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Observations of rocks on the plains show they contain the minerals pyroxene, olivine, plagioclase, and magnetite. These rocks can be classified in different ways. The amounts and types of minerals make the rocks primitive basalts—also called picritic basalts. The rocks are similar to ancient terrestrial rocks called basaltic komatiites. Rocks of the plains also resemble the basaltic shergottites, meteorites which came from Mars. One classification system compares the amount of alkali elements to the amount of silica on a graph; in this system, Gusev plains rocks lie near the junction of basalt, picrobasalt, and tephrite. The Irvine-Barager classification calls them basalts.
Plain's rocks have been very slightly altered, probably by thin films of water because they are softer and contain veins of light colored material that may be bromine compounds, as well as coatings or rinds. It is thought that small amounts of water may have gotten into cracks inducing mineralization processes).
Coatings on the rocks may have occurred when rocks were buried and interacted with thin films of water and dust.
One sign that they were altered was that it was easier to grind these rocks compared to the same types of rocks found on Earth.
The first rock that Spirit studied was Adirondack. It turned out to be typical of the other rocks on the plains. | 0 | Theoretical and Fundamental Chemistry |
Richmond, located in the San Francisco Bay Area, is an evolving, multi-cultural community that has transformed itself from an over-polluted industrial town to a pioneer in an environmental justice movement. The city has been host to numerous oil refineries, including the Chevron Corporation refinery, which opened in 1901 under the ownership of Pacific Coast Oil. The Chevron Refinery is a leading source of air quality violations in the state of California. Richmond residents are also exposed to pollution from the Santa Fe train line and the presence of heavy traffic and diesel trucks along the Richmond Parkway. However, residents are most concerned with air pollution health impacts from the Chevron Refinery. In 1999, Richmond measure significantly higher on Air Quality Indices (AQI) (an indicator of how polluted is air is) compared to national level. Air pollution emission from the Chevron refinery includes benzene, ethylbenzene, toluene, xylene, nitrous dioxide, and sulfur dioxide, which are known to cause elevated cancer risks and respiratory illness. Rates of child and adult asthma are especially elevated among Richmond residents.
Richmond residents have struggled to improve local air quality. The city has a significant non-white, low-income population. According to 2010 U.S. Census, of Richmond's 103,701 person populations, “one in six residents lives below the federal poverty level, and more than eight in 10 are people of color. In North Richmond, next to one of the nation’s largest refineries, 97 percent of residents are non-white and nearly one in four live in poverty”. Low-income communities have differential access to political power, and their collective political voice is often less able to contest decisions impacting industrial operations. The combination of poverty, poor access to clean air, and poor political power can result in inequality in which communities of color bear a disproportionate burden of pollution and, therefore, suffer from greater environmental health risks.
Because Richmond is an air pollution hotspot, Richmond residents have applied different strategies since the 1980s to try to improve local air quality. The first EJ movement in the area started in the late 1980s, when the activist tried to stop construction of a garbage incinerator near North Richmond. Sixteen years later, local citizen utilizes “Bucket Brigades” to document a handful of criteria air pollutants such as sulfur dioxide (SO), carbon monoxide (CO), nitrogen dioxide (NO), and ozone (O).This study involves citizens to actively collecting the samples of emissions from Chevron's refineries, especially during accidents, fires, leaks, and explosions. The “sniffers” alert the “samplers” to collect the air samples when they notice a problem. The “samplers” then contact the Coordinator to check the bucket and perform the paperwork before submitting the samples to the Laboratory, in which the results will be reported to CBE, an environmental justice organization. The “Bucket Brigades” did not only raise the awareness local citizens to fight against the air pollution in their area but also their participation.
As the number of activists and participants grew in numbers, their position in the battle against environmental injustice was further fortified with the election Green-party mayor of Richmond, Gayle McLaughlin, as well as three new council members sympathetic to their cause in 2008. In July 2008, despite the council failing to halt the Chevron's plan to build more refineries in the area due to rising gasoline prices during that time, the council succeeded to acquire $61 million from the oil company for community programs.
Due to great forces from the local communities and fellow EJ activists in Richmond area, Chevron has been making progress to embrace cleaner environment. In 2005, local activists managed to convince Bay Area Air Quality Management District to tighten the air pollution regulations by increasing the frequency of fines of facility incidents. Since then, Chevron has been flaring 10 times less than before. On top of that, Chevron has invested $150 million for building gas turbine in order to reduce air emission, increase energy efficiency, as well as provide most electrical and steam power Chevron requires to operate. | 1 | Applied and Interdisciplinary Chemistry |
DNA supercoiling is important for DNA packaging within all cells. Because the length of DNA can be thousands of times that of a cell, packaging this genetic material into the cell or nucleus (in eukaryotes) is a difficult feat. Supercoiling of DNA reduces the space and allows for DNA to be packaged. In prokaryotes, plectonemic supercoils are predominant, because of the circular chromosome and relatively small amount of genetic material. In eukaryotes, DNA supercoiling exists on many levels of both plectonemic and solenoidal supercoils, with the solenoidal supercoiling proving most effective in compacting the DNA. Solenoidal supercoiling is achieved with histones to form a 10 nm fiber. This fiber is further coiled into a 30 nm fiber, and further coiled upon itself numerous times more.
DNA packaging is greatly increased during mitosis when duplicated sister DNAs are segregated into daughter cells. It has been shown that condensin, a large protein complex that plays a central role in mitotic chromosome assembly, induces positive supercoils in an ATP hydrolysis-dependent manner in vitro. Supercoiling could also play an important role during interphase in the formation and maintenance of topologically associating domains (TADs).
Supercoiling is also required for DNA/RNA synthesis. Because DNA must be unwound for DNA/RNA polymerase action, supercoils will result. The region ahead of the polymerase complex will be unwound; this stress is compensated with positive supercoils ahead of the complex. Behind the complex, DNA is rewound and there will be compensatory negative supercoils. Topoisomerases such as DNA gyrase (Type II Topoisomerase) play a role in relieving some of the stress during DNA/RNA synthesis. | 1 | Applied and Interdisciplinary Chemistry |
SNPs can be easily assayed due to only containing two possible alleles and three possible genotypes involving the two alleles: homozygous A, homozygous B and heterozygous AB, leading to many possible techniques for analysis. Some include: DNA sequencing; capillary electrophoresis; mass spectrometry; single-strand conformation polymorphism (SSCP); single base extension; electrochemical analysis; denaturating HPLC and gel electrophoresis; restriction fragment length polymorphism; and hybridization analysis. | 1 | Applied and Interdisciplinary Chemistry |
Boyle, Charles and Gay-Lussac laws, together with Avogadro's law, were combined by Émile Clapeyron in 1834, giving rise to the ideal gas law. At the end of the 19th century, later developments from scientists like August Krönig, Rudolf Clausius, James Clerk Maxwell and Ludwig Boltzmann, gave rise to the kinetic theory of gases, a microscopic theory from which the ideal gas law can be derived as an statistical result from the movement of atoms/molecules in a gas. | 0 | Theoretical and Fundamental Chemistry |
In 2004, D.R. Halpin and P.B. Harbury presented a novel intriguing method for the construction of DNA-encoded libraries. For the first time the DNA-conjugated templates served for both encoding and programming the infrastructure of the “split-&-pool” synthesis of the library components. The design of Halpin and Harbury enabled alternating rounds of selection, PCR amplification and diversification with small organic molecules, in complete analogy to phage display technology. The DNA-routing machinery consists of a series of connected columns bearing resin-bound anticodons, which could sequence-specifically separate a population of DNA-templates into spatially distinct locations by hybridization. According to this split-and-pool protocol a peptide combinatorial library DNA-encoded of 10 members was generated. | 1 | Applied and Interdisciplinary Chemistry |
Intramolecular cyclopropanation of a diazoketone is applied in a racemic synthesis of sirenin. A single cyclopropane diastereomer was isolated in 55% yield after diazoketone formation and cyclization. | 0 | Theoretical and Fundamental Chemistry |
Carboxylic acids are commonly identified by their trivial names. They often have the suffix -ic acid. IUPAC-recommended names also exist; in this system, carboxylic acids have an -oic acid suffix. For example, butyric acid () is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another parent structure, such as 2-carboxyfuran.
The carboxylate anion ( or ) of a carboxylic acid is usually named with the suffix -ate, in keeping with the general pattern of -ic acid and -ate for a conjugate acid and its conjugate base, respectively. For example, the conjugate base of acetic acid is acetate.
Carbonic acid, which occurs in bicarbonate buffer systems in nature, is not generally classed as one of the carboxylic acids, despite that it has a moiety that looks like a COOH group. | 0 | Theoretical and Fundamental Chemistry |
Kai Simons (born 24 May 1938) is a Finnish professor of biochemistry and cell biology and physician living and working in Germany. He introduced the concept of lipid rafts, as well as coined the term trans-Golgi network and proposed its role in protein and lipid sorting. The co-founder and co-organizer of EMBO, ELSO, Simons initiated the foundation of MPI-CBG, where he acted as a director (1998–2006) and a group-leader (until 2012). He is the co-founder and co-owner of Lipotype GmbH. | 1 | Applied and Interdisciplinary Chemistry |
Other lake constituents can influence lake metabolic rates including CO concentration, pH, salinity, and silica, among others. CO can be a limiting (or co-limiting along with other nutrients) resource for primary productivity and can promote more intense phytoplankton blooms. Some algal species, such as chrysophytes, may not have carbon-concentrating mechanisms or the ability to use bicarbonate as a source of inorganic carbon for photosynthesis, thus, elevated levels of CO may increase their rates of photosynthesis. During algal blooms, elevated dissolved CO ensures that CO is not a limiting resource for growth since rapid increases in production deplete CO and raise pH. Changes in pH at short time scales (e.g. sub-daily) from spikes in primary productivity may cause short-term reductions in bacterial growth and respiration, but at longer timescales, bacterial communities can adapt to elevated pH.
Salinity can also cause changes in metabolic rates of lakes through salinity impacts on individual metabolic rates and community composition. Lake metabolic rates can be correlated both positively or negatively with salinity due to interactions of salinity with other drivers of ecosystem metabolism, such as flushing rates or droughts. For example, Moreira-Turcq (2000) found that excess precipitation over evaporation caused reduced salinity in a coastal lagoon, increased nutrient loading, and increased pelagic primary productivity. The positive relationship between primary productivity and salinity might be an indicator of changes in nutrient availability due to increased inflows. However, salinity increases from road salts can cause toxicity in some lake organisms, and extreme cases of salinity increases can restrict lake mixing which could change distribution of metabolism rates throughout the lake water column. | 1 | Applied and Interdisciplinary Chemistry |
The requirement for a good leaving group is relaxed in conjugate base elimination reactions. These reactions include loss of a leaving group in the β position of an enolate as well as the regeneration of a carbonyl group from the tetrahedral intermediate in nucleophilic acyl substitution. Under forcing conditions, even amides can be made to undergo basic hydrolysis, a process that involves the expulsion of an extremely poor leaving group, RN. Even more dramatic, decarboxylation of benzoate anions can occur by heating with copper or CuO, involving the loss of an aryl anion. This reaction is facilitated by the fact that the leaving group is most likely an arylcopper compound rather than the much more basic alkali metal salt.
This dramatic departure from normal leaving group requirements occurs mostly in the realm of C=O double bond formation where formation of the very strong C=O double bond can drive otherwise unfavorable reactions forward. The requirement for a good leaving group is still relaxed in the case of C=C bond formation via E1cB mechanisms, but because of the relative weakness of the C=C double bond, the reaction still exhibits some leaving group sensitivity. Notably, changing the leaving groups identity (and willingness to leave) can change the nature of the mechanism in elimination reactions. With poor leaving groups, the E1cB mechanism is favored, but as the leaving groups ability changes, the reaction shifts from having a rate determining loss of leaving group from carbanionic intermediate B via TS BC through having a rate determining deprotonation step via TS AB (not pictured) to a concerted E2 elimination. In the latter situation, the leaving group X has become good enough that the former transition state connecting intermediates B and C has become lower in energy than B, which is no longer a stationary point on the potential energy surface for the reaction. Because only one transition state connects starting material A and product C, the reaction is now concerted (albeit very asynchronous in the pictured case) due to the increase in leaving group ability of X. | 0 | Theoretical and Fundamental Chemistry |
Project GABRIEL opened a wide range of questions about formation, transformation, fallout and biological hazards due to bomb debris. GABRIEL supported work in research projects that might apply to the side effects of nuclear war. It was the sole support of the major research effort of Project SUNSHINE, which tested biological damage from radioactive fallout of Sr-90. By 1954 Project GABRIEL included about 70 investigations supported by the Division of Biology and Medicine. At a summer conference that was hosted by the RAND Corporation the estimate of detonations was revised and increased to 25,000 megatons worth of damage. Project Sunshine was led by radiation physicist Willard Libby on July 21, 1953. Libby realized GABRIEL lacked data in other aspects of fallout, examined carbon-14 and developed radiocarbon dating. The Project GABRIEL report by the AEC was issued in 1954, while the RAND Corporation issued their report on Project SUNSHINE in 1953. Both Project GABRIEL and SUNSHINE played a direct role in the reorganization of the AEC's Division of Biology and Medicine in 1957. | 0 | Theoretical and Fundamental Chemistry |
One rock, "Bounce Rock," found sitting on the sandy plains was found to be ejecta from an impact crater. Its chemistry was different from the bedrocks. Containing mostly pyroxene and plagioclase and no olivine, it closely resembled a part, Lithology B, of the shergottite meteorite EETA 79001, a meteorite known to have come from Mars. Bounce rock received its name by being near an airbag bounce mark. | 0 | Theoretical and Fundamental Chemistry |
In animal experiments diphenylamine was rapidly and completely absorbed after ingestion by mouth. It underwent metabolism to sulfonyl and glucuronyl conjugates and was rapidly excreted mainly via urine. Acute oral and dermal toxicity were low. Diphenylamine can cause severe irritation to the eyes. It was not a skin irritant, and it has not been technically feasible to test acute toxicity study by inhalation. Diphenylamine targets the red blood cell system and can cause abnormal erythropoiesis in the spleen, and thus congestion of the spleen, and haemosiderosis. Changes in liver and kidneys were found upon longer exposure. At clear toxic doses of parent animals reproductive effects were limited to reduced implantation sites in F1 females associated with reduced rat litter size, implicating a possible mutagenic or teratogenic effect. No effect on development could be attributed. The U.S. CDC's NIOSH lists the following symptoms of poisoning: irritation eyes, skin, mucous membrane; eczema; tachycardia, hypertension; cough, sneezing; methemoglobinemia; increased blood pressure and heart rate; proteinuria, hematuria (blood in the urine), bladder injury; in animals: teratogenic effects.
The short-term NOAEL of 9.6 – 10 mg/kg bw/day was derived from 90-day rat, 90-day dog and 1-year dog studies and the long-term NOAEL was 7.5 mg/kg bw/day.
The Acceptable Daily Intake of diphenylamine was 0.075 mg/kg bw/day based on the 2-year rat study, applying a safety factor of 100; the Acceptable Operator Exposure Level was 0.1 mg/kg bw/day.
In a study of diphenylamine metabolism in harvested and dipped apples at different time intervals it was observed that radiolabelled residues of diphenylamine penetrate from the surface into the pulp, which after 40 weeks contained 32% of the residue. Diphenylamine was always the major residue, but 3 metabolites were found in good amounts in the apple samples, whose identification experts considered insufficient.(Kim-Kang, H. 1993. Metabolism of 14C-diphenylamine in stored apples—nature of the residue in plants. Report RPT00124. Study XBL 91071. XenoBiotic Laboratories, Inc., USA, unpublished) cited in There is a data gap on presence or formation of nitrosamines in apple metabolism or during processing. The carcinogen 4-Aminobiphenyl can accompany diphenylamine as an impurity.
Diphenylamine has low acute and short-term toxicity to birds, but is very toxic to aquatic organisms. Risk to biological methods of sewage treatment was assessed as low.
The impurity in commercial diphenylamine which induces polycystic kidney disease in rats was identified in 1981. Laboratory studies with highly purified diphenylamine indicated that the impurity can be formed by heating diphenylamine. | 0 | Theoretical and Fundamental Chemistry |
The large number of synthetic organic chemicals currently in production presents a major challenge for timely collection of detailed environmental data on each compound. The concept of structure biodegradability relationships (SBR) has been applied to explain variability in persistence among organic chemicals in the environment. Early attempts generally consisted of examining the degradation of a homologous series of structurally related compounds under identical conditions with a complex "universal" inoculum, typically derived from numerous sources. This approach revealed that the nature and positions of substituents affected the apparent biodegradability of several chemical classes, with resulting general themes, such as halogens generally conferring persistence under aerobic conditions. Subsequently, more quantitative approaches have been developed using principles of QSAR and often accounting for the role of sorption (bioavailability) in chemical fate. | 1 | Applied and Interdisciplinary Chemistry |
The final steps from the common corrinoid intermediate E-37/HE-44 to cobyric acid E-44/HE-51 were carried out by the two groups collaboratively and in parallel, the ETH group working with material produced by the A/D approach, and the Harvard group with that from the A/B approach. What the two groups in fact accomplished thus were the common final steps of two different syntheses.
The tasks in this end phase of the project were the regioselective introduction of methyl groups at the two meso positions C-5 and C-15 of E-37/HE-44, followed by conversion of all its peripheral carboxyl functions into primary amide groups, excepting that in side chain f at ring D, which had to end up as free carboxyl. These conceptually simple finishing steps turned out to be rather complex in execution, including unforeseen pitfalls like a dramatic loss of precious synthetic material in the so-called "Black Friday" (July 9, 1971). | 0 | Theoretical and Fundamental Chemistry |
* "People, unfortunately, tend to equate nuclear with bombs. Im a passionate believer in the peaceful purposes of nuclear energy. What people dont realize is how many people are being helped to surmount medical problems with nuclear medicine."
* "The transmission of knowledge from one generation to the next remains for me the most noble of the professions." | 0 | Theoretical and Fundamental Chemistry |
Tire-derived fuel (TDF) is composed of shredded scrap tires. Tires may be mixed with coal or other fuels, such as wood or chemical wastes, to be burned in concrete kilns, power plants, or paper mills. An EPA test program concluded that, with the exception of zinc emissions, potential emissions from TDF are not expected to be very much different from other conventional fossil fuels, as long as combustion occurs in a well-designed, well-operated
and well-maintained combustion device.
In the United States in 2017, about 43% of scrap tires (1,736,340 tons or 106 million tires) were burnt as tire-derived fuel. Cement manufacturing was the largest user of TDF, at 46%, pulp and paper manufacturing used 29% and electric utilities used 25%. Another 25% of scrap tires were used to make ground rubber, 17% were disposed of in landfills and 16% had other uses. | 1 | Applied and Interdisciplinary Chemistry |
Intestinal organoids have thus far been among the gut organoids generated directly from intestinal tissues or pluripotent stem cells. One way human pluripotent stem cells can be driven to form intestinal organoids is through first the application of activin A to drive the cells into a mesoendodermal identity, followed by the pharmacological upregulation of Wnt3a and Fgf4 signaling pathways as they have been demonstrated to promote posterior gut fate. Intestinal organoids have also been generated from intestinal stem cells, extracted from adult tissue and cultured in 3D media. These adult stem cell-derived organoids are often referred to as enteroids or colonoids, depending on their segment of origin, and have been established from both the human and murine intestine. Intestinal organoids consist of a single layer of polarized intestinal epithelial cells surrounding a central lumen. As such, recapitulate the crypt-villus structure of the intestine, by recapitulating its function, physiology and organization, and maintaining all the cell types found normally in the structure including intestinal stem cells. Thus, intestinal organoids are a valuable model to study intestinal nutrient transport, drug absorption and delivery, nanomaterials and nanomedicine, incretin hormone secretion, and infection by various enteropathogens. For example, Qun Wang's team rationally designed artificial virus nanoparticles as oral drug delivery vehicles (ODDVs) with gut organoid-derived mucosal models and demonstrated a new concept of using newly established colon organoids as tools for high-throughput drug screening, toxicity testing, and oral drug development. Intestinal organoids also recapitulate the crypt-Villus structure to such a high degree of fidelity that they have been successfully transplanted to mouse intestines, and are hence highly regarded as a valuable model for research. One of the fields of research that intestinal organoids have been utilized is that of stem cell niche. Intestinal organoids were used to study the nature of the intestinal stem cell niche, and research done with them demonstrated the positive role IL-22 has in maintaining in intestinal stem cells, along with demonstrating the roles of other cell types like neurons and fibroblasts in maintenance of intestinal stem cells. In the field of infection biology, different intestinal organoid-based model systems have been explored. On one hand, organoids can be infected in bulk by simply mixing them with the enteropathogen of interest. However, to model infection via a more natural route starting from the intestinal lumen, microinjection of the pathogen is required. In addition, the polarity of intestinal organoids can be inverted, and they can even be dissociated into single cells and cultured as 2D monolayers in order to make both the apical and basolateral sides of the epithelium more easily accessible. Intestinal organoids have also demonstrated therapeutic potential.
In order to more accurately recapitulate the intestine in vivo, co-cultures of intestinal organoids and immune cells have been developed. Furthermore, organ-on-a-chip models combine intestinal organoids with other cell types such as endothelial or immune cells as well as peristaltic flow. | 1 | Applied and Interdisciplinary Chemistry |
The measurement of turbidity is a key test of both water clarity and water quality. There are two standard units for reporting turbidity: Formazin Nephelometric Units (FNU) from ISO 7027 and Nephelometric Turbidity Units (NTU) from USEPA Method 180.1. ISO 7027 and FNU is mostly widely used in Europe, whereas NTU is mostly widely used in the U.S. The ISO 7027 provides the method in water quality for the determination of turbidity. It is used to determine the concentration of suspended particles in a sample of water by measuring the incident light scattered at right angles from the sample. The scattered light is captured by a photodiode, which produces an electronic signal that is converted to a turbidity. Open source hardware has been developed following the ISO 7027 method to measure turbidity reliably using an Arduino microcontroller and inexpensive LEDs.
There are several practical ways of checking water quality, the most direct being some measure of attenuation (that is, reduction in strength) of light as it passes through a sample column of water. The alternatively used Jackson Candle method (units: Jackson Turbidity Unit or JTU) is essentially the inverse measure of the length of a column of water needed to completely obscure a candle flame viewed through it. The more water needed (the longer the water column), the clearer the water. Of course water alone produces some attenuation, and any substances dissolved in the water that produce color can attenuate some wavelengths. Modern instruments do not use candles, but this approach of attenuation of a light beam through a column of water should be calibrated and reported in JTUs.
The propensity of particles to scatter a light beam focused on them is now considered a more meaningful measure of turbidity in water. Turbidity measured this way uses an instrument called a nephelometer with the detector set up to the side of the light beam. More light reaches the detector if there are many small particles scattering the source beam than if there are few. The units of turbidity from a calibrated nephelometer can be either NTU or FTU, depending on the standard method used. To some extent, how much light reflects for a given amount of particulates is dependent upon properties of the particles like their shape, color, and reflectivity. For this reason (and the reason that heavier particles settle quickly and do not contribute to a turbidity reading), a correlation between turbidity and total suspended solids (TSS) is somewhat unusual for each location or situation.
Turbidity in lakes, reservoirs, channels, and the ocean can be measured using a Secchi disk. This black and white disk is lowered into the water until it can no longer be seen; the depth (Secchi depth) is then recorded as a measure of the transparency of the water (inversely related to turbidity). The Secchi disk has the advantages of integrating turbidity over depth (where variable turbidity layers are present), being quick and easy to use, and inexpensive. It can provide a rough indication of the depth of the euphotic zone with a 3-fold division of the Secchi depth, however this cannot be used in shallow waters where the disk can still be seen on the bottom.
An additional device, which may help measuring turbidity in shallow waters is the turbidity tube. The turbidity tube condenses water in a graded tube which allows determination of turbidity based on a contrast disk in its bottom, being analogous to the Secchi disk.
Turbidity in air, which causes solar attenuation, is used as a measure of pollution. To model the attenuation of beam irradiance, several turbidity parameters have been introduced, including the Linke turbidity factor (T). | 0 | Theoretical and Fundamental Chemistry |
The most common coordination number for d-block transition metal complexes is 6. The coordination number does not distinguish the geometry of such complexes, i.e. octahedral vs trigonal prismatic.
For transition metal complexes, coordination numbers range from 2 (e.g., Au in PhPAuCl) to 9 (e.g., Re in [ReH]). Metals in the f-block (the lanthanoids and actinoids) can accommodate higher coordination number due to their greater ionic radii and availability of more orbitals for bonding. Coordination numbers of 8 to 12 are commonly observed for f-block elements. For example, with bidentate nitrate ions as ligands, Ce and Th form the 12-coordinate ions [Ce(NO)] (ceric ammonium nitrate) and [Th(NO)]. When the surrounding ligands are much smaller than the central atom, even higher coordination numbers may be possible. One computational chemistry study predicted a particularly stable ion composed of a central lead ion coordinated with no fewer than 15 helium atoms. Among the Frank–Kasper phases, the packing of metallic atoms can give coordination numbers of up to 16. At the opposite extreme, steric shielding can give rise to unusually low coordination numbers. An extremely rare instance of a metal adopting a coordination number of 1 occurs in the terphenyl-based arylthallium(I) complex 2,6-TippCHTl, where Tipp is the 2,4,6-triisopropylphenyl group. | 0 | Theoretical and Fundamental Chemistry |
Denote the two ground states and the excited state of the electron and , respectively. The atom also has overall momentum, so the overall state of the atom is a product state of its internal state and its momentum, as shown in the figure. In the presence of counter-propagating beams of opposite polarization, the internal states experience the atom-light interaction Hamiltonian
where is the Rabi frequency, approximated to be the same for both transitions. Using the definition of the translation operator in momentum space,
the effect of on the state is
This suggests the dressed state that couples to is a more convenient basis state of the two ground states. The orthogonal basis state defined below does not couple to at all.
The action of on these states is
Thus, and undergo Sisyphus-like cooling, identifying the former as the bright state. is optically inaccessible and constitutes the dark state. However, and are not eigenstates of the momentum operator, and thus motionally couple to one another via the kinetic energy term of the unperturbed Hamiltonian:
As a result of this coupling, the dark state evolves into the bright state with frequency proportional to the momentum, effectively selecting hotter atoms to re-enter the Sisyphus cooling cycle. This nonadiabatic coupling occurs predominantly at the potential minima of the light-shifted coupling state. Over time, atoms cool until they lack the momentum to traverse the sinusoidal light shift of the bright state and instead populate the dark state. | 0 | Theoretical and Fundamental Chemistry |
Norvaline (abbreviated as Nva) is an amino acid with the formula CH(CH)CH(NH)COH. The compound is a structural analog of valeric acid and also an isomer of the more common amino acid valine. Like most other α-amino acids, norvaline is chiral. It is a white, water-soluble solid. | 1 | Applied and Interdisciplinary Chemistry |
Reaction intermediates are chemical species, often unstable and short-lived (however sometimes can be isolated), which are not reactants or products of the overall chemical reaction, but are temporary products and/or reactants in the mechanism's reaction steps. Reaction intermediates are often free radicals or ions.
The kinetics (relative rates of the reaction steps and the rate equation for the overall reaction) are explained in terms of the energy needed for the conversion of the reactants to the proposed transition states (molecular states that correspond to maxima on the reaction coordinates, and to saddle points on the potential energy surface for the reaction). | 0 | Theoretical and Fundamental Chemistry |
The exceptional yield strength of nanocrystalline metals is due to grain boundary strengthening, as grain boundaries are extremely effective at blocking the motion of dislocations. Yielding occurs when the stress due to dislocation pileup at a grain boundary becomes sufficient to activate slip of dislocations in the adjacent grain. This critical stress increases as the grain size decreases, and these physics are empirically captured by the Hall-Petch relationship,
where is the yield stress, is a material-specific constant that accounts for the effects of all other strengthening mechanisms, is a material-specific constant that describes the magnitude of the metal's response to grain size strengthening, and is the average grain size. Additionally, because nanocrystalline grains are too small to contain a significant number of dislocations, nanocrystalline metals undergo negligible amounts of strain-hardening, and nanocrystalline materials can thus be assumed to behave with perfect plasticity.
As the grain size continues to decrease, a critical grain size is reached at which intergranular deformation, i.e. grain boundary sliding, becomes more energetically favorable than intragranular dislocation motion. Below this critical grain size, often referred to as the “reverse” or “inverse” Hall-Petch regime, any further decrease in the grain size weakens the material because an increase in grain boundary area results in increased grain boundary sliding. Chandross & Argibay modeled grain boundary sliding as viscous flow and related the yield strength of the material in this regime to material properties as
where is the enthalpy of fusion, is the atomic volume in the amorphous phase, is the melting temperature, and is the volume fraction of material in the grains vs the grain boundaries, given by , where is the grain boundary thickness and typically on the order of 1 nm. The maximum strength of a metal is given by the intersection of this line with the Hall-Petch relationship, which typically occurs around a grain size of = 10 nm for BCC and FCC metals.
Due to the large amount of interfacial energy associated with a large volume fraction of grain boundaries, nanocrystalline metals are thermally unstable. In nanocrystalline samples of low-melting point metals (i.e. aluminum, tin, and lead), the grain size of the samples was observed to double from 10 to 20 nm after 24 hours of exposure to ambient temperatures. Although materials with higher melting points are more stable at room temperatures, consolidating nanocrystalline feedstock into a macroscopic component often requires exposing the material to elevated temperatures for extended periods of time, which will result in coarsening of the nanocrystalline microstructure. Thus, thermally stable nanocrystalline alloys are of considerable engineering interest. Experiments have shown that traditional microstructural stabilization techniques such as grain boundary pinning via solute segregation or increasing solute concentrations have proven successful in some alloy systems, such as Pd-Zr and Ni-W. | 1 | Applied and Interdisciplinary Chemistry |
In normal configuration, the light beam samples perpendicularly the electrode surface. Normal configuration provides optical information related to the changes that take place in the solution adjacent to the electrode and on the electrode surface. The optical path length coincides with the diffusion layer thickness, which is usually in the order of micrometers. This arrangement is the most suitable when the compound of interest is deposited or adsorbed on the working electrode, because it provides information about all processes occurring on the electrode surface.
UV-Vis absorption SEC in normal arrangement can be performed using both transmission and reflection phenomena.
* Normal transmission
In normal transmission, the light beam passes through a optically transparent working electrode, collecting information about the phenomena that take place on the surface of the electrode and on the solution adjacent to it. Electrodes in this configuration must be composed of materials that have great electrical conductivity and adequate optical transparency in the spectral region of interest.
The external reflection mode was proposed to improve the sensitivity and to use non-transparent electrodes.
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* Normal reflection
In normal reflection, the light beam travels in a perpendicular direction to the working electrode surface on which the reflection occurs. The reflected beam is collected to be analyzed in the spectrometer. It is also possible to work with other incidence and collection angles. This configuration is an alternative when the working electrode is non-transparent. In this configuration, the optical path-length in solution is on the order of twice the diffusion layer thickness. It should be noticed that growth of films on the electrode surface could cause optical interference phenomena. As it is based on reflection phenomenon, in many cases reflectance is used as unit of measurement instead of absorbance.
<br /> | 0 | Theoretical and Fundamental Chemistry |
In 1981, Taube became a founding member of the World Cultural Council. As of 1997, Taube had over 600 publications, and had worked with over 250 students. He published a book, Electron Transfer Reactions of Complex Ions in Solution (Current Chemical Concepts) in 1970. His students have had faculty positions at many prestigious universities, including Cornell, Rutgers, Georgetown and Georgia Tech. Together with graduate student Carol Creutz, he is the namesake of the Creutz-Taube complex, a metal complex with the formula Ru(NH)](CHN). His research contributions have been honored in several ways, including a symposium at the 1982 annual American Chemical Society meeting. The annual series Progress in Inorganic Chemistry dedicated its 30th volume to Taube, entitled "An Appreciation of Henry Taube." Luther College in Regina, Saskatchewan offers an annual scholarship to an entering science student in honor of Taube and his science teacher, Paul Liefeld. A seminar series was created in honor of his work at Stanford. Taube gave the inaugural lecture in the series.
Colleagues remember Taube as a dedicated scientist, Jim Collman of Stanford said "Henry was a scientist's scientist and a dominant figure in the field of inorganic chemistry." Harry Gray, a professor at California Institute of Technology said, "He was in a class by himself, a role model and leader whom we all admired and loved." Former student Peter Ford remembers that Taube "made chemistry not only challenging and stimulating, but a lot of fun as well." | 0 | Theoretical and Fundamental Chemistry |
Formol titration is one of the methods used in winemaking to measure yeast assimilable nitrogen needed by wine yeast in order to successfully complete fermentation. | 1 | Applied and Interdisciplinary Chemistry |
Tumor antigens are those antigens that are presented by MHC class I or MHC class II molecules on the surface of tumor cells. Antigens found only on such cells are called tumor-specific antigens (TSAs) and generally result from a tumor-specific mutation. More common are antigens that are presented by tumor cells and normal cells, called tumor-associated antigens (TAAs). Cytotoxic T lymphocytes that recognize these antigens may be able to destroy tumor cells.
Tumor antigens can appear on the surface of the tumor in the form of, for example, a mutated receptor, in which case they are recognized by B cells.
For human tumors without a viral etiology, novel peptides (neo-epitopes) are created by tumor-specific DNA alterations. | 1 | Applied and Interdisciplinary Chemistry |
Reaction of soluble lanthanum nitrate with an excess of oxalic acid:
Also, a reaction of lanthanum chloride with oxalic acid: | 0 | Theoretical and Fundamental Chemistry |
Antiandrogens that are currently on the market are particularly useful for the treatment of prostate cancer during the early stages. However, prostate cancer often progresses to a hormone-refractory state in which the cancer progresses in the presence of continued androgen ablation or antiandrogen therapy. This suggests that long term use of these antiandrogens during prostate cancer can lead to the development of androgen-independent prostate cancer cells or the ability of adrenal androgens to support tumor growth. This phenomenon is called antiandrogen withdrawal syndrome (AWS) and is one of the major drawbacks of existing antiandrogens. AWS is defined as tumor regression or symptomatic relief observed upon discontinuation of the antiandrogen therapy. The mechanism for this is not fully understood but current theories include alterations of the AR gene, coregulator proteins and/or signal transduction pathways. This antiandrogen resistance may also be linked to the relative weakness of current antiandrogens as they have an affinity 50 times or more lower than that of DHT for the AR. This may also explain why compensatory AR overexpression is often observed. | 1 | Applied and Interdisciplinary Chemistry |
In this case, the aglycone contains a cyanohydrin group. Plants that make cyanogenic glycosides store them in the vacuole, but, if the plant is attacked, they are released and become activated by enzymes in the cytoplasm. These remove the sugar part of the molecule, allowing the cyanohydrin structure to collapse and release toxic hydrogen cyanide. Storing them in inactive forms in the vacuole prevents them from damaging the plant under normal conditions.
Along with playing a role in deterring herbivores, in some plants they control germination, bud formation, carbon and nitrogen transport, and possibly act as antioxidants. The production of cyanogenic glycosides is an evolutionarily conserved function, appearing in species as old as ferns and as recent as angiosperms. These compounds are made by around 3,000 species. In screens they are found in about 11% of cultivated plants but only 5% of plants overall; humans seem to have selected for them.
Examples include amygdalin and prunasin which are made by the bitter almond tree; other species that produce cyanogenic glycosides are sorghum (from which dhurrin, the first cyanogenic glycoside to be identified, was first isolated), barley, flax, white clover, and cassava, which produces linamarin and lotaustralin.
Amygdalin and a synthetic derivative, laetrile, were investigated as potential drugs to treat cancer and were heavily promoted as alternative medicine; they are ineffective and dangerous.
Some butterfly species, such as the Dryas iulia and Parnassius smintheus, have evolved to use the cyanogenic glycosides found in their host plants as a form of protection against predators through their unpalatability. | 0 | Theoretical and Fundamental Chemistry |
Typically, for a large power station to approach the operational efficiency of computer models, steps must be taken to increase the electrical conductivity of the conductive substance. The heating of a gas to its plasma state or the addition of other easily ionizable substances like the salts of alkali metals can accomplish this increase. In practice, a number of issues must be considered in the implementation of an MHD generator: generator efficiency, economics, and toxic byproducts. These issues are affected by the choice of one of the three MHD generator designs: the Faraday generator, the Hall generator, and the disc generator. | 1 | Applied and Interdisciplinary Chemistry |
Memory and naïve B cells normally exist in relatively small numbers. As the body needs to be able to respond to a large number of potential pathogens, it maintains a pool of B cells with a wide range of specificities. Consequently, while there is almost always at least one B (naive or memory) cell capable of responding to any given epitope (of all that the immune system can react against), there are very few exact duplicates. However, when a single B cell encounters an antigen to which it can bind, it can proliferate very rapidly. Such a group of cells with identical specificity towards the epitope is known as a clone, and is derived from a common "mother" cell. All the "daughter" B cells match the original "mother" cell in their epitope specificity, and they secrete antibodies with identical paratopes. These antibodies are monoclonal antibodies, since they derive from clones of the same parent cell. A polyclonal response is one in which clones of multiple B cells react to the same antigen. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, pentagonal pyramidal molecular geometry describes the shape of compounds where in six atoms or groups of atoms or ligands are arranged around a central atom, at the vertices of a pentagonal pyramid. It is one of the few molecular geometries with uneven bond angles. | 0 | Theoretical and Fundamental Chemistry |
In naphtha cracking process, C4R2 refers to C4 residual obtained after separation of 1,3-butadiene and isobutylene from C4 raffinate stream and which mainly consists of cis- or trans-2-butene 50~60 wt%, 1-butene 10~15 wt%, and n-butane ~20 wt%. Normally C4R2 is a side product in tert-butyl alcohol plant if C4R1 is used for feed. | 0 | Theoretical and Fundamental Chemistry |
The overall goal of FSM is the protection of public and environmental health. FSM forms a key component of city-wide inclusive sanitation (CWIS), which considers all types of sanitation technologies in order to provide equitable, safe, and sustainable sanitation for everyone. CWIS employs a service delivery approach along the entire service chain, rather than just infrastructure provision.
Adequately and safely managed fecal sludge has the following benefits:
* Reduce the potential for human contact with fecal-borne pathogens by improving the functioning of onsite sanitation systems;
* Minimize odors and nuisances, and the uncontrolled discharge of organic matter from overflowing tanks or pits;
* Reduce indiscriminate disposal of collected fecal sludge;
* Production and sale of the end-products of the sludge treatment process. These products may include recycled water for agriculture and industry, soil conditioners from composting or co-composting materials, and energy products such as biogas, biodiesel, charcoal pellets, industrial powdered fuel, or electricity.
* Stimulate economic development, and job creation and livelihood opportunities, while addressing the issues of the social stigma and operator health and safety that continue to impact informal workers. This can also include jobs for contractors and equipment installers; for sanitation workers such as sludge collection personnel including drivers and emptiers; and for treatment and reuse systems operators. | 1 | Applied and Interdisciplinary Chemistry |
D-Xylose is a five-carbon aldose (pentose, monosaccharide) that can be catabolized or metabolized into useful products by a variety of organisms.
There are at least four different pathways for the catabolism of D-xylose: An oxido-reductase pathway is present in eukaryotic microorganisms. Prokaryotes typically use an isomerase pathway, and two oxidative pathways, called Weimberg and Dahms pathways respectively, are also present in prokaryotic microorganisms. | 1 | Applied and Interdisciplinary Chemistry |
First let us show that the relation is not only valid near the weak discontinuity, but throughout the region. If this inequality is not maintained, then there must be a point where between the weak discontinuity and the detonation front. The second governing equation implies that at this point must be infinite or, . Let us obtain by taking the second derivative of the governing equation. In the resulting equation, impose the condition to obtain . This implies that reaches a maximum at this point which in turn implies that cannot exist for greater than the maximum point considered since otherwise would be multi-valued. The maximum point at most can be corresponded to the outer boundary (detonation front). This means that can vanish only on the boundary and it is already shown that is positive near the weak discontinuity, is positive everywhere in the region except the boundaries where it can vanish.
Note that near the detonation front, we must satisfy the condition . The value evaluated at for the function , i.e., is nothing but the velocity of the detonation front with respect to the gas velocity behind it. For a detonation front, the condition must always be met, with the equality sign representing Chapman–Jouguet detonations and the inequalities representing over-driven detonations. The analysis describing the point must correspond to the detonation front. | 1 | Applied and Interdisciplinary Chemistry |
Boiler feedwater is an essential part of boiler operations. The feed water is put into the steam drum from a feed pump. In the steam drum the feed water is then turned into steam from the heat. After the steam is used, it is then dumped to the main condenser. From the condenser, it is then pumped to the deaerated feed tank. From this tank it then goes back to the steam drum to complete its cycle. The feedwater is never open to the atmosphere. This cycle is known as a closed system or Rankine cycle. | 1 | Applied and Interdisciplinary Chemistry |
Woodward was born in Boston, Massachusetts, on April 10, 1917. He was the son of Margaret Burns (an immigrant from Scotland who claimed to be a descendant of the poet, Robert Burns) and her husband, Arthur Chester Woodward, himself the son of Roxbury apothecary, Harlow Elliot Woodward.
His father was one of the many victims of the 1918 influenza pandemic.
From a very early age, Woodward was attracted to and engaged in private study of chemistry while he attended a public primary school, and then Quincy High School, in Quincy, Massachusetts. By the time he entered high school, he had already managed to perform most of the experiments in Ludwig Gattermanns then widely used textbook of experimental organic chemistry. In 1928, Woodward contacted the Consul-General of the German consulate in Boston (Baron von Tippelskirch ), and through him, managed to obtain copies of a few original papers published in German journals. Later, in his Cope lecture, he recalled how he had been fascinated when, among these papers, he chanced upon Diels and Alders original communication about the Diels–Alder reaction. Throughout his career, Woodward was to repeatedly and powerfully use and investigate this reaction, both in theoretical and experimental ways. In 1933, he entered the Massachusetts Institute of Technology (MIT), but neglected his formal studies badly enough to be excluded at the end of the 1934 fall term. MIT readmitted him in the 1935 fall term, and by 1936 he had received the Bachelor of Science degree. Only one year later, MIT awarded him the doctorate, when his classmates were still graduating with their bachelors degrees. Woodwards doctoral work involved investigations related to the synthesis of the female sex hormone estrone. MIT required that graduate students have research advisors. Woodward's advisors were James Flack Norris and Avery Adrian Morton, although it is not clear whether he actually took any of their advice. After a short postdoctoral stint at the University of Illinois, he took a Junior Fellowship at Harvard University from 1937 to 1938, and remained at Harvard in various capacities for the rest of his life. In the 1960s, Woodward was named Donner Professor of Science, a title that freed him from teaching formal courses so that he could devote his entire time to research. | 0 | Theoretical and Fundamental Chemistry |
In pharmacology, relative bioavailability measures the bioavailability (estimated as the AUC) of a formulation (A) of a certain drug when compared with another formulation (B) of the same drug, usually an established standard, or through administration via a different route. When the standard consists of intravenously administered drug, this is known as absolute bioavailability (see above).
Relative bioavailability is one of the measures used to assess bioequivalence (BE) between two drug products. For FDA approval, a generic manufacturer must demonstrate that the 90% confidence interval for the ratio of the mean responses (usually of AUC and the maximum concentration, C) of its product to that of the "brand name drug" is within the limits of 80% to 125%. Where AUC refers to the concentration of the drug in the blood over time t = 0 to t = ∞, C refers to the maximum concentration of the drug in the blood. When T is given, it refers to the time it takes for a drug to reach C.
While the mechanisms by which a formulation affects bioavailability and bioequivalence have been extensively studied in drugs, formulation factors that influence bioavailability and bioequivalence in nutritional supplements are largely unknown. As a result, in nutritional sciences, relative bioavailability or bioequivalence is the most common measure of bioavailability, comparing the bioavailability of one formulation of the same dietary ingredient to another. | 1 | Applied and Interdisciplinary Chemistry |
As of 2013, bottromycin has not been approved for any clinical applications, nor has it been tested in humans. The in vivo stability of bottromycin must be improved before it can be considered as a drug candidate. Work by Kobayashi and colleagues has already begun to address this issue, but more work may be in progress. The need to find new antibiotics to combat antibiotic resistance means that biologic and synthetic interest in bottromycin will likely continue. A combination of biologic and synthetic techniques may yield both an efficacious and stable bottromycin analog for development as a potential drug candidate. | 0 | Theoretical and Fundamental Chemistry |
A transcritical cycle is a closed thermodynamic cycle where the working fluid goes through both subcritical and supercritical states. In particular, for power cycles the working fluid is kept in the liquid region during the compression phase and in vapour and/or supercritical conditions during the expansion phase. The ultrasupercritical steam Rankine cycle represents a widespread transcritical cycle in the electricity generation field from fossil fuels, where water is used as working fluid. Other typical applications of transcritical cycles to the purpose of power generation are represented by organic Rankine cycles, which are especially suitable to exploit low temperature heat sources, such as geothermal energy, heat recovery applications or waste to energy plants. With respect to subcritical cycles, the transcritical cycle exploits by definition higher pressure ratios, a feature that ultimately yields higher efficiencies for the majority of the working fluids. Considering then also supercritical cycles as a valid alternative to the transcritical ones, the latter cycles are capable of achieving higher specific works due to the limited relative importance of the work of compression work. This evidences the extreme potential of transcritical cycles to the purpose of producing the most power (measurable in terms of the cycle specific work) with the least expenditure (measurable in terms of spent energy to compress the working fluid).
While in single level supercritical cycles both pressure levels are above the critical pressure of the working fluid, in transcritical cycles one pressure level is above the critical pressure and the other is below. In the refrigeration field carbon dioxide, CO, is increasingly considered of interest as refrigerant. | 0 | Theoretical and Fundamental Chemistry |
The term methylation in organic chemistry refers to the alkylation process used to describe the delivery of a group. | 0 | Theoretical and Fundamental Chemistry |
Phillips has directed his research toward the field of computational biology, primarily exploring protein structure. In the Phillips Lab, his work has involved conducting research on the binding of oxygen and ligands to heme proteins, as well as the development of techniques for analyzing protein and nucleic acid dynamics through diffuse X-ray scattering analysis. | 1 | Applied and Interdisciplinary Chemistry |
A common synthesis for porphyrins is the Rothemund reaction, first reported in 1936, which is also the basis for more recent methods described by Adler and Longo. The general scheme is a condensation and oxidation process starting with pyrrole and an aldehyde. | 1 | Applied and Interdisciplinary Chemistry |
CKLF-like MARVEL transmembrane domain-containing 5 (CMTM5), previously termed chemokine-like factor superfamily 5 (i.e. CKLFSF5), designates any one of the six protein isoforms (termed CMTM5-v1 to CMTM5-v6) encoded by six different alternative splices of its gene, CMTM5; CMTM5-v1 is the most studied of these isoforms. The CMTM5 gene is located in band 11.2 on the long (i.e. "q") arm of chromosome 14.
The CMTM5 isoforms are members of the CKLF-like MARVEL transmembrane domain-containing family (CMTM). This family consists of 9 proteins although most of them are known to have one or more isoforms. These proteins are: chemokine-like factor (i.e. CLF, the founding member of the family) and CEF-like marvel transmembrane domain-containing 1 through 8 (i.e. CMTM1 through CMTM8). All of these proteins as well as the genes responsible for their production (i.e. CKLF and CMTM1 to CMTM8, respectively) have similar structures but vary in their apparent physiological and pathological functions. Preliminary studies suggest that CMTM5-v1 (which cells commonly secrete to the extracellular spaces such as the blood) or an unspecified CMTM5 isoform has various functions including involvements in regulating the autoimmune system, the development of numerous types of cancers, and the cardiovascular system. | 1 | Applied and Interdisciplinary Chemistry |
A deficiency associated with lysosomal acid lipase deficiency, Wolman disease, and cholesteryl ester storage disease.
Chlorpromazine is an inhibitor of lysosomal lipase.
A genome wide survey suggests that lysosomal lipase A (located at chromosome 10q23.31) is associated with coronary artery disease in humans. | 1 | Applied and Interdisciplinary Chemistry |
If the acute inflammatory response persists, the body then proceeds to undergo chronic inflammation. During this continual and systemic inflammation phase, one of the primary driving forces is the infiltration of macrophages. The macrophages and lymphocytes induce the formation of new tissues and blood vessels to help supply nutrients to the biomaterial site. New fibrous tissue then encapsulates the foreign biomaterial in order to minimize interactions between the biomaterial and surrounding tissue. While the prolonging of chronic inflammation may be a likely indicator for an infection, inflammation may on occasion be present upwards to five years post-surgery. Chronic inflammation marked by the presence of fibrosis and inflammatory cells was observed in rat cells 30 days post implantation of a device.
Following chronic inflammation, mineralization occurs approximately 60 days after implantation due to the buildup of cellular debris and calcification, which has the potential to compromise the functionality of biocompatible implanted devices in vivo. | 1 | Applied and Interdisciplinary Chemistry |
The dbEST is a division of Genbank established in 1992. As for GenBank, data in dbEST is directly submitted by laboratories worldwide and is not curated. | 1 | Applied and Interdisciplinary Chemistry |
Current Organic Chemistry is a scientific review journal summarizing progress in the fields of asymmetric synthesis, organo-metallic chemistry, bioorganic chemistry, heterocyclic chemistry, natural product chemistry and analytical methods in organic chemistry. The journal is currently being edited by Dr. György Keglevich. | 0 | Theoretical and Fundamental Chemistry |
The vesicular monoamine transporter (VMAT) is a transport protein integrated into the membranes of synaptic vesicles of presynaptic neurons. It transports monoamine neurotransmitters – such as dopamine, serotonin, norepinephrine, epinephrine, and histamine – into the vesicles, which release the neurotransmitters into synapses, as chemical messages to postsynaptic neurons. VMATs utilize a proton gradient generated by V-ATPases in vesicle membranes to power monoamine import.
Pharmaceutical drugs that target VMATs have possible applications for many conditions, leading to a plethora of biological research, including hypertension, drug addiction, psychiatric disorders, Parkinson's disease, and other neurological disorders. Many drugs that target VMATs act as inhibitors and alter the kinetics of the protein. Much research regarding the effects of altered VMATs on biological systems is still ongoing. | 1 | Applied and Interdisciplinary Chemistry |
A Venturi can be used to measure the volumetric flow rate, , using Bernoulli's principle.
Since
then
A Venturi can also be used to mix a liquid with a gas. If a pump forces the liquid through a tube connected to a system consisting of a Venturi to increase the liquid speed (the diameter decreases), a short piece of tube with a small hole in it, and last a Venturi that decreases speed (so the pipe gets wider again), the gas will be sucked in through the small hole because of changes in pressure. At the end of the system, a mixture of liquid and gas will appear. See aspirator and pressure head for discussion of this type of siphon. | 1 | Applied and Interdisciplinary Chemistry |
In photosynthesis, singlet oxygen can be produced from the light-harvesting chlorophyll molecules. One of the roles of carotenoids in photosynthetic systems is to prevent damage caused by produced singlet oxygen by either removing excess light energy from chlorophyll molecules or quenching the singlet oxygen molecules directly.
In mammalian biology, singlet oxygen is one of the reactive oxygen species, which is linked to oxidation of LDL cholesterol and resultant cardiovascular effects. Polyphenol antioxidants can scavenge and reduce concentrations of reactive oxygen species and may prevent such deleterious oxidative effects.
Ingestion of pigments capable of producing singlet oxygen with activation by light can produce severe photosensitivity of skin (see phototoxicity, photosensitivity in humans, photodermatitis, phytophotodermatitis). This is especially a concern in herbivorous animals (see Photosensitivity in animals).
Singlet oxygen is the active species in photodynamic therapy. | 0 | Theoretical and Fundamental Chemistry |
Historically, the chemical engineer has been primarily concerned with process engineering, which can generally be divided into two complementary areas: chemical reaction engineering and separation processes. The modern discipline of chemical engineering, however, encompasses much more than just process engineering. Chemical engineers are now engaged in the development and production of a diverse range of products, as well as in commodity and specialty chemicals. These products include high-performance materials needed for aerospace, automotive, biomedical, electronic, environmental and military applications. Examples include ultra-strong fibers, fabrics, adhesives and composites for vehicles, bio-compatible materials for implants and prosthetics, gels for medical applications, pharmaceuticals, and films with special dielectric, optical or spectroscopic properties for opto-electronic devices. Additionally, chemical engineering is often intertwined with biology and biomedical engineering. Many chemical engineers work on biological projects such as understanding biopolymers (proteins) and mapping the human genome. | 1 | Applied and Interdisciplinary Chemistry |
Hydrolysis of boronic esters back to the boronic acid and the alcohol can be accomplished in certain systems with thionyl chloride and pyridine.
Aryl boronic acids or esters may be hydrolyzed to the corresponding phenols by reaction with hydroxylamine at room temperature. | 0 | Theoretical and Fundamental Chemistry |
Condensation with ketones and aldehydes yields the corresponding N-tert-butanesulfinyl aldimines and ketimines. These intermediates are more resistant to hydrolysis than other imines but more reactive towards nucleophiles. A nucleophile adds diastereoselectively over the imine group in an electrophilic addition with the tert-butanesulfinyl group acting as a chiral auxiliary. This tert-butanesulfinyl group is also a protecting group. On addition of hydrochloric acid the tert-butanesulfinyl group is removed, forming the chiral primary ammonium salt or amine (from aldehyde precursor) or the chiral secondary amine (ketone precursor).
Typical nucleophiles are Grignard reagents, organozinc compounds, organolithium compounds, and enolates.
Chiral sulfinimines as intermediates for the asymmetric synthesis of amines have also been developed by Franklin A. Davis. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.eawag.ch/en/department/surf/projects/chemeql/ ChemEQL] Free software for calculation of chemical equilibria from Eawag.
* [http://www.factsage.com/ FactSage] Commercial thermodynamic databank software, also available in a free [http://www.crct.polymtl.ca/ephweb.php?lang= web application].
* [http://www.gwb.com/pourbaix.php The Geochemist's Workbench] Commercial geochemical modeling software from Aqueous Solutions LLC.
* [http://community.gwb.com/pourbaix.php GWB Community Edition] Free download of the popular geochemical modeling software package.
* [http://www.kth.se/che/medusa/ HYDRA/MEDUSA] Free software for creating chemical equilibrium diagrams from the KTH Department of Chemistry.
* [http://www.outotec.com/products/digital-solutions/hsc-chemistry/hsc-eph--eh-ph-diagrams-module HSC Chemistry] Commercial thermochemical calculation software from Outotec Oy.
* [http://www.phreeplot.org/ PhreePlot] Free program for making geochemical plots using the USGS code [http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/ PHREEQC].
* [https://web.archive.org/web/20140424142253/http://www.thermocalc.com/solutions/application/corrosion/ Thermo-Calc Windows] Commercial software for thermodynamic calculations from Thermo-Calc Software.
* [https://materialsproject.org/ Materials Project] Public website that can generate Pourbaix diagrams from a large database of computed material properties, hosted at NERSC. | 0 | Theoretical and Fundamental Chemistry |
The momentum equation for open-channel flow may be found by starting from the incompressible Navier-Stokes equations :where is the pressure, is the kinematic viscosity, is the Laplace operator, and is the gravitational potential. By invoking the high Reynolds number and 1D flow assumptions, we have the equations:<math display="block">\begin{aligned}
{\partial u\over{\partial t}} + u{\partial u\over{\partial x}} &= -{1\over{\rho}}{\partial p\over{\partial x}} + F_{x} \\
-{1\over{\rho}}{\partial p\over{\partial z}} - g &= 0
\end{aligned}, where the channel depth is the difference between the free surface elevation and the channel bottom . Substitution into the first equation gives:where the channel bed slope . To account for shear stress along the channel banks, we may define the force term to be:where is the shear stress and is the hydraulic radius. Defining the friction slope , a way of quantifying friction losses, leads to the final form of the momentum equation: | 1 | Applied and Interdisciplinary Chemistry |
The CRFs in thin layer chromatography characterize the equal-spreading of the spots. The ideal case, when the RF of the spots are uniformly distributed in <0,1> range (for example 0.25,0.5 and 0.75 for three solutes) should be characterized as the best situation possible.
The simplest criteria are and product (Wang et al., 1996). They are the smallest difference between sorted RF values, or product of such differences.
Another function is the multispot response function (MRF) as developed by De Spiegeleer et al.{Analytical Chemistry (1987):59(1),62-64} It is based also of differences product. This function always lies between 0 and 1. When two RF values are equal, it is equal to 0, when all RF values are equal-spread, it is equal to 1. The L and U values – upper and lower limit of RF – give possibility to avoid the band region.
The last example of coefficient sensitive to minimal distance between spots is Retention distance (Komsta et al., 2007)
The second group are criteria insensitive for minimal difference between RF values (if two compounds are not separated, such CRF functions will not indicate it). They are equal to zero in equal-spread state increase when situation is getting worse.
There are:
Separation response (Bayne et al., 1987)
Performance index (Gocan et al., 1991)
Informational entropy (Gocan et al., 1991, second reference)
Retention uniformity (Komsta et al., 2007)
In all above formulas, n is the number of compounds separated, R are the Retention factor of the compounds sorted in non-descending order, R = 0 and R = 1. | 0 | Theoretical and Fundamental Chemistry |
De Silva et al. constructed an OR molecular logic gate using an aza-crown ether receptor and sodium and potassium ions as the inputs. Either of the two ions could bind to the crown ether, causing the PET to be quenched and the fluorescence to be turned on. Since either of the two ions (input “1”) could turn on the fluorescence (output “1”), the system resembled an OR logic gate. | 0 | Theoretical and Fundamental Chemistry |
A molybdenum imido complex appears in a common nitrogen fixation cycle:
: Mo•NH (ammine);
with the oxidation state of molybdenum varying to accommodate the number bonds from nitrogen. | 0 | Theoretical and Fundamental Chemistry |
A sulfoxide, R−S(O)−R, is the S-oxide of a sulfide ("sulfide oxide"), a sulfone, R−S(O)−R, is the S,S-dioxide of a sulfide, a thiosulfinate, R−S(O)−S−R, is the S-oxide of a disulfide, and a thiosulfonate, R−S(O)−S−R, is the S,S-dioxide of a disulfide. All of these compounds are well known with extensive chemistry, e.g., dimethyl sulfoxide, dimethyl sulfone, and allicin (see drawing). | 0 | Theoretical and Fundamental Chemistry |
In addition to this division, lithotrophs differ in the initial energy source which initiates ATP production:
* Chemolithotrophs use the above-mentioned inorganic compounds for aerobic or anaerobic respiration. The energy produced by the oxidation of these compounds is enough for ATP production. Some of the electrons derived from the inorganic donors also need to be channeled into biosynthesis. Mostly, additional energy has to be invested to transform these reducing equivalents to the forms and redox potentials needed (mostly NADH or NADPH), which occurs by reverse electron transfer reactions.
* Photolithotrophs use light as their energy source. These organisms are photosynthetic; examples of photolithotrophic bacteria are purple bacteria (e. g., Chromatiaceae), green bacteria (Chlorobiaceae and Chloroflexota), and "Cyanobacteria". Purple and green bacteria oxidize sulfide, sulfur, sulfite, iron or hydrogen. Cyanobacteria and plants extract reducing equivalents from water, i.e., they oxidize water to oxygen. The electrons obtained from the electron donors are not used for ATP production (as long as there is light); they are used in biosynthetic reactions. Some photolithotrophs shift over to chemolithotrophic metabolism in the dark. | 1 | Applied and Interdisciplinary Chemistry |
(+)-Discodermolide is a polyketide natural product found to stabilize microtubules. (+)-discodermolide was isolated by Gunasekera and his co-workers at the Harbor Branch Oceanographic Institute from the deep-sea sponge Discodermia dissoluta in 1990. (+)-Discodermolide was found to be a potent inhibitor of tumor cell growth in several MDR cancer cell lines. (+)-discodermolide also shows some unique characters, including a linear backbone structure, immunosuppressive properties both in vitro and in vivo, potent induction of an accelerated senescence phenotype, and synergistic antiproliferative activity in combination with paclitaxel. Discodermolide was recognized as one of the most potent natural promoters of tubulin assembly. A large number of efforts toward the total synthesis of (+)-discodermolide were directed by its interesting biological activities and extreme scarcity of natural sources (0.002% w/w from frozen marine sponge). The compound supply necessary for complete clinical trials cannot be met by harvesting, isolation, and purification. As of 2005, attempts at synthesis or semi-synthesis by fermentation have proven unsuccessful. As a result, all discodermolide used in preclinical studies and clinical trials has come from large-scale total synthesis. | 0 | Theoretical and Fundamental Chemistry |
Many plant expression vectors are based on the Ti plasmid of Agrobacterium tumefaciens. In these expression vectors, DNA to be inserted into plant is cloned into the T-DNA, a stretch of DNA flanked by a 25-bp direct repeat sequence at either end, and which can integrate into the plant genome. The T-DNA also contains the selectable marker. The Agrobacterium provides a mechanism for transformation, integration of into the plant genome, and the promoters for its vir genes may also be used for the cloned genes. Concerns over the transfer of bacterial or viral genetic material into the plant however have led to the development of vectors called intragenic vectors whereby functional equivalents of plant genome are used so that there is no transfer of genetic material from an alien species into the plant.
Plant viruses may be used as vectors since the Agrobacterium method does not work for all plants. Examples of plant virus used are the tobacco mosaic virus (TMV), potato virus X, and cowpea mosaic virus. The protein may be expressed as a fusion to the coat protein of the virus and is displayed on the surface of assembled viral particles, or as an unfused protein that accumulates within the plant. Expression in plant using plant vectors is often constitutive, and a commonly used constitutive promoter in plant expression vectors is the cauliflower mosaic virus (CaMV) 35S promoter. | 1 | Applied and Interdisciplinary Chemistry |
While magnets can be used to localize magnetic nanoparticles to desired cells, this mechanism may be difficult to maintain in practice. The nanoparticles can be concentrated in 2D space such as on a culture plate or at the surface of the body, but it can be more difficult to localize them in the 3D space of the body. Magnetofection does not work well for organs or blood vessels far from the surface of the body, since the magnetic field weakens as distance increases. In addition, the user must consider the frequency and timing of applying the magnetic field, as the particles will not necessarily stay in the desired location once the magnet is removed. | 1 | Applied and Interdisciplinary Chemistry |
Schlögl received numerous scientific awards for his work, including the Erwin Schrödinger Prize of the Austrian Academy of Sciences in 1985, the prize for natural sciences of the city of Vienna in 1989, and the Wilhelm Exner Medal of the Austrian Economic Association in 1991. | 0 | Theoretical and Fundamental Chemistry |
Disulfide bonds are usually formed from the oxidation of sulfhydryl () groups, especially in biological contexts. The transformation is depicted as follows:
A variety of oxidants participate in this reaction including oxygen and hydrogen peroxide. Such reactions are thought to proceed via sulfenic acid intermediates. In the laboratory, iodine in the presence of base is commonly employed to oxidize thiols to disulfides. Several metals, such as copper(II) and iron(III) complexes affect this reaction. Alternatively, disulfide bonds in proteins often formed by thiol-disulfide exchange:
Such reactions are mediated by enzymes in some cases and in other cases are under equilibrium control, especially in the presence of a catalytic amount of base.
The alkylation of alkali metal di- and polysulfides gives disulfides. "Thiokol" polymers arise when sodium polysulfide is treated with an alkyl dihalide. In the converse reaction, carbanionic reagents react with elemental sulfur to afford mixtures of the thioether, disulfide, and higher polysulfides. These reactions are often unselective but can be optimized for specific applications. | 0 | Theoretical and Fundamental Chemistry |
Some clays are thixotropic, with their behavior of great importance in structural and geotechnical engineering. Landslides, such as those common in the cliffs around Lyme Regis, Dorset and in the Aberfan spoil tip disaster in Wales are evidence of this phenomenon. Similarly, a lahar is a mass of earth liquefied by a volcanic event, which rapidly solidifies once coming to rest.
Drilling muds used in geotechnical applications can be thixotropic. Honey from honey bees may also exhibit this property under certain conditions (such as heather honey or mānuka honey).
Both cytoplasm and the ground substance in the human body are thixotropic, as is semen.
Some clay deposits found in the process of exploring caves exhibit thixotropism: an initially solid-seeming mudbank will turn soupy and yield up moisture when dug into or otherwise disturbed. These clays were deposited in the past by low-velocity streams which tend to deposit fine-grained sediment.
A thixotropic fluid is best visualised by an oar blade embedded in mud. Pressure on the oar often results in a highly viscous (more solid) thixotropic mud on the high pressure side of the blade, and low viscosity (very fluid) thixotropic mud on the low pressure side of the oar blade. Flow from the high pressure side to the low pressure side of the oar blade is non-Newtonian. (i.e., fluid velocity is not linearly proportional to the square root of the pressure differential over the oar blade). | 1 | Applied and Interdisciplinary Chemistry |
A number of methods exist in the literature for the preparation of diazirines, which begin from a variety of reagents. | 0 | Theoretical and Fundamental Chemistry |
A Knudsen gas is a gas in a state of such low density that the average distance travelled by the gas molecules between collisions (mean free path) is greater than the diameter of the receptacle that contains it. If the mean free path is much greater than the diameter, the flow regime is dominated by collisions between the gas molecules and the walls of the receptacle, rather than intermolecular collisions with each other. It is named after Martin Knudsen. | 0 | Theoretical and Fundamental Chemistry |
Rigid copper is a popular choice for water lines. It is joined using a sweat, compression or crimped/pressed connection. Rigid copper, rigid due to the work hardening of the drawing process, cannot be bent and must use elbow fittings to go around corners or around obstacles. If heated and allowed to slowly cool, called annealing, then rigid copper will become soft and can be bent/formed without cracking. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, head is a concept that relates the energy in an incompressible fluid to the height of an equivalent static column of that fluid. From Bernoullis principle, the total energy at a given point in a fluid is the kinetic energy associated with the speed of flow of the fluid, plus energy from static pressure in the fluid, plus energy from the height of the fluid relative to an arbitrary datum. Head is expressed in units of distance such as meters or feet. The force per unit volume on a fluid in a gravitational field is equal to ρg where ρ is the density of the fluid, and g' is the gravitational acceleration. On Earth, additional height of fresh water adds a static pressure of about 9.8 kPa per meter (0.098 bar/m) or 0.433 psi per foot of water column height.
The static head of a pump is the maximum height (pressure) it can deliver. The capability of the pump at a certain RPM can be read from its Q-H curve (flow vs. height).
Head is useful in specifying centrifugal pumps because their pumping characteristics tend to be independent of the fluid's density.
There are generally four types of head:
#Velocity head is due to the bulk motion (kinetic energy) of a fluid. Note that is equal to the dynamic pressure for irrotational flow.
#Elevation head is due to the fluids weight, the gravitational force acting on a column of fluid. The elevation head is simply the elevation (h') of the fluid above an arbitrarily designated zero point:
#Pressure head is due to the static pressure, the internal molecular motion of a fluid that exerts a force on its container. It is equal to the pressure divided by the force/volume of the fluid in a gravitational field:
#Resistance head (or friction head or Head Loss) is due to the frictional forces acting against a fluids motion by the container. For a continuous medium, this is described by Darcys law which relates volume flow rate (q) to the gradient of the hydraulic head through the hydraulic conductivity K: while in a piped system head losses are described by the Hagen–Poiseuille equation and Bernoulli’s equation. | 1 | Applied and Interdisciplinary Chemistry |
His first important research work, undertaken as part of his doctoral studies under E. H. Riesenfeld in the early 1920s, concerned ozone, . Schwab was the first to describe the preparation of pure ozone and its solidification, thereby accurately determining many of its physical constants. At the time, it was still not certain whether the tetratomic species oxozone, , was also present in ozone samples. The work of young Schwab conclusively refuted the century-old theory of oxozone, which led to the exceptional grade of his dissertation. | 0 | Theoretical and Fundamental Chemistry |
An important observation from Stokes' solution for the oscillating Stokes flow is that vorticity oscillations are confined to a thin boundary layer and damp exponentially when moving away from the wall. This observation is also valid for the case of a turbulent boundary layer. Outside the Stokes boundary layer – which is often the bulk of the fluid volume – the vorticity oscillations may be neglected. To good approximation, the flow velocity oscillations are irrotational outside the boundary layer, and potential flow theory can be applied to the oscillatory part of the motion. This significantly simplifies the solution of these flow problems, and is often applied in the irrotational flow regions of sound waves and water waves. | 1 | Applied and Interdisciplinary Chemistry |
Samples are registered through Allocating Agents. At present (November 2021) the following IGSN Allocation Agents register IGSN:
* System for Earth Sample Registration (SESAR)
* Geoscience Australia
* Commonwealth Scientific and Industrial Research Organisation Mineral Resources
* Australian Research Data Commons (ARDC)
* University of Bremen MARUM
* German Research Centre for Geosciences (GFZ)
* IFREMER Institut Français de Recherche pour l'Exploitation de la Mer
* Korea Institute of Geoscience & Mineral Resources (KIGAM)
* University of Kiel
To obtain an IGSN, users need to register a sample by submitting information about it to an IGSN Allocating Agent. Once logged in, users can:
* register individual samples or batches
* register sampling features
* track relationships between samples and subsamples (e.g., bulk samples and mineral separates)
* update information on registered samples
* download QR code images for labelling purposes | 0 | Theoretical and Fundamental Chemistry |
Industrial separation processes are technical procedures which are used in industry to separate a product from impurities or other products. The original mixture may either be a natural resource (like ore, oil or sugar cane) or the product of a chemical reaction (like a drug or an organic solvent). | 0 | Theoretical and Fundamental Chemistry |
The most common type of mass spectrometer (MS) associated with a gas chromatograph (GC) is the quadrupole mass spectrometer, sometimes referred to by the Hewlett-Packard (now Agilent) trade name "Mass Selective Detector" (MSD). Another relatively common detector is the ion trap mass spectrometer. Additionally one may find a magnetic sector mass spectrometer, however these particular instruments are expensive and bulky and not typically found in high-throughput service laboratories. Other detectors may be encountered such as time of flight (TOF), tandem quadrupoles (MS-MS) (see below), or in the case of an ion trap MS where n indicates the number mass spectrometry stages. | 0 | Theoretical and Fundamental Chemistry |
Nitric acid plays a key role in PUREX and other nuclear fuel reprocessing methods, where it can dissolve many different actinides. The resulting nitrates are converted to various complexes that can be reacted and extracted selectively in order to separate the metals from each other. | 0 | Theoretical and Fundamental Chemistry |
The carbon–fluorine bond is a polar covalent bond between carbon and fluorine that is a component of all organofluorine compounds. It is one of the strongest single bonds in chemistry (after the B–F single bond, Si–F single bond, and H–F single bond), and relatively short, due to its partial ionic character. The bond also strengthens and shortens as more fluorines are added to the same carbon on a chemical compound. As such, fluoroalkanes like tetrafluoromethane (carbon tetrafluoride) are some of the most unreactive organic compounds. | 0 | Theoretical and Fundamental Chemistry |
The chemical reaction for the dissolution of gold, the "Elsner equation", follows:
: 4Au + 8NaCN + O + 2HO → 4Na[Au(CN)] + 4NaOH
Potassium cyanide and calcium cyanide are sometimes used in place of sodium cyanide.
Gold is one of the few metals that dissolves in the presence of cyanide ions and oxygen. The soluble gold species is dicyanoaurate. from which it can be recovered by adsorption onto activated carbon. | 1 | Applied and Interdisciplinary Chemistry |
The Parkes process is a pyrometallurgical industrial process for removing silver from lead during the production of bullion. It is an example of liquid–liquid extraction.
The process takes advantage of two liquid-state properties of zinc. The first is that zinc is immiscible with lead, and the other is that silver is 3000 times more soluble in zinc than it is in lead. When zinc is added to liquid lead that contains silver as a contaminant, the silver preferentially migrates into the zinc. Because the zinc is immiscible in the lead it remains in a separate layer and is easily removed. The zinc-silver solution is then heated until the zinc vaporizes, leaving nearly pure silver. If gold is present in the liquid lead, it can also be removed and isolated by the same process.
The process was patented by Alexander Parkes in 1850. Parkes received two additional patents in 1852.
The Parkes process was not adopted in the United States, due to the low native production of lead. The problems were overcome during the 1880s and by 1923 only when the Parkes process was used. | 1 | Applied and Interdisciplinary Chemistry |
Cisplatin has a number of side effects that can limit its use:
* Nephrotoxicity (kidney damage) is the primary dose-limiting side effect and is of major clinical concern. Cisplatin selectively accumulates into the proximal tubule via basolateral-to-apical transport, where it disrupts mitochondrial energetics and endoplasmic reticulum Ca homeostasis and stimulates reactive oxygen species and pro-inflammatory cytokines. Multiple mitigation strategies are being explored clinically and pre-clinically, including hydration regimens, amifostine, transporter inhibitors, antioxidants, anti-inflammatories, and epoxyeicosatrienoic acids and their analogues.
* Neurotoxicity (nerve damage) can be anticipated by performing nerve conduction studies before and after treatment. Common neurological side effects of cisplatin include visual perception and hearing disorder, which can occur soon after treatment begins. While triggering apoptosis through interfering with DNA replication remains the primary mechanism of cisplatin, this has not been found to contribute to neurological side effects. Recent studies have shown that cisplatin noncompetitively inhibits an archetypal, membrane-bound mechanosensitive sodium-hydrogen ion transporter known as NHE-1. It is primarily found on cells of the peripheral nervous system, which are aggregated in large numbers near the ocular and aural stimuli-receiving centers. This noncompetitive interaction has been linked to hydroelectrolytic imbalances and cytoskeleton alterations, both of which have been confirmed in vitro and in vivo. However, NHE-1 inhibition has been found to be both dose-dependent (half-inhibition = 30 μg/mL) and reversible. Cisplatin can increase levels of sphingosine-1-phosphate in the central nervous system, contributing to the development of post-chemotherapy cognitive impairment.
* Nausea and vomiting: cisplatin is one of the most emetogenic chemotherapy agents, but this symptom is managed with prophylactic antiemetics (ondansetron, granisetron, etc.) in combination with corticosteroids. Aprepitant combined with ondansetron and dexamethasone has been shown to be better for highly emetogenic chemotherapy than just ondansetron and dexamethasone.
* Ototoxicity and hearing loss associated with cisplatin can be severe and is considered to be a dose-limiting side effect. Audiometric analysis may be necessary to assess the severity of ototoxicity. Other drugs (such as the aminoglycoside antibiotic class) may also cause ototoxicity, and the administration of this class of antibiotics in patients receiving cisplatin is generally avoided. The ototoxicity of both the aminoglycosides and cisplatin may be related to their ability to bind to melanin in the stria vascularis of the inner ear or the generation of reactive oxygen species. In September 2022, the U.S. Food and Drug Administration (FDA) approved sodium thiosulfate under the brand name Pedmark to lessen the risk of ototoxicity and hearing loss in people receiving cisplatin. There is ongoing investigation of acetylcysteine injections as a preventative measure.
* Electrolyte disturbance: Cisplatin can cause hypomagnesaemia, hypokalaemia and hypocalcaemia. The hypocalcaemia seems to occur in those with low serum magnesium secondary to cisplatin, so it is not primarily due to the cisplatin.
* Hemolytic anemia can be developed after several courses of cisplatin. It is suggested that an antibody reacting with a cisplatin-red-cell membrane is responsible for hemolysis. | 1 | Applied and Interdisciplinary Chemistry |
Coherent microwave scattering from electrons in REMPI-induced plasma filaments adds the capability to measure selectively-ionized species with a high spatial and temporal resolution - allowing for nonintrusive determinations of concentration profiles without the use of physical probes or electrodes. It has been applied for the detection of species such as argon, xenon, nitric oxide, carbon monoxide, atomic oxygen, and methyl radicals both within enclosed cells, open air, and atmospheric flames.
Microwave detection is based on homodyne or heterodyne technologies. They can significantly increase the detection sensitivity by suppressing the noise and follow sub-nanosecond plasma generation and evolution. The homodyne detection method mixes the detected microwave electric field with its own source to produce a signal proportional to the product of the two. The signal frequency is converted down from tens of gigahertz to below one gigahertz so that the signal can be amplified and observed with standard electronic devices. Because of the high sensitivity associated with the homodyne detection method, the lack of background noise in the microwave regime, and the capability of time gating of the detection electronics synchronous with the laser pulse, very high SNRs are possible even with milliwatt microwave sources. These high SNRs allow the temporal behavior of the microwave signal to be followed on a sub-nanosecond time scale. Thus the lifetime of electrons within the plasma can be recorded. By utilizing a microwave circulator, a single microwave horn transceiver has been built, which significantly simplifies the experimental setup.
Detection in the microwave region has numerous advantages over optical detection. Using homodyne or heterodyne technologies, the electric field rather than the power can be detected, so much better noise rejection can be achieved. In contrast to optical heterodyne techniques, no alignment or mode matching of the reference is necessary. The long wavelength of the microwaves leads to effective point coherent scattering from the plasma in the laser focal volume, so phase matching is unimportant and scattering in the backward direction is strong. Many microwave photons can be scattered from a single electron, so the amplitude of the scattering can be increased by increasing the power of the microwave transmitter. The low energy of the microwave photons corresponds to thousands of more photons per unit energy than in the visible region, so shot noise is drastically reduced. For weak ionization characteristic of trace species diagnostics, the measured electric field is a linear function of the number of electrons which is directly proportional to the trace species concentration. Furthermore, there is very little solar or other natural background radiation in the microwave spectral region. | 0 | Theoretical and Fundamental Chemistry |
DAST is prepared by the reaction of diethylaminotrimethylsilane and sulfur tetrafluoride:
:EtNSiMe + SF → EtNSF + MeSiF
The original paper calls for trichlorofluoromethane (Freon-11) as a solvent. Diethyl ether is a green alternative that can be used with no decrease in yield. Because of the dangers involved in the preparation of DAST (glass etching, possibility of exothermic events), it is often purchased from a commercial source. At one time Carbolabs was one of the few suppliers of the chemical but a number of companies now sell DAST. Carbolabs was acquired by Sigma-Aldrich in 1998. | 0 | Theoretical and Fundamental Chemistry |
The WGSR has been extensively studied for over a hundred years. The kinetically relevant mechanism depends on the catalyst composition and the temperature. Two mechanisms have been proposed: an associative Langmuir–Hinshelwood mechanism and a redox mechanism. The redox mechanism is generally regarded as kinetically relevant during the high-temperature WGSR (> 350 °C) over the industrial iron-chromia catalyst. Historically, there has been much more controversy surrounding the mechanism at low temperatures. Recent experimental studies confirm that the associative carboxyl mechanism is the predominant low temperature pathway on metal-oxide-supported transition metal catalysts. | 0 | Theoretical and Fundamental Chemistry |
In 2021, the first brain metabolome atlas of the mouse brain – and of an animal (a mammal) across different life stages – was released online. The data differentiates by brain regions and the metabolic changes could be "mapped to existing gene and protein brain atlases". | 1 | Applied and Interdisciplinary Chemistry |
Moiety conservation is the conservation of a subgroup in a chemical species, which is cyclically transferred from one molecule to another. In biochemistry, moiety conservation can have profound effects on the system's dynamics. | 1 | Applied and Interdisciplinary Chemistry |
It is a member of the small pentraxins family (also known as short pentraxins). The polypeptide encoded by this gene has 224 amino acids. The full-length polypeptide is not present in the body in significant quantities due to signal peptide, which is removed by signal peptidase before translation is completed. The complete protein, composed of five monomers, has a total mass of approximately 120,000 Da. In serum, it assembles into stable pentameric structure with a discoid shape. | 1 | Applied and Interdisciplinary Chemistry |
Hydrogen cyanide forms in at least limited amounts from many combinations of hydrogen, carbon, and ammonia. Hydrogen cyanide is produced in large quantities by several processes and is a recovered waste product from the manufacture of acrylonitrile. In 2006, between 500 million and 1 billion pounds (between 230,000 and 450,000 t) were produced in the US.
The most important process is the Andrussow oxidation invented by Leonid Andrussow at IG Farben in which methane and ammonia react in the presence of oxygen at about over a platinum catalyst:
:2 CH + 2 NH + 3 O → 2 HCN + 6 HO
The energy needed for the reaction is provided by the partial oxidation of methane and ammonia.
Of lesser importance is the Degussa process (BMA process) in which no oxygen is added and the energy must be transferred indirectly through the reactor wall:
:CH + NH → HCN + 3H
This reaction is akin to steam reforming, the reaction of methane and water to give carbon monoxide and hydrogen.
In the Shawinigan Process, hydrocarbons, e.g. propane, are reacted with ammonia.
In the laboratory, small amounts of HCN are produced by the addition of acids to cyanide salts of alkali metals:
:H + NaCN → HCN + Na
This reaction is sometimes the basis of accidental poisonings because the acid converts a nonvolatile cyanide salt into the gaseous HCN.
Hydrogen cyanide could be obtained from potassium ferricyanide and acid:
:6 H + [Fe(CN)] → 6 HCN + Fe | 0 | Theoretical and Fundamental Chemistry |
The glycocalyx is located on the apical surface of vascular endothelial cells which line the lumen. When vessels are stained with cationic dyes such as Alcian blue stain, transmission electron microscopy shows a small, irregularly shaped layer extending approximately 50–100 nm into the lumen of a blood vessel. Another study used osmium tetroxide staining during freeze substitution, and showed that the endothelial glycocalyx could be up to 11 μm thick. It is present throughout a diverse range of microvascular beds (capillaries) and macrovessels (arteries and veins). The glycocalyx also consists of a wide range of enzymes and proteins that regulate leukocyte and thrombocyte adherence, since its principal role in the vasculature is to maintain plasma and vessel-wall homeostasis. These enzymes and proteins include:
*Endothelial nitric oxide synthase (endothelial NOS)
*Extracellular superoxide dismutase (SOD3)
*Angiotensin converting enzyme
*Antithrombin-III
*Lipoprotein lipase
*Apolipoproteins
*Growth factors
*Chemokines
The enzymes and proteins listed above serve to reinforce the glycocalyx barrier against vascular and other diseases. Another main function of the glycocalyx within the vascular endothelium is that it shields the vascular walls from direct exposure to blood flow, while serving as a vascular permeability barrier. Its protective functions are universal throughout the vascular system, but its relative importance varies depending on its exact location in the vasculature. In microvascular tissue, the glycocalyx serves as a vascular permeability barrier by inhibiting coagulation and leukocyte adhesion. Leukocytes must not stick to the vascular wall because they are important components of the immune system that must be able to travel to a specific region of the body when needed. In arterial vascular tissue, the glycocalyx also inhibits coagulation and leukocyte adhesion, but through mediation of shear stress-induced nitric oxide release. Another protective function throughout the cardiovascular system is its ability to affect the filtration of interstitial fluid from capillaries into the interstitial space.
The glycocalyx, which is located on the apical surface of endothelial cells, is composed of a negatively charged network of proteoglycans, glycoproteins, and glycolipids. Along the luminal surface of the vascular glycocalyx exists an empty layer that excludes red blood cells. | 1 | Applied and Interdisciplinary Chemistry |
Different protecting groups on either the glycosyl donor or the glycosyl acceptor may affect the reactivity and yield of the glycosylation reaction. Typically, electron-withdrawing groups such as acetyl or benzoyl groups are found to decrease the reactivity of the donor/acceptor and are therefore termed "disarming" groups. Electron-donating groups such as the benzyl group, are found to increase the reactivity of the donor/acceptor and are therefore called "arming" groups. | 0 | Theoretical and Fundamental Chemistry |
Carbon-14, C-14, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934.
There are three naturally occurring isotopes of carbon on Earth: carbon-12 (), which makes up 99% of all carbon on Earth; carbon-13 (), which makes up 1%; and carbon-14 (), which occurs in trace amounts, making up about 1 or 1.5 atoms per 10 atoms of carbon in the atmosphere. Carbon-12 and carbon-13 are both stable, while carbon-14 is unstable and has a half-life of years. Carbon-14 has a maximum specific activity of 62.4 mCi/mmol (2.31 GBq/mmol), or 164.9 GBq/g. Carbon-14 decays into nitrogen-14 () through beta decay. A gram of carbon containing 1 atom of carbon-14 per 10 atoms will emit ~0.2 beta particles per second. The primary natural source of carbon-14 on Earth is cosmic ray action on nitrogen in the atmosphere, and it is therefore a cosmogenic nuclide. However, open-air nuclear testing between 1955 and 1980 contributed to this pool.
The different isotopes of carbon do not differ appreciably in their chemical properties. This resemblance is used in chemical and biological research, in a technique called carbon labeling: carbon-14 atoms can be used to replace nonradioactive carbon, in order to trace chemical and biochemical reactions involving carbon atoms from any given organic compound. | 0 | Theoretical and Fundamental Chemistry |
Reverse osmosis is a more economical way to concentrate liquids (such as fruit juices) than conventional heat-treatment. Concentration of orange and tomato juice has advantages including a lower operating cost and the ability to avoid heat-treatment, which makes it suitable for heat-sensitive substances such as protein and enzymes.
RO is used in the dairy industry to produce whey protein powders and concentrate milk. The whey (liquid remaining after cheese manufacture) is concentrated with RO from 6% solids to 10–20% solids before ultrafiltration processing. The retentate can then be used to make whey powders, including whey protein isolate. Additionally, the permeate, which contains lactose, is concentrated by RO from 5% solids to 18–total solids to reduce crystallization and drying costs.
Although RO was once avoided in the wine industry, it is now widespread. An estimated 60 RO machines were in use in Bordeaux, France, in 2002. Known users include many of elite firms, such as Château Léoville-Las Cases. | 0 | Theoretical and Fundamental Chemistry |
The classification of soil structural forms is based largely on shape.
# Spheroidal structure: sphere-like or rounded in shape. All the axes are approximately of the same dimensions, with curved and irregular faces. These are found commonly in cultivated fields.
## Crumb structure: small and are like crumbs of bread due to them being porous
## Granular structure: less porous than crumb structure aggregates and are more durable than crumb structure aggregates
# Plate-like structure: mainly horizontally aligned along plant based areas, with thin units being laminar and the thick units of the aggregates are classified as platy. Platy structures are usually found in the surface and sometimes in the lower sub-soils.
# Block-like structure: particles that are arranged around a central point are enclosed by surfaces that may be either flat or somewhat rounded. These types are generally found in subsoil.
## Sub angular blocky: corners are more rounded than the angular blocky aggregates
# Prism-like structure: particles that are longer than they are wide, with the vertical axis being greater than the horizontal axis. They are commonly found in subsoil horizon of arid and semi-arid region soils.
## Prismatic: more angular and hexagonal at the top of the aggregate
## Columnar: particles that are rounded at the top of the aggregate | 0 | Theoretical and Fundamental Chemistry |
The smelting process was often carried out away from the rest of the community. Ironworkers engaged in rituals designed to encourage good production and to ward off bad spirits, including song and prayers, plus the giving of medicines and sacrifices. The latter were usually put in the furnace itself or buried under the base of the furnace. Examples of these date back as far as the early Iron Age in Tanzania and Rwanda (Schmidt 1997 in Childs et al., 2005 p. 293).
Some cultures associated sexual symbolism with iron production. Smelting was integrated with the fertility of their society, The production of the bloom was compared to human conception and birth. There were sexual taboos surrounding the process. The smelting process was carried out entirely by men and often away from the village. For women to touch any of the materials or be present could jeopardise the success of the production. The furnaces were also often adorned to resemble a woman, the mother of the bloom. | 1 | Applied and Interdisciplinary Chemistry |
In nucleophilic aliphatic substitution, sodium nitrite (NaNO) replaces an alkyl halide. In the so-called Ter Meer reaction (1876) named after Edmund ter Meer, the reactant is a 1,1-halonitroalkane:
The reaction mechanism is proposed in which in the first slow step a proton is abstracted from nitroalkane 1 to a carbanion 2 followed by protonation to an aci-nitro 3 and finally nucleophilic displacement of chlorine based on an experimentally observed hydrogen kinetic isotope effect of 3.3. When the same reactant is reacted with potassium hydroxide the reaction product is the 1,2-dinitro dimer. | 0 | Theoretical and Fundamental Chemistry |
Levosalbutamol is the INN while levalbuterol is the USAN.
Levalbuterol was approved in the United States as a solution to be used with a nebulizer device in March 1999 and in March 2015 became available in a formulation with a metered-dose inhaler under the trade name Xopenex HFA (levalbuterol tartrate inhalation aerosol). | 0 | Theoretical and Fundamental Chemistry |
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