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Intelectins are lectins (carbohydrate-binding proteins) expressed in humans and other chordates. Humans express two types of intelectins encoded by ITLN1 and ITLN2 genes respectively. Several intelectins bind microbe-specific carbohydrate residues. Therefore, intelectins have been proposed to function as immune lectins. Even though intelectins contain fibrinogen-like domain found in the ficolins family of immune lectins, there is significant structural divergence. Thus, intelectins may not function through the same lectin-complement pathway. Most intelectins are still poorly characterized and they may have diverse biological roles. Human intelectin-1 (hIntL-1) has also been shown to bind lactoferrin, but the functional consequence has yet to be elucidated. Additionally, hIntL-1 is a major component of asthmatic mucus and may be involved in insulin physiology as well. | 1 | Applied and Interdisciplinary Chemistry |
Sulfinamides are traditionally produced by the reaction of sulfinyl chlorides with primary or secondary amines. They also arise by the addition of Grignard reagents to sulfinylamines, followed by protonation:
:RMgX + RN=S=O → RS(O)(NRMgX)
:RS(O)(NRMgX) + HO → RS(O)(NRH) + "MgX(OH)"
Yet another route entails peracid-oxidation of sulfenylphthalimides, which gives sulfinylphthalimides. | 0 | Theoretical and Fundamental Chemistry |
The Hansen solubility parameter (HSP) values are based on dispersion bonds (δD), polar bonds (δP) and hydrogen bonds (δH). These contain information about the inter-molecular interactions with other solvents and also with polymers, pigments, nanoparticles, etc. This allows for rational formulations knowing, for example, that there is a good HSP match between a solvent and a polymer. Rational substitutions can also be made for "good" solvents (effective at dissolving the solute) that are "bad" (expensive or hazardous to health or the environment). The following table shows that the intuitions from "non-polar", "polar aprotic" and "polar protic" are put numerically – the "polar" molecules have higher levels of δP and the protic solvents have higher levels of δH. Because numerical values are used, comparisons can be made rationally by comparing numbers. For example, acetonitrile is much more polar than acetone but exhibits slightly less hydrogen bonding.
If, for environmental or other reasons, a solvent or solvent blend is required to replace another of equivalent solvency, the substitution can be made on the basis of the Hansen solubility parameters of each. The values for mixtures are taken as the weighted averages of the values for the neat solvents. This can be calculated by trial-and-error, a spreadsheet of values, or HSP software. A 1:1 mixture of toluene and 1,4 dioxane has δD, δP and δH values of 17.8, 1.6 and 5.5, comparable to those of chloroform at 17.8, 3.1 and 5.7 respectively. Because of the health hazards associated with toluene itself, other mixtures of solvents may be found using a full HSP dataset. | 1 | Applied and Interdisciplinary Chemistry |
Due to every method of gene transfer having shortcomings, there have been some hybrid methods developed that combine two or more techniques. Virosomes are one example; they combine liposomes with an inactivated HIV or influenza virus. This has been shown to have more efficient gene transfer in respiratory epithelial cells than either viral or liposomal methods alone. Other methods involve mixing other viral vectors with cationic lipids or hybridising viruses. | 1 | Applied and Interdisciplinary Chemistry |
The majority of clinically actionable pharmacogenetic variation occurs in genes that code for drug-metabolizing enzymes, including those involved in both phase I and phase II metabolism. The cytochrome P450 enzyme family is responsible for metabolism of 70-80% of all medications used clinically. CYP3A4, CYP2C9, CYP2C19, and CYP2D6 are major CYP enzymes involved in drug metabolism and are all known to be highly polymorphic. Additional drug-metabolizing enzymes that have been implicated in pharmacogenetic interactions include UGT1A1 (a UDP-glucuronosyltransferase), DPYD, and TPMT. | 1 | Applied and Interdisciplinary Chemistry |
For this article, annular velocity is described, as used in drilling fluid applications in the oil exploration industry. There may be other applications in other fields of study such as fluid mechanics (the study of the movement of fluid) or fluid dynamics (the study of the flow of fluid). | 1 | Applied and Interdisciplinary Chemistry |
In the 19th century, a number of people had employed an electric arc to melt iron. Sir Humphry Davy conducted an experimental demonstration in 1810; welding was investigated by Pepys in 1815; Pinchon attempted to create an electrothermic furnace in 1853; and, in 1878–79, Sir William Siemens took out patents for electric furnaces of the arc type.
The first successful and operational furnace was invented by James Burgess Readman in Edinburgh, Scotland, in 1888 and patented in 1889. This was specifically for the creation of phosphorus.
Further electric arc furnaces were developed by Paul Héroult, of France, with a commercial plant established in the United States in 1907. The Sanderson brothers formed The Sanderson Brothers Steel Co. in Syracuse, New York, installing the first electric arc furnace in the U.S. This furnace is now on display at Station Square, Pittsburgh, Pennsylvania.
Initially "electric steel" produced by an electric arc furnace was a specialty product for such uses as machine tools and spring steel. Arc furnaces were also used to prepare calcium carbide for use in carbide lamps. The Stassano electric furnace is an arc type furnace that usually rotates to mix the bath. The Girod furnace is similar to the Héroult furnace.
While EAFs were widely used in World War II for production of alloy steels, it was only later that electric steelmaking began to expand. The low capital cost for a mini-mill—around US$140–200 per ton of annual installed capacity, compared with US$1,000 per ton of annual installed capacity for an integrated steel mill—allowed mills to be quickly established in war-ravaged Europe, and also allowed them to successfully compete with the big United States steelmakers, such as Bethlehem Steel and U.S. Steel, for low-cost, carbon steel "long products" (structural steel, rod and bar, wire, and fasteners) in the U.S. market.
When Nucor—now one of the largest steel producers in the US — entered the market for long steel products in 1969, they used a mini-mill with an EAF as its steelmaking furnace, soon followed by other manufacturers. Whilst Nucor expanded rapidly in the Eastern US, the companies that followed them into mini-mill operations concentrated on local markets for long products, where the EAF allowed the plants to vary production according to local demand. This pattern was followed globally, with EAF steel production primarily used for long products, while integrated mills, using blast furnaces and basic oxygen furnaces, cornered the markets for "flat products"—sheet steel and heavier steel plate. In 1987, Nucor expanded into the flat products market, still using the EAF production method. | 1 | Applied and Interdisciplinary Chemistry |
Olson's studies DNA as polymers, with atoms and chemical bonds. She studies the interaction between DNA and structural proteins which do not bind to the nuclear bases, but to the phosphorus-sugar backbone, e.g.histones. Also, the energy needed to form circular DNA is investigated Olson aims to clarify the role of local structure on the overall folding of RNA, for instance the helices and loops in the ribosome. A second goal is to uncover structural details of nucleic acid structural transitions, such as those involving different DNA duplexes. This information helps to design new drugs and materials. | 1 | Applied and Interdisciplinary Chemistry |
The Oxford English Dictionary (OED) entry on siphon, published in 1911, states that a siphon works by atmospheric pressure. Stephen Hughes of Queensland University of Technology criticized this in a 2010 article which was widely reported in the media. The OED editors stated, "there is continuing debate among scientists as to which view is correct. ... We would expect to reflect this debate in the fully updated entry for siphon, due to be published later this year." Hughes continued to defend his view of the siphon in a late September post at the Oxford blog. The 2015 definition by the OED is:
The Encyclopædia Britannica currently describes a siphon as: | 1 | Applied and Interdisciplinary Chemistry |
Copper(I) thiophene-2-carboxylate or CuTC is a coordination complex derived from copper and thiophene-2-carboxylic acid. It is used as a reagent to promote the Ullmann reaction between aryl halides. | 0 | Theoretical and Fundamental Chemistry |
There are at least four members of SLC-5 gene family, which are secondary active glucose transporters. The sodium glucose transporters proteins SGLT-1 and SGLT-2 are the two premier members of the family. These two members are found in the kidneys, among other transporters, and are the main co-transporters there related to the blood sugar. They play a role in renal glucose reabsorption and in intestinal glucose absorption.
Blood glucose is freely filtered by the glomeruli and SGLT-1 and SGLT-2 reabsorb glucose in the kidneys and put it back into the circulation cells. SGLT-2 is responsible for 90% of the reabsorption and SGLT-1 for the other 10%. | 1 | Applied and Interdisciplinary Chemistry |
When the energy of a turbidity current lowers, its ability to keep suspended sediment decreases, thus sediment deposition occurs. When the material comes to rest, it is the sand and other coarse material which settles first followed by mud and eventually the very fine particulate matter. It is this sequence of deposition that creates the so called Bouma sequences that characterize turbidite deposits.
Because turbidity currents occur underwater and happen suddenly, they are rarely seen as they happen in nature, thus turbidites can be used to determine turbidity current characteristics. Some examples: grain size can give indication of current velocity, grain lithology and the use of foraminifera for determining origins, grain distribution shows flow dynamics over time and sediment thickness indicates sediment load and longevity.
Turbidites are commonly used in the understanding of past turbidity currents, for example, the Peru-Chile Trench off Southern Central Chile (36°S–39°S) contains numerous turbidite layers that were cored and analysed. From these turbidites the predicted history of turbidity currents in this area was determined, increasing the overall understanding of these currents. | 1 | Applied and Interdisciplinary Chemistry |
Lavoisier employed the new nomenclature in his Traité élémentaire de chimie (Elementary Treatise on Chemistry), published in 1789. This work represents the synthesis of Lavoisiers contribution to chemistry and can be considered the first modern textbook on the subject. The core of the work was the oxygen theory, and the work became a most effective vehicle for the transmission of the new doctrines. It presented a unified view of new theories of chemistry, contained a clear statement of the law of conservation of mass, and denied the existence of phlogiston. This text clarified the concept of an element as a substance that could not be broken down by any known method of chemical analysis and presented Lavoisiers theory of the formation of chemical compounds from elements. It remains a classic in the history of science. While many leading chemists of the time refused to accept Lavoisiers new ideas, demand for Traité élémentaire as a textbook in Edinburgh was sufficient to merit translation into English within about a year of its French publication. In any event, the Traité élémentaire' was sufficiently sound to convince the next generation. | 1 | Applied and Interdisciplinary Chemistry |
The Fano resonance line-shape is due to interference between two scattering amplitudes, one due to scattering within a continuum of states (the background process) and the second due to an excitation of a discrete state (the resonant process). The energy of the resonant state must lie in the energy range of the continuum (background) states for the effect to occur. Near the resonant energy, the background scattering amplitude typically varies slowly with energy while the resonant scattering amplitude changes both in magnitude and phase quickly. It is this variation that creates the asymmetric profile.
For energies far from the resonant energy the background scattering process dominates. Within of the resonant energy, the phase of the resonant scattering amplitude changes by . It is this rapid variation in phase that creates the asymmetric line-shape.
Fano showed that the total scattering cross-section assumes the following form,
where describes the line width of the resonant energy and , the Fano parameter, measures the ratio of resonant scattering to the direct (background) scattering amplitude. This is consistent with the interpretation within the Feshbach–Fano partitioning theory. In the case the direct scattering amplitude vanishes, the parameter becomes zero and the Fano formula becomes :
Looking at transmission shows that this last expression boils down to the expected Breit–Wigner (Lorentzian) formula, as , the three parameters Lorentzian function (note that it is not a density function and does not integrate to 1, as its amplitude is 1 and not ). | 0 | Theoretical and Fundamental Chemistry |
It was established by the decree of Peter the Great to process the local copper deposits. The Polevskoy Plant was named after the local river Polevaya. The plant became the basis for the settlement which later grew into the town of Polevskoy.
The place for a new plant was chosen by Vasily Tatishchev. Georg Wilhelm de Gennin was in charge of the construction. The Plant became active in 1724. The copper was branded with the symbol of the Roman goddess Venus. The Venus symbol (♀), which represents copper as a chemical element, is now displayed in the Polevskoy town coat of arms.
In 1757 the Polevskoy Plant was purchased by the Ural merchant Alexei Turchaninov along with the Seversky Pipe Plant. Along with the Seversky and Sysertsky Plants, the Polevskoy Plant represented the Sysert Mining District. It was extremely profitable. Turchaninov's descendants managed the plant til 1912. For a long time the main ore supplier for the plant was the Gumyoshevsky mine, called "The Copper Mountain" by the local populace. However in the 19th century the Gumyoshevsky mine was exhausted. After it was shut down in 1870, the Polevskoy Copper Smelting Plant was reorganized to the iron plant. In this capacity the plant stayed active until 1923, but then shut down due to the lack of prospects. | 1 | Applied and Interdisciplinary Chemistry |
The targeted deletion or alteration of genes relies on the integration of a DNA strand at a specific and predictable position into the genome of the host cell. This DNA strand must be engineered in such a way that both ends are identical to this specific gene locus. This is a prerequisite for being efficiently integrated via homologous recombination (HR). This is similar to the process used for creating knockout mice.
So far, this method of gene targeting in land plants has been carried out in the mosses Physcomitrella patens and Ceratodon purpureus, since in these non-seed plant species the efficiency of HR is several orders of magnitude higher than in seed plants.
Knockout mosses are stored at and distributed by a specialized biobank, the International Moss Stock Center. | 1 | Applied and Interdisciplinary Chemistry |
Chemical systems cannot oscillate about a position of final equilibrium because such an oscillation would violate the second law of thermodynamics. For a thermodynamic system which is not at equilibrium, this law requires that the system approach equilibrium and not recede from it. For a closed system at constant temperature and pressure, the thermodynamic requirement is that the Gibbs free energy must decrease continuously and not oscillate. However it is possible that the concentrations of some reaction intermediates oscillate, and also that the rate of formation of products oscillates.
Theoretical models of oscillating reactions have been studied by chemists, physicists, and mathematicians. In an oscillating system the energy-releasing reaction can follow at least two different pathways, and the reaction periodically switches from one pathway to another. One of these pathways produces a specific intermediate, while another pathway consumes it. The concentration of this intermediate triggers the switching of pathways. When the concentration of the intermediate is low, the reaction follows the producing pathway, leading then to a relatively high concentration of intermediate. When the concentration of the intermediate is high, the reaction switches to the consuming pathway.
Different theoretical models for this type of reaction have been created, including the Lotka-Volterra model, the Brusselator and the Oregonator. The latter was designed to simulate the Belousov-Zhabotinsky reaction. | 1 | Applied and Interdisciplinary Chemistry |
A biological example of diffusion is the gas exchange that occurs during respiration within the human body. Upon inhalation, oxygen is brought into the lungs and quickly diffuses across the membrane of alveoli and enters the circulatory system by diffusing across the membrane of the pulmonary capillaries. Simultaneously, carbon dioxide moves in the opposite direction, diffusing across the membrane of the capillaries and entering into the alveoli, where it can be exhaled. The process of moving oxygen into the cells, and carbon dioxide out, occurs because of the concentration gradient of these substances, each moving away from their respective areas of higher concentration toward areas of lower concentration. Cellular respiration is the cause of the low concentration of oxygen and high concentration of carbon dioxide within the blood which creates the concentration gradient. Because the gasses are small and uncharged, they are able to pass directly through the cell membrane without any special membrane proteins. No energy is required because the movement of the gasses follows Fick's first law and the second law of thermodynamics. | 1 | Applied and Interdisciplinary Chemistry |
Two opposite explanations that endeavored to explain the formations of isochores were vigorously debated as part of the neutralist-selectionist controversy. The first view was that isochores reflect variable mutation processes among genomic regions consistent with the neutral model.
Alternatively, isochores were posited as a result of natural selection for certain compositional environment required by certain genes. Several hypotheses derive from the selectionist view, such as the thermodynamic stability hypothesis and the biased gene conversion hypothesis. Thus far, none of the theories provides a comprehensive explanation to the genome structure, and the topic is still under debate. | 1 | Applied and Interdisciplinary Chemistry |
The binding of proteins to the SELDI surface acts as a solid-phase chromatographic separation step, and as a result, the proteins attached to the surface are easier to analyze. The surface is composed primarily of materials with a variety of physico-chemical characteristics, metal ions, or anion or cation exchangers. Common surfaces include CM10 (weak cation exchange), H50 (hydrophobic surface, similar to C-C reverse phase chromatography), IMAC30 (metal-binding surface), and Q10 (strong anion exchange). SELDI surfaces can also be modified to study DNA-protein binding, antibody-antigen assays, and receptor-ligand interactions. | 1 | Applied and Interdisciplinary Chemistry |
Process simulation is a model-based representation of chemical, physical, biological, and other technical processes and unit operations in software. Basic prerequisites for the model are chemical and physical properties of pure components and mixtures, of reactions, and of mathematical models which, in combination, allow the calculation of process properties by the software.
Process simulation software describes processes in flow diagrams where unit operations are positioned and connected by product or educt streams. The software solves the mass and energy balance to find a stable operating point on specified parameters. The goal of a process simulation is to find optimal conditions for a process. This is essentially an optimization problem which has to be solved in an iterative process.
In the example above the feed stream to the column is defined in terms of its chemical and physical properties. This includes the composition of individual molecular species in the stream; the overall mass flowrate; the streams pressure and temperature. For hydrocarbon systems the Vapor-Liquid Equilibrium Ratios (K-Values) or models that are used to define them are specified by the user. The properties of the column are defined such as the inlet pressure and the number of theoretical plates. The duty of the reboiler and overhead condenser are calculated by the model to achieve a specified composition or other parameter of the bottom and/or top product. The simulation calculates the chemical and physical properties of the product streams, each is assigned a unique number which is used in the mass and energy diagram.
Process simulation uses models which introduce approximations and assumptions but allow the description of a property over a wide range of temperatures and pressures which might not be covered by available real data. Models also allow interpolation and extrapolation - within certain limits - and enable the search for conditions outside the range of known properties. | 1 | Applied and Interdisciplinary Chemistry |
ACS Medicinal Chemistry Letters is a monthly peer-reviewed scientific journal covering medicinal chemistry. It was established in 2009 and is published by the American Chemical Society. The editor-in-chief is Dennis C. Liotta (Emory University).
According to the Journal Citation Reports, the journal has a 2021 impact factor of 4.632. | 1 | Applied and Interdisciplinary Chemistry |
Without a chiral influence (for example a chiral catalyst, solvent or starting material), a chemical reaction that makes a chiral product will always yield a racemate. That can make the synthesis of a racemate cheaper and easier than making the pure enantiomer, because it does not require special conditions. This fact also leads to the question of how biological homochirality evolved on what is presumed to be a racemic primordial earth.
The reagents of, and the reactions that produce, racemic mixtures are said to be "not stereospecific" or "not stereoselective", for their indecision in a particular stereoisomerism. A frequent scenario is that of a planar species (such as an sp carbon atom or a carbocation intermediate) acting as an electrophile. The nucleophile will have a 50% probability of hitting either of the two sides of the planar grouping, thus producing a racemic mixture: | 0 | Theoretical and Fundamental Chemistry |
Multipstep ultrasensitivity occurs when a single effector acts on several steps in a cascade. Successive cascade signals can result in higher levels of noise being introduced into the signal that can interfere with the final output. This is especially relevant for large cascades, such as the flagellar regulatory system in which the master regulator signal is transmitted through multiple intermediate regulators before activating transcription. Cascade ultrasensitivity can reduce noise and therefore require less input for activation. Additionally, multiple phosphorylation events are an example of ultrasensitivity. Recent modeling has shown that multiple phosphorylation sites on membrane proteins could serve to locally saturate enzyme activity. Proteins at the membrane are greatly reduced in mobility compared to those in the cytoplasm, this means that a membrane tethered enzyme acting upon a membrane protein will take longer to diffuse away. With the addition of multiple phosphorylation sites upon the membrane substrate, the enzyme can - by a combination of increased local concentration of enzyme and increased substrates - quickly reach saturation. | 1 | Applied and Interdisciplinary Chemistry |
*"Maßanalytische Bestimmung des Schwefelwasserstoffes in alkalischer Lösung mit Ferricyankalium", Japanese J. Chem., 1, 43 - 54 (1922)
*"Radioactive Manganiferous Nodules from Tanokami Oomi Province", [https://dx.doi.org/10.1246/bcsj.1.43 Bull. Chem. Soc. Japan, 1, 43 - 47 (1926)]
*"Formation of the Radioactive Manganiferous Deposits from Tanokami, and the Source of Manganese in the Deep-sea Manganese Nodules", [http://doi.org/10.1246/bcsj.2.270 Bull. Chem. Soc. Japan, 2, 270 - 273 (1927)]
*"Photochemical Cell with Complex Cyanides of Nickel or Platinum", Sc.Pap.I.P.C.R.,8', 14 - 15(1928)
*"The Uranium-Thorium Ratio in Monazite", Sc. Pap. I.P.C.R., 10, 229 - 236 (1929)
*"A Pink Kaolin, and Ruthenium as a Minor Constituent of the Tanokami Kaolin", [http://doi.org/10.1246/bcsj.4.1 Bull. Chem. Soc. Japan, 4, 1 - 5 (1929)]
*"Periodicity in the Solarization of Calcite", Nature, 131, 619 (1933)
*"The Photoluminescence of Feldspar", Sc.Pap.I.P.C.R., 29, 79 - 110 (1936)
Sci.Pap.I.P.C.R:Scientific papers of the Institute of Physical and Chemical Research | 0 | Theoretical and Fundamental Chemistry |
Leonidas Zervas (, ; 21 May 1902 – 10 July 1980) was a Greek organic chemist who made seminal contributions in peptide chemical synthesis. Together with his mentor Max Bergmann they laid the foundations for the field in 1932 with their major discovery, the Bergmann-Zervas carboxybenzoxy oligopeptide synthesis which remained unsurpassed in utility for the next two decades. The carboxybenzyl protecting group he discovered is often abbreviated Z in his honour.
Throughout his life Zervas also served in many important posts, including President of the Academy of Athens or briefly Minister of Industry of Greece. He received numerous awards and honours during his life and posthumously, such as Foreign Member of the USSR Academy of Sciences or the first Max Bergmann golden medal. | 0 | Theoretical and Fundamental Chemistry |
Most humans have multiple copies of the regulatory gene sequence for prodynorphin, which is virtually identical among all primates, whereas other primates have only a single copy. In addition, most Asian populations have two copies of the gene sequence for prodynorphin, whereas East Africas, Middle Easterners, and Europeans tend to have three repetitions.
The extent of regulatory gene disparities for prodynorphin, between human and primates, has gained the attention of scientists. There are very few genes known to be directly related to mankind's speciation from other great apes. According to computational biologist researcher Matthew W. Hahn of Indiana University, "this is the first documented instance of a neural gene that has had its regulation shaped by natural selection during human origins."
The prodynorphin polypeptide is identical in humans and chimpanzees, but the regulatory promoter sequences have been shown to exhibit marked differences. According to Hahn, "humans have the ability to turn on this gene more easily and more intensely than other primates", a reason why regulation of this gene may have been important in the evolution of modern humans' mental capacity. | 1 | Applied and Interdisciplinary Chemistry |
A fundamental problem in finding solutions for surface gravity waves is that boundary conditions have to be applied at the position of the free surface, which is not known beforehand and is thus a part of the solution to be found.
Sir George Stokes solved this nonlinear wave problem in 1847 by expanding the relevant potential flow quantities in a Taylor series around the mean (or still) surface elevation. As a result, the boundary conditions can be expressed in terms of quantities at the mean (or still) surface elevation (which is fixed and known).
Next, a solution for the nonlinear wave problem (including the Taylor series expansion around the mean or still surface elevation) is sought by means of a perturbation series – known as the Stokes expansion – in terms of a small parameter, most often the wave steepness. The unknown terms in the expansion can be solved sequentially. Often, only a small number of terms is needed to provide a solution of sufficient accuracy for engineering purposes. Typical applications are in the design of coastal and offshore structures, and of ships.
Another property of nonlinear waves is that the phase speed of nonlinear waves depends on the wave height. In a perturbation-series approach, this easily gives rise to a spurious secular variation of the solution, in contradiction with the periodic behaviour of the waves. Stokes solved this problem by also expanding the dispersion relationship into a perturbation series, by a method now known as the Lindstedt–Poincaré method. | 1 | Applied and Interdisciplinary Chemistry |
SK channels (small conductance calcium-activated potassium channels) are a subfamily of calcium-activated potassium channels. They are so called because of their small single channel conductance in the order of 10 pS. SK channels are a type of ion channel allowing potassium cations to cross the cell membrane and are activated (opened) by an increase in the concentration of intracellular calcium through N-type calcium channels. Their activation limits the firing frequency of action potentials and is important for regulating afterhyperpolarization in the neurons of the central nervous system as well as many other types of electrically excitable cells. This is accomplished through the hyperpolarizing leak of positively charged potassium ions along their concentration gradient into the extracellular space. This hyperpolarization causes the membrane potential to become more negative. SK channels are thought to be involved in synaptic plasticity and therefore play important roles in learning and memory. | 1 | Applied and Interdisciplinary Chemistry |
An extensive open-air planting used maintain genetic diversity of wild, agricultural, or forestry species. Typically species that are either difficult or impossible to conserve in seed banks are conserved in field gene banks. Field gene banks may also be used grow and select progeny of species stored by other ex situ techniques. | 1 | Applied and Interdisciplinary Chemistry |
By 1993, the Everglades had been affected by numerous human developments. The water flow and quality had been affected by the construction of canals and levees, to the series of elevated highways running through the Everglades to the expansive Everglades Agricultural Area that had contaminated the Everglades with high amounts of nitrogen. The result of this reduced flow of water was dramatic. There was a 90 - 95% reduction in wading bird populations, declining fish populations and salt water intrusion into the ecosystem. If the Florida Everglades were to remain a US landmark, action needed to be taken. | 1 | Applied and Interdisciplinary Chemistry |
Pentamethyltantalum was reported by Richard Schrock in 1974.
Salts of [Ta(CH)] are prepared by alkylation of TaF using methyl lithium:
:TaF + 6 LiCH → Li[Ta(CH)] + 5 LiF | 0 | Theoretical and Fundamental Chemistry |
Several isotopes of both hydrogen and oxygen exist, giving rise to several known isotopologues of water. Vienna Standard Mean Ocean Water is the current international standard for water isotopes. Naturally occurring water is almost completely composed of the neutron-less hydrogen isotope protium. Only 155 ppm include deuterium ( or D), a hydrogen isotope with one neutron, and fewer than 20 parts per quintillion include tritium ( or T), which has two neutrons. Oxygen also has three stable isotopes, with present in 99.76%, in 0.04%, and in 0.2% of water molecules.
Deuterium oxide, , is also known as heavy water because of its higher density. It is used in nuclear reactors as a neutron moderator. Tritium is radioactive, decaying with a half-life of 4500 days; exists in nature only in minute quantities, being produced primarily via cosmic ray-induced nuclear reactions in the atmosphere. Water with one protium and one deuterium atom occur naturally in ordinary water in low concentrations (~0.03%) and in far lower amounts (0.000003%) and any such molecules are temporary as the atoms recombine.
The most notable physical differences between and , other than the simple difference in specific mass, involve properties that are affected by hydrogen bonding, such as freezing and boiling, and other kinetic effects. This is because the nucleus of deuterium is twice as heavy as protium, and this causes noticeable differences in bonding energies. The difference in boiling points allows the isotopologues to be separated. The self-diffusion coefficient of at 25 °C is 23% higher than the value of . Because water molecules exchange hydrogen atoms with one another, hydrogen deuterium oxide (DOH) is much more common in low-purity heavy water than pure dideuterium monoxide .
Consumption of pure isolated may affect biochemical processes—ingestion of large amounts impairs kidney and central nervous system function. Small quantities can be consumed without any ill-effects; humans are generally unaware of taste differences, but sometimes report a burning sensation or sweet flavor. Very large amounts of heavy water must be consumed for any toxicity to become apparent. Rats, however, are able to avoid heavy water by smell, and it is toxic to many animals.
Light water refers to deuterium-depleted water (DDW), water in which the deuterium content has been reduced below the standard level. | 1 | Applied and Interdisciplinary Chemistry |
The term phosphorescence comes from the ancient Greek word φῶς (phos), meaning "light", and the Greek suffix -φόρος (-phoros), meaning "to bear", combined with the Latin suffix -escentem, meaning "becoming of", "having a tendency towards", or "with the essence of". Thus, phosphorescence literally means "having a tendency to bear light". It was first recorded in 1766.
The term phosphor had been used since the Middle Ages to describe minerals that glowed in the dark. One of the most famous, but not the first, was Bolognian phosphor. Around 1604, Vincenzo Casciarolo discovered a "lapis solaris" near Bologna, Italy. Once heated in an oxygen-rich furnace, it thereafter absorbed sunlight and glowed in the dark. In 1677, Hennig Brand isolated a new element that glowed due to a chemiluminescent reaction when exposed to air, and named it "phosphorus".
In contrast, the term luminescence (from the Latin lumen for "light"), was coined by Eilhardt Wiedemann in 1888 as a term to refer to "light without heat", while "fluorescence" by Sir George Stokes in 1852, when he noticed that, when exposing a solution of quinine sulfate to light refracted through a prism, the solution glowed when exposed to the mysterious invisible-light (now known to be UV light) beyond the violet end of the spectrum. Stokes formed the term from a combination of fluorspar and opalescence (preferring to use a mineral instead of a solution), albeit it was later discovered that fluorspar glows due to phosphorescence.
There was much confusion between the meanings of these terms throughout the late nineteenth to mid-twentieth centuries. Whereas the term "fluorescence" tended to refer to luminescence that ceased immediately (by human-eye standards) when removed from excitation, "phosphorescence" referred to virtually any substance that glowed for appreciable periods in darkness, sometimes to include even chemiluminescence (which occasionally produced substantial amounts of heat). Only after the 1950s and 1960s did advances in quantum electronics, spectroscopy, and lasers provide a measure to distinguish between the various processes that emit the light, although in common speech the distinctions are still often rather vague. | 0 | Theoretical and Fundamental Chemistry |
The term nocebo (Latin , I shall harm, from , I harm) was coined by Walter Kennedy in 1961 to denote the counterpart to the use of placebo (Latin , I shall please, from , I please), a substance that may produce a beneficial, healthful, pleasant, or desirable effect. Kennedy emphasized that his use of the term nocebo refers strictly to a subject-centered response, a quality inherent in the patient rather than in the remedy". That is, Kennedy rejected the use of the term for pharmacologically induced negative side effects such as the ringing in the ears caused by quinine. That is not to say that the patient's psychologically induced response may not include physiological effects. For example, an expectation of pain may induce anxiety, which in turn causes the release of cholecystokinin, which facilitates pain transmission. | 1 | Applied and Interdisciplinary Chemistry |
Osmotic release systems have a number of major advantages over other controlled-release mechanisms. They are significantly less affected by factors such as pH, food intake, GI motility, and differing intestinal environments. Using an osmotic pump to deliver drugs has additional inherent advantages regarding control over drug delivery rates. This allows for much more precise drug delivery over an extended period of time, which results in much more predictable pharmacokinetics. However, osmotic release systems are relatively complicated, somewhat difficult to manufacture, and may cause irritation or even blockage of the GI tract due to prolonged release of irritating drugs from the non-deformable tablet. | 1 | Applied and Interdisciplinary Chemistry |
The classification of thermodynamic systems arose with the development of thermodynamics as a science.
Theoretical studies of thermodynamic processes in the period from the first theory of heat engines (Saadi Carnot, France, 1824) to the theory of dissipative structures (Ilya Prigozhin, Belgium, 1971) mainly concerned the patterns of interaction of thermodynamic systems with the environment.
At the same time, thermodynamic systems were mainly classified as isolated, closed and open, with corresponding properties in various thermodynamic states, for example, in states close to equilibrium, nonequilibrium and strongly nonequilibrium.
In 2010, Boris Dobroborsky (Israel, Russia) proposed a classification of thermodynamic systems according to internal processes consisting in energy redistribution (passive systems) and energy conversion (active systems). | 0 | Theoretical and Fundamental Chemistry |
In the case of protein folding, the hydrophobic effect is important to understanding the structure of proteins that have hydrophobic amino acids (such as valine, leucine, isoleucine, phenylalanine, tryptophan and methionine) clustered together within the protein. Structures of globular proteins have a hydrophobic core in which hydrophobic side chains are buried from water, which stabilizes the folded state. Charged and polar side chains are situated on the solvent-exposed surface where they interact with surrounding water molecules. Minimizing the number of hydrophobic side chains exposed to water is the principal driving force behind the folding process, although formation of hydrogen bonds within the protein also stabilizes protein structure.
The energetics of DNA tertiary-structure assembly were determined to be driven by the hydrophobic effect, in addition to Watson–Crick base pairing, which is responsible for sequence selectivity, and stacking interactions between the aromatic bases. | 0 | Theoretical and Fundamental Chemistry |
Multiple isomorphous replacement (MIR), where heavy atoms are inserted into structure (usually by synthesizing proteins with analogs or by soaking) | 0 | Theoretical and Fundamental Chemistry |
The digestive system is supplied by the celiac artery. The celiac artery is the first major branch from the abdominal aorta, and is the only major artery that nourishes the digestive organs.
There are three main divisions – the left gastric artery, the common hepatic artery and the splenic artery.
The celiac artery supplies the liver, stomach, spleen and the upper 1/3 of the duodenum (to the sphincter of Oddi) and the pancreas with oxygenated blood. Most of the blood is returned to the liver via the portal venous system for further processing and detoxification before returning to the systemic circulation via the hepatic veins.
The next branch from the abdominal aorta is the superior mesenteric artery, which supplies the regions of the digestive tract derived from the midgut, which includes the distal 2/3 of the duodenum, jejunum, ileum, cecum, appendix, ascending colon, and the proximal 2/3 of the transverse colon.
The final branch which is important for the digestive system is the inferior mesenteric artery, which supplies the regions of the digestive tract derived from the hindgut, which includes the distal 1/3 of the transverse colon, descending colon, sigmoid colon, rectum, and the anus above the pectinate line.
Blood flow to the digestive tract reaches its maximum 20–40 minutes after a meal and lasts for 1.5–2 hours. | 1 | Applied and Interdisciplinary Chemistry |
Peroxin-7 is a receptor associated with Refsum's disease and rhizomelic chondrodysplasia punctata type 1. | 1 | Applied and Interdisciplinary Chemistry |
Nipah virus is a causative agent of outbreaks of encephalitis with pneumonia and has a high case fatality rate. The first outbreak occurred in Malaysia-Singapore, related to contact with pigs in slaughterhouses and an outbreak in Philippines related to slaughter of horses, most other outbreaks have affected India and Bangladesh. in Bangladesh outbreaks are often associated with consumption of raw date palm sap contaminated by saliva and urine of fruit bats. In a study published in the Scientific Reports, Syrian hamster model for Nipah virus infection was used, which closely mirrors most aspects of human disease, such as widespread vasculitis, pneumonia, and encephalitis. The hamsters were infected with a lethal dose of 10 PFU NiV-M via the intraperitoneal (i.p.) route similar to previous studies and treatment was initiated immediately after infection. Favipiravir was administered twice daily via the peroral (p.o.) route for 14 days. The treated hamsters displayed 100% survival and no obvious morbidity after lethal NiV challenge, whereas all the control cases died of severe disease. | 0 | Theoretical and Fundamental Chemistry |
Mitochondrial creatine kinase (CK) is present in the mitochondrial intermembrane space, where it regenerates phosphocreatine (PCr) from mitochondrially generated ATP and creatine (Cr) imported from the cytosol. Apart from the two mitochondrial CK isoenzyme forms, that is, ubiquitous mtCK (present in non-muscle tissues) and sarcomeric mtCK (present in sarcomeric muscle), there are three cytosolic CK isoforms present in the cytosol, depending on the tissue. Whereas MM-CK is expressed in sarcomeric muscle, that is, skeletal and cardiac muscle, MB-CK is expressed in cardiac muscle, and BB-CK is expressed in smooth muscle and in most non-muscle tissues.
Mitochondrial mtCK and cytosolic CK are connected in a so-called PCr/Cr-shuttle or circuit. PCr generated by mtCK in mitochondria is shuttled to cytosolic CK that is coupled to ATP-dependent processes, e.g. ATPases, such as acto-myosin ATPase and calcium ATPase involved in muscle contraction, and sodium/potassium ATPase involved in sodium retention in the kidney. The bound cytosolic CK accepts the PCr shuttled through the cell and uses ADP to regenerate ATP, which can then be used as an energy source by the ATPases (CK is associated intimately with the ATPases, forming a functionally coupled microcompartment). PCr is not only an energy buffer, but also a cellular transport form of energy between subcellular sites of energy (ATP) production (mitochondria and glycolysis) and those of energy utilization (ATPases).
Thus, CK enhances skeletal, cardiac, and smooth muscle contractility, and is involved in the generation of blood pressure. Further, the ADP-scavenging action of creatine kinase has been implicated in bleeding disorders: persons with highly elevated plasma CK could be prone to major bleeding. | 1 | Applied and Interdisciplinary Chemistry |
The earliest forms of French drains were simple ditches that were pitched from a high area to a lower one and filled with gravel. These may have been invented in France but Henry Flagg French (1813–1885) of Concord, Massachusetts, a lawyer and Assistant U.S. Treasury Secretary described and popularized them in Farm Drainage (1859). French's own drains were made of sections of ordinary roofing tile that were laid with a gap in between the sections to admit water. Later, specialised drain tiles were designed with perforations. To prevent clogging, the size of the gravel varied from coarse in the center to fine on the outside and was selected contingent on the gradation of the surrounding soil. The sizes of particles were critical to prevent the surrounding soil from washing into the pores, i. e., voids between the particles of gravel and thereby clogging the drain. The later development of geotextiles greatly simplified this technique.
Ditches are dug manually or by a trencher. An inclination of 1 in 100 to 1 in 200 is typical. Lining the bottom of the ditch with clay or plastic pipe increases the volume of water that can flow through the drain. Modern French drain systems are made of perforated pipe, for example weeping tile surrounded by sand or gravel, and geotextile or landscaping textile. Landscaping textiles prevent migration of the drainage material and prevent soil and roots from entering and clogging the pipe. The perforated pipe provides a minor subterranean volume of storage for water, yet the prime purpose is drainage of the area along the full length of the pipe via its perforations and to discharge any surplus water at its terminus. The direction of percolation depends on the relative conditions within and without the pipe.
Subsurface drainage systems have been used for centuries. They have many forms that are similar in design and function to the traditional French drain. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry and crystallography, crystal structures that have the same set of interatomic distances are called homometric structures. Homometric structures need not be congruent (that is, related by a rigid motion or reflection). Homometric crystal structures produce identical diffraction patterns; therefore, they cannot be distinguished by a diffraction experiment.
Recently, a Monte Carlo algorithm was proposed to calculate the number of homometric structures corresponding to any given set of interatomic distances. | 0 | Theoretical and Fundamental Chemistry |
Endangered animal species and breeds are preserved using similar techniques. Animal species can be preserved in genebanks, which consist of cryogenic facilities used to store living sperm, eggs, or embryos. For example, the Zoological Society of San Diego has established a "frozen zoo" to store such samples using cryopreservation techniques from more than 355 species, including mammals, reptiles, and birds.
A potential technique for aiding in reproduction of endangered species is interspecific pregnancy, implanting embryos of an endangered species into the womb of a female of a related species, carrying it to term. It has been carried out for the Spanish ibex. | 1 | Applied and Interdisciplinary Chemistry |
Termination finishes of nickel, gold or palladium have been shown to eliminate whisker formation in controlled trials. | 1 | Applied and Interdisciplinary Chemistry |
Sodium dithiophosphate is the salt with the formula NaPSO. It is usually supplied as the hydrated solid or as an aqueous solution together with other thiophosphates such as sodium monothiophosphate and sodium trithiophosphate. It is a colorless compound, but commercial samples can appear dark owing to the presence of impurities. It is used to facilitate the isolation of molybdenum from its ores. | 1 | Applied and Interdisciplinary Chemistry |
Perfluorocarbons dissolve relatively high volumes of gases. The high solubility of gases is attributed to the weak intermolecular interactions in these fluorocarbon fluids.
The table shows values for the mole fraction, , of nitrogen dissolved, calculated from the Blood–gas partition coefficient, at 298.15 K (25 °C), 0.101325 MPa. | 1 | Applied and Interdisciplinary Chemistry |
GnRH is released by the hypothalamus in a pulsatile fashion; this causes the anterior pituitary gland to release luteinizing hormone (LH) and follicle-stimulating hormone (FSH). LH stimulates the testes to produce testosterone, which is metabolized to DHT by the enzyme 5α-reductase.
DHT, and to a significantly smaller extent, testosterone, stimulate prostate cancer cells to grow. Therefore, blocking these androgens can provide powerful treatment for prostate cancer, especially metastatic disease. Normally administered are GnRH analogues, such as leuprorelin or cetrorelix. Although GnRH agonists stimulate the same receptors that GnRH does, since they are present continuously and not in a pulsatile manner, they serve to inhibit the pituitary gland and therefore block the whole chain. However, they initially cause a surge in activity; this is not solely a theoretical risk but may cause the cancer to flare. Flutamide was initially used at the beginning of GnRH agonist therapy to block this surge, and it and other NSAAs continue in this use. In contrast to GnRH agonists, GnRH antagonists don't cause an initial androgen surge, and are gradually replacing GnRH agonists in clinical use.
There have been studies to investigate the benefit of adding an antiandrogen to surgical orchiectomy or its continued use with a GnRH analogue (combined androgen blockade (CAB)). Adding antiandrogens to orchiectomy showed no benefit, while a small benefit was shown with adding antiandrogens to GnRH analogues.
Unfortunately, therapies which lower testosterone levels, such as orchiectomy or GnRH analogue administration, also have significant side effects. Compared to these therapies, treatment with antiandrogens exhibits "fewer hot flashes, less of an effect on libido, less muscle wasting, fewer personality changes, and less bone loss." However, antiandrogen therapy alone is less effective than surgery. Nevertheless, given the advanced age of many with prostate cancer, as well as other features, many men may choose antiandrogen therapy alone for a better quality of life.
Flutamide has been found to be similarly effective in the treatment of prostate cancer to bicalutamide, although indications of inferior efficacy, including greater compensatory increases in testosterone levels and greater reductions in PSA levels with bicalutamide, were observed. The medication, at a dosage of 750 mg/day (250 mg three times daily), has also been found to be equivalent in effectiveness to 250 mg/day oral cyproterone acetate as a monotherapy in the treatment of prostate cancer in a large-scale clinical trial of 310 patients, though its side effect and toxicity profiles (including gynecomastia, diarrhea, nausea, loss of appetite, and liver disturbances) were regarded as considerably worse than those of cyproterone acetate.
A dosage of 750 mg/day flutamide (250 mg/three times a day) is roughly equivalent in terms of effectiveness to 50 mg/day bicalutamide when used as the antiandrogen component in combined androgen blockade in the treatment of advanced prostate cancer.
Flutamide has been used to prevent the effects of the testosterone flare at the start of GnRH agonist therapy in men with prostate cancer.
The combination of flutamide with an estrogen such as ethinylestradiol sulfonate has been used as a form of combined androgen blockade and as an alternative to the combination of flutamide with surgical or medical castration. | 0 | Theoretical and Fundamental Chemistry |
Volumetric flow rate can also be defined by
where
: = flow velocity,
: = cross-sectional vector area/surface.
The above equation is only true for uniform or homogeneous flow velocity and a flat or planar cross section. In general, including spatially variable or non-homogeneous flow velocity and curved surfaces, the equation becomes a surface integral:
This is the definition used in practice. The area required to calculate the volumetric flow rate is real or imaginary, flat or curved, either as a cross-sectional area or a surface. The vector area is a combination of the magnitude of the area through which the volume passes through, , and a unit vector normal to the area, . The relation is . | 1 | Applied and Interdisciplinary Chemistry |
In 1915, the reason for nuclear charge being quantized in units of Z, which were now recognized to be the same as the element number, was not understood. An old idea called Prouts hypothesis had postulated that the elements were all made of residues (or "protyles") of the lightest element hydrogen, which in the Bohr-Rutherford model had a single electron and a nuclear charge of one. However, as early as 1907, Rutherford and Thomas Royds had shown that alpha particles, which had a charge of +2, were the nuclei of helium atoms, which had a mass four times that of hydrogen, not two times. If Prouts hypothesis were true, something had to be neutralizing some of the charge of the hydrogen nuclei present in the nuclei of heavier atoms.
In 1917, Rutherford succeeded in generating hydrogen nuclei from a nuclear reaction between alpha particles and nitrogen gas, and believed he had proven Prout's law. He called the new heavy nuclear particles protons in 1920 (alternate names being proutons and protyles). It had been immediately apparent from the work of Moseley that the nuclei of heavy atoms have more than twice as much mass as would be expected from their being made of hydrogen nuclei, and thus there was required a hypothesis for the neutralization of the extra protons presumed present in all heavy nuclei. A helium nucleus was presumed to be composed of four protons plus two "nuclear electrons" (electrons bound inside the nucleus) to cancel two of the charges. At the other end of the periodic table, a nucleus of gold with a mass 197 times that of hydrogen was thought to contain 118 nuclear electrons in the nucleus to give it a residual charge of +79, consistent with its atomic number. | 0 | Theoretical and Fundamental Chemistry |
One major use of CFCs has been as propellants of aerosols, including metered-dose inhalers for drugs used to treat asthma. The conversion of these devices and treatments from CFC to propellants that do not deplete the ozone layer is almost complete. Production and import is now banned in the United States. | 1 | Applied and Interdisciplinary Chemistry |
Tris(tert-butoxy)silanethiol is a silicon compound containing three tert-butoxy groups and a rare Si–S–H functional group. This colourless compound serves as an hydrogen donor in radical chain reactions. It was first prepared by alcoholysis of silicon disulfide and purified by distillation:
:3 (CH)COH + SiS → [(CH)CO]SiSH + HS
Since 1962 it was thoroughly studied including its acid-base properties and coordination chemistry with metal ions. It coordinates to metal ions via the sulfur and oxygen donor atoms. | 0 | Theoretical and Fundamental Chemistry |
Increasing agricultural development is associated with the trend of elevated nitrogen concentrations in surrounding soil and groundwater composition due to the runoff of fertilizers and agricultural byproducts. Development of a submerged microbial desalination-denitrification cell (SMDDC) to remove nitrogen and saline from subsurface water alleviates the demand for additional compounds acting as electron donors and instead produces both a net energy and clean, desalinated and denitrified water. In contrast to the typical MDC model, the SMDDC excludes a middle desalination chamber, but instead only contains an anode and cathode chamber separated by a polycarbonate plate and are parallel to the exterior AEM and CEM respectively. Nitrate is introduced through the AEM into the anode chamber through synthetic groundwater, then propagated as an effluent through the external loop to the cathode chamber, in which nitrate is reduced to nitrogen by the cathode and sodium influent. A wastewater feeding tank pumps water to the anodic chamber for subsequent oxidation of sludge by the anodic biofilm. Similar to the original configuration of the MDC, the SMDDC also includes an external circuit in which electrons are thus freed from the oxidation process of the sludge and drove through a closed, external circuit to the cathodic chamber. The toxic and pathogenic content of the wastewater are thus separated simultaneously with the denitrification of the groundwater, producing water that is thus filtered out as a usable effluent. Highest nitrate removal was exhibited when an external voltage (0.8 V) was applied to the circuit, transporting the ions to the anodic chamber and reducing nitrate via heterotrophic denitrification. | 0 | Theoretical and Fundamental Chemistry |
One example of gamma ray production due to radionuclide decay is the decay scheme for cobalt-60, as illustrated in the accompanying diagram. First, decays to excited by beta decay emission of an electron of . Then the excited decays to the ground state (see nuclear shell model) by emitting gamma rays in succession of 1.17 MeV followed by . This path is followed 99.88% of the time:
Another example is the alpha decay of to form ; which is followed by gamma emission. In some cases, the gamma emission spectrum of the daughter nucleus is quite simple, (e.g. /) while in other cases, such as with (/ and /), the gamma emission spectrum is complex, revealing that a series of nuclear energy levels exist. | 0 | Theoretical and Fundamental Chemistry |
Thomas Albrecht-Schönzart is an American radiochemist specializing in the chemistry and physics of transuranium elements. He is jointly appointed as a University Distinguished Professor at the Colorado School of Mines in Golden, Colorado, and Director of the Nuclear Science & Engineering Center and Idaho National Laboratory. | 0 | Theoretical and Fundamental Chemistry |
Consider operators that obey the cyclic commutation relations
In fact only the first two relations are necessary for the following derivation, but since we are usually working with operators associated with Cartesian directions, such as the individual angular momentum operators, the third commutator follows by a symmetry argument.
Introduce also the commutation superoperator of an operator (in our case, this is more formally related to the adjoint representation of the Lie algebra whose elements are ), which acts as
In particular, for the cyclic operators, we have
and consequently for integer
An identity for two operators is
which can be derived by putting where is a scalar parameter, differentiating both sides with respect to , and noting that both sides satisfy the same differential equation in that parameter, with the same initial condition at . In particular, for some scalar parameter , we have
where the final equality follows from recognising the Taylor series for sine and cosine. Now suppose that the density operator at time zero is , and it is allowed to freely evolve under the Hamiltonian where is some scalar. Using the results above, the density operator at some later time will be given by
The interpretation of this is that although nuclear spin angular momentum itself is not connected to rotations in three-dimensional space in the same way that angular momentum is, the evolution of the density operator can be viewed as rotations in an abstract space, in which the operators are the generators of rotations about the axes. An example of such a set of generators is just the spin operators themselves.
We now also introduce the arrow notation typically used in NMR, which writes the general evolution given above as the shorthand
With more specific reference to the radiofrequency pulses applied during NMR experiments, a hard pulse with tip angle around a direction is written as above the arrow and corresponds to taking as the rotation generator in Equation . When there is no ambiguity, the arrow label may be omitted, or be eg text instead.
Note that a more complicated calculation has now been reduced to a simpler procedure that requires no knowledge of the underlying quantum mechanics, especially since the subspaces of cyclic operators can be tabulated in advance. | 0 | Theoretical and Fundamental Chemistry |
Dedicated or partially dedicated GISAXS beamlines exist at most synchrotron light sources (for instance Advanced Light Source (ALS), Australian Synchrotron, APS, ELETTRA (Italy), Diamond (UK), ESRF, National Synchrotron Light Source II (NSLS-II), Pohang Light Source (South Korea), SOLEIL (France), Shanghai Synchrotron (PR China), SSRL
At neutron research facilities, GISANS is increasingly used, typically on small-angle (SANS) instruments or on reflectometers.
GISAS does not require any specific sample preparation other than thin film deposition techniques. Film thicknesses may range from a few nm to several 100 nm, and such thin films are still fully penetrated by the x-ray beam. The film surface, the film interior, as well as the substrate-film interface are all accessible. By varying the incidence angle the various contributions can be identified. | 0 | Theoretical and Fundamental Chemistry |
Metalloprisms are another common type of coordination cage. They can be assembled from planar modules linked with column-like ligands.
One illustrative synthesis starts with [(η-p-cymene)Ru(μ-tpt-κN)(μ-CHRO- κO)] using the linker of 2,4,6-tri(pyridine-4-yl)-1,3,5-triazine (tpt). Various guest molecules have been encapsulated in the hydrophobic cavity of metallaprisms. A few examples of guests are bioconjugate derivatives, metal complexes, and nitroaromatics. | 0 | Theoretical and Fundamental Chemistry |
The Le Bail method extracts intensities (I) from powder diffraction data. This is done in order to find intensities that are suitable to determine the atomic structure of a crystalline material and to refine the unit cell and has the added advantage of checking phase-purity. Generally, the intensities of powder diffraction data are complicated by overlapping diffraction peaks with similar d-spacings. For the Le Bail method, the unit cell and the approximate space group of the sample must be predetermined because they are included as a part of the fitting technique. The algorithm involves refining the unit cell, the profile parameters, and the peak intensities to match the measured powder diffraction pattern. It is not necessary to know the structural factor and associated structural parameters, since they are not considered in this type of analysis. Le Bail can be used to find phase transitions in high pressure and temperature experiments. It generally provides a quick method to refine the unit cell, which allows better experimental planning. Le Bail analysis provides a more reliable estimate for the intensities of allowed reflections for different crystal symmetries.
Crystallographic structural determination can be accomplished in multiple ways. Le Bail technique is relevant for diffraction studies that involve using a radiation source, which may be neutron or synchrotron, to collect a high resolution, high quality powder diffraction profile. Initially, peak positions are found in the data. Next, the pattern is indexed in order to determine the unit cell or lattice parameters. Then, space group determination follows based on symmetry and the presence or absence of certain reflections. Then, either Le Bail or Pawley technique may be used to extract intensities and refine the unit cell. | 0 | Theoretical and Fundamental Chemistry |
The gel is prepared by dissolving the agarose powder in an appropriate buffer, such as TAE or TBE, to be used in electrophoresis. The agarose is dispersed in the buffer before heating it to near-boiling point, but avoid boiling. The melted agarose is allowed to cool sufficiently before pouring the solution into a cast as the cast may warp or crack if the agarose solution is too hot. A comb is placed in the cast to create wells for loading sample, and the gel should be completely set before use.
The concentration of gel affects the resolution of DNA separation. The agarose gel is composed of microscopic pores through which the molecules travel, and there is an inverse relationship between the pore size of the agarose gel and the concentration – pore size decreases as the density of agarose fibers increases. High gel concentration improves separation of smaller DNA molecules, while lowering gel concentration permits large DNA molecules to be separated. The process allows fragments ranging from 50 base pairs to several mega bases to be separated depending on the gel concentration used. The concentration is measured in weight of agarose over volume of buffer used (g/ml). For a standard agarose gel electrophoresis, a 0.8% gel gives good separation or resolution of large 5–10kb DNA fragments, while 2% gel gives good resolution for small 0.2–1kb fragments. 1% gels is often used for a standard electrophoresis. High percentage gels are often brittle and may not set evenly, while low percentage gels (0.1-0.2%) are fragile and not easy to handle. Low-melting-point (LMP) agarose gels are also more fragile than normal agarose gel. Low-melting point agarose may be used on its own or simultaneously with standard agarose for the separation and isolation of DNA. PFGE and FIGE are often done with high percentage agarose gels. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, the no-slip condition is a boundary condition which enforces that at a solid boundary, a viscous fluid attains zero bulk velocity. This boundary condition was first proposed by Osborne Reynolds, who observed this behaviour while performing his influential pipe flow experiments. The form of this boundary condition is an example of a Dirichlet boundary condition.
In the majority of fluid flows relevant to fluids engineering, the no-slip condition is generally utilised at solid boundaries. This condition often fails for systems which exhibit non-Newtonian behaviour. Fluids which this condition fails includes common food-stuffs which contain a high fat content, such as mayonnaise or melted cheese. | 1 | Applied and Interdisciplinary Chemistry |
Although van der Waals postulated the intermolecular interaction in 1873, in 1894, Fischer built a philosophical root for supramolecular chemistry. He pointed out that enzyme-protein interactions behave in a "lock-and-key" manner. This interaction is the foundation to host-guest chemistry. With the deeper understanding of the non-covalent interactions, for example, the clear elucidation of DNA structure, chemists started to emphasize the importance of non-covalent interactions. In 1967, Charles J. Pedersen discovered crown ethers, which are ring-like structures capable of chelating certain metal ions. Then, in 1969, Jean-Marie Lehn discovered a class of molecules similar to crown ethers, called cryptands. After that, Donald J. Cram synthesized many variations to crown ethers, on top of separate molecules capable of selective interaction with certain chemicals. The three scientists were awarded the Nobel Prize in Chemistry in 1987 for "development and use of molecules with structure-specific interactions of high selectivity”. In 2016, Bernard L. Feringa, Sir J. Fraser Stoddart, and Jean-Pierre Sauvage were awarded the Nobel Prize in Chemistry, "for the design and synthesis of molecular machines".
Supramolecular chemistry refers to the chemical systems that contains discrete number chemical components. The strengths of the systems vary from the intermolecular forces to covalent bindings. The researchers mentioned above created and enlarged the area of host-guest interaction, one of the most important concepts of the supramolecular chemistry fields. There are two significant components in the host-guest interaction. One is the "host molecules", which usually have "pore-like" structure that is able to capture some other molecules. The other one is the "guest molecules", which are generally smaller than the host molecules, and capable of binding the host molecules. The driving forces of the interaction might vary in different cases, such as hydrophobic effect, chelate effect, van der Waals force, et al. Different bindings will provide variant properties for the materials, i.e., stimuli-responsiveness, self-healing, matrix rigidification. As a consequence, the host-guest interaction can be applied for self-healing materials, stimuli-responsive materials, room-temperature phosphorescence (RTP), improvement of mechanical properties, et al. The sizes of the host and guest molecules play an essential role in the interactions, and some typical examples of the host interactions will be discussed as follows.
Host–guest chemistry is a branch of supramolecular chemistry in which a host molecule binds a so-called guest molecule or ion. The two components of the complex interact by non-covalent forces, most commonly by hydrogen-bonding. Binding between host and guest can be highly selective, in which case the interaction is called molecular recognition. Often, a dynamic equilibrium exist between the unbound and the bound states:
:H ="host", G ="guest", HG ="host–guest complex"
The "host" component is often the larger molecule, and it encloses the smaller, "guest", molecule. In biological systems, the analogous terms of host and guest are commonly referred to as enzyme and substrate respectively. | 0 | Theoretical and Fundamental Chemistry |
The energy of the alpha particle emitted in alpha decay is mildly dependent on the half-life for the emission process, with many orders of magnitude differences in half-life being associated with energy changes of less than 50%, shown by the Geiger–Nuttall law.
The energy of alpha particles emitted varies, with higher energy alpha particles being emitted from larger nuclei, but most alpha particles have energies of between 3 and 7 MeV (mega-electron-volts), corresponding to extremely long and extremely short half-lives of alpha-emitting nuclides, respectively. The energies and ratios are often distinct and can be used to identify specific nuclides as in alpha spectrometry.
With a typical kinetic energy of 5 MeV; the speed of emitted alpha particles is 15,000 km/s, which is 5% of the speed of light. This energy is a substantial amount of energy for a single particle, but their high mass means alpha particles have a lower speed than any other common type of radiation, e.g. β particles, neutrons.
Because of their charge and large mass, alpha particles are easily absorbed by materials, and they can travel only a few centimetres in air. They can be absorbed by tissue paper or by the outer layers of human skin. They typically penetrate skin about 40 micrometres, equivalent to a few cells deep. | 0 | Theoretical and Fundamental Chemistry |
Synthetic analogues of the naturally occurring Fe–S clusters were first reported by Holm and coworkers. Treatment of iron salts with a mixture of thiolates and sulfide affords derivatives such as (EtN)FeS(SCHPh)]. | 0 | Theoretical and Fundamental Chemistry |
There are several ways to name the alkylthiols:
* The suffix -thiol is added to the name of the alkane. This method is nearly identical to naming an alcohol and is used by the IUPAC, e.g. CHSH would be methanethiol.
* The word mercaptan replaces alcohol in the name of the equivalent alcohol compound. Example: CHSH would be methyl mercaptan, just as CHOH is called methyl alcohol.
* The term sulfhydryl- or mercapto- is used as a prefix, e.g. mercaptopurine. | 0 | Theoretical and Fundamental Chemistry |
Bents rule is able to characterize molecule geometry with accuracy. Bents rule provides a reliable and robust framework for predicting the bond angles of molecules. Bents rule accuracy and precision in predicting the geometry of real-world molecules continues to demonstrate its credibility. Beyond bond angle prediction, Bents rule has some significant applications and is of considerable interest to chemists. Bent's rule can be applied to analyzing bonding interactions and molecular syntheses.
Bents rule can be used to predict which products are favored in an organic synthesis depending on the starting materials. Wang et. al. considered how the substituents affected the silabenzenes equilibrium and found that Bents rule played a significant role in the results. The study conducted by Wang et. al. demonstrates how Bents rule can be used to predict the route of a synthesis and the stability of products. Showing a similar application, Dubois et. al were able to justify some of their findings using Bents rule when they found a reaction to be irreversible. Both these studies show how Bents rule can be used to aid synthetic chemistry. Knowing how molecular geometry accurately due to Bents rule allows synthetic chemists to predict relative product stability. Additionally, Bents rule can help chemists choose their starting materials to drive the reaction towards a particular product. Hence, Bent's rule allows synthetic chemists to exert more control over reactions of interest. | 0 | Theoretical and Fundamental Chemistry |
Because T-RFLP relies on DNA extraction methods and PCR, the biases inherent to both will affect the results of the analysis. Also, the fact that only the terminal fragments are being read means that any two distinct sequences which share a terminal restriction site will result in one peak only on the electropherogram and will be indistinguishable. Indeed, when T-RFLP is applied on a complex microbial community the result is often a compression of the total diversity to normally 20-50 distinct peaks only representing each an unknown number of distinct sequences. Although this phenomenon makes the T-RFLP results easier to handle, it naturally introduces biases and oversimplification of the real diversity. Attempts to minimize (but not overcome) this problem are often done by applying several restriction enzymes and/ or labeling both primers with a different fluorescent dye. The inability to retrieve sequences from T-RFLP often leads to the need to construct and analyze one or more clone libraries in parallel to the T-RFLP analysis which adds to the effort and complicates analysis. The possible appearance of false (pseudo) T-RFs, as discussed above, is yet another drawback. To handle this researchers often only consider peaks which can be affiliated to sequences in a clone library. | 1 | Applied and Interdisciplinary Chemistry |
In conjunction with organosilicates, phosphonates are also used to treat "sudden oak death", which is caused by the fungus-like eukaryote Phytophthora ramorum. | 0 | Theoretical and Fundamental Chemistry |
In ventilation systems a jet fan, also known as an impulse or induction fan, ejects a stream of air which entrains ambient air along with it, in order to circulate the ambient air. The system takes up less space than conventional ventilation ducting and can significantly increase the rates of inflow of fresh air and expulsion of stale air. | 0 | Theoretical and Fundamental Chemistry |
The concept of micelles was introduced to describe the core-corona aggregates of small surfactant molecules, however it has also extended to describe aggregates of amphiphilic block copolymers in selective solvents. It is important to know the difference between these two systems. The major difference between these two types of aggregates is in the size of their building blocks. Surfactant molecules have a molecular weight which is generally of a few hundreds of grams per mole while block copolymers are generally one or two orders of magnitude larger. Moreover, thanks to the larger hydrophilic and hydrophobic parts, block copolymers can have a much more pronounced amphiphilic nature when compared to surfactant molecules.
Because of these differences in the building blocks, some block copolymer micelles behave like surfactant ones, while others do not. It is necessary therefore to make a distinction between the two situations. The former ones will belong to the dynamic micelles while the latter will be called kinetically frozen micelles. | 0 | Theoretical and Fundamental Chemistry |
The ouzo effect ( ), also known as the louche effect ( ) and spontaneous emulsification, is the phenomenon of formation of a milky oil-in-water emulsion when water is added to ouzo and other anise-flavored liqueurs and spirits, such as pastis, rakı, arak, sambuca and absinthe. Such emulsions occur with only minimal mixing and are highly stable. | 0 | Theoretical and Fundamental Chemistry |
In nature, the incorporation of a deoxyribonucleoside triphosphate (dNTP) into a growing DNA strand involves the formation of a covalent bond and the release of pyrophosphate and a positively charged hydrogen ion. A dNTP will only be incorporated if it is complementary to the leading unpaired template nucleotide. Ion semiconductor sequencing exploits these facts by determining if a hydrogen ion is released upon providing a single species of dNTP to the reaction.
Microwells on a semiconductor chip that each contain many copies of one single-stranded template DNA molecule to be sequenced and DNA polymerase are sequentially flooded with unmodified A, C, G or T dNTP. If an introduced dNTP is complementary to the next unpaired nucleotide on the template strand it is incorporated into the growing complementary strand by the DNA polymerase. If the introduced dNTP is not complementary there is no incorporation and no biochemical reaction. The hydrogen ion that is released in the reaction changes the pH of the solution, which is detected by an ISFET. The unattached dNTP molecules are washed out before the next cycle when a different dNTP species is introduced. | 1 | Applied and Interdisciplinary Chemistry |
Assisted by Lewis acid catalyst, Friedel-Crafts methylsulfonation of aryl ring can be achieved by MsO. In contrast to MsCl, either activated or deactivated benzene derivatives can form the corresponding sulfonatesin satisfactory yields with MsO.
Examples of aromatic sulfonation with MsO:
* Sulfonation of chlorobenzene resulted in addition of methylsulfonyl group at para and ortho positions (with respect to chloride), with a ratio of 2 to 1, respectively; while reaction with Meta-dichlorobenzene gave monosulfonylated product at C4 position.
* With sulfuric acid, di-aryl sulfones were synthesized. | 0 | Theoretical and Fundamental Chemistry |
The Chernobyl accident released a large amount of caesium isotopes which were dispersed over a wide area. Cs is an isotope which is of long-term concern as it remains in the top layers of soil. Plants with shallow root systems tend to absorb it for many years. Hence grass and mushrooms can carry a considerable amount of Cs, which can be transferred to humans through the food chain.
One of the best countermeasures in dairy farming against Cs is to mix up the soil by deeply ploughing the soil. This has the effect of putting the Cs out of reach of the shallow roots of the grass, hence the level of radioactivity in the grass will be lowered. Also the removal of top few centimeters of soil and its burial in a shallow trench will reduce the dose to humans and animals as the gamma rays from Cs will be attenuated by their passage through the soil. The deeper and more remote the trench is, the better the degree of protection.
Fertilizers containing potassium can be used to dilute cesium and limit its uptake by plants.
In livestock farming, another countermeasure against Cs is to feed to animals prussian blue. This compound acts as an ion-exchanger. The cyanide is so tightly bonded to the iron that it is safe for a human to consume several grams of prussian blue per day. The prussian blue reduces the biological half-life (different from the nuclear half-life) of the caesium. The physical or nuclear half-life of Cs is about 30 years. Caesium in humans normally has a biological half-life of between one and four months. An added advantage of the prussian blue is that the caesium which is stripped from the animal in the droppings is in a form which is not available to plants. Hence it prevents the caesium from being recycled. The form of prussian blue required for the treatment of animals, including humans is a special grade. Attempts to use the pigment grade used in paints have not been successful. | 0 | Theoretical and Fundamental Chemistry |
The essential requirements that samples and sample material must meet includes a description of the sample, what form of dissection was used, what processing method was done, whether the samples were frozen or fixed and how long did it take, and what sample conditions were used. It is also desirable to know the volume or mass of the sample that was processed for the qPCR. | 1 | Applied and Interdisciplinary Chemistry |
Mass can be represented as density times volume, and under most conditions, water can be considered incompressible (density does not depend on pressure). The mass fluxes across the boundaries then become volume fluxes (as are found in Darcy's law). Using Taylor series to represent the in and out flux terms across the boundaries of the control volume, and using the divergence theorem to turn the flux across the boundary into a flux over the entire volume, the final form of the groundwater flow equation (in differential form) is:
This is known in other fields as the diffusion equation or heat equation, it is a parabolic partial differential equation (PDE). This mathematical statement indicates that the change in hydraulic head with time (left hand side) equals the negative divergence of the flux (q) and the source terms (G). This equation has both head and flux as unknowns, but Darcys law relates flux to hydraulic heads, so substituting it in for the flux (q') leads to
Now if hydraulic conductivity (K) is spatially uniform and isotropic (rather than a tensor), it can be taken out of the spatial derivative, simplifying them to the Laplacian, this makes the equation
Dividing through by the specific storage (S), puts hydraulic diffusivity (α = K/S or equivalently, α = T/S) on the right hand side. The hydraulic diffusivity is proportional to the speed at which a finite pressure pulse will propagate through the system (large values of α lead to fast propagation of signals). The groundwater flow equation then becomes
Where the sink/source term, G, now has the same units but is divided by the appropriate storage term (as defined by the hydraulic diffusivity substitution). | 1 | Applied and Interdisciplinary Chemistry |
Léon-Albert Arnaud (15 February 1853 – 27 March 1915) was a French chemist born in Paris.
From 1872 he worked as an assistant in the laboratory of Michel Eugène Chevreul (1786–1889) at the Muséum national dhistoire naturelle. In 1883 he succeeded François Stanislas Cloez (1817–1883) as aide-naturaliste', and from 1890 to 1915 was chair of applied organic chemistry at the museum.
Arnaud was the first scientist to describe the chemical make-up of tariric acid, an extraction from the glucoside of the "tariri plant" found in Guatemala. He is also credited with isolating tanghinine, taken from Tanghinia venenifera; (family Apocynaceae), and in 1883 discovered a new alkaloid called cinchonamine. | 0 | Theoretical and Fundamental Chemistry |
A tube filled with a glucose phosphate broth is inoculated with a sterile transfer loop. The tube is incubated at for 2–5 days. After incubation, 2.5 ml of the medium are transferred to another tube. Five drops of the pH indicator methyl red is added to this tube. The tube is gently rolled between the palms to disperse the methyl red. | 0 | Theoretical and Fundamental Chemistry |
Electrically detected magnetic resonance (EDMR) is a materials characterisation technique that improves upon electron spin resonance. It involves measuring the change in electrical resistance of a sample when exposed to certain microwave frequencies. It can be used to identify very small numbers (down to a few hundred atoms) of impurities in semiconductors. | 0 | Theoretical and Fundamental Chemistry |
In practice, the term is usually used more specifically to indicate that non-carbon atoms have replaced carbon in the backbone of the molecular structure. Typical heteroatoms are nitrogen (N), oxygen (O), sulfur (S), phosphorus (P), chlorine (Cl), bromine (Br), and iodine (I), as well as the metals lithium (Li) and magnesium (Mg). | 0 | Theoretical and Fundamental Chemistry |
This section describes the surface coverage when the adsorbate is in liquid phase and is a binary mixture.
For ideal both phases no lateral interactions, homogeneous surface the composition of a surface phase for a binary liquid system in contact with solid surface is given by a classic Everett isotherm equation (being a simple analogue of Langmuir equation), where the components are interchangeable (i.e. "1" may be exchanged to "2") without change of equation form:
where the normal definition of multi-component system is valid as follows:
By simple rearrangement, we get
This equation describes competition of components "1" and "2". | 0 | Theoretical and Fundamental Chemistry |
Substrates for anabolism are mostly intermediates taken from catabolic pathways during periods of high energy charge in the cell. | 1 | Applied and Interdisciplinary Chemistry |
The effect of non-depolarizing neuromuscular-blocking drugs may be reversed with acetylcholinesterase inhibitors, neostigmine, and edrophonium, as commonly used examples. Of these, edrophonium has a faster onset of action than neostigmine, but it is unreliable when used to antagonize deep neuromuscular block. Acetylcholinesterase inhibitors increase the amount of acetylcholine in the neuromuscular junction, so a prerequisite for their effect is that the neuromuscular block is not complete, because in case every acetylcholine receptor is blocked then it does not matter how much acetylcholine is present.
Sugammadex is a newer drug for reversing neuromuscular block by rocuronium and vecuronium in general anaesthesia. It is the first selective relaxant binding agent (SRBA). | 1 | Applied and Interdisciplinary Chemistry |
Velocimetry has also been applied to medical images in order to obtain regional measurements of blood flow and tissue motion. Initially, standard PIV (single plane illumination) was adapted to work with x-ray images (full volume illumination), enabling the measurement of opaque flows such as blood flow. This was then extended to investigate the regional 2D motion of lung tissue, and was found to be a sensitive indicator of regional lung disease.
Velocimetry was also expanded to 3D regional measurements blood flow and tissue motion with a new technique – computed tomographic x-ray velocimetry – which uses information contained within the PIV cross-correlation to extract 3D measurements from 2D image sequences. Specifically, computed tomographic x-ray velocimetry generates a model solution, compares the cross-correlations of the model to the cross-correlation from the 2D image sequence, and iterates the model solution until the difference between the model cross-correlations and the image sequence cross-correlations are minimised. This technique is being used as a non invasive method to quantify functional performance of the lungs. It is being used in a clinical setting, and is being utilised in clinical trails conducted by institutions including Duke University, Vanderbilt University Medical Center and Oregon Health Science University | 1 | Applied and Interdisciplinary Chemistry |
Levonorgestrel is used in combination with an estrogen in menopausal hormone therapy. It is used under the brand name Klimonorm as a combined oral tablet with estradiol valerate and under the brand name Climara Pro as a combined transdermal patch with estradiol. | 0 | Theoretical and Fundamental Chemistry |
Alkalinity (from ) is the capacity of water to resist acidification. It should not be confused with basicity, which is an absolute measurement on the pH scale. Alkalinity is the strength of a buffer solution composed of weak acids and their conjugate bases. It is measured by titrating the solution with an acid such as HCl until its pH changes abruptly, or it reaches a known endpoint where that happens. Alkalinity is expressed in units of concentration, such as meq/L (milliequivalents per liter), μeq/kg (microequivalents per kilogram), or mg/L CaCO (milligrams per liter of calcium carbonate). Each of these measurements corresponds to an amount of acid added as a titrant.
In freshwater, particularly those on non-limestone terrains, alkalinities are low and involve a lot of ions. In the ocean, on the other hand, alkalinity is completely dominated by carbonate and bicarbonate plus a small contribution from borate.
Although alkalinity is primarily a term used by limnologists and oceanographers, it is also used by hydrologists to describe temporary hardness. Moreover, measuring alkalinity is important in determining a streams ability to neutralize acidic pollution from rainfall or wastewater. It is one of the best measures of the sensitivity of the stream to acid inputs. There can be long-term changes in the alkalinity of streams and rivers in response to human disturbances such as acid rain generated by SO and NO emissions. | 0 | Theoretical and Fundamental Chemistry |
It is well documented that (R)-enantiomers of profens in the presence of coenzyme A (CoA), adenosine triphosphate (ATP) and Mg are converted to active (S)-forms. The pathways of chiral inversion is illustrated taking ibuprofen as the prototype, in the scheme below.
The pathway consists mainly of three steps:
# Stereoselective activation: Stereoselective activation of (R)-profen by the formation of the thioester, in the presence of CoA, ATP and Mg. (S)-profen does not form the thioester.
# Epimerization (Racemization): The enzyme epimerase 2-arylpropionic-CoA changes the (R)-thioester to the (S)-thioester. This process is called "racemization" or "epimerization."
# Hydrolysis: With the help of hydrolase/thioesterase, thioesters are broken down into their (R)- and (S)-forms
Because the acyl-CoA thioester (profenyl-CoA) changes the structure of triglycerides and phospholipids, metabolic chiral inversion may cause toxic effects. | 0 | Theoretical and Fundamental Chemistry |
In autumn 1806, he was welcomed into the family home of Ørsted, where he was given a position as an Assistant, helping Ørsted prepare his university lectures. His stay with Ørsted lasted several years and was certainly of the greatest importance for his development. Ørsted himself recounted how he influenced Zeise through conversations and encouraged him when he expressed the desire to take the university entrance examination (Examen artium). Ørsted spoke fondly of Zeise's independent spirit. Zeise became a university student in 1809.
Zeise had at first intended to study medicine, but while attending lectures it became clear that his interests had a broader scientific base; and chemistry remained his favourite subject. He still experimented in Ørsteds Laboratory, but since at that time there was no prospect for a teaching position at the university, he took the pharmacist exam in 1815, later a masters degree (magisterkonferens) and on 21 October 1817 he defended his doctoral dissertation on The effect of Alkalies upon organic substances. The experimental part of this work he performed in a small laboratory, which in 1816 he had converted from the pharmacy in Slagelse.
As the university had no separate lecturing chair in chemistry and no scientific laboratory, Zeise decided to work and study abroad. In 1818 he managed to get travelling money. Zeise arrived in Göttingen, where he spent four months working in Friedrich Stromeyers laboratory, one of the few experimental laboratories in Germany at that time. He was trained particularly in analytical chemistry, in which he would become a great master. Zeise next spent nearly a year in Paris. His diary entries reflect how diligent he was, and depict vividly the impression he got of the famous French scientists he came in contact with. In August 1818, while in Paris, Zeise became personally acquainted with the distinguished Swedish chemist Jöns Jacob Berzelius. Berzelius received the young Danish chemist with great benevolence, expressing his admiration for Zeises Doctoral thesis. They continued a respectful friendship thereafter, despite Zeise being ten years younger than Berzelius. | 0 | Theoretical and Fundamental Chemistry |
Agarose gel electrophoresis is a method of gel electrophoresis used in biochemistry, molecular biology, genetics, and clinical chemistry to separate a mixed population of macromolecules such as DNA or proteins in a matrix of agarose, one of the two main components of agar. The proteins may be separated by charge and/or size (isoelectric focusing agarose electrophoresis is essentially size independent), and the DNA and RNA fragments by length. Biomolecules are separated by applying an electric field to move the charged molecules through an agarose matrix, and the biomolecules are separated by size in the agarose gel matrix.
Agarose gel is easy to cast, has relatively fewer charged groups, and is particularly suitable for separating DNA of size range most often encountered in laboratories, which accounts for the popularity of its use. The separated DNA may be viewed with stain, most commonly under UV light, and the DNA fragments can be extracted from the gel with relative ease. Most agarose gels used are between 0.7–2% dissolved in a suitable electrophoresis buffer. | 1 | Applied and Interdisciplinary Chemistry |
Philipp Kukura FRSC (born 26 March 1978) is Professor of Chemistry at the University of Oxford, and a Fellow of Exeter College, Oxford. He is best known for pioneering contributions to femtosecond stimulated Raman spectroscopy (FSRS), interferometric scattering microscopy (iSCAT) and the development of mass photometry. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, π backbonding is a π-bonding interaction between a filled (or half filled) orbital of a transition metal atom and a vacant orbital on an adjacent ion or molecule. In this type of interaction, electrons from the metal are used to bond to the ligand, which dissipates excess negative charge and stabilizes the metal. It is common in transition metals with low oxidation states that have ligands such as carbon monoxide, olefins, or phosphines. The ligands involved in π backbonding can be broken into three groups: carbonyls and nitrogen analogs, alkenes and alkynes, and phosphines. Compounds where π backbonding is prominent include Ni(CO), Zeise's salt, and molybdenym and iron dinitrogen complexes. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl group, or a sulfanyl group. Thiols are the sulfur analogue of alcohols (that is, sulfur takes the place of oxygen in the hydroxyl () group of an alcohol), and the word is a blend of "thio-" with "alcohol".
Many thiols have strong odors resembling that of garlic or rotten eggs. Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless), and the "smell of natural gas" is due to the smell of the thiol used as the odorant. Thiols are sometimes referred to as mercaptans () or mercapto compounds, a term introduced in 1832 by William Christopher Zeise and is derived from the Latin (capturing mercury) because the thiolate group () bonds very strongly with mercury compounds. | 0 | Theoretical and Fundamental Chemistry |
According to Aristotle, the Pre-Socratic Greek philosopher Anaxagoras had taught that every thing, and every portion of a thing, contains within itself an infinite number of like and unlike parts. For example, Anaxagoras maintained that there must be blackness as well as whiteness in snow; how, otherwise, could it be turned into dark water? Aristotle criticized Anaxagoras' theory on multiple grounds, among them the following:
*Animals and plants cannot be infinitely small according to Aristotle; thus the relatively homogeneous substances of which they are composed (e.g., bone and flesh in animals, or wood in plants) could not be infinitely small, either, but must have a smallest determinate size—i.e., a natural minimum.
*On Anaxagoras' argument in which all things contain all others infinitely, water could be drawn from flesh, then flesh from that water, and water from that flesh, and so on. However, as above, because there is a smallest determinate size beyond which a further divided substance would no longer be flesh, any further cycle of such drawings out would be impossible.
*Moreover, "[s]ince every body must diminish in size when something is taken from it, and flesh is quantitatively definite in respect both of greatness and smallness, it is clear that from the minimum quantity of flesh no body can be separated out; for the flesh left would be less than the minimum of flesh."
Unlike the atomism of Leucippus, Democritus, and Epicurus, and also unlike the later atomic theory of John Dalton, the Aristotelian natural minimum was not conceptualized as physically indivisible--"atomic" in the contemporary sense. Instead, the concept was rooted in Aristotles hylomorphic worldview, which held that every physical thing is a compound of matter (Greek hyle) and a substantial form (Greek morphe') that imparts its essential nature and structure. For instance, a rubber ball for a hylomorphist like Aristotle would be rubber (matter) structured by spherical shape (form).
Aristotle's intuition was that there is some smallest size beyond which matter could no longer be structured as flesh, or bone, or wood, or some other such organic substance that (for Aristotle, living before the microscope) could be considered homogeneous. For instance, if flesh were divided beyond its natural minimum, what would remain might be some elemental water, and smaller amounts of the other elements (e.g., earth) with which water was thought to mix to form flesh. But whatever was left, the water (or earth, etc.), would no longer have the formal "nature" of flesh in particular – the remaining matter would have the form of water (or earth, etc.) rather than the substantial form of flesh.
This is suggestive of modern chemistry, in which, e.g., a bar of gold can be continually divided until one has a single atom of gold, but further division of that atom of gold yields only subatomic particles (electrons, quarks, etc.) which are no longer the chemical element gold. Just as water alone is not flesh, electrons alone are not gold. | 1 | Applied and Interdisciplinary Chemistry |
Proton density (PD)- weighted images are created by having a long repetition time (TR) and a short echo time (TE). On images of the brain, this sequence has a more pronounced distinction between grey matter (bright) and white matter (darker grey), but with little contrast between brain and CSF. It is very useful for the detection of arthropathy and injury. | 0 | Theoretical and Fundamental Chemistry |
Material is put on a sinter machine in two layers. The bottom layer may vary in thickness from . A 12 to 20 mm sinter fraction is used, also referred to as the hearth layer. The second, covering layer consists of mixed materials, making for a total bed height of . The mixed materials are applied with drum feeders and roll feeders, which distributes the nodules in certain depth throughout the sinterring machine . The upper layer is smoothed using a leveler. The material, also known as a charge, enters the ignition furnace into rows of multi-slit burners. In the case of one plant, the first (ignition) zone has eleven burners. The next (soaking/annealing) zone typically offers 12 burners. Air is sucked from the bottom of the bed of mixed material throughout the sintering machine. Fire penetrates the mixed material gradually, until it reaches the hearth layer. This end point of burning is called burn through point (BTP). The hearth layer, which is nothing but sinter in smaller size, restricts sticking of hot sinter with pallets. BTP is achieved in a certain zone of sinter machine, to optimize the process, by means of several temperature measuring instrument placed throughout the sinter machine. After completion of burning, the mix converts into sinter, which then breaks into smaller size by sinter breaker. After breaking into small sizes, it cools down in cooler (linear or circular) by means of forced air. At discharge of sinter cooler, temperature of sinter is maintained as low, so that the hot sinter can be transported by a conveyor belt made of rubber. Necessary precautions are taken to trace any existence of fire in the belt and necessary extinguishing is done by spraying water. Then this product is being passed through a jaw-crusher, where the size of sinter is further reduced (~ 50 mm) into smaller size. Then the complete mixture is being passed through two screens. Smallest sinter fines (< 5 mm) are stored in proportioning bins and reused for preparing sinter again through mixing and nodulizing drum and fed to sinter machine for burning. A part of the smaller one ( 5 – 20 mm) is used for hearth layer in sinter machine and the rest is taken to the blast furnace along with the biggest sized sinters.
The temperature is typically maintained between in the ignition zone and between 900 and 1000 °C in the soaking zone to prevent sudden quenching of the sintered layer. The top 5 mm from screens goes to the conveyor carrying the sinter for the blast furnace and, along with blast furnace grade sinter, either goes to sinter storage bunkers or to BF bunkers. Blast furnace-grade sinter consists of particles sized 5 to 12 mm as well as 20 mm and above. | 1 | Applied and Interdisciplinary Chemistry |
A wide variety of enantioselective additions employing chiral, non-racemic Lewis acids are known. The chiral (acyloxy)borane or "CAB" catalyst 1, titanium-BINOL system 2, and silver-BINAP system 3 provide addition products in high ee via the Lewis-acid-promoted mechanism described above. | 0 | Theoretical and Fundamental Chemistry |
Without loss of generality taken at the origin and . Then the fundamental tensor and vector are
where
where is the modified Bessel function of the second kind of order zero. | 1 | Applied and Interdisciplinary Chemistry |
The nuclear protein in testis gene (i.e. NUTM1 gene) encodes (i.e. directs the synthesis of) a 1,132-amino acid protein termed NUT that is expressed almost exclusively in the testes, ovaries, and ciliary ganglion (i.e. a parasympathetic ganglion of nerve cells located just behind the eye). NUT protein facilitates the acetylation of chromatin (i.e. DNA-protein bundles) by histone acetyltransferase EP300 in testicular spermatids (cells that mature into sperms). This acetylation is a form of chromatin remodeling which compacts spermatid chromatin, a critical step required for the normal conduct of spermatogenesis, i.e. the maturation of spermatids into sperm. Male mice that lacked the mouse Nutm1 gene using a gene knockout method had abnormally small testes, lacked sperm in their cauda epididymis (i.e. tail of the epididymis which contains sperm in fertile male mice), and were completely sterile. These findings indicate that Nutm1 gene is essential for the development of normal fertility in male mice and suggest that the NUTM1 gene may play a similar role in men.
The NUTM1 gene is located in band 14 on the long (or "q") arm of chromosome 15. In the early 1990s, this gene was implicated in the development of certain epithelial cell cancers that: a) occurred in the midline structures of young people, b) were rapidly fatal, and c) consisted of poorly differentiated (i.e. not resembling any particular cell type), immature-appearing cells containing a BRD4-NUTM1 fusion gene. BRD4 is the bromodomain-containing protein 4 gene. A fusion gene is an abnormal gene consisting of parts from two different genes that form as a result of a large scale gene mutation such as a chromosomal translocation, interstitial deletion, or inversion. The BRD4-NUTM1 fusion gene is a translocation that encodes a fusion protein that has merged most of the protein coding region of the NUTM1 gene with a large part of the BRD4 gene located in band 13 on the short (i.e. "q") arm of chromosome 19. This translocation is notated as t(15;19)(q13, p13.1).
BRD4 protein recognizes acetylated lysine residues on proteins and by doing so participates in the regulation of DNA replication, DNA transcription, and thereby key cellular processes involved in the development of neoplasms (i.e. malignant or benign tissue growths). The product of the BRD4-NUTM1 fusion gene, BRD4-NUT protein, stimulates the expression of at least 4 relevant genes, MYC, TP63, SOX2, and MYB in cultured cells. All four of these genes are oncogenes, i.e., genes that when overexpressed and/or overly active promote the development of certain types of cancers. Overexpression of the MYC and SOX2 genes can also act to maintain cells in an undifferentiated stem cell-like state similar to the cells in the neoplasms driven by the BRD4-NUTM1 fusion gene. It is generally accepted that the BRD4-NUT protein promotes these neoplasms by maintaining their neoplastic cells in a perpetually undifferentiated, proliferative state. Further studies are needed to confirm and expand these views and to determine if any of the overexpressed gene products of the BRD4-NUT protein contribute to the development and/or progression, or can serve as targets for the treatment, of the neoplasms associated with the BRD4-NUTM1 fusion gene. These questions also apply to a wide range of neoplasms that have more recently been associated with the NUTM1 gene fused to other genes. | 1 | Applied and Interdisciplinary Chemistry |
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