text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
α,β-Unsaturated carbonyls are electrophilic at both the carbonyl carbon as well as the β-carbon. Depending on conditions, either site is attacked by nucleophiles. Additions to the alkene are called conjugate additions. One type of conjugate addition is the Michael addition, which is used commercially in the conversion of mesityl oxide into isophorone. Owing to their extended conjugation, α,β-unsaturated carbonyls are prone to polymerization. In terms of industrial scale, polymerization dominates the use of α,β-unsaturated carbonyls. Again because of their electrophilic character, the alkene portion of α,β-unsaturated carbonyls is good dienophiles in Diels–Alder reactions. They can be further activated by Lewis acids, which bind to the carbonyl oxygen. α,β-Unsaturated carbonyls are good ligands for low-valent metal complexes, examples being Fe(bda)(CO) and tris(dibenzylideneacetone)dipalladium(0).
α,β-Unsaturated carbonyls are readily hydrogenated. Hydrogenation can target the carbonyl or the alkene (conjugate reduction) selectively, or both functional groups.
Enones undergo the Nazarov cyclization reaction and in the Rauhut–Currier reaction (dimerization). | 0 | Theoretical and Fundamental Chemistry |
In 1921, Mieli founded the Società italiana per lo studio delle questioni sessuali (Italian society for the study of sexual matters), an organisation to discuss sexuality and sexology. He also founded the journal Rassegna di Studi Sessuali (Sexual Studies Review). The journal published a range of topics on sex and sexuality, notably including the works of Magnus Hirschfeld. Hirschfield and Mieli had both been members of the organizing committee of the first Congress of Sexology, in Berlin, held earlier that year in 1921.
These activities formed part of Mieli's strategy to encourage public debate on sexual issues with a view to changing government policies on sexuality. He considered homosexuality a "completely natural fact, not something to cure but to be analysed with a high degree of objectivity", which Benadusi notes was an "absolute novelty". | 1 | Applied and Interdisciplinary Chemistry |
Retinal guanylyl cyclase 1 also known as guanylate cyclase 2D, retinal is an enzyme that in humans is encoded by the GUCY2D (guanylate cyclase 2D) gene. | 1 | Applied and Interdisciplinary Chemistry |
Crude oil is a mixture of many varieties of hydrocarbons and most usually have many sulfur-containing compounds. The oil refining process commonly includes hydrodesulfurization which converts most of that sulfur into gaseous hydrogen sulfide. Raw natural gas also may contain gaseous hydrogen sulfide and sulfur-containing mercaptans, which are removed in natural-gas processing plants before the gas is distributed to consumers.
The hydrogen sulfide removed in the refining and processing of crude oil and natural gas is subsequently converted into byproduct elemental sulfur. In fact, the vast majority of the 64,000,000 metric tons of sulfur produced worldwide in 2005 was byproduct sulfur from refineries and natural-gas processing plants. | 1 | Applied and Interdisciplinary Chemistry |
FAST pertains to a chemical-genetic strategy for specific labeling of proteins. A peptide domain, called "tag", is genetically encoded to be bound to a protein of interest (by combination of their respective genes by means of transfection or infection). This tag is the anchor for a synthetic fluorescent probe to be further added. Such chemical-genetic approach was already implemented besides natural fluorescent proteins such as GFP or their derivatives such as mCherry in several systems already widely used:
* since 2003, SNAP-tag, a bi-component reporting system consisting of a 19 kDa peptide derived from a human enzyme, O-methylguanine-ADN methyltransferase, evolved to form covalent bonds with fluorescent O-benzylguanine derivatives; SNAP-tag was later evolved into an orthogonal tag, CLIP-tag;
* since 2008, HaloTag, a bi-component reporting system consisting of a 33 kDa peptide derived from a bacterial enzyme, a haloalkane deshalogenase, which can specifically bind functional halogenated synthetic ligands, most often fluorescent for cell imaging (e.g., Coumarine, Oregon Green, Alexa Fluor 488, diAcFAM, TMR).
Several versions of FAST have been described differing by a small number of mutations, e.g., FAST1 (a.k.a. Y-FAST), FAST2 (a.k.a. iFAST), or a dimer, td-FAST. Also, a complementation split version for monitoring protein-protein interactions was developed, splitFAST. A number of plasmids displaying FAST or splitFAST genes are available at Addgene. | 1 | Applied and Interdisciplinary Chemistry |
Fractional crystallization and accumulation of crystals formed during the differentiation process of a magmatic event are known as cumulate rocks, and those parts are the first which crystallize out of the magma. Identifying whether a rock is a cumulate or not is crucial for understanding if it can be modelled back to a primary melt or a primitive melt, and identifying whether the magma has dropped out cumulate minerals is equally important even for rocks which carry no phenocrysts. | 0 | Theoretical and Fundamental Chemistry |
It's a popular firecracker item in India, which children play with during the festival of Diwali. Though deemed toxic by the Chest Research foundation and Pune University, black snake fireworks are still in use. The objective of the study was to determine which firework produced the most air pollution in India. The conducted study showed that the snake fireworks emitted the highest particulate matter, capable of penetrating the lungs via inhalation of smoke particles and consequently, causing significant damage. Other firecrackers that emit huge amounts of smoke particles include fuljhadi, pulpul, chakris and annar. | 1 | Applied and Interdisciplinary Chemistry |
Low temperature heat contains very little capacity to do work (Exergy), so the heat is qualified as waste heat and rejected to the environment. Economically most convenient is the rejection of such heat to water from a sea, lake or river. If sufficient cooling water is not available, the plant can be equipped with a cooling tower or air cooler to reject the waste heat into the atmosphere. In some cases it is possible to use waste heat, for instance in district heating systems. | 0 | Theoretical and Fundamental Chemistry |
Polymer solutions are solutions containing dissolved polymers. These may be (e.g. in ), or solid solutions (e.g. a substance which has been plasticized).
The introduction into the polymer of small amounts of a solvent (plasticizer) reduces the temperature of glass transition, the yield temperature, and the viscosity of a melt.
An understanding of the thermodynamics of a polymer solution is critical to prediction of its behavior in manufacturing processes — for example, its shrinkage or expansion in injection molding processes, or whether pigments and solvents will mix evenly with a polymer in the manufacture of paints and coatings. A recent theory on the viscosity of polymer solutions gives a physical explanation for various well-known empirical relations and numerical values including the Huggins constant, but reveals also novel simple concentration and molar mass dependence. | 0 | Theoretical and Fundamental Chemistry |
The exact size of the GPCR superfamily is unknown, but at least 831 different human genes (or about 4% of the entire protein-coding genome) have been predicted to code for them from genome sequence analysis. Although numerous classification schemes have been proposed, the superfamily was classically divided into three main classes (A, B, and C) with no detectable shared sequence homology between classes.
The largest class by far is class A, which accounts for nearly 85% of the GPCR genes. Of class A GPCRs, over half of these are predicted to encode olfactory receptors, while the remaining receptors are liganded by known endogenous compounds or are classified as orphan receptors. Despite the lack of sequence homology between classes, all GPCRs have a common structure and mechanism of signal transduction. The very large rhodopsin A group has been further subdivided into 19 subgroups (A1-A19).
According to the classical A-F system, GPCRs can be grouped into six classes based on sequence homology and functional similarity:
*Class A (or 1) (Rhodopsin-like)
*Class B (or 2) (Secretin receptor family)
*Class C (or 3) (Metabotropic glutamate/pheromone)
*Class D (or 4) (Fungal mating pheromone receptors)
*Class E (or 5) (Cyclic AMP receptors)
*Class F (or 6) (Frizzled/Smoothened)
More recently, an alternative classification system called GRAFS (Glutamate, Rhodopsin, Adhesion, Frizzled/Taste2, Secretin) has been proposed for vertebrate GPCRs. They correspond to classical classes C, A, B2, F, and B.
An early study based on available DNA sequence suggested that the human genome encodes roughly 750 G protein-coupled receptors, about 350 of which detect hormones, growth factors, and other endogenous ligands. Approximately 150 of the GPCRs found in the human genome have unknown functions.
Some web-servers and bioinformatics prediction methods have been used for predicting the classification of GPCRs according to their amino acid sequence alone, by means of the pseudo amino acid composition approach. | 1 | Applied and Interdisciplinary Chemistry |
Dissolved ions may affect the suitability of water for a range of industrial and domestic purposes. The most familiar of these is probably the presence of calcium (Ca) and magnesium (Mg) that interfere with the cleaning action of soap, and can form hard sulfate and soft carbonate deposits in water heaters or boilers. Hard water may be softened to remove these ions. The softening process often substitutes sodium cations. For certain populations, hard water may be preferable to soft water because health problems have been associated with calcium deficiencies and with excess sodium. The necessity for additional calcium and magnesium in water depends on the population in question because people generally satisfy their recommended amounts through food. | 0 | Theoretical and Fundamental Chemistry |
For electron backscattering diffraction microscopy, a flat polished crystalline specimen is usually placed inside the microscope chamber. The sample is tilted at ~70° from Scanning electron microscope (SEM) flat specimen positioning and 110° to the electron backscatter diffraction (EBSD) detector. Tilting the sample elongates the interaction volume perpendicular to the tilt axis, allowing more electrons to leave the sample providing better signal. A high-energy electron beam (typically 20 kV) is focused on a small volume and scatters with a spatial resolution of ~20 nm at the specimen surface. The spatial resolution varies with the beam energy, angular width, interaction volume, nature of the material under study, and, in transmission Kikuchi diffraction (TKD), with the specimen thickness; thus, increasing the beam energy increases the interaction volume and decreases the spatial resolution.
The EBSD detector is located within the specimen chamber of the SEM at an angle of approximately 90° to the pole piece. The EBSD detector is typically a phosphor screen that is excited by the backscattered electrons. The screen is coupled to lens which focuses the image from the phosphor screen onto a charge-coupled device (CCD) or complementary metal–oxide–semiconductor (CMOS) camera.
In this configuration, as the backscattered electrons leave the sample, they interact with the Coulomb potential and also lose energy due to inelastic scattering leading to a range of scattering angles (θ). The backscattered electrons form Kikuchi lines – having different intensities – on an electron-sensitive flat film/screen (commonly phosphor), gathered to form a Kikuchi band. These Kikuchi lines are the trace of a hyperbola formed by the intersection of Kossel cones with the plane of the phosphor screen. The width of a Kikuchi band is related to the scattering angles and, thus, to the distance d between lattice planes with Miller indexes h, k, and l. These Kikuchi lines and patterns were named after Seishi Kikuchi, who, together with , was the first to notice this diffraction pattern in 1928 using transmission electron microscopy (TEM) which is similar in geometry to X-ray Kossel pattern.
The systematically arranged Kikuchi bands, which have a range of intensity along their width, intersect around the centre of the regions of interest (ROI), describing the probed volume crystallography. These bands and their intersections form what is known as Kikuchi patterns or electron backscatter patterns (EBSPs). To improve contrast, the patterns’ background is corrected by removing anisotropic/inelastic scattering using static background correction or dynamic background correction. | 0 | Theoretical and Fundamental Chemistry |
The most common mammalian expression systems are Chinese Hamster ovary (CHO) and Human embryonic kidney (HEK) cells.
* Chinese hamster ovary cell
* Mouse myeloma lymphoblstoid (e.g. NS0 cell)
* Fully Human
** Human embryonic kidney cells (HEK-293)
** Human embryonic retinal cells (Crucell's Per.C6)
** Human amniocyte cells (Glycotope and CEVEC) | 1 | Applied and Interdisciplinary Chemistry |
Neoendorphins are a group of endogenous opioid peptides derived from the proteolytic cleavage of prodynorphin. They include α-neoendorphin and β-neoendorphin. The α-neoendorphin is present in greater amounts in the brain than β-neoendorphin. Both are products of the dynorphin gene, which also expresses dynorphin A, dynorphin A-(1-8), and dynorphin B. These opioid neurotransmitters are especially active in Central Nervous System receptors, whose primary function is pain sensation. These peptides all have the consensus amino acid sequence of Try-Gly-Gly-Phe-Met (met-enkephalin) or Tyr-Gly-Gly-Phe-Leu ( leu-enkephalin). Binding of neoendorphins to opioid receptors (OPR), in the dorsal root ganglion (DRG) neurons results in the reduction of time of calcium-dependent action potential. The α-neoendorphins bind OPRD1(delta), OPRK1(kappa), and OPRM1 (mu) and β-neoendorphin bind OPRK1. | 1 | Applied and Interdisciplinary Chemistry |
Repeated experiments are performed to characterize the mechanism by which the material deforms. The dominant mechanism is the one which dominates the continuous deformation rate (strain rate), however at any given level of stress and temperature, more than one of the creep and plasticity mechanisms may be active. The boundaries between the fields are determined from the constitutive equations of the deformation mechanisms by solving for stress as a function of temperature. Along these boundaries, the deformation rates for the two neighboring mechanisms are equal. The programming code used for many of the published maps is open source
and an archive of its development is online. Many researchers have also written their own codes to make these maps.
The main regions in a typical deformation mechanism map and their constitutive equations are shown in the following subsections. | 1 | Applied and Interdisciplinary Chemistry |
Manganese-mediated coupling reactions are radical coupling reactions between enolizable carbonyl compounds and unsaturated compounds initiated by a manganese(III) salt, typically manganese(III) acetate. Copper(II) acetate is sometimes used as a co-oxidant to assist in the oxidation of intermediate radicals to carbocations.
Manganese(III) acetate is effective for the one-electron oxidation of enolizable carbonyl compounds to α-oxoalkyl or α,α'-dioxoalkyl radicals. Radicals generated in this manner may then undergo inter- or intramolecular addition to carbon-carbon multiple bonds. Pathways available to the adduct radical include further oxidation to a carbocation (and subsequent β-elimination or trapping with a nucleophile) and hydrogen abstraction to generate a saturated carbonyl compound containing a new carbon-carbon bond. Copper(II) acetate is sometimes needed to facilitate the oxidation of adduct radicals to carbocations. Yields of these reactions are generally moderate, particularly in the intermolecular case, but tandem intramolecular radical cyclizations initiated by Mn(III) oxidation may generate complex carbocyclic frameworks. Because of the limited functional group compatibility of Mn(OAc), radical couplings employing this reagent have mainly been applied to the synthesis of hydrocarbon natural products, such as pheromones. | 0 | Theoretical and Fundamental Chemistry |
On this scale, pure HSO (18.4 M) has a H value of −12, and pyrosulfuric acid has H ~ −15. Take note that the Hammett acidity function clearly avoids water in its equation. It is a generalization of the pH scale—in a dilute aqueous solution (where B is HO), pH is very nearly equal to H. By using a solvent-independent quantitative measure of acidity, the implications of the leveling effect are eliminated, and it becomes possible to directly compare the acidities of different substances (e.g. using pK, HF is weaker than HCl or HSO in water but stronger than HCl in glacial acetic acid.)
H for some concentrated acids:
* Helonium: −63
* Fluoroantimonic acid (1990): −23 > H > −28
* Magic acid (1974): −23
* Carborane superacids: H < −18.0
* Fluorosulfuric acid (1944): −15.1
*Hydrogen fluoride: −15.1
*Trifluoromethanesulfonic acid (1940): −14.9
*Perchloric acid: −13
* Sulfurochloridic acid: −13.8; −12.78
* Sulfuric acid: −12.0
For mixtures (e.g., partly diluted acids in water), the acidity function depends on the composition of the mixture and has to be determined empirically. Graphs of H vs mole fraction can be found in the literature for many acids. | 0 | Theoretical and Fundamental Chemistry |
#Antibody coating: Throughout the ELISpot Assay technique, different substances are added to and washed away from wells. Wells are found on a laboratory plate with tiny dishes/bowls that can be filled with a substance to be examined; the amount of wells on a plate varies, but it usually ranges from 16-100. The first substance added to the wells are cytokine specific monoclonal antibodies. These antibodies coat the walls of the wells for future binding to cytokine. The monoclonal antibodies means that the antibody is produced from a single cell lineage, and is only able to bind to one protein epitope. Polyclonal antibodies, on the other hand, are capable of binding to multiple epitopes of the same protein.
#Cell incubation: The desired cells being observed and analyzed are added to the wells. Each well can have the presence or absence of stimuli that activate the secretion of cytokine in cells. During cell incubation, the cells are allowed to react to any present stimuli and secrete cytokine. There are many procedures and methods to follow to ensure proper cell handling. To make sure that cells are of high quality, cells in blood samples should be lightly agitated if stored for longer than 3 hours, the blood samples should be diluted in PBS (phosphate buffered saline) before being stored, and the blood samples should not have granulocytes. Any cells that have been cryopreserved and thawed should be allowed to rest for an hour or more at 37 degrees Celsius (the typical temperature of the human body). There are also many things that should be taken into consideration when incubating the cells, such as making sure that the cells do not experience sudden movements that could affect spot formation, or that the incubator's humidity is high enough to avoid excessive evaporation and drying out the wells.
#Cytokine capture: Since the cells are surrounded by cytokine specific monoclonal antibodies that coat the walls of the wells, cytokine that has been secreted by the incubated cells will start to attach to the antibodies at a specific epitope.
#Detection antibodies: At this point, the wells must be rinsed in order to get rid of the cells and any other undesirable substances. All that should remain are the cytokine specific monoclonal antibodies and any cytokine that bonded to the antibodies. Biotinylated cytokine-specific detection antibodies are then added to the well. These cytokine-specific detection antibodies will bind to any cytokine that is left in the well since the cytokine is still attached to the first set of antibodies used. Since the cytokine attached to the first set of antibodies coating the wells, the cytokine was not washed away when the wells were rinsed.
#Streptavidin-enzyme conjugate: Streptavidin-enzyme conjugate is added to the wells in order to bind with the detection antibodies. The purpose of biotinylating the cytokine-specific detection antibodies added to the wells in the previous step is so that the antibody can bind to the new streptavidin-enzyme conjugate. Biotinylation basically creates a strong affinity between the biotin on the cytokine-specific antibody and the streptavidin on the conjugate.
#Addition of substrate: A substrate is added to the wells, and is catalyzed by the enzyme conjugate added in the previous step. This reaction forms insoluble precipitate that forms spots in the wells. The substrate that you use in this step will depend on the type of enzyme used in the previous step. If streptavidin-ALP (streptavidin and alkaline phosphatase conjugate) is used, then using BCIP/NBT-plus (a mixture of 5-bromo-4-chloro-3-indolyl phosphate and nitroblue tetrazolium chloride) as a substrate will produce more distinct spots that are easier to analyze. If streptavidin-HRP (streptavidin and horseradish peroxidase conjugate) is used, then using TMB (tetramethylbenzidine) as a substrate will produce better results.
#Analysis: The spots that are formed can then be read on an automated ELISpot reader, or counted under a dissection microscope, and further used to calculate the frequency of cytokine secretion. | 1 | Applied and Interdisciplinary Chemistry |
Drahoš considers himself a centrist politician. As a candidate, Jiří Drahoš has presented himself as someone who can unite society, and as a respectable person who would act according to the constitution. Drahoš emphasises the importance of Czech science and education and has called for solidarity with those "who cannot take care of themselves". He has called for a "responsible approach" to the landscape and environment and has described human reason, creativity and ingeniousness as the only "renewable resource" of the wealth of the Czech Republic.
Drahoš wants the Czech Republic to play an active role in discussions over the future of the European Union, and wants the country to be a part of the Western world. He supports European integration but has said that he believes that the European Union should not impose unnecessary regulations on member states. He also said that he would not rush into Czech adoption of the Euro. Drahoš opposes a referendum about Czech membership of the European Union, and said that important geopolitical questions should not be decided by referendum. He supports the Czech Republic's membership of NATO.
In August 2015, Drahoš signed a petition named "scientists against fear and apathy" in opposition to both anti-Islamic radicalism and anti-immigrant populism.
Drahoš suggested that the Catalan independence referendum was "not legal", supporting the position of the Spanish government.
Drahoš says he supports the anti-Russian sanctions imposed by the United States and the EU. However he also said that having good relations with Russia is in the interest of the Czech Republic and European Union. Drahoš supports trade and economic relations with China, arguing that "China is a superpower" and "many countries are doing business with China."
In 2017, Drahoš rejected the European Unions proposal of compulsory migrant quotas, saying, "there is no successful model of Muslim integration in Europe". Drahoš also said that "Europe cant feed 100 million Africans, it is necessary to help them at home."
Drahoš described the pre-war German minority in Czechoslovakia as "Adolf Hitler's fifth column", and said that he agreed with the post-war expulsion of Germans from Czechoslovakia.
Drahoš has described himself as a sympathizer with Israel. | 0 | Theoretical and Fundamental Chemistry |
The exact mechanism of the enhancement effect of SERS is still a matter of debate in the literature. There are two primary theories and while their mechanisms differ substantially, distinguishing them experimentally has not been straightforward. The electromagnetic theory proposes the excitation of localized surface plasmons, while the chemical theory proposes the formation of charge-transfer complexes. The chemical theory is based on resonance Raman spectroscopy, in which the frequency coincidence (or resonance) of the incident photon energy and electron transition greatly enhances Raman scattering intensity. Research in 2015 on a more powerful extension of the SERS technique called SLIPSERS (Slippery Liquid-Infused Porous SERS) has further supported the EM theory. | 0 | Theoretical and Fundamental Chemistry |
*1st degree order of the Great Patriotic War
*State Prize of the Republic of Azerbaijan (1980)
*Y. Mammadaliyev medal (1995)
*Shohrat Order (2005)
* "OGS" golden medal and diploma (2006)
*Honorary title of Honored Scientist (2009)
*Y. Mammadaliyev prize (2014)
*Sharaf Order (2014) | 0 | Theoretical and Fundamental Chemistry |
The simplest non-Kekulé molecules are biradicals. A biradical is an even-electron chemical compound with two free radical centres which act independently of each other. They should not be confused with the more general class of diradicals.
One of the first biradicals was synthesized by Wilhelm Schlenk in 1915 following the same methodology as Moses Gomberg's triphenylmethyl radical. The so-called Schlenk-Brauns hydrocarbons are:
Eugene Müller, with the aid of a Gouy balance, established for the first time that these compounds are paramagnetic with a triplet ground state.
Another classic biradical was synthesised by Aleksei Chichibabin in 1907. Other classical examples are the biradicals described by Yang in 1960 and by Coppinger in 1962. | 0 | Theoretical and Fundamental Chemistry |
The ozone layer or ozone shield is a region of Earths stratosphere that absorbs most of the Suns ultraviolet radiation. It contains a high concentration of ozone (O) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately above Earth, although its thickness varies seasonally and geographically.
The ozone layer was discovered in 1913 by French physicists Charles Fabry and Henri Buisson. Measurements of the sun showed that the radiation sent out from its surface and reaching the ground on Earth is usually consistent with the spectrum of a black body with a temperature in the range of , except that there was no radiation below a wavelength of about 310 nm at the ultraviolet end of the spectrum. It was deduced that the missing radiation was being absorbed by something in the atmosphere. Eventually the spectrum of the missing radiation was matched to only one known chemical, ozone. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958, Dobson established a worldwide network of ozone monitoring stations, which continue to operate to this day. The "Dobson unit", a convenient measure of the amount of ozone overhead, is named in his honor.
The ozone layer absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which otherwise would potentially damage exposed life forms near the surface.
In 1985, atmospheric research revealed that the ozone layer was being depleted by chemicals released by industry, mainly chlorofluorocarbons (CFCs). Concerns that increased UV radiation due to ozone depletion threatened life on Earth, including increased skin cancer in humans and other ecological problems, led to bans on the chemicals, and the latest evidence is that ozone depletion has slowed or stopped. The United Nations General Assembly has designated September 16 as the International Day for the Preservation of the Ozone Layer.
Venus also has a thin ozone layer at an altitude of 100 kilometers above the planet's surface. | 0 | Theoretical and Fundamental Chemistry |
The manufacturing process is similar to that of ordinary coins, except that two blanks (the inner and the outer) are struck at the same time, deforming the separate blanks sufficiently to hold them together. | 1 | Applied and Interdisciplinary Chemistry |
In nuclear physics, a beta decay transition is the change in state of an atomic nucleus undergoing beta decay. (β-decay) When undergoing beta decay, a nucleus emits a beta particle and a corresponding neutrino, transforming the original nuclide into one with the same mass, but differing charge. (an isobar)
There are several types of beta decay transition. In a Fermi transition, the spins of the two emitted particles are anti-parallel, for a combined spin . As a result, the total angular momentum of the nucleus is unchanged by the transition. By contrast, in a Gamow-Teller transition, the spins of the two emitted particles are parallel, with total spin , leading to a change in angular momentum between the initial and final states of the nucleus.
The theoretical work in describing these transitions was done between 1934 and 1936 by George Gamow and Edward Teller at George Washington University. | 0 | Theoretical and Fundamental Chemistry |
The Tepper-García function, named after German-Mexican Astrophysicist Thor Tepper-García, is a combination of an exponential function and rational functions that approximates the line broadening function over a wide range of its parameters.
It is obtained from a truncated power series expansion of the exact line broadening function.
In its most computationally efficient form, the Tepper-García function can be expressed as
where , , and .
Thus the line broadening function can be viewed, to first order, as a pure Gaussian function plus a correction factor that depends linearly on the microscopic properties of the absorbing medium (encoded in ); however, as a result of the early truncation in the series expansion, the error in the approximation is still of order , i.e. . This approximation has a relative accuracy of
over the full wavelength range of , provided that .
In addition to its high accuracy, the function is easy to implement as well as computationally fast. It is widely used in the field of quasar absorption line analysis. | 0 | Theoretical and Fundamental Chemistry |
In a semiconductors, if all oscillations have the same eigenfrequency and the broadening in the imaginary part of the dielectric function results only from a finite damping , the system is said to be homogeneously broadened, and has a Lorentzian profile. If the system contains many oscillators with slightly different frequencies about however, then the system is inhomogeneously broadened. | 0 | Theoretical and Fundamental Chemistry |
*2024: Humboldt Research Award
*2018: Madhuri and Jagdish N. Sheth International Alumni Award for Exceptional Achievement (University of Illinois)
*2015: Ho-Am Prize in Science (HOAM Foundation)
*2014: The World's Most Influential Scientific Minds (Thomson Reuters)
*2013: KCS Academic Achievement Award (Korean Chemical Society)
*2012: POSCO TJ Park Prize (POSCO TJ Park Foundation)
*2012: Korea's 100 Most Influential Person for Next 10 Years (DongA Daily News)
*2010: Inchon Prize (Inchon Memorial Foundation)
*2007: Song-Gok Science Prize (Korea Institute of Science and Technology)
*2004: KCS Award in Inorganic Chemistry (Korean Chemical Society)
*2002: Young Scientist Award, Korean Academy of Science and Technology
*2001: Wiley Young Chemist Award (Korean Chemical Society-Wiley & Sons) | 0 | Theoretical and Fundamental Chemistry |
Several approaches to simulate NMR observables of carbohydrates has been reviewed. They include:
*Universal statistical database approaches (ACDLabs, Modgraph, etc.)
*Usage of neural networks to refine the predictions
*Regression based methods
*CHARGE
*Carbohydrate-optimized empirical schemes (CSDB/BIOPSEL, CASPER).
*Combined molecular mechanics/dynamics geometry calculation and quantum-mechanical simulation/iteration of NMR observables (PERCH NMR Software)
*ONIOM approaches (optimization of different parts of molecule with different accuracy)
*Ab initio calculations.
Growing computational power allows usage of thorough quantum-mechanical calculations at high theory levels and large basis sets for refining the molecular geometry of carbohydrates and subsequent prediction of NMR observables using GIAO and other methods with or without solvent effect account. Among combinations of theory level and a basis set reported as sufficient for NMR predictions were B3LYP/6-311G++(2d,2p) and PBE/PBE (see review). It was shown for saccharides that carbohydrate-optimized empirical schemes provide significantly better accuracy (0.0-0.5 ppm per C resonance) than quantum chemical methods (above 2.0 ppm per resonance) reported as best for NMR simulations, and work thousands times faster. However, these methods can predict only chemical shifts and perform poor for non-carbohydrate parts of molecules.
As a representative example, see figure on the right. | 0 | Theoretical and Fundamental Chemistry |
The difference between pitting and micropitting is the size of the pits after surface fatigue. Pits formed by micropitting are approximately 10–20 μm in depth, and micropitted metal often has a frosted or gray appearance. Normal pitting creates larger and more visible pits. Micropits are originated from the local contact of asperities produced by improper lubrication. | 1 | Applied and Interdisciplinary Chemistry |
If quantum effects are negligible, an accelerating charged particle radiates power as described by the Larmor formula and its relativistic generalization. | 0 | Theoretical and Fundamental Chemistry |
Subsurface wetlands are less hospitable to mosquitoes compared to surface flow wetlands, as there is no water exposed to the surface. Mosquitos can be a problem in surface flow constructed wetlands. Subsurface flow systems have the advantage of requiring less land area for water treatment than surface flow. However, surface flow wetlands can be more suitable for wildlife habitat.
For urban applications the area requirement of a subsurface flow constructed wetland might be a limiting factor compared to conventional municipal wastewater treatment plants. High rate aerobic treatment processes like activated sludge plants, trickling filters, rotating discs, submerged aerated filters or membrane bioreactor plants require less space. The advantage of subsurface flow constructed wetlands compared to those technologies is their operational robustness which is particularly important in developing countries. The fact that constructed wetlands do not produce secondary sludge (sewage sludge) is another advantage as there is no need for sewage sludge treatment. However, primary sludge from primary settling tanks does get produced and needs to be removed and treated. | 1 | Applied and Interdisciplinary Chemistry |
Upamāna (उपमान) means comparison and analogy. Upamāna, states Lochtefeld, may be explained with the example of a traveller who has never visited lands or islands with endemic population of wildlife. He or she is told, by someone who has been there, that in those lands you see an animal that sort of looks like a cow, grazes like cow but is different from a cow in such and such way. Such use of analogy and comparison is, state the Indian epistemologists, a valid means of conditional knowledge, as it helps the traveller identify the new animal later. The subject of comparison is formally called upameyam, the object of comparison is called upamānam, while the attribute(s) are identified as sāmānya. Thus, explains Monier Williams, if a boy says "her face is like the moon in charmingness", "her face" is upameyam, the moon is upamānam, and charmingness is sāmānya. The 7th century text Bhaṭṭikāvya in verses 10.28 through 10.63 discusses many types of comparisons and analogies, identifying when this epistemic method is more useful and reliable, and when it is not. In various ancient and medieval texts of Hinduism, 32 types of Upamāna and their value in epistemology are debated. | 1 | Applied and Interdisciplinary Chemistry |
The table, like most shaking tables, consists of a riffled deck with a gentle tilt on a stable support to counteract the tables oscillation. A motor, usually mounted to the side, drives a small arm that shakes the table along its length. The riffles are typically less than high and cover more than half the tables surface. Varied riffle designs are available for specific applications. The riffles run longitudinally, parallel to the long dimension of the table. The table's shaking motion is parallel to the riffle pattern.
Deck construction varies from wood to hard-wearing fiberglass where the riffles are formed as part of the mold. The decks are lined with high coefficient-of-friction materials (linoleum, rubber or plastic), which assists in the mineral recovery process.
During operation, a slurry of < sample material consisting of about 25% solids by weight is fed with wash water along the top of the table, perpendicular to the direction of table motion. The table is shaken longitudinally, using a slow forward stroke and a rapid return strike that causes particles to migrate or crawl along the deck parallel to the direction of motion. Particles move diagonally across the deck from the feed end and separate on the table according to size and density. Water flow rate, table tilt angle and intensity of the shaking motion must be properly adjusted for effective mineral recovery.
The riffles cause mineral particles to stratify in the protected inter-riffle regions. The finest and heaviest particles are forced to the bottom and the coarsest and lightest particles remain at the top. Particle layers migrate across the riffles with addition of new slurry feed and continued water wash. The riffles are tapered and flatten (disappear) towards the concentrate end of the table. The taper of the riffles causes migrating particles of progressively finer size and higher density to be brought into contact with the flowing film of water that tops the riffles; lighter material is washed away as tailings and middlings. Final concentration takes place in the unriffled region at the end of the deck where the layer of material at this stage is usually only a few particles deep. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, ketonic decarboxylation (also known as decarboxylative ketonization) is a type of organic reaction and a decarboxylation converting two equivalents of a carboxylic acid () to a symmetric ketone () by the application of heat. It can be thought of as a decarboxylative Claisen condensation of two identical molecules. Water and carbon dioxide are byproducts:
Bases promote this reaction. The reaction mechanism likely involves nucleophilic attack of the alpha-carbon of one acid group on the other acid groups carbonyl (), possibly as a concerted reaction with the decarboxylation. The initial formation of an intermediate carbanion via decarboxylation of one of the acid groups prior to the nucleophilic attack has been proposed, but is unlikely since the byproduct resulting from the carbanions protonation by the acid has never been reported. This reaction is different from oxidative decarboxylation, which proceeds through a radical mechanism and is characterised by a different product distribution in isotopic labeling experiments with two different carboxylic acids. With two different carboxylic acids, the reaction behaves poorly because of poor selectivity except when one of the acids (for example, a small, volatile one) is used in large excess. | 0 | Theoretical and Fundamental Chemistry |
From the kinetic energy formula it can be shown that
where v is in m/s, T is in kelvin, and m is the mass of one molecule of gas in kg. The most probable (or mode) speed is 81.6% of the root-mean-square speed , and the mean (arithmetic mean, or average) speed is 92.1% of the rms speed (isotropic distribution of speeds).
See:
* Average,
* Root-mean-square speed
* Arithmetic mean
* Mean
* Mode (statistics) | 0 | Theoretical and Fundamental Chemistry |
Reverberatory furnaces are widely used to melt secondary aluminium scrap for eventual use by die-casting industries.
The simplest reverberatory furnace is nothing more than a steel box lined with alumina refractory brick with a flue at one end and a vertically lifting door at the other. Conventional oil or gas burners are placed usually on either side of the furnace to heat the brick and the eventual bath of molten metal is then poured into a casting machine to produce ingots. | 1 | Applied and Interdisciplinary Chemistry |
The rapid development in the multidisciplinary field of tissue engineering has resulted in a variety of new and innovative medicinal products, often carrying living cells, intended to repair, regenerate or replace damaged human tissue. Tissue engineered medicinal products (TEMPs) vary in terms of the type and origin of cells and the product’s complexity. As all medicinal products, the safety and efficacy of TEMPs must be consistent throughout the manufacturing process. Quality control and assurance are of paramount importance and products are constantly assessed throughout the manufacturing process to ensure their safety, efficacy, consistency and reproducibility between batches. The European Medicines Agency (EMA) is responsible for the development, assessment and supervision of medicines in the EU. The appointed committees are involved in referral procedures concerning safety or the balance of benefit/risk of a medicinal product. In addition, the committees organize inspections with regards to the conditions under which medicinal products are being manufactured. For example, the compliance with good manufacturing practice (GMP), good clinical practice (GCP), good laboratory practice (GLP) and pharmacovigilance (PhV). | 1 | Applied and Interdisciplinary Chemistry |
The Fick principle states that blood flow to an organ can be calculated using a marker substance if the following information is known:
* Amount of marker substance taken up by the organ per unit time
* Concentration of marker substance in arterial blood supplying the organ
* Concentration of marker substance in venous blood leaving the organ
Developed by Adolf Eugen Fick (1829–1901), the Fick principle has been applied to the measurement of cardiac output. Its underlying principles may also be applied in a variety of clinical situations.
In Ficks original method, the "organ" was the entire human body and the marker substance was oxygen. The first published mention was in conference proceedings from July 9, 1870 from a lecture he gave at that conference; it is this publishing that is most often used by articles to cite Ficks contribution.The principle may be applied in different ways. For example, if the blood flow to an organ is known, together with the arterial and venous concentrations of the marker substance, the uptake of marker substance by the organ may then be calculated. | 1 | Applied and Interdisciplinary Chemistry |
Regular pulses of glucocorticoids, mainly cortisol in the case of humans, are released regularly from the adrenal cortex following a circadian pattern in addition to their release as a part of the stress response. Cortisol release follows a high frequency of pulses forming an ultradian rhythm, with amplitude being the primary variation in its release, so that the signal is amplitude modulated. Glucocorticoid pulsatlity has been observed to follow a circadian rhythm, with highest levels observed before waking and before anticipated mealtimes. This pattern in amplitude of release is observed to be consistent across vertebrates. Studies done in humans, rats, and sheep have also observed a similar circadian pattern of release of adrenocorticotropin (ACTH) shortly preceding the pulse in the resulting corticosteroid. It is currently hypothesized that the observed pulsatility of ACTH and glucocorticoids is driven via pulsatility of corticotropin-releasing hormone (CRH), however there exists little data to support this due to difficulty in measuring CRH. | 1 | Applied and Interdisciplinary Chemistry |
Usually aminomethyl groups feature tertiary amines. Often they are obtained by alkylation with Eschenmoser's salt, a source of [CH=N(CH)].
A cobalt(III) complex of aminomethyl is known in the form [Co(bipyridine)(CHNH)](ClO4).
Aminomethyl is the first member of a series of 1-aminoalkyl groups of the form .
Aminomethyl is used in the standard (IUPAC) names of some compounds, such as 4-(aminomethyl) benzoic acid. | 0 | Theoretical and Fundamental Chemistry |
Ampicillin is used to treat infections by many gram-positive and gram-negative bacteria. It was the first "broad spectrum" penicillin with activity against gram-positive bacteria, including Streptococcus pneumoniae, Streptococcus pyogenes, some isolates of Staphylococcus aureus (but not penicillin-resistant or methicillin-resistant strains), Trueperella, and some Enterococcus. It is one of the few antibiotics that works against multidrug resistant Enterococcus faecalis and E. faecium. Activity against gram-negative bacteria includes Neisseria meningitidis, some Haemophilus influenzae, and some of the Enterobacteriaceae (though most Enterobacteriaceae and Pseudomonas are resistant). Its spectrum of activity is enhanced by co-administration of sulbactam, a drug that inhibits beta lactamase, an enzyme produced by bacteria to inactivate ampicillin and related antibiotics. It is sometimes used in combination with other antibiotics that have different mechanisms of action, like vancomycin, linezolid, daptomycin, and tigecycline. | 0 | Theoretical and Fundamental Chemistry |
The non-recombinants are separated from recombinants; i.e., a r-DNA is introduced in bacteria, some bacteria are successfully transformed some remain non-transformed. When grown on medium containing ampicillin, bacteria die due to lack of ampicillin resistance. The position is later noted on nitrocellulose paper and separated out to move them to nutrient medium for mass production of required product.
An alternative to a selectable marker is a screenable marker which can also be denoted as a reporter gene, which allows the researcher to distinguish between wanted and unwanted cells, e.g. between blue and white colonies. These wanted or unwanted cells are simply un-transformed cells that were unable to take up the gene during the experiment. | 1 | Applied and Interdisciplinary Chemistry |
In 1912, Hahn and Meitner moved to the newly founded Kaiser Wilhelm Institute (KWI) for Chemistry. Hahn accepted an offer from Fischer to become a junior assistant in charge of its radiochemistry section, the first laboratory of its kind in Germany. The job came with the title of "professor" and a salary of 5,000 marks per annum. Meitner worked without salary as a "guest" in Hahns section. Later that year, perhaps fearing that Meitner was in financial difficulties and might return to Vienna, since her father had died in 1910, Planck appointed her his assistant at the Institute for Theoretical Physics in the Friedrich Wilhelm University. As such, she marked his students papers. It was her first paid position. Assistant was the lowest rung on the academic ladder, and Meitner was the first female scientific assistant in Prussia.
Proud officials presented Meitner to Kaiser Wilhelm II at the official opening of the KWI for Chemistry on 23 October 1912. The following year she became a Mitglied (associate), the same rank as Hahn (although her salary was still less), and the radioactivity section became the Hahn-Meitner Laboratory. Meitner celebrated with a dinner party at the Hotel Adlon. Hahn and Meitners salaries would soon be dwarfed by royalties from mesothorium ("middle thorium", radium-228 also called "German radium") produced for medical purposes, for which Hahn received 66,000 marks in 1914, of which he gave ten per cent to Meitner. In 1914, Meitner received an attractive offer of an academic position in Prague. Planck made it clear to Fischer that he didnt want Meitner to leave, and Fischer arranged for her salary to be doubled to 3,000 marks.
The move to new accommodation was fortuitous, as the wood shop had become thoroughly contaminated by radioactive liquids that had been spilt, and radioactive gases that had vented and then decayed and settled as radioactive dust, making sensitive measurements impossible. To ensure that their clean new laboratories stayed that way, Hahn and Meitner instituted strict procedures. Chemical and physical measurements were conducted in different rooms, people handling radioactive substances had to follow protocols that included not shaking hands, and rolls of toilet paper were hung next to every telephone and door handle. Strongly radioactive substances were stored in the old wood shop, and later in a purpose-built radium house on the institute grounds. | 1 | Applied and Interdisciplinary Chemistry |
Bruyerinus Champier was the nephew of Symphorien Champier, and physician of Henry II of France. He was an Arabist, and translated works of Avicena. In 1550 he published his first Materia Medica, printed by Balthazar Arnoullet in Lyons. This work had a second edition in 1552 printed by Arnoullet in Lyon and Vienne. Both works were illustrated with figures by Fuchs, but in this last edition there were also 30 woodcuts by the botanist and physician Jacob Dalechamp. It seems that the reason that he used his initials, H.B.P., and not his full name in the work; it could be that he practically transcribed commentaries of Mattioli. | 1 | Applied and Interdisciplinary Chemistry |
Transparent wood derives its mechanical properties and performance primarily from its cellulose fiber content and the geometric orientation of the fiber tube cells (radial and tangential) structure, providing the structural base for the design of advanced materials applications.
One aspect of the transparent wood mechanical property is the strength of the material. According to Zhu and his colleagues, transparent wood in the longitudinal direction has an elastic modulus of 2.37 GPa and strength of 45.38 MPa (both which are lower than for pure PMMA) and twice as high as those perpendicular to the longitudinal direction, 1.22 GPa and 23.38 MPa respectively. They conclude that longitudinal to transverse properties decreased for transparent wood, which they expected as the presence of the polymer resin suppresses the cavity space. Also, the plastic nature of transparent wood composite provides advantages compare to other brittle materials like glass, meaning it does not shatter upon impact. | 0 | Theoretical and Fundamental Chemistry |
In the same paper in which the structure of prFMN was deduced in the active site of AnFdc1 there was a proposal for the mechanism by which Fdc1 decarboxylates α,β-unsaturated carboxylic acids. Not all UbiD enzymes decarboxylate acrylic acid substrates and other mechanisms may be at play for alternative substrates. In the case of AnFdc1 it was noted that prFMN displays an azomethine ylide characteristic C4a-N5+=C1’(Figure 1). This is a well-known 1,3-dipole in organic chemistry, positioned in the enzyme active site near to the α,β-unsaturated carboxylic acid substrate which contains a 1,3-dipolarophile. Thus, it was proposed that a 1,3-dipolar cycloaddition mechanism was responsible for the enzymatic decarboxylation. This was confirmed in a later paper.
The mechanism proposed in for 1,3-dipolar cycloaddition by Fdc1 is as follows (intermediates represented in Figure 1):
# 1,3-dipolar cycloaddition between prFMN and the α,β-unsaturated substrate leads to a pyrrolidine cycloadduct (Int1)
# This pyrrolidine cycloadduct supports simultaneous decarboxylation and ring opening, resulting in the formation of a distinct prFMN-alkene adduct (Int2)
# A conserved glutamic acid residue (E282) donates a proton to the alkene moiety, resulting a second pyrrolidine cycloadduct (Int3)
# The reaction concludes with cycloelimination of Int3 and the release of the alkene product and CO
A study went on to present evidence for the 1,3-dipolar cycloaddition, due to suspected turnover of cinnamic acid a crystal structure of AnFdc1 in complex with α-fluorocinnamic acid revealed the substrate Cα and Cβ carbons are located directly above the prFMN C1’ and C4a respectively (shown as Sub in Figure 1 - with cinnamic acid as opposed to α-fluorocinnamic acid). Cinnamic acid was confirmed to bind in a similar manner using inactive AnFdc1 crystals containing FMN. The AnFdc1 E282Q mutant crystallised with cinnamic acid revealed a structure corresponding to the Int2 species, this was taken to mean that progression through the 1,3-dipolarcycloadition cycle was halted as E282 is unable to donate a proton to the alkene moiety.
In order to observe the Int1 and Int3 structures alkyne analogues were used. Like alkenes these compounds can also act as dipolarophiles but cycloaddition would yield a cycloadduct containing a double bond. An inactive AnFdc1 enzyme (with prFMN bound) co-crystallised with the phenylpropiolic acid revealed binding in a similar manner to the α-fluorocinnamic acid AnFdc1 and cinnamic acid AnFdc1 with FMN bound (Inhib). An active AnFdc1 enzyme co-crystallised with phenylpropiolic acid revealed clear density for a 3-pyrroline cycloadduct (Int3’) between the alkyne and prFMN. Int3’ represents a structure post decarboxylation, so it was assumed that over the time it took for crystallisation (~24h) the decarboxylation had occurred. Using a rapid soaking procedure, a different cycloadduct was observed that retained the carboxyl moiety (Int1’). | 1 | Applied and Interdisciplinary Chemistry |
Exact solution is also available when the cylinder starts to slide in the axial direction with constant velocity . If we consider the cylinder axis to be in direction, then the solution is given by | 1 | Applied and Interdisciplinary Chemistry |
Triboluminescence is a phenomenon in which light is generated when a material is mechanically pulled apart, ripped, scratched, crushed, or rubbed (see tribology). The phenomenon is not fully understood but appears in most cases to be caused by the separation and reunification of static electric charges, see also triboelectric effect. The term comes from the Greek τρίβειν ("to rub"; see tribology) and the Latin lumen (light). Triboluminescence can be observed when breaking sugar crystals and peeling adhesive tapes.
Triboluminescence is often a synonym for fractoluminescence (a term mainly used when referring only to light emitted from fractured crystals). Triboluminescence differs from piezoluminescence in that a piezoluminescent material emits light when deformed, as opposed to broken. These are examples of mechanoluminescence, which is luminescence resulting from any mechanical action on a solid. | 0 | Theoretical and Fundamental Chemistry |
* Intracytoplasmic sperm injection (ICSI) is where a single sperm is injected directly into an egg. Its main usage as an expansion of IVF is to overcome male infertility problems, although it may also be used where eggs cannot easily be penetrated by sperm, and occasionally in conjunction with sperm donation. It can be used in teratozoospermia, since once the egg is fertilised abnormal sperm morphology does not appear to influence blastocyst development or blastocyst morphology.
* Additional methods of embryo profiling. For example, methods are emerging in making comprehensive analyses of up to entire genomes, transcriptomes, proteomes and metabolomes which may be used to score embryos by comparing the patterns with ones that have previously been found among embryos in successful versus unsuccessful pregnancies.
* Assisted zona hatching (AZH) can be performed shortly before the embryo is transferred to the uterus. A small opening is made in the outer layer surrounding the egg in order to help the embryo hatch out and aid in the implantation process of the growing embryo.
* In egg donation and embryo donation, the resultant embryo after fertilisation is inserted in another person than the one providing the eggs. These are resources for those with no eggs due to surgery, chemotherapy, or genetic causes; or with poor egg quality, previously unsuccessful IVF cycles or advanced maternal age. In the egg donor process, eggs are retrieved from a donors ovaries, fertilised in the laboratory with sperm, and the resulting healthy embryos are returned to the recipients uterus.
* In oocyte selection, the oocytes with optimal chances of live birth can be chosen. It can also be used as a means of preimplantation genetic screening.
* Embryo splitting can be used for twinning to increase the number of available embryos.
*Cytoplasmic transfer is where the cytoplasm from a donor egg is injected into an egg with compromised mitochondria. The resulting egg is then fertilised with sperm and introduced into a uterus, usually that of the person who provided the recipient egg and nuclear DNA. Cytoplasmic transfer was created to aid those who experience infertility due to deficient or damaged mitochondria, contained within an egg's cytoplasm. | 1 | Applied and Interdisciplinary Chemistry |
Terpenes are a key component in chemotaxonomical classification of cannabis strains as terpene composition is a phenotypic trait. Majority of terpenes found in cannabis are hydrocarbons, which are a direct product of terpene synthase (TPS) enzymes. The molecular make up of terpenes in a cannabis plant involves the linking and elongation of chains in hydrocarbons and isoprene units, formed by isopentenyl pyrophosphate and dimethylallyl pyrophosphate. Terpenoids are basically terpenes with the addition of oxygen, among other structural additions. There are numerous types of unique functional terpenes in green plants and are formed via many differing pathways; methylerythritol phosphate (MEP), cytosolic mevalonate (MEV), or deoxyxylulose phosphate pathway (DOXP) to name a few. In addition, mevalonic acids (MVA) involvement in biosynthesis of complex terpenoids, such as steroids, was demonstrated in 1983. Once produced, specifically within the disk cells, terpenes are stored within the trichomes of the plant. There are several types of terpenes in cannabis composed of varying numbers of isoprene units. They contribute to the signature aroma and insecticidal properties via their emission as volatile organic compounds. Different cannabis strains synthesize different terpenes through their biochemical pathways, and diversity of the terpenes is dependent upon the diversity of the TPS enzymes present in the cannabis plants TPS gene pool. Though, causes of variations in the TPS enzymes are still unknown.
Monoterpenes myrcene and sesquiterpenes β-caryophyllene (binds to the human CB2 cannabinoids receptor) and α-humulene are the most common terpene compounds, and are present in most varieties of cannabis strains. The lack of exact standards makes it sometimes difficult for scientists to classify new terpenes. Terpene profiles are subject to change under different environmental conditions, which may lead to variation in TPS gene expression, ultimately leading to a variation in the synthesized terpenes. Terpenes have unique, distinct aromas, which is why each strain smells different. Cannabis plants, like many others, biochemically synthesize terpenes with intense aromas as a method of chemical defense in attempts to repel predators, and invite pollinators. Because terpenes and terpenoids are biologically active molecules, it is possible variations in terpenes may elicit different biological and psychoactive responses in humans. This is why people claim to have different psychological effects to different strains. | 1 | Applied and Interdisciplinary Chemistry |
Insulated pipes (called also preinsulated pipes or bonded pipe ) are widely used for district heating and hot water supply. They consist of a steel pipe called "service pipe", a thermal insulation layer and an outer casing. The insulation bonds the service pipe and the casing together. The main purpose of such pipes is to maintain the temperature of the fluid inside the service pipes. Insulated pipes are commonly used for transport of hot water from district heating plants to district heating networks and for distribution of hot water inside district heating networks.
Thermal insulation material usually used is polyurethane foam or similar, with a thermal conductivity λ of about 0.024–0.033 W/(m·K).
While polyurethane has outstanding mechanical and thermal properties, the high toxicity of the [diisocyanates] required for its manufacturing has caused a restriction on their use. This has triggered research on alternative insulating foam fitting the application, which include polyethylene terephthalate (PET) and polybutylene (PB-1).
The outer casing is usually made of high-density polyethylene (HDPE).
Preinsulated pipes for district heating are described in European standards EN 253 and EN 15698-1. EN 253 describes "District heating pipes - Bonded single pipe systems for directly buried hot water networks - Factory made pipe assembly of steel service pipe, polyurethane thermal insulation and a casing of polyethylene". EN 15698-1 describes "District heating pipes - Bonded twin pipe systems for directly buried hot water networks - Factory made twin pipe assembly of steel service pipes, polyurethane thermal insulation and one casing of polyethylene". Both standards don't give "short names" or abbreviations for described pipes.
According to EN 253:2019 & EN 15698-1:2019, pipes must be produced to work at constant temperature of for 30 years. Thermal conductivity λ in unaged condition shall not exceed 0.029 W/(m·K). Both standards describe three insulation thickness levels. Both standards require use of polyurethane foam for thermal insulation and HDPE for casing.
Insulated pipelines are usually assembled from pipes of , , or in length, directly buried in soil in depths of commonly . | 1 | Applied and Interdisciplinary Chemistry |
Carbochemistry is the branch of chemistry that studies the transformation of coal (bituminous coal, coal tar, anthracite, lignite, graphite, and charcoal) into useful products and raw materials. The processes that are used in carbochemistry include degasification processes such as carbonization and coking, gasification processes, and liquefaction processes. | 1 | Applied and Interdisciplinary Chemistry |
Hexachlorophosphazene reacts readily with alkali metal alkoxides and amides.
The nucleophilic polysubstitution of chloride by alkoxide proceeds via displacement of chloride at separate phosphorus centers:
The observed regioselectivity is due to the combined steric effects and oxygen lone pair π-backdonation (which deactivates already substituted P atoms). | 0 | Theoretical and Fundamental Chemistry |
Unsuccessful transfer or abortive transfer is any bacterial DNA transfer from donor cells to recipient cells that fails to survive transduction and conjugation. In all cases, the transferred fragment could be diluted during the proliferation phase. Failures in the integration of the transferred DNA in the genetic material of the recipient cells may be due to:
*Failure of the incoming DNA to form a circular molecule;
*Post-circularisation, the circular molecule is wrong for maintenance, making this transfer occurs as plasmids. Genes that are located on the corresponding part of the DNA can express in the recipient cells. | 1 | Applied and Interdisciplinary Chemistry |
Carbonate esters have planar OC(OC) cores, which confers rigidity. The unique O=C bond is short (1.173 Å in the depicted example), while the C-O bonds are more ether-like (the bond distances of 1.326 Å for the example depicted).
Carbonate esters can be divided into three structural classes: acyclic, cyclic, and polymeric. The first and general case is the acyclic carbonate group. Organic substituents can be identical or not. Both aliphatic or aromatic substituents are known, they are called dialkyl or diaryl carbonates, respectively. The simplest members of these classes are dimethyl carbonate and diphenyl carbonate.
Alternatively, the carbonate groups can be linked by a 2- or 3-carbon bridge, forming cyclic compounds such as ethylene carbonate and trimethylene carbonate. The bridging compound can also have substituents, e.g. CH for propylene carbonate. Instead of terminal alkyl or aryl groups, two carbonate groups can be linked by an aliphatic or aromatic bifunctional group.
A third family of carbonates are the polymers, such as poly(propylene carbonate) and poly(bisphenol A carbonate) (e.g. Makrolon or Lexan). | 0 | Theoretical and Fundamental Chemistry |
Cannulas are typically implanted in healthy cows to research cow digestion in a university setting, to analyze the nutritional quality of feed in an agricultural setting, or to improve the microbiome of a cow with digestive disturbance in a veterinary or agricultural setting. | 1 | Applied and Interdisciplinary Chemistry |
The alloy to undergo VAR is formed into a cylinder typically by vacuum induction melting (VIM) or ladle refining (airmelt). This cylinder, referred to as an electrode is then put into a large cylindrical enclosed crucible and brought to a metallurgical vacuum (). At the bottom of the crucible is a small amount of the alloy to be remelted, which the top electrode is brought close to prior to starting the melt. Several kiloamperes of DC current are used to start an arc between the two pieces, thus a continuous melt is derived. The crucible (typically made of copper) is surrounded by a water jacket to cool the melt and control the solidification rate. To prevent arcing between the electrode and the crucible walls, the diameter of the crucible is larger than the electrode. As a result, the electrode must be lowered as the melt consumes it. Control of the current, cooling water, and electrode gap is essential to effective control of the process and production of defect-free material.
Ideally, the melt rate stays constant throughout the process cycle, but monitoring and control of the vacuum arc remelting process is not simple. This is because there is a complex heat transfer occurring involving conduction, radiation, convection within the liquid metal, and advection caused by the Lorentz force. Ensuring the consistency of the melt process in terms of pool geometry, and melt rate is crucial in ensuring the best possible properties of the alloy. | 1 | Applied and Interdisciplinary Chemistry |
The clustered regularly interspaced short palindrome repeats (CRISPR)/Cas9 system is a gene-editing technology that can introduce double-strand breaks (DSBs) at a target genomic locus. By using a single guide RNA (sgRNA), the endonuclease Cas9 can be delivered to a specific DNA sequence where it cleaves the nucleotide chain. The specificity of the sgRNA is determined by a 20-nt sequence, homologous to the genomic locus of interest, and the binding to Cas9 is mediated by a constant scaffold region of the sgRNA. The desired target site must be immediately followed (5’ to 3’) by a conserved 3 nucleotide protospacer adjacent motif (PAM). In order to repair the DSBs, the cell may use the highly error prone non-homologous end joining, or homologous recombination. By designing suitable sgRNAs, planned insertions or deletions can be introduced into the genome. In the context of genome-wide LOF screens, the aim is to cause gene disruption and knockout. | 1 | Applied and Interdisciplinary Chemistry |
Marinsky was born in Buffalo, New York on April 11, 1918. He attended the State University of New York at Buffalo, beginning at age 16 and receiving a bachelor's degree in chemistry in 1939.
During World War II he was employed as a chemist for the Manhattan Project, working for Clinton Laboratories (now Oak Ridge National Laboratory) from 1944 to 1946. In 1945, together with Lawrence E. Glendenin and Charles D. Coryell, he isolated the previously undocumented rare earth element 61 (promethium). Marinsky and Glendenin produced it both by extraction from fission products and by bombarding neodymium with neutrons. They isolated it using ion-exchange chromatography. Publication of the finding was delayed until later due to the war. Marinsky and Glendenin announced the discovery at a meeting of the American Chemical Society in September 1947. Upon the suggestion of Charles D. Coryell's wife Grace Coryell, the team named the new element for the mythical god Prometheus, who stole fire from the gods and was punished for the act by Zeus. They had also considered naming it "clintonium" for the facility where it was isolated.
Marinsky was among the Manhattan Project scientists who in 1945 signed a petition against using an atomic bomb on Japan.
He resumed his education after the war, obtaining a PhD in Nuclear and Inorganic Chemistry from the Massachusetts Institute of Technology in 1949. He worked in industrial research before joining the faculty of the State University of New York at Buffalo in 1957. His research was concerned with nuclear inorganic chemistry, physicochemical studies of ion exchange, and polyelectrolyte and electrolyte systems. During the early 1960s Marinsky was a Fulbright Research Scholar at the Weizmann Institute of Science in Israel. He worked again for SUNY at Buffalo during the late 1960s; when during that time the university required faculty to sign an oath of loyalty to the United States, Marinsky refused, terming it a violation of civil liberties; some other faculty members lost their jobs due to such a refusal. He retired in 1988, becoming a professor emeritus.
In 1990, he received the Clifford Furnas Memorial Award of the State University of New York at Buffalo, awarded to graduates whose scientific accomplishments brought prestige to the university.
Marinsky died on September 1, 2005, from multiple myeloma. He was buried in Pine Hill Cemetery in Buffalo. He was survived by his wife, the former Ruth Slick, to whom he was married for 63 years. They were the parents of four daughters. | 1 | Applied and Interdisciplinary Chemistry |
At the height of the past glaciation (about 20,000 years ago), the land was pushed down by the weight of the ice (isostatic depression). All of the ground-up rock was deposited in the surrounding ocean, which had penetrated significantly inland. The loose deposition of the silt and clay particles in the marine environment, allowed an unusual flocculation to take place. Essentially, this formed a strongly bonded soil skeleton, which was glued by highly mobile sea-salt ions.
At this point, there was only the formation of very strong marine clay, which is found all over the world and highly stable, but with its own unique geotechnical problems. When the glaciers retreated, the land mass rose (post-glacial rebound), the clay was exposed, and formed the soil mass for new vegetation. The rainwater in these northern countries was quite aggressive to these clays, perhaps because it was softer (containing less calcium), or the higher silt content allowed more rainwater and snowmelt to penetrate. The final result was that the ionic glue of the clay was weakened, to give a weak, loose soil skeleton, enclosing significant amounts of water (high sensitivity with high moisture content).
Quick clay deposits are rarely located directly at the ground surface, but are typically covered by a normal layer of topsoil. While this topsoil can absorb most normal stresses, such as normal rainfall or a modest earth tremor, a shock that exceeds the capacity of the topsoil layer — such as a larger earthquake, a large mass added near a slope, or an abnormal rainfall which leaves the topsoil fully saturated so that additional water has nowhere to permeate except into the clay — can disturb the clay and initiate the process of liquefaction. | 0 | Theoretical and Fundamental Chemistry |
Sandia National Laboratories is studying radiolysis for making superalloys. It uses nanoparticle synthesis to create alloys and superalloys. This process holds promise as a universal method of nanoparticle formation. By developing an understanding of the basic material science, it might be possible to expand research into other aspects of superalloys. Radiolysis produces polycrystalline alloys, which suffer from an unacceptable level of creep. | 1 | Applied and Interdisciplinary Chemistry |
Transfection is the process of deliberately introducing naked or purified nucleic acids into eukaryotic cells. It may also refer to other methods and cell types, although other terms are often preferred: "transformation" is typically used to describe non-viral DNA transfer in bacteria and non-animal eukaryotic cells, including plant cells. In animal cells, transfection is the preferred term as transformation is also used to refer to progression to a cancerous state (carcinogenesis) in these cells. Transduction is often used to describe virus-mediated gene transfer into eukaryotic cells.
The word transfection is a portmanteau of trans- and infection. Genetic material (such as supercoiled plasmid DNA or siRNA constructs), may be transfected. Transfection of animal cells typically involves opening transient pores or "holes" in the cell membrane to allow the uptake of material. Transfection can be carried out using calcium phosphate (i.e. tricalcium phosphate), by electroporation, by cell squeezing, or by mixing a cationic lipid with the material to produce liposomes that fuse with the cell membrane and deposit their cargo inside.
Transfection can result in unexpected morphologies and abnormalities in target cells. | 1 | Applied and Interdisciplinary Chemistry |
A boundary layer can transition to turbulence through a number of paths. Which path is realized physically depends on the initial conditions such as initial disturbance amplitude and surface roughness. The level of understanding of each phase varies greatly, from near complete understanding of primary mode growth to a near-complete lack of understanding of bypass mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
Type V restriction enzymes (e.g., the cas9-gRNA complex from CRISPRs) utilize guide RNAs to target specific non-palindromic sequences found on invading organisms. They can cut DNA of variable length, provided that a suitable guide RNA is provided. The flexibility and ease of use of these enzymes make them promising for future genetic engineering applications. | 1 | Applied and Interdisciplinary Chemistry |
Nitrogen-containing explosophores (groups I, II and III below) are particularly strong because in addition to providing oxygen they react to form molecular nitrogen, which is a very stable molecule, and thus the overall reaction is strongly exothermic. The gas formed also expands, causing the shock wave which is observed. | 0 | Theoretical and Fundamental Chemistry |
In chemistry, bond stretch isomerism is a concept of isomerism based on variations of bond length. The concept was proposed in the 1970s but was refuted in the 1990s.
The phenomenon was first invoked to explain the observation of blue and green isomers of , where is dimethylphenylphosphine. These isomers were shown, purportedly, by X-ray crystallography to differ with respect to the length of the Mo-O bond, which differed by 0.2 Å. Subsequent work showed that the supposed green bond stretch isomer consisted of blue contaminated with a small amount of yellow . The nearly isomorphous replacement of Mo-O unit with small amounts of Mo-Cl unit results in artifactually long Mo-O distance in the green sample. In essence the deception arises because the crystallographic disorder was not modeled appropriately. Several such examples were uncovered. | 0 | Theoretical and Fundamental Chemistry |
Small molecule antiandrogens that are available today have undesirable side effects caused by complete, non-selective inhibition of AR action. To minimize these side effects, a new class of tissue selective androgen receptor modulators (SARMs) has been proposed as a novel approach for the treatment of prostate cancer. These ligands should behave as antagonists in the prostate with either no activity or agonist activity in other target tissues, so as to have little or no effects in the anabolic tissues or central nervous system (CNS). However discovering this new class of ligands might be challenging because the molecular mechanism of AR action is not well understood.
Several mechanisms have been proposed to achieve this tissue selectivity of AR ligands. The most definitive evidence exists for the role of 5-alpha reductase. 5-alpha reductase is only expressed in specific tissues and could therefore be a unique contributor to tissue selectivity. Specific inhibition of the type 2 enzyme by finasteride blocks the conversion of testosterone to DHT in the prostate.
Several approaches might make use of the potential tissue-specific conversion to develop SARMs, including:
# Inactive parent compounds that are activated by type 2 5-alpha reductase in the prostate to form antiandrogens.
# AR agonists that are inactivated by type 2 5-alpha reductase in the prostate.
# AR agonists that are converted to antiandrogens only by type 2 5-alpha reductase in the prostate. | 1 | Applied and Interdisciplinary Chemistry |
Adenine nucleotide translocator (ANT), also known as the ADP/ATP translocase (ANT), ADP/ATP carrier protein (AAC) or mitochondrial ADP/ATP carrier, exchanges free ATP with free ADP across the inner mitochondrial membrane. ANT is the most abundant protein in the inner mitochondrial membrane and belongs to mitochondrial carrier family.
Free ADP is transported from the cytoplasm to the mitochondrial matrix, while ATP produced from oxidative phosphorylation is transported from the mitochondrial matrix to the cytoplasm, thus providing the cells with its main energy currency. ADP/ATP translocases are exclusive to eukaryotes and are thought to have evolved during eukaryogenesis. Human cells express four ADP/ATP translocases: SLC25A4, SLC25A5, SLC25A6 and SLC25A31, which constitute more than 10% of the protein in the inner mitochondrial membrane. These proteins are classified under the mitochondrial carrier superfamily. | 1 | Applied and Interdisciplinary Chemistry |
Adsorption constants are equilibrium constants, therefore they obey the Van 't Hoff equation:
As can be seen in the formula, the variation of K must be isosteric, that is, at constant coverage.
If we start from the BET isotherm and assume that the entropy change is the same for liquefaction and adsorption, we obtain
that is to say, adsorption is more exothermic than liquefaction. | 0 | Theoretical and Fundamental Chemistry |
In several large American cities, homeless people live in storm drains. At least 300 people live in the 200 miles of underground storm drains of Las Vegas, many of them making a living finding unclaimed winnings in the gambling machines. An organization called Shine a Light was founded in 2009 to help the drain residents after over 20 drowning deaths occurred in the preceding years. A man in San Diego was evicted from a storm drain after living there for nine months in 1986. | 1 | Applied and Interdisciplinary Chemistry |
Figure 2 illustrates the most common type of DDRNAI DNA construct, designed to express a shRNA. This figure consists of a promoter sequence driving the expression of sense and antisense sequences separated by a loop sequence, followed by a transcriptional terminator. The antisense sequence processed from the shRNA can bind to the target RNA and specify its degradation. shRNA constructs typically encode sense and antisense sequences of 20–30 nucleotides. Flexibility in construct design is possible; for example, the positions of sense and antisense sequences can be reversed, and other modifications and additions can alter intracellular shRNA processing. Moreover, a variety of promoter loop and terminator sequences can be used.
A beneficial variant is a multi-cassette (Figure 2b). Designed to express two or more shRNAs, they can simultaneously target multiple sequences for degradation hence particularly a useful strategy for targeting viruses. Natural sequence variations can render a single shRNA-target site unrecognizable, preventing RNA degradation. Multi-cassette constructs that target multiple sites within the same viral RNA circumvent this issue. | 1 | Applied and Interdisciplinary Chemistry |
Phenylalanine and tyrosine are the precursors used in the phenylpropanoids biosynthesis. The phenylpropanoids are then used to produce the flavonoids, coumarins, tannins and lignin. The first enzyme involved is phenylalanine ammonia-lyase (PAL) that converts -phenylalanine to trans-cinnamic acid and ammonia. | 1 | Applied and Interdisciplinary Chemistry |
Markovnikovs rule addition of the cobalt hydride to primary alkenes is disfavored by steric hindrance between the cobalt centre and the secondary alkyl ligand. Bulky ligands exacerbate this steric hindrance. Hence, the mixed carbonyl/phosphine complexes offer a greater selectivity for anti-Markovnikov addition, thus favoring straight chain products (n'-) aldehydes. Modern catalysts rely increasingly on chelating ligands, especially diphosphites. | 0 | Theoretical and Fundamental Chemistry |
Flux in geochemical cycles is the movement of material between the deep Earth and the surface reservoirs. This occurs through two different processes: volcanism and subduction of tectonic plates.
Subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate and sinks into the mantle as the plates converge. This leads to the sinking of one plate into the mantle which creates a broad range of geochemical transformations or cycling.
Volcanism is the process that takes place at divergent boundaries by which one tectonic plate separates from another creating a rift in which molten rock (magma) erupts onto the surface of the Earth. This molten rock magma then cools and crystallizes, forming igneous rocks. If crystallization occurs at the Earths surface, extrusive igneous rocks are formed; if crystallization occurs within the Earths lithosphere, intrusive igneous rocks are formed which can then be brought to Earth's surface by denudation | 0 | Theoretical and Fundamental Chemistry |
In 1978, Walter Gilbert published "Why Genes in Pieces" which first began to explore the idea that the gene is a mosaic—that each full nucleic acid strand is not coded continuously but is interrupted by "silent" non-coding regions. This was the first indication that there needed to be a distinction between the parts of the genome that code for protein, now called coding regions, and those that do not. | 1 | Applied and Interdisciplinary Chemistry |
The interfacing mechanism is contained inside a common EI source, like that found in any GC-MS system. The liquid phase from a nano HPLC column is admitted from the capillary column port, where the connection tubing and the nebulizer are first introduced and sealed to prevent vacuum loss. The mechanism is based on the formation of an aerosol in high-vacuum conditions, followed by a quick droplet desolvation and final vaporization of the solute prior to the ionization. The completion of the process is quick and complete and reduces chances of thermal decomposition as reported in the Figure, where a scheme of the interface is shown. The core of the interface is represented by the micro-nebulizer. The nebulizer tip protrudes into the ion source so that the spray expansion is completely contained inside the ion volume. The eluate emerges as liquid phase at a flow rate of 300-500 nL/min, and any premature in-tube solvent evaporation is prevented by a convenient thermal insulation of the nebulizer and the connecting tubing from the surrounding source heat. The high temperature of the ion source, between 300 and 400°C, has a double function: to compensate for the latent heat of vaporization during the droplet desolvation, and to convert the solute into the gas phase. If all components of this simple interface are correctly placed and sized, then each substance separated by the nano-column is smoothly converted into the gas phase, the peak profile is nicely reproduced, and high quality mass spectra are generated. Major advantages of this technical solution are the following: 1) It delivers high-quality, fully library matchable mass spectra of most sub-1 kDa molecules amenable by HPLC, 2) It is a chemical ionization free interface (unless operated intentionally) with accurate reproduction of the expected isotope ion abundances, 3) Response is never influenced by matrix components in the sample or in the mobile phase, 4) It can be considered a universal detector for small molecules because response is not related to compound polarity. | 0 | Theoretical and Fundamental Chemistry |
Thomson scattering is a model for the effect of electromagnetic fields on electrons when the field energy is much less than the rest mass of the electron . In the model the electric field of the incident wave accelerates the charged particle, causing it, in turn, to emit radiation at the same frequency as the incident wave, and thus the wave is scattered. Thomson scattering is an important phenomenon in plasma physics and was first explained by the physicist J. J. Thomson. As long as the motion of the particle is non-relativistic (i.e. its speed is much less than the speed of light), the main cause of the acceleration of the particle will be due to the electric field component of the incident wave. In a first approximation, the influence of the magnetic field can be neglected. The particle will move in the direction of the oscillating electric field, resulting in electromagnetic dipole radiation. The moving particle radiates most strongly in a direction perpendicular to its acceleration and that radiation will be polarized along the direction of its motion. Therefore, depending on where an observer is located, the light scattered from a small volume element may appear to be more or less polarized.
The electric fields of the incoming and observed wave (i.e. the outgoing wave) can be divided up into those components lying in the plane of observation (formed by the incoming and observed waves) and those components perpendicular to that plane. Those components lying in the plane are referred to as "radial" and those perpendicular to the plane are "tangential". (It is difficult to make these terms seem natural, but it is standard terminology.)
The diagram on the right depicts the plane of observation. It shows the radial component of the incident electric field, which causes the charged particles at the scattering point to exhibit a radial component of acceleration (i.e., a component tangent to the plane of observation). It can be shown that the amplitude of the observed wave will be proportional to the cosine of χ, the angle between the incident and observed waves. The intensity, which is the square of the amplitude, will then be diminished by a factor of cos(χ). It can be seen that the tangential components (perpendicular to the plane of the diagram) will not be affected in this way.
The scattering is best described by an emission coefficient which is defined as ε where ε dt dV dΩ dλ is the energy scattered by a volume element in time dt into solid angle dΩ between wavelengths λ and λ+dλ. From the point of view of an observer, there are two emission coefficients, ε corresponding to radially polarized light and ε corresponding to tangentially polarized light. For unpolarized incident light, these are given by:
where is the density of charged particles at the scattering point, is incident flux (i.e. energy/time/area/wavelength), is the angle between the incident and scattered photons (see figure above) and is the Thomson cross section for the charged particle, defined below. The total energy radiated by a volume element in time dt between wavelengths λ and λ+dλ is found by integrating the sum of the emission coefficients over all directions (solid angle):
The Thomson differential cross section, related to the sum of the emissivity coefficients, is given by
expressed in SI units; q is the charge per particle, m the mass of particle, and a constant, the permittivity of free space. (To obtain an expression in cgs units, drop the factor of 4ε.) Integrating over the solid angle, we obtain the Thomson cross section
in SI units.
The important feature is that the cross section is independent of light frequency. The cross section is proportional by a simple numerical factor to the square of the classical radius of a point particle of mass m and charge q, namely
Alternatively, this can be expressed in terms of , the Compton wavelength, and the fine structure constant:
For an electron, the Thomson cross-section is numerically given by: | 0 | Theoretical and Fundamental Chemistry |
Wetland chemistry is largely affected by dredging, which can be done for a variety of purposes. Wetlands are areas within floodplains with both terrestrial and aquatic characteristics, including marshes, swamps, bogs, and others. It has been estimated that they occupy around 2.8x10 km, about 2.2% of the Earth’s surface, but other estimates are even higher. It has also been estimated to have a worth of $14.9 trillion and are responsible for 75% of commercial and 90% of recreational harvest of fish and shellfish in the United States. Wetlands also hold an important role in water purification, storm protection, industry, travel, research, education, and tourism. Being heavily used and traveled through, dredging is common and leads to continuation of long-term damage of the ecosystem and land loss, and ultimately a loss in industry, homes, and protection.
Wetlands undergo different chemical reactions depending on a variety of parameters, including salinity and pH. Redox reactions have a major effect on wetland ecosystems, as they depend heavily on salinity, pH, oxygen availability, and others. Common redox reactions in wetland include carbon, nitrogen, and sulfur transformations. Fluctuations in water flow and flooding can change the abundance of the oxidized or reduced species depending on the environment. Increased flooding and water flow can also change the availability of nutrients to local species. The further the wetlands change from their original states, the more difficult rebuilding land becomes. The types of mitigation efforts also change depending on the chemistry, so an understanding of the change is required for effective mitigation. | 0 | Theoretical and Fundamental Chemistry |
In a common FPLC strategy, a resin is chosen that the protein of interest will bind to by a charge interaction while in buffer A (the running buffer) but become dissociated and return to solution in buffer B (the elution buffer). A mixture containing one or more proteins of interest is dissolved in 100% buffer A and pumped into the column. The proteins of interest bind to the resin while other components are carried out in the buffer. The total flow rate of the buffer is kept constant; however, the proportion of buffer B (the "elution" buffer) is gradually increased from 0% to 100% according to a programmed change in concentration (the "gradient"). At some point during this process each of the bound proteins dissociates and appears in the eluant. The eluant passes through two detectors which measure salt concentration (by conductivity) and protein concentration (by absorption of ultraviolet light at a wavelength of 280 nm). As each protein is eluted, it appears in the eluant as a "peak" in protein concentration, and can be collected for further use. | 0 | Theoretical and Fundamental Chemistry |
Using non-linear least squares minimization, the following system is solved:
where is the calculated intensity and is the observed intensity of a point in the powder pattern, , is a scale factor, and is the number of measured data points. The minimized function is given by:
where is the weight, and from the previous equation is unity (since is usually absorbed in the phase scale factor). The summation extends to all data points. Considering the peak shape functions and accounting for the overlapping of Bragg peaks because of the one-dimensionality of XRD data, the expanded form of the above equation for the case of a single phase measured with a single wavelength becomes:
where:
* is the background at the data point.
* is the phase scale factor.
* is the number of Bragg reflections contributing to the intensity of the reflection.
* is the integrated intensity of the Bragg peak.
* is the peak shape function.
For a material that contains several phases (), the contribution from each is accounted for by modifying the above equation as follows:
It can easily be seen from the above equations that experimentally minimizing the background, which holds no useful structural information, is paramount for a successful profile fitting. For a low background, the functions are defined by contributions from the integrated intensities and peak shape parameters. But with a high background, the function being minimized depends on the adequacy of the background and not integrated intensities or peak shapes. Thus, a structure refinement cannot adequately yield structural information in the presence of a large background.
It is also worth noting the increased complexity brought forth by the presence of multiple phases. Each additional phase adds to the fitting, more Bragg peaks, and another scale factor tied to corresponding structural parameters, and peak shape. Mathematically they are easily accounted for, but practically, due to the finite accuracy and limited resolution of experimental data, each new phase can lower the quality and stability of the refinement. It is advantageous to use single phase materials when interested in finding precise structural parameters of a material. However, since the scale factors of each phase are determined independently, Rietveld refinement of multi phase materials can quantitatively examine the mixing ratio of each phase in the material. | 0 | Theoretical and Fundamental Chemistry |
* Metallic sleeves are heatsinks in the firestop that follows the mounting of the penetrants. Maximum and minimum tolerances for wall thicknesses must be taken into account prior to casting. Heatsinks can affect T-ratings. Organic sealants used for topcaulking in firestops may let go of the sleeve if it has conducted too much heat through to the unexposed side (as in the case of the fire test article, ).
*Plastic sleeves are usually removed after the concrete forms are stripped, as they contribute fuel to an accidental fire. | 1 | Applied and Interdisciplinary Chemistry |
The best-studied example of cap-independent translation initiation in eukaryotes uses the internal ribosome entry site (IRES). Unlike cap-dependent translation, cap-independent translation does not require a 5 cap to initiate scanning from the 5 end of the mRNA until the start codon. The ribosome can localize to the start site by direct binding, initiation factors, and/or ITAFs (IRES trans-acting factors) bypassing the need to scan the entire 5' UTR. This method of translation is important in conditions that require the translation of specific mRNAs during cellular stress, when overall translation is reduced. Examples include factors responding to apoptosis and stress-induced responses. | 1 | Applied and Interdisciplinary Chemistry |
The word fugacity is derived from the Latin fugere, to flee. In the sense of an "escaping tendency", it was introduced to thermodynamics in 1901 by the American chemist Gilbert N. Lewis and popularized in an influential textbook by Lewis and Merle Randall, Thermodynamics and the Free Energy of Chemical Substances, in 1923. The "escaping tendency" referred to the flow of matter between phases and played a similar role to that of temperature in heat flow. | 0 | Theoretical and Fundamental Chemistry |
Process analysis initially involved sampling the variety of process streams or webs and transporting samples to quality control or central analytical service laboratories. Time delays for analytical results due to sample transport and analytical preparation steps negated the value of many chemical analyses for purposes other than product release. Over time it was understood that real-time measurements provided timely information about a process, which was far more useful for high efficiency and quality. The development of real-time process analysis has provided information for process optimization during any manufacturing process. The journal Analytical Chemistry (journal) publishes a biennial review of the most recent developments in the field.
The first real-time measurements in a production environment were made with modified laboratory instrumentation; in recent times specialized process and handheld instrumentation has been developed for immediate analysis. | 0 | Theoretical and Fundamental Chemistry |
Fluoride salts are commonly used in biological assay processing to inhibit the activity of phosphatases, such as serine/threonine phosphatases. Fluoride mimics the nucleophilic hydroxide ion in these enzymes' active sites. Beryllium fluoride and aluminium fluoride are also used as phosphatase inhibitors, since these compounds are structural mimics of the phosphate group and can act as analogues of the transition state of the reaction. | 1 | Applied and Interdisciplinary Chemistry |
Oral exemestane 25 mg/day for 2–3 years of adjuvant therapy was generally more effective than 5 years of continuous adjuvant tamoxifen in the treatment of postmenopausal women with early-stage estrogen receptor-positive/unknown receptor status breast in a large well-designed trial. Preliminary data from the open-label TEAM trial comparing exemestane with tamoxifen indicated in 2009 that exemestane 25 mg/day is also effective in the primary adjuvant treatment of early-stage breast cancer in postmenopausal women.
Interim phase III trial results in 2011 showed that adding everolimus to exemestane therapy against advanced breast cancer can significantly improve progression-free survival compared with exemestane therapy alone.
A Phase III trial was reported in 2011, concluding that the use of exemestane in postmenopausal women at an increased risk for breast cancer reduced the incidence of invasive breast cancer. In 4,560 women, after 35 months, the administration of exemestane at a dose of 25 mg/day resulted in a 65% reduction in the risk of breast cancer compared with placebo; annual incidence rates were 0.19% and 0.55%, respectively (hazard ratio: 0.35; 95% CI [0.18-0.70]; p = 0.002). | 0 | Theoretical and Fundamental Chemistry |
α,β-unsaturated carbonyl compounds undergo hydrocyanation in the absence of metal catalysts. One manifestation is a special case of the Michael reaction, leading to β-cyanoketones. Another manifestation leads to vinyl cyanohydrins. β-cyano-cyanohydrins are also observed. Reaction conditions allows access to any of these products.
Generally acidic conditions favor 1,2-adducts, while basic conditions favor 1,4-adducts. Additions of alkali metal cyanides, for instance, lead exclusively to 1,4-addition. In contrast to alkali metal cyanides and cyanoaluminates, Lewis acidic cyanides, such as TMSCN, favor 1,2-addition. Acetylenic substrates undergo the reaction; however the scope of this reaction is limited and yields are often low.
1,4-Addition to imines has been observed in a few cases, although imines are often base labile.
Esters, nitriles and other carbonyl derivatives also undergo conjugative hydrocyanation.
When alkali metal cyanides are used, at least partial neutralization of the reaction medium is usually necessary. Neutralization can be accomplished through an acidic group on the substate itself (internal neutralization). or through the addition of an external acid (external neutralization). Acetic acid is commonly used for this purpose, in a procedure pioneered by Lapworth.
Conjugative hydrocyanation was used to prepare the steroidal D ring. Diastereoselectivity is generally high in these addition reactions, and the resulting β-cyano carbonyl compounds can be converted to a number of steroidal products. | 0 | Theoretical and Fundamental Chemistry |
Alkali metal alkoxides are often oligomeric or polymeric compounds, especially when the R group is small (Me, Et). The alkoxide anion is a good bridging ligand, thus many alkoxides feature or linkages. In solution, the alkali metal derivatives exhibit strong ion-pairing, as expected for the alkali metal derivative of a strongly basic anion. | 0 | Theoretical and Fundamental Chemistry |
The myelin sheath of long nerves was discovered and named by German pathological anatomist Rudolf Virchow in 1854. French pathologist and anatomist Louis-Antoine Ranvier later discovered the nodes, or gaps, in the myelin sheath that now bear his name. Born in Lyon, Ranvier was one of the most prominent histologists of the late 19th century. Ranvier abandoned pathological studies in 1867 and became an assistant of physiologist Claude Bernard. He was the chairman of General Anatomy at the Collège de France in 1875.
His refined histological techniques and his work on both injured and normal nerve fibers became world-renowned. His observations on fiber nodes and the degeneration and regeneration of cut fibers had a great influence on Parisian neurology at the Salpêtrière. Soon afterwards, he discovered gaps in sheaths of nerve fibers, which were later called the Nodes of Ranvier. This discovery later led Ranvier to careful histological examination of myelin sheaths and Schwann cells. | 1 | Applied and Interdisciplinary Chemistry |
Thermal equilibrium of a body in itself refers to the body when it is isolated. The background is that no heat enters or leaves it, and that it is allowed unlimited time to settle under its own intrinsic characteristics. When it is completely settled, so that macroscopic change is no longer detectable, it is in its own thermal equilibrium. It is not implied that it is necessarily in other kinds of internal equilibrium. For example, it is possible that a body might reach internal thermal equilibrium but not be in internal chemical equilibrium; glass is an example.
One may imagine an isolated system, initially not in its own state of internal thermal equilibrium. It could be subjected to a fictive thermodynamic operation of partition into two subsystems separated by nothing, no wall. One could then consider the possibility of transfers of energy as heat between the two subsystems. A long time after the fictive partition operation, the two subsystems will reach a practically stationary state, and so be in the relation of thermal equilibrium with each other. Such an adventure could be conducted in indefinitely many ways, with different fictive partitions. All of them will result in subsystems that could be shown to be in thermal equilibrium with each other, testing subsystems from different partitions. For this reason, an isolated system, initially not its own state of internal thermal equilibrium, but left for a long time, practically always will reach a final state which may be regarded as one of internal thermal equilibrium. Such a final state is one of spatial uniformity or homogeneity of temperature. The existence of such states is a basic postulate of classical thermodynamics. This postulate is sometimes, but not often, called the minus first law of thermodynamics. A notable exception exists for isolated quantum systems which are many-body localized and which never reach internal thermal equilibrium. | 0 | Theoretical and Fundamental Chemistry |
Brownfield is land that is abandoned or underutilized due to pollution from industrial use. The specific definition of brownfield land varies and is decided by policy makers and/or land developers within different countries. The main difference in definitions of whether a piece of land is considered a brownfield or not depends on the presence or absence of pollution. Overall, brownfield land is a site previously developed for industrial or commercial purposes and thus requires further development before reuse.
Examples of post industrial brownfield sites include abandoned factories, dry cleaning establishments, and gas stations. Typical contaminants include hydrocarbon spillages, solvents and pesticides, asbestos, and heavy metals like lead.
Many contaminated post-industrial brownfield sites sit unused because the cleaning costs may be more than the land is worth after redevelopment. Previously unknown underground wastes can increase the cost for study and clean-up. Depending on the contaminants and damage present adaptive re-use and disposal of a brownfield can require advanced and specialized appraisal analysis techniques. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogels have the remarkable ability to swell in water and aqueous solvents. During the process of swelling, surface instability can occur. This instability depends on the thickness of the hydrogel layers and the surface tension. A higher surface tension stabilizes the flat surface of the hydrogel, which is the outer-most layer. The swelling ratio of the flat layer can be calculated using the following equation derived from the Flory–Huggins theory of free surface energy in hydrogels:
Where λ is the swelling ratio, μ is the chemical potential, p is pressure, k is the Boltzmann constant, and χ and N are unitless hydrogel constants.
As swelling increases, mechanical properties generally suffer. | 0 | Theoretical and Fundamental Chemistry |
Rate constant can be calculated for elementary reactions by molecular dynamics simulations.
One possible approach is to calculate the mean residence time of the molecule in the reactant state. Although this is feasible for small systems with short residence times, this approach is not widely applicable as reactions are often rare events on molecular scale.
One simple approach to overcome this problem is Divided Saddle Theory. Such other methods as the Bennett Chandler procedure, and Milestoning have also been developed for rate constant calculations. | 0 | Theoretical and Fundamental Chemistry |
Pakistan Engineering Council headquarters are located at Ataturk Avenue (East) in the G-5/2 sector of Islamabad. President Muhammad Zia-ul-Haq laid the foundation stone of the building on 28 July 1987. The building became functional on 14 October 1992 after Prime Minister Nawaz Sharif inaugurated it. | 1 | Applied and Interdisciplinary Chemistry |
An isometry of the Euclidean plane is a distance-preserving transformation of the plane. That is, it is a map
such that for any points p and q in the plane,
where d(p, q) is the usual Euclidean distance between p and q. | 0 | Theoretical and Fundamental Chemistry |
A microprobe is an instrument that applies a stable and well-focused beam of charged particles (electrons or ions) to a sample. | 0 | Theoretical and Fundamental Chemistry |
Manganese is also important in photosynthetic oxygen evolution in chloroplasts in plants. The oxygen-evolving complex (OEC) is a part of photosystem II contained in the thylakoid membranes of chloroplasts; it is responsible for the terminal photooxidation of water during the light reactions of photosynthesis, and has a metalloenzyme core containing four atoms of manganese. To fulfill this requirement, most broad-spectrum plant fertilizers contain manganese. | 1 | Applied and Interdisciplinary Chemistry |
Free molecular flow describes the fluid dynamics of gas where the mean free path of the molecules is larger than the size of the chamber or of the object under test. For tubes/objects of the size of several cm, this means pressures well below 10 mbar. This is also called the regime of high vacuum, or even ultra-high vacuum. This is opposed to viscous flow encountered at higher pressures. The presence of free molecular flow can be calculated, at least in estimation, with the Knudsen number (Kn). If Kn > 10, the system is in free molecular flow, also known as Knudsen flow.
In free molecular flow, the pressure of the remaining gas can be considered as effectively zero. Thus, boiling points do not depend on the residual pressure. The flow can be considered to be individual particles moving in straight lines. Practically, the "vapor" cannot move around bends or into other spaces behind obstacles, as they simply hit the tube wall. This implies conventional pumps cannot be used, as they rely on viscous flow and fluid pressure. Instead, special sorption pumps, ion pumps and momentum transfer pumps i.e. turbomolecular pumps are used.
Free molecular flow occurs in various processes such as molecular distillation, ultra-high vacuum equipment such as particle accelerators, and naturally in outer space.
The definition of a free molecular flow depends on the distance scale under consideration. For example, in the interplanetary medium, the plasma is in a free molecular flow regime in scales less than 1 AU; thus, planets and moons are effectively under particle bombardment. However, on larger scales, fluid-like behavior is observed, because the probability of collisions between particles becomes significant. | 1 | Applied and Interdisciplinary Chemistry |
Silver nitrate is a salt of silver that is sometimes used by dentists as a caustic material to cauterize mouth sores, and has in the past been used by physicians for treating wounds. It may be an appropriate material to salt the earth after burying a monster that has been killed with silver bullets. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.