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In nickel-based superalloys, regions of NiAl (called γ' phase) precipitate out of the nickel-rich matrix (called γ phase) to give high strength and creep resistance. Many alloy formulations are available and they usually include other elements, such as chromium, molybdenum, and iron, in order to improve various properties. | 8 | Metallurgy |
The safety of ketosis from low-carbohydrate diets is often called into question by clinicians, researchers and the media. A common safety concern stems from the misunderstanding of the difference between physiological ketosis and pathologic ketoacidosis. There is also continued debate whether chronic ketosis is a healthy state or a stressor to be avoided. Some argue that humans evolved to avoid ketosis and should not be in ketosis long-term. The counter-argument is that there is no physiological requirement for dietary carbohydrate as adequate energy can be made via gluconeogenesis and ketogenesis indefinitely. Alternatively, the switching between a ketotic and fed state has been proposed to have beneficial effects on metabolic and neurologic health. The effects of sustaining ketosis for up to two years are known from studies of people following a strict ketogenic diet for epilepsy or type 2 diabetes; these include short-term adverse effects leading to potential long-term ones. However, literature on longer term effects of intermittent ketosis is lacking. | 1 | Biochemistry |
Most alkenes are prochiral, meaning in this context that their hydrocyanation generates chiral nitriles. Conventional hydrocyanation catalysts, e.g. , catalyse the formation of racemic mixtures. When however the supporting ligands are chiral, the hydrocyanation can be highly enantioselective. For asymmetric hydrocyanation, popular chiral ligands are chelating aryl diphosphite complexes. | 0 | Organic Chemistry |
In a two-dimensional isotropic material the grain boundary tension would be the same for the grains. This would give angle of 120° at GB junction where three grains meet. This would give the structure a hexagonal pattern which is the metastable state (or mechanical equilibrium) of the 2D specimen. A consequence of this is that, to keep trying to be as close to the equilibrium as possible, grains with fewer sides than six will bend the GB to try keep the 120° angle between each other. This results in a curved boundary with its curvature towards itself. A grain with six sides will, as mentioned, have straight boundaries, while a grain with more than six sides will have curved boundaries with its curvature away from itself. A grain with six boundaries (i.e. hexagonal structure) is in a metastable state (i.e. local equilibrium) within the 2D structure. In three dimensions structural details are similar but much more complex and the metastable structure for a grain is a non-regular 14-sided polyhedra with doubly curved faces. In practice all arrays of grains are always unstable and thus always grow until prevented by a counterforce.
Grains strive to minimize their energy, and a curved boundary has a higher energy than a straight boundary. This means that the grain boundary will migrate towards the curvature. The consequence of this is that grains with less than 6 sides will decrease in size while grains with more than 6 sides will increase in size.
Grain growth occurs due to motion of atoms across a grain boundary. Convex surfaces have a higher chemical potential than concave surfaces, therefore grain boundaries will move toward their center of curvature. As smaller particles tend to have a higher radius of curvature and this results in smaller grains losing atoms to larger grains and shrinking. This is a process called Ostwald ripening. Large grains grow at the expense of small grains.
Grain growth in a simple model is found to follow:
Here G is final average grain size, G is the initial average grain size, t is time, m is a factor between 2 and 4, and K is a factor given by:
Here Q is the molar activation energy, R is the ideal gas constant, T is absolute temperature, and K is a material dependent factor. In most materials the sintered grain size is proportional to the inverse square root of the fractional porosity, implying that pores are the most effective retardant for grain growth during sintering. | 8 | Metallurgy |
In Canada, hash oil – defined as a chemically concentrated extract having up to 90% THC potency – was approved for commerce in October 2018.
In the United States, regulations specifically for hash oil have not been issued as of 2019, but hemp seed oil – along with hulled hemp seeds and hemp seed protein – were approved as generally recognized as safe (GRAS) in December 2018, indicating that "these products can be legally marketed in human foods for these uses without food additive approval, provided they comply with all other requirements and do not make disease treatment claims". | 7 | Physical Chemistry |
Mechanical lysis involves the use of physical force, such as grinding or sonication, to break down bacterial cells and release the plasmid DNA. There are several different mechanical lysis methods that can be used, including French press, bead-beating, and ultrasonication. | 1 | Biochemistry |
EDC couples primary amines, and other nucleophiles, to carboxylic acids by creating an activated ester leaving group. First, the carbonyl of the acid attacks the carbodiimide of EDC, and there is a subsequent proton transfer. The primary amine then attacks the carbonyl carbon of the acid which forms a tetrahedral intermediate before collapsing and discharging the urea byproduct. The desired amide is obtained. | 1 | Biochemistry |
;Novartis-Drew Award
*2003: Elaine Fuchs; Philip A. Sharp; David Botstein
*2002: Frank McCormick; Brian J. Druker; Harold Varmus
*2001: Sidney Brenner; Eric Lander; Craig Venter
*2000: Susan L. Lindquist
*1999: Elizabeth Helen Blackburn; Joan Steitz
*1998: Tom Maniatis; Alexander Varshavsky
*1997: Edward Alan Berger
;Ciba-Drew Award
*1996: H. Robert Horvitz; Stanley J. Korsmeyer
*1995: Joseph Schlessinger; Günter Blobel ; Arnold J. Levine
*1994: Thomas R. Cech; Albert Eschenmoser; Manfred Eigen
*1993: Leroy Hood; Francis S. Collins
*1992: Stuart L. Schreiber ; Peter G. Schultz ; Richard Lerner
*1991: Sir Michael Berridge
*1990: Roger David Kornberg; Nicholas R. Cozzarelli
*1989: Robert William Mahley
*1988: Samuel Broder; Robert C. Gallo ; Luc Montagnier
*1987: Thomas A. Waldmann
*1986: Michael H. Wigler
*1985: Jean-Pierre Changeux; Solomon Halbert Snyder
*1984: Albrecht Fleckenstein; Harald Reuter
*1983: Ronald Levy;
*1981: C. Ronald Kahn; Donald F. Steiner ; Sydney Brenner
*1980: Bengt I. Samuelsson; John Robert Vane
*1979: Paul Greengard
*1977: Robert C. Gallo; Fred Rapp | 1 | Biochemistry |
In homogeneous catalysis, C-symmetric ligands refer to ligands that lack mirror symmetry but have C symmetry (two-fold rotational symmetry). Such ligands are usually bidentate and are valuable in catalysis. The C symmetry of ligands limits the number of possible reaction pathways and thereby increases enantioselectivity, relative to asymmetrical analogues. C-symmetric ligands are a subset of chiral ligands. Chiral ligands, including C-symmetric ligands, combine with metals or other groups to form chiral catalysts. These catalysts engage in enantioselective chemical synthesis, in which chirality in the catalyst yields chirality in the reaction product. | 4 | Stereochemistry |
Especially in proteins, electron transfer often involves hopping of an electron from one redox-active center to another. The hopping pathway, which is viewed as a vector, guides and facilitates ET within an insulating matrix. Typical redox centers are iron-sulfur clusters, e.g. the 4Fe-4S ferredoxins. These site are often separated by 7-10 Å, a distance compatible with fast outer-sphere ET. | 7 | Physical Chemistry |
Still another type of photochemical reaction is the di--methane rearrangement. Two further early examples were the rearrangement of 1,1,5,5-tetraphenyl-3,3-dimethyl-1,4-pentadiene (the "Mariano" molecule) and the rearrangement of barrelene to semibullvalene. We note that, in contrast to the cyclohexadienone reactions which used n-* excited states, the di--methane rearrangements utilize -* excited states. | 5 | Photochemistry |
Ted Ellis (born 1963) is an American artist and former environmental chemist. Ellis is best known for his African-American themed art and styles which blend elements of folk art, naturalism and impressionism. His personal rendition of Barack Obama in acrylic, Obama, the 44th President, was presented in honor of the 2009 Presidential Inauguration.
Ellis art business has sold over 1.75 million fine art products, and he works with a number of prominent corporations. He is also known for his community work, especially advancing arts in childrens education. | 3 | Analytical Chemistry |
Plastocyanin (CuPc) is reduced (an electron is added) by cytochrome f according to the following reaction:
:CuPc + e → CuPc
After dissociation, CuPc diffuses through the lumen space until recognition/binding occurs with P700, at which point P700 oxidizes CuPc according to the following reaction:
:CuPc → CuPc + e
The redox potential is about 370 mV and the isoelectric pH is about 4. | 5 | Photochemistry |
In contrast to most fresh-water sources, iron levels in surface sea-water are extremely low (1 nM to 1 μM in the upper 200 m) and much lower than those of V, Cr, Co, Ni, Cu and Zn. Virtually all this iron is in the iron(III) state and complexed to organic ligands. These low levels of iron limit the primary production of phytoplankton and have led to the Iron Hypothesis where it was proposed that an influx of iron would promote phytoplankton growth and thereby reduce atmospheric CO. This hypothesis has been tested on more than 10 different occasions and in all cases, massive blooms resulted. However, the blooms persisted for variable periods of time. An interesting observation made in some of these studies was that the concentration of the organic ligands increased over a short time span in order to match the concentration of added iron, thus implying biological origin and in view of their affinity for iron possibly being of a siderophore or siderophore-like nature. Significantly, heterotrophic bacteria were also found to markedly increase in number in the iron-induced blooms. Thus there is the element of synergism between phytoplankton and heterotrophic bacteria. Phytoplankton require iron (provided by bacterial siderophores), and heterotrophic bacteria require non-CO carbon sources (provided by phytoplankton).
The dilute nature of the pelagic marine environment promotes large diffusive losses and renders the efficiency of the normal siderophore-based iron uptake strategies problematic. However, many heterotrophic marine bacteria do produce siderophores, albeit with properties different from those produced by terrestrial organisms. Many marine siderophores are surface-active and tend to form molecular aggregates, for example aquachelins. The presence of the fatty acyl chain renders the molecules with a high surface activity and an ability to form micelles. Thus, when secreted, these molecules bind to surfaces and to each other, thereby slowing the rate of diffusion away from the secreting organism and maintaining a relatively high local siderophore concentration. Phytoplankton have high iron requirements and yet the majority (and possibly all) do not produce siderophores. Phytoplankton can, however, obtain iron from siderophore complexes by the aid of membrane-bound reductases and certainly from iron(II) generated via photochemical decomposition of iron(III) siderophores. Thus a large proportion of iron (possibly all iron) absorbed by phytoplankton is dependent on bacterial siderophore production. | 1 | Biochemistry |
In the ovary, the FSH receptor is necessary for follicular development and expressed on the granulosa cells.
In the male, the FSH receptor has been identified on the Sertoli cells that are critical for spermatogenesis.
The FSHR is expressed during the luteal phase in the secretory endometrium of the uterus.
FSH receptor is selectively expressed on the surface of the blood vessels of a wide range of carcinogenic tumors. | 1 | Biochemistry |
Butter yellow was synthesized by Peter Griess in the 1860s at the Royal College of Chemistry in London. The dye was used to dye butter in Germany and other parts of the world during the latter half of the 19th century and the beginning of the 20th before being phased out in the 1930s and 40s. It was in the 1930s that research led by Riojun Kinosita showed the link between several azo dyes and cancer, linking butter yellow to liver cancer in rats after two to three months exposure. In 1939, the International Congress for Cancer Research issued a recommendation for the banning of cancer-causing food dyes (including butter yellow) from food production.
In 2014, dried tofu products (a.k.a. dougan 豆乾) from Taiwan were found to have been adulterated with methyl yellow, used as a coloring agent. | 3 | Analytical Chemistry |
# Magnetic materials e.g. alnico, sendust, Permendur, FeCo, Terfenol-D
# Superconductors e.g. A15 phases, niobium-tin
# Hydrogen storage e.g. AB compounds (nickel metal hydride batteries)
# Shape memory alloys e.g. Cu-Al-Ni (alloys of CuAl and nickel), Nitinol (NiTi)
# Coating materials e.g. NiAl
# High-temperature structural materials e.g. nickel aluminide, NiAl
# Dental amalgams, which are alloys of intermetallics AgSn and CuSn
# Gate contact/ barrier layer for microelectronics e.g. TiSi
# Laves phases (AB), e.g., MgCu, MgZn and MgNi.
The formation of intermetallics can cause problems. For example, intermetallics of gold and aluminium can be a significant cause of wire bond failures in semiconductor devices and other microelectronics devices. The management of intermetallics is a major issue in the reliability of solder joints between electronic components. | 8 | Metallurgy |
Jelly-falls are marine carbon cycling events whereby gelatinous zooplankton, primarily cnidarians, sink to the seafloor and enhance carbon and nitrogen fluxes via rapidly sinking particulate organic matter. These events provide nutrition to benthic megafauna and bacteria. Jelly-falls have been implicated as a major “gelatinous pathway” for the sequestration of labile biogenic carbon through the biological pump. These events are common in protected areas with high levels of primary production and water quality suitable to support cnidarian species. These areas include estuaries and several studies have been conducted in fjords of Norway. | 9 | Geochemistry |
Many additional tests have since been run to apply and compare Hoffman's principles to reality. Among the experiments done, some of the more notable secondary nucleation tests are briefly explained in the table below. | 7 | Physical Chemistry |
The Calvin cycle starts by using the enzyme RuBisCO to fix CO into five-carbon Ribulose bisphosphate (RuBP) molecules. The result is unstable six-carbon molecules that immediately break down into three-carbon molecules called 3-phosphoglyceric acid, or 3-PGA.
The ATP and NADPH made in the light reactions is used to convert the 3-PGA into glyceraldehyde-3-phosphate, or G3P sugar molecules. Most of the G3P molecules are recycled back into RuBP using energy from more ATP, but one out of every six produced leaves the cycle—the end product of the dark reactions. | 5 | Photochemistry |
Once correctly positioned in the membrane via binding of PIP3, Akt can then be phosphorylated by its activating kinases, phosphoinositide-dependent kinase 1 (PDK1) and PDK2. Serine473, the hydrophobic motif, is phosphorylated in an mTORC2-dependent manner, leading some investigators to hypothesize that mTORC2 is the long-sought PDK2 molecule. Threonine308, the activation loop, is phosphorylated by PDK1, allowing full Akt activation. Activated Akt can then go on to activate or deactivate its myriad substrates via its kinase activity. The PHLPPs therefore antagonize PDK1 and PDK2, since they dephosphorylate the site that PDK2 phosphorylates. | 1 | Biochemistry |
The term ‘secondary building unit’ has been used for some time to describe conceptual fragments which can be compared as bricks used to build a house of zeolites; in the context of this page it refers to the geometry of the units defined by the points of extension. | 6 | Supramolecular Chemistry |
Lynette Cegelski is an American physical chemist and chemical biologist who studies extracellular structures such as biofilms and membrane proteins. She is an associate professor of chemistry and, by courtesy, of chemical engineering at Stanford University. She is a Stanford Bio-X and Stanford ChEM-H affiliated faculty member. | 7 | Physical Chemistry |
Zeba Islam Seraj is a Bangladeshi scientist known for her research in developing salt-tolerant rice varieties suitable for growth in the coastal areas of Bangladesh. She is currently a professor at the Department of Biochemistry and Molecular Biology, University of Dhaka. | 1 | Biochemistry |
Armstrong's acid (naphthalene-1,5-disulfonic acid) is a fluorescent organic compound with the formula CH(SOH). It is one of several isomers of naphthalenedisulfonic acid. It a colorless solid, typically obtained as the tetrahydrate. Like other sulfonic acids, it is a strong acid. It is named for British chemist Henry Edward Armstrong. | 0 | Organic Chemistry |
René Roy uses carbohydrate chemistry to develop neoglycoconjugates and polymers to treat disease related to glycoproteins such as bacterial infections and cancers. His synthesis of new glycan structures, among which glycopolymers, glycodendrimers, and glycodendrimersomes (terms that he first developed) enabled progress in the area of multivalent molecular recognition mechanisms.
He is known for his work on semi-synthetic glycoconjugate vaccines. He has designed a breast cancer vaccine prototype.
René Roy has authored more than 370 scientific articles and 2 books on vaccines and glycomimetics. He has 5 patents to his credit, of which two ended in commercial products | 0 | Organic Chemistry |
Eukaryotic translation is the biological process by which messenger RNA is translated into proteins in eukaryotes. It consists of four phases: initiation, elongation, termination, and recapping. | 1 | Biochemistry |
There are four main types of making to localize the artificial metal cofactor to make an ArM, including covalent, supramolecular, metal substitution and dative. | 0 | Organic Chemistry |
Amorphous carbonia, also called a-carbonia or a-CO, is an exotic amorphous solid form of carbon dioxide that is analogous to amorphous silica glass. It was first made in the laboratory in 2006 by subjecting dry ice to high pressures (40-48 gigapascal, or 400,000 to 480,000 atmospheres), in a diamond anvil cell. Amorphous carbonia is not stable at ordinary pressures—it quickly reverts to normal CO.
While normally carbon dioxide forms molecular crystals, where individual molecules are bound by Van der Waals forces, in amorphous carbonia a covalently bound three-dimensional network of atoms is formed, in a structure analogous to silicon dioxide or germanium dioxide glass.
Mixtures of a-carbonia and a-silica may be a prospective very hard and stiff glass material stable at room temperature. Such glass may serve as protective coatings, e.g. in microelectronics.
The discovery has implications for astrophysics, as interiors of massive planets may contain amorphous solid carbon dioxide. | 7 | Physical Chemistry |
Coacervates are a type of lyophilic colloid; that is, the dense phase retains some of the original solvent – generally water – and does not collapse into solid aggregates, rather keeping a liquid property. Coacervates can be characterized as complex or simple based on the driving force for the LLPS: associative or segregative. Associative LLPS is dominated by attractive interactions between macromolecules (such as electrostatic force between oppositely charged polymers), and segregative LLPS is driven by the minimization of repulsive interactions (such as hydrophobic effect on proteins containing a disordered region).
The thermodynamics of segregative LLPS can be described by a Flory-Huggins polymer mixing model (see equation). In ideal polymer solutions, the free-energy of mixing (ΔG) is negative because the mixing entropy (ΔS, combinatorial in the Flory-Huggins approach) is positive and the interaction enthalpies are all taken as equivalent (ΔH or χ = 0). In non-ideal solutions, ΔH can be different from zero, and the process endothermic enough to overcome the entropic term and favor the de-mixed state (the blue curve shifts up). Low molecular-weight solutes will hardly reach such non-ideality, whereas for polymeric solutes, with increasing interactions sites N and therefore decreasing entropic contribution, simple coacervation is much more likely.
The phase diagram of the mixture can be predicted by experimentally determining the two-phase boundary, or binodal curve. In a simplistic theoretical approach, the binodes are the compositions at which the free energy of de-mixing is minimal (
), across different temperatures (or other interaction parameter). Alternatively, by minimizing the change in free energy of de-mixing in regards to composition (), the spinodal curve is defined. The conditions of the mixture in comparison to the two curves defines the phase separation mechanism: nucleation-growth of coacervate droplets (when the binodal region is crossed slowly) and spinodal decomposition.
Associative LLPS is more complex to describe, as both solute polymers are present in the dilute and dense phase. Electrostatic-based complex coacervates are the most common, and in that case the solutes are two polyelectrolytes of opposite charge. The Voorn-Overbeek approach applies the Debye-Hückel approximation to the enthalpic term in the Flory-Huggins model, and considers two polyelectrolytes of the same length and at the same concentration. Complex coacervates are a subset of aqueous two-phase systems (ATPS), which also include segregatively separated systems in which both phases are enriched in one type of polymer. | 7 | Physical Chemistry |
Sulfides are important in biology, notably in the amino acid methionine and the cofactor biotin. Petroleum contains many organosulfur compounds, including sulfides. Polyphenylene sulfide is a useful high temperature plastic. Coenzyme M, , is the precursor to methane (i.e. natural gas) via the process of methanogenesis. | 0 | Organic Chemistry |
In oceanography, temperature-salinity diagrams, sometimes called T-S diagrams, are used to identify water masses. In a T-S diagram, rather than plotting each water property as a separate "profile," with pressure or depth as the vertical coordinate, potential temperature (on the vertical axis) is plotted versus salinity (on the horizontal axis). As long as it remains isolated from the surface, where heat or fresh water can be gained or lost, and in the absence of mixing with other water masses, a water parcel's potential temperature and salinity are conserved. Deep water masses thus retain their T-S characteristics for long periods of time, and can be identified readily on a T-S plot.
Temperature and salinity combine to determine the potential density of seawater; contours of constant potential density are often shown in T-S diagrams. | 9 | Geochemistry |
* Carotid bodies and aortic bodies detect changes primarily in pCO and H ion concentration. They also sense decrease in partial pressure of O, but to a lesser degree than for pCO and H ion concentration.
* The chemoreceptor trigger zone is an area of the medulla in the brain that receives inputs from blood-borne drugs or hormones, and communicates with the vomiting center (area postrema) to induce vomiting.
* Primary cilia play important roles in chemosensation. In adult tissues, these cilia regulate cell proliferation in response to external stimuli, such as tissue damage. In humans, improper functioning of primary cilia is associated with important diseases known as ciliopathies. | 3 | Analytical Chemistry |
Decantation can also separate solid and liquid mixtures by allowing gravity to pull the solid fragments to settle at the bottom of the container. In laboratory situations, decantation of mixtures containing solids and liquids occur in test tubes. To enhance productivity, test tubes should be placed at a 45° angle to allow sediments to settle at the bottom of the apparatus.
A centrifuge machine may also be used in decantation as the natural process of settling down is time-consuming and tedious. A centrifuge forces the precipitate to the bottom of the container; if the force is high enough, solids can aggregate to form pellets, making it easier to separate the mixtures. Then the liquid can be more easily poured away, as the precipitate will tend to remain in its compressed form.
A decanter centrifuge may be used for continuous solid-liquid separation. | 3 | Analytical Chemistry |
A method for detecting arsenious oxide, simple arsenic, in corpses was devised in 1773 by the Swedish chemist, Carl Wilhelm Scheele. His work was expanded upon, in 1806, by German chemist Valentin Ross, who learned to detect the poison in the walls of a victim's stomach.
James Marsh was the first to apply this new science to the art of forensics. He was called by the prosecution in a murder trial to give evidence as a chemist in 1832. The defendant, John Bodle, was accused of poisoning his grandfather with arsenic-laced coffee. Marsh performed the standard test by mixing a suspected sample with hydrogen sulfide and hydrochloric acid. While he was able to detect arsenic as yellow arsenic trisulfide, when it was shown to the jury it had deteriorated, allowing the suspect to be acquitted due to reasonable doubt.
Annoyed by that, Marsh developed a much better test. He combined a sample containing arsenic with sulfuric acid and arsenic-free zinc, resulting in arsine gas. The gas was ignited, and it decomposed to pure metallic arsenic, which, when passed to a cold surface, would appear as a silvery-black deposit. So sensitive was the test, known formally as the Marsh test, that it could detect as little as one-fiftieth of a milligram of arsenic. He first described this test in The Edinburgh Philosophical Journal in 1836. | 3 | Analytical Chemistry |
The woodsprite (Atokirina in Navi) is an animal, also called seed, of the "holy tree", appearing similar to airborne jellyfish. Neytiri describes them as very pure spirits, and slaps Jake for shooing two of them away. The Omaticaya Clan plants one of these seeds on the body of a deceased Navi, so the Navis consciousness will become part of Eywa. | 1 | Biochemistry |
An electrocyclic reaction can either be classified as conrotatory or disrotatory based on the rotation at each end of the molecule. In conrotatory mode, both atomic orbitals of the end groups turn in the same direction (such as both atomic orbitals rotating clockwise or counter-clockwise). In disrotatory mode, the atomic orbitals of the end groups turn in opposite directions (one atomic orbital turns clockwise and the other counter-clockwise). The cis/trans geometry of the final product is directly decided by the difference between conrotation and disrotation.
Determining whether a particular reaction is conrotatory or disrotatory can be accomplished by examining the molecular orbitals of each molecule and through a set of rules. Only two pieces of information are required to determine conrotation or disrotation using the set of rules: how many electrons are in the pi-system and whether the reaction is induced by heat or by light. This set of rules can also be derived from an analysis of the molecular orbitals for predicting the stereochemistry of electrocyclic reactions. | 7 | Physical Chemistry |
Jones was born in New London, Maryland in a farming family and went to study chemistry at Johns Hopkins University, receiving a PhD in 1892 with studies under Harmon N. Morse. He then travelled to Europe where he worked for two years at the laboratories of Wilhelm Ostwald in Leipzig, Svante Arrhenius in Stockholm and Jacobus vant Hoff in Amsterdam. He then joined Johns Hopkins as a fellow and from 1895 as n instructor. He became a full professor in 1903. He published several books and many papers and was a popular teacher who would recount anecdotes from the lives of chemists he had worked with in Europe. At the time of his death, he was writing a book on the Nature of Solution'. This was published posthumously with a biographical note by his colleague E. Emmet Reid. Jones was depressed and committed suicide by consuming a cyanide pill.
Jones married Harriet Brooks in 1902. | 7 | Physical Chemistry |
Astrocytes express several sAC splice variants, which are involved in metabolic coupling between neurons and astrocytes. Increase of potassium [K] in the extracellular space caused by neuronal activity depolarizes the cell membrane of nearby astrocytes and facilitates the entry of hydrogencarbonate through Na/HCO- cotransporters. The increase in cytosolic hydrogencarbonate activates sAC; the result of this activation is the release of lactate for use as energy source by the neurons. | 1 | Biochemistry |
Due to low titre and to difficulties in isolating and purifying thienamycin produced by fermentation, total synthesis is the preferred method for commercial production. Numerous methods are available in the literature for the total synthesis of thienamycin. One synthetic route is given in Figure 3.
The starting β-lactam for the pathway given above can be synthesized using the following method (Figure 4): | 0 | Organic Chemistry |
In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium. It is that temperature and pressure at which the sublimation, fusion, and vaporisation curves meet. For example, the triple point of mercury occurs at a temperature of and a pressure of 0.165 mPa.
In addition to the triple point for solid, liquid, and gas phases, a triple point may involve more than one solid phase, for substances with multiple polymorphs. Helium-4 is unusual in that it has no sublimation/deposition curve and therefore no triple points where its solid phase meets its gas phase. Instead, it has a vapor-liquid-superfluid point, a solid-liquid-superfluid point, a solid-solid-liquid point, and a solid-solid-superfluid point. None of these should be confused with the Lambda Point, which is not any kind of triple point.
The triple point of water was used to define the kelvin, the base unit of thermodynamic temperature in the International System of Units (SI). The value of the triple point of water was fixed by definition, rather than by measurement, but that changed with the 2019 redefinition of SI base units. The triple points of several substances are used to define points in the ITS-90 international temperature scale, ranging from the triple point of hydrogen (13.8033 K) to the triple point of water (273.16 K, 0.01 °C, or 32.018 °F).
The term "triple point" was coined in 1873 by James Thomson, brother of Lord Kelvin. | 7 | Physical Chemistry |
The average adult human body contains approximately atoms and contains at least detectable traces of 60 chemical elements. About 29 of these elements are thought to play an active positive role in life and health in humans.
The relative amounts of each element vary by individual, mainly due to differences in the proportion of fat, muscle and bone in their body. Persons with more fat will have a higher proportion of carbon and a lower proportion of most other elements (the proportion of hydrogen will be about the same).
The numbers in the table are averages of different numbers reported by different references.
The adult human body averages ~53% water. This varies substantially by age, sex, and adiposity. In a large sample of adults of all ages and both sexes, the figure for water fraction by weight was found to be 48 ±6% for females and 58 ±8% water for males. Water is ~11% hydrogen by mass but ~67% hydrogen by atomic percent, and these numbers along with the complementary % numbers for oxygen in water, are the largest contributors to overall mass and atomic composition figures. Because of water content, the human body contains more oxygen by mass than any other element, but more hydrogen by atom-fraction than any element.
The elements listed below as "Essential in humans" are those listed by the US Food and Drug Administration as essential nutrients, as well as six additional elements: oxygen, carbon, hydrogen, and nitrogen (the fundamental building blocks of life on Earth), sulfur (essential to all cells) and cobalt (a necessary component of vitamin B). Elements listed as "Possibly" or "Probably" essential are those cited by the US National Research Council as beneficial to human health and possibly or probably essential.
Iron = ~3 g in males, ~2.3 g in females
Of the 94 naturally occurring chemical elements, 61 are listed in the table above. Of the remaining 33, it is not known how many occur in the human body.
Most of the elements needed for life are relatively common in the Earths crust. Aluminium, the third most common element in the Earths crust (after oxygen and silicon), serves no function in living cells, but is toxic in large amounts, depending on its physical and chemical forms and magnitude, duration, frequency of exposure, and how it was absorbed by the human body. Transferrins can bind aluminium. | 1 | Biochemistry |
Subsequent research on DNA computing has produced [https://ieeexplore.ieee.org/document/8642913 reversible DNA computing], bringing the technology one step closer to the silicon-based computing used in (for example) PCs. In particular, [https://web.archive.org/web/20190201104419/https://users.cs.duke.edu/~reif/index.htm John Reif] and his group at Duke University have proposed two different techniques to reuse the computing DNA complexes. The first design uses dsDNA gates, while the second design uses DNA hairpin complexes.
While both the designs face some issues (such as reaction leaks), this appears to represent a significant breakthrough in the field of DNA computing. Some other groups have also attempted to address the gate reusability problem.
Using strand displacement reactions (SRDs), reversible proposals are presented in the [https://www.mdpi.com/2073-8994/13/7/1242 "Synthesis Strategy of Reversible Circuits on DNA Computers" paper] for implementing reversible gates and circuits on DNA computers by combining DNA computing and reversible computing techniques. This paper also proposes a universal reversible gate library (URGL) for synthesizing n-bit reversible circuits on DNA computers with an average length and cost of the constructed circuits better than the previous methods. | 1 | Biochemistry |
Stomatal crypts are sunken areas of the leaf epidermis which form a chamber-like structure that contains one or more stomata and sometimes trichomes or accumulations of wax. Stomatal crypts can be an adaption to drought and dry climate conditions when the stomatal crypts are very pronounced. However, dry climates are not the only places where they can be found. The following plants are examples of species with stomatal crypts or antechambers: Nerium oleander, conifers, Hakea and Drimys winteri which is a species of plant found in the cloud forest. | 5 | Photochemistry |
A healthy American male soldier was given EA-3148, 1.15 µg/kg i.v.. Erythrocyte AChE values dropped precipitously to 22% of normal within 15 min of dosing and to 0% at 48 h; the value recovered to 88% of normal at 72 days post-exposure. Signs of toxicity were evident within 5-8 min of treatment in two comparably dosed subjects who felt dizzy, weak, tired, sweaty, and had hands and feet that were moist. Within 2 h post-exposure, these subjects reportedly were resting, eating, and feeling fine.
A U.S. Army report summarizing experience with EA-3148 noted anorexia, fatigue, poor sleep, unusual dreams, dizziness, euphoria, blurred vision, increased salivation, restlessness; decrements in a test of numerical facility in four individuals and exaggeration of a schizoid personality in one male soldier. | 1 | Biochemistry |
Because in non-ideal solutions volumes are no longer strictly additive it is often preferable to work with molality b (mol/kg of HO) rather than molarity c (mol/L). In that case, molal ionic strength is defined as:
in which
:i = ion identification number
:z = charge of ion
:b = molality (mol solute per Kg solvent) | 7 | Physical Chemistry |
All FSL Kode constructs disperse in water and are therefore compatible with inkjet printers. FSL constructs can be printed with a standard desktop inkjet printer directly onto paper to create immunoassays. An empty ink cartridge is filled with an FSL construct and words, barcodes, or graphics are printed. A Perspex template is adhered to the surface to create reaction wells. The method is then a standard EIA procedure, but blocking of serum is not required and undiluted serum can be used. A typical procedure is as follows: add serum, incubate, wash by immersion, add secondary EIA conjugate, incubate, wash, add NBT/BCIP precipitating substrate and stop the reaction when developed by washing (Fig. 9). The end result is stable for years. | 1 | Biochemistry |
To lower the concentration of airborne dust concentrations during woodworking, dust extraction systems are used. These can be divided into two types. The first are local exhaust ventilation systems, the second are room ventilation systems. Use of personal respirators, a form of personal protective equipment, can also isolate workers from dust. | 2 | Environmental Chemistry |
The mining and mineral processing industry uses screening for a variety of processing applications. For example, after mining the minerals, the material is transported to a primary crusher. Before crushing large boulder are scalped on a shaker with thick shielding screening. Further down stream after crushing the material can pass through screens with openings or slots that continue to become smaller. Finally, screening is used to make a final separation to produce saleable products based on a grade or a size range. | 8 | Metallurgy |
Side effects may include liver damage and nerve problems. Hyperthermia may also occur. Deaths have also resulted. | 1 | Biochemistry |
Another application of biogenic substances is in the synthesis of metallic nanoparticles. The current chemical and physical production methods for nanoparticles used are costly and produce toxic waste and pollutants in the environment. Additionally, the nanoparticles that are produced can be unstable and unfit for use in the body. Using plant-derived biogenic substances aims to create an environmentally-friendly and cost-effective production method. The biogenic phytochemicals used for these reduction reactions can be derived from plants in numerous ways, including a boiled leaf broth, biomass powder, whole plant immersion in solution, or fruit and vegetable juice extracts. C. annuum juices have been shown to produce Ag nanoparticles at room temperature when treated with silver ions and additionally deliver essential vitamins and amino acids when consumed, making them a potential nanomaterials agent. Another procedure is through the use of a different biogenic substance: the exudate of germinating seeds. When seeds are soaked, they passively release phytochemicals into the surrounding water, which after reaching equilibrium can be mixed with metal ions to synthesise metallic nanoparticles. M. sativa exudate in particular has had success in effectively producing Ag metallic particles, while L. culinaris is an effective reactant for manufacturing Au nanoparticles. This process can also be further adjusted by manipulating factors such as pH, temperature, exudate dilution and plant origin to produce different shapes of nanoparticles, including triangles, spheres, rods, and spirals. These biogenic metallic nanoparticles then have applications as catalysts, glass window coatings to insulate heat, in biomedicine, and in biosensor devices. | 0 | Organic Chemistry |
Temperature has an effect on both, the equilibrium state and kinetics of protein adsorption. The amount of protein adsorbed at high temperature is usually higher than that at room temperature. Temperature variation causes conformational changes in protein influencing adsorption. These conformational rearrangements in proteins results in an entropy gain which acts as a major driving force for protein adsorption. The temperature effect on protein adsorption can be seen in food manufacturing processes, especially liquid foods such as, milk which causes severe fouling on the wall surfaces of equipment where thermal treatment is carried out. | 1 | Biochemistry |
Any signal that can be represented as a variable that varies in time has a corresponding frequency spectrum. This includes familiar entities such as visible light (perceived as color), musical notes (perceived as pitch), radio/TV (specified by their frequency, or sometimes wavelength) and even the regular rotation of the earth. When these signals are viewed in the form of a frequency spectrum, certain aspects of the received signals or the underlying processes producing them are revealed. In some cases the frequency spectrum may include a distinct peak corresponding to a sine wave component. And additionally there may be peaks corresponding to harmonics of a fundamental peak, indicating a periodic signal which is not simply sinusoidal. Or a continuous spectrum may show narrow frequency intervals which are strongly enhanced corresponding to resonances, or frequency intervals containing almost zero power as would be produced by a notch filter. | 7 | Physical Chemistry |
Hydroxyl ion absorption is the absorption in optical fibers of electromagnetic radiation, including the near-infrared, due to the presence of trapped hydroxyl ions remaining from water as a contaminant.
The hydroxyl (OH) ion, can penetrate glass during or after product fabrication, resulting in significant attenuation of discrete optical wavelengths, e.g., centred at 1.383 μm, used for communications via optical fibres. | 3 | Analytical Chemistry |
As described in the applications section, spectrophotometry can be used in both qualitative and quantitative analysis of DNA, RNA, and proteins. Qualitative analysis can be used and spectrophotometers are used to record spectra of compounds by scanning broad wavelength regions to determine the absorbance properties (the intensity of the color) of the compound at each wavelength. One experiment that can demonstrate the various uses that visible spectrophotometry can have is the separation of β-galactosidase from a mixture of various proteins. Largely, spectrophotometry is best used to help quantify the amount of purification your sample has undergone relative to total protein concentration. By running an affinity chromatography, B-Galactosidase can be isolated and tested by reacting collected samples with Ortho-Nitrophenyl-β-galactoside (ONPG) and determining if the sample turns yellow. Following this testing the sample at 420 nm for specific interaction with ONPG and at 595 for a Bradford Assay the amount of purification can be assessed quantitatively. In addition to this spectrophotometry can be used in tandem with other techniques such as SDS-Page electrophoresis in order to purify and isolate various protein samples. | 7 | Physical Chemistry |
The use of H—P HSQC is relatively uncommon in lipidomics, however use of P in lipidomics dates back to the 1990s. The use of this technique is limited with respect to mass spectrometry due to its requirement for much bigger sample size, however the combination of H—P HSQC with mass spectrometry is regarded as a thorough approach to lipidomics and techniques for dual spectroscopy are becoming available. | 7 | Physical Chemistry |
1,1-Difluoroethane, or DFE, is an organofluorine compound with the chemical formula CHF. This colorless gas is used as a refrigerant, where it is often listed as R-152a (refrigerant-152a) or HFC-152a (hydrofluorocarbon-152a). It is also used as a propellant for aerosol sprays and in gas duster products. As an alternative to chlorofluorocarbons, it has an ozone depletion potential of zero, a lower global warming potential (124) and a shorter atmospheric lifetime (1.4 years). | 2 | Environmental Chemistry |
In the human genome, STAT6 protein is encoded by the STAT6 gene, located on the chromosome 12q13.3-q14.1. The gene encompasses over 19 kb and consists of 23 exons. STAT6 shares structural similarity with the other STAT proteins and is composed of the N-terminal domain, DNA binding domain, SH3- like domain, SH2 domain and transactivation domain (TAD).
STAT proteins are activated by the Janus family (JAKs) tyrosine kinases in response to cytokine exposure. STAT6 is activated by cytokines interleukin-4 (IL-4), and interleukin-13 (IL-13) with their receptors that both contain the α subunit of the IL-4 receptor (IL-4Rα). Tyrosine phosporylation of STAT6 after stimulation by IL-4 results in the formation of STAT6 homodimers that bind specific DNA elements via a DNA-binding domain. | 1 | Biochemistry |
To aid in the digestion of their food, animals evolved organs such as beaks, tongues, radulae, teeth, crops, gizzards, and others. | 1 | Biochemistry |
Superhydrophilicity allows for surfaces to clean away a wide variety of dirt or debris. This mechanism is very different than the aforementioned superhydrophobic surfaces. For superhydrophilic self-cleaning surfaces, cleaning occurs because water on the surface is able to spread out to a great degree (extremely low water contact angle) to get between any fouling debris and the surface to wash away the debris. | 7 | Physical Chemistry |
Hybridization is one way to determine the sequence of a DNA strand from detecting the changes in the length of a hairpin. When a probe hybridizes to an open hairpin, complete refolding of the hairpin is stalled, and the position of the hybridized probe can be inferred. Thus the sequence of a DNA fragment of interest can be inferred from overlapping the positions of probes sets, which are allowed to hybridize one by one. | 1 | Biochemistry |
Through the voluntary work of its members, CSMBLM is dedicated to improve the profession and scientific field of medical biochemistry and laboratory medicine, raise the level of public awareness at national level, encourage and provide assistance to its members in achieving professional and scientific excellence especially in performance quality of every segment of work in medical biochemistry laboratories. | 1 | Biochemistry |
The phosphaethynolate anion is the heavier isoelectronic congener of the cyanate anion. It has been shown that it behaves in a similar way to its lighter analogue, as an ambidentate nucleophile. This ambidentate character of the anion means that it is able to bind via both the phosphorus and oxygen atoms depending on the nature of the centre being coordinated.
Computational studies carried out on the anion such as Natural Bond Orbital (NBO) and Natural Resonance Theory (NRT) analyses can go part way to explain why PCO can react in such a manner . The two dominant resonance forms of the phosphaethynolate anion localise negative charge on either the phosphorus or oxygen atoms meaning both are sites of nucleophilicity. The same applies for the cyanate anion hence why PCO is observed to have similar pseudo-halogenic behaviour. | 7 | Physical Chemistry |
Heating of the surfaces via passing current through a conductive transparent film has been shown to repel and remove contamination. It has been used in inkjet printers to reduced ink contamination on sensor windows. | 7 | Physical Chemistry |
Since corepressors participate and regulate a vast range of gene expression, it is not surprising that aberrant corepressor activities can cause diseases.
Acute myeloid leukemia (AML) is a highly lethal blood cancer characterized by uncontrolled myeloid cell growth. Two homologous corepressor genes, BCOR (BCL6 corepressor) and BCORL1, are recurrently mutated in AML patients. BCOR works with multiple transcription factors and is known to play vital regulatory roles in embryonic development. Clinical results detected BCOR somatic mutations in ~4% of an unselected group of AML patients, and ~17% in a subset of patients who lack known AML-causing mutations. Similarly, BCORL1 is a corepressor that regulates cellular processes, and was found to be mutated in ~6% of tested AML patients. These studies point out a strong association between corepressor mutations and AML. Further corepressor research may reveal potential therapeutic targets for AML and other diseases. | 1 | Biochemistry |
Tetrafluoroethane is typically made by reacting trichloroethylene with hydrogen fluoride:
:CHCl=CCl + 4 HF → CFCHF + 3 HCl
It reacts with butyllithium to give trifluorovinyl lithium:
:CFCHF + 2 BuLi → CF=CFLi + LiF + 2 BuH | 2 | Environmental Chemistry |
Increased carbon dioxide levels, mostly from burning fossil fuels, are changing ocean chemistry. Global warming and changes in salinity have significant implications for the ecology of marine environments. | 9 | Geochemistry |
Chemicals and their metabolites can be detected in a variety of biological substances such as blood, urine, exhaled air, hair, nails, feces, semen, breast milk, or saliva. Blood and urine are the most commonly used in occupational safety and health.
Breast milk is a favored matrix (substance) to measure lipophilic (fat-loving) persistent, bioaccumulative, and toxic (PBT) compounds during lactation; this exposure route is dominant for breastfeeding children. A lipophilic compound might also be detected in blood, while a hydrophilic (water-loving) compound might be detected in urine.
Analytical methods used by the CDC include isotope dilution mass spectrometry, inductively coupled plasma mass spectrometry, or graphite furnace atomic absorption spectrometry. Others include gas chromatography or high-performance liquid chromatography coupled with various detectors such as ultraviolet, electron capture, flame ionization, atomic emission, or mass spectrometric detectors. Ligand-binding assays and immunoassays are also used.
As biomonitoring necessarily involves working with human subjects and specimens, biosafety procedures are necessary to prevent the transmission of pathogens. | 2 | Environmental Chemistry |
Different form of the stationary principle for T-matrix reads
The wave functions and must satisfy the same Lippmann-Schwinger equations to get the stationary value. | 7 | Physical Chemistry |
Hand-counting is a cheap and easy to conduct method to estimate the liberation characteristics of a bulk sample wither originating from run-of-mine material, a waste dump or for example exploration trenching. Analysis of particles in the size range 10-100mm has been conducted on a total sample mass of 10 tonnes. By visual inspection of trained personnel, a classification of each particle into different bins (e.g. lithology, grade) is possible and the distribution is determined by weighing each bin. A trained professional can quickly estimate the efficiency of a specific detection and process efficiency of sensor-based ore sorting knowing the sensor response of the mineralogy of ore in question and other process efficiency parameters. | 3 | Analytical Chemistry |
Typical adsorbents proposed for carbon capture and storage are zeolites and MOFs. The customization of adsorbents makes them a potentially attractive alternative to absorption. Because adsorbents can be regenerated by temperature or pressure swing, this step can be less energy intensive than absorption regeneration methods. Major problems that are present with adsorption cost in carbon capture are: regenerating the adsorbent, mass ratio, solvent/MOF, cost of adsorbent, production of the adsorbent, lifetime of adsorbent.
In sorption enhanced water gas shift (SEWGS) technology a pre-combustion carbon capture process, based on solid adsorption, is combined with the water gas shift reaction (WGS) in order to produce a high pressure hydrogen stream. The CO stream produced can be stored or used for other industrial processes. | 7 | Physical Chemistry |
Lymphocytes can enter mitosis when they are activated by mitogens or antigens. B cells specifically can divide when they encounter an antigen matching their immunoglobulin. T cells undergo mitosis when stimulated by mitogens to produce small lymphocytes that are then responsible for the production of lymphokines, which are substances that modify the host organism to improve its immunity. B cells, on the other hand, divide to produce plasma cells when stimulated by mitogens, which then produce immunoglobulins, or antibodies. Mitogens are often used to stimulate lymphocytes and thereby assess immune function. The most commonly used mitogens in clinical laboratory medicine are:
Lipopolysaccharide toxin from gram-negative bacteria is thymus-independent. They may directly activate B cells, regardless of their antigenic specificity. Plasma cells are terminally differentiated and, therefore, cannot undergo mitosis. Memory B cells can proliferate to produce more memory cells or plasma B cells. This is how the mitogen works, that is, by inducing mitosis in memory B cells to cause them to divide, with some becoming plasma cells. | 1 | Biochemistry |
Antarafacial (Woodward-Hoffmann symbol a) and suprafacial (s) are two topological concepts in organic chemistry describing the relationship between two simultaneous chemical bond making and/or bond breaking processes in or around a reaction center. The reaction center can be a p- or sp-orbital (Woodward-Hoffmann symbol ω), a conjugated system (π) or even a sigma bond (σ).
* The relationship is antarafacial when opposite faces of the π system or isolated orbital are involved in the process (think anti). For a σ bond, it corresponds to involvement of one "interior" lobe and one "exterior" lobe of the bond.
* The relationship is suprafacial when the same face of the π system or isolated orbital are involved in the process (think syn). For a σ bond, it corresponds to involvement of two "interior" lobes or two "exterior" lobes of the bond.
The components of all pericyclic reactions, including sigmatropic reactions and cycloadditions, and electrocyclizations, can be classified as either suprafacial or antarafacial, and this determines the stereochemistry. In particular, antarafacial topology corresponds to inversion of configuration for the carbon atom of a [1, n]-sigmatropic rearrangement, and conrotation for electrocyclic ring closure, while suprafacial corresponds to retention and disrotation.
An example is the [1,3]-hydride shift, in which the interacting frontier orbitals are the allyl free radical and the hydrogen 1s orbitals. The suprafacial shift is symmetry-forbidden because orbitals with opposite algebraic signs overlap. The symmetry allowed antarafacial shift would require a strained transition state and is also unlikely. In contrast a symmetry allowed and suprafacial [1,5]-hydride shift is a common event. | 4 | Stereochemistry |
Weak affinity chromatography (WAC) is an affinity chromatography technique for affinity screening in drug development. WAC is an affinity-based liquid chromatographic technique that separates chemical compounds based on their different weak affinities to an immobilized target. The higher affinity a compound has towards the target, the longer it remains in the separation unit, and this will be expressed as a longer retention time. The affinity measure and ranking of affinity can be achieved by processing the obtained retention times of analyzed compounds. Affinity chromatography is part of a larger suite of techniques used in chemoproteomics based drug target identification.
The WAC technology is demonstrated against a number of different protein targets – proteases, kinases, chaperones and protein–protein interaction (PPI) targets. WAC has been shown to be more effective than established methods for fragment based screening. | 3 | Analytical Chemistry |
In World War II Eshelby began working for the Admiralty on the degaussing of ships, but on 4 May 1940 he joined the Technical Branch of the Royal Air Force. His work from February 1941 to June 1942 was for the Coastal Command Development Unit conducting performance trials of Air-to-Surface Vessel radar and other operational devices in all types of aircraft. He was then involved in radar work, from August 1942 to February 1943 with 76 signals wing and from February 1943 to September 1944 at the radar establishment at Malvern. He was then transferred to disarmament work and then to the Air Historical branch in September 1945. He left the RAF as a squadron leader on 4 October 1946.
After the war Eshelby returned to Bristol University to study for a PhD and taught himself the theory of elasticity for his thesis on "Stationary and moving dislocations". He obtained his PhD in 1950 under Nevill Mott. In 1951 he moved to the University of Illinois Urbana-Champaign as a Research Associate, where he stayed until 1953 when he was appointed a lecturer at the University of Birmingham, where he taught from 1953 to 1964 at the Department of Metallurgy. During this time, he worked on point defects and dislocations, developing the method of transformation strains and studying the Eshelby inclusion problems for the first time, as well as the study of forces on elastic singularities.
In 1964 he moved to the Cavendish Laboratory at Cambridge University at the behest of Neville Mott, and was a Fellow of Churchill College from 1965 to 1966. He was then appointed Reader in the Faculty of Materials (Theory of Materials) at the University of Sheffield, where he became Professor in 1971. | 8 | Metallurgy |
In 1972, Corbett was elected a Fellow of the Royal Society of New Zealand. He was also a Fellow of the New Zealand Institute of Chemistry. | 0 | Organic Chemistry |
Alkanediazonium salts are synthetically unimportant due to their extreme and uncontrolled reactivity toward S2/S1/E1 substitution. These cations are however of theoretical interest. Furthermore, methyldiazonium carboxylate is believed to be an intermediate in the methylation of carboxylic acids by diazomethane, a common transformation.
Loss of is both enthalpically and entropically favorable:
:, ΔH = −43 kcal/mol
:, ΔH = −11 kcal/mol
For secondary and tertiary alkanediazonium species, the enthalpic change is calculated to be close to zero or negative, with minimal activation barrier. Hence, secondary and (especially) tertiary alkanediazonium species are either unbound, nonexistent species or, at best, extremely fleeting intermediates.
The aqueous pK of methanediazonium () is estimated to be <10. | 0 | Organic Chemistry |
In nuclear magnetic resonance spectroscopy, the highly abundant C isotope does not produce any signal whereas the comparably rare C isotope is easily detected. As a result, carbon isotopomers of a compound can be studied by carbon-13 NMR to learn about the different carbon atoms in the structure. Each individual structure that contains a single C isotope provides data about the structure in its immediate vicinity. A large sample of a chemical contains a mixture of all such isotopomers, so a single spectrum of the sample contains data about all carbons in it. Nearly all of the carbon in normal samples of carbon-based chemicals is C, with only about 1% abundance of C, so there is only about a 1% abundance of the total of the singly-substituted isotopologues, and exponentially smaller amounts of structures having two or more C in them. The rare case where two adjacent carbon atoms in a single structure are both C causes a detectable coupling effect between them as well as signals for each one itself. The INADEQUATE correlation experiment uses this effect to provide evidence for which carbon atoms in a structure are attached to each other, which can be useful for determining the actual structure of an unknown chemical. | 4 | Stereochemistry |
The G-less cassette is a reporter gene that encodes a transcript lacking guanine nucleotides in the sense strand of the DNA (hence "G-less"). A plasmid containing such a gene is located downstream of a MCS. After the promoter is inserted into the MCS, transcription proceeds with the addition of radiolabeled UTP, CTP, and ATP (as well as non-radiolabeled/cold nucleotides) and continues until the end of the G-less cassette is reached and guanine residues are once again apparent in the sense strand of the DNA. The absence of GTP in vitro results in transcription being prematurely terminated at the first guanine residue in the sense strand following the cassette. Gel electrophoresis is performed on the transcription products and the amount of radioactivity is quantified by autoradiography or phosphorimaging to determine the strength of the promoter of interest. | 1 | Biochemistry |
Leached pulp and carbon are transferred in a countercurrent flow arrangement involving a series of tanks, usually numbering 4 to 6. In the final tank, fresh or barren carbon is put in contact with low grade or tailings solution. At this tank the fresh carbon has a high affinity for gold and can remove trace amounts of gold (to levels below 0.01 mg/L Au in solution).
As it moves up the train, the carbon loads to higher and higher concentrations of gold, as it comes in contact with higher grade solutions. Typically concentrations as high as 4000 to 8000 grams of gold per tonne of carbon (g/t Au) can be achieved on the final loaded carbon, as it comes in contact with freshly leached ore and pregnant leach solution (PLS). | 8 | Metallurgy |
There are a variety of challenges associated with the flow of liquids through carbon nanotubes and nanopipes. A common occurrence is channel blocking due to large macromolecules in the liquid. Also, any insoluble debris in the liquid can easily clog the tube. A solution for this researchers are hoping to find is a low friction coating or channel materials that help reduce the blocking of the tubes. Also, large polymers, including biologically relevant molecules such as DNA, often fold in vivo, causing blockages. Typical DNA molecules from a virus have lengths of approx. 100–200 kilobases and will form a random coil of the radius some 700 nm in aqueous solution at 20%. This is also several times greater than the pore diameter of even large carbon pipes and two orders of magnitude the diameter of a single walled carbon nanotube. | 7 | Physical Chemistry |
Enamines can be efficiently cross-coupled with enol silanes through treatment with ceric ammonium nitrate. These reactions were reported by the Narasaka group in 1975, providing a route to stable enamines as well as one instance of a 1,4-diketone (derived from a morpholine amine reagent). Later, these results were exploited by the MacMillan group with the development of an organocatalyst which used the Narasaka substrates to produce 1,4 dicarbonyls enantioselectively, with good yields. Oxidative dimerization of aldehydes in the presence of amines proceeds through the formation of an enamine followed by a final pyrrole formation. This method for symmetric pyrrole synthesis was developed in 2010 by the Jia group, as a valuable new pathway for the synthesis of pyrrole-containing natural products. | 0 | Organic Chemistry |
Different gases will have different mean free paths for molecules and electrons. This is because different molecules have ionization cross sections, that is, different effective diameters. Noble gases like helium and argon are monatomic harder to ionize and tend to have smaller effective diameters. This gives them greater mean free paths.
Ionization potentials differ between molecules, as well as the speed that they recapture electrons after they have been knocked out of orbit. All three effects change the number of collisions needed to cause an exponential growth in free electrons. These free electrons are necessary to cause an arc. | 7 | Physical Chemistry |
Mikael Bols was born and grew up in Copenhagen, Denmark. He attended high school (Gentofte Statskole) from 1977 to 1980, and took a degree as chemical engineer at the Technical University of Denmark from 1980 to 1985. | 0 | Organic Chemistry |
T-1123 is a carbamate-based acetylcholinesterase inhibitor. It was investigated as a chemical warfare agent starting in 1940. It does not go through the blood-brain barrier due to the charge on quaternary nitrogen. The antidote is atropine. T-1123 is a quaternary ammonium ion. A phenyl carbamate ester is bonded in the meta position to the nitrogen on a diethylmethyl amine. The chloride and methylsulfate salt of T-1123 is TL-1299 and TL-1317, respectively. | 1 | Biochemistry |
Basic oxygen steelmaking is a primary steelmaking process for converting molten pig iron into steel by blowing oxygen through a lance over the molten pig iron inside the converter. Exothermic heat is generated by the oxidation reactions during blowing.
The basic oxygen steel-making process is as follows:
# Molten pig iron (sometimes referred to as "hot metal") from a blast furnace is poured into a large refractory-lined container called a ladle.
# The metal in the ladle is sent directly for basic oxygen steelmaking or to a pretreatment stage where sulfur, silicon, and phosphorus are removed before charging the hot metal into the converter. In external desulfurizing pretreatment, a lance is lowered into the molten iron in the ladle and several hundred kilograms of powdered magnesium are added and the sulfur impurities are reduced to magnesium sulfide in a violent exothermic reaction. The sulfide is then raked off. Similar pretreatments are possible for external desiliconisation and external dephosphorisation using mill scale (iron oxide) and lime as fluxes. The decision to pretreat depends on the quality of the hot metal and the required final quality of the steel.
# Filling the furnace with the ingredients is called charging. The BOS process is autogenous, i.e. the required thermal energy is produced during the oxidation process. Maintaining the proper charge balance, the ratio of hot metal from melt to cold scrap is important. The BOS vessel can be tilted up to 360° and is tilted towards the deslagging side for charging scrap and hot metal. The BOS vessel is charged with steel or iron scrap (25–30%), if required. Molten iron from the ladle is added as required for the charge balance. A typical chemistry of hotmetal charged into the BOS vessel is: 4% C, 0.2–0.8% Si, 0.08%–0.18% P, and 0.01–0.04% S, all of which can be oxidised by the supplied oxygen except sulfur (which requires reducing conditions).
# The vessel is then set upright and a water-cooled, copper tipped lance with 3–7 nozzles is lowered into it to within a few feet of the surface of the bath and high-purity oxygen at a pressure of is introduced at supersonic speed. The lance "blows" 99% pure oxygen over the hot metal, igniting the carbon dissolved in the steel, to form carbon monoxide and carbon dioxide, causing the temperature to rise to about 1700 °C. This melts the scrap, lowers the carbon content of the molten iron and helps remove unwanted chemical elements. It is this use of pure oxygen (instead of air) that improves upon the Bessemer process, as the nitrogen (an undesirable element) and other gases in air do not react with the charge, and decrease the efficiency of the furnace.
# Fluxes (burnt lime or dolomite) are fed into the vessel to form slag, to maintain basicity of the slag – the ratio of calcium oxide to silicon oxide – at a level to minimise refractory wear and absorb impurities during the steelmaking process. During "blowing", churning of metal and fluxes in the vessel forms an emulsion that facilitates the refining process. Near the end of the blowing cycle, which takes about 20 minutes, the temperature is measured and samples are taken. A typical chemistry of the blown metal is 0.3–0.9% C, 0.05–0.1% Mn, 0.001–0.003% Si, 0.01–0.03% S and 0.005–0.03% P.
# The BOS vessel is tilted towards the slagging side and the steel is poured through a tap hole into a steel ladle with basic refractory lining. This process is called tapping the steel. The steel is further refined in the ladle furnace, by adding alloying materials to impart special properties required by the customer. Sometimes argon or nitrogen is bubbled into the ladle to make the alloys mix correctly.
# After the steel is poured off from the BOS vessel, the slag is poured into the slag pots through the BOS vessel mouth and dumped. | 8 | Metallurgy |
Some fjords develop euxinia if the connection to the open ocean is constricted, similar to the case of the Black Sea. This constriction prohibits relatively dense, oxygen-rich oceanic water from mixing with the bottom water of the fjord, which leads to stable stratified layers in the fjord. Low salinity melt water forms a lens of fresh, low density water on top of a more dense mass of bottom water. Ground sources of sulfur are also an important cause for euxinia in fjords. | 9 | Geochemistry |
Constrained geometry complexes are related to ansa-metallocenes except that one ligand is not Cp-related. | 0 | Organic Chemistry |
Water chemistry analyses are carried out to identify and quantify the chemical components and properties of water samples. The type and sensitivity of the analysis depends on the purpose of the analysis and the anticipated use of the water.
Chemical water analysis is carried out on water used in industrial processes, on waste-water stream, on rivers and stream, on rainfall and on the sea. In all cases the results of the analysis provides information that can be used to make decisions or to provide re-assurance that conditions are as expected.
The analytical parameters selected are chosen to be appropriate for the decision making process or to establish acceptable normality.
Water chemistry analysis is often the groundwork of studies of water quality, pollution, hydrology and geothermal waters.
Analytical methods routinely used can detect and measure all the natural elements and their inorganic compounds and a very wide range of organic chemical species using methods such as gas chromatography and mass spectrometry. In water treatment plants producing drinking water and in some industrial processes using products with distinctive taste and odours, specialised organoleptic methods may be used to detect smells at very low concentrations. | 9 | Geochemistry |
Coal-tar creosote is the most widely used wood treatment today; both industrially, processed into wood using pressure methods such as "full-cell process" or "empty-cell process", and more commonly applied to wood through brushing. In addition to toxicity to fungi, insects, and marine borers, it serves as a natural water repellent. It is commonly used to preserve and waterproof railroad ties, pilings, telephone poles, power line poles, marine pilings, and fence posts. Although suitable for use in preserving the structural timbers of buildings, it is not generally used that way because it is difficult to apply. There are also concerns about the environmental impact of the leaching of creosote into aquatic ecosystems.
Due to its carcinogenic character, the European Union has regulated the quality of creosote for the EU market and requires that the sale of creosote be limited to professional users. The United States Environmental Protection Agency regulates the use of coal-tar creosote as a wood preservative under the provisions of the Federal Insecticide, Fungicide, and Rodenticide Act. Creosote is considered a restricted-use pesticide and is only available to licensed pesticide applicators. | 7 | Physical Chemistry |
EDLs have an additional parameter defining their characterization: differential capacitance. Differential capacitance, denoted as C, is described by the equation below:
where σ is the surface charge and ψ is the electric surface potential. | 7 | Physical Chemistry |
In chemistry, a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular bipyramid. This is one geometry for which the bond angles surrounding the central atom are not identical (see also pentagonal bipyramid), because there is no geometrical arrangement with five terminal atoms in equivalent positions. Examples of this molecular geometry are phosphorus pentafluoride (), and phosphorus pentachloride () in the gas phase. | 4 | Stereochemistry |
The average coverage for a whole genome can be calculated from the length of the original genome (G), the number of reads (N), and the average read length (L) as . For example, a hypothetical genome with 2,000 base pairs reconstructed from 8 reads with an average length of 500 nucleotides will have 2× redundancy. This parameter also enables one to estimate other quantities, such as the percentage of the genome covered by reads (sometimes also called breadth of coverage). A high coverage in shotgun sequencing is desired because it can overcome errors in base calling and assembly. The subject of DNA sequencing theory addresses the relationships of such quantities. | 1 | Biochemistry |
In retrosynthetic analysis, a synthon is a hypothetical unit within a target molecule that represents a potential starting reagent in the retroactive synthesis of that target molecule. The term was coined in 1967 by E. J. Corey. He noted in 1988 that the "word synthon has now come to be used to mean synthetic building block rather than retrosynthetic fragmentation structures".
It was noted in 1998 that the phrase did not feature very prominently in Coreys 1981 book The Logic of Chemical Synthesis', as it was not included in the index. Because synthons are charged, when placed into a synthesis an uncharged form is found commercially instead of forming and using the potentially very unstable charged synthons. | 0 | Organic Chemistry |
The presence of nearby particles will affect the radiation emitted by an individual particle. There are two limiting cases by which this occurs:
* Impact pressure broadening or collisional broadening: The collision of other particles with the light emitting particle interrupts the emission process, and by shortening the characteristic time for the process, increases the uncertainty in the energy emitted (as occurs in natural broadening). The duration of the collision is much shorter than the lifetime of the emission process. This effect depends on both the density and the temperature of the gas. The broadening effect is described by a Lorentzian profile and there may be an associated shift.
* Quasistatic pressure broadening: The presence of other particles shifts the energy levels in the emitting particle (see spectral band), thereby altering the frequency of the emitted radiation. The duration of the influence is much longer than the lifetime of the emission process. This effect depends on the density of the gas, but is rather insensitive to temperature. The form of the line profile is determined by the functional form of the perturbing force with respect to distance from the perturbing particle. There may also be a shift in the line center. The general expression for the lineshape resulting from quasistatic pressure broadening is a 4-parameter generalization of the Gaussian distribution known as a stable distribution.
Pressure broadening may also be classified by the nature of the perturbing force as follows:
* Linear Stark broadening occurs via the linear Stark effect, which results from the interaction of an emitter with an electric field of a charged particle at a distance , causing a shift in energy that is linear in the field strength.
* Resonance broadening occurs when the perturbing particle is of the same type as the emitting particle, which introduces the possibility of an energy exchange process.
* Quadratic Stark broadening occurs via the quadratic Stark effect, which results from the interaction of an emitter with an electric field, causing a shift in energy that is quadratic in the field strength.
* Van der Waals broadening occurs when the emitting particle is being perturbed by Van der Waals forces. For the quasistatic case, a Van der Waals profile is often useful in describing the profile. The energy shift as a function of distance between the interacting particles is given in the wings by e.g. the Lennard-Jones potential. | 7 | Physical Chemistry |
Molecular cloning is used to isolate and then transfer a DNA sequence of interest into a plasmid vector. This recombinant DNA technology was first developed in the 1960s. In this technique, a DNA sequence coding for a protein of interest is cloned using polymerase chain reaction (PCR), and/or restriction enzymes, into a plasmid (expression vector). The plasmid vector usually has at least 3 distinctive features: an origin of replication, a multiple cloning site (MCS), and a selective marker (usually antibiotic resistance). Additionally, upstream of the MCS are the promoter regions and the transcription start site, which regulate the expression of cloned gene.
This plasmid can be inserted into either bacterial or animal cells. Introducing DNA into bacterial cells can be done by transformation via uptake of naked DNA, conjugation via cell-cell contact or by transduction via viral vector. Introducing DNA into eukaryotic cells, such as animal cells, by physical or chemical means is called transfection. Several different transfection techniques are available, such as calcium phosphate transfection, electroporation, microinjection and liposome transfection. The plasmid may be integrated into the genome, resulting in a stable transfection, or may remain independent of the genome and expressed temporarily, called a transient transfection.
DNA coding for a protein of interest is now inside a cell, and the protein can now be expressed. A variety of systems, such as inducible promoters and specific cell-signaling factors, are available to help express the protein of interest at high levels. Large quantities of a protein can then be extracted from the bacterial or eukaryotic cell. The protein can be tested for enzymatic activity under a variety of situations, the protein may be crystallized so its tertiary structure can be studied, or, in the pharmaceutical industry, the activity of new drugs against the protein can be studied. | 1 | Biochemistry |
Liming can also improve aggregate stability on clay soils. For this purpose structure lime, products containing calcium oxide (CaO) or hydroxide (Ca(OH)) in mixes with calcium carbonate (CaCO), are often used. Structure liming can reduce losses of clay and nutrients from soil aggregates. The degree to which a given amount of lime per unit of soil volume will increase soil pH depends on the buffer capacity of the soil (this is generally related to soil cation exchange capacity or CEC).
Most acid soils are saturated with aluminum rather than hydrogen ions. The acidity of the soil is therefore a result of hydrolysis of aluminum. This concept of "corrected lime potential" to define the degree of base saturation in soils became the basis for procedures now used in soil testing laboratories to determine the "lime requirement" of soils.
Soils with low CEC will usually show a more marked pH increase than soils with high CEC. But the low-CEC soils will witness more rapid leaching of the added bases, and so will see a quicker return to original acidity unless additional liming is done. Over-liming is most likely to occur on soil that has low CEC, such as sand which is deficient in buffering agents such as organic matter and clay. | 9 | Geochemistry |
Substituted tryptamines, or serotonin analogues, are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all tryptamines contain an indole ring, joined to an amino (NH) group via an ethyl (−CH2–CH2−) sidechain. In substituted tryptamines, the indole ring, sidechain, and/or amino group are modified by substituting another group for one of the hydrogen (H) atoms.
Well-known tryptamines include serotonin, an important neurotransmitter, and melatonin, a hormone involved in regulating the sleep-wake cycle. Tryptamine alkaloids are found in fungi, plants and animals; and sometimes used by humans for the neurological or psychotropic effects of the substance. Prominent examples of tryptamine alkaloids include psilocybin (from "psilocybin mushrooms") and DMT. In South America, dimethyltryptamine is obtained from numerous plant sources, like chacruna, and it is often used in ayahuasca brews. Many synthetic tryptamines have also been made, including the migraine drug sumatriptan, and psychedelic drugs. A 2022 study has found the variety of tryptamines present in wild mushrooms may affect the therapeutic impact.
The tryptamine structure, in particular its indole ring, may be part of the structure of some more complex compounds, for example: LSD, ibogaine, mitragynine and yohimbine. A thorough investigation of dozens of tryptamine compounds was published by Ann and Alexander Shulgin under the title TiHKAL. | 0 | Organic Chemistry |
Racemic Photo-Methionine is synthesized from 4,4'-azi-pentanal by the Strecker amino acid synthesis. The enantiomer is separated by enzymatic resolution of the acetamide. | 5 | Photochemistry |
The GUS reporter system (GUS: β-glucuronidase) is a reporter gene system, particularly useful in plant molecular biology and microbiology. Several kinds of GUS reporter gene assay are available, depending on the substrate used. The term GUS staining refers to the most common of these, a histochemical technique. | 1 | Biochemistry |
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