Physics, University of Nottingham
* 1968: Senior Lecturer, Department of Physics, University of Nottingham
* 1970: Reader, Department of Physics, University of Nottingham
* 1972–73: Senior Visitor, Max Planck Institute for Medical Research, Heidelberg
* 1979: Professor, Department of Physics, University of Nottingham
Mansfield is credited with inventing slice selection for MRI - i.e. the method by which a localised axial slice of a subject can be selectively imaged, rather than the entire subject - and understanding how the radio signals from MRI can be mathematically analysed, making interpretation of the signals into a useful image a possibility. He is also credited with discovering how fast imaging could be possible by developing the MRI protocol called echo-planar imaging. Echo-planar imaging allows T2* weighted images to be collected many times faster than previously possible. It also has made functional magnetic resonance imaging (fMRI) feasible.
Whilst working at Nottingham University, Mansfield tested the first full body prototype, installed just before Christmas, 1978. Mansfield was so keen, that he volunteered to test it himself and produced the first scan of a live patient. The prototype machine is now an exhibit, in the Medical Section of the Science Museum. | 0 | Theoretical and Fundamental Chemistry |
Two drops of iron(III) chloride are added to a test tube with distilled water. After mixing, it is divided into two parts. Add one millilitre of gastric juice in one test tube and the same volume of distilled water in the other test tube, which is acting as a control. The test tube with the gastric juice turns yellow in the presence of lactic acid due to the formation of ferric lactate. | 0 | Theoretical and Fundamental Chemistry |
Ions are ubiquitous in nature and are responsible for diverse phenomena from the luminescence of the Sun to the existence of the Earth's ionosphere. Atoms in their ionic state may have a different color from neutral atoms, and thus light absorption by metal ions gives the color of gemstones. In both inorganic and organic chemistry (including biochemistry), the interaction of water and ions is extremely important; an example is energy that drives the breakdown of adenosine triphosphate (ATP). | 0 | Theoretical and Fundamental Chemistry |
# Accessibility: Run over 200 regularly updated analysis and visualization tools (that support data preprocessing, gene expression analysis, proteomics, Single nucleotide polymorphism (SNP) analysis, flow cytometry, and next-generation sequencing) and create analytic workflows without any programming through a point and click user interface.
# Reproducibility: Automated history and provenance tracking with versioning so that any user can share, repeat and understand a complete computational analysis
# Extensibility: Computational users can import their methods and code for sharing using tools that support easy creation and integration
# Multiple interfaces: Web browser, application, and programmatic interfaces make analysis modules and pipelines available to a broad range of users; public hosted server | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen–deuterium exchange (also called H–D or H/D exchange) is a chemical reaction in which a covalently bonded hydrogen atom is replaced by a deuterium atom, or vice versa. It can be applied most easily to exchangeable protons and deuterons, where such a transformation occurs in the presence of a suitable deuterium source, without any catalyst. The use of acid, base or metal catalysts, coupled with conditions of increased temperature and pressure, can facilitate the exchange of non-exchangeable hydrogen atoms, so long as the substrate is robust to the conditions and reagents employed. This often results in perdeuteration: hydrogen-deuterium exchange of all non-exchangeable hydrogen atoms in a molecule.
An example of exchangeable protons which are commonly examined in this way are the protons of the amides in the backbone of a protein. The method gives information about the solvent accessibility of various parts of the molecule, and thus the tertiary structure of the protein. The theoretical framework for understanding hydrogen exchange in proteins was first described by Kaj Ulrik Linderstrøm-Lang and he was the first to apply H/D exchange to study proteins. | 0 | Theoretical and Fundamental Chemistry |
If carbon dioxide, carbonic acid, hydrogen ions, bicarbonate and carbonate are all dissolved in water, and at chemical equilibrium, their equilibrium concentrations are often assumed to be given by:
where the subscript eq denotes that these are equilibrium concentrations, K is the equilibrium constant for the reaction + H + (i.e. the first acid dissociation constant for carbonic acid), K is the equilibrium constant for the reaction H + (i.e. the second acid dissociation constant for carbonic acid), and DIC is the (unchanging) total concentration of dissolved inorganic carbon in the system, i.e. [] + [] + []. K, K and DIC each have units of a concentration, e.g. mol/L.
A Bjerrum plot is obtained by using these three equations to plot these three species against , for given K, K and DIC. The fractions in these equations give the three species' relative proportions, and so if DIC is unknown, or the actual concentrations are unimportant, these proportions may be plotted instead.
These three equations show that the curves for and intersect at , and the curves for and intersect at . Therefore, the values of K and K that were used to create a given Bjerrum plot can easily be found from that plot, by reading off the concentrations at these points of intersection. An example with linear Y axis is shown in the accompanying graph. The values of K and K, and therefore the curves in the Bjerrum plot, vary substantially with temperature and salinity. | 0 | Theoretical and Fundamental Chemistry |
Sulfur can replace oxygen, either in the carbonyl group or in the bridge. In the former case, the name of the acyl group is enclosed in parentheses to avoid ambiguity in the name, e.g., (thioacetic) anhydride (CHC(S)OC(S)CH). When two acyl groups are attached to the same sulfur atom, the resulting compound is called a thioanhydride, e.g., acetic thioanhydride ((CHC(O))S). | 0 | Theoretical and Fundamental Chemistry |
The NS radical was detected by LIF spectrum as the product of photolysis of tetranitrogen tetrasulfide (NS) gas by a 248 nm laser. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the principle of least motion is the hypothesis that when multiple species with different nuclear structures could theoretically form as products of a given chemical reaction, the more likely to form tends to be the one requiring the least amount of change in nuclear structure or the smallest change in nuclear positions. | 0 | Theoretical and Fundamental Chemistry |
She graduated from Pierre and Marie Curie University. She studied the price of land in the 1700s and the Riverstrahler model of river nutrient transfer. | 0 | Theoretical and Fundamental Chemistry |
Alzheimers disease (AD) is the most common cause of dementia in the elderly. AD is a neurodegenerative disease characterized by the loss of cognitive functioning - thinking, remembering and reasoning- and behavioral abilities to such an extent that it interferes with a persons daily life and activities. The neuropathological hallmarks of AD include amyloid plaques and neurofibrillary tangles, which lead to neuronal death. Studies in animal models of AD have shown that p75NTR contributes to amyloid β-induced neuronal damage. In humans with AD, increases in p75NTR expression relative to TrkA have been suggested to be responsible for the loss of cholinergic neurons. Increases in proNGF in AD indicate that the Neurotrophin environment is favorable for p75NTR/sortilin signaling and supports the theory that age-related neural damage is facilitated by a shift toward proNGF-mediated signaling. A recent study found that activation of Ngfr signaling in astroglia of Alzheimers disease mouse model enhanced neurogenesis and reduced two hallmarks of Alzheimers disease. This study also found that NGFR signaling in humans is age-related and correlates with proliferative potential of neural progenitors. | 1 | Applied and Interdisciplinary Chemistry |
To obtain the desired measurement of , it is not sufficient to just measure .
The temperature at the reference junctions must be already known.
Two strategies are often used here:
* "Ice bath" method: The reference junction block is immersed in a semi-frozen bath of distilled water at atmospheric pressure. The precise temperature of the melting point phase transition acts as a natural thermostat, fixing to 0 °C.
* Reference junction sensor (known as ""): The reference junction block is allowed to vary in temperature, but the temperature is measured at this block using a separate temperature sensor. This secondary measurement is used to compensate for temperature variation at the junction block. The thermocouple junction is often exposed to extreme environments, while the reference junction is often mounted near the instrument's location. Semiconductor thermometer devices are often used in modern thermocouple instruments.
In both cases the value is calculated, then the function is searched for a matching value. The argument where this match occurs is the value of : | 1 | Applied and Interdisciplinary Chemistry |
Whiting events have a unique effect on the waters around them. The fact that calcium carbonate clouds increase turbidity and light reflectance holds implications for organisms and processes that depend on light. In addition, whiting events can function as a transport mechanism for organic carbon to the benthic zone, which is relevant to nutrient cycling. The cyanobacteria abundant clouds also hold the potential to act as a means to study the microorganism's role in carbon cycling (especially in relation to climate change) and their possible role in finding petroleum source rocks. | 0 | Theoretical and Fundamental Chemistry |
Despite being a CNS stimulant, the addiction and dependence liabilities of modafinil are considered low. The exact mechanisms of action of modafinil are not known, and it is believed that pharmacological profile of modafinil is different from that of the classical stimulants. Although modafinil shares biochemical mechanisms with stimulant drugs, it is less likely to have mood-elevating properties. The similarities in effects with caffeine are not clearly established. Unlike other stimulants, modafinil does not induce a strong subjective feeling of pleasure or reward, which is commonly associated with euphoria, an intense feeling of well-being. Euphoria is a potential indicator of drug abuse, which is the compulsive and excessive use of a substance despite adverse consequences. In comparison to classical stimulants, modafinil exhibits a low propensity for abuse, as it lacks significantly expressed pleasurable or euphoric effects. Albeit to a lower degree than classical stimulants, modafinil still produces psychoactive, euphoric, and subjective effects typical for abused stimulants.
Modafinil was not observed to promote overuse or misuse, even in people who have a history of cocaine addiction. Despite the initial belief that modafinil carried no abuse potential, emerging evidence suggests that it works at the same neurobiological mechanisms as other addictive stimulants. Consequently, there exists a potential risk of modafinil abuse, necessitating prudent consideration and caution when prescribing or using this medication. Modafinil exhibits a lower response on the amphetamine scale of the addiction research center inventory, suggesting reduced propensity for abuse compared to amphetamine.
The US Drug Enforcement Administration has classified modafinil as a Schedule IV controlled substance; the medicine is recognized for having valid medical uses with low addiction potential. The International Narcotics Control Board does not classify it as a narcotic or a psychotropic substance. | 0 | Theoretical and Fundamental Chemistry |
Physicist Dr David Criswell suggests the Moon is the optimum location for solar power stations, and promotes lunar-based solar power. The main advantage he envisions is construction largely from locally available lunar materials, using in-situ resource utilization, with a teleoperated mobile factory and crane to assemble the microwave reflectors, and rovers to assemble and pave solar cells, which would significantly reduce launch costs compared to SBSP designs. Power relay satellites orbiting around earth and the Moon reflecting the microwave beam are also part of the project. A demo project of 1 GW starts at $50 billion. The Shimizu Corporation use combination of lasers and microwave for the Luna Ring concept, along with power relay satellites. | 0 | Theoretical and Fundamental Chemistry |
Due to the energy range typically used in ion scattering experiments (> 500 eV), effects of thermal vibrations, phonon oscillations, and interatomic binding are ignored since they are far below this range (~a few eV), and the interaction of particle and surface may be thought of as a classical two-body elastic collision problem. Measuring the energy of ions scattered in this type of interaction can be used to determine the elemental composition of a surface, as is shown in the following:
Two-body elastic collisions are governed by the concepts of energy and momentum conservation. Consider a particle with mass m, velocity v, and energy given as impacting another particle at rest with mass m. The energies of the particles after collision are and where and thus . Additionally, we know . Using trigonometry we are able to determine
Similarly, we know
In a well-controlled experiment the energy and mass of the primary ions (E and m, respectively) and the scattering or recoiling geometries are all known, so determination of surface elemental composition is given by the correlation between E or E and m. Higher energy scattering peaks correspond to heavier atoms and lower energy peaks correspond to lighter atoms. | 0 | Theoretical and Fundamental Chemistry |
In 1960 John Nuckolls published the concept of inertial confinement fusion (ICF). The laser, introduced the same year, turned out to be a suitable "driver".
In 1961 the Soviet Union tested its 50 megaton Tsar Bomba, the most powerful thermonuclear weapon ever.
Spitzer published a key plasma physics text at Princeton in 1963. He took the ideal gas laws and adapted them to an ionized plasma, developing many of the fundamental equations used to model a plasma.
Laser fusion was suggested in 1962 by scientists at LLNL. Initially, lasers had little power. Laser fusion (inertial confinement fusion) research began as early as 1965.
At the 1964 World's Fair, the public was given its first fusion demonstration. The device was a Theta-pinch from General Electric. This was similar to the Scylla machine developed earlier at Los Alamos.
By the mid-1960s progress had stalled across the world. All of the major designs were losing plasma at unsustainable rates. The 12-beam "4 pi laser" attempt at inertial confinement fusion developed at LLNL targeted a gas-filled target chamber of about 20 centimeters in diameter.
The magnetic mirror was first published in 1967 by Richard F. Post and many others at LLNL. The mirror consisted of two large magnets arranged so they had strong fields within them, and a weaker, but connected, field between them. Plasma introduced in the area between the two magnets would "bounce back" from the stronger fields in the middle.
A.D. Sakharov's group constructed the first tokamaks. The most successful were the T-3 and its larger version T-4. T-4 was tested in 1968 in Novosibirsk, producing the first quasistationary fusion reaction. When this was announced, the international community was skeptical. A British team was invited to see T-3, and confirmed the Soviet claims. A burst of activity followed as many planned devices were abandoned and tokamaks were introduced in their place—the C model stellarator, then under construction after many redesigns, was quickly converted to the Symmetrical Tokamak.
In his work with vacuum tubes, Philo Farnsworth observed that electric charge accumulated in the tube. In 1962, Farnsworth patented a design using a positive inner cage to concentrate plasma and fuse protons. During this time, Robert L. Hirsch joined Farnsworth Television labs and began work on what became the Farnsworth-Hirsch Fusor. This effect became known as the Multipactor effect. Hirsch patented the design in 1966 and published it in 1967.
Plasma temperatures of approximately 40 million degrees Celsius and 10 deuteron-deuteron fusion reactions per discharge were achieved at LANL with Scylla IV.
In 1968 the Soviets announced results from the T-3 tokamak, claiming temperatures an order of magnitude higher than any other device. A UK team, nicknamed "The Culham Five", confirmed the results. The results led many other teams, including the Princeton group, which converted their stellarator to a tokamak. | 0 | Theoretical and Fundamental Chemistry |
Arenediazonium cations undergo several reactions in which the group is replaced by another group or ion. Some of the major ones are the following. | 0 | Theoretical and Fundamental Chemistry |
Tetrafluoromethane, also known as carbon tetrafluoride or R-14, is the simplest perfluorocarbon (CF). As its IUPAC name indicates, tetrafluoromethane is the perfluorinated counterpart to the hydrocarbon methane. It can also be classified as a haloalkane or halomethane. Tetrafluoromethane is a useful refrigerant but also a potent greenhouse gas. It has a very high bond strength due to the nature of the carbon–fluorine bond. | 1 | Applied and Interdisciplinary Chemistry |
A primary metabolite is a kind of metabolite that is directly involved in normal growth, development, and reproduction. It usually performs a physiological function in the organism (i.e. an intrinsic function). A primary metabolite is typically present in many organisms or cells. It is also referred to as a central metabolite, which has an even more restricted meaning (present in any autonomously growing cell or organism). Some common examples of primary metabolites include: lactic acid, and certain amino acids. Note that primary metabolites do not show any pharmacological actions or effects.
Conversely, a secondary metabolite is not directly involved in those processes, but usually has an important ecological function (i.e. a relational function). A secondary metabolite is typically present in a taxonomically restricted set of organisms or cells (plants, fungi, bacteria, etc.). Some common examples of secondary metabolites include: ergot alkaloids, antibiotics, naphthalenes, nucleosides, phenazines, quinolines, terpenoids, peptides and growth factors.
Plant growth regulators may be classified as both primary and secondary metabolites due to their role in plant growth and development. Some of them are intermediates between primary and secondary metabolism. | 1 | Applied and Interdisciplinary Chemistry |
The existence of two distinct units with the same name was confusing, and the difference (about in relative terms) was large enough to affect high-precision measurements. Moreover, it was discovered that the isotopes of oxygen had different natural abundances in water and in air. For these and other reasons, in 1961 the International Union of Pure and Applied Chemistry (IUPAC), which had absorbed the ICAW, adopted a new definition of the atomic mass unit for use in both physics and chemistry; namely, of the mass of a carbon-12 atom. This new value was intermediate between the two earlier definitions, but closer to the one used by chemists (who would be affected the most by the change).
The new unit was named the "unified atomic mass unit" and given a new symbol "u", to replace the old "amu" that had been used for the oxygen-based units. However, the old symbol "amu" has sometimes been used, after 1961, to refer to the new unit, particularly in lay and preparatory contexts.
With this new definition, the standard atomic weight of carbon is about , and that of oxygen is about . These values, generally used in chemistry, are based on averages of many samples from Earth's crust, its atmosphere, and organic materials. | 0 | Theoretical and Fundamental Chemistry |
One of the most developed areas of phosphaalkyne chemistry is that of cycloadditions. Like other multiply bonded molecular fragments, phosphaalkynes undergo myriad reactions such as [1+2] cycloadditions, [3+2] cycloadditions, and [4+2] cycloadditions. This reactivity is summarized in graphical format below, which includes some examples of 1,2-addition reactivity (which is not a form of cycloaddition). | 0 | Theoretical and Fundamental Chemistry |
Described as "one of the more imaginative members" of the Organisation, McTaggart continued mineral chlorination studies and early in 1944, Ian Kraitzer joined the research group in what was to become the Minerals Utilization Section of the future CSIR Division of Industrial Chemistry (created 1959), and then by a young recruit, Isabel Joy Bear as a Junior Laboratory Assistant, and later by Charles Alsope, together seeking new uses for titanium tetrachloride. In the alkoxides of titanium, in particular the properties of polymerised butyl titanate, they discovered an excellent vehicle for heat-resisting paint pigments; it was a use of titanium esters that was patented by CSIR, a project in which the Defence laboratories joined Kraitzer and McTaggart s laboratory tests with paint formulation studies by Defence laboratories George Winter (who later joined the Division of Mineral Chemistry). After McTaggart presented an account of their findings in Paris and London, industrial firms in England and the USA were soon marketing the new paint, and its heat-resistance was still attracting attention as late as 1962, though with no acknowledgment of the Australian contribution.
McTaggart and Jean Lehmann married in 1944. After the war in 1947 and during a period of residency in Europe and the USA he worked with H J Emeléus in the chemistry labs in Cambridge, | 0 | Theoretical and Fundamental Chemistry |
Small amounts of fission products are naturally formed as the result of either spontaneous fission of natural uranium, which occurs at a low rate, or as a result of neutrons from radioactive decay or reactions with cosmic ray particles. The microscopic tracks left by these fission products in some natural minerals (mainly apatite and zircon) are used in fission track dating to provide the cooling (crystallization) ages of natural rocks. The technique has an effective dating range of 0.1 Ma to >1.0 Ga depending on the mineral used and the concentration of uranium in that mineral.
About 1.5 billion years ago in a uranium ore body in Africa, a natural nuclear fission reactor operated for a few hundred thousand years and produced approximately 5 tonnes of fission products. These fission products were important in providing proof that the natural reactor had occurred.
Fission products are produced in nuclear weapon explosions, with the amount depending on the type of weapon.
The largest source of fission products is from nuclear reactors. In current nuclear power reactors, about 3% of the uranium in the fuel is converted into fission products as a by-product of energy generation. Most of these fission products remain in the fuel unless there is fuel element failure or a nuclear accident, or the fuel is reprocessed. | 0 | Theoretical and Fundamental Chemistry |
Side effects reported for trandolapril include nausea, vomiting, diarrhea, headache, dry cough, dizziness or lightheadedness when sitting up or standing, hypotension, or fatigue. | 0 | Theoretical and Fundamental Chemistry |
Measurements of organic matter generally measure only organic compounds or carbon, and so are only an approximation of the level of once-living or decomposed matter. Some definitions of organic matter likewise only consider "organic matter" to refer to only the carbon content, or organic compounds, and do not consider the origins or decomposition of the matter. In this sense, not all organic compounds are created by living organisms, and living organisms do not only leave behind organic material. A clam's shell, for example, while biotic, does not contain much organic carbon, so may not be considered organic matter in this sense. Conversely, urea is one of many organic compounds that can be synthesized without any biological activity.
Organic matter is heterogeneous and very complex. Generally, organic matter, in terms of weight, is:
* 45–55% carbon
* 35–45% oxygen
* 3–5% hydrogen
* 1–4% nitrogen
The molecular weights of these compounds can vary drastically, depending on if they repolymerize or not, from 200 to 20,000 amu. Up to one third of the carbon present is in aromatic compounds in which the carbon atoms form usually six-membered rings. These rings are very stable due to resonance stabilization, so they are difficult to break down. The aromatic rings are also susceptible to electrophilic and nucleophilic attack from other electron-donating or electron-accepting material, which explains the possible polymerization to create larger molecules of organic matter.
There are also reactions that occur with organic matter and other material in the soil to create compounds never seen before. Unfortunately, it is very difficult to characterize these because so little is known about natural organic matter in the first place. Research is currently being done to figure out more about these new compounds and how many of them are being formed. | 0 | Theoretical and Fundamental Chemistry |
Bifunctional purine biosynthesis protein PURH is a protein that in humans is encoded by the ATIC gene.
ATIC encodes an enzyme which generates inosine monophosphate from aminoimidazole carboxamide ribonucleotide.
It has two functions:
* - 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase
* - IMP cyclohydrolase | 1 | Applied and Interdisciplinary Chemistry |
Historically, micro process engineering originated around the 1980s, when mechanical micromachining methods developed for the fabrication of uranium isotope separation nozzles were first applied to the manufacturing of compact heat exchangers at the Karlsruhe (Nuclear) Research Center. | 1 | Applied and Interdisciplinary Chemistry |
Waters from the modern Pacific and Southern ocean, typically observe an increase in Si/N ratio at intermediate depth, which results in an increase in opal export (~ increase in opal production). In the Southern Ocean and North Pacific, this relationship between opal export and Si/N ratio switches from linear to exponential for Si/N ratios greater than 2. This gradual increase in the importance of silicate (Si) relative to nitrogen (N) has tremendous consequences for the ocean biological production. The change in nutrient ratios contributes to select diatoms as main producers, compared to other (e.g., calcifying) organisms. For example, microcosm experiments have demonstrated that diatoms are DSi supercompetitors and dominate other producers above 2 μM DSi. Consequently, opal vs. carbonate export will be favored, resulting in increasing opal production. The Southern Ocean and the North Pacific also display maximum biogenic silicate/C flux ratios, and consist thus in an enrichment in biogenic silicate, compared to C export flux. This combined increase in opal preservation and export makes the Southern Ocean the most important sink for DSi today. | 1 | Applied and Interdisciplinary Chemistry |
Radiation is the evolutionary process of diversification of a single species into multiple forms. It includes the physiological and ecological diversity within a rapidly multiplying lineage. There are many types of radiation including adaptive, concordant, and discordant radiation however escape and radiate coevolution does not always follow those specific types.
Ehrlich and Raven's original paper did not clearly answer why ecological escape leads to increased diversification, however several explanations have been proposed. Once a novel defense has been acquired, the attacking organism which had evolved adaptations that allowed it to predate is now up against a new defense that it has not yet been evolved to encounter. This gives the defending organism the advantage, and therefore time to rapidly multiply unopposed by the previously attacking organism. This ultimately leads to the physiological and ecological diversity within the rapidly multiplying lineage, hence radiation. | 1 | Applied and Interdisciplinary Chemistry |
A feedwater heater is a power plant component used to pre-heat water delivered to a steam generating boiler. Preheating the feedwater reduces the irreversibilities involved in steam generation and therefore improves the thermodynamic efficiency of the system. This reduces plant operating costs and also helps to avoid thermal shock to the boiler metal when the feedwater is introduced back into the steam cycle.
In a steam power plant (usually modeled as a modified Rankine cycle), feedwater heaters allow the feedwater to be brought up to the saturation temperature very gradually. This minimizes the inevitable irreversibilities associated with heat transfer to the working fluid (water). See the article on the second law of thermodynamics for a further discussion of such irreversibilities. | 1 | Applied and Interdisciplinary Chemistry |
Opening of terminal epoxides by adventitious hydroxide may occur under the conditions of rearrangement; if this is not desired, anhydrous solvents, reagents, and glassware must be used. Freshly prepared sodium methoxide in methanol is commonly used to effect rearrangement without opening. Nucleophilic opening can be accomplished through the use of sodium azide, excess hydroxide, or cuprate reagents in the presence of lithium chloride. Electrophilic trapping is carried out under standard conditions in the presence of an electrophile such as benzyl bromide. Silyl halides have also been used as electrophilic trapping agents.
To prevent epoxide migration, weakly basic conditions may be employed. Neither aqueous potassium carbonate nor aqueous amine bases cause epoxide rearrangement. Low temperatures are also beneficial when epoxide migration is not desired. | 0 | Theoretical and Fundamental Chemistry |
The efficiency of the direct energy conversion in MHD power generation increases with the magnetic field strength and the plasma conductivity, which depends directly on the plasma temperature, and more precisely on the electron temperature. As very hot plasmas can only be used in pulsed MHD generators (for example using shock tubes) due to the fast thermal material erosion, it was envisaged to use nonthermal plasmas as working fluids in steady MHD generators, where only free electrons are heated a lot (10,000–20,000 kelvins) while the main gas (neutral atoms and ions) remains at a much lower temperature, typically 2500 kelvins. The goal was to preserve the materials of the generator (walls and electrodes) while improving the limited conductivity of such poor conductors to the same level as a plasma in thermodynamic equilibrium; i.e. completely heated to more than 10,000 kelvins, a temperature that no material could stand.
But Evgeny Velikhov first discovered theoretically in 1962 and experimentally in 1963 that an ionization instability, later called the Velikhov instability or electrothermal instability, quickly arises in any MHD converter using magnetized nonthermal plasmas with hot electrons, when a critical Hall parameter is reached, hence depending on the degree of ionization and the magnetic field. Such an instability greatly degrades the performance of nonequilibrium MHD generators. The prospects about this technology, which initially predicted awesome efficiencies, crippled MHD programs all over the world as no solution to mitigate the instability was found at that time.
Consequently, without implementing solutions to master the electrothermal instability, practical MHD generators had to limit the Hall parameter or use moderately heated thermal plasmas instead of cold plasmas with hot electrons, which severely lowers efficiency.
As of 1994, the 22% efficiency record for closed-cycle disc MHD generators was held by Tokyo Technical Institute. The peak enthalpy extraction in these experiments reached 30.2%. Typical open-cycle Hall & duct coal MHD generators are lower, near 17%. These efficiencies make MHD unattractive, by itself, for utility power generation, since conventional Rankine cycle power plants easily reach 40%.
However, the exhaust of an MHD generator burning fossil fuel is almost as hot as a flame. By routing its exhaust gases into a heat exchanger for a turbine Brayton cycle or steam generator Rankine cycle, MHD can convert fossil fuels into electricity with an estimated efficiency of up to 60 percent, compared to the 40 percent of a typical coal plant.
A magnetohydrodynamic generator might also be the first stage of a gas core reactor. | 1 | Applied and Interdisciplinary Chemistry |
The reverse transcriptase employs a "right hand" structure similar to that found in other viral nucleic acid polymerases. In addition to the transcription function, retroviral reverse transcriptases have a domain belonging to the RNase H family, which is vital to their replication. By degrading the RNA template, it allows the other strand of DNA to be synthesized. Some fragments from the digestion also serve as the primer for the DNA polymerase (either the same enzyme or a host protein), responsible for making the other (plus) strand. | 1 | Applied and Interdisciplinary Chemistry |
Nuclear magnetic resonance was first described and measured in molecular beams by Isidor Rabi in 1938, by extending the Stern–Gerlach experiment, and in 1944, Rabi was awarded the Nobel Prize in Physics for this work. In 1946, Felix Bloch and Edward Mills Purcell expanded the technique for use on liquids and solids, for which they shared the Nobel Prize in Physics in 1952.
Russell H. Varian filed the "Method and means for correlating nuclear properties of atoms and magnetic fields", on July 24, 1951. Varian Associates developed the first NMR unit called NMR HR-30 in 1952.
Purcell had worked on the development of radar during World War II at the Massachusetts Institute of Technology's Radiation Laboratory. His work during that project on the production and detection of radio frequency power and on the absorption of such RF power by matter laid the foundation for his discovery of NMR in bulk matter.
Rabi, Bloch, and Purcell observed that magnetic nuclei, like and , could absorb RF energy when placed in a magnetic field and when the RF was of a frequency specific to the identity of the nuclei. When this absorption occurs, the nucleus is described as being in resonance. Different atomic nuclei within a molecule resonate at different (radio) frequencies for the same magnetic field strength. The observation of such magnetic resonance frequencies of the nuclei present in a molecule makes it possible to determine essential chemical and structural information about the molecule.
The improvements of the NMR method benefited from the development of electromagnetic technology and advanced electronics and their introduction into civilian use. Originally as a research tool it was limited primarily to dynamic nuclear polarization, by the work of Anatole Abragam and Albert Overhauser, and to condensed matter physics, where it produced one of the first demonstrations of the validity of the BCS theory of superconductivity by the observation by Charles Slichter of the Hebel-Slichter effect. It soon showed its potential in organic chemistry, and by the 1990s improvement in the sensitivity and resolution of NMR spectroscopy resulted in its broader use in analytical chemistry, biochemistry and materials science.
In the 2020s zero- to ultralow-field nuclear magnetic resonance (ZULF NMR), a form of spectroscopy that provides abundant analytical results without the need for large magnetic fields, was developed. It is combined with a special technique that makes it possible to hyperpolarize atomic nuclei. | 0 | Theoretical and Fundamental Chemistry |
Trace heat cables may be connected to single-phase or (in groups) to three-phase power supplies. Power is controlled either by a contactor or a solid-state controller. For self-regulating cable, the supply must furnish a large warm-up current if the system is switched on from a cold starting condition. The contactor or controller may include a thermostat if accurate temperature maintenance is required, or may just shut off a freeze-protection system in mild weather.
Electrical heat tracing systems may be required to have earth leakage (ground fault or RCD) devices for personnel and equipment protection. The system design must minimize leakage current to prevent nuisance tripping; this may limit the length of any individual heating circuit. | 1 | Applied and Interdisciplinary Chemistry |
* R.J. Talling, R.J. Dashwood, M. Jackson, D. Dye, [https://www.sciencedirect.com/science/article/pii/S1359645408008082 On the mechanism of superelasticity in Gum metal], Acta Materialia, Volume 57, Issue 4, 2009, Pages 1188-1198, ISSN 1359-6454, doi: 10.1016/j.actamat.2008.11.013.
* N.G. Jones, R.J. Dashwood, M. Jackson, D. Dye, [https://www.sciencedirect.com/science/article/pii/S1359645409002559 β Phase decomposition in Ti–5Al–5Mo–5V–3Cr], Acta Materialia, Volume 57, Issue 13, 2009, Pages 3830-3839, ISSN 1359-6454, doi: 10.1016/j.actamat.2009.04.031.
* N.G. Jones, R.J. Dashwood, D. Dye, M. Jackson, [https://www.sciencedirect.com/science/article/pii/S0921509308001007 Thermomechanical processing of Ti–5Al–5Mo–5V–3Cr], Materials Science and Engineering: A, Volume 490, Issues 1–2, 2008, Pages 369-377, ISSN 0921-5093, doi: 10.1016/j.msea.2008.01.055.
* K.M. Rahman, V.A. Vorontsov, D. Dye, [https://www.sciencedirect.com/science/article/pii/S1359645415001081 The effect of grain size on the twin initiation stress in a TWIP steel], Acta Materialia, Volume 89, 2015, Pages 247-257, ISSN 1359-6454, doi: 10.1016/j.actamat.2015.02.008. | 1 | Applied and Interdisciplinary Chemistry |
A pyrometer, or radiation thermometer, is a type of remote sensing thermometer used to measure the temperature of distant objects. Various forms of pyrometers have historically existed. In the modern usage, it is a device that from a distance determines the temperature of a surface from the amount of the thermal radiation it emits, a process known as pyrometry, a type of radiometry.
The word pyrometer comes from the Greek word for fire, "πῦρ" (pyr), and meter, meaning to measure. The word pyrometer was originally coined to denote a device capable of measuring the temperature of an object by its incandescence, visible light emitted by a body which is at least red-hot. Infrared thermometers, can also measure the temperature of cooler objects, down to room temperature, by detecting their infrared radiation flux. Modern pyrometers are available for a wide range of wavelengths and are generally called radiation thermometers. | 1 | Applied and Interdisciplinary Chemistry |
Morse was elected a fellow of the American Association for the Advancement of Science in 1986. In 1997 she received the Garvan–Olin Medal for scientific accomplishments by a woman chemist from the American Chemical Society. In 2012 Western Washington University named the chemistry building the Karen W. Morse Hall in recognition of her. In 2021, Utah State University awarded her with an honorary doctorate. | 0 | Theoretical and Fundamental Chemistry |
Introductory chemistry uses postulates: the oxidation state for an element in a chemical formula is calculated from the overall charge and postulated oxidation states for all the other atoms.
A simple example is based on two postulates,
# OS = +1 for hydrogen
# OS = −2 for oxygen
where OS stands for oxidation state. This approach yields correct oxidation states in oxides and hydroxides of any single element, and in acids such as sulfuric acid () or dichromic acid (). Its coverage can be extended either by a list of exceptions or by assigning priority to the postulates. The latter works for hydrogen peroxide () where the priority of rule 1 leaves both oxygens with oxidation state −1.
Additional postulates and their ranking may expand the range of compounds to fit a textbook's scope. As an example, one postulatory algorithm from many possible; in a sequence of decreasing priority:
# An element in a free form has OS = 0.
# In a compound or ion, the sum of the oxidation states equals the total charge of the compound or ion.
# Fluorine in compounds has OS = −1; this extends to chlorine and bromine only when not bonded to a lighter halogen, oxygen or nitrogen.
# Group 1 and group 2 metals in compounds have OS = +1 and +2, respectively.
# Hydrogen has OS = +1 but adopts −1 when bonded as a hydride to metals or metalloids.
# Oxygen in compounds has OS = −2 but only when not bonded to oxygen (e.g. in peroxides) or fluorine.
This set of postulates covers oxidation states of fluorides, chlorides, bromides, oxides, hydroxides, and hydrides of any single element. It covers all oxoacids of any central atom (and all their fluoro-, chloro-, and bromo-relatives), as well as salts of such acids with group 1 and 2 metals. It also covers iodides, sulfides, and similar simple salts of these metals. | 0 | Theoretical and Fundamental Chemistry |
The ferric chloride test can be used to detect metabolites in urine in case of inborn error of metabolism such as phenylketonuria. Compounds such as phenylpyruvate increase in plasma and are excreted out via urine. Also, it can be used to detect salicylates in urine, quick diagnostic test for aspirin overdose. | 0 | Theoretical and Fundamental Chemistry |
There are a number of ways to measure ocean turbidity, including autonomous remote vehicles, shipcasts and satellites.
From a satellite, a proxy measurement of the water turbidity can be made by examining the amount of reflectance in the visible region of the electromagnetic spectrum. For the Advanced Very High Resolution Radiometer (AVHRR), the logical choice is band 1, covering wavelengths 580 to 680 nanometres, the orange and red. In order to make derived products that are comparable over time and space, an atmospheric correction is required. To do this, the effects of Rayleigh scattering are calculated based on the satellite viewing angle and the solar zenith angle and then subtracted from the band 1 radiance. For an aerosol correction, band 2 in the near infrared is used. It is first corrected for Rayleigh scattering and then subtracted from the Rayleigh corrected band 1. The Rayleigh corrected band 2 is assumed to be aerosol radiance because no return signal from water in the near infrared is expected since water is highly absorbing at those wavelengths. Because bands 1 and 2 are relatively close on the electromagnetic spectrum, we can reasonably assume their aerosol radiances are the same.
In these images the turbidity is quantified as the percent reflected light emerging from the water column in a range of 0 to 8 percent. The reflectance percentage can be correlated to attenuation, Secchi disk depth or total suspended solids although the exact relationship will vary regionally and depends on the optical properties of the water. For example, in Florida Bay, 10% reflectance corresponds to a sediment concentration of 30 milligram/litre and a Secchi depth of 0.5 metre. These relationships are approximately linear so that 5% reflectance would correspond to a sediment concentration of approximately 15 milligram/litre and a Secchi depth of 1 metre. In the Mississippi River plume regions these same reflectance values would represent sediment concentrations that are about ten times or more higher. | 0 | Theoretical and Fundamental Chemistry |
Corrosion engineering involves good design. Using a rounded edge rather than an acute edge reduces corrosion. Also not coupling by welding or other joining method, two dissimilar metals to avoid galvanic corrosion is best practice. Avoiding having a small anode (or anodic material) next to a large cathode (or cathodic material) is good practice. As an example, weld material should always be more noble than the surrounding material. Corrosion in ballast tanks on marine vessels can be an issue if good design is not undertaken. Other examples include simple design such as material thickness. In a known corrosion situation the material can just be made thicker so it will take much longer to corrode. | 1 | Applied and Interdisciplinary Chemistry |
Polyaniline nanofibers can also be synthesized through "rapid mixing" reactions. This method attempts to prevent overgrowth that would compromise the nanofiber nature of the polymer by stopping the polymerization immediately after nanofibers have been formed. This is achieved by the rapid mixing of the monomer, aniline, and an initiator solution. At the start of the reaction, the initiator is consumed rapidly and completely depleted when the nanofibers are formed. Without initiator remaining, the synthesis of polyaniline is halted. | 0 | Theoretical and Fundamental Chemistry |
CrysTBox is compiled to a stand-alone installers using MATLAB Compiler. Therefore, 1-2 GB of MATLAB libraries are installed together with the toolbox.
The diffraction simulation used in cellViewer is based on kinematic diffraction theory. This allows for a real-time response to user interaction, but it does not cover advanced diffraction features like double diffraction covered by dynamical diffraction theory, even though some phenomena caused by multiple electron-matter interactions are visualized by CrysTBox - for instance Kikuchi lines.
The analytical tools provide correction for scale calibration imperfections, but does not provide adjustment for image distortions such as elliptical distortion. If high-accuracy measurement is needed or if the distortion exceeds standard levels, appropriate tools should be applied prior to the analysis. | 0 | Theoretical and Fundamental Chemistry |
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula . It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly corrosive base and alkali that decomposes lipids and proteins at ambient temperatures and may cause severe chemical burns. It is highly soluble in water, and readily absorbs moisture and carbon dioxide from the air. It forms a series of hydrates . The monohydrate crystallizes from water solutions between 12.3 and 61.8 °C. The commercially available "sodium hydroxide" is often this monohydrate, and published data may refer to it instead of the anhydrous compound.
As one of the simplest hydroxides, sodium hydroxide is frequently used alongside neutral water and acidic hydrochloric acid to demonstrate the pH scale to chemistry students.
Sodium hydroxide is used in many industries: in the making of wood pulp and paper, textiles, drinking water, soaps and detergents, and as a drain cleaner. Worldwide production in 2004 was approximately 60 million tons, while demand was 51 million tons. | 0 | Theoretical and Fundamental Chemistry |
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