text stringlengths 105 4.57k | label int64 0 1 | label_text stringclasses 2
values |
|---|---|---|
Aside from virtually all saturated organic compounds, most compounds of Si, Ge, and Sn are tetrahedral. Often tetrahedral molecules feature multiple bonding to the outer ligands, as in xenon tetroxide (XeO), the perchlorate ion (), the sulfate ion (), the phosphate ion (). Thiazyl trifluoride () is tetrahedral, featuring a sulfur-to-nitrogen triple bond.
Other molecules have a tetrahedral arrangement of electron pairs around a central atom; for example ammonia () with the nitrogen atom surrounded by three hydrogens and one lone pair. However the usual classification considers only the bonded atoms and not the lone pair, so that ammonia is actually considered as pyramidal. The H–N–H angles are 107°, contracted from 109.5°. This difference is attributed to the influence of the lone pair which exerts a greater repulsive influence than a bonded atom. | 0 | Theoretical and Fundamental Chemistry |
* The two largest rivers in Australia, the Murray and its tributary the Darling, converge at Wentworth, New South Wales. | 1 | Applied and Interdisciplinary Chemistry |
In coordination chemistry, the S1cB (conjugate base) mechanism describes the pathway by which many metal amine complexes undergo substitution, that is, ligand exchange. Typically, the reaction entails reaction of a polyamino metal halide with aqueous base to give the corresponding polyamine metal hydroxide:
The rate law for the reaction is:
The rate law is deceptive: hydroxide serves not as a nucleophile but as a base to deprotonate the coordinated ammonia. Simultaneously with deprotonation, the halide dissociates. Water binds to the coordinatively unsaturated complex followed by proton transfer to give the hydroxy complex. The conjugate base resulting from deprotonation of the amine is rarely observed. | 0 | Theoretical and Fundamental Chemistry |
Monosaccharide nomenclature is the naming system of the building blocks of carbohydrates, the monosaccharides, which may be monomers or part of a larger polymer. Monosaccharides are subunits that cannot be further hydrolysed in to simpler units. Depending on the number of carbon atom they are further classified into trioses, tetroses, pentoses, hexoses etc., which is further classified in to aldoses and ketoses depending on the type of functional group present in them. | 0 | Theoretical and Fundamental Chemistry |
Excitation energy can be deposited in air by a number of different mechanisms:
* Ionizing radiation is the cause of blue glow surrounding sufficient quantities of strongly radioactive materials in air, e.g. some radioisotope specimens (e.g. radium or polonium), particle beams (e.g. from particle accelerators) in air, the blue flashes during criticality accidents, and the eerie/low brightness "purple" to "blue" glow enveloping the mushroom cloud during the first several dozen seconds after nuclear explosions near sea level. This post-explosion effect has been observed only at night from atmospheric nuclear tests owing to its low brightness, with observers noticing it following the pre-dawn Trinity nuclear test, as well as Upshot-Knothole Annie, Operation Fishbowl, and the Cherokee shot of Operation Redwing.
* Within minutes after the steam explosion that caused the Chernobyl accident at 01:23 local time, a number of employees at the power station went outside to get a clearer view of the extent of the damage. One such survivor, Alexander Yuvchenko, recounts that once he stopped outside and looked up towards the reactor hall he saw a "very beautiful" laser-like beam of light bluish light, caused by the ionization of air, that appeared to be "flooding up into infinity".
* Cathode rays in air produce this blue glow.
* Electrical discharge in air is the cause of blue light emitted by electric sparks, lightning, and corona discharges (e.g. St. Elmo's fire).
* Auroras, the sometimes observable blue-violet hues emitted by nitrogen at lower altitudes | 0 | Theoretical and Fundamental Chemistry |
The host recognition of bacteriophages occur via bacteria-binding proteins that have strong binding affinities to specific protein or carbohydrate structures on the surface of the bacterial host. At the end of the infection life cycle the bacteria-lysing Endolysin is synthesized and degrades the bacterial peptidoglycan cell wall, resulting in lysis (and therefore killing) of the bacterial cell. | 1 | Applied and Interdisciplinary Chemistry |
Substitutions can occur on the level of both the DNA and RNA. RNA editing-dependent amino acid substitutions can produce missense mRNA's of which occur through hydrolytic deaminase reactions. Two of the most prevalent deaminase reactions occur through the Apolipoprotein B mRNA editing enzyme (APOBEC) and the adenosine deaminase acting on RNA enzyme (ADAR) which are responsible for the conversion of cytidine to uridine (C-to-U), and the deamination of adenosine to inosine (A-to-I), respectively. Such selective substitutions of uridine for cytidine, and inosine for adenosine in RNA editing can produce differential isoforms of missense mRNA transcripts, and confer transcriptome diversity and enhanced protein function in response to selective pressures. | 1 | Applied and Interdisciplinary Chemistry |
The United States manufactured approximately 500,000 Geiger counters. Britain manufactured about 20,000 of each of its major types, and is second after the U.S. Some instruments were also manufactured by other countries in smaller numbers.
The American instruments dating from the Kennedy administration era were designed to use low voltage transistor electronics, and the batteries are still available today. However, most British civil defence instruments retained until 1982 or later were manufactured from 1953 to 1957, and required high voltage batteries which became obsolete after portable valve radios were superseded by transistor ones.
All British civil defence instruments were jointly designed by the Home Office and the Ministry of Defence, and were also a military issue. | 0 | Theoretical and Fundamental Chemistry |
In electrochemistry, CO stripping is a special process of voltammetry where a monolayer of carbon monoxide already adsorbed on the surface of an electrocatalyst is electrochemically oxidized and thus removed from the surface. A well-known process of this type is CO stripping on Pt/C electrocatalysts in which the electrooxidation peak occurs somewhere between 0.5 to 0.9 V depending on the characteristics and structural properties of the specimen. | 0 | Theoretical and Fundamental Chemistry |
CuHARS have been shown to completely degrade under physiological conditions (cell culture media at 37 °C), even in the absence of cells; this is possibly due to the metal chelating properties of typical cell culture medias. These may include the copper-binding properties of cerulosplasmin and of albumin. Additionally, CuHARS have been shown to polarize light using inverted microscopy. Cobalt-containing MOBs (CoMOBs) have been shown to be susceptible to an externally applied magnetic field as shown in Figure 2. | 0 | Theoretical and Fundamental Chemistry |
Numerous authors have claimed that willow was used by the ancients as a painkiller, but there is no evidence that this is true. All such accounts date from after the discovery of aspirin, and are possibly based on a misunderstanding of the chemistry. Bartrams 1998 Encyclopedia of Herbal Medicine is perhaps typical when it states, in 1838 chemists identified salicylic acid in the bark of White Willow. After many years, it was synthesised as acetylsalicylic acid, now known as aspirin.' It goes on to claim that willow extract has the same medical properties as aspirin, which is incorrect.
Ancient medical uses for willow were more varied. The Roman author Aulus Cornelius Celsus recommended using the leaves, pounded and boiled in vinegar, as treatment for uterine prolapse, but it is unclear what he considered the therapeutic action to be; it is unlikely to have been pain relief, as he recommended cauterization in the following paragraph (De Medicina, book VI, p. 287, chapter 18, section 10). Gerard quotes Dioscorides, that [the bark] being burnt to ashes, and steeped in vinegar, takes away corns and other like risings in the feet and toes, which is similar to modern uses of salicylic acid. Translations of Hippocrates make no mention of willow at all.
Nicholas Culpeper, in The Complete Herbal, gave many uses for willow, including to staunch wounds, to stay the heat of lust in man or woman, and to provoke urine (if stopped) but, like Celsus, made no mention of any analgesic properties. He also used the burnt ashes of willow bark, mixed with vinegar, to take away warts, corns, and superfluous flesh.
Although Turner (1551) thought that fevers could be cured by cooling the air with boughs and leaves of willow, the earliest known mention of willow bark extract for treating fever came in 1763, when a letter from English chaplain Edward Stone to the Royal Society described the dramatic power of powdered white willow bark to cure intermittent fevers, or ague. Stone had accidentally tasted the bark of a willow tree in 1758 and noticed an astringency reminiscent of Peruvian bark, which he knew was used to treat malaria. Over the next five years he treated some 50 ague sufferers, with universal success, except in a few severe cases, where it merely reduced their symptoms. Stone's remedy was trialled by a few pharmacists, but was never widely adopted. During the American Civil War, Confederate forces experimented with willow as a cure for malaria, without success. | 1 | Applied and Interdisciplinary Chemistry |
Lorber et al. found that at the outermost wing station, the existence of the tip vortex gives both the steady and unsteady lift and pitching moment hysteresis loops a more nonlinear quasi-steady behaviour due to an element of steady vortex-induced lift, while for the rest of the wing stations where oscillations below stall, there is no particular difference from 2-D cases. | 1 | Applied and Interdisciplinary Chemistry |
In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron. The bond angles are cos(−) = 109.4712206...° ≈ 109.5° when all four substituents are the same, as in methane () as well as its heavier analogues. Methane and other perfectly symmetrical tetrahedral molecules belong to point group T, but most tetrahedral molecules have lower symmetry. Tetrahedral molecules can be chiral. | 0 | Theoretical and Fundamental Chemistry |
In 1840, Claus, received a substantial amount of platinum ore samples for his studies from the Ural Mountains and the St Petersburg Mint and started working on chemistry and isolation of noble metals, in particular rhodium, iridium, osmium, and to a lesser extent, palladium and platinum. In 1844, he discovered a new chemical element, which he named ruthenium, after Ruthenia, the latinised name for Russia and the Latin name of Rus', by which Сlaus meant the Russian Empire and Russia in particular. Choosing the name for the new element, he stated: "I named the new body, in honour of my Motherland, ruthenium. I had every right to call it by this name because Mr. Osann relinquished his ruthenium and the word does not yet exist in chemistry."
Claus managed not only to isolate ruthenium, but also determine its atomic weight and chemical properties. He noted the similarity of the chemical properties of ruthenium, rhodium, palladium and platinum and meticulously documented his results. For this discovery, he was awarded the Demidov Prize of 5,000 rubles (which was of much financial help to his large family). He sent samples of new element for analysis to Jöns Jakob Berzelius, who was one of the most renowned scientists in the field of new elements, and thereby became known to European scientists. | 1 | Applied and Interdisciplinary Chemistry |
Cavity ring-down spectroscopy (CRDS) is a highly sensitive optical spectroscopic technique that enables measurement of absolute optical extinction by samples that scatter and absorb light. It has been widely used to study gaseous samples which absorb light at specific wavelengths, and in turn to determine mole fractions down to the parts per trillion level. The technique is also known as cavity ring-down laser absorption spectroscopy (CRLAS).
A typical CRDS setup consists of a laser that is used to illuminate a high-finesse optical cavity, which in its simplest form consists of two highly reflective mirrors. When the laser is in resonance with a cavity mode, intensity builds up in the cavity due to constructive interference. The laser is then turned off in order to allow the measurement of the exponentially decaying light intensity leaking from the cavity. During this decay, light is reflected back and forth thousands of times between the mirrors giving an effective path length for the extinction on the order of a few kilometers.
If a light-absorbing material is now placed in the cavity, the mean lifetime decreases as fewer bounces through the medium are required before the light is fully absorbed, or absorbed to some fraction of its initial intensity. A CRDS setup measures how long it takes for the light to decay to 1/e of its initial intensity, and this "ringdown time" can be used to calculate the concentration of the absorbing substance in the gas mixture in the cavity. | 0 | Theoretical and Fundamental Chemistry |
MALDI mass spectrometry is a laser-based soft-ionization method often used for analysis of large proteins, but has been used successfully for lipids. The lipid is mixed with a matrix, such as 2,5-dihydroxybenzoic acid, and applied to a sample holder as a small spot. A laser is fired at the spot, and the matrix absorbs the energy, which is then transferred to the analyte, resulting in ionization of the molecule. MALDI-Time-of-flight (MALDI-TOF) MS has become a very promising approach for lipidomics studies, particularly for the imaging of lipids from tissue slides. | 1 | Applied and Interdisciplinary Chemistry |
The compound hydrolyzes to hydrazoic acid:
The compound adds to ketones and aldehydes to give the siloxy azides and subsequently tetrazoles:
It ring-opens epoxides to give azido alcohols.
It has been used in the Oseltamivir total synthesis. | 0 | Theoretical and Fundamental Chemistry |
A dilatant (, ) (also termed shear thickening) material is one in which viscosity increases with the rate of shear strain. Such a shear thickening fluid, also known by the initialism STF, is an example of a non-Newtonian fluid. This behaviour is usually not observed in pure materials, but can occur in suspensions.
A dilatant is a non-Newtonian fluid where the shear viscosity increases with applied shear stress. This behavior is only one type of deviation from Newton's law of viscosity, and it is controlled by such factors as particle size, shape, and distribution. The properties of these suspensions depend on Hamaker theory and Van der Waals forces and can be stabilized electrostatically or sterically. Shear thickening behavior occurs when a colloidal suspension transitions from a stable state to a state of flocculation. A large portion of the properties of these systems are due to the surface chemistry of particles in dispersion, known as colloids.
This can readily be seen with a mixture of cornstarch and water (sometimes called oobleck), which acts in counterintuitive ways when struck or thrown against a surface. Sand that is completely soaked with water also behaves as a dilatant this is the reason why when walking on wet sand, a dry area appears directly underfoot.
Rheopecty is a similar property in which viscosity increases with cumulative stress or agitation over time. The opposite of a dilatant material is a pseudoplastic. | 1 | Applied and Interdisciplinary Chemistry |
In civil engineering, and in the earth sciences, flocculation is a condition in which clays, polymers or other small charged particles become attached and form a fragile structure, a floc. In dispersed clay slurries,
flocculation occurs after mechanical agitation ceases and the dispersed clay platelets spontaneously form flocs because of attractions between negative face charges and positive edge charges. | 1 | Applied and Interdisciplinary Chemistry |
Mitogen-activated protein kinase 3 (MAPK3) is also known as extracellular signal-regulated kinase 1 (ERK1). Transgenic gene knockout mice lacking MAPK3 are viable and it is thought that MAPK1 can fulfill some MAPK3 functions in most cells. The main exception is in T cells. Mice lacking MAPK3 have reduced T cell development past the CD4+ and CD8+ stage. | 1 | Applied and Interdisciplinary Chemistry |
Most hormones initiate a cellular response by initially binding to either cell surface receptors or intracellular receptors. A cell may have several different receptors that recognize the same hormone but activate different signal transduction pathways, or a cell may have several different receptors that recognize different hormones and activate the same biochemical pathway.
Receptors for most peptide as well as many eicosanoid hormones are embedded in the cell membrane as cell surface receptors, and the majority of these belong to the G protein-coupled receptor (GPCR) class of seven alpha helix transmembrane proteins. The interaction of hormone and receptor typically triggers a cascade of secondary effects within the cytoplasm of the cell, described as signal transduction, often involving phosphorylation or dephosphorylation of various other cytoplasmic proteins, changes in ion channel permeability, or increased concentrations of intracellular molecules that may act as secondary messengers (e.g., cyclic AMP). Some protein hormones also interact with intracellular receptors located in the cytoplasm or nucleus by an intracrine mechanism.
For steroid or thyroid hormones, their receptors are located inside the cell within the cytoplasm of the target cell. These receptors belong to the nuclear receptor family of ligand-activated transcription factors. To bind their receptors, these hormones must first cross the cell membrane. They can do so because they are lipid-soluble. The combined hormone-receptor complex then moves across the nuclear membrane into the nucleus of the cell, where it binds to specific DNA sequences, regulating the expression of certain genes, and thereby increasing the levels of the proteins encoded by these genes. However, it has been shown that not all steroid receptors are located inside the cell. Some are associated with the plasma membrane. | 1 | Applied and Interdisciplinary Chemistry |
An aqueous sample is treated with an equal volume of 1% strong base (sodium or potassium hydroxide) followed by a few drops of aqueous copper(II) sulfate. If the solution turns purple, it contains protein. 5–160 mg/mL can be determined. Peptides with the correct length of at least 3 amino acids are necessary for a significant, measurable colour shift with these reagents. | 0 | Theoretical and Fundamental Chemistry |
The limnology of the lake shows it contains approximately 280 million tons of dissolved salts, with the salinity varying depending upon the amount of water in the lake at any given time. Before 1941, average salinity was approximately 50 grams per liter (g/L) (compared to a value of 31.5 g/L for the world's oceans). In January 1982, when the lake reached its lowest level of , the salinity had nearly doubled to 99 g/L. In 2002, it was measured at 78 g/L and is expected to stabilize at an average 69 g/L as the lake replenishes over the next 20 years.
An unintended consequence of ending the water diversions was the onset of a period of "meromixis" in Mono Lake. In the time prior to this, Mono Lake was typically "monomictic"; which means that at least once each year the deeper waters and the shallower waters of the lake mixed thoroughly, thus bringing oxygen and other nutrients to the deep waters. In meromictic lakes, the deeper waters do not undergo this mixing; the deeper layers are more saline than the water near the surface, and are typically nearly devoid of oxygen. As a result, becoming meromictic greatly changes a lake's ecology.
Mono Lake has experienced meromictic periods in the past; this most recent episode of meromixis, brought on by the end of the water diversions, commenced in 1994 and had ended by 2004. | 1 | Applied and Interdisciplinary Chemistry |
The density of seawater controls much of the movement of water, or the thermohaline flow, in the ocean. The density of seawater is primarily determined by the temperature and salinity of that water. Changes in these two main parameters, potential temperature Θ and salinity S, are multiplied with their thermal expansion or haline contraction coefficient equal to each other; and are both proportional to a change in density and are both terms of the linearized equation of state of the ocean (TEOS-10). This similarity is supposed to be relevant for understanding the consequences of sea water mixing.
The density doesn't change over an isopycnal. However, by mixing a change in temperature and salinity can occur. Therefore spiciness is introduced as variable that is proportional to thermal expansion and haline contraction. Integration of this variable along an isopycnal leads to the following equation.
Spiciness could be described as the isothermal gradient of the density that equals the isohaline gradient of the density.
The isopycnal gradient of spiciness should equal to the isopycnal gradient of temperature and salinity by multiplication with the derivative in the other variable of the density.
Another mathematical implication for the existence of a spiciness influence manifests itself in a -diagram, where the negative slope of the isopleths equals the ratio between the temperature- and salinity derivative of the spiciness. | 0 | Theoretical and Fundamental Chemistry |
* Annual Review of Fluid Mechanics
* Journal of Fluid Mechanics
* Physics of Fluids
* Physical Review Fluids
* Experiments in Fluids
* European Journal of Mechanics B: Fluids
* Theoretical and Computational Fluid Dynamics
* Computers and Fluids
* International Journal for Numerical Methods in Fluids
* Flow, Turbulence and Combustion | 1 | Applied and Interdisciplinary Chemistry |
Enzymes used in decellularization treatments are used to break the bonds and interactions between nucleic acids, interacting cells through neighboring proteins, and other cellular components. Lipases, thermolysin, galactosidase, nucleases, and trypsin have all been used in the removal of cells. After a cell is lysed with a detergent, acid, physical pressure, etc., endonucleases and exonucleases can begin the degradation of the genetic material. Endonucleases cleave DNA and RNA in the middle of sequences. Benzoase, an endonuclease, produces multiple small nuclear fragments that can be further degraded and removed from the ECM scaffold. Exonucleases act at the end of DNA sequences to cleave the phosphodiester bonds and further degrade the nucleic acid sequences.
Enzymes such as trypsin act as proteases that cleave the interactions between proteins. Although trypsin can have adverse effects of collagen and elastin fibers of the ECM, using it in a time-sensitive manner controls any potential damage it could cause on the extracellular fibers. Dispase is used to prevent undesired aggregation of cells, which is beneficial in promoting their separating from the ECM scaffold. Experimentation has shown dispase to be most effective on the surface of a thin tissue, such as a lung in pulmonary tissue regeneration. To successfully remove deep cells of a tissue with dispase, mechanical agitation is often included in the process.
Collagenase is only used when the ECM scaffold product does not require an intact collagen structure. Lipases are commonly used when decellularized skin grafts are needed. Lipase acids function in decellularizing dermal tissues through delipidation and cleaving the interactions between heavily lipidized cells. The enzyme, α-galactosidase is a relevant treatment when removing the Gal epitope antigen from cell surfaces. | 1 | Applied and Interdisciplinary Chemistry |
* ASBMB Award for Exemplary Contributions to Education
* ASBMB Leadership Awards
* ASBMB–Merck Award
* ASBMB Young Investigator Award
* Avanti Award in Lipids
* Bert and Natalie Vallee Award in Biomedical Science
* DeLano Award for Computational Biosciences
* Earl and Thressa Stadtman Distinguished Scientist Award
* Earl and Thressa Stadtman Young Scholar Award
* Herbert Tabor Research Award
* Mildred Cohn Award in Biological Chemistry - The Mildred Cohn Award in Biological Chemistry was established in 2013 to honor the scientific achievements of Mildred Cohn. Cohn was the first female president of the society, in 1978. The award of $5,000 is presented annually to a scientist who has made substantial advances in understanding biological chemistry using innovative physical approaches. The recipient is expected to deliver the Mildred Cohn Award lecture at the annual meeting.
* Ruth Kirschstein Diversity in Science Award
* The Alice and C. C. Wang Award in Molecular Parasitology
* Walter A. Shaw Young Investigator Award in Lipid Research
* William C. Rose Award | 1 | Applied and Interdisciplinary Chemistry |
The Inglis–Teller equation represents an approximate relationship between the plasma density and the principal quantum number of the highest bound state of an atom. The equation was derived by [https://ahf.nuclearmuseum.org/ahf/profile/david-r-inglis/ David R. Inglis] and Edward Teller in 1939.
In a plasma, atomic levels are broadened and shifted due to the Stark effect, caused by electric microfields formed by the charged plasma particles (ions and electrons). The Stark broadening increases with the principal quantum number , while the energy separation between the nearby levels and decreases. Therefore, above a certain all levels become merged.
Assuming a neutral atomic radiator in a plasma consisting of singly charged ions (and neglecting the electrons), the equation reads
where is the ion particle density and is the Bohr radius.
The equation readily generalizes to cases of multiply charged plasma ions and/or charged radiator. Allowance for the effect of electrons is also possible, as was discussed already in the original study.
Spectroscopically, this phenomenon appears as discrete spectral lines merging into continuous spectrum. Therefore, by using the (appropriately generalized) Inglis–Teller equation it is possible to infer the density of laboratory and astrophysical plasmas. | 0 | Theoretical and Fundamental Chemistry |
In botany, a light curve shows the photosynthetic response of leaf tissue or algal communities to varying light intensities. The shape of the curve illustrates the principle of limiting factors; in low light levels, the rate of photosynthesis is limited by the concentration of chlorophyll and the efficiency of the light-dependent reactions, but in higher light levels it is limited by the efficiency of RuBisCo and the availability of carbon dioxide. The point on the curve where these two differing slopes meet is called the light saturation point and is where the light-dependent reactions are producing more ATP and NADPH than can be utilized by the light-independent reactions. Since photosynthesis is also limited by ambient carbon dioxide levels, light curves are often repeated at several different constant carbon dioxide concentrations. | 0 | Theoretical and Fundamental Chemistry |
The accuracy and precision of this method is supported largely by the confidence level of the results for appropriate liquid/solid combinations (as seen, for example, in fig 6). The Owens/Wendt theory is typically applicable to surfaces with low charge and moderate polarity. Some good examples are polymers that contain heteroatoms, such as PVC, polyurethanes, polyamides, polyesters, polyacrylates, and polycarbonates | 0 | Theoretical and Fundamental Chemistry |
High-energy (from 80 GeV to ~10 TeV) gamma rays arriving from far-distant quasars are used to estimate the extragalactic background light in the universe: The highest-energy rays interact more readily with the background light photons and thus the density of the background light may be estimated by analyzing the incoming gamma ray spectra. | 0 | Theoretical and Fundamental Chemistry |
Sulfur has long been known to contribute to damage. This is true for many materials such as metal corrosion, or concrete degradation. In King Lear, Shakespeare says: | 1 | Applied and Interdisciplinary Chemistry |
The stereoisomers β--glucopyranose and β--mannopyranose are epimers because they differ only in the stereochemistry at the C-2 position. The hydroxy group in β-D-glucopyranose is equatorial (in the "plane" of the ring), while in β-D-mannopyranose the C-2 hydroxy group is axial (up from the "plane" of the ring). These two molecules are epimers but, because they are not mirror images of each other, are not enantiomers. (Enantiomers have the same name, but differ in and classification.) They are also not sugar anomers, since it is not the anomeric carbon involved in the stereochemistry. Similarly, β--glucopyranose and β--galactopyranose are epimers that differ at the C-4 position, with the former being equatorial and the latter being axial.
In the case that the difference is the -OH groups on C-1, the anomeric carbon, such as in the case of α--glucopyranose and β--glucopyranose, the molecules are both epimers and anomers (as indicated by the α and β designation).
Other closely related compounds are epi-inositol and inositol and lipoxin and epilipoxin. | 0 | Theoretical and Fundamental Chemistry |
Darcys law is valid for laminar flow through sediments. In fine-grained sediments, the dimensions of interstices are small and thus flow is laminar. Coarse-grained sediments also behave similarly but in very coarse-grained sediments the flow may be turbulent. Hence Darcys law is not always valid in such sediments.
For flow through commercial circular pipes, the flow is laminar when Reynolds number is less than 2000 and turbulent when it is more than 4000, but in some sediments, it has been found that flow is laminar when the value of Reynolds number is less than 1. | 1 | Applied and Interdisciplinary Chemistry |
Living polymerization was first described by Michael Szwarc in 1956. It is defined as a chain polymerization from which chain transfer and chain termination are absent. In the absence of chain-transfer and chain termination, the monomer in the system is consumed and the polymerization stops but the polymer chain remains active. If new monomer is added, the polymerization can proceed.
Due to the low PDI and predictable molecular weight, living polymerization is at the forefront of polymer research. It can be further divided into living free radical polymerization, living ionic polymerization and living ring-opening metathesis polymerization, etc. | 0 | Theoretical and Fundamental Chemistry |
The magnetic properties of metal clusters are strongly influenced by their size and surface ligands. In general, the magnetic moments in small metal clusters are larger than in the case of a macroscopic bulk metal structure. For example, the average magnetic moment per atom in Ni clusters was found to be 0.7-0.8 μB, as compared with 0.6 μB for bulk Ni. This is explained by longer metal–metal bonds in cluster structures than in bulk structures, a consequence of a larger s character of metal–metal bonds in clusters. Magnetic moments approach bulk values as cluster size increases, though this is often difficult to predict computationally.
Magnetic quenching is an important phenomenon that is well documented for Ni clusters, and represents a significant effect of ligands on metal cluster magnetism. It has been shown that CO ligands cause the magnetic moments of surface Ni atoms to go to zero and the magnetic moment of inner Ni atoms to decrease to 0.5 μB. In this case, the 4s-derived Ni–Ni bonding molecular orbitals experience repulsion with the Ni-CO σ orbital, which causes its energy level to increase so that 3d-derived molecular orbitals are filled instead. Furthermore, Ni-CO π backbonding leaves Ni slightly positive, causing more transfer of electrons to 3d-derived orbitals, which are less disperse than those of 4s. Together, these effects result in a 3d, diamagnetic character of the ligated Ni atoms, and their magnetic moment decreases to zero.
Density functional theory (DFT) calculations have shown that these ligand-induced electronic effects are limited to only surface Ni atoms, and inner cluster atoms are virtually unperturbed. Experimental findings have described two electronically distinct cluster atoms, inner atoms and surface atoms. These results indicate the significant effect that a cluster's size has on its properties, magnetic and other. | 0 | Theoretical and Fundamental Chemistry |
Single Chain Cyclized/Knotted Polymers are a new class of polymer architecture with a general structure consisting of multiple intramolecular cyclization units within a single polymer chain. Such a structure was synthesized via the controlled polymerization of multivinyl monomers, which was first reported in Dr. Wenxin Wang's research lab. These multiple intramolecular cyclized/knotted units mimic the characteristics of complex knots found in proteins and DNA which provide some elasticity to these structures. Of note, 85% of elasticity in natural rubber is due to knot-like structures within its molecular chain. <br />
An intramolecular cyclization reaction is where the growing polymer chain reacts with a vinyl functional group on its own chain, rather than with another growing chain in the reaction system. In this way the growing polymer chain covalently links to itself in a fashion similar to that of a knot in a piece of string. As such, single chain cyclized/knotted polymers consist of many of these links (intramolecularly cyclized), as opposed to other polymer architectures including branched and crosslinked polymers that are formed by two or more polymer chains in combination.
Linear polymers can also fold into knotted topologies via non-covalent linkages. Knots and slipknots have been identified in naturally evolved polymers such as proteins as well. Circuit topology and knot theory formalise and classify such molecular conformations. | 0 | Theoretical and Fundamental Chemistry |
EQCM has been used to study the self-assembled monolayers of long chain alkyl mercaptan and alkanethiol and mercaptoalkanoic on gold electrode surface. | 0 | Theoretical and Fundamental Chemistry |
Even though quark-gluon plasma can only occur under quite extreme conditions of temperature and/or pressure, it is being actively studied at particle colliders, such as the Large Hadron Collider LHC at CERN and the Relativistic Heavy Ion Collider RHIC at Brookhaven National Laboratory.
In these collisions, the plasma only occurs for a very short time before it spontaneously disintegrates. The plasma's physical characteristics are studied by detecting the debris emanating from the collision region with large particle detectors
Heavy-ion collisions at very high energies can produce small short-lived regions of space whose energy density is comparable to that of the 20-micro-second-old universe. This has been achieved by colliding heavy nuclei such as lead nuclei at high speeds, and a first time claim of formation of quark–gluon plasma came from the SPS accelerator at CERN in February 2000.
This work has been continued at more powerful accelerators, such as RHIC in the US, and as of 2010 at the European LHC at CERN located in the border area of Switzerland and France. There is good evidence that the quark–gluon plasma has also been produced at RHIC. | 0 | Theoretical and Fundamental Chemistry |
In laboratory systems, either 10–30 mm beam diameter non-monochromatic Al K or Mg K anode radiation is used, or a focused 20-500 micrometer diameter beam single wavelength Al K monochromatised radiation. Monochromatic Al K X-rays are normally produced by diffracting and focusing a beam of non-monochromatic X-rays off of a thin disc of natural, crystalline quartz with a X-rays have an intrinsic full width at half maximum (FWHM) of 0.43 eV, centered on 1486.7 eV (E/ΔE = 3457). For a well–optimized monochromator, the energy width of the monochromated aluminum K X-rays is 0.16 eV, but energy broadening in common electron energy analyzers (spectrometers) produces an ultimate energy resolution on the order of FWHM=0.25 eV which, in effect, is the ultimate energy resolution of most commercial systems. When working under practical, everyday conditions, high energy-resolution settings will produce peak widths (FWHM) between 0.4 and 0.6 eV for various pure elements and some compounds. For example, in a spectrum obtained in 1 minute at a pass energy of 20 eV using monochromated aluminum K X-rays, the Ag 3d peak for a clean silver film or foil will typically have a FWHM of 0.45 eV. Non-monochromatic magnesium X-rays have a wavelength of 9.89 angstroms (0.989 nm) which corresponds to a photon energy of 1253 eV. The energy width of the non-monochromated X-ray is roughly 0.70 eV, which, in effect is the ultimate energy resolution of a system using non-monochromatic X-rays. Non-monochromatic X-ray sources do not use any crystals to diffract the X-rays which allows all primary X-rays lines and the full range of high-energy Bremsstrahlung X-rays (1–12 keV) to reach the surface. The ultimate energy resolution (FWHM) when using a non-monochromatic Mg K source is 0.9–1.0 eV, which includes some contribution from spectrometer-induced broadening. | 0 | Theoretical and Fundamental Chemistry |
Several countries had created their own nonproprietary naming system before the INN was created, and in many cases, the names created under the old systems continue to be used in those countries. As one example, in English the INN name for a common painkiller is paracetamol; the table below gives the alternative names for this in different systems: | 1 | Applied and Interdisciplinary Chemistry |
Environmental chemistry is used by the Environment Agency in England, Natural Resources Wales, the United States Environmental Protection Agency, the Association of Public Analysts, and other environmental agencies and research bodies around the world to detect and identify the nature and source of pollutants. These can include:
*Heavy metal contamination of land by industry. These can then be transported into water bodies and be taken up by living organisms.
*PAHs (Polycyclic Aromatic Hydrocarbon) in large bodies of water contaminated by oil spills or leaks. Many of the PAHs are carcinogens and are extremely toxic. They are regulated by concentration (ppb) using environmental chemistry and chromatography laboratory testing.
*Nutrients leaching from agricultural land into water courses, which can lead to algal blooms and eutrophication.
*Urban runoff of pollutants washing off impervious surfaces (roads, parking lots, and rooftops) during rain storms. Typical pollutants include gasoline, motor oil and other hydrocarbon compounds, metals, nutrients and sediment (soil).
*Organometallic compounds. | 1 | Applied and Interdisciplinary Chemistry |
Ultraviolet radiation can aggravate several skin conditions and diseases, including systemic lupus erythematosus, Sjögrens syndrome, Sinear Usher syndrome, rosacea, dermatomyositis, Dariers disease, Kindler–Weary syndrome and Porokeratosis. | 0 | Theoretical and Fundamental Chemistry |
Gene expression and RNA quantification studies have benefited from the increased precision and absolute quantification of dPCR. RNA quantification can be accomplished via RT-PCR, wherein RNA is reverse-transcribed into cDNA in the partitioned reaction itself, and the number of RNA molecules originating from each transcript (or allelic transcript) is quantified via dPCR.
One can often achieve greater sensitivity and precision by using dPCR rather than qPCR to quantify RNA molecules in part because it does not require use of a standard curve for quantification. dPCR is also more resilient to PCR inhibitors for the quantification of RNA than qPCR.
dPCR can detect and quantify more individual target species per detection channel than qPCR by virtue of being able to distinguish targets based on their differential fluorescence amplitude or by the use of distinctive color combinations for their detection. As an example of this, a 2-channel dPCR system has been used to detect in a single well the expression of four different splice variants of human telomerase reverse transcriptase, a protein that is more active in most tumor cells than in healthy cells. | 1 | Applied and Interdisciplinary Chemistry |
Soil vapor extraction (SVE) is a physical treatment process for in situ remediation of volatile contaminants in vadose zone (unsaturated) soils (EPA, 2012). SVE (also referred to as in situ soil venting or vacuum extraction) is based on mass transfer of contaminant from the solid (sorbed) and liquid (aqueous or non-aqueous) phases into the gas phase, with subsequent collection of the gas phase contamination at extraction wells. Extracted contaminant mass in the gas phase (and any condensed liquid phase) is treated in aboveground systems. In essence, SVE is the vadose zone equivalent of the pump-and-treat technology for groundwater remediation. SVE is particularly amenable to contaminants with higher Henry’s Law constants, including various chlorinated solvents and hydrocarbons. SVE is a well-demonstrated, mature remediation technology and has been identified by the U.S. Environmental Protection Agency (EPA) as presumptive remedy. | 1 | Applied and Interdisciplinary Chemistry |
The elementary reaction responsible for water quantification in the Karl Fischer titration is oxidation of sulfur dioxide () with iodine:
This elementary reaction consumes exactly one molar equivalent of water vs. iodine. Iodine is added to the solution until it is present in excess, marking the end point of the titration, which can be detected by potentiometry. The reaction is run in an alcohol solution containing a base, which consumes the sulfur trioxide and hydroiodic acid produced. | 0 | Theoretical and Fundamental Chemistry |
The fatty acid salts formed during production constitute the actual soap and are effective cleaners due to their surfactant properties. Using soap helps dissolve many water-insoluble substances, like fats and oils, making them washable with water.
In most cases, hard soaps or products based on them are used for handwashing because they exhibit an alkaline (pH value above 7) nature and can irritate the skin when in contact with mucous membranes. Hard soap has antiseptic qualities and can be used alongside warm water as a household remedy for paronychia. It's also used to shape dreadlocks.
In the realm of detergents, soaps are generally secondary due to the creation of soap scum. They are primarily utilized as defoamers.
Beyond cleaning, soaps also treat wood surfaces. They enhance the appearance of conifer woods, seal the wood's pores, minimize dirt accumulation, and prevent staining from fats or embedded dyes. For cleaning brushes, especially in oil painting, hard soap ensures extended durability of the bristles or hairs.
On occasion, water-based soap solutions are employed for pest control on cultivated plants, like against thrips and aphids. | 0 | Theoretical and Fundamental Chemistry |
A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays. With frequencies above 30 exahertz () and wavelength less than 10 picometer () gamma ray photons have the highest photon energy of any form of electromagnetic radiation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays based on their relatively strong penetration of matter; in 1900 he had already named two less penetrating types of decay radiation (discovered by Henri Becquerel) alpha rays and beta rays in ascending order of penetrating power.
Gamma rays from radioactive decay are in the energy range from a few kiloelectronvolts (keV) to approximately 8 megaelectronvolts (MeV), corresponding to the typical energy levels in nuclei with reasonably long lifetimes. The energy spectrum of gamma rays can be used to identify the decaying radionuclides using gamma spectroscopy. Very-high-energy gamma rays in the 100–1000 teraelectronvolt (TeV) range have been observed from sources such as the Cygnus X-3 microquasar.
Natural sources of gamma rays originating on Earth are mostly a result of radioactive decay and secondary radiation from atmospheric interactions with cosmic ray particles. However, there are other rare natural sources, such as terrestrial gamma-ray flashes, which produce gamma rays from electron action upon the nucleus. Notable artificial sources of gamma rays include fission, such as that which occurs in nuclear reactors, and high energy physics experiments, such as neutral pion decay and nuclear fusion.
Gamma rays and X-rays are both electromagnetic radiation, and since they overlap in the electromagnetic spectrum, the terminology varies between scientific disciplines. In some fields of physics, they are distinguished by their origin: Gamma rays are created by nuclear decay while X-rays originate outside the nucleus. In astrophysics, gamma rays are conventionally defined as having photon energies above 100 keV and are the subject of gamma ray astronomy, while radiation below 100 keV is classified as X-rays and is the subject of X-ray astronomy.
Gamma rays are ionizing radiation and are thus hazardous to life. They can cause DNA mutations, cancer and tumors, and at high doses burns and radiation sickness. Due to their high penetration power, they can damage bone marrow and internal organs. Unlike alpha and beta rays, they easily pass through the body and thus pose a formidable radiation protection challenge, requiring shielding made from dense materials such as lead or concrete. On Earth, the magnetosphere protects life from most types of lethal cosmic radiation other than gamma rays. | 0 | Theoretical and Fundamental Chemistry |
MPI-Marburg is scheduled to expand with a new [http://www.uni-marburg.de/synmikro/synmikro?set_language=en Department for Synthetic Microbiology (SYNMIKRO)], in collaboration with the Max Planck Society and the University of Marburg. The new department will serve as a research centre for SYNMIKRO with about 100 scientific positions expected to be made available. A grant of about 21 million Euro has been allocated for the period of 2010-12 alone. | 0 | Theoretical and Fundamental Chemistry |
As a successor to the HSEES program, ATSDR launched the National Toxic Substance Incidents Program (NTSIP) in 2009. One aspect of NTSIP is a national database of information related to chemical spills. NTSIP also has Assessment of Chemical Exposure teams to assist state and local health departments in the aftermath of toxic spills. These teams interview people who were exposed to the hazardous substances and collect samples to test the level of contamination in the environment and in people. | 1 | Applied and Interdisciplinary Chemistry |
There are two options for realizing apertureless NSOM-Raman technique: TERS and SERS. TERS is frequently used for apertureless NSOM-Raman and can significantly enhance the spatial resolution. This technique requires a metal tip to enhance the signal of the sample. That is why an AFM metal tip is usually used for enhancing the electric field for molecule excitation. Raman spectroscopy was combined with AFM in 1999. A very narrow aperture of the tip was required to obtain a relatively high spatial resolution; such aperture reduced the signal and was difficult to prepare. In 2000, Stȍckle et al. first designed a setup combining apertureless NSOM, Raman and AFM techniques, in which the tip had a 20 nm thick granular silver film on it. They reported a large gain in the Raman scattering intensity of a dye film (brilliant cresyl blue) deposited on a glass substrate if a metal-coated AFM tip was brought very close to the sample. About 2000-fold enhancement of Raman scattering and a spatial resolution of ~55 nm were achieved.
Similarly, Nieman et al. used an illuminated AFM tip coated with a 100 nm thick film of gold to enhance Raman scattering from polymers samples and achieved a resolution of 100 nm. In the early research of TERS, the most commonly used coating materials for the tip probe were silver and gold. High-resolution spatial maps of Raman signals were obtained with this technique from molecular films of such compounds as brilliant cresyl blue, malachite green isothiocyanate and rhodamine 6G, as well as individual carbon nanotubes. | 0 | Theoretical and Fundamental Chemistry |
A vacuum coffee maker operates as a siphon, where heating and cooling the lower vessel changes the vapor pressure of water in the lower, first pushing the water up into the upper vessel, then allowing the water to fall back down into the lower vessel.
Specifically, once the water in lower chamber is hot enough that its vapor pressure (the pressure exerted by the vapour component of a liquid) exceeds the pressure of a standard atmosphere, some of it begins to boil, turning into water vapor. Since the density of water vapor is about 1/2000 that of liquid water, the mixture of the air and water vapor in the lower chamber quickly expands, and, when the new pressure exceeds atmospheric pressure, pushes the remaining water up the siphon tube into the upper chamber, where it remains so long as the pressure difference between the upper and lower chambers is sufficient to support it (about 1.5 kPa or 0.015 atm). This pressure difference is maintained during brewing through the continuous heating of the lower chamber. Coffee grinds are added to the water in the upper chamber.
When the coffee has finished brewing, the heat is removed and the pressure in the bottom vessel drops, so the combined force of gravity and atmospheric pressure overcomes the pressure of the bottom chamber, causing the brewed coffee to be pulled into the bottom chamber of the vacuum coffee maker, leaving the coffee grounds in the top chamber.
The iconic Moka pot coffee maker functions on the same principle but the water is forced up from the bottom chamber through a third middle chamber containing the coffee grounds to the top chamber which has an air gap to prevent the brewed coffee from returning downwards. (Additionally, because the water is forced up through packed grounds, the pressures are greater.) The prepared coffee is then poured off from the top. | 1 | Applied and Interdisciplinary Chemistry |
Several different technological methods are available for carbon capture as demanded by the clean coal concept:
* Pre-combustion capture – This involves the gasification of a feedstock (such as coal) to form synthesis gas, which may be shifted to produce an and -rich gas mixture, from which the can be efficiently captured and separated, transported, and ultimately sequestered, This technology is usually associated with Integrated Gasification Combined Cycle process configurations.
* Post-combustion capture – This refers to capture of from exhaust gases of combustion processes.
* Oxy-fuel combustion – Fossil fuels such as coal are burned in a mixture of recirculated flue gas and oxygen, rather than in air, which largely eliminates nitrogen from the flue gas enabling efficient, low-cost capture.
The Kemper County IGCC Project, a proposed 582 MW coal gasification-based power plant, was expected to use pre-combustion capture of to capture 65% of the the plant produces, which would have been utilized and geologically sequestered in enhanced oil recovery operations. However, after many delays and a cost runup to $7.5 billion (triple the initial budget), the coal gasification project was abandoned and as of late 2017, Kemper is under construction as a cheaper natural gas power plant.
The Saskatchewan Government's Boundary Dam Integrated Carbon Capture and Sequestration Demonstration Project will use post-combustion, amine-based scrubber technology to capture 90% of the emitted by Unit 3 of the power plant; this will be pipelined to and utilized for enhanced oil recovery in the Weyburn oil fields.
An early example of a coal-based plant using (oxy-fuel) carbon-capture technology is Swedish company Vattenfall’s Schwarze Pumpe power station located in Spremberg, Germany, built by German firm Siemens, which went on-line in September 2008. The facility captures and acid rain producing pollutants, separates them, and compresses the into a liquid. Plans are to inject the into depleted natural gas fields or other geological formations. Vattenfall opines that this technology is considered not to be a final solution for reduction in the atmosphere, but provides an achievable solution in the near term while more desirable alternative solutions to power generation can be made economically practical.
Other examples of oxy-combustion carbon capture are in progress. Callide Power Station has retrofitted a 30-MWth existing PC-fired power plant to operate in oxy-fuel mode; in Ciuden, Spain, Endesa has a newly built 30-MWth oxy-fuel plant using circulating fluidized bed combustion (CFBC) technology. Babcock-ThermoEnergy's Zero Emission Boiler System (ZEBS) is oxy-combustion-based; this system features near 100% carbon-capture and according to company information virtually no air-emissions.
Other carbon capture and storage technologies include those that dewater low-rank coals. Low-rank coals often contain a higher level of moisture content which contains a lower energy content per tonne. This causes a reduced burning efficiency and an increased emissions output. Reduction of moisture from the coal prior to combustion can reduce emissions by up to 50 percent. | 1 | Applied and Interdisciplinary Chemistry |
A variational principle in physics, such as the principle of least action or Fermat's principle in optics, allows one to describe the system in a global manner and to solve it using the calculus of variations. In thermodynamics, such a principle would allow a Lagrangian formulation. The Gouy-Stodola theorem can be used as the basis for such a variational principle, in thermodynamics. It has been proven to satisfy the necessary conditions.
This is fundamentally different from most of the theorems other uses - here, it isnt being applied in order to locate components with irreversibilities or loss of exergy, but rather helps give some more general information about the system. | 0 | Theoretical and Fundamental Chemistry |
Hydroxylamine was first prepared as hydroxylammonium chloride in 1865 by the German chemist Wilhelm Clemens Lossen (1838-1906); he reacted tin and hydrochloric acid in the presence of ethyl nitrate. It was first prepared in pure form in 1891 by the Dutch chemist Lobry de Bruyn and by the French chemist Léon Maurice Crismer (1858-1944). The coordination complex (zinc dichloride di(hydroxylamine)), known as Crismer's salt, releases hydroxylamine upon heating. | 0 | Theoretical and Fundamental Chemistry |
A.J. Clark, FRS (1885–1941) held the established Chair of Pharmacology from 1918 to 1926. After qualifying in medicine, and serving as a field medical officer throughout the First World War, Clark had been appointed Professor of Pharmacology at the University of Cape Town where he remained until accepting the Chair of Pharmacology at UCL in 1920. His influence on the subject was profound. The distinguished physiologist and Nobel laureate A.V. Hill (Archibald Hill) had begun the quantitative study of the action of agonists on an isolated tissue (frog skeletal muscle) some years earlier. Clark took this much further and extended it to examine the actions of antagonists. The data he gathered on the exact relationship between agonist concentration and response, and on how this changed in the presence of a competitive antagonist, were published in two classic papers in the Journal of Physiology in 1926,. But he failed to work out a method for analysing properly the results of experiments with antagonists: that had to wait for his successor, Heinz Schild.
Nevertheless, Clark was largely responsible for the transition of pharmacology from a descriptive subject to the quantitative science that it is today - this emphasis on quantitative approaches has remained strong throughout the subsequent history of the department. Clarks book The Mode of Action of Drugs on Cells' (Williams & Wilkins, 1933) is a classic and the following quotation from it set the tone for the department for many years.
::"In the first place, there is no advantage in fitting curves by a formula unless this expresses some possible physico-chemical process, and it is undesirable to employ formulae that imply impossibilities. It is a question of finding a few systems so simple that it is possible to establish with reasonable probability the relation between the quantity of drug and the action produced."
While at UCL Clark wrote the first edition of his textbook Applied Pharmacology in 1923, a book that was to be updated by two of his successors as Head of department, first by H.O. Schild and later by H.P. Rang, and is still extant in the form of the widely used textbook Rang & Dales Pharmacology'.
In 1926 Clark followed his predecessor in moving to the University of Edinburgh. | 1 | Applied and Interdisciplinary Chemistry |
-Norpseudoephedrine, or (−)-norpseudoephedrine, is a psychostimulant drug of the amphetamine family. It is one of the four optical isomers of phenylpropanolamine, the other three being cathine ((+)-norpseudoephedrine), (−)-norephedrine, and (+)-norephedrine; as well as one of the two enantiomers of norpseudoephedrine (the other being cathine). Similarly to cathine, -norpseudoephedrine acts as a releasing agent of norepinephrine (EC = 30 nM) and to a lesser extent of dopamine (EC = 294 nM). Due to the 10-fold difference in its potency for inducing the release of the two neurotransmitters however, -norpseudoephedrine could be called a modestly selective or preferential norepinephrine releasing agent, similarly to related compounds like ephedrine and pseudoephedrine. | 0 | Theoretical and Fundamental Chemistry |
In 2017, General Fusion developed its plasma injector technology and Tri Alpha Energy constructed and operated its C-2U device. In August 2014, Phoenix Nuclear Labs announced the sale of a high-yield neutron generator that could sustain 5×10 deuterium fusion reactions per second over a 24-hour period.
In October 2014, Lockheed Martin's Skunk Works announced the development of a high beta fusion reactor, the Compact Fusion Reactor. Although the original concept was to build a 20-ton, container-sized unit, the team conceded in 2018 that the minimum scale would be 2,000 tons.
In January 2015, the polywell was presented at Microsoft Research. TAE Technologies announced that its Norman reactor had achieved plasma.
In 2017, Helion Energy's fifth-generation plasma machine went into operation, seeking to achieve plasma density of 20 T and fusion temperatures. ST40 generated "first plasma".
In 2018, Eni announced a $50 million investment in Commonwealth Fusion Systems, to attempt to commercialize ARC technology using a test reactor (SPARC) in collaboration with MIT. The reactor planned to employ yttrium barium copper oxide (YBCO) high-temperature superconducting magnet technology. Commonwealth Fusion Systems in 2021 tested successfully a 20 T magnet making it the strongest high-temperature superconducting magnet in the world. Following the 20 T magnet CFS raised $1.8 billion from private investors.
General Fusion began developing a 70% scale demo system. In 2018, TAE Technologies' reactor reached nearly 20 M°C. | 0 | Theoretical and Fundamental Chemistry |
Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a reaction occurs but in itself tells nothing about its rate. Chemical kinetics includes investigations of how experimental conditions influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition states, as well as the construction of mathematical models that also can describe the characteristics of a chemical reaction. | 0 | Theoretical and Fundamental Chemistry |
In 1922 Karamichailova graduated as a PhD in Physics and Mathematics. She wrote her thesis, entitled "About Electric Figures on Different Materials, Especially On Crystals" under the direction of Karl Przibram. Karamichailova continued her work at the Institute for Radium Studies afterwards, becoming particularly interested in radioluminescence. She cooperated with Marietta Blau in the study of polonium, and later researched methods for neutron bombardment of thorium. Karamichailova simultaneously attended courses in electronic and radio engineering at the Vienna Polytechnic. In the autumn of 1923 she returned briefly to Bulgaria and worked as a "guest fellow" at the Physics Institute of Sofia University. Soon Karamichailova went back to Vienna and began her work on the transmutation of light elements under alpha radiation at the Institute of Radium Studies. In 1931, Karamichailova and Marietta Blau observed a specific type of previously unknown radiation emitted from polonium, which would later be confirmed by James Chadwick as neutron radiation, leading to his discovery of neutrons.
In 1933 the position of "research assistant", under which she worked in Vienna, was terminated. Karamichailova had to continue her research without tuition until 1935, when she obtained a 3-year Alfred Yarrow Research Fellowship from Girton College, Cambridge. She was subsequently employed at the Cavendish Laboratory. In December 1937, she applied for a position as a docent in Experimental Physics at Sofia University. Karamichailova managed to extend her scholarship by 10 months, and finally returned to Bulgaria in 1939, where she was appointed as a docent of Experimental Atomistics with Radioactivity at SU. She set up an atomic physics course, introducing the latest knowledge from her studies in Austria and England and some of her equipment. The outbreak of World War II halted any further expansion of nuclear research activities.
Her studies now involved cosmic rays as well. Karamichailova used photographic plates to continue her work in this field, which she had collaborated on with Marietta Blau. She attempted to continue the study of multiple ionization, but this was impossible without the sophisticated equipment she had access to while in England. When Karamichailova began her work in Sofia in 1940, she only had a microscope and a dark room. | 0 | Theoretical and Fundamental Chemistry |
Permeable pavements are designed to replace Effective Impervious Areas (EIAs), but can be used, in some cases, to manage stormwater from other impervious surfaces on site. Use of this technique must be part of an overall on site management system for stormwater, and is not a replacement for other techniques.
During large storm events, the water table below the porous pavement can rise to a higher level, preventing the precipitation from being absorbed into the ground. Some additional water is stored in the open graded or crushed drain rock base, and remains until the subgrade can absorb the water. For clay-based soils, or other low to non-draining soils, it is important to increase the depth of the crushed drain rock base to allow additional capacity for the water as it waits to be infiltrated. | 1 | Applied and Interdisciplinary Chemistry |
The reaction between a ketone and ammonia results in an imine and byproduct water. This reaction is water sensitive and thus drying agents such as aluminum chloride or a Dean–Stark apparatus must be employed to remove water. The resulting imine will react and decompose back into the ketone and the ammonia when in the presence of water. This is due to the fact that this reaction is reversible: | 1 | Applied and Interdisciplinary Chemistry |
Thomas Charles Hope (21 July 1766 – 13 June 1844) was a Scottish physician, chemist and lecturer. He proved the existence of the element strontium, and gave his name to Hope's Experiment, which shows that water reaches its maximum density at .
In 1815 Hope was elected as president of the Royal College of Physicians of Edinburgh (1815–19), and as vice-president of Royal Society of Edinburgh (1823–33) during the presidencies of Walter Scott and Thomas Makdougall Brisbane.
Charles Darwin was one of Hope's students, and Darwin viewed his chemistry lectures as highlights in his otherwise largely dull education at the University. | 1 | Applied and Interdisciplinary Chemistry |
The metabolome refers to the complete set of small-molecule chemicals found within a biological sample. The biological sample can be a cell, a cellular organelle, an organ, a tissue, a tissue extract, a biofluid or an entire organism. The small molecule chemicals found in a given metabolome may include both endogenous metabolites that are naturally produced by an organism (such as amino acids, organic acids, nucleic acids, fatty acids, amines, sugars, vitamins, co-factors, pigments, antibiotics, etc.) as well as exogenous chemicals (such as drugs, environmental contaminants, food additives, toxins and other xenobiotics) that are not naturally produced by an organism.
In other words, there is both an endogenous metabolome and an exogenous metabolome. The endogenous metabolome can be further subdivided to include a "primary" and a "secondary" metabolome (particularly when referring to plant or microbial metabolomes). A primary metabolite is directly involved in the normal growth, development, and reproduction. A secondary metabolite is not directly involved in those processes, but usually has important ecological function. Secondary metabolites may include pigments, antibiotics or waste products derived from partially metabolized xenobiotics. The study of the metabolome is called metabolomics. | 1 | Applied and Interdisciplinary Chemistry |
Almost all functional transcripts are derived from known genes. The only exceptions are a small number of transcripts that might play a direct role in regulating gene expression near the prompters of known genes. (See Enhancer RNA.)
Gene occupy most of prokaryotic genomes so most of their genomes are transcribed. Many eukaryotic genomes are very large and known genes may take up only a fraction of the genome. In mammals, for example, known genes only account for 40-50% of the genome. Nevertheless, identified transcripts often map to a much larger fraction of the genome suggesting that the transcriptome contains spurious transcripts that do not come from genes. Some of these transcripipts are known to be non-functional because they map to transcribed pseudogenes or degenerative transposons and viruses. Others map to unidentified regions of the genome that may be junk DNA.
Spurious transcription is very common in eukaryotes, especially those with large genomes that might contain a lot of junk DNA. Some scientists claim that if a transcript has not been assigned to a known gene then the default assumption must be that it is junk RNA until it has been shown to be functional. This would mean that much of the transcriptome in species with large genomes is probably junk RNA. (See Non-coding RNA)
The transcriptome includes the transcripts of protein-coding genes (mRNA plus introns) as well as the transcripts of non-coding genes (functional RNAs plus introns).
*Ribosomal RNA/rRNA: Usually the most abundant RNA in the transcriptome.
*Long non-coding RNA/lncRNA: Non-coding RNA transcripts that are more than 200 nucleotides long. Members of this group comprise the largest fraction of the non-coding transcriptome other than introns. It is not known how many of these transcripts are functional and how many are junk RNA.
*transfer RNA/tRNA
*micro RNA/miRNA: 19-24 nucleotides (nt) long. Micro RNAs up- or downregulate expression levels of mRNAs by the process of RNA interference at the post-transcriptional level.
*small interfering RNA/siRNA: 20-24 nt
*small nucleolar RNA/snoRNA
*Piwi-interacting RNA/piRNA: 24-31 nt. They interact with Piwi proteins of the Argonaute family and have a function in targeting and cleaving transposons.
*enhancer RNA/eRNA: | 1 | Applied and Interdisciplinary Chemistry |
Metallic microlattice may find potential applications in thermal and vibration insulators such as shock absorbers, and may also prove useful as battery electrodes and catalyst supports. Additionally, the microlattices' ability to return to their original state after being compressed may make them suitable for use in spring-like energy storage devices. Automotive and aeronautical manufacturers are using microlattice technology to develop extremely lightweight and efficient structures that combine multiple functions, such as structural reinforcement and heat transfer, into single components for high-performance vehicles. | 0 | Theoretical and Fundamental Chemistry |
Numerous ion channels undergo palmitoylation, a lipid modification process. Moreover, a significant subset of ion channels demonstrate a direct affinity for cholesterol binding. The regulation of ion channels by cholesterol can stem from both direct binding interactions and an indirect influence, facilitated by the localization of palmitoylated residues within lipid rafts. It's important to note that these two mechanisms are not mutually exclusive; they can concurrently contribute to the modulation of ion channel activity and localization.
The spatial arrangement of an ion channel can profoundly impact its activation potential. Proposed mechanisms for this phenomenon encompass alterations in membrane thickness and the concentration of lipid molecules critical for signaling. One instance of this is observed in TREK-1 channels, which transition between lipid rafts and PIP2 domains, where they interact with an activating lipid. Similarly, Kir2.1 channels experience inhibition due to cholesterol while being activated by PIP2. Consequently, a transition from cholesterol-enriched GM1 to PIP2-rich domains is anticipated to trigger channel activation. Conversely, the scenario is opposite for nAChR, which responds positively to cholesterol, eliciting its activation. | 1 | Applied and Interdisciplinary Chemistry |
An electrocyclic reaction can either be classified as conrotatory or disrotatory based on the rotation at each end of the molecule. In conrotatory mode, both atomic orbitals of the end groups turn in the same direction (such as both atomic orbitals rotating clockwise or counter-clockwise). In disrotatory mode, the atomic orbitals of the end groups turn in opposite directions (one atomic orbital turns clockwise and the other counter-clockwise). The cis/trans geometry of the final product is directly decided by the difference between conrotation and disrotation.
Determining whether a particular reaction is conrotatory or disrotatory can be accomplished by examining the molecular orbitals of each molecule and through a set of rules. Only two pieces of information are required to determine conrotation or disrotation using the set of rules: how many electrons are in the pi-system and whether the reaction is induced by heat or by light. This set of rules can also be derived from an analysis of the molecular orbitals for predicting the stereochemistry of electrocyclic reactions. | 0 | Theoretical and Fundamental Chemistry |
Kinetic energy may be released during the course of a reaction (exothermic reaction) or kinetic energy may have to be supplied for the reaction to take place (endothermic reaction). This can be calculated by reference to a table of very accurate particle rest masses, as follows: according to the reference tables, the nucleus has a standard atomic weight of 6.015 atomic mass units (abbreviated u), the deuterium has 2.014 u, and the helium-4 nucleus has 4.0026 u. Thus:
* the sum of the rest mass of the individual nuclei = 6.015 + 2.014 = 8.029 u;
* the total rest mass on the two helium-nuclei = 2 × 4.0026 = 8.0052 u;
* missing rest mass = 8.029 – 8.0052 = 0.0238 atomic mass units.
In a nuclear reaction, the total (relativistic) energy is conserved. The "missing" rest mass must therefore reappear as kinetic energy released in the reaction; its source is the nuclear binding energy. Using Einsteins mass-energy equivalence formula E = mc', the amount of energy released can be determined. We first need the energy equivalent of one atomic mass unit:
Hence, the energy released is 0.0238 × 931 MeV = 22.2 MeV.
Expressed differently: the mass is reduced by 0.3%, corresponding to 0.3% of 90 PJ/kg is 270 TJ/kg.
This is a large amount of energy for a nuclear reaction; the amount is so high because the binding energy per nucleon of the helium-4 nucleus is unusually high because the He-4 nucleus is "doubly magic". (The He-4 nucleus is unusually stable and tightly bound for the same reason that the helium atom is inert: each pair of protons and neutrons in He-4 occupies a filled 1s nuclear orbital in the same way that the pair of electrons in the helium atom occupy a filled 1s electron orbital). Consequently, alpha particles appear frequently on the right-hand side of nuclear reactions.
The energy released in a nuclear reaction can appear mainly in one of three ways:
*kinetic energy of the product particles (fraction of the kinetic energy of the charged nuclear reaction products can be directly converted into electrostatic energy);
*emission of very high energy photons, called gamma rays;
*some energy may remain in the nucleus, as a metastable energy level.
When the product nucleus is metastable, this is indicated by placing an asterisk ("*") next to its atomic number. This energy is eventually released through nuclear decay.
A small amount of energy may also emerge in the form of X-rays. Generally, the product nucleus has a different atomic number, and thus the configuration of its electron shells is wrong. As the electrons rearrange themselves and drop to lower energy levels, internal transition X-rays (X-rays with precisely defined emission lines) may be emitted. | 0 | Theoretical and Fundamental Chemistry |
The first passive sampling devices were developed in the 1970s to determine concentrations of contaminants in the air. In 1980 this technology was first adapted for the monitoring of organic contaminants in water. The initial type of passive sampler developed for aquatic monitoring purposes was the semipermeable membrane device (SMPD). SPMD samplers are most effective at absorbing hydrophobic pollutants with an octanol-water partition coefficient (Kow) ranging from 4-8. As the global emission of bioconcentratable persistent organic pollutants (POPs) was shown to result in adverse ecological effects, industry developed a wide range of increasing water-soluble, polar hydrophilic organic compounds (HpOCs) to replace them. These compounds generally have lower bioconcentration factors. However, there is evidence that large fluxes of these HpOCs into aquatic environments may be responsible for a number of adverse effects to aquatic organisms, such as altered behavior, neurotoxicity, endocrine disruption, and impaired reproduction. In the late 1990s research was underway to develop a new passive sampler in order to monitor HpOCs with a log Kow value of less than 3. In 1999 the POCIS sampler was under development at the University of Missouri-Columbia. It gathered more support in the early 2000s as concern increased regarding the effects of pharmaceutical and personal care products in surface waters.
The United States Geological Survey (USGS) has been heavily involved in the development of passive samplers and has articles in their database regarding the development of POCIS as early as 2000. The USGS Columbia Environmental Research Center (CERC) is a self-proclaimed international leader in the field of passive sampling. There have been recent efforts by the USGS to connect people who have an interest in passive sampling. An international workshop and symposium on passive sampling was held by the USGS in 2013 to connect developers, policy makers and end users in order to discuss ways of monitoring environmental pollution. | 0 | Theoretical and Fundamental Chemistry |
Southern Research was founded in Birmingham, Alabama, on October 11, 1941, by Thomas Martin as the Alabama Research Institute.
Although Martin was named chairman of the newly chartered organization in December, 1941, activities were put on hold in the aftermath of the attack on Pearl Harbor and the beginning of US involvement in World War II. Two years later, in December 1943, with a promise of support from the Alabama Power Company, Martin reengaged the Alabama's industrial leaders and received over $100,000 in philanthropic donations.
Alabama Power Company pledged an additional US$15,000 per year for five years, $75,000 total, and this was enough for the organization to finance laboratory space and hire researchers and staff. The following year, 1944, the decision was made to change the institute's name from Alabama Research Institute, to Southern Research Institute.
Around this same time, Southern Research Institute hired its first director, Wilbur Lazier. Though he only stayed in this role for four years, Lazier is credited with recruiting many figures that shaped the history of the organization, including Howard E. Skipper.
Southern Research celebrated its 75th anniversary in October 2016. In celebration of this milestone the director of National Institutes of Health (NIH), Francis Collins, produced a video congratulating the organization on its anniversary. | 1 | Applied and Interdisciplinary Chemistry |
Tritium has an atomic mass of 3.01604928 u. Diatomic tritium ( or ) is a gas at standard temperature and pressure. Combined with oxygen, it forms a liquid called tritiated water ().
Compared to hydrogen in its natural composition on Earth, tritium has a higher melting point (20.62 K vs. 13.99 K), a higher boiling point (25.04 K vs. 20.27 K), a higher critical temperature (40.59 K vs. 32.94 K) and a higher critical pressure (1.8317 MPa vs. 1.2858 MPa).
Tritium's specific activity is .
Tritium figures prominently in studies of nuclear fusion because of its favorable reaction cross section and the large amount of energy (17.6 MeV) produced through its reaction with deuterium:
All atomic nuclei contain protons as their only electrically charged particles. They therefore repel one another because like charges repel. However, if the atoms have a high enough temperature and pressure (for example, in the core of the Sun), then their random motions can overcome such electrical repulsion (called the Coulomb force), and they can come close enough for the strong nuclear force to take effect, fusing them into heavier atoms.
The tritium nucleus, containing one proton and two neutrons, has the same charge as the nucleus of ordinary hydrogen, and it experiences the same electrostatic repulsive force when brought close to another atomic nucleus. However, the neutrons in the tritium nucleus increase the attractive strong nuclear force when brought close enough to another atomic nucleus. As a result, tritium can more easily fuse with other light atoms, compared with the ability of ordinary hydrogen to do so.
The same is true, albeit to a lesser extent, of deuterium. This is why brown dwarfs (so-called failed stars) cannot utilize ordinary hydrogen, but they do fuse the small minority of deuterium nuclei.
Like the other isotopes of hydrogen, tritium is difficult to confine. Rubber, plastic, and some kinds of steel are all somewhat permeable. This has raised concerns that if tritium were used in large quantities, in particular for fusion reactors, it might contribute to radioactive contamination, although its short half-life should prevent significant long-term accumulation in the atmosphere.
The high levels of atmospheric nuclear weapons testing that took place prior to the enactment of the Partial Nuclear Test Ban Treaty proved to be unexpectedly useful to oceanographers. The high levels of tritium oxide introduced into upper layers of the oceans have been used in the years since then to measure the rate of mixing of the upper layers of the oceans with their lower levels. | 0 | Theoretical and Fundamental Chemistry |
Flavin mononucleotide is a prosthetic group found in, among other proteins, NADH dehydrogenase, E.coli nitroreductase and old yellow enzyme. | 1 | Applied and Interdisciplinary Chemistry |
Bounded by impoundments (an impoundment is a dam), these dams typically use "local materials" including the tailings themselves, and may be considered embankment dams. Traditionally, the only option for tailings storage was to contain the tailings slurry with locally available earthen materials. This slurry is a dilute stream of the tailings solids within water that was sent to the tailings storage area. The modern tailings designer has a range of tailings products to choose from depending upon how much water is removed from the slurry prior to discharge. It is increasingly common for tailings storage facilities to require special barriers like Bituminous Geomembranes (BGMs) to contain liquid tailings slurries and prevent impact to the surrounding environment. The removal of water not only can create a better storage system in some cases (e.g. dry stacking, see below) but can also assist in water recovery which is a major issue as many mines are in arid regions. In a 1994 description of tailings impoundments, however, the U.S. EPA stated that dewatering methods may be prohibitively expensive except in special circumstances. Subaqueous storage of tailings has also been used.
Tailing ponds are areas of refused mining tailings where the waterborne refuse material is pumped into a pond to allow the sedimentation (meaning separation) of solids from the water. The pond is generally impounded with a dam, and known as tailings impoundments or tailings dams. It was estimated in 2000 that there were about 3,500 active tailings impoundments in the world. The ponded water is of some benefit as it minimizes fine tailings from being transported by wind into populated areas where the toxic chemicals could be potentially hazardous to human health; however, it is also harmful to the environment. Tailing ponds are often somewhat dangerous because they attract wildlife such as waterfowl or caribou as they appear to be a natural pond, but they can be highly toxic and harmful to the health of these animals. Tailings ponds are used to store the waste made from separating minerals from rocks, or the slurry produced from tar sands mining. Tailings are sometimes mixed with other materials such as bentonite to form a thicker slurry that slows the release of impacted water to the environment.
There are many different subsets of this method, including valley impoundments, ring dikes, in-pit impoundments, and specially dug pits. The most common is the valley pond, which takes advantage of the natural topographical depression in the ground. Large earthen dams may be constructed and then filled with the tailings. Exhausted open pit mines may be refilled with tailings. In all instances, due consideration must be made to contamination of the underlying water table, amongst other issues. Dewatering is an important part of pond storage, as the tailings are added to the storage facility the water is removed – usually by draining into decant tower structures. The water removed can thus be reused in the processing cycle. Once a storage facility is filled and completed, the surface can be covered with topsoil and revegetation commenced. However, unless a non-permeable capping method is used, water that infiltrates into the storage facility will have to be continually pumped out into the future. | 1 | Applied and Interdisciplinary Chemistry |
The same molecular-kinetic picture of a single component gas can also be applied to a gaseous mixture. For instance, in the Chapman–Enskog approach the viscosity of a binary mixture of gases can be written in terms of the individual component viscosities , their respective volume fractions, and the intermolecular interactions.
As for the single-component gas, the dependence of on the parameters of the intermolecular interactions enters through various collisional integrals which may not be expressible in closed form. To obtain usable expressions for which reasonably match experimental data, the collisional integrals may be computed numerically or from correlations. In some cases, the collision integrals are regarded as fitting parameters, and are fitted directly to experimental data. This is a common approach in the development of reference equations for gas-phase viscosities. An example of such a procedure is the Sutherland approach for the single-component gas, discussed above.
For gas mixtures consisting of simple molecules, Revised Enskog Theory has been shown to accurately represent both the density- and temperature dependence of the viscosity over a wide range of conditions. | 1 | Applied and Interdisciplinary Chemistry |
A fibrous protein forms long protein filaments, which are shaped like rods or wires. Fibrous proteins are structural or storage proteins that are typically inert and water-insoluble. A fibrous protein occurs as an aggregate due to hydrophobic side chains that protrude from the molecule.
A fibrous protein's peptide sequence often has limited residues with repeats; these can form unusual secondary structures, such as a collagen helix. The structures often feature cross-links between chains (e.g., cys-cys disulfide bonds between keratin chains).
Fibrous proteins tend not to denature as easily as globular proteins.
Miroshnikov et al. (1998) are among the researchers who have attempted to synthesize fibrous proteins. | 1 | Applied and Interdisciplinary Chemistry |
Historically, the modern idea of pharmacophore was popularized by Lemont Kier, who mentions the concept in 1967 and uses the term in a publication in 1971. Nevertheless, F. W. Shueler, in a 1960s book, uses the expression "pharmacophoric moiety" that corresponds to the modern concept.
The development of the concept is often erroneously accredited to Paul Ehrlich. However neither the alleged source nor any of his other works mention the term "pharmacophore" or make use of the concept. | 1 | Applied and Interdisciplinary Chemistry |
A study of non-medical use potential of eszopiclone found that in persons with a known history of non-medical benzodiazepine use, eszopiclone at doses of 6 and 12 mg produced effects similar to those of diazepam 20 mg. The study found that at these doses which are two or more times greater than the maximum recommended doses, a dose-related increase in reports of amnesia, sedation, sleepiness, and hallucinations was observed for both eszopiclone (Lunesta) as well as for diazepam (Valium). | 0 | Theoretical and Fundamental Chemistry |
The 6 of the 11 metabolic intermediates in reverse Krebs cycle promoted by Fe, Zn, and Cr in acidic conditions imply that protocells possibly emerged in locally metal-rich and acidic terrestrial hydrothermal fields. The acidic conditions are seemingly consistent with the stabilization of RNA. These hydrothermal fields would have exhibited cycling of freezing and thawing and a variety of temperature gradients that would promote nonenzymatic reactions of gluconeogenesis, nucleobase synthesis, nonenzymatic polymerization, and RNA replication. ATP synthesis and oxidation of ferrous iron via photochemical reactions or oxidants such as nitric oxide derived from lightning strikes, meteorite impacts, or volcanic emissions could have also occurred at hydrothermal fields.
Wet-dry cycling of hydrothermal fields would polymerize RNA and peptides, protocell aggregation in a moist gel phase during wet-dry cycling would allow diffusion of metabolic products across neighboring protocells. Protocell aggregation could be described as a primitive version of horizontal gene transfer. Fatty acid vesicles would be stabilized by polymers in the presence of Mg required for ribozyme activity. These prebiotic processes might have occurred in shaded areas that protect the emergence of early cellular life under ultraviolet irradiation. Long chain alcohols and monocarboxylic acids would have also been synthesized via Fischer–Tropsch synthesis. Hydrothermal fields would also have precipitates of transition metals and concentrated many elements including CHNOPS. Geothermal convection could also be a source of energy for the emergence of the proton motive force, phosphoryl group transfer, coupling between oxidation-reduction, and active transport. Its noted by David Deamer and Bruce Damer that these environments seemingly resemble Charles Darwins idea of a "warm little pond".
The problems with the hypothesis of a subaerial hydrothermal field of abiogenesis is that the proposed chemistry doesnt resemble known biochemical reactions. The abundance of subaerial hydrothermal fields would have been rare and offered no protection from either meteorites or ultraviolet irradiation. Clay minerals at subaerial hydrothermal fields would absorb organic reactants. Pyrophosphate has low solubility in water and cant be phosphorylated without a phosphorylating agent. It doesn't offer explanations for the origin of chemiosmosis and differences between Archaea and Bacteria. | 1 | Applied and Interdisciplinary Chemistry |
In drug development, preclinical development (also termed preclinical studies or nonclinical studies) is a stage of research that begins before clinical trials (testing in humans) and during which important feasibility, iterative testing and drug safety data are collected, typically in laboratory animals.
The main goals of preclinical studies are to determine a starting, safe dose for first-in-human study and assess potential toxicity of the product, which typically include new medical devices, prescription drugs, and diagnostics.
Companies use stylized statistics to illustrate the risks in preclinical research, such as that on average, only one in every 5,000 compounds that enters drug discovery to the stage of preclinical development becomes an approved drug. | 1 | Applied and Interdisciplinary Chemistry |
The translational invariance of a crystal lattice is described by a set of unit cell, direct lattice basis vectors (contravariant or polar) called a, b, and c, or equivalently by the lattice parameters, i.e. the magnitudes of the vectors, called a, b and c, and the angles between them, called α (between b and c), β (between c and a), and γ (between a and b). Direct lattice vectors have components measured in distance units, like meters (m) or angstroms (Å).
A lattice vector is indexed by its coordinates in the direct lattice basis system and is generally placed between square brackets []. Thus a direct lattice vector , or , is defined as . Angle brackets ⟨⟩ are used to refer to a symmetrically equivalent class of lattice vectors (i.e. the set of vectors generated by an action of the lattice's symmetry group). In the case of a cubic lattice, for instance, ⟨100⟩ represents [100], [010], [001], [00], [00] and [00] because each of these vectors is symmetrically equivalent under a 90 degree rotation along an axis. A bar over a coordinate is equivalent to a negative sign (e.g., ).
The term "zone axis" more specifically refers to the direction of a direct-space lattice vector. For example, since the [120] and [240] lattice vectors are parallel, their orientations both correspond the ⟨120⟩ zone of the crystal. Just as a set of lattice planes in direct space corresponds to a reciprocal lattice vector in the complementary space of spatial frequencies and momenta, a "zone" is defined as a set of reciprocal lattice planes in frequency space that corresponds to a lattice vector in direct space.
The reciprocal space analog to a zone axis is a "lattice plane normal" or "g-vector direction". Reciprocal lattice vectors (one-form or axial) are Miller-indexed using coordinates in the reciprocal lattice basis instead, generally between round brackets () (similar to square brackets [] for direct lattice vectors). Curly brackets {} (not to be confused with a mathematical set) are used to refer to a symmetrically equivalent class of reciprocal lattice vectors, similar to angle brackets ⟨⟩ for classes of direct lattice vectors.
Here, , , and , where the unit cell volume is ( denotes a dot product and a cross product). Thus a reciprocal lattice vector or has a direction perpendicular to a crystallographic plane and a magnitude equal to the reciprocal of the spacing between those planes, measured in spatial frequency units, e.g. of cycles per angstrom (cycles/Å).
A useful and quite general rule of crystallographic "dual vector spaces in 3D", e.g. reciprocal lattices, is that the condition for a direct lattice vector [uvw] (or zone axis) to be perpendicular to a reciprocal lattice vector (hkl) can be written with a dot product as . This is true even if, as is often the case, the basis vector set used to describe the lattice is not Cartesian. | 0 | Theoretical and Fundamental Chemistry |
It is known that most materials are polycrystalline and contain grain boundaries and that grain boundaries can act as sinks and transport pathways for point defects. However experimentally and theoretically determining what effect point defects have on a system is difficult. Interesting examples of the complications of how point defects behave has been manifested in the temperature dependence of the Seebeck effect. In addition the dielectric and piezoelectric response can be altered by the distribution of point defects near grain boundaries. Mechanical properties can also be significantly influenced with properties such as the bulk modulus and damping being influenced by changes to the distribution of point defects within a material. It has also been found that the Kondo effect within graphene can be tuned due to a complex relationship between grain boundaries and point defects. Recent theoretical calculations have revealed that point defects can be extremely favourable near certain grain boundary types and significantly affect the electronic properties with a reduction in the band gap. | 1 | Applied and Interdisciplinary Chemistry |
Other photoinitiated free radical polymerization reactions can also be used for fiber production. In this case, the shealth fluid was only used to separate the core fluid from the tube wall. Also, to achieve the solidification rapid enough, a more concentrated monomer solution was usually used.
An example would be the production of 4-hydroxybutyl acrylate fiber reported by Beebe et al. The microfluid device they used was built with ethylvinyl acetate caplliary and PDMS rubber. The core fluid was a mixture of [https://pubchem.ncbi.nlm.nih.gov/compound/75588 4-hydroxybutyl acrylate], acrylic acid, ethyleneglycol dimethacrylate (crosslinker), [https://www.chemicalbook.com/ChemicalProductProperty_EN_CB0439891.htm 2,2′-dimethoxy-2-phenyl-acetonephenone] (photoinitiator). The sheath fluid was only for separation. The crosslinked network was formed by free radical polymerization when the UV light met the core fluid. | 0 | Theoretical and Fundamental Chemistry |
The Müllerian strategy is usually contrasted with Batesian mimicry, in which one harmless species adopts the appearance of an unprofitable species to gain the advantage of predators avoidance; Batesian mimicry is thus in a sense parasitic on the models defences, whereas Müllerian is to mutual benefit. However, because comimics may have differing degrees of protection, the distinction between Müllerian and Batesian mimicry is not absolute, and there can be said to be a spectrum between the two forms.
Viceroy butterflies and monarchs (types of admiral butterfly) are both poisonous Müllerian mimics, though they were long thought to be Batesian. Mitochondrial DNA analysis of admiral butterflies shows that the viceroy is the basal lineage of two western sister species in North America. The variation in wing patterns appears to have preceded the evolution of toxicity, while other species remain non-toxic, refuting the hypothesis that the toxicity of these butterflies is a conserved characteristic from a common ancestor. | 1 | Applied and Interdisciplinary Chemistry |
If Z is a state function then the balance of Z remains unchanged during a cyclic process:
Entropy is a state function and is defined in an absolute sense through the Third Law of Thermodynamics as
where a reversible path is chosen from absolute zero to the final state, so that for an isothermal reversible process
In general, for any cyclic process the state points can be connected by reversible paths, so that
meaning that the net entropy change of the working fluid over a cycle is zero. | 0 | Theoretical and Fundamental Chemistry |
Atmospheric nuclear weapons tests in isolated areas often resulted in doses of less than 1 mSv to any individual. All the thousands of atmospheric tests that occurred in the 20th century together now cause a 30,000 man-Sv collective dose each year from fallout. The annual dose reduces each year. | 0 | Theoretical and Fundamental Chemistry |
The seeding particles are an inherently critical component of the PIV system. Depending on the fluid under investigation, the particles must be able to match the fluid properties reasonably well. Otherwise they will not follow the flow satisfactorily enough for the PIV analysis to be considered accurate. Ideal particles will have the same density as the fluid system being used, and are spherical (these particles are called microspheres). While the actual particle choice is dependent on the nature of the fluid, generally for macro PIV investigations they are glass beads, polystyrene, polyethylene, aluminum flakes or oil droplets (if the fluid under investigation is a gas). Refractive index for the seeding particles should be different from the fluid which they are seeding, so that the laser sheet incident on the fluid flow will reflect off of the particles and be scattered towards the camera.
The particles are typically of a diameter in the order of 10 to 100 micrometers. As for sizing, the particles should be small enough so that response time of the particles to the motion of the fluid is reasonably short to accurately follow the flow, yet large enough to scatter a significant quantity of the incident laser light. For some experiments involving combustion, seeding particle size may be smaller, in the order of 1 micrometer, to avoid the quenching effect that the inert particles may have on flames. Due to the small size of the particles, the particles motion is dominated by Stokes drag and settling or rising effects. In a model where particles are modeled as spherical (microspheres) at a very low Reynolds number, the ability of the particles to follow the fluids flow is inversely proportional to the difference in density between the particles and the fluid, and also inversely proportional to the square of their diameter. The scattered light from the particles is dominated by Mie scattering and so is also proportional to the square of the particles diameters. Thus the particle size needs to be balanced to scatter enough light to accurately visualize all particles within the laser sheet plane, but small enough to accurately follow the flow.
The seeding mechanism needs to also be designed so as to seed the flow to a sufficient degree without overly disturbing the flow. | 1 | Applied and Interdisciplinary Chemistry |
Kāla is a real entity according to Jainism and is said to be the cause of continuity and succession. Champat Rai Jain in his book "The Key of Knowledge wrote: Jaina philosophers call the substance of Time as Niścay Time to distinguish it from vyavhāra (practical) Time which is a measure of duration- hours, days and the like. | 1 | Applied and Interdisciplinary Chemistry |
RNA splicing is the process by which introns, regions of RNA that do not code for proteins, are removed from the pre-mRNA and the remaining exons connected to re-form a single continuous molecule. Exons are sections of mRNA which become "expressed" or translated into a protein. They are the coding portions of a mRNA molecule. Although most RNA splicing occurs after the complete synthesis and end-capping of the pre-mRNA, transcripts with many exons can be spliced co-transcriptionally. The splicing reaction is catalyzed by a large protein complex called the spliceosome assembled from proteins and small nuclear RNA molecules that recognize splice sites in the pre-mRNA sequence. Many pre-mRNAs, including those encoding antibodies, can be spliced in multiple ways to produce different mature mRNAs that encode different protein sequences. This process is known as alternative splicing, and allows production of a large variety of proteins from a limited amount of DNA. | 1 | Applied and Interdisciplinary Chemistry |
In most conventional activated sludge processes or aerobic granular reactor, the microorganisms grow in flocs. Flocs are defined as a mass of microorganisms that are held together by slime or fungal filaments, which help with aerobic decomposition and trapping particles (et al. Wilen). Activated sludges are built with two physical separate tanks. One tank is specifically designed for aeration, where biological reactions happen. The second tank or the “settling tank” is where treated water is separated from flocculation. This is the most important part because the biomass is in the form of the flocculent sludge, which consists of extracellular polymeric substances. There are some downfalls to using a conventional AGS system because they tend to have low biomass in the aeration tank and settling tank. | 1 | Applied and Interdisciplinary Chemistry |
In physics, transport phenomena are all irreversible processes of statistical nature stemming from the random continuous motion of molecules, mostly observed in fluids. Every aspect of transport phenomena is grounded in two primary concepts : the conservation laws, and the constitutive equations. The conservation laws, which in the context of transport phenomena are formulated as continuity equations, describe how the quantity being studied must be conserved. The constitutive equations describe how the quantity in question responds to various stimuli via transport. Prominent examples include Fouriers law of heat conduction and the Navier–Stokes equations, which describe, respectively, the response of heat flux to temperature gradients and the relationship between fluid flux and the forces applied to the fluid. These equations also demonstrate the deep connection between transport phenomena and thermodynamics, a connection that explains why transport phenomena are irreversible. Almost all of these physical phenomena ultimately involve systems seeking their lowest energy state in keeping with the principle of minimum energy. As they approach this state, they tend to achieve true thermodynamic equilibrium, at which point there are no longer any driving forces in the system and transport ceases. The various aspects of such equilibrium are directly connected to a specific transport: heat transfer is the systems attempt to achieve thermal equilibrium with its environment, just as mass and momentum transport move the system towards chemical and mechanical equilibrium.
Examples of transport processes include heat conduction (energy transfer), fluid flow (momentum transfer), molecular diffusion (mass transfer), radiation and electric charge transfer in semiconductors.
Transport phenomena have wide application. For example, in solid state physics, the motion and interaction of electrons, holes and phonons are studied under "transport phenomena". Another example is in biomedical engineering, where some transport phenomena of interest are thermoregulation, perfusion, and microfluidics. In chemical engineering, transport phenomena are studied in reactor design, analysis of molecular or diffusive transport mechanisms, and metallurgy.
The transport of mass, energy, and momentum can be affected by the presence of external sources:
* An odor dissipates more slowly (and may intensify) when the source of the odor remains present.
* The rate of cooling of a solid that is conducting heat depends on whether a heat source is applied.
* The gravitational force acting on a rain drop counteracts the resistance or drag imparted by the surrounding air. | 1 | Applied and Interdisciplinary Chemistry |
In 2003 English Nature concluded that in the UK policy makers have largely ignored green roofs. However, British examples can be found with increasing frequency. The Kensington Roof Gardens are a notable early roof garden which was built above the former Derry & Toms department store in Kensington, London in 1938. More recent examples can be found at the University of Nottingham Jubilee Campus, and in London at Sainsburys Millennium Store in Greenwich, the Horniman Museum and at Canary Wharf. The Ethelred Estate, close to the River Thames in central London, is the British capitals largest roof-greening project to date. Toxteth in Liverpool is also a candidate for a major roof-greening project.
In the United Kingdom, intensive green roofs are sometimes used in built-up city areas where residents and workers often do not have access to gardens or local parks. Extensive green roofs are sometimes used to blend buildings into rural surroundings, for example by Rolls-Royce Motor Cars, who has one of the biggest green roofs in Europe (covering more than on their factory at Goodwood, West Sussex.
The University of Sheffield has created a Green Roof Centre of Excellence and conducted research, particularly in a UK context, into green roofs. Nigel Dunnett of Sheffield University published a UK-centric book about green roofing in 2004 (updated 2008).
Fort Dunlop has the largest green roof in the UK since its redevelopment between 2004 and 2006.
The UK also has one of the most innovative food preparation facilities in Europe, the Kanes salad factory in Evesham. It is topped with a wildflower roof featuring nearly 90 species of wildflower and natural grasses. The seed mix was prepared in consultation with leading ecologists to try to minimise the impact on the local environment. The pre-grown wildflower blanket sits on top of a standing seam roof and is combined with solar panels to create an eco-friendly finish to the entire factory. The development also won the 2013 National Federation of Roofing Contractors Sustainable Roof Award for Green Roofing. | 1 | Applied and Interdisciplinary Chemistry |
Human health effects include excess nitrate in drinking water (blue baby syndrome); disinfection by-products in drinking water. Swimming in water affected by a harmful algal bloom can cause skin rashes and respiratory problems. | 1 | Applied and Interdisciplinary Chemistry |
Imines are typically prepared by the condensation of primary amines and aldehydes. Ketones undergo similar reactions, but less commonly than aldehydes. In terms of mechanism, such reactions proceed via the nucleophilic addition giving a hemiaminal -C(OH)(NHR)- intermediate, followed by an elimination of water to yield the imine (see alkylimino-de-oxo-bisubstitution for a detailed mechanism). The equilibrium in this reaction usually favors the carbonyl compound and amine, so that azeotropic distillation or use of a dehydrating agent, such as molecular sieves or magnesium sulfate, is required to favor of imine formation. In recent years, several reagents such as Tris(2,2,2-trifluoroethyl)borate [B(OCHCF)], pyrrolidine or titanium ethoxide [Ti(OEt)] have been shown to catalyse imine formation.
Rarer than primary amines is the use of ammonia to give a primary imine. In the case of hexafluoroacetone, the hemiaminal intermediate can be isolated. | 0 | Theoretical and Fundamental Chemistry |
The words care, therapy, treatment, and intervention overlap in a semantic field, and thus they can be synonymous depending on context. Moving rightward through that order, the connotative level of holism decreases and the level of specificity (to concrete instances) increases. Thus, in health-care contexts (where its senses are always noncount), the word care tends to imply a broad idea of everything done to protect or improve someones health (for example, as in the terms preventive care and primary care, which connote ongoing action), although it sometimes implies a narrower idea (for example, in the simplest cases of wound care or postanesthesia care, a few particular steps are sufficient, and the patients interaction with the provider of such care is soon finished). In contrast, the word intervention tends to be specific and concrete, and thus the word is often countable; for example, one instance of cardiac catheterization is one intervention performed, and coronary care (noncount) can require a series of interventions (count). At the extreme, the piling on of such countable interventions amounts to interventionism, a flawed model of care lacking holistic circumspection—merely treating discrete problems (in billable increments) rather than maintaining health. Therapy and treatment, in the middle of the semantic field, can connote either the holism of care or the discreteness of intervention, with context conveying the intent in each use. Accordingly, they can be used in both noncount and count senses (for example, therapy for chronic kidney disease can involve several dialysis treatments per week).
The words aceology and iamatology are obscure and obsolete synonyms referring to the study of therapies.
The English word therapy comes via Latin therapīa from and literally means "curing" or "healing". The term is a somewhat archaic doublet of the word therapy. | 1 | Applied and Interdisciplinary Chemistry |
The friction coefficient for ice, without a liquid film on the surface, is measured to be . A comparable friction coefficient is that of rubber or bitumen (roughly 0.8), which would be very difficult to ice skate on. The friction coefficients needs to be around or below 0.005 for ice skating to be possible. The reason ice skating is possible is because there is a thin film of water present between the blade of the ice skate and the ice. The origin of this water film has been a long-standing debate.
There are three proposed mechanisms that could account for a film of liquid water on the ice surface:
* Pressure Melting: James Thomson suggested as early as 1849 that expansion of water as it freezes implied that ice should melt upon compression. This idea was exploited by John Joly as a mechanism for ice skating, arguing that the pressure on the skates could melt ice and thereby create a lubricating film (1886).
* Premelting: Previously, Faraday and Tyndall had argued that the slipperiness of ice was due to the existence of a premelting film on the ice surface, irrespective of pressure.
* Friction: Bowden instead argued that heat generated from the ice skates moving, melts a small amount of ice under the blade.
While contributions from all three of these factors are usually in effect when ice skating, the scientific community has long debated over which is the dominating mechanism. For several decades it was common to explain the low friction of the skates on ice by pressure melting, but there are several recent arguments that contradict this hypothesis. The strongest argument against pressure melting is that ice skating is still possible below temperatures under -20 °C (253K). At this temperature, a great deal of pressure (>100MPa) is required to induce melting. Just below -23 °C (250K), increasing the pressure can only form a different solid structure of ice (Ice III) since the isotherm no longer passes through the liquid phase on the phase diagram. While impurities in the ice will suppress the melting temperature, many materials scientists agree that pressure melting is not the dominant mechanism.
The thickness of the water film due to premelting is also limited at low temperatures. While the water film can reach thicknesses on the order of μm, at temperatures around -10 °C the thickness is on the order of nm.
Although, De Koning et al. found in their measurements that the adding of impurities to the ice can lower the friction coefficient up to 15%. The friction coefficient increases with skating speed, which could yield different results depending on the skating technique and speeds.
While the pressure melting hypothesis may have been put to rest, the debate between premelting and friction as the dominant mechanism still rages on. | 0 | Theoretical and Fundamental Chemistry |
Aside from their basicity, the dominant reactivity of amines is their nucleophilicity. Most primary amines are good ligands for metal ions to give coordination complexes. Amines are alkylated by alkyl halides. Acyl chlorides and acid anhydrides react with primary and secondary amines to form amides (the "Schotten–Baumann reaction").
Similarly, with sulfonyl chlorides, one obtains sulfonamides. This transformation, known as the Hinsberg reaction, is a chemical test for the presence of amines.
Because amines are basic, they neutralize acids to form the corresponding ammonium salts . When formed from carboxylic acids and primary and secondary amines, these salts thermally dehydrate to form the corresponding amides.
Amines undergo sulfamation upon treatment with sulfur trioxide or sources thereof: | 0 | Theoretical and Fundamental Chemistry |
Moissan died suddenly in Paris in February 1907, shortly after his return from receiving the Nobel Prize in Stockholm. His death was attributed to an acute case of appendicitis, however, there is speculation that repeated exposure to fluorine and carbon monoxide also contributed to his death. | 0 | Theoretical and Fundamental Chemistry |
Early quantum models included a soliton pair creation model by Maki and a proposal by John Bardeen that condensed CDW electrons tunnel coherently through a tiny pinning gap, fixed at ±k unlike the Peierls gap. Makis theory lacked a sharp threshold field and Bardeen only gave a phenomenological interpretation of the threshold field. However, a 1985 paper by Krive and Rozhavsky pointed out that nucleated solitons and antisolitons of charge ±q generate an internal electric field E* proportional to q/ε. The electrostatic energy (1/2)ε[E ± E*] prevents soliton tunneling for applied fields E less than a threshold E = E*/2 without violating energy conservation. Although this Coulomb blockade threshold can be much smaller than the classical depinning field, it shows the same scaling with impurity concentration since the CDWs polarizability and dielectric response ε vary inversely with pinning strength.
Building on this picture, as well as a 2000 article on time-correlated soliton tunneling, a more recent quantum model proposes Josephson-like coupling (see Josephson effect) between complex order parameters associated with nucleated droplets of charged soliton dislocations on many parallel chains. Following Richard Feynman in The Feynman Lectures on Physics, Vol. III, Ch. 21, their time-evolution is described using the Schrödinger equation as an emergent classical equation. The narrow-band noise and related phenomena result from the periodic buildup of electrostatic charging energy and thus do not depend on the detailed shape of the washboard pinning potential. Both a soliton pair-creation threshold and a higher classical depinning field emerge from the model, which views the CDW as a sticky quantum fluid or deformable quantum solid with dislocations, a concept discussed by Philip Warren Anderson. | 0 | Theoretical and Fundamental Chemistry |
NAD-dependent formate dehydrogenases are important in methylotrophic yeast and bacteria, being vital in the catabolism of C1 compounds such as methanol. The cytochrome-dependent enzymes are more important in anaerobic metabolism in prokaryotes. For example, in E. coli, the formate:ferricytochrome-b1 oxidoreductase is an intrinsic membrane protein with two subunits and is involved in anaerobic nitrate respiration.
NAD-dependent reaction
Formate + NAD CO + NADH + H
Cytochrome-dependent reaction
Formate + 2 ferricytochrome b1 CO + 2 ferrocytochrome b1 + 2 H | 1 | Applied and Interdisciplinary Chemistry |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.