text
stringlengths 105
4.57k
| label
int64 0
1
| label_text
stringclasses 2
values |
|---|---|---|
George Warren Hammond (April 4, 1833 – January 6, 1908) was an American businessman. Camp Hammond, in Yarmouth, Maine, is named for him. He was also one of its architects. Built in , it was placed on the National Register of Historic Places in 1979.
Hammond was also co-owner of Forest Paper Company, which was the largest paper mill in the world at the time of his death. The mill was also known as a pioneer in the processing of soda pulp. | 1 | Applied and Interdisciplinary Chemistry |
In North America, union pipefitters are members of the United Association. Wages vary from area to area, based on demands for experienced personnel and existing contracts between local unions and contractors. The United Association is also affiliated with the piping trades unions in Ireland and Australia. | 1 | Applied and Interdisciplinary Chemistry |
The first recombinant plant-derived protein (PDP) was human serum albumin, initially produced in 1990 in transgenic tobacco and potato plants. Open field growing trials of these crops began in the United States in 1992 and have taken place every year since. While the United States Department of Agriculture has approved planting of pharma crops in every state, most testing has taken place in Hawaii, Nebraska, Iowa, and Wisconsin.
In the early 2000s, the pharming industry was robust. Proof of concept has been established for the production of many therapeutic proteins, including antibodies, blood products, cytokines, growth factors, hormones, recombinant enzymes and human and veterinary vaccines. By 2003 several PDP products for the treatment of human diseases were under development by nearly 200 biotech companies, including recombinant gastric lipase for the treatment of cystic fibrosis, and antibodies for the prevention of dental caries and the treatment of non-Hodgkin's lymphoma.
However, in late 2002, just as ProdiGene was ramping up production of trypsin for commercial launch it was discovered that volunteer plants (left over from the prior harvest) of one of their GM corn products were harvested with the conventional soybean crop later planted in that field. ProdiGene was fined $250,000 and ordered by the USDA to pay over $3 million in cleanup costs. This raised a furor and set the pharming field back, dramatically. Many companies went bankrupt as companies faced difficulties getting permits for field trials and investors fled. In reaction, APHIS introduced more strict regulations for pharming field trials in the US in 2003. In 2005, Anheuser-Busch threatened to boycott rice grown in Missouri because of plans by Ventria Bioscience to grow pharm rice in the state. A compromise was reached, but Ventria withdrew its permit to plant in Missouri due to unrelated circumstances.
The industry has slowly recovered, by focusing on pharming in simple plants grown in bioreactors and on growing GM crops in greenhouses. Some companies and academic groups have continued with open-field trials of GM crops that produce drugs. In 2006 Dow AgroSciences received USDA approval to market a vaccine for poultry against Newcastle disease, produced in plant cell culture – the first plant-produced vaccine approved in the U.S. | 1 | Applied and Interdisciplinary Chemistry |
In the early 1920s, pharmacist Alexis Moussalli joined the Millot pharmaceutical laboratories in Paris. Leveraging his expertise of rare-earth elements, he invented a beauty cream laden with thorium chloride and radium bromide. In order to start his own brand and as a marketing device, he associated with Alfred Curie, a medical doctor, homonymous to Pierre and Marie Curie but with no connection to them. Pierre and Marie Curie apparently considered legal action against the company. Alfred Curie was to register the Tho-Radia brand on 29 November 1932 and approved the mention "after Dr Alfred Curie's formula" on the packaging and publicities. | 0 | Theoretical and Fundamental Chemistry |
Like all phyllosilicates, clay minerals are characterised by two-dimensional sheets of corner-sharing tetrahedra or octahedra. The sheet units have the chemical composition . Each silica tetrahedron shares three of its vertex oxygen ions with other tetrahedra, forming a hexagonal array in two dimensions. The fourth oxygen ion is not shared with another tetrahedron and all of the tetrahedra "point" in the same direction; i.e. all of the unshared oxygen ions are on the same side of the sheet. These unshared oxygen ions are called apical oxygen ions.
In clays, the tetrahedral sheets are always bonded to octahedral sheets formed from small cations, such as aluminum or magnesium, and coordinated by six oxygen atoms. The unshared vertex from the tetrahedral sheet also forms part of one side of the octahedral sheet, but an additional oxygen atom is located above the gap in the tetrahedral sheet at the center of the six tetrahedra. This oxygen atom is bonded to a hydrogen atom forming an OH group in the clay structure. Clays can be categorized depending on the way that tetrahedral and octahedral sheets are packaged into layers. If there is only one tetrahedral and one octahedral group in each layer the clay is known as a 1:1 clay. The alternative, known as a 2:1 clay, has two tetrahedral sheets with the unshared vertex of each sheet pointing towards each other and forming each side of the octahedral sheet.
Bonding between the tetrahedral and octahedral sheets requires that the tetrahedral sheet becomes corrugated or twisted, causing ditrigonal distortion to the hexagonal array, and the octahedral sheet is flattened. This minimizes the overall bond-valence distortions of the crystallite.
Depending on the composition of the tetrahedral and octahedral sheets, the layer will have no charge or will have a net negative charge. If the layers are charged this charge is balanced by interlayer cations such as Na or K or by a lone octahedral sheet. The interlayer may also contain water. The crystal structure is formed from a stack of layers interspaced with the interlayers. | 0 | Theoretical and Fundamental Chemistry |
Certain skin conditions, including keratosis, psoriasis, eczema and acne, may be treated with UVB light therapy, including by using tanning beds in commercial salons. Using tanning beds allows patients to access UV exposure when dermatologist-provided phototherapy is not available. A systematic review of studies, published in Dermatology and Therapy in 2015, noted that moderate sunlight is a treatment recommended by the American National Psoriasis Foundation, and suggested that clinicians consider UV phototherapy and tanning beds as a source of that therapy.
When UV light therapy is used in combination with psoralen, an oral or topical medication, the combined therapy is referred to as PUVA. A concern with the use of commercial tanning is that beds that primarily emit UVA may not treat psoriasis effectively. One study found that plaque psoriasis is responsive to erythemogenic doses of either UVA or UVB. It does require more energy to reach erythemogenic dosing with UVA. | 0 | Theoretical and Fundamental Chemistry |
Between 1920 and 1930 fundamental concepts of quantum mechanics were developed by Pauli, Heisenberg, Schrödinger, and Dirac. Understanding of the spin and exclusion principle allowed conceiving how electron shells of atoms are filled with the increasing atomic number. | 0 | Theoretical and Fundamental Chemistry |
In the S-matrix formulation of particle physics, which was pioneered by John Archibald Wheeler among others, all physical processes are modeled according to the following paradigm.
One begins with a non-interacting multiparticle state in the distant past. Non-interacting does not mean that all of the forces have been turned off, in which case for example protons would fall apart, but rather that there exists an interaction-free Hamiltonian H, for which the bound states have the same energy level spectrum as the actual Hamiltonian . This initial state is referred to as the in state. Intuitively, it consists of elementary particles or bound states that are sufficiently well separated that their interactions with each other are ignored.
The idea is that whatever physical process one is trying to study may be modeled as a scattering process of these well separated bound states. This process is described by the full Hamiltonian , but once its over, all of the new elementary particles and new bound states separate again and one finds a new noninteracting state called the out state'. The S-matrix is more symmetric under relativity than the Hamiltonian, because it does not require a choice of time slices to define.
This paradigm allows one to calculate the probabilities of all of the processes that we have observed in 70 years of particle collider experiments with remarkable accuracy. But many interesting physical phenomena do not obviously fit into this paradigm. For example, if one wishes to consider the dynamics inside of a neutron star sometimes one wants to know more than what it will finally decay into. In other words, one may be interested in measurements that are not in the asymptotic future. Sometimes an asymptotic past or future is not even available. For example, it is very possible that there is no past before the Big Bang.
In the 1960s, the S-matrix paradigm was elevated by many physicists to a fundamental law of nature. In S-matrix theory, it was stated that any quantity that one could measure should be found in the S-matrix for some process. This idea was inspired by the physical interpretation that S-matrix techniques could give to Feynman diagrams restricted to the mass-shell, and led to the construction of dual resonance models. But it was very controversial, because it denied the validity of quantum field theory based on local fields and Hamiltonians. | 0 | Theoretical and Fundamental Chemistry |
Volatolomics is a branch of chemistry that studies volatile organic compounds (VOCs) emitted by a biological system, under specific experimental conditions. | 0 | Theoretical and Fundamental Chemistry |
Acid-base extraction is frequently used as the first step in a work-up procedure following a chemical synthesis to remove acidic and basic starting materials or impurities. Acid-base extraction is typically a precursor to more complicated purification techniques, such as recrystallization, if the product synthesized is still not completely pure.
Organic synthesis often uses acid-base extractions during work-up procedures. For example, consider a Fischer esterification –– the condensation of a carboxylic acid with an alcohol to form an ester. The post-reaction mixture often consists of small amounts of leftover acid and alcohol, in addition to the desired ester. Acid-base extraction can be used to easily separate out the acidic starting materials from the ester. By rinsing the crude product mixture with a weak base (e.g. sodium bicarbonate), the carboxylic acid and alcohol will be washed away with the aqueous layer, leaving purified ester in the organic layer. The choice of base used for extraction is critical, as a strong base (e.g. sodium hydroxide) will hydrolyze the ester.
Another common example of acid-base extraction occurs following peptide coupling, where the amide product must be separated from leftover carboxylic acid and amine. The carboxylic acid can be removed by rinsing the organic layer with weak base (sodium bicarbonate), while the amine can be removed by rinsing with a weak acid (10% hydrochloric acid). Following these two extractions, the amide will remain in the organic layer and has been significantly purified. | 0 | Theoretical and Fundamental Chemistry |
There are two types of β-agonists, long- and short-acting. They are both inhaled and given by aerosol delivery devices.
Long-lasting β-agonists are often given in a combination with corticosteroids to treat asthma. Short-acting β-agonists are used to treat exercise-induced asthma,
and for asthma patients to get a quick relief of symptoms. They are taken 10–15 minutes before exercise. The bronchodilation begins few minutes after inhalation of short-acting β-agonists and lasts from 4 to 8 hours.
Long-lasting β-agonists are discouraged in treating acute exercise-induced asthma, because their chronic use might mask poorly controlled asthma. | 1 | Applied and Interdisciplinary Chemistry |
DOC is conceptually divided into labile DOC, which is rapidly taken up by heterotrophic microbes, and the recalcitrant DOC reservoir, which has accumulated in the ocean (following a definition by Hansell). As a consequence of its recalcitrance, the accumulated DOC reaches average radiocarbon ages between 1,000 and 4,000 years in surface waters, and between 3,000 and 6,000 years in the deep ocean, indicating that it persists through several deep ocean mixing cycles between 300 and 1,400 years each. Behind these average radiocarbon ages, a large spectrum of ages is hidden. Follett et al. showed DOC comprises a fraction of modern radiocarbon age, as well as DOC reaching radiocarbon ages of up to 12,000 years. | 1 | Applied and Interdisciplinary Chemistry |
Flavins (from Latin flavus, "yellow") refers generally to the class of organic compounds containing the tricyclic heterocycle isoalloxazine or its isomer alloxazine, and derivatives thereof. The biochemical source of flavin is the yellow B vitamin riboflavin. The flavin moiety is often attached with an adenosine diphosphate to form flavin adenine dinucleotide (FAD), and, in other circumstances, is found as flavin mononucleotide (or FMN), a phosphorylated form of riboflavin. It is in one or the other of these forms that flavin is present as a prosthetic group in flavoproteins. Despite the similar names, flavins (with "i") are chemically and biologically distinct from the flavanoids (with "a"), and the flavonols (with "o").
The flavin group is capable of undergoing oxidation-reduction reactions, and can accept either one electron in a two-step process or two electrons at once. Reduction is made with the addition of hydrogen atoms to specific nitrogen atoms on the isoalloxazine ring system:
In aqueous solution, flavins are yellow-coloured when oxidized, taking a red colour in the semi-reduced anionic state or blue in the neutral (semiquinone) state, and colourless when totally reduced. The oxidized and reduced forms are in fast equilibrium with the semiquinone (radical) form, shifted against the formation of the radical:
::Fl + FlH ⇌ FlH
where Fl is the oxidized flavin, FlH the reduced flavin (upon addition of two hydrogen atoms) and FlH the semiquinone form (addition of one hydrogen atom).
In the form of FADH, it is one of the cofactors that can transfer electrons to the electron transfer chain. | 1 | Applied and Interdisciplinary Chemistry |
Knowledge of hydration is essential for calculating the masses for many compounds. The reactivity of many salt-like solids is sensitive to the presence of water.
The hydration and dehydration of salts is central to the use of phase-change materials for energy storage. | 0 | Theoretical and Fundamental Chemistry |
The Batchelor–Chandrasekhar equation is the evolution equation for the scalar functions, defining the two-point velocity correlation tensor of a homogeneous axisymmetric turbulence, named after George Batchelor and Subrahmanyan Chandrasekhar. They developed the theory of homogeneous axisymmetric turbulence based on Howard P. Robertson's work on isotropic turbulence using an invariant principle. This equation is an extension of Kármán–Howarth equation from isotropic to axisymmetric turbulence. | 1 | Applied and Interdisciplinary Chemistry |
In the 1960s there was a lot of interest in fluorocarbons as anesthetics. The research did not produce any anesthetics, but the research included tests on the issue of flammability, and showed that the tested fluorocarbons were not flammable in air in any proportion, though most of the tests were in pure oxygen or pure nitrous oxide (gases of importance in anesthesiology).
In 1993, 3M considered fluorocarbons as fire extinguishants to replace CFCs. This extinguishing effect has been attributed to their high heat capacity, which takes heat away from the fire. It has been suggested that an atmosphere containing a significant percentage of perfluorocarbons on a space station or similar would prevent fires altogether.
When combustion does occur, toxic fumes result, including carbonyl fluoride, carbon monoxide, and hydrogen fluoride. | 1 | Applied and Interdisciplinary Chemistry |
Measurements of Δ can be used to better understand the physiology of extinct organisms, and to place constraints on the early development of endothermy, the process by which organisms regulate their internal body temperatures. Prior to the development of clumped isotope analysis, there was no straightforward way to estimate either the body temperature or body water δO of extinct animals. Eagle et al., 2010 measure Δ47 in bioapatite from a modern Indian elephant, white rhinoceros, Nile crocodile and American alligator. These animals were chosen as they span a wide range in internal body temperatures, allowing for the creation of a mathematical framework relating Δ of bioapatite and internal body temperature. This relationship has been applied to analyses of fossil teeth, in order to predict the body temperatures of a woolly mammoth and a sauropod dinosaur. The latest Δ temperature calibration for (bio)apatite of Löffler et al. 2019 covers a wide temperature range of 1 to 80 °C and was applied to a fossil megalodon shark tooth for calculating seawater temperatures and δO values. | 0 | Theoretical and Fundamental Chemistry |
IPA can be converted in the liver or kidneys to 3-indoleacrylic acid, which is subsequently conjugated with glycine, forming indolylacryloyl glycine. | 1 | Applied and Interdisciplinary Chemistry |
* (Original paper is available at: https://www.irphe.fr/~clanet/otherpaperfile/articles/Rayleigh/rayleigh1883.pdf .) | 1 | Applied and Interdisciplinary Chemistry |
The coffee-ring pattern is detrimental when uniform application of a dried deposit is required, such as in printed electronics. It can be suppressed by adding elongated particles, such as cellulose fibers, to the spherical particles that cause the coffee-ring effect. The size and weight fraction of added particles may be smaller than those of the primary ones.
It is also reported that controlling flow inside a droplet is a powerful way to generate a uniform film; for example, by harnessing solutal Marangoni flows occurring during evaporation.
Mixtures of low boiling point and high boiling point solvents were shown to suppress the coffee ring effect, changing the shape of a deposited solute from a ring-like to a dot-like shape.
Control of the substrate temperature was shown to be an effective way to suppress the coffee ring formed by droplets of water-based PEDOT:PSS solution. On a heated hydrophilic or hydrophobic substrate, a thinner ring with an inner deposit forms, which is attributed to Marangoni convection.
Control of the substrate wetting properties on slippery surfaces can prevent the pinning of the drop contact line, which will, therefore, suppress the coffee ring effect by reducing the number of particles deposited at the contact line. Drops on superhydrophobic or liquid impregnated surfaces are less likely to have a pinned contact line and will suppress ring formation. Drops with an oil ring formed at the drop contact line have high mobility and can avoid the ring formation on hydrophobic surfaces.
Alternating voltage electrowetting may suppress coffee stains without the need to add surface-active materials. Reverse particle motion may also reduce the coffee-ring effect because of the capillary force near the contact line. The reversal takes place when the capillary force prevails over the outward coffee-ring flow by the geometric constraints. | 0 | Theoretical and Fundamental Chemistry |
Ligands targeting the mAChR that are currently approved for clinical use include non-selective antagonists for the treatment of Parkinson's disease, atropine (to dilate the pupil), scopolamine (used to prevent motion sickness), and ipratropium (used in the treatment of COPD). | 1 | Applied and Interdisciplinary Chemistry |
JES is the flagship journal of The Electrochemical Society. Published continuously from 1902 to the present, JES is one of the most highly-cited journals in electrochemistry and solid-state science and technology. | 0 | Theoretical and Fundamental Chemistry |
For pol II-transcribed genes, and unlike bacterial RNA polymerase, promoter melting requires hydrolysis of ATP and is mediated by TFIIH. TFIIH is a ten-subunit protein, including both ATPase and protein kinase activities. While the upstream promoter DNA is held in a fixed position by TFIID, TFIIH pulls downstream double-stranded DNA into the cleft of the polymerase, driving the separation of DNA strands and the transition of the preinitiation complex from the closed to open state. TFIIB aids in open complex formation by binding the melted DNA and stabilizing the transcription bubble. | 1 | Applied and Interdisciplinary Chemistry |
Silent Information Regulator (SIR) proteins are involved in regulating gene expression. SIR proteins organize heterochromatin near telomeres, ribosomal DNA (rDNA), and at silent loci including hidden mating type loci in yeast. The SIR family of genes encodes catalytic and non-catalytic proteins that are involved in de-acetylation of histone tails and the subsequent condensation of chromatin around a SIR protein scaffold. Some SIR family members are conserved from yeast to humans. | 1 | Applied and Interdisciplinary Chemistry |
Scar sequences are common in multiple segment DNA assembly. In the multisegment assembly method Gateway, segments are added into the donor with additional ATT sequences, which overlap in those added segments, and this results in the segments separated by the ATT sequences. In BioBrick assembly, an eight-nucleotide scar sequence, which codes for a tyrosine and a stop codon, is left between every segment added into the plasmid.
Golden Gate assembly uses Type IIS restriction enzymes cutting outside their recognition sequences. Also, the same Type IIS restriction enzyme can generate copious different overhangs on the inserts and the vector; for instance, BsaI creates 256 four-basepair overhangs. If the overhangs are carefully designed, the segments are ligated without scar sequences between them, and the final construct can be quasi-scarless, where the restriction enzyme sites remain on both sides of the insert. As additional segments can be inserted into the vectors without scars within an open reading frame, Golden Gate is widely used in protein engineering. | 1 | Applied and Interdisciplinary Chemistry |
The Food and Drug Administration (FDA) classifies tanning beds as "moderate risk" devices (changed in 2014 from "low risk"). It requires that devices carry a black box warning that they should not be used by individuals under the age of 18, but it has not banned their use by minors. , California, Delaware, the District of Columbia, Hawaii, Illinois, Kansas, Louisiana, Massachusetts, Minnesota, Nevada, New Hampshire, North Carolina, Oregon, Texas, Vermont and Washington have banned the use of tanning beds for minors under the age of 18. Other states strictly regulate indoor tanning under the age of 18, with most banning indoor tanning for persons under the age of 14 unless medically required, and some requiring the consent of a guardian for those aged 14–17. In 2010 under the Affordable Care Act, a 10% "tanning tax" was introduced, which is added to the fees charged by tanning facilities; it was expected to raise $2.7 billion for health care over ten years.
Tanning beds are regulated in the United States by the federal governments Code of Federal Regulations (21 CFR 1040.20). This is designed to ensure that the devices adhere to a set of safety rules, with the primary focus on sunbed and lamp manufacturers regarding maximum exposure times and product equivalence. Additionally, must have a "Recommended Exposure Schedule" posted on both the front of the tanning bed and in the owners manual, and list the original lamp that was certified for that particular tanning bed. Salon owners are required to replace the lamps with either exactly the same lamp, or a lamp that is certified by the lamp manufacturer to be.
States control regulations for salons, regarding operator training, sanitization of sunbeds and eyewear, and additional warning signs. Many states also ban or regulate the use of tanning beds by minors under the age of 18.
American osteopathic physician Joseph Mercola was prosecuted in 2016 by the Federal Trade Commission (FTC) for selling tanning beds to "reverse your wrinkles" and "slash your risk of cancer". The settlement meant that consumers who had purchased the devices were eligible for refunds totalling $5.3 million. Mercola had falsely claimed that the FDA "endorsed indoor tanning devices as safe", and had failed to disclose that he had paid the Vitamin D Council for its endorsement of his devices. The FTC said that it was deceptive for the defendants to fail to disclose that tanning is not necessary to produce vitamin D. | 0 | Theoretical and Fundamental Chemistry |
Lead azide in its pure form was first prepared by Theodor Curtius in 1891. Due to sensitivity and stability concerns, the dextrinated form of lead azide (MIL-L-3055) was developed in the 1920s and 1930s with large scale production by DuPont Co beginning in 1932. Detonator development during World War II resulted in the need for a form of lead azide with a more brisant output. RD-1333 lead azide (MIL-DTL-46225), a version of lead azide with sodium carboxymethyl cellulose as a precipitating agent, was developed to meet that need. The Vietnam War saw an accelerated need for lead azide and it was during this time that Special Purpose Lead Azide (MIL-L-14758) was developed; the US government also began stockpiling lead azide in large quantities. After the Vietnam War, the use of lead azide dramatically decreased. Due to the size of the US stockpile, the manufacture of lead azide in the US ceased completely by the early 1990s. In the 2000s, concerns about the age and stability of stockpiled lead azide led the US government to investigate methods to dispose of its stockpiled lead azide and obtain new manufacturers. | 0 | Theoretical and Fundamental Chemistry |
Vasilis Gregoriou (born 1965, Trikala, Greece) is a researcher, inventor, technology entrepreneur and former Director and Chairman of the Board of Directors at National Hellenic Research Foundation (NHRF) in Athens, Greece. During his career, he has achieved international recognition by serving in research and administrative positions both in Greece and the US. His studies in Greece began at the University of Patras (BSc. Chemistry) while his studies in the United States took place at Duke University where he received a PhD degree in Physical Chemistry. He was also a National Research Service Award recipient at Princeton University. | 0 | Theoretical and Fundamental Chemistry |
In Finland, green roofs are still scarce. Some experimental green roofs have been built in big cities. However, the capital city of Helsinki has published guidelines for enhancing the building of green roofs in the city. There is on-going research on the topic as the conditions in the southern Europe are very different from those in the north and knowledge acquired there can't be directly applied to colder climates. The fifth dimension – [https://www.researchgate.net/project/Fifth-Dimension-Green-Roofs-and-Walls-in-Urban-Areas-research-program Green roofs and walls in urban areas -research program] aims to produce high-level scientific and broadly applicable knowledge on optimal green roof and -wall solutions in Finland. | 1 | Applied and Interdisciplinary Chemistry |
Since many sources of human food are ultimately derived from terrestrial plants, the relative concentration of carbon-14 in human bodies is nearly identical to the relative concentration in the atmosphere. The rates of disintegration of potassium-40 and carbon-14 in the normal adult body are comparable (a few thousand disintegrated nuclei per second). The beta decays from external (environmental) radiocarbon contribute approximately 0.01 mSv/year (1 mrem/year) to each person's dose of ionizing radiation. This is small compared to the doses from potassium-40 (0.39 mSv/year) and radon (variable).
Carbon-14 can be used as a radioactive tracer in medicine. In the initial variant of the urea breath test, a diagnostic test for Helicobacter pylori, urea labeled with approximately carbon-14 is fed to a patient (i.e., 37,000 decays per second). In the event of a H. pylori infection, the bacterial urease enzyme breaks down the urea into ammonia and radioactively-labeled carbon dioxide, which can be detected by low-level counting of the patient's breath. | 0 | Theoretical and Fundamental Chemistry |
Metal carbonyls are often characterized by C NMR spectroscopy. To improve the sensitivity of this technique, complexes are often enriched with CO. Typical chemical shift range for terminally bound ligands is 150 to 220 ppm. Bridging ligands resonate between 230 and 280 ppm. The C signals shift toward higher fields with an increasing atomic number of the central metal.
NMR spectroscopy can be used for experimental determination of the fluxionality.
The activation energy of ligand exchange processes can be determined by the temperature dependence of the line broadening. | 0 | Theoretical and Fundamental Chemistry |
Mass-independent isotope fractionation or Non-mass-dependent fractionation (NMD), refers to any chemical or physical process that acts to separate isotopes, where the amount of separation does not scale in proportion with the difference in the masses of the isotopes. Most isotopic fractionations (including typical kinetic fractionations and equilibrium fractionations) are caused by the effects of the mass of an isotope on atomic or molecular velocities, diffusivities or bond strengths. Mass-independent fractionation processes are less common, occurring mainly in photochemical and spin-forbidden reactions. Observation of mass-independently fractionated materials can therefore be used to trace these types of reactions in nature and in laboratory experiments. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, the Cornforth rearrangement is a rearrangement reaction of a 4-acyloxazole in which the group attached to an acyl on position 4 and the substituent on position 5 of an oxazole ring exchange places. It was first reported in 1949, and is named for John Cornforth. The reaction is used in the synthesis of amino acids, where the corresponding oxazoles occur as intermediates. | 0 | Theoretical and Fundamental Chemistry |
He completed his Ph.D. in chemical engineering at the University of Minnesota in 1975, with advisors Arnold Fredrickson and Rutherford Aris on the topic of modeling of population dynamics. He thesis was published in 1978 with the title, "Mathematical Modelling of the Dynamics of Interacting Microbial Populations. Extinction Probabilities in a Stochastic Competition and Predation". | 1 | Applied and Interdisciplinary Chemistry |
Azo compounds are organic compounds bearing the functional group diazenyl (, in which R and R′ can be either aryl or alkyl groups).
IUPAC defines azo compounds as: "Derivatives of diazene (diimide), , wherein both hydrogens are substituted by hydrocarbyl groups, e.g. azobenzene or diphenyldiazene.", where Ph stands for phenyl group. The more stable derivatives contain two aryl groups. The group is called an azo group (, ).
Many textile and leather articles are dyed with azo dyes and pigments. | 0 | Theoretical and Fundamental Chemistry |
Charles M. Schwab (1862–1939) and Eugene Grace (1876–1960) made Bethlehem Steel the second-largest American steel company by the 1920s. Schwab had been the operating head of Carnegie Steel and US Steel. In 1903 he purchased the small firm Bethlehem Steel, and in 1916 made Grace president. Innovation was the keynote at a time when U.S. Steel under Judge Elbert Henry Gary moved slowly. Bethlehem concentrated on government contracts, such as ships and naval armor, and on construction beams, especially for skyscrapers and bridges. Its subsidiary Bethlehem Shipbuilding Corporation operated 15 shipyards in World War II. It produced 1,121 ships, more than any other builder during the war and nearly one-fifth of the U.S. Navy's fleet. Its peak employment was 180,000 workers, out of a company-wide wartime peak of 300,000. After 1945 Bethlehem doubled its steel capacity, a measure of the widespread optimism in the industry. However the company ignored the new technologies then being developed in Europe and Japan. Seeking labor peace in order to avoid strikes, Bethlehem like the other majors agreed to large wage and benefits increases that kept its costs high. After Grace retired the executives concentrated on short term profits and postponed innovations that led to long-term inefficiency. It went bankrupt in 2001. | 1 | Applied and Interdisciplinary Chemistry |
The history of alchemy has become a recognized subject of academic study. As the language of the alchemists is analysed, historians are becoming more aware of the connections between that discipline and other facets of Western cultural history, such as the evolution of science and philosophy, the sociology and psychology of the intellectual communities, kabbalism, spiritualism, Rosicrucianism, and other mystic movements. Institutions involved in this research include The Chymistry of Isaac Newton project at Indiana University, the University of Exeter Centre for the Study of Esotericism (EXESESO), the European Society for the Study of Western Esotericism (ESSWE), and the University of Amsterdam's Sub-department for the History of Hermetic Philosophy and Related Currents. A large collection of books on alchemy is kept in the Bibliotheca Philosophica Hermetica in Amsterdam.
Journals which publish regularly on the topic of Alchemy include Ambix, published by the Society for the History of Alchemy and Chemistry, and Isis, published by the History of Science Society. | 1 | Applied and Interdisciplinary Chemistry |
The STRENDA project is driven by 15 scientists from all over the world forming the STRENDA Commission and supporting the work with expertises in biochemistry, [https://www.qmul.ac.uk/sbcs/iubmb/enzyme/ enzyme nomenclature], bioinformatics, systems biology, modelling, mechanistic enzymology and theoretical biology. | 1 | Applied and Interdisciplinary Chemistry |
When there is enough matter in a region to allow molecular collisions to occur very much more often than absorption or emission of photons, for radiation one speaks of local thermodynamic equilibrium (LTE). In this case, Kirchhoff's law of equality of radiative absorptivity and emissivity holds.
Two bodies in radiative exchange equilibrium, each in its own local thermodynamic equilibrium, have the same temperature and their radiative exchange complies with the Stokes-Helmholtz reciprocity principle. | 0 | Theoretical and Fundamental Chemistry |
When the distance between the probe and the sample is brought to the range where atomic force may be detected, while a cantilever is excited in its natural eigenfrequency (f), the resonance frequency f of the cantilever may shift from its original resonance frequency. In other words, in the range where atomic force may be detected, a frequency shift (df =f–f) will also be observed. When the distance between the probe and the sample is in the non-contact region, the frequency shift increases in negative direction as the distance between the probe and the sample gets smaller.
When the sample has concavity and convexity, the distance between the tip-apex and the sample varies in accordance with the concavity and convexity accompanied with a scan of the sample along x–y direction (without height regulation in z-direction). As a result, the frequency shift arises. The image in which the values of the frequency obtained by a raster scan along the x–y direction of the sample surface are plotted against the x–y coordination of each measurement point is called a constant-height image.
On the other hand, the df may be kept constant by moving the probe upward and downward (See (3) of FIG.5) in z-direction using a negative feedback (by using z-feedback loop) while the raster scan of the sample surface along the x–y direction. The image in which the amounts of the negative feedback (the moving distance of the probe upward and downward in z-direction) are plotted against the x–y coordination of each measurement point is a topographic image. In other words, the topographic image is a trace of the tip of the probe regulated so that the df is constant and it may also be considered to be a plot of a constant-height surface of the df.
Therefore, the topographic image of the AFM is not the exact surface morphology itself, but actually the image influenced by the bond-order between the probe and the sample, however, the topographic image of the AFM is considered to reflect the geographical shape of the surface more than the topographic image of a scanning tunnel microscope. | 0 | Theoretical and Fundamental Chemistry |
Adaptive management is a key aspect of ESEM. Adaptive management is a way of approaching environmental management. It assumes that there is a great deal of uncertainty in environmental systems and holds that there is never a final solution to an earth systems problem. Therefore, once action has been taken, the Earth Systems Engineer will need to be in constant dialogue with the system, watching for changes and how the system evolves. This way of monitoring and managing ecosystems accepts nature's inherent uncertainty and embraces it by never concluding to one certain cure to a problem. | 1 | Applied and Interdisciplinary Chemistry |
The thermal copper pillar bump, also known as the "thermal bump", is a thermoelectric device made from thin-film thermoelectric material embedded in flip chip interconnects (in particular copper pillar solder bumps) for use in electronics and optoelectronic packaging, including: flip chip packaging of CPU and GPU integrated circuits (chips), laser diodes, and semiconductor optical amplifiers (SOA). Unlike conventional solder bumps that provide an electrical path and a mechanical connection to the package, thermal bumps act as solid-state heat pumps and add thermal management functionality locally on the surface of a chip or to another electrical component. The diameter of a thermal bump is 238 μm and 60 μm high.
The thermal bump uses the thermoelectric effect, which is the direct conversion of temperature differences to electric voltage and vice versa. Simply put, a thermoelectric device creates a voltage when there is a different temperature on each side, or when a voltage is applied to it, it creates a temperature difference. This effect can be used to generate electricity, to measure temperature, to cool objects, or to heat them.
For each bump, thermoelectric cooling (TEC) occurs when a current is passed through the bump. The thermal bump pulls heat from one side of the device and transfers it to the other as current is passed through the material. This is known as the Peltier effect. The direction of heating and cooling is determined by the direction of current flow and the sign of the majority electrical carrier in the thermoelectric material. Thermoelectric power generation (TEG) on the other hand occurs when the thermal bump is subjected to a temperature gradient (i.e., the top is hotter than the bottom). In this instance, the device generates current, converting heat into electrical power. This is termed the Seebeck effect.
The thermal bump was developed by Nextreme Thermal Solutions as a method for integrating active thermal management functionality at the chip level in the same manner that transistors, resistors and capacitors are integrated in conventional circuit designs today. Nextreme chose the copper pillar bump as an integration strategy due to its widespread acceptance by Intel, Amkor and other industry leaders as the method for connecting microprocessors and other advanced electronics devices to various surfaces during a process referred to as “flip-chip” packaging. The thermal bump can be integrated as a part of the standard flip-chip process (Figure 1) or integrated as discrete devices.
The efficiency of a thermoelectric device is measured by the heat moved (or pumped) divided by the amount of electrical power supplied to move this heat. This ratio is termed the coefficient of performance or COP and is a measured characteristic of a thermoelectric device. The COP is inversely related to the temperature difference that the device produces. As you move a cooling device further away from the heat source, parasitic losses between the cooler and the heat source necessitate additional cooling power: the further the distance between source and cooler, the more cooling is required. For this reason, the cooling of electronic devices is most efficient when it occurs closest to the source of the heat generation.
Use of the thermal bump does not displace system level cooling, which is still needed to move heat out of the system; rather it introduces a fundamentally new methodology for achieving temperature uniformity at the chip and board level. In this manner, overall thermal management of the system becomes more efficient. In addition, while conventional cooling solutions scale with the size of the system (bigger fans for bigger systems, etc.), the thermal bump can scale at the chip level by using more thermal bumps in the overall design. | 0 | Theoretical and Fundamental Chemistry |
The protocol is based on the fact that the formaldehyde cross-linking is more efficient in nucleosome-bound DNA than it is in nucleosome-depleted regions of the genome. This method then segregates the non cross-linked DNA that is usually found in open chromatin, which is then sequenced. The protocol consists of cross linking, phenol extraction and sequencing the DNA in aqueous phase. | 1 | Applied and Interdisciplinary Chemistry |
The softening point is the temperature at which a material softens beyond some arbitrary softness. It can be determined, for example, by the Vicat method (ASTM-D1525 or ISO 306), Heat Deflection Test (ASTM-D648) or a ring and ball method (ISO 4625 or ASTM E28-67/E28-99 or ASTM D36 or ASTM D6493 - 11 or JIS K 6863). A ring and ball apparatus can also be used for the determination of softening point of bituminous materials. | 0 | Theoretical and Fundamental Chemistry |
The oil and gas industry is usually divided into three major sectors: upstream, midstream, and downstream. The downstream sector is the refining of petroleum crude oil and the processing and purifying of raw natural gas, as well as the marketing and distribution of products derived from crude oil and natural gas. The downstream sector reaches consumers through products such as gasoline or petrol, kerosene, jet fuel, diesel oil, heating oil, fuel oils, lubricants, waxes, asphalt, natural gas, and liquefied petroleum gas (LPG) as well as naphtha and hundreds of petrochemicals.
Midstream operations are often included in the downstream category and are considered to be a part of the downstream sector. | 1 | Applied and Interdisciplinary Chemistry |
Dendrimers are particularly versatile drug delivery devices due to the wide range of chemical modifications that can be made to increase in vivo suitability and allow for site-specific targeted drug delivery.
Drug attachment to the dendrimer may be accomplished by (1) a covalent attachment or conjugation to the external surface of the dendrimer forming a dendrimer prodrug, (2) ionic coordination to charged outer functional groups, or (3) micelle-like encapsulation of a drug via a dendrimer-drug supramolecular assembly. In the case of a dendrimer prodrug structure, linking of a drug to a dendrimer may be direct or linker-mediated depending on desired release kinetics. Such a linker may be pH-sensitive, enzyme catalyzed, or a disulfide bridge. The wide range of terminal functional groups available for dendrimers allows for many different types of linker chemistries, providing yet another tunable component on the system. Key parameters to consider for linker chemistry are (1) release mechanism upon arrival to the target site, whether that be within the cell or in a certain organ system, (2) drug-dendrimer spacing so as to prevent lipophilic drugs from folding into the dendrimer, and (3) linker degradability and post-release trace modifications on drugs.
Polyethylene glycol (PEG) is a common modification for dendrimers to modify their surface charge and circulation time. Surface charge can influence the interactions of dendrimers with biological systems, such as amine-terminal modified dendrimers which have a propensity to interact with cell membranes with anionic charge. Certain in vivo studies have shown polycationic dendrimers to be cytotoxic through membrane permeabilization, a phenomenon that could be partially mitigated via addition of PEGylation caps on amine groups, resulting in lower cytotoxicity and lower red blood cell hemolysis. Additionally, studies have found that PEGylation of dendrimers results in higher drug loading, slower drug release, longer circulation times in vivo, and lower toxicity in comparison to counterparts without PEG modifications.
Numerous targeting moieties have been used to modify dendrimer biodistribution and allow for targeting to specific organs. For example, folate receptors are overexpressed in tumor cells and are therefore promising targets for localized drug delivery of chemotherapeutics. Folic acid conjugation to PAMAM dendrimers has been shown to increase targeting and decrease off-target toxicity while maintaining on-target cytotoxicity of chemotherapeutics such as methotrexate, in mouse models of cancer.
Antibody-mediated targeting of dendrimers to cell targets has also shown promise for targeted drug delivery. As epidermal growth factor receptors (EGFRs) are often overexpressed in brain tumors, EGFRs are a convenient target for site-specific drug delivery. The delivery of boron to cancerous cells is important for effective neutron capture therapy, a cancer treatment which requires a large concentration of boron in cancerous cells and a low concentration in healthy cells. A boronated dendrimer conjugated with a monoclonal antibody drug that targets EGFRs was used in rats to successfully deliver boron to cancerous cells.
Modifying nanoparticle dendrimers with peptides has also been successful for targeted destruction of colorectal (HCT-116) cancer cells in a co-culture scenario. Targeting peptides can be used to achieve site- or cell-specific delivery, and it has been shown that these peptides increase in targeting specificity when paired with dendrimers. Specifically, gemcitabine-loaded YIGSR-CMCht/PAMAM, a unique kind of dendrimer nanoparticle, induces a targeted mortality on these cancer cells. This is performed via selective interaction of the dendrimer with laminin receptors. Peptide dendrimers may be employed in the future to precisely target cancer cells and deliver chemotherapeutic agents.
The cellular uptake mechanism of dendrimers can also be tuned using chemical targeting modifications. Non-modified PAMAM-G4 dendrimer is taken up into activated microglia by fluid phase endocytosis. Conversely, mannose modification of hydroxyl PAMAM-G4 dendrimers was able to change the mechanism of internalization to mannose-receptor (CD206) mediated endocytosis. Additionally, mannose modification was able to change the biodistribution in the rest of the body in rabbits. | 0 | Theoretical and Fundamental Chemistry |
Steric hindrance is a consequence of steric effects. Steric hindrance is the slowing of chemical reactions due to steric bulk. It is usually manifested in intermolecular reactions, whereas discussion of steric effects often focus on intramolecular interactions. Steric hindrance is often exploited to control selectivity, such as slowing unwanted side-reactions.
Steric hindrance between adjacent groups can also affect torsional bond angles. Steric hindrance is responsible for the observed shape of rotaxanes and the low rates of racemization of 2,2'-disubstituted biphenyl and binaphthyl derivatives. | 0 | Theoretical and Fundamental Chemistry |
Next-generation sequencing has enabled a genome-wide approach to identify DNA footprints. Open chromatin assays such as DNase-Seq and FAIRE-Seq have proven to provide a robust regulatory landscape for many cell types. However, these assays require some downstream bioinformatics analyses in order to provide genome-wide DNA footprints. The computational tools proposed can be categorized in two classes: segmentation-based and site-centric approaches.
Segmentation-based methods are based on the application of Hidden Markov models or sliding window methods to segment the genome into open/closed chromatin region. Examples of such methods are: HINT, Boyle method and Neph method. Site-centric methods, on the other hand, find footprints given the open chromatin profile around motif-predicted binding sites, i.e., regulatory regions predicted using DNA-protein sequence information (encoded in structures such as position weight matrix). Examples of these methods are CENTIPEDE and Cuellar-Partida method. | 1 | Applied and Interdisciplinary Chemistry |
During plant photosynthesis, 2 equivalents of glycerate 3-phosphate (GP; also known as 3-phosphoglycerate) are produced by the first step of the light-independent reactions when ribulose 1,5-bisphosphate (RuBP) and carbon dioxide are catalysed by the rubisco enzyme. The GP is converted to D-glyceraldehyde 3-phosphate (G3P) using the energy in ATP and the reducing power of NADPH as part of the Calvin cycle. This returns ADP, phosphate ions Pi, and NADP+ to the light-dependent reactions of photosynthesis for their continued function.
RuBP is regenerated for the Calvin cycle to continue.
G3P is generally considered the prime end-product of photosynthesis and it can be used as an immediate food nutrient, combined and rearranged to form monosaccharide sugars, such as glucose, which can be transported to other cells, or packaged for storage as insoluble polysaccharides such as starch. | 0 | Theoretical and Fundamental Chemistry |
Pharmaceuticals:
This technique is widely used in the pharma market. Because of the small sample amounts and the high yields, it is ideal for spray drying expensive substances in basic research. The following list shows examples of what is possible:
*Inhalable drugs for dry powder inhalers (DPI‘s)
*Nano- and microencapsulation of liposomes
*Stabilization of heat-sensitive vaccines, insulin, growth hormones
*Encapsulation of nanoparticle drugs for high bioavailability
*Nanocapsules of biodegradable polymers (lactides, glycolides)
*Porous drug carriers for nanoparticle suspensions
*Excipients for controlled drug release studies: trehalose, mannitol, lactose, HPMC, PVA, chitosan, dextrin, PLGA, starch, gelatin
Materials science:
This new technique offers new prospects in materials science, specially in the nanomaterial field. Now it is possible to spray dry fine particles. The following list shows examples of what is possible:
*Fine metal particles for novel catalysts
*Fine magnetic powders
*Carbon nanotubes as additives
*High performance ceramics with novel structures and high specific surface area
*Titanium oxide particles
*Nanoparticle suspensions for agglomeration
*Silicon oxide nanoparticle agglomerates
*Finest pigments for paints and coatings
Food:
Also in the field of food science this technology offers new possibilities. Especially in the currently vibrant field of functional food, the following list shows examples of what is possible:
*Nano food – Functional additives
*Encapsulation of fruit aromas, flavours, or perfumes
*Spray drying of fine powder aromas for pet food
*Encapsulation of fish oil for smell protection
*Vitamins, other food additives, etc. | 0 | Theoretical and Fundamental Chemistry |
Arsenic removal technologies are traditional treatment processes which have been tailored to improve removal of arsenic from drinking water. Although some of the removal processes, such as precipitative processes, adsorption processes, ion exchange processes, and separation (membrane) processes, may be technically feasible, their cost may be prohibitive.
For underdeveloped countries, the challenge is finding the means to fund such technologies. The Environmental Protection Agency, for example, has estimated the total national annualized cost of treatment, monitoring, reporting, record keeping, and administration to enforce the MCL rule to be approximately $181 million. Most of the cost is due to the installation and operation of the treatment technologies needed to reduce arsenic in public water systems. | 1 | Applied and Interdisciplinary Chemistry |
Thiols, or more specific their conjugate bases, are readily alkylated to give sulfides:
:RSH + R′Br + B → RSR′ + [HB]Br (B = base) | 0 | Theoretical and Fundamental Chemistry |
Prostaglandins are derived from the parent molecule arachidonic acid. The synthesis of prostaglandins can be blocked by anti-inflammatory drugs such as ibuprofen. Anti-inflammatory drugs block the synthesis of cyclooxygenases which in turn produce prostaglandins. Prostaglandins (PG) are the result of an enzyme cascade pathway that includes two enzymes cyclooxygenase and PG synthase. Prostaglandin E2 is produced by PGE synthase via the activation of EP1-4 receptors. Prostaglandin E2s (PGEs) are associated with the development of vascular diseases that lead to inflammation in the body. In the human body, PGEs are involved in the control of the vascular smooth muscle, cell migration and the division of a cell into two daughter cells. The process of producing two daughter cells via cell division is called cell proliferation. | 1 | Applied and Interdisciplinary Chemistry |
The two major species of deer found in North America are the white-tailed deer (Odocoileus virginianus) and the mule deer (Odocoileus hemionus). The most important sense in these animals is olfaction (the sense of smell)—so much so that they have an accessory olfaction system.
The vomeronasal organ, located at the base of the nasal cavity, is the sensory organ for this system. Besides locating food and water, deer rely on their two separate olfactory systems to detect the presence of predators, as well as to supply them with information about the identity, sex, dominance status and reproductive status of other deer.
The preorbital gland of O. virginianus is about in length, while that of O. hemionus is roughly in length. In black-tailed deer (O. h. columbianus), a subspecies of O. hemionus, the preorbital gland measures about . In all of these animals, the preorbital glands are surrounded by muscle which is under voluntary control, at least to some extent.
It is not entirely clear whether the preorbital gland secretions of North American deer are significant for chemical communication. Most of the time the glands remain closed, but deer are capable of opening them to emit an odor in certain circumstances. For example, a rutting male may dilate its preorbital glands in order to signal aggression to another nearby male. Female deer often open their glands while caring for their young. | 1 | Applied and Interdisciplinary Chemistry |
In the canonical pathway, Wnt proteins binds to its transmembrane receptor of the Frizzled family of proteins. The binding of Wnt to a Frizzled protein activates the Dishevelled protein. In its active state the Dishevelled protein inhibits the activity of the glycogen synthase kinase 3 (GSK3) enzyme. Normally active GSK3 prevents the dissociation of β-catenin to the APC protein, which results in β-catenin degradation. Thus inhibited GSK3, allows β-catenin to dissociate from APC, accumulate, and travel to nucleus. In the nucleus β-catenin associates with Lef/Tcf transcription factor, which is already working on DNA as a repressor, inhibiting the transcription of the genes it binds. Binding of β-catenin to Lef/Tcf works as a transcription activator, activating the transcription of the Wnt-responsive genes. | 1 | Applied and Interdisciplinary Chemistry |
Since 1990 the number of European producers has been declining. The French SNPE factory closed in 1990; in 1993, the production of hexamethylenetetramine in Leuna, Germany ceased; in 1996, the Italian facility of Agrolinz closed down; in 2001, the UK producer Borden closed; in 2006, production at Chemko, Slovak Republic, was closed. Remaining producers include INEOS in Germany, Caldic in the Netherlands, and Hexion in Italy. In the US, Eli Lilly and Company stopped producing methenamine tablets in 2002. In Australia, Hexamine Tablets for fuel are made by Thales Australia Ltd. In México, Hexamine is produced by Abiya. | 0 | Theoretical and Fundamental Chemistry |
The ratio of activities of a solute, A in an aqueous/organic system will remain constant and independent of the total quantity of A (hence ), so at any given temperature:
Distribution constants are useful as they allow the calculation of the concentration of remaining analyte in the solution, even after a number of solvent extractions have occurred. They also provide guidance in choosing the most efficient way to conduct an extractive separation.
Thus, the concentration of A remaining in an aqueous solution after i extractions with an organic solvent can be found using:
(where [A] is the concentration of A remaining after extracting V millilitres of solution with the original concentration of [A] with i portions of the organic solvent, each with a volume of V). | 0 | Theoretical and Fundamental Chemistry |
The Karlsruhe Congress was called so that European chemists could discuss matters of chemical nomenclature, notation, and atomic weights. The organization, invitation, and sponsorship of the conference were handled by August Kekulé, Adolphe Wurtz, and Karl Weltzien. As an example of the problems facing the delegates, Kekulés Lehrbuch der Organischen Chemie' gave nineteen different formulas used by chemists for acetic acid, as shown in the figure on this page.
An understanding was reached on the time and place of the meeting, and printing of a circular addressed to European chemists listed below, which explained the objectives and goals of an international congress was agreed upon. The circular concluded: "...with the aim of avoiding any unfortunate omissions, the undersigned request that the individuals to whom this circular will be sent please communicate it to their scientist friends who are duly authorized to attend the planned conference."
The circular of the conference was sent to:
Of the above, only 20 of 45 attended. | 1 | Applied and Interdisciplinary Chemistry |
A reduced form of phenolphthalein, phenolphthalin, which is colorless, is used in a test to identify substances thought to contain blood, commonly known as the Kastle–Meyer test. A dry sample is collected with a swab or filter paper. A few drops of alcohol, then a few drops of phenolphthalin, and finally a few drops of hydrogen peroxide are dripped onto the sample. If the sample contains hemoglobin, it will turn pink immediately upon addition of the peroxide, because of the generation of phenolphthalein. A positive test indicates the sample contains hemoglobin and, therefore, is likely blood. A false positive can result from the presence of substances with catalytic activity similar to hemoglobin. This test is not destructive to the sample; it can be kept and used in further tests. This test has the same reaction with blood from any animal whose blood contains hemoglobin, including almost all vertebrates; further testing would be required to determine whether it originated from a human. | 0 | Theoretical and Fundamental Chemistry |
Flap endonuclease 1 (FEN1) is responsible for processing Okazaki fragments. It works with DNA polymerase to remove the RNA primer of an Okazaki fragment and can remove the 5 ribonucleotide and 5 flaps when DNA polymerase displaces the strands during lagging strand synthesis. The removal of these flaps involves a process called nick translation and creates a nick for ligation. Thus, FEN1's function is necessary to Okazaki fragment maturation in forming a long continuous DNA strand. Likewise, during DNA base repair, the damaged nucleotide is displaced into a flap and subsequently removed by FEN1. | 1 | Applied and Interdisciplinary Chemistry |
The structures of both eukaryotic and prokaryotic genes involve several nested sequence elements. Each element has a specific function in the multi-step process of gene expression. The sequences and lengths of these elements vary, but the same general functions are present in most genes. Although DNA is a double-stranded molecule, typically only one of the strands encodes information that the RNA polymerase reads to produce protein-coding mRNA or non-coding RNA. This sense or coding strand, runs in the 5 to 3 direction where the numbers refer to the carbon atoms of the backbone's ribose sugar. The open reading frame (ORF) of a gene is therefore usually represented as an arrow indicating the direction in which the sense strand is read.
Regulatory sequences are located at the extremities of genes. These sequence regions can either be next to the transcribed region (the promoter) or separated by many kilobases (enhancers and silencers). The promoter is located at the 5' end of the gene and is composed of a core promoter sequence and a proximal promoter sequence. The core promoter marks the start site for transcription by binding RNA polymerase and other proteins necessary for copying DNA to RNA. The proximal promoter region binds transcription factors that modify the affinity of the core promoter for RNA polymerase. Genes may be regulated by multiple enhancer and silencer sequences that further modify the activity of promoters by binding activator or repressor proteins. Enhancers and silencers may be distantly located from the gene, many thousands of base pairs away. The binding of different transcription factors, therefore, regulates the rate of transcription initiation at different times and in different cells.
Regulatory elements can overlap one another, with a section of DNA able to interact with many competing activators and repressors as well as RNA polymerase. For example, some repressor proteins can bind to the core promoter to prevent polymerase binding. For genes with multiple regulatory sequences, the rate of transcription is the product of all of the elements combined. Binding of activators and repressors to multiple regulatory sequences has a cooperative effect on transcription initiation.
Although all organisms use both transcriptional activators and repressors, eukaryotic genes are said to be default off, whereas prokaryotic genes are default on. The core promoter of eukaryotic genes typically requires additional activation by promoter elements for expression to occur. The core promoter of prokaryotic genes, conversely, is sufficient for strong expression and is regulated by repressors.
An additional layer of regulation occurs for protein coding genes after the mRNA has been processed to prepare it for translation to protein. Only the region between the start and stop codons encodes the final protein product. The flanking untranslated regions (UTRs) contain further regulatory sequences. The 3' UTR contains a terminator sequence, which marks the endpoint for transcription and releases the RNA polymerase. The 5’ UTR binds the ribosome, which translates the protein-coding region into a string of amino acids that fold to form the final protein product. In the case of genes for non-coding RNAs, the RNA is not translated but instead folds to be directly functional. | 1 | Applied and Interdisciplinary Chemistry |
Sepro Tyre Driven Grinding Mills are designed for small and medium capacity grinding applications, specifically small tonnage plants, regrinding mills, reagent prep and lime slaking. Sepro Pneumatic Tyre Driven (PTD) mills provide an alternative to standard trunnion drive systems. The drive consists of multiple gears boxes and electric motors directly connected and controlled through an AC variable frequency drive. Shell supported mills such as the Sepro PTD mills minimize stress on the mill shell by spreading the power drive over the full length of the mill. Sepro Mills are suitable for ball, rod and pebble charges and are available with overflow or grate discharge to suit the application. Shell supported mills such as the Sepro PTD Grinding Mills minimize stress on the shell by spreading the power drive over the full length of the unit. | 1 | Applied and Interdisciplinary Chemistry |
A phase-change material (PCM) is a substance which releases/absorbs sufficient energy at phase transition to provide useful heat or cooling. Generally the transition will be from one of the first two fundamental states of matter - solid and liquid - to the other. The phase transition may also be between non-classical states of matter, such as the conformity of crystals, where the material goes from conforming to one crystalline structure to conforming to another, which may be a higher or lower energy state.
The energy released/absorbed by phase transition from solid to liquid, or vice versa, the heat of fusion is generally much higher than the sensible heat. Ice, for example, requires 333.55 J/g to melt, but then water will rise one degree further with the addition of just 4.18 J/g. Water/ice is therefore a very useful phase change material and has been used to store winter cold to cool buildings in summer since at least the time of the Achaemenid Empire.
By melting and solidifying at the phase-change temperature (PCT), a PCM is capable of storing and releasing large amounts of energy compared to sensible heat storage. Heat is absorbed or released when the material changes from solid to liquid and vice versa or when the internal structure of the material changes; PCMs are accordingly referred to as latent heat storage (LHS) materials.
There are two principal classes of phase-change material: organic (carbon-containing) materials derived either from petroleum, from plants or from animals; and salt hydrates, which generally either use natural salts from the sea or from mineral deposits or are by-products of other processes. A third class is solid to solid phase change.
PCMs are used in many different commercial applications where energy storage and/or stable temperatures are required, including, among others, heating pads, cooling for telephone switching boxes, and clothing.
By far the biggest potential market is for building heating and cooling. In this application area, PCMs hold potential in light of the progressive reduction in the cost of renewable electricity, coupled with the intermittent nature of such electricity. This can result in a misfit between peak demand and availability of supply. In North America, China, Japan, Australia, Southern Europe and other developed countries with hot summers, peak supply is at midday while peak demand is from around 17:00 to 20:00. This creates opportunities for thermal storage media.
Solid-liquid phase-change materials are usually encapsulated for installation in the end application, to contain in the liquid state. In some applications, especially when incorporation to textiles is required, phase change materials are micro-encapsulated. Micro-encapsulation allows the material to remain solid, in the form of small bubbles, when the PCM core has melted. | 0 | Theoretical and Fundamental Chemistry |
The tendency of a boundary layer to separate primarily depends on the distribution of the adverse or negative
edge velocity gradient along the surface, which in turn is directly related to the pressure and its gradient by the differential form of the Bernoulli relation,
which is the same as the momentum equation for the outer inviscid flow.
But the general magnitudes of required for separation are much greater for turbulent than for laminar flow, the former being able to tolerate nearly an order of magnitude stronger flow deceleration. A secondary influence is the Reynolds number. For a given adverse distribution, the separation resistance of a turbulent boundary layer increases slightly with increasing Reynolds number. In contrast, the separation resistance of a laminar boundary layer is independent of Reynolds number — a somewhat counterintuitive fact. | 1 | Applied and Interdisciplinary Chemistry |
The reversibility of the interconversion of 3-sulfolene with buta-1,3-diene and sulfur dioxide suggests the use of sulfolene as a recyclable aprotic dipolar solvent, in replacement for dimethyl sulfoxide (DMSO), which is often used but difficult to separate and poorly reusable. As a model reaction, the reaction of benzyl azide with 4-toluenesulfonic acid cyanide forming 1-benzyl-5-(4-toluenesulfonyl)tetrazole was investigated. The formation of the tetrazole can also be carried out as a one-pot reaction without the isolation of the benzyl azide with 72% overall yield.
After the reaction, the solvent 3-sulfolene is decomposed at 135 °C and the volatile butadiene (b.p. −4.4 °C) and sulfur dioxide (b.p. −10.1 °C) are deposited in a cooling trap at −76 °C charged with excess sulfur dioxide. After the addition of hydroquinone as polymerization inhibition, 3-sulfoles is formed again quantitatively upon heating to room temperature. It appears questionable though, if 3-sulfolene with a useful liquid phase range of only 64 to a maximum of about 100 °C can be used as DMSO substitutes (easy handling, low cost, environmental compatibility) in industrial practice. | 0 | Theoretical and Fundamental Chemistry |
Bores occur in relatively few locations worldwide, usually in areas with a large tidal range (typically more than between high and low tide) and where incoming tides are funneled into a shallow, narrowing river or lake via a broad bay. The funnel-like shape not only increases the tidal range, but it can also decrease the duration of the flood tide, down to a point where the flood appears as a sudden increase in the water level. A tidal bore takes place during the flood tide and never during the ebb tide.
A tidal bore may take on various forms, ranging from a single breaking wavefront with a roller – somewhat like a hydraulic jump – to undular bores, comprising a smooth wavefront followed by a train of secondary waves known as whelps. Large bores can be particularly unsafe for shipping but also present opportunities for river surfing.
Two key features of a tidal bore are the intense turbulence and turbulent mixing generated during the bore propagation, as well as its rumbling noise. The visual observations of tidal bores highlight the turbulent nature of the surging waters. The tidal bore induces a strong turbulent mixing in the estuarine zone, and the effects may be felt along considerable distances. The velocity observations indicate a rapid deceleration of the flow associated with the passage of the bore as well as large velocity fluctuations. A tidal bore creates a powerful roar that combines the sounds caused by the turbulence in the bore front and whelps, entrained air bubbles in the bore roller, sediment erosion beneath the bore front and of the banks, scouring of shoals and bars, and impacts on obstacles. The bore rumble is heard far away because its low frequencies can travel over long distances. The low-frequency sound is a characteristic feature of the advancing roller in which the air bubbles entrapped in the large-scale eddies are acoustically active and play the dominant role in the rumble-sound generation. | 1 | Applied and Interdisciplinary Chemistry |
Oscar Paul Kuipers (Rotterdam, May 12, 1956) is a Dutch professor of molecular genetics at the University of Groningen. His areas of expertise include microbiology, biochemistry, molecular and cell biology, and biotechnology. | 0 | Theoretical and Fundamental Chemistry |
Fluid flow is measured with a wide variety of instruments. The venturi meter in the diagram on the left shows two columns of a measurement fluid at different heights. The height of each column of fluid is proportional to the pressure of the fluid. To demonstrate a classical measurement of pressure head, we could hypothetically replace the working fluid with another fluid having different physical properties.
For example, if the original fluid was water and we replaced it with mercury at the same pressure, we would expect to see a rather different value for pressure head. In fact the specific weight of water is 9.8 kN/m and the specific weight of mercury is 133 kN/m. So, for any particular measurement of pressure head, the height of a column of water will be about [133/9.8 = 13.6] 13.6 times taller than a column of mercury would be. So if a water column meter reads "13.6 cm HO", then an equivalent measurement is "1.00 cm Hg".
This example demonstrates why there is some confusion surrounding pressure head and its relationship to pressure. Scientists frequently use columns of water (or mercury) to measure pressure (manometric pressure measurement), since for a given fluid, pressure head is proportional to pressure. Measuring pressure in units of "mm of mercury" or "inches of water" makes sense for instrumentation, but these raw measurements of head must frequently be converted to more convenient pressure units using the equations above to solve for pressure.
In summary pressure head is a measurement of length, which can be converted to the units of pressure (force per unit area), as long as strict attention is paid to the density of the measurement fluid and the local value of g. | 1 | Applied and Interdisciplinary Chemistry |
*Protein, peptide, and DNA patterning
*Hydrogels
*Sol gels
*Conductive inks
*Lipids
*Silanes (liquid phase) written to glass or silicon | 1 | Applied and Interdisciplinary Chemistry |
The scientist was the first to draw attention to the special importance of studying the migration of relatively short-lived radioelements in the Earth's crust for solving general geological and geochemical problems (1926). V. G. Khlopin pointed out a number of questions of these disciplines, which imply solution by the proposed methods: determination of sequence in geological and geochemical processes, determination of absolute age of relatively young and very young geological formations, and a number of other thematic areas. Migrations of uranium and radium were subjected to experimental study. | 0 | Theoretical and Fundamental Chemistry |
Kutlu Özergin Ülgen is a Turkish biochemical engineer researching pharmacophore modelling to identify pharmacological chaperones used to treat infectious diseases, genetic diseases, and cancer. Ülgen is a professor in the department of chemical engineering at Boğaziçi University. | 1 | Applied and Interdisciplinary Chemistry |
Damage and subsequent dysfunction in mitochondria is an important factor in a range of human diseases due to their influence in cell metabolism. Mitochondrial disorders often present as neurological disorders, including autism. They can also manifest as myopathy, diabetes, multiple endocrinopathy, and a variety of other systemic disorders. Diseases caused by mutation in the mtDNA include Kearns–Sayre syndrome, MELAS syndrome and Lebers hereditary optic neuropathy. In the vast majority of cases, these diseases are transmitted by a female to her children, as the zygote derives its mitochondria and hence its mtDNA from the ovum. Diseases such as Kearns-Sayre syndrome, Pearson syndrome, and progressive external ophthalmoplegia are thought to be due to large-scale mtDNA rearrangements, whereas other diseases such as MELAS syndrome, Lebers hereditary optic neuropathy, MERRF syndrome, and others are due to point mutations in mtDNA.
It has also been reported that drug tolerant cancer cells have an increased number and size of mitochondria which suggested an increase in mitochondrial biogenesis. A 2022 study in Nature Nanotechnology has reported that cancer cells can hijack the mitochondria from immune cells via physical tunneling nanotubes.
In other diseases, defects in nuclear genes lead to dysfunction of mitochondrial proteins. This is the case in Friedreichs ataxia, hereditary spastic paraplegia, and Wilsons disease. These diseases are inherited in a dominance relationship, as applies to most other genetic diseases. A variety of disorders can be caused by nuclear mutations of oxidative phosphorylation enzymes, such as coenzyme Q10 deficiency and Barth syndrome. Environmental influences may interact with hereditary predispositions and cause mitochondrial disease. For example, there may be a link between pesticide exposure and the later onset of Parkinsons disease. Other pathologies with etiology involving mitochondrial dysfunction include schizophrenia, bipolar disorder, dementia, Alzheimers disease, Parkinson's disease, epilepsy, stroke, cardiovascular disease, chronic fatigue syndrome, retinitis pigmentosa, and diabetes mellitus.
Mitochondria-mediated oxidative stress plays a role in cardiomyopathy in type 2 diabetics. Increased fatty acid delivery to the heart increases fatty acid uptake by cardiomyocytes, resulting in increased fatty acid oxidation in these cells. This process increases the reducing equivalents available to the electron transport chain of the mitochondria, ultimately increasing reactive oxygen species (ROS) production. ROS increases uncoupling proteins (UCPs) and potentiate proton leakage through the adenine nucleotide translocator (ANT), the combination of which uncouples the mitochondria. Uncoupling then increases oxygen consumption by the mitochondria, compounding the increase in fatty acid oxidation. This creates a vicious cycle of uncoupling; furthermore, even though oxygen consumption increases, ATP synthesis does not increase proportionally because the mitochondria are uncoupled. Less ATP availability ultimately results in an energy deficit presenting as reduced cardiac efficiency and contractile dysfunction. To compound the problem, impaired sarcoplasmic reticulum calcium release and reduced mitochondrial reuptake limits peak cytosolic levels of the important signaling ion during muscle contraction. Decreased intra-mitochondrial calcium concentration increases dehydrogenase activation and ATP synthesis. So in addition to lower ATP synthesis due to fatty acid oxidation, ATP synthesis is impaired by poor calcium signaling as well, causing cardiac problems for diabetics.
Mitochondria also modulate processes such as testicular somatic cell development, spermatogonial stem cell differentiation, luminal acidification, testosterone production in testes, and more. Thus, dysfunction of mitochondria in spermatozoa can be a cause for infertility.
In efforts to combat mitochondrial disease, mitochondrial replacement therapy (MRT) has been developed. This form of in vitro fertilization uses donor mitochondria, which avoids the transmission of diseases caused by mutations of mitochondrial DNA. However, this therapy is still being researched and can introduce genetic modification, as well as safety concerns. These diseases are rare but can be extremely debilitating and progressive diseases, thus posing complex ethical questions for public policy. | 1 | Applied and Interdisciplinary Chemistry |
A 3–10% solution of potassium hydroxide (KOH) gives a color change in some species of mushrooms:
* In Agaricus, some species such as A. xanthodermus turn yellow with KOH, many have no reaction, and A. subrutilescens turns green.
* Distinctive change occurs for some species of Cortinarius and Boletes | 0 | Theoretical and Fundamental Chemistry |
Pinealon is a synthetic tripeptide of sequence (Glu-Asp-Arg) and purported geroprotector documented in the Russian scientific literature. | 1 | Applied and Interdisciplinary Chemistry |
Trifluoromethanesulfonic acid is produced industrially by electrochemical fluorination (ECF) of methanesulfonic acid:
The resulting CFSOF is hydrolyzed, and the resulting triflate salt is reprotonated. Alternatively, trifluoromethanesulfonic acid arises by oxidation of trifluoromethylsulfenyl chloride:
Triflic acid is purified by distillation from triflic anhydride. | 0 | Theoretical and Fundamental Chemistry |
Other bodies may define classes of reference material differently. WHO guidelines for biological reference materials provide the terms:
* Reference standards: materials that are used as calibrators in assays
* International biological measurement standard: a biological substance provided to enable the results of biological assay or immunological assay procedures to be expressed in the same way throughout the world
* Secondary reference standards: Reference standards calibrated against and traceable to primary WHO materials and intended for use in routine tests
* Reference reagent: a WHO reference standard, the activity of which is defined by WHO in terms of a unit
For chemical substances some pharmacopoeias use the WHO terms
* Primary chemical reference substance: a chemical reference substance ... whose value is accepted without requiring comparison to another chemical substance.
* Secondary chemical reference substance: substance whose characteristics are assigned and/or calibrated by comparison with a primary chemical reference substance.
The United States National Institute of Standards and Technology (NIST) uses the trade marked term Standard Reference Material (SRM) to denote a certified reference material that satisfies additional NIST-specific criteria. In addition, commercial producers adhering to criteria and protocols defined by NIST may use the trademark "NIST traceable reference material" to designate certified reference materials with a well-defined traceability linkage to existing NIST standards for chemical measurements. | 0 | Theoretical and Fundamental Chemistry |
The alternative oxidase (AOX) is an enzyme that forms part of the electron transport chain in mitochondria of different organisms. Proteins homologous to the mitochondrial oxidase and the related plastid terminal oxidase have also been identified in bacterial genomes.
The oxidase provides an alternative route for electrons passing through the electron transport chain to reduce oxygen. However, as several proton-pumping steps are bypassed in this alternative pathway, activation of the oxidase reduces ATP generation. This enzyme was first identified as a distinct oxidase pathway from cytochrome c oxidase as the alternative oxidase is resistant to inhibition by the poison cyanide. | 1 | Applied and Interdisciplinary Chemistry |
Stakeholder Program on Infant Formula and Adult Nutritionals program (SPIFAN) develops consensus-based standards and methods to make infant formula and adult nutritionals safer for babies and adults to consume. | 0 | Theoretical and Fundamental Chemistry |
Atmospheric carbon dioxide plays an integral role in the Earth's carbon cycle whereby is removed from the atmosphere by some natural processes such as photosynthesis and deposition of carbonates, to form limestones for example, and added back to the atmosphere by other natural processes such as respiration and the acid dissolution of carbonate deposits. There are two broad carbon cycles on Earth: the fast carbon cycle and the slow carbon cycle. The fast carbon cycle refers to movements of carbon between the environment and living things in the biosphere whereas the slow carbon cycle involves the movement of carbon between the atmosphere, oceans, soil, rocks, and volcanism. Both cycles are intrinsically interconnected and atmospheric facilitates the linkage.
Natural sources of atmospheric include volcanic outgassing, the combustion of organic matter, wildfires and the respiration processes of living aerobic organisms. Man-made sources of include the burning of fossil fuels for heating, power generation and transport, as well as some industrial processes such as cement making. It is also produced by various microorganisms from fermentation and cellular respiration. Plants, algae and cyanobacteria convert carbon dioxide to carbohydrates by a process called photosynthesis. They gain the energy needed for this reaction from absorption of sunlight by chlorophyll and other pigments. Oxygen, produced as a by-product of photosynthesis, is released into the atmosphere and subsequently used for respiration by heterotrophic organisms and other plants, forming a cycle with carbon.
Most sources of emissions are natural, and are balanced to various degrees by similar sinks. For example, the decay of organic material in forests, grasslands, and other land vegetation - including forest fires - results in the release of about 436 gigatonnes of (containing 119 gigatonnes carbon) every year, while uptake by new growth on land counteracts these releases, absorbing 451 Gt (123 Gt C). Although much in the early atmosphere of the young Earth was produced by volcanic activity, modern volcanic activity releases only 130 to 230 megatonnes of each year. Natural sources are more or less balanced by natural sinks, in the form of chemical and biological processes which remove from the atmosphere.
Overall, there is a large natural flux of atmospheric into and out of the biosphere, both on land and in the oceans. In the pre-industrial era, each of these fluxes were in balance to such a degree that little net flowed between the land and ocean reservoirs of carbon, and little change resulted in the atmospheric concentration. From the human pre-industrial era to 1940, the terrestrial biosphere represented a net source of atmospheric (driven largely by land-use changes), but subsequently switched to a net sink with growing fossil carbon emissions. In 2012, about 57% of human-emitted , mostly from the burning of fossil carbon, was taken up by land and ocean sinks.
The ratio of the increase in atmospheric to emitted is known as the airborne fraction. This ratio varies in the short-term and is typically about 45% over longer (5-year) periods. Estimated carbon in global terrestrial vegetation increased from approximately 740 gigatonnes in 1910 to 780 gigatonnes in 1990. | 1 | Applied and Interdisciplinary Chemistry |
Some methods first developed within nuclear chemistry and physics have become so widely used within chemistry and other physical sciences that they may be best thought of as separate from normal nuclear chemistry. For example, the isotope effect is used so extensively to investigate chemical mechanisms and the use of cosmogenic isotopes and long-lived unstable isotopes in geology that it is best to consider much of isotopic chemistry as separate from nuclear chemistry. | 0 | Theoretical and Fundamental Chemistry |
Gas molecules in soil are in continuous thermal motion according to the kinetic theory of gases, and there is also collision between molecules – a random walk process. In soil, a concentration gradient causes net movement of molecules from high concentration to low concentration, which gives the movement of gas by diffusion. Numerically, it is explained by the Fick's law of diffusion. Soil gas migration, specifically that of hydrocarbon species with one to five carbons, can also be caused by microseepage.
The soil atmosphere's variable composition and constant motion can be attributed to chemical processes such as diffusion, decomposition, and, in some regions of the world, thawing, among other processes. Diffusion of soil air with the atmosphere causes the preferential replacement of soil gases with atmospheric air. More significantly, moreover, variation in soil gas composition due to seasonal, or even daily, temperature and/or moisture change can influence the rate of soil respiration.
According to the USDA, soil respiration refers to the quantity of carbon dioxide released from soil. This excess carbon dioxide is created by the decomposition of organic material by microbial organisms, in the presence of oxygen. Given the importance of both soil gases to soil life, significant fluctuation of carbon dioxide and oxygen can result in changes in rate of decay, while changes in microbial abundance can inversely influence soil gas composition.
In regions of the world where freezing of soils or drought is common, soil thawing and rewetting due to seasonal or meteorological changes influences soil gas flux. Both processes hydrate the soil and increase nutrient availability leading to an increase in microbial activity. This results in greater soil respiration and influences the composition of soil gases. | 0 | Theoretical and Fundamental Chemistry |
Mitochondrial genes in some vertebrates (including humans) have incomplete stop codons ending in U or UA, which become complete termination codons (UAA) upon subsequent polyadenylation. | 1 | Applied and Interdisciplinary Chemistry |
Crampton et al. have proposed a mechanism for the ssDNA-dependent hydrolysis of dTTP by T7 DNA helicase as shown in the figure below. In their model, protein loops located on each hexameric subunit, each of which contain three lysine residues, sequentially interact with the negatively charged phosphate backbone of ssDNA. This interaction presumably causes a conformational change in the actively bound subunit, providing for the efficient release of dTDP from its dTTP binding site. In the process of dTDP release, the ssDNA is transferred to the neighboring subunit, which undergoes a similar process. Previous studies have already suggested that ssDNA is able to bind to two hexameric subunits simultaneously. | 1 | Applied and Interdisciplinary Chemistry |
When a second phase of mass fragmentation is added, for example using a second quadrupole in a quadrupole instrument, it is called tandem MS (MS/MS). MS/MS can sometimes be used to quantitate low levels of target compounds in the presence of a high sample matrix background.
The first quadrupole (Q1) is connected with a collision cell (Q2) and another quadrupole (Q3). Both quadrupoles can be used in scanning or static mode, depending on the type of MS/MS analysis being performed. Types of analysis include product ion scan, precursor ion scan, selected reaction monitoring (SRM) (sometimes referred to as multiple reaction monitoring (MRM)) and neutral loss scan. For example: When Q1 is in static mode (looking at one mass only as in SIM), and Q3 is in scanning mode, one obtains a so-called product ion spectrum (also called "daughter spectrum"). From this spectrum, one can select a prominent product ion which can be the product ion for the chosen precursor ion. The pair is called a "transition" and forms the basis for SRM. SRM is highly specific and virtually eliminates matrix background. | 0 | Theoretical and Fundamental Chemistry |
Dehydroretinal (3,4-dehydroretinal) is a derivative metabolite of retinal belonging to the group of vitamin A as a retinaldehyde form, besides the endogenously present 3,4-dehydroretinol and 3,4-dehydroretinoic acid.
The livers of some freshwater fishes and some fish found in India contain a higher ratio of dehydroretinal to retinal than do other species. | 1 | Applied and Interdisciplinary Chemistry |
An insulator is a type of cis-regulatory element known as a long-range regulatory element. Found in multicellular eukaryotes and working over distances from the promoter element of the target gene, an insulator is typically 300 bp to 2000 bp in length. Insulators contain clustered binding sites for sequence specific DNA-binding proteins and mediate intra- and inter-chromosomal interactions.
Insulators function either as an enhancer-blocker or a barrier, or both. The mechanisms by which an insulator performs these two functions include loop formation and nucleosome modifications. There are many examples of insulators, including the CTCF insulator, the gypsy insulator, and the β-globin locus. The CTCF insulator is especially important in vertebrates, while the gypsy insulator is implicated in Drosophila. The β-globin locus was first studied in chicken and then in humans for its insulator activity, both of which utilize CTCF.
The genetic implications of insulators lie in their involvement in a mechanism of imprinting and their ability to regulate transcription. Mutations to insulators are linked to cancer as a result of cell cycle disregulation, tumourigenesis, and silencing of growth suppressors. | 1 | Applied and Interdisciplinary Chemistry |
In NMR spectroscopy, the product operator formalism is a method used to determine the outcome of pulse sequences in a rigorous but straightforward way. With this method it is possible to predict how the bulk magnetization evolves with time under the action of pulses applied in different directions. It is a net improvement from the semi-classical vector model which is not able to predict many of the results in NMR spectroscopy and is a simplification of the complete density matrix formalism.
In this model, for a single spin, four base operators exist: , , and which represent respectively polarization (population difference between the two spin states), single quantum coherence (magnetization on the xy plane) and the unit operator. Many other, non-classical operators exist for coupled systems. Using this approach, the evolution of the magnetization under free precession is represented by and corresponds to a rotation about the z-axis with a phase angle proportional to the chemical shift of the spin in question:
Pulses about the x and y axis can be represented by and respectively; these allow to interconvert the magnetization between planes and ultimately to observe it at the end of a sequence. Since every spin will evolve differently depending on its shift, with this formalism it is possible to calculate exactly where the magnetization will end up and hence devise pulse sequences to measure the desired signal while excluding others.
The product operator formalism is particularly useful in describing experiments in two-dimensions like COSY, HSQC and HMBC. | 0 | Theoretical and Fundamental Chemistry |
Metal acyl complexes participate in several commercial processes, including:
*hydroformylation
*acetic acid synthesis
*Eastman acetic anhydride process
*Ethylene-carbon monoxide copolymerization
A reaction involving metal acyl complexes of occasional value in organic synthesis is the Tsuji–Wilkinson decarbonylation reaction of aldehydes. | 0 | Theoretical and Fundamental Chemistry |
The Folin–Ciocâlteu reagent (FCR) or Folins phenol reagent or Folin–Denis reagent, is a mixture of phosphomolybdate and phosphotungstate used for the colorimetric in vitro' assay of phenolic and polyphenolic antioxidants, also called the gallic acid equivalence method (GAE). It is named after Otto Folin, Vintilă Ciocâlteu, and Willey Glover Denis. The Folin-Denis reagent is prepared by mixing sodium tungstate and phosphomolybdic acid in phosphoric acid. The Folin–Ciocalteu reagent is just a modification of the Folin-Denis reagent. The modification consisted of the addition of lithium sulfate and bromine to the phosphotungstic-phosphomolybdic reagent.
The reagent does not measure only phenols, but will react with any reducing substance. It therefore measures the total reducing capacity of a sample, not just phenolic compounds. This reagent is part of the Lowry protein assay, and will also react with some nitrogen-containing compounds such as hydroxylamine and guanidine. The reagent has also been shown to be reactive towards thiols, many vitamins, the nucleotide base guanine, the trioses glyceraldehyde and dihydroxyacetone, and some inorganic ions. Copper complexation increases the reactivity of phenols towards this reagent.
This reagent is distinct from Folin's reagent, which is used to detect amines and sulfur-containing compounds.
A 1951 paper entitled "Protein measurement with the Folin phenol reagent" was the most cited paper in the 1945–1988 Science Citation Index, with 187,652 citations. | 0 | Theoretical and Fundamental Chemistry |
* 2012 – Pearson Education RACI Centenary of Federation Chemistry Educator of the Year Award
* 2011 – Vice-Chancellor's Award for Outstanding Teaching
* 2011 – Australian Learning and Teaching Council Citation for Teaching Excellence
* 2010 – Vice-Chancellor's Award for Support of the Student Experience
* 2008 – NSW and ACT Young Tall Poppy Science Award
* 2007 – RACI Athel Beckwith Lectureship
* 2006 – RACI Nyholm Lectureship | 0 | Theoretical and Fundamental Chemistry |
Thiols having the structure R−SH, in which an alkyl group (R) is attached to a sulfhydryl group (SH), are referred to as alkanethiols or alkyl thiols. Thiols and alcohols have similar connectivity. Because sulfur atoms are larger than oxygen atoms, C−S bond lengths – typically around 180 picometres – are about 40 picometers longer than typical C−O bonds. The C−S−H angles approach 90° whereas the angle for the C−O−H group is more obtuse. In solids and liquids, the hydrogen-bonding between individual thiol groups is weak, the main cohesive force being Van der Waals interactions between the highly polarizable divalent sulfur centers.
The S−H bond is much weaker than the O−H bond as reflected in their respective bond dissociation energies (BDE). For CHS−H, the BDE is , while for CHO−H, the BDE is .
An S−H bond is moderately polar because of the small difference in the electronegativity of sulfur and hydrogen. In contrast, O−H bonds in hydroxyl groups are more polar. Thiols have a lower dipole moment relative to their corresponding alcohols. | 0 | Theoretical and Fundamental Chemistry |
Alexander Frank Wells (2 September 1912 – 28 November 1994), or A. F. Wells, was a British chemist and crystallographer. He is known for his work on structural inorganic chemistry, which includes the description and classification of structural motifs, such as the polyhedral coordination environments, in crystals obtained from X-ray crystallography. His work is summarized in a classic reference book, Structural inorganic chemistry, first appeared in 1945 and has since gone through five editions. In addition his work on crystal structures in terms of nets have been important and inspirational for the field of Metal-Organic Frameworks and related materials. | 0 | Theoretical and Fundamental Chemistry |
Plasma electron temperatures can range between ~6,000 K and ~10,000 K and are usually several orders of magnitude greater than the temperature of the neutral species. Argon ICP plasma discharge temperatures are typically ~5,500 to 6,500 K and are therefore comparable to that reached at the surface (photosphere) of the sun (~4,500 K to ~6,000 K). ICP discharges are of relatively high electron density, on the order of 10 cm. As a result, ICP discharges have wide applications where a high-density plasma (HDP) is needed.
* ICP-AES, a type of atomic emission spectroscopy.
* ICP-MS, a type of mass spectrometry.
* ICP-RIE, a type of reactive-ion etching.
Another benefit of ICP discharges is that they are relatively free of contamination, because the electrodes are completely outside the reaction chamber. By contrast, in a capacitively coupled plasma (CCP), the electrodes are often placed inside the reactor and are thus exposed to the plasma and subsequent reactive chemical species. | 0 | Theoretical and Fundamental Chemistry |
Many shower curtains come with features to reduce the shower-curtain effect. They may have adhesive suction cups on the bottom edges of the curtain, which are then pushed onto the sides of the shower when in use. Others may have magnets at the bottom, though these are not effective on acrylic or fiberglass tubs.
It is possible to use a telescopic shower curtain rod to block the curtain on its lower part and to prevent it from sucking inside.
Hanging the curtain rod higher or lower, or especially further away from the shower head, can reduce the effect. A convex shower rod can also be used to hold the curtain against the inside wall of a tub.
A weight can be attached to a long string and the string attached to the curtain rod in the middle of the curtain (on the inside). Hanging the weight low against the curtain just above the rim of the shower pan or tub makes it an effective billowing deterrent without allowing the weight to hit the pan or tub and damage it.
There are a few alternative solutions that either attach to the shower curtain directly, attach to the shower rod or attach to the wall. | 1 | Applied and Interdisciplinary Chemistry |
The "elution time" of a solute is the time between the start of the separation (the time at which the solute enters the column) and the time at which the solute elutes. In the same way, the elution volume is the volume of eluent required to cause elution. Under standard conditions for a known mix of solutes in a certain technique, the elution volume may be enough information to identify solutes. For instance, a mixture of amino acids may be separated by ion-exchange chromatography. Under a particular set of conditions, the amino acids will elute in the same order and at the same elution volume. | 0 | Theoretical and Fundamental Chemistry |
The core of β-catenin consists of several very characteristic repeats, each approximately 40 amino acids long. Termed armadillo repeats, all these elements fold together into a single, rigid protein domain with an elongated shape – called armadillo (ARM) domain. An average armadillo repeat is composed of three alpha helices. The first repeat of β-catenin (near the N-terminus) is slightly different from the others – as it has an elongated helix with a kink, formed by the fusion of helices 1 and 2. Due to the complex shape of individual repeats, the whole ARM domain is not a straight rod: it possesses a slight curvature, so that an outer (convex) and an inner (concave) surface is formed. This inner surface serves as a ligand-binding site for the various interaction partners of the ARM domains.
The segments N-terminal and far C-terminal to the ARM domain do not adopt any structure in solution by themselves. Yet these intrinsically disordered regions play a crucial role in β-catenin function. The N-terminal disordered region contains a conserved short linear motif responsible for binding of TrCP1 (also known as β-TrCP) E3 ubiquitin ligase – but only when it is phosphorylated. Degradation of β-catenin is thus mediated by this N-terminal segment. The C-terminal region, on the other hand, is a strong transactivator when recruited onto DNA. This segment is not fully disordered: part of the C-terminal extension forms a stable helix that packs against the ARM domain, but may also engage separate binding partners. This small structural element (HelixC) caps the C-terminal end of the ARM domain, shielding its hydrophobic residues. HelixC is not necessary for β-catenin to function in cell–cell adhesion. On the other hand, it is required for Wnt signaling: possibly to recruit various coactivators, such as 14-3-3zeta. Yet its exact partners among the general transcription complexes are still incompletely understood, and they likely involve tissue-specific players. Notably, the C-terminal segment of β-catenin can mimic the effects of the entire Wnt pathway if artificially fused to the DNA binding domain of LEF1 transcription factor.
Plakoglobin (also called γ-catenin) has a strikingly similar architecture to that of β-catenin. Not only their ARM domains resemble each other in both architecture and ligand binding capacity, but the N-terminal β-TrCP-binding motif is also conserved in plakoglobin, implying common ancestry and shared regulation with β-catenin. However, plakoglobin is a very weak transactivator when bound to DNA – this is probably caused by the divergence of their C-terminal sequences (plakoglobin appears to lack the transactivator motifs, and thus inhibits the Wnt pathway target genes instead of activating them). | 1 | Applied and Interdisciplinary Chemistry |
Air kerma is of importance in the practical calibration of instruments for photon measurement, where it is used for the traceable calibration of gamma instrument metrology facilities using a "free air" ion chamber to measure air kerma.
IAEA safety report 16 states "The quantity air kerma should be used for calibrating the reference photon radiation fields and reference instruments. Radiation protection monitoring instruments should be calibrated in terms of dose equivalent quantities. Area dosimeters or dose ratemeters should be calibrated in terms of the ambient dose equivalent, H*(10), or the directional dose equivalent, H′(0.07),without any phantom present, i.e. free in air."
Conversion coefficients from air kerma in Gy to equivalent dose in Sv are published in the International Commission on Radiological Protection (ICRP) report 74 (1996). For instance, air kerma rate is converted to tissue equivalent dose using a factor of Sv/Gy (air) = 1.21 for Cs 137 at 0.662 MeV. | 0 | Theoretical and Fundamental Chemistry |
The Institute of Chemistry PNG is the professional organisation supporting chemical sciences in Papua New Guinea and a learned society promoting the science and practice of chemistry. | 1 | Applied and Interdisciplinary Chemistry |
Synthesis of marmesin has been successfully conducted in the laboratory on multiple occasions. One way of doing so is by a strategy based on the palladium-catalyzed intramolecular coupling reaction. This reaction would construct the dihydropyran ring and synthesize the compound from the intermediate (-)-peucedanol. The key step in the overall synthesis uses catalytic asymmetric epoxidation of an enone. | 1 | Applied and Interdisciplinary Chemistry |
The plasma used in an ICP-MS is made by partially ionizing argon gas (Ar → Ar + e). The energy required for this reaction is obtained by pulsing an alternating electric current in load coil that surrounds the plasma torch with a flow of argon gas.
After the sample is injected, the plasma's extreme temperature causes the sample to separate into individual atoms (atomization). Next, the plasma ionizes these atoms (M → M + e) so that they can be detected by the mass spectrometer.
An inductively coupled plasma (ICP) for spectrometry is sustained in a torch that consists of three concentric tubes, usually made of quartz. The two major designs are the Fassel and Greenfield torches. The end of this torch is placed inside an induction coil supplied with a radio-frequency electric current. A flow of argon gas (usually 14 to 18 liters per minute) is introduced between the two outermost tubes of the torch and an electrical spark is applied for a short time to introduce free electrons into the gas stream. These electrons interact with the radio-frequency magnetic field of the induction coil and are accelerated first in one direction, then the other, as the field changes at high frequency (usually 27.12 MHz or 40 MHz). The accelerated electrons collide with argon atoms, and sometimes a collision causes an argon atom to part with one of its electrons. The released electron is in turn accelerated by the rapidly changing magnetic field. The process continues until the rate of release of new electrons in collisions is balanced by the rate of recombination of electrons with argon ions (atoms that have lost an electron). This produces a ‘fireball’ that consists mostly of argon atoms with a rather small fraction of free electrons and argon ions. | 0 | Theoretical and Fundamental Chemistry |
Subsets and Splits
No saved queries yet
Save your SQL queries to embed, download, and access them later. Queries will appear here once saved.