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Full genome sequencing provides information on a genome that is orders of magnitude larger than by DNA arrays, the previous leader in genotyping technology.
For humans, DNA arrays currently provide genotypic information on up to one million genetic variants, while full genome sequencing will provide information on all six billion bases in the human genome, or 3,000 times more data. Because of this, full genome sequencing is considered a disruptive innovation to the DNA array markets as the accuracy of both range from 99.98% to 99.999% (in non-repetitive DNA regions) and their consumables cost of $5000 per 6 billion base pairs is competitive (for some applications) with DNA arrays ($500 per 1 million basepairs). | 1 | Applied and Interdisciplinary Chemistry |
A common application is mixing nozzles for two-component adhesives (e.g., epoxy) and sealants (see Resin casting). Other applications include wastewater treatment and chemical processing. Static mixers can be used in the refinery and oil and gas markets as well, for example in bitumen processing or for desalting crude oil. In polymer production, static mixers can be used to facilitate polymerization reactions or for the admixing of liquid additives. | 1 | Applied and Interdisciplinary Chemistry |
The Irwin screen was as of 2010 in the pharmaceutical industry almost exclusively used with lab mice, whereas the FOB, or some modification thereof, was used with lab rats and other nonrodent species, such as rabbits, dogs, guinea pigs and nonhuman primates. | 1 | Applied and Interdisciplinary Chemistry |
The use of anti-graffiti barrier coatings to protect graffiti-prone historic buildings, monuments, and other culturally-sensitive surfaces may seem to be an easy solution to a persistent problem. Research suggests that the application of such coatings can cause physical or aesthetic changes or otherwise damage historic substrates. Both the National Park Service and English Heritage advise against the use of anti-graffiti coatings and promote the exercise of caution when they are applied to historic buildings and monuments.
In the United States, many state and local historic district commissions and review boards have regulations that require approval for both graffiti removal work and the application of coatings applied to the facades on designated landmarks or properties located in local historic districts. Alternatives to anti-graffiti barrier coatings include security measures such as night lighting and surveillance cameras, design strategies such as barrier plantings and fences, improved maintenance of the general area and rapid graffiti removal, as well as community awareness raising programs like a neighborhood watch. | 0 | Theoretical and Fundamental Chemistry |
With the advent of stable isotope ratio mass spectrometry, isotopic signatures of materials find increasing use in forensics, distinguishing the origin of otherwise similar materials and tracking the materials to their common source. For example, the isotope signatures of plants can be to a degree influenced by the growth conditions, including moisture and nutrient availability. In case of synthetic materials, the signature is influenced by the conditions during the chemical reaction. The isotopic signature profiling is useful in cases where other kinds of profiling, e.g. characterization of impurities, are not optimal. Electronics coupled with scintillator detectors are routinely used to evaluate isotope signatures and identify unknown sources.
A study was published demonstrating the possibility of determination of the origin of a common brown PSA packaging tape by using the carbon, oxygen, and hydrogen isotopic signature of the backing polymer, additives, and adhesive.
Measurement of carbon isotopic ratios can be used for detection of adulteration of honey. Addition of sugars originated from corn or sugar cane (C4 plants) skews the isotopic ratio of sugars present in honey, but does not influence the isotopic ratio of proteins; in an unadulterated honey the carbon isotopic ratios of sugars and proteins should match. As low as 7% level of addition can be detected.
Nuclear explosions form Be by a reaction of fast neutrons with C in the carbon dioxide in air. This is one of the historical indicators of past activity at nuclear test sites. | 0 | Theoretical and Fundamental Chemistry |
Hydrocolloids contain some type of gel-forming agent, such as sodium carboxymethylcellulose (NaCMC) and gelatin. They are normally combined with some type of sealant, i.e. polyurethane to stick to the skin. | 0 | Theoretical and Fundamental Chemistry |
Two regimes of stack effect can exist in buildings: normal and reverse. Normal stack effect occurs in buildings which are maintained at a higher temperature than the outdoor environment. Warm air within the building has a low density (or high specific volume) and exhibits a greater buoyancy force. Consequently, it rises from lower levels to upper levels through penetrations between floors. This presents a situation where floors underneath the neutral axis of the building have a net negative pressure, whereas floors above the neutral axis have a net positive pressure. The net negative pressure on lower floors can induce outdoor air to infiltrate the building through doors, windows, or ductwork without backdraft dampers. Warm air will attempt to exfiltrate the building envelope through floors above the neutral axis.
Mechanical refrigeration equipment provides sensible and latent cooling during summer months. This reduces the dry-bulb temperature of the air within the building relative to the outdoor ambient air. It also decreases the specific volume of the air contained within the building, thereby reducing the buoyancy force. Consequently, cool air will travel vertically down the building through elevator shafts, stairwells, and unsealed utility penetrations (i.e., hydronics, electric and water risers). Once the conditioned air reaches the bottom floors underneath the neutral axis, it exfiltrates the building envelopes through unsealed openings such as through dampers, curtainwall, etc. The exfiltrating air on floors underneath the neutral axis will induce outdoor air to infiltrate the building envelope through unsealed openings. | 0 | Theoretical and Fundamental Chemistry |
Generally, the main process in a rotary vacuum drum filter is continuous filtration whereby solids are separated from liquids through a filter medium by a vacuum. The filter cloth is one of the most important components on a filter and is typically made of weaving polymer yarns. The best selection of cloth can increase the performance of filtration. Initially, slurry is pumped into the trough and as the drum rotates, it is partially submerged in the slurry. The vacuum draws liquid and air through the filter media and out the shaft hence forming a layer of cake. An agitator is used to regulate the slurry if the texture is coarse and it is settling rapidly. Solids that are trapped on the surface of the drum are washed and dried after 2/3 of revolution, removing all the free moisture.
During the washing stage, the wash liquid can either be poured onto the drum or sprayed on the cake. Cake pressing is optional but its advantages are preventing cake cracking and removing more moisture. Cake discharge is when all the solids are removed from the surface of the cake by a scraper blade, leaving a clean surface as drum re-enters the slurry. There are a few types of discharge which are scraper, roller, string, endless belt and pre coat. The filtrate and air flow through internal pipes, valve and into the vacuum receiver where the separation of liquid and gas occurs producing a clear filtrate. Pre coat filtration is an ideal method to produce a high clarity of filtrate. Basically, the drum surface is pre coated with a filter aid such as diatomaceous earth (DE) or perlite to improve filtration and increase cake permeability. It then undergoes the same process cycle as the conventional rotary vacuum drum filter however, pre coat filtration uses a higher precision blade to scrape off the cake.
The filter is assessed by the size of the drum or filter area and its possible output. Typically, the output is in the units of pounds per hour of dry solids per square foot of filter area. The size of the auxiliary parts depends on the area of the filter and the type of usage. Rotary vacuum filters are flexible in handling variety of materials therefore the estimated solids yield from 5 to 200 pounds per hour per square foot. For pre coat discharge, the solid output is approximately 2 to 40 gallons per hour per square foot. Filtration efficiencies can also be improved in terms dryness of filter cake by significantly preventing filtrate liquid from getting stuck in the filter drum during filtration phase. Usage of multiple filters for example, running 3 filter units instead of 2 units yields a thicker cake hence, producing a clearer filtrate. This becomes beneficial in terms of production cost and also quality. | 0 | Theoretical and Fundamental Chemistry |
Thylakoid membranes contain integral membrane proteins which play an important role in light-harvesting and the light-dependent reactions of photosynthesis. There are four major protein complexes in the thylakoid membrane:
*Photosystems I and II
*Cytochrome b6f complex
*ATP synthase
Photosystem II is located mostly in the grana thylakoids, whereas photosystem I and ATP synthase are mostly located in the stroma thylakoids and the outer layers of grana. The cytochrome b6f complex is distributed evenly throughout thylakoid membranes. Due to the separate location of the two photosystems in the thylakoid membrane system, mobile electron carriers are required to shuttle electrons between them. These carriers are plastoquinone and plastocyanin. Plastoquinone shuttles electrons from photosystem II to the cytochrome b6f complex, whereas plastocyanin carries electrons from the cytochrome b6f complex to photosystem I.
Together, these proteins make use of light energy to drive electron transport chains that generate a chemiosmotic potential across the thylakoid membrane and NADPH, a product of the terminal redox reaction. The ATP synthase uses the chemiosmotic potential to make ATP during photophosphorylation. | 0 | Theoretical and Fundamental Chemistry |
In this shuttle, the enzyme called cytoplasmic glycerol-3-phosphate dehydrogenase 1 (GPD1 or cGPD) converts dihydroxyacetone phosphate (2) to glycerol 3-phosphate (1) by oxidizing one molecule of NADH to NAD as in the following reaction:
Glycerol-3-phosphate is converted back to dihydroxyacetone phosphate by an inner membrane-bound mitochondrial glycerol-3-phosphate dehydrogenase 2 (GPD2 or mGPD), this time reducing one molecule of enzyme-bound flavin adenine dinucleotide (FAD) to FADH. FADH then reduces coenzyme Q (ubiquinone to ubiquinol) whose electrons enter into oxidative phosphorylation. This reaction is irreversible. These electrons bypass Complex I of the electron transport chain, making the glycerol-3-phosphate shuttle less energetically efficient compared to oxidation of NADH by Complex I. | 1 | Applied and Interdisciplinary Chemistry |
The conversion of ammonium to nitrate is performed primarily by soil-living bacteria and other nitrifying bacteria. In the primary stage of nitrification, the oxidation of ammonium () is performed by bacteria such as the Nitrosomonas species, which converts ammonia to nitrites (). Other bacterial species such as Nitrobacter, are responsible for the oxidation of the nitrites () into nitrates (). It is important for the ammonia () to be converted to nitrates or nitrites because ammonia gas is toxic to plants.
Due to their very high solubility and because soils are highly unable to retain anions, nitrates can enter groundwater. Elevated nitrate in groundwater is a concern for drinking water use because nitrate can interfere with blood-oxygen levels in infants and cause methemoglobinemia or blue-baby syndrome. Where groundwater recharges stream flow, nitrate-enriched groundwater can contribute to eutrophication, a process that leads to high algal population and growth, especially blue-green algal populations. While not directly toxic to fish life, like ammonia, nitrate can have indirect effects on fish if it contributes to this eutrophication. Nitrogen has contributed to severe eutrophication problems in some water bodies. Since 2006, the application of nitrogen fertilizer has been increasingly controlled in Britain and the United States. This is occurring along the same lines as control of phosphorus fertilizer, restriction of which is normally considered essential to the recovery of eutrophied waterbodies. | 1 | Applied and Interdisciplinary Chemistry |
Test samples are filtered through standard filter paper and then transferred to M-endo or LES Endo Agar mediums. Colonies appear pinkish-red with green metallic sheen after 22–24 hours of incubation. These colonies can be confirmed as coliforms if they are inoculated in lauryl tryptose (LST), produce gas, and then inoculated in BGLB. If there is gas production in the BGLB tubes, the test is positive for the presence of coliform bacteria. | 0 | Theoretical and Fundamental Chemistry |
An example is the auxin mediated derepression of the auxin response factor family of transcription factors in plants. These auxin response factors are repressed by Aux/IAA repressors. In the presence of auxin, these Aux/AII proteins undergo ubiquitination and are then degraded. This derepresses the auxin response factors so they may carry out their functions in the cell. | 1 | Applied and Interdisciplinary Chemistry |
Soil organic matter is the largest source of nutrients and energy in a soil. Its inputs strongly influence key soil factors such as types of biota, pH, and even soil order. Soil organic matter is often strategically applied by plant growers because of its ability to improve soil structure, supply nutrients, manage pH, increase water retention, and regulate soil temperature (which directly affects water dynamics and biota).
The chief elements found in humus, the product of organic matter decomposition in soil, are carbon, hydrogen, oxygen, sulphur and nitrogen. The important compound found in humus are carbohydrates, phosphoric acid, some organic acids, resins, urea etc. Humus is a dynamic product and is constantly changing because of its oxidation, reduction and hydrolysis; hence, it has much carbon content and less nitrogen. This material can come from a variety of sources, but often derives from livestock manure and plant residues.
Though there are many other variables, such as texture, soils that lack sufficient organic matter content are susceptible to soil degradation and drying, as there is nothing supporting the soil structure. This often leads to a decline in soil fertility and an increase in erodibility.
Other associated concepts:
* Anion and cation exchange capacity
* Soil pH
* Mineral formation and transformation processes and pedogenesis
* Clay mineralogy
* Sorption and precipitation reactions in soil
* Chemistry of problem soils
* C/N ratio
* Erosion and soil degradation | 0 | Theoretical and Fundamental Chemistry |
Zerovalent iron (ZVI) is jargon that describes forms of iron metal that are proposed for used in Groundwater remediation.
ZVI operates by electron transfer from Fe toward some organochlorine compounds, a common class of pollutants. The remediation process is proposed to generate Fe and Cl and halide-free organic products, all of which are relatively innocuous. The technology is not however been implemented, despite many proofs of principle. | 1 | Applied and Interdisciplinary Chemistry |
The alloy has the highest magnetostriction of any alloy, up to 0.002 m/m at saturation; it expands and contracts in a magnetic field. Terfenol-D has a large magnetostriction force, high energy density, low sound velocity, and a low Youngs modulus. At its most pure form, it also has low ductility and a low fracture resistance. Terfenol-D is a gray alloy that has different possible ratios of its elemental components that always follow a formula of . The addition of dysprosium made it easier to induce magnetostrictive responses by making the alloy require a lower level of magnetic fields. When the ratio of Tb and Dy is increased, the resulting alloys magnetostrictive properties will operate at temperatures as low as −200 °C, and when decreased, it may operate at a maximum of 200 °C. The composition of Terfenol-D allows it to have a large magnetostriction and magnetic flux when a magnetic field is applied to it. This case exists for a large range of compressive stresses, with a trend of decreasing magnetostriction as the compressive stress increases. There is also a relationship between the magnetic flux and compression in which when the compressive stress increases, the magnetic flux changes less drastically. Terfenol-D is mostly used for its magnetostrictive properties, in which it changes shape when exposed to magnetic fields in a process called magnetization. Magnetic heat treatment is shown to improve the magnetostrictive properties of Terfenol-D at low compressive stress for certain ratios of Tb and Dy. | 1 | Applied and Interdisciplinary Chemistry |
* Solids control : 40–80% reduction
* Pollution control : COD/BOD reduction – 40–90%
* Fecal coliforms control : 50–100% reduction
* Ecotoxicity : Nil
* Dissolved oxygen : Increased by 150% – 1200%
* Aquatic species :
** Increase in plants/plankton – 200%
** Increase in micro-invertebrates – 200%
Other than the changes in the water quality mentioned above a multifold change in population of avifauna, terrestrial plants along the riverbanks has been noticed. There is an overall odour and mosquito reduction and improvement of river aesthetics. Increase in health status of aquatic life in lentic-lotic system by reduction in ecotoxicity of pollutants. | 1 | Applied and Interdisciplinary Chemistry |
* Chemists' Club of New York, 1974
* Pharmaceutical Society of Japan, 1973
* Chemical Society of Japan, 2002
* Royal Society of Chemistry, UK, 1983
* Chairman Organic Division of the American Chemical Society, 1966–1967 | 0 | Theoretical and Fundamental Chemistry |
NCOA6 has been shown to interact with:
* ASCL2 and
* Activating transcription factor 2,
* Androgen receptor,
* CREB-binding protein,
* DNA-PKcs,
* E2F1,
* EP300,
* Estrogen receptor alpha,
* Estrogen receptor beta,
* HBXIP,
* HIST2H3C,
* HSF1,
* Ku70,
* Ku80,
* Liver X receptor beta,
* MLL3,
* RBBP5,
* Retinoblastoma protein,
* Retinoic acid receptor alpha,
* Retinoid X receptor alpha,
* Src,
* TGS1,
* TUBA4A,
* TUBB,
* Thyroid hormone receptor alpha, and
* Thyroid hormone receptor beta. | 1 | Applied and Interdisciplinary Chemistry |
Hydroperoxides or peroxols are compounds of the form ROOH, where R stands for any group, typically organic, which contain the hydroperoxy functional group (). Hydroperoxide also refers to the hydroperoxide anion () and its salts, and the neutral hydroperoxyl radical (•OOH) consist of an unbond hydroperoxy group. When R is organic, the compounds are called organic hydroperoxides. Such compounds are a subset of organic peroxides, which have the formula ROOR. Organic hydroperoxides can either intentionally or unintentionally initiate explosive polymerisation in materials with unsaturated chemical bonds. | 0 | Theoretical and Fundamental Chemistry |
There is a hypothesis that states that TEs might provide a ready source of DNA that could be co-opted by the cell to help regulate gene expression. Research showed that many diverse modes of TEs co-evolution along with some transcription factors targeting TE-associated genomic elements and chromatin are evolving from TE sequences. Most of the time, these particular modes do not follow the simple model of TEs and regulating host gene expression. | 1 | Applied and Interdisciplinary Chemistry |
Convection (or convective heat transfer) is the transfer of heat from one place to another due to the movement of fluid. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined processes of conduction (heat diffusion) and advection (heat transfer by bulk fluid flow). Convection is usually the dominant form of heat transfer in liquids and gases.
Note that this definition of convection is only applicable in Heat transfer and thermodynamic contexts. It should not be confused with the dynamic fluid phenomenon of convection, which is typically referred to as Natural Convection in thermodynamic contexts in order to distinguish the two. | 0 | Theoretical and Fundamental Chemistry |
For large wavelengths (small ), only the first term is relevant and one has gravity waves.
In this limit, the waves have a group velocity half the phase velocity: following a single wave's crest in a group one can see the wave appearing at the back of the group, growing and finally disappearing at the front of the group. | 1 | Applied and Interdisciplinary Chemistry |
Upregulation refers to the increase in the number of receptor sites on the membrane. Estrogen upregulates FSH receptor sites. In turn, FSH stimulates granulosa cells to produce estrogens. This synergistic activity of estrogen and FSH allows for follicle growth and development in the ovary. | 1 | Applied and Interdisciplinary Chemistry |
Perfluorinated oxaziridines are known to hydroxylate unactivated hydrocarbons with remarkable regio- and diastereospecificity. This is a highly coveted transformation, and similar reactivity and specificity is seldom rivaled, especially considering the nonmetallic nature of the oxidant. Perfluorinated oxaziridines show high selectivity toward tertiary hydrogens. Hydroxylation of primary carbons and dihydroxylation of a compound with two oxidizable sites have never been observed. Retention of stereochemistry is very high, often 95 to 98%. (Retention of stereochemistry may be further enhanced by the addition of a fluoride salt). | 0 | Theoretical and Fundamental Chemistry |
Lightly crosslinked refers to the lightly woven polymer portion of the scavenger. This type of resin becomes swollen in a particular solvent, allowing an impurity to react with a specified functional group. In many times single solvents are not sufficient to expand the resin, in which case a second solvent must be added. Examples of a secondary solvent, or co-solvent, would be Tetrahydrofuran, or THF. Typically contain 1–3% of divinylbenzene. | 0 | Theoretical and Fundamental Chemistry |
sAC activation by bicarbonate is necessary for motility and other aspects of capacitation in the spermatozoa of mammals. In human males, mutations in the ADCY10 gene that lead to the inactivation of sAC have been linked to cases of sterility. Due to this essential role in male fertility, sAC has been explored as a potential target for non-hormonal male contraception. | 1 | Applied and Interdisciplinary Chemistry |
Russell S. Drago was born November 5, 1928, in Montague, Massachusetts to Stephen R. Drago and Lillia Mary Margret (Pucci) Drago.
In 1950, Drago married Ruth Ann Burrill (January 29, 1929 – November 9, 2013). They remained married for 47 years until his death. They had four children, Patti Kouba (Drago), Steve, Paul, and Robert. | 0 | Theoretical and Fundamental Chemistry |
In metal borides, the bonding of boron varies depending on the atomic ratio B/M. Diborides have B/M = 2, as in the well-known superconductor MgB; they crystallize in a hexagonal AlB-type layered structure. Hexaborides have B/M = 6 and form a three-dimensional boron framework based on a boron octahedron (Fig. 1a). Tetraborides, i.e. B/M = 4, are mixtures of diboride and hexaboride structures. Cuboctahedron (Fig. 1b) is the structural unit of dodecaborides, which have a cubic lattice and B/M = 12. When the composition ratio exceeds 12, boron forms B icosahedra (Fig. 1c) which are linked into a three-dimensional boron framework, and the metal atoms reside in the voids of this framework.
This complex bonding behavior originates from the fact that boron has only three valence electrons; this hinders tetrahedral bonding as in diamond or hexagonal bonding as in graphite. Instead, boron atoms form polyhedra. For example, three boron atoms make up a triangle where they share two electrons to complete the so-called three-center bonding. Boron polyhedra, such as B octahedron, B cuboctahedron and B icosahedron, lack two valence electrons per polyhedron to complete the polyhedron-based framework structure. Metal atoms need to donate two electrons per boron polyhedron to form boron-rich metal borides. Thus, boron compounds are often regarded as electron-deficient solids. The covalent bonding nature of metal boride compounds also give them their hardness and inert chemical reactivity property.
Icosahedral B compounds include α-rhombohedral boron (BC), β-rhombohedral boron (MeB, 23≤x), α-tetragonal boron (BBC), β-tetragonal boron (β-AlB), AlB or AlCB, YB, YB, YB, NaB or MgAlB, γ-AlB, BeB and SiB.
YB and YB decompose without melting that hinders their growth as single crystals by the floating zone method. However, addition of a small amount of Si solves this problem and results in single crystals with the stoichiometry of YBSi. This stabilization technique allowed the synthesis of some other boron-rich rare-earth borides.
Albert and Hillebrecht reviewed binary and selected ternary boron compounds containing main-group elements, namely, borides of the alkali and alkaline-earth metals, aluminum borides and compounds of boron and the nonmetals C, Si, Ge, N, P, As, O, S and Se. They, however, excluded the described here icosahedron-based rare-earth borides. Note that rare-earth elements have d- and f-electrons that complicates chemical and physical properties of their borides. Werheit et al. reviewed Raman spectra of numerous icosahedron-based boron compounds.
Figure 2 shows a relationship between the ionic radius of trivalent rare-earth ions and the composition of some rare-earth borides. Note that scandium has many unique boron compounds, as shown in figure 2, because of the much smaller ionic radius compared with other rare-earth elements.
In understanding the crystal structures of rare-earth borides, it is important to keep in mind the concept of partial site occupancy, that is, some atoms in the described below unit cells can take several possible positions with a given statistical probability. Thus, with the given statistical probability, some of the partial-occupancy sites in such a unit cell are empty, and the remained sites are occupied. | 0 | Theoretical and Fundamental Chemistry |
Lanthanum hydroxide can be obtained by adding an alkali such as ammonia to aqueous solutions of lanthanum salts such as lanthanum nitrate. This produces a gel-like precipitate that can then be dried in air.
Alternatively, it can be produced by hydration reaction (addition of water) to lanthanum oxide. | 0 | Theoretical and Fundamental Chemistry |
In July 2007, officials of the People's Republic of China seized US-produced pork for containing ractopamine residues. Further shipments of Canadian ractopamine-fed pork were seized in September 2007.
In June 2019, customs inspectors in China detected ractopamine in a shipment of Canadian pork products destined for Chinese consumption. The Chinese government thereupon suspended not only pork, but also beef imports from Canada. Canadian Agriculture Minister Marie-Claude Bibeau stated that the CRFPCP certificate was a forgery and called in the RCMP, while Canadian Public Safety Minister Ralph Goodale stressed that the federal government would vigorously defend Canadian meat producers. It was also revealed that the Canadian Cattlemen's Association said in a statement that "We are fully confident in our meat production systems in Canada and the safeguards we have in place." Meanwhile, holes were found in the CRFPCP programme because the meat packer at the centre of the controversy was a chilled butcher shop only.<what> It was disclosed on 3 July that the Chinese authorities had discovered 188 falsified CRFPCP certificates. | 0 | Theoretical and Fundamental Chemistry |
Similarly to drugs, manufacturers of medical devices in the United States are required to conduct clinical trials for premarket approval. Device trials may compare a new device to an established therapy, or may compare similar devices to each other. An example of the former in the field of vascular surgery is the Open versus Endovascular Repair (OVER trial) for the treatment of abdominal aortic aneurysm, which compared the older open aortic repair technique to the newer endovascular aneurysm repair device. An example of the latter are clinical trials on mechanical devices used in the management of adult female urinary incontinence. | 1 | Applied and Interdisciplinary Chemistry |
A glide plane is a reflection in a plane, followed by a translation parallel with that plane. This is noted by , , or , depending on which axis the glide is along. There is also the glide, which is a glide along the half of a diagonal of a face, and the glide, which is a fourth of the way along either a face or space diagonal of the unit cell. The latter is called the diamond glide plane as it features in the diamond structure. In 17 space groups, due to the centering of the cell, the glides occur in two perpendicular directions simultaneously, i.e. the same glide plane can be called b or c, a or b, a or c. For example, group Abm2 could be also called Acm2, group Ccca could be called Cccb. In 1992, it was suggested to use symbol e for such planes. The symbols for five space groups have been modified: | 0 | Theoretical and Fundamental Chemistry |
In mining, tailings or tails are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different from overburden, which is the waste rock or other material that overlies an ore or mineral body and is displaced during mining without being processed.
The extraction of minerals from ore can be done two ways: placer mining, which uses water and gravity to concentrate the valuable minerals, or hard rock mining, which pulverizes the rock containing the ore and then relies on chemical reactions to concentrate the sought-after material. In the latter, the extraction of minerals from ore requires comminution, i.e., grinding the ore into fine particles to facilitate extraction of the target element(s). Because of this comminution, tailings consist of a slurry of fine particles, ranging from the size of a grain of sand to a few micrometres. Mine tailings are usually produced from the mill in slurry form, which is a mixture of fine mineral particles and water.
Tailings are likely to be dangerous sources of toxic chemicals such as heavy metals, sulfides and radioactive content. These chemicals are especially dangerous when stored in water in ponds behind tailings dams. These ponds are also vulnerable to major breaches or leaks from the dams, causing environmental disasters, such as the Mount Polley disaster in British Columbia. Because of these and other environmental concerns such as groundwater leakage, toxic emissions and bird death, tailing piles and ponds have received more scrutiny, especially in first world countries, but the first UN-level standard for tailing management was only established 2020.
There are a wide range of methods for recovering economic value, containing or otherwise mitigating the impacts of tailings. However, internationally, these practices are poor, sometimes violating human rights. | 1 | Applied and Interdisciplinary Chemistry |
Kennedy J. P. Orton (1872 - 1930) was a British chemist. Initially he studied medicine at St. Thomas Hospital, but there he became interested in chemistry and moved to St. Johns College, Cambridge. He then obtained a Ph.D. summa cum laude in Heidelberg under Karl von Auwers, before working for a year with Sir William Ramsey at University College, London. He was then lecturer and demonstrator of Chemistry at St. Bartholomew's Hospital, before in 1903 being appointed Professor of Chemistry at University College of North Wales, Bangor, where he headed the department until his death. He was elected a Fellow of the Royal Society in 1921.
Besides being a chemist, he was a keen climber and ornithologist, and a biannual ornithological lecture was endowed in his name. | 0 | Theoretical and Fundamental Chemistry |
A protein is predicted to be "druggable" if it is a member of a protein family for which other members of the family are known to be targeted by drugs (i.e., "guilt" by association). While this is a useful approximation of druggability, this definition has limitations for two main reasons: (1) it highlights only historically successful proteins, ignoring the possibility of a perfectly druggable, but yet undrugged protein family; and (2) assumes that all protein family members are equally druggable. | 1 | Applied and Interdisciplinary Chemistry |
Miura et al. reported the cross coupling of vinyl bromides with an alkenyl carboxylic acid using a palladium catalyst. Some of the conjugated dienes prepared were reported to exhibit solid state fluorescence. | 0 | Theoretical and Fundamental Chemistry |
Calcium (Ca) deficiency is a plant disorder that can be caused by insufficient level of biologically available calcium in the growing medium, but is more frequently a product of low transpiration of the whole plant or more commonly the affected tissue. Plants are susceptible to such localized calcium deficiencies in low or non-transpiring tissues because calcium is not transported in the phloem. This may be due to water shortages, which slow the transportation of calcium to the plant, poor uptake of calcium through the stem, or too much nitrogen in the soil. | 1 | Applied and Interdisciplinary Chemistry |
In the pharmaceutical industry, ICP-MS is used for detecting inorganic impurities in pharmaceuticals and their ingredients. New and reduced maximum permitted exposure levels of heavy metals from dietary supplements, introduced in USP (United States Pharmacopeia) «〈232〉Elemental Impurities—Limits» and USP «〈232〉Elemental Impurities—Procedures», will increase the need for ICP-MS technology, where, previously, other analytic methods have been sufficient.
Cosmetics, such as lipstick, recovered from a crime scene may provide valuable forensic information. Lipstick smears left on cigarette butts, glassware, clothing, bedding; napkins, paper, etc. may be valuable evidence. Lipstick recovered from clothing or skin may also indicate physical contact between individuals. Forensic analysis of recovered lipstick smear evidence can provide valuable information on the recent activities of a victim or suspect. Trace elemental analysis of lipstick smears could be used to complement existing visual comparative procedures to determine the lipstick brand and color.
Single Particle Inductively Coupled Plasma Mass Spectroscopy (SP ICP-MS) was designed for particle suspensions in 2000 by Claude Degueldre. He first tested this new methodology at the Forel Institute of the University of Geneva and presented this new analytical approach at the Colloid 2oo2 symposium during the spring 2002 meeting of the EMRS, and in the proceedings in 2003. This study presents the theory of SP ICP-MS and the results of tests carried out on clay particles (montmorillonite) as well as other suspensions of colloids. This method was then tested on thorium dioxide nanoparticles by Degueldre & Favarger (2004), zirconium dioxide by Degueldre et al (2004) and gold nanoparticles, which are used as a substrate in nanopharmacy, and published by Degueldre et al (2006). Subsequently, the study of uranium dioxide nano- and micro-particles gave rise to a detailed publication, Ref. Degueldre et al (2006). Since 2010 the interest for SP ICP-MS has exploded.
Previous forensic techniques employed for the organic analysis of lipsticks by compositional comparison include thin layer chromatography (TLC), gas chromatography (GC), and high-performance liquid chromatography (HPLC). These methods provide useful information regarding the identification of lipsticks. However, they all require long sample preparation times and destroy the sample. Nondestructive techniques for the forensic analysis of lipstick smears include UV fluorescence observation combined with purge-and-trap gas chromatography, microspectrophotometry and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and Raman spectroscopy. | 0 | Theoretical and Fundamental Chemistry |
Motor proteins are a class of molecular motors that can move along the cytoskeleton of cells. They convert chemical energy into mechanical work by the hydrolysis of ATP. Flagellar rotation, however, is powered by a proton pump. | 0 | Theoretical and Fundamental Chemistry |
S. cerevisiae (yeast) can stably exist as either a diploid or a haploid. Both haploid and diploid yeast cells reproduce by mitosis, with daughter cells budding from mother cells. Haploid cells are capable of mating with other haploid cells of the opposite mating type (an a cell can only mate with an α cell, and vice versa) to produce a stable diploid cell. Diploid cells, usually upon facing stressful conditions such as nutrient depletion, can undergo meiosis to produce four haploid spores: two a spores and two α spores. | 1 | Applied and Interdisciplinary Chemistry |
In the physics of superfluidity, a boojum is a geometric pattern on the surface of one of the phases of superfluid helium-3, whose motion can result in the decay of a supercurrent. A boojum can result from a monopole singularity in the bulk of the liquid being drawn to, and then "pinned" on a surface. Although superfluid helium-3 only exists within a few thousandths of a degree of absolute zero, boojums have also been observed forming in various liquid crystals, which exist at a far broader range of temperatures.
The boojum was named by N. David Mermin of Cornell University in 1976. He was inspired by Lewis Carrolls poem The Hunting of the Snark. As in the poem, the appearance of a boojum can cause something (in this case, the supercurrent) to "softly and suddenly vanish away". Other, less whimsical names had already been suggested for the phenomenon, but Mermin was persistent. After an exchange of letters that Mermin describes as both "lengthy and hilarious", the editors of Physical Review Letters' agreed to his terminology. Research using the term "boojum" in a superfluid context was first published in 1977, and the term has since gained widespread acceptance in broader areas of physics. Its Russian phonetic equivalent is "budzhum", which is also well accepted by physicists.
The plural of the term is "boojums", a word initially disliked by Mermin (who at first used "booja") but one which is defined unambiguously by Carroll in his poem. | 1 | Applied and Interdisciplinary Chemistry |
Limulus amebocyte lysate (LAL) is an aqueous extract of motile blood cells (amebocytes) from the Atlantic horseshoe crab Limulus polyphemus. LAL reacts with bacterial endotoxins such as lipopolysaccharides (LPS), which are components of the bacterial capsule, the outermost membrane of cell envelope of gram-negative bacteria. This reaction is the basis of the LAL test, which is widely used for the detection and quantification of bacterial endotoxins.
In Asia, a similar Tachypleus amebocyte lysate (TAL) test based on the local horseshoe crabs Tachypleus gigas or Tachypleus tridentatus is occasionally used instead. The recombinant factor C (rFC) assay is a replacement of LAL and TAL based on a similar reaction. | 0 | Theoretical and Fundamental Chemistry |
A general sigmatropic rearrangement can be classified as order [i,j], meaning that a σ bond originally between atoms denoted 1 and 1, adjacent to one or more π systems, is shifted to between atoms i and j. Thus it migrates (i − 1), (j' − 1) atoms away from its original position.
A formal symmetry analysis via correlation diagrams is of no use in the study of sigmatropic rearrangements as there are, in general, only symmetry elements present in the transition state. Except in special cases (e.g. [3,3]-rearrangements), there are no symmetry elements that are conserved as the reaction coordinate is traversed. Nevertheless, orbital correlations between starting materials and products can still be analyzed, and correlations of starting material orbitals with high energy product orbitals will, as usual, result in "symmetry-forbidden" processes. However, an FMO based approach (or the Dewar-Zimmerman analysis) is more straightforward to apply.
One of the most prevalent classes of sigmatropic shifts is classified as [1,j], where j is odd. That means one terminus of the σ-bond migrates (j − 1) bonds away across a π-system while the other terminus does not migrate. It is a reaction involving j + 1 electrons: j − 1 from the π-system and 2 from σ-bond. Using FMO analysis, [1,j]-sigmatropic rearrangements are allowed if the transition state has constructive overlap between the migrating group and the accepting p orbital of the HOMO. In [1,j]-sigmatropic rearrangements if j + 1 = 4n, then supra/antara is thermally allowed, and if j + 1 = 4n + 2, then supra/supra or antara/antara is thermally allowed.
The other prevalent class of sigmatropic rearrangements are [3,3], notably the Cope and Claisen rearrangements. Here, the constructive interactions must be between the HOMOs of the two allyl radical fragments in the transition state. The ground state HOMO Ψ of the allyl fragment is shown below. As the terminal p-orbitals are of opposite sign, this reaction can either take place in a supra/supra topology, or an antara/antara topology.
The selection rules for an [i,j]-sigmatropic rearrangement are as follows:
* For supra/supra or antara/antara [i,j]-sigmatropic shifts, if i + j = 4n + 2 they are thermally allowed and if i + j = 4n they are photochemically allowed
* For supra/antara [i,j]-sigmatropic shifts, if i + j = 4n they are thermally allowed, and if i + j = 4n + 2 they are photochemically allowed
This is summarized in the following table: | 0 | Theoretical and Fundamental Chemistry |
In 1988, climatologist Stephen Schneider organised a conference of the American Geophysical Union. The first Chapman Conference on Gaia, was held in San Diego, California on March 7, 1988.
During the "philosophical foundations" session of the conference, David Abram spoke on the influence of metaphor in science, and of the Gaia hypothesis as offering a new and potentially game-changing metaphorics, while James Kirchner criticised the Gaia hypothesis for its imprecision. Kirchner claimed that Lovelock and Margulis had not presented one Gaia hypothesis, but four:
* CoEvolutionary Gaia: that life and the environment had evolved in a coupled way. Kirchner claimed that this was already accepted scientifically and was not new.
* Homeostatic Gaia: that life maintained the stability of the natural environment, and that this stability enabled life to continue to exist.
* Geophysical Gaia: that the Gaia hypothesis generated interest in geophysical cycles and therefore led to interesting new research in terrestrial geophysical dynamics.
* Optimising Gaia: that Gaia shaped the planet in a way that made it an optimal environment for life as a whole. Kirchner claimed that this was not testable and therefore was not scientific.
Of Homeostatic Gaia, Kirchner recognised two alternatives. "Weak Gaia" asserted that life tends to make the environment stable for the flourishing of all life. "Strong Gaia" according to Kirchner, asserted that life tends to make the environment stable, to enable the flourishing of all life. Strong Gaia, Kirchner claimed, was untestable and therefore not scientific.
Lovelock and other Gaia-supporting scientists, however, did attempt to disprove the claim that the hypothesis is not scientific because it is impossible to test it by controlled experiment. For example, against the charge that Gaia was teleological, Lovelock and Andrew Watson offered the Daisyworld Model (and its modifications, above) as evidence against most of these criticisms. Lovelock said that the Daisyworld model "demonstrates that self-regulation of the global environment can emerge from competition amongst types of life altering their local environment in different ways".
Lovelock was careful to present a version of the Gaia hypothesis that had no claim that Gaia intentionally or consciously maintained the complex balance in her environment that life needed to survive. It would appear that the claim that Gaia acts "intentionally" was a statement in his popular initial book and was not meant to be taken literally. This new statement of the Gaia hypothesis was more acceptable to the scientific community. Most accusations of teleologism ceased, following this conference. | 0 | Theoretical and Fundamental Chemistry |
The young Rutherford made his grandmother a wooden potato masher, which was believed to have been made during the school holidays. It has been held in the collection of the Royal Society since 1888.
In 1900, Rutherford married Mary Georgina Newton (1876–1954), to whom he had become engaged before leaving New Zealand, at St Pauls Anglican Church, Papanui in Christchurch. They had one daughter, Eileen Mary (1901–1930), who married the physicist Ralph Fowler. Rutherfords hobbies included golf and motoring.
For some time before his death, Rutherford had a small hernia, which he neglected to have fixed, and it became strangulated, rendering him violently ill. Despite an emergency operation in London, he died four days afterwards, at Cambridge on 19 October 1937 at age 66, of what physicians termed "intestinal paralysis". After cremation at Golders Green Crematorium, he was given the high honour of burial in Westminster Abbey, near Isaac Newton and other illustrious British scientists such as Charles Darwin. | 1 | Applied and Interdisciplinary Chemistry |
Liming is the application of calcium- (Ca) and magnesium (Mg)-rich materials in various forms, including marl, chalk, limestone, burnt lime or hydrated lime to soil. In acid soils, these materials react as a base and neutralize soil acidity. This often improves plant growth and increases the activity of soil bacteria, but oversupply may result in harm to plant life. Modern liming was preceded by marling, a process of spreading raw chalk and lime debris across soil, in an attempt to modify pH or aggregate size. Evidence of these practices dates to the 1200's and the earliest examples are taken from the modern British Isles. | 0 | Theoretical and Fundamental Chemistry |
In the U.S. MTBE has been used in gasoline at low levels since 1979, replacing tetraethyllead (TEL) as an antiknock (octane rating) additive to prevent engine knocking. Oxygenates also help gasoline burn more completely, reducing tailpipe emissions. Oxygenates also dilute or displace gasoline components such as aromatics (e.g., benzene). Before the introduction of other oxygenates and octane enhancers, refiners chose MTBE for its blending characteristics and low cost. | 1 | Applied and Interdisciplinary Chemistry |
Exposure assessment is a branch of environmental science and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. These are the final steps in the path to release an environmental contaminant, through transport to its effect in a biological system. It tries to measure how much of a contaminant can be absorbed by an exposed target organism, in what form, at what rate and how much of the absorbed amount is actually available to produce a biological effect. Although the same general concepts apply to other organisms, the overwhelming majority of applications of exposure assessment are concerned with human health, making it an important tool in public health. | 1 | Applied and Interdisciplinary Chemistry |
Hexafluoroethane is used as a versatile etchant in semiconductor manufacturing. It can be used for selective etching of metal silicides and oxides versus their metal substrates and also for etching of silicon dioxide over silicon. The primary aluminium and the semiconductor manufacturing industries are the major emitters of hexafluoroethane using the Hall-Héroult process.
Together with trifluoromethane it is used in refrigerants R508A (61%) and R508B (54%).
It is used as a tamponade to assist in retinal reattachment following vitreoretinal surgery. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, annulation (; occasionally annelation) is a chemical reaction in which a new ring is constructed on a molecule.
Examples are the Robinson annulation, Danheiser annulation and certain cycloadditions. Annular molecules are constructed from side-on condensed cyclic segments, for example helicenes and acenes. In transannulation a bicyclic molecule is created by intramolecular carbon-carbon bond formation in a large monocyclic ring. An example is the samarium(II) iodide induced ketone - alkene cyclization of 5-methylenecyclooctanone which proceeds through a ketyl intermediate: | 0 | Theoretical and Fundamental Chemistry |
List adapted from, Figure 1.
*Phylum Chlorobiota ("green sulfur bacteria"), in full. Example genera:
** Chlorobium
** Pelodictyon
** Prostecochloris
*Phylum Chloroflexota, class Chloroflexia ("green non-sulfur bacteria"), suborder Chloroflexineae, in full.
** Family Chloroflexineae. Example genera:
*** Chloroflexus
*** Chloronema
** Family Oscillochloridaceae. Example genera:
*** Oscillochloris
* Species Chloracidobacterium thermophilum. This is the only Acidobacterium known to make a chlorosome. (Proposed in 2021 to be split into three species of different temperature preference by sequence similarity.) | 0 | Theoretical and Fundamental Chemistry |
AR3 is expressed by Halorubrum sodomense. The organism was first identified in the Dead Sea in 1980 and requires a higher concentration of Mg ions for growth than related halophiles. The aop3 gene was cloned by Ihara and colleagues at Nagoya University in 1999 and the protein was found to share 59% sequence identity with bacteriorhodopsin. The crystal structure of AR3 was solved by Anthony Watts at Oxford University and Isabel Moraes at the National Physical Laboratory, together with collaborators at Diamond Light Source.
Mutants of Archaerhodopsin-3 (AR3) are widely used as tools in optogenetics for neuroscience research.
AR3 has recently been introduced as a fluorescent voltage sensor. | 0 | Theoretical and Fundamental Chemistry |
Several research have used TERS to image single atoms and the internal structure of the molecules. In 2019, the Ara Apkarian group at the Center for Chemistry at the Space-Time Limit, University of California, Irvine imaged vibrational normal modes of single porphyrin molecules using TERS. TERS-based DNA sequencing has also been demonstrated. | 0 | Theoretical and Fundamental Chemistry |
Because of the complementary nature of base-pairing between nucleic acid polymers, a double-stranded DNA molecule will be composed of two strands with sequences that are reverse complements of each other. To help molecular biologists specifically identify each strand individually, the two strands are usually differentiated as the "sense" strand and the "antisense" strand. An individual strand of DNA is referred to as positive-sense (also positive (+) or simply sense) if its nucleotide sequence corresponds directly to the sequence of an RNA transcript which is translated or translatable into a sequence of amino acids (provided that any thymine bases in the DNA sequence are replaced with uracil bases in the RNA sequence). The other strand of the double-stranded DNA molecule is referred to as negative-sense (also negative (−) or antisense), and is reverse complementary to both the positive-sense strand and the RNA transcript. It is actually the antisense strand that is used as the template from which RNA polymerases construct the RNA transcript, but the complementary base-pairing by which nucleic acid polymerization occurs means that the sequence of the RNA transcript will look identical to the positive-sense strand, apart from the RNA transcript's use of uracil instead of thymine.
Sometimes the phrases coding strand and template strand are encountered in place of sense and antisense, respectively, and in the context of a double-stranded DNA molecule the usage of these terms is essentially equivalent. However, the coding/sense strand need not always contain a code that is used to make a protein; both protein-coding and non-coding RNAs may be transcribed.
The terms "sense" and "antisense" are relative only to the particular RNA transcript in question, and not to the DNA strand as a whole. In other words, either DNA strand can serve as the sense or antisense strand. Most organisms with sufficiently large genomes make use of both strands, with each strand functioning as the template strand for different RNA transcripts in different places along the same DNA molecule. In some cases, RNA transcripts can be transcribed in both directions (i.e. on either strand) from a common promoter region, or be transcribed from within introns on either strand (see "ambisense" below). | 1 | Applied and Interdisciplinary Chemistry |
Metal acyls are often generated by the reaction of low-valent metal centers with acyl chlorides. Illustrative is the oxidative addition of acetyl chloride to Vaska's complex, converting square planar Ir(I) to octahedral Ir(III):
:IrCl(CO)(PPh) + CHCOCl → CHCOIrCl(CO)(PPh)
In rare cases, acyls can be produced from aldehydes by C-H oxidative addition. This reaction underpins hydroacylation.
In a related reaction, metal carbonyl anions are acylated by acyl chlorides:
:(CH)Fe(CO)Na + CHC(O)Cl → (CH)Fe(CO)COCH + NaCl
Another important route to metal acyls entails insertion of CO into a metal alkyl bond. In this pathway, the alkyl ligand migrates to an adjacent CO ligand. This reaction is a step in the hydroformylation process.
Coordinatively saturated metal carbonyls react with organolithium reagents to give acyls. This reaction proceeds by attack of the alkyl nucleophile on the electrophilic CO ligand. | 0 | Theoretical and Fundamental Chemistry |
A variety of transformations have been developed to facilitate removal of the oxazolidinone auxiliary to generate different synthetically useful functional groups. | 0 | Theoretical and Fundamental Chemistry |
Denigés' reagent is used to detect isolefin or tertiary alcohols which can be easily dehydrated to form isoolefin in the presence of acid. Treatment of solutions containing either isolefin or tertiary alcohols with this reagent will result in the formation of a solid yellow or red precipitate. | 0 | Theoretical and Fundamental Chemistry |
Sigma B was the first anti-sigma factor identified in a bacterium. It is found in Bacillus subtilis and other similar bacteria. Sigma B is a stress response factor that plays a role in survival and against destruction that could be caused by other organisms such as mammals. General stress responses that are controlled by Sigma B are stimulated by things like temperature, salt concentration, energy depletion, etc. Once activated, Sigma B binds to the RNAP and recognizes a promoter, causing inhibition of the stimuli. Because Sigma B orthologs are conserved in various gram-positive bacteria, this anti-sigma factor plays an essential role in the evolution of different bacteria and their ability to respond to stressing factors. Scientist have found that the anti- sigma factor, Sigma B controls more than 150 genes that are influential in stress response. | 1 | Applied and Interdisciplinary Chemistry |
While cerium anomalies in coal are usually negative, they can rarely be positive as well. This can occur during volcanic eruptions when volcanic ash is weathered into mafic tuffs with positive Ce-anomalies. The Pavlovka deposit in Far East Russia has large positive Ce-anomalies in its Fe-Mn oxyhydroxide ores. Because cerium is one of only two REEs that can obtain an oxidation number of +4, Ce is absorbed into Mn(IV) oxides instead of other REEs and this results in a positive Ce-anomaly. | 0 | Theoretical and Fundamental Chemistry |
Since warming of Earth means less ice on the ground on average, it would cause lower albedo and more sunlight absorbed, hence further increasing Earth's temperature.
As a rough estimate, we note that the average temperature on most of Earth are between -20 and +30 Celsius degree, a good guess will be that 2% of its surface are between -1 and 0 °C, and thus an equivalent area of its surface will be changed from ice-covered (or snow-covered) to either ocean or forest.
For comparison, in the northern hemisphere, the arctic sea ice has shrunk between 1979 and 2015 by 1.43x10 m at maxima and 2.52x10 m at minima, for an average of almost 2x10 m, which is 0.4% of Earth's total surface of 510x10 m. At this time the global temperature rose by ~0.6 °C. The areas of inland glaciers combined (not including the antarctice ice sheet), the antarctic sea ice, and the arctic sea ice are all comparable, so one may expect the change in ice of the arctic sea ice is roughly a third of the total change, giving 1.2% of the Earth surface turned from ice to ocean or bare ground per 0.6 °C, or equivalently 2% per 1 °C. The antarctic ice cap size oscillates, and it is hard to predict its future course, with factors such as relative thermal insulated and constraints due to the Antarctic Circumpolar Current probably playing a part.
As the difference in albedo between ice and e.g. ocean is around 2/3, this means that due to a 1 °C rise, the albedo will drop by 2%*2/3 = 4/3%. However this will mainly happen in northern and southern latitudes, around 60 degrees off the equator, and so the effective area is actually 2% * cos(60) = 1%, and the global albedo drop would be 2/3%.
Since a change in radiation of 1.3% causes a direct change of 1 degree Celsius (without feedback), as calculated above, and this causes another change of 2/3% in radiation due to positive feedback, whice is half the original change, this means the total factor caused by this feedback mechanism would be:
Thus, this feedback would double the effect of the change in radiation, causing a change of ~ 2 K in the global temperature, which is indeed the commonly accepted short-term value. For long-term value, including further feedback mechanisms, ~3K is considered more probable. | 1 | Applied and Interdisciplinary Chemistry |
A screw axis is a rotation about an axis, followed by a translation along the direction of the axis. These are noted by a number, n, to describe the degree of rotation, where the number is how many operations must be applied to complete a full rotation (e.g., 3 would mean a rotation one third of the way around the axis each time). The degree of translation is then added as a subscript showing how far along the axis the translation is, as a portion of the parallel lattice vector. So, 2 is a twofold rotation followed by a translation of 1/2 of the lattice vector. | 0 | Theoretical and Fundamental Chemistry |
Diphenylchloroarsine (DA) is the organoarsenic compound with the formula (CH)AsCl. It is highly toxic and was once used in chemical warfare. It is also an intermediate in the preparation of other organoarsenic compounds. The molecule consists of a pyramidal As(III) center attached to two phenyl rings and one chloride. It was also known as sneezing oil during World War I by the Allies. | 1 | Applied and Interdisciplinary Chemistry |
The idea that there must be specific transport proteins associated with the uptake of monoamines and acetylcholine into vesicles developed due to the discovery of specific inhibitors which interfered with monoamine neurotransmission and also depleted monoamines in neuroendocrine tissues. VMAT1 and VMAT2 were first identified in rats upon cloning cDNAs for proteins which gave non-amine accumulating recipient cells the ability to sequester monoamines. Subsequently, human VMATs were cloned using human cDNA libraries with the rat homologs as probes, and heterologous-cell amine uptake assays were performed to verify transport properties. | 1 | Applied and Interdisciplinary Chemistry |
Creation of the oligonucleotides requires only two pieces of essential information: the primer sequences used and the location and details of any modifications made to the sequence. But there are several desirable pieces of data, including the identification number from the RTPrimerDB database, the sequences from the probes, the manufacturer used to make the oligos, and how they were purified. | 1 | Applied and Interdisciplinary Chemistry |
Protein-RNA interactions may prevent or stabilize the formation of an anti-terminator structure. .. karima eric discovery | 1 | Applied and Interdisciplinary Chemistry |
Reactive nitrogen ("Nr"), also known as fixed nitrogen, refers to all forms of nitrogen present in the environment except for molecular nitrogen (). While nitrogen is an essential element for life on Earth, molecular nitrogen is comparatively unreactive, and must be converted to other chemical forms via nitrogen fixation before it can be used for growth. Common Nr species include nitrogen oxides (), ammonia (), nitrous oxide (), as well as the anion nitrate ().
Biologically, nitrogen is "fixed" mainly by the microbes (eg., Bacteria and Archaea) of the soil that fix into mainly but also other species. Legumes, a type of plant in the Fabacae family, are symbionts to some of these microbes that fix . is a building block to Amino acids and proteins amongst other things essential for life. However, just over half of all reactive nitrogen entering the biosphere is attributable to anthropogenic activity such as industrial fertilizer production. While reactive nitrogen is eventually converted back into molecular nitrogen via denitrification, an excess of reactive nitrogen can lead to problems such as eutrophication in marine ecosystems. | 1 | Applied and Interdisciplinary Chemistry |
Prior to the formation of the lactate shuttle hypothesis, lactate had long been considered a byproduct resulting from glucose breakdown through glycolysis in times of anaerobic metabolism. As a means of regenerating oxidized NAD, lactate dehydrogenase catalyzes the conversion of pyruvate to lactate in the cytosol, oxidizing NADH to NAD, regenerating the necessary substrate needed to continue glycolysis. Lactate is then transported from the peripheral tissues to the liver by means of the Cori Cycle where it is reformed into pyruvate through the reverse reaction using lactate dehydrogenase. By this logic, lactate was traditionally considered a toxic metabolic byproduct that could give rise to fatigue and muscle pain during times of anaerobic respiration. Lactate was essentially payment for ‘oxygen debt’ defined by Hill and Lupton as the ‘total amount of oxygen used, after cessation of exercise in recovery therefrom’. | 1 | Applied and Interdisciplinary Chemistry |
The following is a list of consumer medicines that either contain pseudoephedrine or have switched to a less-regulated alternative such as phenylephrine.
*Actifed (made by GlaxoSmithKline) — contains 60 mg pseudoephedrine and 2.5 mg triprolidine in certain countries.
*Advil Cold & Sinus (made by Pfizer Canada Inc.) — contains 30 mg pseudoephedrine hydrochloride and 200 mg ibuprofen.
*Aleve-D Sinus & Cold (made by Bayer Healthcare) — contains 120 mg pseudoephedrine hydrochloride (also 220 mg naproxen).
*Allegra-D (made by Sanofi Aventis) — contains 120 mg of pseudoephedrine hydrochloride (also 60 mg of fexofenadine).
*Allerclear-D (made by Kirkland Signature) — contains 240 mg of pseudoephedrine sulfate (also 10 mg of loratadine).
*Benadryl Allergy Relief Plus Decongestant (made by McNeil Consumer Healthcare, a Johnson & Johnson company) — contains 60 mg pseudoephedrine hydrochloride (also 8 mg acrivastine)
*Cirrus (made by UCB) — contains 120 mg pseudoephedrine hydrochloride (also 5 mg cetirizine).
*Claritin-D (made by Bayer Healthcare) — contains 120 mg of pseudoephedrine sulfate (also 5 mg of loratadine).
*Claritin-D 24 Hour (made by Bayer Healthcare) — contains 240 mg of pseudoephedrine sulfate (also 10 mg of loratadine).
*Codral (made by Asia-Pacific subsidiary of Johnson & Johnson) — Codral Original contains pseudoephedrine, Codral New Formula substitutes phenylephrine for pseudoephedrine.
*Congestal (made by SIGMA Pharmaceutical Industries) — contains 60 mg pseudoephedrine hydrochloride (also 650 mg paracetamol and 4 mg chlorpheniramine).
*Contac (made by GlaxoSmithKline) — previously contained pseudoephedrine, now contains phenylephrine. As at Nov 2014 UK version still contains 30 mg pseudoephedrine hydrochloride per tablet.
*Demazin (made by Bayer Healthcare) — contains pseudoephedrine sulfate and chlorpheniramine maleate
*Eltor (made by Sanofi Aventis) — contains pseudoephedrine hydrochloride.
*Mucinex D (made by Reckitt Benckiser) — contains 60 mg pseudoephedrine hydrochloride (also 1200 mg guaifenesin).
*Nexafed (made by Acura Pharmaceuticals) — contains 30 mg pseudoephedrine per tablet, formulated with Impede Meth-Deterrent technology.
*Nurofen Cold & Flu (made by Reckitt Benckiser) — contains 30 mg pseudoephedrine hydrochloride (also 200 mg ibuprofen).
*Respidina – contains 120 mg of pseudoephedrine in the form of extended release tablets.
*Rhinex Flash (made by Pharma Product Manufacturing, Cambodia) — contains pseudoephedrine combined with paracetamol and triprolidine.
*Rhinos SR (made by Dexa Medica) — contains 120 mg of pseudoephedrine hydrochloride
* Sinutab (made by McNeil Consumer Healthcare, a Johnson & Johnson company) — contains 500 mg paracetamol and 30 mg pseudoephedrine hydrochloride.
* Sudafed Decongestant (made by McNeil Consumer Healthcare, a Johnson & Johnson company) — contains 60 mg of pseudoephedrine hydrochloride. Not to be confused with Sudafed PE, which contains phenylephrine.
* Theraflu (made by Novartis) — previously contained pseudoephedrine, now contains phenylephrine
* Trima — contains 60 mg pseudoephedrine hydrochloride
* Tylol Hot (made by NOBEL İLAÇ SANAYİİ VE TİCARET A.Ş., Turkey) — a packet of 20 g contains 60 mg pseudoephedrine hydrochloride, 500 mg paracetamol and 4 mg chlorpheniramine maleate
* Unifed (made by United Pharmaceutical Manufacturer, Jordan) — contains pseudoephedrine hydrochloride (also triprolidine and guaifenesin).
*Zyrtec-D 12 Hour (made by McNeil Consumer Healthcare, a Johnson & Johnson company) — contains 120 mg pseudoephedrine hydrochloride (also 5 mg of cetirizine).
*Zephrex-D (made by Westport Pharmaceuticals) – a special meth-resistant form of pseudoephedrine that becomes gooey when heated. | 0 | Theoretical and Fundamental Chemistry |
Dipole-dipole interactions are electrostatic interactions between permanent dipoles in molecules. These interactions tend to align the molecules to increase attraction (reducing potential energy). Normally, dipoles are associated with electronegative atoms, including oxygen, nitrogen, sulfur, and fluorine.
For example, acetone, the active ingredient in some nail polish removers, has a net dipole associated with the carbonyl (see figure 2). Since oxygen is more electronegative than the carbon that is covalently bonded to it, the electrons associated with that bond will be closer to the oxygen than the carbon, creating a partial negative charge (δ) on the oxygen, and a partial positive charge (δ) on the carbon. They are not full charges because the electrons are still shared through a covalent bond between the oxygen and carbon. If the electrons were no longer being shared, then the oxygen-carbon bond would be an electrostatic interaction.
Often molecules contain dipolar groups, but have no overall dipole moment. This occurs if there is symmetry within the molecule that causes the dipoles to cancel each other out. This occurs in molecules such as tetrachloromethane. Note that the dipole-dipole interaction between two individual atoms is usually zero, since atoms rarely carry a permanent dipole. See atomic dipoles. | 0 | Theoretical and Fundamental Chemistry |
The candidate division SR1 and gracilibacteria code (translation table 25) is used in two groups of (so far) uncultivated bacteria found in marine and fresh-water environments and in the intestines and oral cavities of mammals among others. The difference to the standard and the bacterial code is that UGA represents an additional glycine codon and does not code for termination. | 1 | Applied and Interdisciplinary Chemistry |
Yeast matches bacterial cells' cost-effectiveness, efficiency and technical feasibility. Moreover, yeast secretes soluble proteins and has the ability to perform post-translational modifications similar to mammalian cells.
Notably, yeast incorporates more mannose molecules during N-glycosylation when compared with other eukaryotes, which may trigger cellular conformational stress responses. Such responses may result in failure in reaching native protein conformation, implying potential reduction of serum half-life and immunogenicity. Regarding application, both the hepatitis B virus surface antigen (HBsAg) and the virus-like particles (VLPs) of the major capsid protein L1 of human papillomavirus type 6, 11, 16, 18 are produced by Saccharomyces cerevisiae. | 1 | Applied and Interdisciplinary Chemistry |
In the late 1930s August Pfund used a triple-pass cell like the one shown above for atmospheric study. The cell, which became known as the Pfund cell, is constructed using two identical spherical mirrors, each having a hole carefully machined into its center. The separation distance between the mirrors is equal to the mirror focal length. A source enters from a hole in either mirror, is redirected twice at two reflection points, and then exits the cell through the other mirror on the third pass. The Pfund cell was one of the earliest examples of this type of spectroscopic technique and is noted for having used multiple passes. | 0 | Theoretical and Fundamental Chemistry |
Clumped isotopes analyses have traditionally been used in lieu of conventional δO analyses when the δO of seawater or source water is poorly constrained. While conventional δO analysis solves for temperature as a function of both carbonate and water δO, clumped isotope analyses can provide temperature estimates that are independent of the source water δO. Δ47-derived temperature can then be used in conjunction with carbonate δO to reconstruct δO of the source water, thus providing information on the water with which the carbonate was equilibrated.
Clumped isotope analyses thus allow for estimates of two key environmental variables: temperature and water δO. These variables are especially useful for reconstructing past climates, as they can provide information on a wide range of environmental properties. For example, temperature variability can imply changes in solar irradiance, greenhouse gas concentration, or albedo, while changes in water δO can be used to estimate changes in ice volume, sea level, or rainfall intensity and location.
Studies have used temperatures derived from clumped isotopes for varied and numerous paleoclimate applications — to constrain δO of past seawater, pinpoint the timing of icehouse-hothouse transitions, track changes in ice volume through an ice age, and to reconstruct temperature changes in ancient lake basins. | 0 | Theoretical and Fundamental Chemistry |
In geology, silicification is a petrification process in which silica-rich fluids seep into the voids of Earth materials, e.g., rocks, wood, bones, shells, and replace the original materials with silica (SiO). Silica is a naturally existing and abundant compound found in organic and inorganic materials, including Earth's crust and mantle. There are a variety of silicification mechanisms. In silicification of wood, silica permeates into and occupies cracks and voids in wood such as vessels and cell walls. The original organic matter is retained throughout the process and will gradually decay through time. In the silicification of carbonates, silica replaces carbonates by the same volume. Replacement is accomplished through the dissolution of original rock minerals and the precipitation of silica. This leads to a removal of original materials out of the system. Depending on the structures and composition of the original rock, silica might replace only specific mineral components of the rock. Silicic acid (HSiO) in the silica-enriched fluids forms lenticular, nodular, fibrous, or aggregated quartz, opal, or chalcedony that grows within the rock. Silicification happens when rocks or organic materials are in contact with silica-rich surface water, buried under sediments and susceptible to groundwater flow, or buried under volcanic ashes. Silicification is often associated with hydrothermal processes. Temperature for silicification ranges in various conditions: in burial or surface water conditions, temperature for silicification can be around 25°−50°; whereas temperatures for siliceous fluid inclusions can be up to 150°−190°. Silicification could occur during a syn-depositional or a post-depositional stage, commonly along layers marking changes in sedimentation such as unconformities or bedding planes. | 0 | Theoretical and Fundamental Chemistry |
Smear layer refers to a layer of debris on the inorganic surface of substrate which comprises residual inorganic and organic components. This layer is produced whenever the tooth structure undergoes a preparation with a bur.
Smear layer will fill the orifices of the dentinal tubules, hence forming smear plugs. These smear plugs decrease dentin permeability by 90% and the smear plug alone can prevent adhesive resin penetration into dentinal tubules. The thickness of smear layer can range from 0.5-2 µmeter and for the smear plug, 1 to 10 µmeter.
Smear layer poses some threat for optimal bonding to occur. That is why it needs to be removed. For example, smear layer needs to be removed prior to bonding by etch-and-rinse (total etch) adhesives. This will lead to thicker hybrid layer and long, denser resin tags which results in better bond strength. | 0 | Theoretical and Fundamental Chemistry |
The Darcy–Weisbach friction factor is 4 times larger than the Fanning friction factor , so attention must be paid to note which one of these is meant in any "friction factor" chart or equation being used. Of the two, the Darcy–Weisbach factor is more commonly used by civil and mechanical engineers, and the Fanning factor by chemical engineers, but care should be taken to identify the correct factor regardless of the source of the chart or formula.
Note that
Most charts or tables indicate the type of friction factor, or at least provide the formula for the friction factor with laminar flow. If the formula for laminar flow is , it is the Fanning factor , and if the formula for laminar flow is , it is the Darcy–Weisbach factor .
Which friction factor is plotted in a Moody diagram may be determined by inspection if the publisher did not include the formula described above:
#Observe the value of the friction factor for laminar flow at a Reynolds number of 1000.
#If the value of the friction factor is 0.064, then the Darcy friction factor is plotted in the Moody diagram. Note that the nonzero digits in 0.064 are the numerator in the formula for the laminar Darcy friction factor: .
#If the value of the friction factor is 0.016, then the Fanning friction factor is plotted in the Moody diagram. Note that the nonzero digits in 0.016 are the numerator in the formula for the laminar Fanning friction factor: .
The procedure above is similar for any available Reynolds number that is an integer power of ten. It is not necessary to remember the value 1000 for this procedure—only that an integer power of ten is of interest for this purpose. | 1 | Applied and Interdisciplinary Chemistry |
Further shell closures beyond the main island of stability in the vicinity of Z = 112–114 may give rise to additional islands of stability. Although predictions for the location of the next magic numbers vary considerably, two significant islands are thought to exist around heavier doubly magic nuclei; the first near 126 (with 228 neutrons) and the second near 164 or 164 (with 308 or 318 neutrons). Nuclides within these two islands of stability might be especially resistant to spontaneous fission and have alpha decay half-lives measurable in years, thus having comparable stability to elements in the vicinity of flerovium. Other regions of relative stability may also appear with weaker proton shell closures in beta-stable nuclides; such possibilities include regions near 126 and 154. Substantially greater electromagnetic repulsion between protons in such heavy nuclei may greatly reduce their stability, and possibly restrict their existence to localized islands in the vicinity of shell effects. This may have the consequence of isolating these islands from the main chart of nuclides, as intermediate nuclides and perhaps elements in a "sea of instability" would rapidly undergo fission and essentially be nonexistent. It is also possible that beyond a region of relative stability around element 126, heavier nuclei would lie beyond a fission threshold given by the liquid drop model and thus undergo fission with very short lifetimes, rendering them essentially nonexistent even in the vicinity of greater magic numbers.
It has also been posited that in the region beyond A > 300, an entire "continent of stability" consisting of a hypothetical phase of stable quark matter, comprising freely flowing up and down quarks rather than quarks bound into protons and neutrons, may exist. Such a form of matter is theorized to be a ground state of baryonic matter with a greater binding energy per baryon than nuclear matter, favoring the decay of nuclear matter beyond this mass threshold into quark matter. If this state of matter exists, it could possibly be synthesized in the same fusion reactions leading to normal superheavy nuclei, and would be stabilized against fission as a consequence of its stronger binding that is enough to overcome Coulomb repulsion. | 0 | Theoretical and Fundamental Chemistry |
Although MRM has been used extensively in metabolomics and proteomics, its high sensitivity and linear response over a wide dynamic range make it especially suited for glycan biomarker research and discovery. MRM is performed on a triple quadrupole (QqQ) instrument, which is set to detect a predetermined precursor ion in the first quadrupole, a fragmented in the collision quadrupole, and a predetermined fragment ion in the third quadrupole. It is a non-scanning technique, wherein each transition is detected individually and the detection of multiple transitions occurs concurrently in duty cycles. This technique is being used to characterize the immune glycome.
Table 1:Advantages and disadvantages of mass spectrometry in glycan analysis | 0 | Theoretical and Fundamental Chemistry |
Titanium's propensity to form an oxide layer on its surface prevents corrosion of surfaces that are in contact with human tissues because the surface oxides minimize diffusion of metal ions from the bulk material to the surface. When titanium gains a coating to make it more bioactive, it can turn the already biocompatible titanium surface into an interface able to enhance osteoblast adhesion and able to promote osseointegration. Today, research is heavily focused on improving the success rate of integration and uses an understanding of the natural process of bone growth and repair to create coatings that will enhance the surface finish and surface properties of the implant. These adjustments allow the artificial structure to mimic biological materials and to gain acceptance into the body with fewer negative side effects.
A 3-year clinical and radiographic study found implants in humans coated by nanocrystalline hydroxylapatite (HA) to support osseointegration. The nanocrystalline HA was developed with a large rough surface of interconnecting pores between 10 and 20 nm of the silica matrix gel, resulting in a porous bone structure. Mean rates of marginal bone loss were insignificant and the periotest values were indicative of a solid osseointegration.
In effect, the pores are structured in such a way that they are able hold onto the proteins on the biomaterial's surface. Ideally, this allows the body to engage in self-repair in that the synthetic HA is recognized as a like-nanomaterial in which live tissues may develop
Titanium foams can be coated with HA through various methods including plasma spraying, sol-gel and electrophoretic deposition. It has been shown that HA-coated titanium exhibits increased interfacial strength in comparison to titanium foams without the coating. In an effort to enhance bone in-growth, Spoerke et al. developed a method for growing organoapatites on titanium implants. Organoapatites may assist in-bone in-growth at the implant interface. The foams were manufactured using a modified HIP process, which exploits the allotropic nature of titanium to create higher porosity foams. Previous in vitro experimentation with the organoapatite-titanium foam held promising results including the possibility that ingrown tissue within these coated pores will improve the lifetime use of the foam through reduction of stress-shielding effects. | 0 | Theoretical and Fundamental Chemistry |
Canada has the worlds largest deposit of natural bitumen in the Athabasca oil sands, and Canadian First Nations along the Athabasca River had long used it to waterproof their canoes. In 1719, a Cree named Wa-Pa-Su brought a sample for trade to Henry Kelsey of the Hudsons Bay Company, who was the first recorded European to see it. However, it wasn't until 1787 that fur trader and explorer Alexander MacKenzie saw the Athabasca oil sands and said, "At about 24 miles from the fork (of the Athabasca and Clearwater Rivers) are some bituminous fountains into which a pole of 20 feet long may be inserted without the least resistance."
The value of the deposit was obvious from the start, but the means of extracting the bitumen was not. The nearest town, Fort McMurray, Alberta, was a small fur trading post, other markets were far away, and transportation costs were too high to ship the raw bituminous sand for paving. In 1915, Sidney Ells of the Federal Mines Branch experimented with separation techniques and used the product to pave 600 feet of road in Edmonton, Alberta. Other roads in Alberta were paved with material extracted from oil sands, but it was generally not economic. During the 1920s Dr. Karl A. Clark of the Alberta Research Council patented a hot water oil separation process and entrepreneur Robert C. Fitzsimmons built the Bitumount oil separation plant, which between 1925 and 1958 produced up to per day of bitumen using Dr. Clark's method. Most of the bitumen was used for waterproofing roofs, but other uses included fuels, lubrication oils, printers ink, medicines, rust- and acid-proof paints, fireproof roofing, street paving, patent leather, and fence post preservatives. Eventually Fitzsimmons ran out of money and the plant was taken over by the Alberta government. Today the Bitumount plant is a Provincial Historic Site. | 0 | Theoretical and Fundamental Chemistry |
Other uses include making custom-shaped apertures and blocks (for example, electron-beam cutouts and lung blocks) for medical radiation treatment, and making casts of keys that are hard to otherwise duplicate.
Like other fusible alloys, e.g. Roses metal, Woods metal can be used as a heat-transfer medium in hot baths. Hot baths with Roses and Woods metals are not used routinely but are employed at temperatures above .
Wood's metal has a modulus of elasticity of 12.7 GPa and a yield strength of 26.2 MPa. | 1 | Applied and Interdisciplinary Chemistry |
Based on the standard polyvinyl chloride material, three other variants are in use.
One variant called OPVC, or PVCO, represents an important landmark in the history of plastic pipe technology. This molecular-oriented bi-axial high performance version combines higher strength with extra impact resistance.
A ductile variant is the MPVC, polyvinyl chloride modified with acrylics or chlorinated PE. This more ductile material with high fracture resistance is used in higher-demand applications where resistance against cracking and stress corrosion is important. In several studies the long track record of uPVC pipes has been investigated. Recent investigations at the German KRV and the Dutch TNO have confirmed that uPVC water pressure pipes, when installed correctly have a useful life span of over 100 years. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a transition metal boryl complex is a molecular species with a formally anionic boron center coordinated to a transition metal. They have the formula LM-BR or LM-(BRLB) (L = ligand, R = H, organic substituent, LB = Lewis base). One example is (CMe)Mn(CO)(BHPMe) (Me = methyl). Such compounds, especially those derived from catecholborane and the related pinacolborane, are intermediates in transition metal-catalyzed borylation reactions. | 0 | Theoretical and Fundamental Chemistry |
As for ideal MHD, the plasma can be considered as tied to the magnetic field lines when certain conditions are fulfilled. One often says that the magnetic field lines are frozen into the plasma. The frozen-in conditions can be derived from Vlasov equation.
We introduce the scales , , and for time, distance and speed respectively. They represent magnitudes of the different parameters which give large changes in . By large we mean that
We then write
Vlasov equation can now be written
So far no approximations have been done. To be able to proceed we set , where is the gyro frequency and is the gyroradius. By dividing by , we get
If and , the two first terms will be much less than since and due to the definitions of , , and above. Since the last term is of the order of , we can neglect the two first terms and write
This equation can be decomposed into a field aligned and a perpendicular part:
The next step is to write , where
It will soon be clear why this is done. With this substitution, we get
If the parallel electric field is small,
This equation means that the distribution is gyrotropic. The mean velocity of a gyrotropic distribution is zero. Hence, is identical with the mean velocity, , and we have
To summarize, the gyro period and the gyro radius must be much smaller than the typical times and lengths which give large changes in the distribution function. The gyro radius is often estimated by replacing with the thermal velocity or the Alfvén velocity. In the latter case is often called the inertial length. The frozen-in conditions must be evaluated for each particle species separately. Because electrons have much smaller gyro period and gyro radius than ions, the frozen-in conditions will more often be satisfied. | 1 | Applied and Interdisciplinary Chemistry |
Pairs of octahedra can be fused in a way that preserves the octahedral coordination geometry by replacing terminal ligands with bridging ligands. Two motifs for fusing octahedra are common: edge-sharing and face-sharing. Edge- and face-shared bioctahedra have the formulas [ML(μ-L)] and ML(μ-L), respectively. Polymeric versions of the same linking pattern give the stoichiometries [ML(μ-L)] and [M(μ-L)], respectively.
The sharing of an edge or a face of an octahedron gives a structure called bioctahedral. Many metal pentahalide and pentaalkoxide compounds exist in solution and the solid with bioctahedral structures. One example is niobium pentachloride. Metal tetrahalides often exist as polymers with edge-sharing octahedra. Zirconium tetrachloride is an example. Compounds with face-sharing octahedral chains include MoBr, RuBr, and TlBr. | 0 | Theoretical and Fundamental Chemistry |
Around 1990, theoretical and experimental evidence has emerged that forces between charged particles suspended in dilute solutions of monovalent electrolytes might be attractive at larger distances. This evidence is in contradiction with the PB theory discussed above, which always predicts repulsive interactions in these situations. The theoretical treatment leading to these conclusions was strongly criticized. The experimental findings were mostly based on video-microscopy, but the underlying data analysis was questioned concerning the role of impurities, appropriateness of image processing techniques, and the role of hydrodynamic interactions. Despite the initial criticism, accumulative evidence suggest that the DLVO fails to account for essential physics necessary to describe the experimental observations.
While the community remains skeptical regarding the existence of effective attractions between like-charged species, recent computer molecular dynamics simulations with an explicit description of the solvent have demonstrated that the solvent plays an important role in the structure of charged species in solution, while PB and the primitive model do not account for most of these effects. Specifically, the solvent plays a key role in the charge localization of the diffuse ions in ion-rich
domains that bring charged species closer together. Based on this idea, simulations have explained experimental trends such as the disappearance of a scattering peak in salt-free polyelectrolyte solutions and the structural inhomogeneities of charged colloidal particles/nanoparticles observed experimentally that PB and primitive model approaches fail to explain. | 0 | Theoretical and Fundamental Chemistry |
In the context of rainwater harvesting, a first flush diverter is a simple device that is designed to protect a storage cistern from contamination by first flush runoff. This leads to a higher quality of water captured, and less silting of the cistern over time in dusty areas. The diverted first flush water is used for irrigation or other purposes in a fashion similar to greywater. Although many commercial versions are available, these devices are frequently constructed of spare pipe when the cistern is initially installed or thereafter. See Texas Manual on Rainwater Harvesting for calculations on sizing. | 1 | Applied and Interdisciplinary Chemistry |
Unlike the conduction equation (a finite element solution is used), a numerical solution for the convection–diffusion equation has to deal with the convection part of the governing equation in addition to diffusion. When the Péclet number (Pe) exceeds a critical value, the spurious oscillations result in space and this problem is not unique to finite elements as all other discretization techniques have the same difficulties. In a finite difference formulation, the spatial oscillations are reduced by a family of discretization schemes like upwind scheme. In this method, the basic shape function is modified to obtain the upwinding effect. This method is an extension of Runge–Kutta discontinuous for a convection-diffusion equation.
For time-dependent equations, a different kind of approach is followed. The finite difference scheme has an equivalent in the finite element method (Galerkin method). Another similar method is the characteristic Galerkin method (which uses an implicit algorithm). For scalar variables, the above two methods are identical. | 1 | Applied and Interdisciplinary Chemistry |
The idea of affinity is extremely old. Many attempts have been made at identifying its origins. The majority of such attempts, however, except in a general manner, end in futility since "affinities" lie at the basis of all magic, thereby pre-dating science. Physical chemistry, however, was one of the first branches of science to study and formulate a "theory of affinity". The name affinitas was first used in the sense of chemical relation by German philosopher Albertus Magnus near the year 1250. Later, those as Robert Boyle, John Mayow, Johann Glauber, Isaac Newton, and Georg Stahl put forward ideas on elective affinity in attempts to explain how heat is evolved during combustion reactions.
The term affinity has been used figuratively since c. 1600 in discussions of structural relationships in chemistry, philology, etc., and reference to "natural attraction" is from 1616. "Chemical affinity", historically, has referred to the "force" that causes chemical reactions. as well as, more generally, and earlier, the ″tendency to combine″ of any pair of substances. The broad definition, used generally throughout history, is that chemical affinity is that whereby substances enter into or resist decomposition.
The modern term chemical affinity is a somewhat modified variation of its eighteenth-century precursor "elective affinity" or elective attractions, a term that was used by the 18th century chemistry lecturer William Cullen. Whether Cullen coined the phrase is not clear, but his usage seems to predate most others, although it rapidly became widespread across Europe, and was used in particular by the Swedish chemist Torbern Olof Bergman throughout his book (1775). Affinity theories were used in one way or another by most chemists from around the middle of the 18th century into the 19th century to explain and organise the different combinations into which substances could enter and from which they could be retrieved. Antoine Lavoisier, in his famed 1789 Traité Élémentaire de Chimie (Elements of Chemistry), refers to Bergman's work and discusses the concept of elective affinities or attractions.
According to chemistry historian Henry Leicester, the influential 1923 textbook Thermodynamics and the Free Energy of Chemical Reactions by Gilbert N. Lewis and Merle Randall led to the replacement of the term "affinity" by the term "free energy" in much of the English-speaking world.
According to Prigogine, the term was introduced and developed by Théophile de Donder.
Goethe used the concept in his novel Elective Affinities (1809). | 0 | Theoretical and Fundamental Chemistry |
Measuring the extent and kinetics of radioligand binding is important in determining information about binding sites of radioligands, and subsequent affinity to potential drugs. Three different binding assays are typically used for radioligand binding; these are saturation, competition, and kinetic binding. | 1 | Applied and Interdisciplinary Chemistry |
Epideictic pheromones are different from territory pheromones, when it comes to insects. Fabre observed and noted how "females who lay their eggs in these fruits deposit these mysterious substances in the vicinity of their clutch to signal to other females of the same species they should clutch elsewhere." It may be helpful to note that the word epideictic, having to do with display or show (from the Greek deixis), has a different but related meaning in rhetoric, the human art of persuasion by means of words. | 1 | Applied and Interdisciplinary Chemistry |
Particular attention must be paid to vias and contact holes. The current carrying capacity of a via is much less than a metallic wire of same length. Hence multiple vias are often used, whereby the geometry of the via array is very significant: multiple vias must be organized such that the resulting current is distributed as evenly as possible through all the vias.
Attention must also be paid to bends in interconnects. In particular, 90-degree corner bends must be avoided, since the current density in such bends is significantly higher than that in oblique angles (e.g., 135 degrees). | 0 | Theoretical and Fundamental Chemistry |
The stability of a supramolecular polymer can be described using the association constant, K. When K ≤ 10M, the polymeric aggregates are typically small in size and do not show any interesting properties and when K≥ 10 M, the supramolecular polymer behaves just like covalent polymers due to the lack of dynamics. So, an optimum K = 10–10Mneed to be attained for producing functional supramolecular polymers. The dynamics and stability of the supramolecular polymers often affect by the influence of additives (e.g. co-solvent or chain-capper). When a good solvent, for instance chloroform, is added to a supramolecular polymer in a poor solvent, for instance heptane, the polymer disassembles. However, in some cases, cosolvents contribute the stabilization/destabilization of supramolecular polymer. For instance, supramolecular polymerization of a hydrogen bonding porphyrin-based monomer in a hydrocarbon solvent containing a minute amount of a hydrogen bond scavenging alcohol shows distinct pathways, i.e. polymerization favored both by cooling as well as heating, and is known as "thermally bisignate supramolecular polymerization". In another example, minute amounts of molecularly dissolved water molecules in apolar solvents, like methylcyclohexane, become part of the supramolecular polymer at lower temperatures, due to specific hydrogen bonding interaction between the monomer and water. | 0 | Theoretical and Fundamental Chemistry |
Pyruvate kinase isozymes M1/M2 (PKM1/M2), also known as pyruvate kinase muscle isozyme (PKM), pyruvate kinase type K, cytosolic thyroid hormone-binding protein (CTHBP), thyroid hormone-binding protein 1 (THBP1), or opa-interacting protein 3 (OIP3), is an enzyme that in humans is encoded by the PKM2 gene.
PKM2 is an isoenzyme of the glycolytic enzyme pyruvate kinase. Depending upon the different metabolic functions of the tissues, different isoenzymes of pyruvate kinase are expressed. PKM2 is expressed in some differentiated tissues, such as lung, fat tissue, retina, and pancreatic islets, as well as in all cells with a high rate of nucleic acid synthesis, such as normal proliferating cells, embryonic cells, and especially tumor cells. | 1 | Applied and Interdisciplinary Chemistry |
The photosynthesis process in chloroplasts begins when an electron of P680 of PSII attains a higher-energy level. This energy is used to reduce a chain of electron acceptors that have subsequently higher redox potentials. This chain of electron acceptors is known as an electron transport chain. When this chain reaches PSI, an electron is again excited, creating a high redox-potential. The electron transport chain of photosynthesis is often put in a diagram called the Z-scheme, because the redox diagram from P680 to P700 resembles the letter Z.
The final product of PSII is plastoquinol, a mobile electron carrier in the membrane. Plastoquinol transfers the electron from PSII to the proton pump, cytochrome b6f. The ultimate electron donor of PSII is water. Cytochrome bf transfers the electron chain to PSI through plastocyanin molecules. PSI can continue the electron transfer in two different ways. It can transfer the electrons either to plastoquinol again, creating a cyclic electron flow, or to an enzyme called FNR (Ferredoxin—NADP(+) reductase), creating a non-cyclic electron flow. PSI releases FNR into the stroma, where it reduces to NADPH.
Activities of the electron transport chain, especially from cytochrome bf, lead to pumping of protons from the stroma to the lumen. The resulting transmembrane proton gradient is used to make ATP via ATP synthase.
The overall process of the photosynthetic electron transport chain in chloroplasts is: | 0 | Theoretical and Fundamental Chemistry |
Some cyanobacteria can produce neurotoxins, cytotoxins, endotoxins, and hepatotoxins (e.g., the microcystin-producing bacteria genus microcystis), which are collectively known as cyanotoxins.
Specific toxins include anatoxin-a, guanitoxin, aplysiatoxin, cyanopeptolin, cylindrospermopsin, domoic acid, nodularin R (from Nodularia), neosaxitoxin, and saxitoxin. Cyanobacteria reproduce explosively under certain conditions. This results in algal blooms which can become harmful to other species and pose a danger to humans and animals if the cyanobacteria involved produce toxins. Several cases of human poisoning have been documented, but a lack of knowledge prevents an accurate assessment of the risks, and research by Linda Lawton, FRSE at Robert Gordon University, Aberdeen and collaborators has 30 years of examining the phenomenon and methods of improving water safety.
Recent studies suggest that significant exposure to high levels of cyanobacteria producing toxins such as BMAA can cause amyotrophic lateral sclerosis (ALS). People living within half a mile of cyanobacterially contaminated lakes have had a 2.3 times greater risk of developing ALS than the rest of the population; people around New Hampshire's Lake Mascoma had an up to 25 times greater risk of ALS than the expected incidence. BMAA from desert crusts found throughout Qatar might have contributed to higher rates of ALS in Gulf War veterans. | 0 | Theoretical and Fundamental Chemistry |
Life Cycle Analysis (LCA) is an important tool for ecological evaluation of products or processes. LCA is an internationally accepted standard (ISO 14040 & ISO 14044) and scientific tool that is used to quantify the environmental performance attributable to the different life stages of our products, including upstream stages such as raw material production and energy supply. Results are benchmarked based on LCA indicators with the final aim of identifying operational efficiencies and optimising product design while providing a higher level of environmental transparency.
The life-cycle of glass starts from extraction of raw materials, to distribution, use by final consumers to disposal/landfilling. In light of saving the economy and the environment, researchers are working to eliminate the linearity of this lifecycle to have a circular/closed loop life cycle where extraction of raw materials and landfilling after final consumption will be eliminated.
Glass takes up to millions of years to decompose in the environment and even more in landfill. Fortunately, glass is 100% recyclable, making it a sustainable resource for producing new forms of packaging without relying on raw materials. The problem now is that only 70% of glasses are being collected for recycling in the EU (30% in the US) (which is already good, but can be better). Its recyclability can hence be improved by improving its collection rate all around the world. The only way we can increase collection rate is to enlighten every single consumer of glass to properly dispose and speak up against improper disposal of this glass. | 0 | Theoretical and Fundamental Chemistry |
The Ames process was used on August 3, 1942, by a group of chemists led by Frank Spedding and Harley Wilhelm at the Ames Laboratory as part of the Manhattan Project. It is a type of thermite-based purification, which was patented in 1895 by German chemist Hans Goldschmidt. Development of the Ames process came at a time of increased research into mass uranium-metal production. The desire for increased production was motivated by a fear of Nazi Germany's developing nuclear weapons before the Allies. The process originally involved mixing powdered uranium tetrafluoride and powdered magnesium together. This mixture was placed inside an iron pipe that was welded shut on one side and capped shut on another side. This container, called a "bomb" by Spedding, was placed into a furnace. When heated to a temperature of , the contents of the container reacted violently, leaving a 35-gram ingot of pure uranium metal. The process was quickly scaled up; by October 1942 the "Ames Project" was producing metal at a rate of per week. The uranium tetrafluoride and magnesium were sealed in a refractory-lined reactor vessel, still referred to as a "bomb". The thermite reaction was initiated by furnace heating the assembly to ; the large difference in density between slag and metal allowed complete separation in the liquid state, yielding slag-free metal. By July 1943, the production rate exceeded of uranium metal per month. Approximately 1000 tons of uranium ingots were produced at Ames before the process was transferred to industry.
The Ames project received the Army-Navy "E" Award for Excellence in Production on October 12, 1945, signifying 2.5 years of excellence in industrial production of metallic uranium as a vital war material. Iowa State University is unique among educational institutions to have received this award for outstanding service, an honor normally given to industry. | 1 | Applied and Interdisciplinary Chemistry |
A mass spectrometer is typically utilized in one of two ways: full scan or selective ion monitoring (SIM). The typical GC–MS instrument is capable of performing both functions either individually or concomitantly, depending on the setup of the particular instrument.
The primary goal of instrument analysis is to quantify an amount of substance. This is done by comparing the relative concentrations among the atomic masses in the generated spectrum. Two kinds of analysis are possible, comparative and original. Comparative analysis essentially compares the given spectrum to a spectrum library to see if its characteristics are present for some sample in the library. This is best performed by a computer because there are a myriad of visual distortions that can take place due to variations in scale. Computers can also simultaneously correlate more data (such as the retention times identified by GC), to more accurately relate certain data. Deep learning was shown to lead to promising results in the identification of VOCs from raw GC–MS data.
Another method of analysis measures the peaks in relation to one another. In this method, the tallest peak is assigned 100% of the value, and the other peaks being assigned proportionate values. All values above 3% are assigned. The total mass of the unknown compound is normally indicated by the parent peak. The value of this parent peak can be used to fit with a chemical formula containing the various elements which are believed to be in the compound. The isotope pattern in the spectrum, which is unique for elements that have many natural isotopes, can also be used to identify the various elements present. Once a chemical formula has been matched to the spectrum, the molecular structure and bonding can be identified, and must be consistent with the characteristics recorded by GC–MS. Typically, this identification is done automatically by programs which come with the instrument, given a list of the elements which could be present in the sample.
A "full spectrum" analysis considers all the "peaks" within a spectrum. Conversely, selective ion monitoring (SIM) only monitors selected ions associated with a specific substance. This is done on the assumption that at a given retention time, a set of ions is characteristic of a certain compound. This is a fast and efficient analysis, especially if the analyst has previous information about a sample or is only looking for a few specific substances. When the amount of information collected about the ions in a given gas chromatographic peak decreases, the sensitivity of the analysis increases. So, SIM analysis allows for a smaller quantity of a compound to be detected and measured, but the degree of certainty about the identity of that compound is reduced. | 0 | Theoretical and Fundamental Chemistry |
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