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The most widely used electrode is the glass electrode, which is selective for the hydrogen ion. This is suitable for all acid–base equilibria. values between about 2 and 11 can be measured directly by potentiometric titration using a glass electrode. This enormous range of stability constant values (ca. 100 to 10) is possible because of the logarithmic response of the electrode. The limitations arise because the Nernst equation breaks down at very low or very high pH.
When a glass electrode is used to obtain the measurements on which the calculated equilibrium constants depend, the precision of the calculated parameters is limited by secondary effects such as variation of liquid junction potentials in the electrode. In practice it is virtually impossible to obtain a precision for log β better than ±0.001. | 7 | Physical Chemistry |
In one study, the human health and environmental costs due to pesticides in the United States was estimated to be $9.6 billion: offset by about $40 billion in increased agricultural production.
Additional costs include the registration process and the cost of purchasing pesticides: which are typically borne by agrichemical companies and farmers respectively. The registration process can take several years to complete (there are 70 different types of field tests) and can cost $50–70 million for a single pesticide. At the beginning of the 21st century, the United States spent approximately $10 billion on pesticides annually. | 2 | Environmental Chemistry |
The Joback method uses a four-parameter polynomial to describe the temperature dependency of the ideal-gas heat capacity. These parameters are valid from 273 K to about 1000 K. But you are able to extend it to 1500K if you don't mind a bit of uncertainty here and there. | 7 | Physical Chemistry |
GPR126 is necessary for Schwann cell myelination. Knockouts of this adhesion GPCR in both Danio rerio and Mus musculus result in an arrest at the promyelinating stage. Schwann cells arise from the neural crest, which migrates to peripheral nerves to form either myelinating or non-myelinating cells. In GPR126 knockouts, these precursor cells develop to the promyelinating stage, where they have wrapped approximately 1.5 times. Myelination is arrested at the promyelinating stage and in fish no myelin basic protein can be detected. In fish this can be rescued by adding forskolin during development, which rescues myelin basic protein expression. | 1 | Biochemistry |
DAVID (the database for annotation, visualization and integrated discovery) is a free online bioinformatics resource developed by the Laboratory of Human Retrovirology and Immunoinformatics ([https://david.ncifcrf.gov/content.jsp?file=about_us.html LHRI]). All tools in the DAVID Bioinformatics Resources aim to provide functional interpretation of large lists of genes derived from genomic studies, e.g. microarray and proteomics studies. DAVID can be found at https://david.ncifcrf.gov/
The DAVID Bioinformatics Resources consists of the DAVID Knowledgebase and five integrated, web-based functional annotation tool suites: the DAVID Gene Functional Classification Tool, the DAVID Functional Annotation Tool, the DAVID Gene ID Conversion Tool, the DAVID Gene Name Viewer and the DAVID NIAID Pathogen Genome Browser. The expanded DAVID Knowledgebase now integrates almost all major and well-known public bioinformatics resources centralized by the DAVID Gene Concept, a single-linkage method to agglomerate tens of millions of diverse gene/protein identifiers and annotation terms from a variety of public bioinformatics databases. For any uploaded gene list, the DAVID Resources now provides not only the typical gene-term enrichment analysis, but also new tools and functions that allow users to condense large gene lists into gene functional groups, convert between gene/protein identifiers, visualize many-genes-to-many-terms relationships, cluster redundant and heterogeneous terms into groups, search for interesting and related genes or terms, dynamically view genes from their lists on bio-pathways and more.
DAVID 2021 update was released in December 2021. The knowledgebase has been scheduled to update quarterly. | 1 | Biochemistry |
In magnetic spectroscopy (EPR, NMR), a microwave pulse (EPR) or a radio frequency pulse (NMR) in a strong ambient magnetic field is used as the energizing event. This turns the magnetic particles at an angle to the ambient field, resulting in gyration. The gyrating spins then induce a periodic current in a detector coil. Each spin exhibits a characteristic frequency of gyration (relative to the field strength) which reveals information about the analyte.
In Fourier-transform mass spectrometry, the energizing event is the injection of the charged sample into the strong electromagnetic field of a cyclotron. These particles travel in circles, inducing a current in a fixed coil on one point in their circle. Each traveling particle exhibits a characteristic cyclotron frequency-field ratio revealing the masses in the sample. | 7 | Physical Chemistry |
Structurally, sea foam is thermodynamically unstable, though some sea foam can persist in the environment for several days at most. There are two types of sea foam categorized based on their stability: 1) Unstable or transient foams have very short lifetimes of only seconds. The bubbles formed in sea foam may burst releasing aerosols into the air, contributing to sea spray. 2) Metastable foams can have a lifetime of several hours to several days; their duration is sometimes attributed to small particles of silica, calcium, or iron which contribute to foam stability and longevity. Additionally, seawater that contains released dissolved organic material from phytoplankton and macrophytic algae that is then agitated in its environment is most likely to produce stable, longer-lasting foam when compared with seawater lacking one of those components. For example, filtered seawater when added to the fronds of the kelp, Ecklonia maxima, produced foam but it lacked the stability that unfiltered seawater provided. Additionally, kelp fronds that were maintained in flowing water therefore reducing their mucus coating, were unable to help foam form. Different types of salt are also found to have varying effects on bubble proximity within sea foam, therefore contributing to its stability. | 9 | Geochemistry |
Cobalt(II) thiocyanate is an inorganic compound with the formula Co(SCN). The anhydrous compound is a coordination polymer with a layered structure. The trihydrate, Co(SCN)(HO), is a isothiocyanate complex used in the cobalt thiocyanate test (or Scott test) for detecting cocaine. The test has been responsible for widespread false positives and false convictions. | 3 | Analytical Chemistry |
There are an enormous number of different ways in which a chain can be curled around in a relatively compact shape, like an unraveling ball of twine with much open space, and comparatively few ways it can be more or less stretched out. So, if each conformation has an equal probability or statistical weight, chains are much more likely to be ball-like than they are to be extended — a purely entropic effect. In an ensemble of chains, most of them will, therefore, be loosely balled up. This is the kind of shape any one of them will have most of the time.
Consider a linear polymer to be a freely-jointed chain with N subunits, each of length , that occupy zero volume, so that no part of the chain excludes another from any location. One can regard the segments of each such chain in an ensemble as performing a random walk (or "random flight") in three dimensions, limited only by the constraint that each segment must be joined to its neighbors. This is the ideal chain mathematical model. It is clear that the maximum, fully extended length L of the chain is . If we assume that each possible chain conformation has an equal statistical weight, it can be shown that the probability P(r) of a polymer chain in the population to have distance r between the ends will obey a characteristic distribution described by the formula
where is the mean of .
The average (root mean square) end-to-end distance for the chain, , turns out to be times the square root of N — in other words, the average distance scales with N . | 7 | Physical Chemistry |
The African crested rat (Lophiomys imhausi) has a broad, white-bordered strip of hairs covering an area of glandular skin on the flank. When the animal is threatened or excited, the mane on its back erects and this flank strip parts, exposing the glandular area. The hairs in this flank area are highly specialised; at the tips they are like ordinary hairs, but are otherwise spongy, fibrous, and absorbent. The rat is known to deliberately chew the roots and bark of the Poison-arrow tree (Acokanthera schimperi), which contains ouabain. After the rat has chewed the tree, instead of swallowing the poison it slathers the resulting masticate onto its specialised flank hairs which are adapted to absorb the poisonous mixture. It thereby creates a defense mechanism that can sicken or even kill predators which attempt to bite it. | 0 | Organic Chemistry |
Diatomic elements played an important role in the elucidation of the concepts of element, atom, and molecule in the 19th century, because some of the most common elements, such as hydrogen, oxygen, and nitrogen, occur as diatomic molecules. John Daltons original atomic hypothesis assumed that all elements were monatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed waters formula to be HO, giving the atomic weight of oxygen as eight times that of hydrogen, instead of the modern value of about 16. As a consequence, confusion existed regarding atomic weights and molecular formulas for about half a century.
As early as 1805, Gay-Lussac and von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen, and by 1811 Amedeo Avogadro had arrived at the correct interpretation of waters composition, based on what is now called Avogadros law and the assumption of diatomic elemental molecules. However, these results were mostly ignored until 1860, partly due to the belief that atoms of one element would have no chemical affinity toward atoms of the same element, and also partly due to apparent exceptions to Avogadro's law that were not explained until later in terms of dissociating molecules.
At the 1860 Karlsruhe Congress on atomic weights, Cannizzaro resurrected Avogadro's ideas and used them to produce a consistent table of atomic weights, which mostly agree with modern values. These weights were an important prerequisite for the discovery of the periodic law by Dmitri Mendeleev and Lothar Meyer. | 4 | Stereochemistry |
Charlotte Fitch Roberts (February 13, 1859 – December 5, 1917) was an American chemist best known for her work on stereochemistry. | 4 | Stereochemistry |
Clinker is a generic name given to waste from industrial processes, particularly those that involve smelting metals, welding, burning fossil fuels and use of a blacksmith's forge, which commonly causes a large buildup of clinker around the tuyere. Clinker often forms a loose, dark deposit consisting of waste materials such as coke, coal, slag, charcoal, and grit. Clinker often has a glassy look to it, usually because of the formation of molten silica compounds during processing. Clinker generally is much denser than coke, and, unlike coke, generally contains too little carbon to be of any value as fuel. It is also applied to the byproduct of combustion and heating by those who use anthracite or lignite coal-fired boilers.
Clinkers can occur naturally, for example in underground deposits of coal that has been altered by heat from nearby molten magma; volcanic clinkers are jagged pieces of lava that look similar to industrial clinker. | 8 | Metallurgy |
James S. Robbins has argued that the advent of petroleum-refined kerosene saved some species of great whales from extinction by providing an inexpensive substitute for whale oil, thus eliminating the economic imperative for open-boat whaling, but others say that fossil fuels increased whaling with most whales being killed in the 20th century. | 7 | Physical Chemistry |
Shortly after the publication of Kirkendall's paper, L.S. Darken published an analysis of diffusion in binary systems much like the one studied by Smigelskas and Kirkendall. By separating the actual diffusive flux of the materials from the movement of the interface relative to the markers, Darken found the marker velocity to be
where and are the diffusion coefficients of the two materials and is an atomic fraction.
One consequence of this equation is that the movement of an interface varies linearly with the square root of time, which is exactly the experimental relationship discovered by Smigelskas and Kirkendall.
Darken also developed a second equation that defines a combined chemical diffusion coefficient in terms of the diffusion coefficients of the two interfacing materials:
This chemical diffusion coefficient can be used to mathematically analyze Kirkendall effect diffusion via the Boltzmann-Matano method. | 8 | Metallurgy |
The field of spectroradiometry concerns itself with the measurement of absolute radiometric quantities in narrow wavelength intervals. It is useful to sample the spectrum with narrow bandwidth and wavelength increments because many sources have line structures Most often in spectroradiometry, spectral irradiance is the desired measurement. In practice, the average spectral irradiance is measured, shown mathematically as the approximation:
Where is the spectral irradiance, is the radiant flux of the source (SI unit: watt, W) within a wavelength interval (SI unit: meter, m), incident on the surface area, (SI unit: square meter, m). The SI unit for spectral irradiance is W/m. However it is often more useful to measure area in terms of centimeters and wavelength in nanometers, thus submultiples of the SI units of spectral irradiance will be used, for example μW/cm*nm
Spectral irradiance will vary from point to point on the surface in general. In practice, it is important note how radiant flux varies with direction, the size of the solid angle subtended by the source at each point on the surface, and the orientation of the surface. Given these considerations, it is often more prudent to use a more rigorous form of the equation to account for these dependencies
Note that the prefix "spectral" is to be understood as an abbreviation of the phrase "spectral concentration of" which is understood and defined by the CIE as the "quotient of the radiometric quantity taken over an infinitesimal range on either side of a given wavelength, by the range". | 7 | Physical Chemistry |
Lev T. Perelman, principal scientist at MIT, and Vadim Backman, graduate student in Harvard- MIT Health Sciences and Technology program introduced LSS in 1998. | 7 | Physical Chemistry |
The microbial loop describes a trophic pathway in the marine microbial food web where dissolved organic carbon (DOC) is returned to higher trophic levels via its incorporation into bacterial biomass, and then coupled with the classic food chain formed by phytoplankton-zooplankton-nekton. The term microbial loop was coined by Farooq Azam, Tom Fenchel et al. in 1983 to include the role played by bacteria in the carbon and nutrient cycles of the marine environment. In general, dissolved organic carbon is introduced into the ocean environment from bacterial lysis, the leakage or exudation of fixed carbon from phytoplankton (e.g., mucilaginous exopolymer from diatoms), sudden cell senescence, sloppy feeding by zooplankton, the excretion of waste products by aquatic animals, or the breakdown or dissolution of organic particles from terrestrial plants and soils. Bacteria in the microbial loop decompose this particulate detritus to utilize this energy-rich matter for growth. Since more than 95% of organic matter in marine ecosystems consists of polymeric, high molecular weight (HMW) compounds (e.g., protein, polysaccharides, lipids), only a small portion of total dissolved organic matter (DOM) is readily utilizable to most marine organisms at higher trophic levels. This means that dissolved organic carbon is not available directly to most marine organisms; marine bacteria introduce this organic carbon into the food web, resulting in additional energy becoming available to higher trophic levels. | 9 | Geochemistry |
Oftentimes, ELPs are not used in isolation, but are rather fused with other proteins to become functionally active. The structure of these other proteins will have a certain effect on transition temperature. It is important to be able to predict the transition temperature that these fusion proteins will have relative to the free ELPs, as this temperature will determine the fused protein's applicability and phase transition. A theoretical model is available that relates the change in T of the fused protein to the varying ratios of each individual amino acid found in the fused protein. The model involves calculating a surface index (SI) associated with each amino acid and then extrapolating, based on the ratio of each amino acid present in the fused protein, the total change in the T associated with the fusion protein, ΔT:
SI=(ASA/ ASA)(T)
where ASA refers to the area of the entire fused protein that is available to the solvent that is being used, ASA refers to the area of the guest residue on the ELP that is available to the solvent, and T is the transition temperature that is unique to the amino acid. Summing up the contribution of each potential guest residue (XAA) will yield an SI index that is directly proportional to ΔT It was found that the amino acids that are charged under a physiological pH of 7.4 have the greatest impact on the overall SI of a fused protein. This is due to the fact that they are more accessible to water-containing solvents, thereby increasing the ASA and also have high T values. Hence, knowledge of the transition temperature of a fused protein is highly dependent on the presence of these charged residues. | 7 | Physical Chemistry |
The eFS assay could be used to analyze other cell or tissue types. By assessing enrichment in GFP-expressing CD2-negative as well as CD2-positive cells, and by crossing a common pool of reporter transformant male flies to females expressing CD2 in different cell types, it is possible to assay specificity as well as activity. Accelerating the annotation of the regulatory genome in Drosophila should in principle generate the kind of large-scale regulatory interaction data that would allow exploring the network properties of transcriptional regulation. | 1 | Biochemistry |
Both anti-glycoprotein-210 (anti-gp210) and anti-nucleoporin 62 (anti-p62) antibodies are antibodies to components of the nuclear membrane and are found in primary biliary cirrhosis (PBC). Each antibody is present in approximately 25–30% of PBC. The antigens of both antibodies are constituents of the nuclear membrane. gp210 is a 200kDa protein involved in anchoring components of the nuclear pore to the nuclear membrane. The p62 antigen is a 60kDa nuclear pore complex. | 1 | Biochemistry |
After Moseleys death in 1915, the atomic numbers of all known elements from hydrogen to uranium (Z = 92) were examined by his method. There were seven elements (with Z < 92) which were not found and therefore identified as still undiscovered, corresponding to atomic numbers 43, 61, 72, 75, 85, 87 and 91. From 1918 to 1947, all seven of these missing elements were discovered. By this time, the first four transuranium elements had also been discovered, so that the periodic table was complete with no gaps as far as curium (Z' = 96). | 3 | Analytical Chemistry |
The expansion ratio of a liquefied and cryogenic substance is the volume of a given amount of that substance in liquid form compared to the volume of the same amount of substance in gaseous form, at room temperature and normal atmospheric pressure.
If a sufficient amount of liquid is vaporized within a closed container, it produces pressures that can rupture the pressure vessel. Hence the use of pressure relief valves and vent valves are important.
The expansion ratio of liquefied and cryogenic from the boiling point to ambient is:
*nitrogen – 1 to 696
*liquid helium – 1 to 745
*argon – 1 to 842
*liquid hydrogen – 1 to 850
*liquid oxygen – 1 to 860
*neon – Neon has the highest expansion ratio with 1 to 1445. | 7 | Physical Chemistry |
Raychelle Burks is an associate professor of analytical chemistry at American University in Washington, D.C., and science communicator, who has regularly appeared on the Science Channel. In 2020, the American Chemical Society awarded her the Grady-Stack award for her public engagement excellence. | 3 | Analytical Chemistry |
It is not possible to determine the structure of a protein with H/D exchange other than neutron crystallography nor is it possible to define secondary structural elements. The reasons for this are related to the way in which protein structure slows exchange. Exchange rates are a function of two parameters: solvent accessibility and hydrogen bonding. Thus an amide which is part of an intramolecular hydrogen bond will exchange slowly if at all, while an amide on the surface of protein hydrogen bonded to water will exchange rapidly. Amides buried from the solvent but not hydrogen bonded may also have very slow exchange rates. Because both solvent accessibility and hydrogen bonding contribute to the rate of exchange, it becomes difficult to attribute a given exchange rate to a structural element without crystallography or NMR structural data.
H–D exchange has been used to characterize the folding pathway of proteins, by refolding the protein under exchange conditions. In a forward exchange experiment (H to D), a pulse of deuterium is added after various amounts of refolding time. The parts of the structure that form rapidly will be protected and thus not exchanged, whereas areas that fold late in the pathway will be exposed to the exchange for longer periods of time. Thus H/D exchange can be used to determine the sequence of various folding events. Factors determining the time resolution of this approach are the efficiency of mixing and how quickly the quench can be performed after the labeling.
H–D exchange has been used to characterize protein structures and protein–protein interactions. The exchange reaction needs to be carried out with the isolated proteins and with the complex. The exchanging regions are then compared. If a region is buried by the binding, the amides in this region may be protected in the complex and exchange slowly. However, one must bear in mind that H–D exchange cannot be used to locate binding interfaces for all protein-protein interactions. Some protein-protein interactions are driven by electrostatic forces of side chains and are unlikely to change the exchange rate of backbone amide hydrogens, particularly if the amide hydrogens are located in stable structural elements such as alpha helices.
Lastly, H–D exchange can be used to monitor conformational changes in proteins as they relate to protein function. If conformation is altered as result of post-translational modification, enzyme activation, drug binding or other functional events, there will likely be a change to H/D exchange that can be detected. | 7 | Physical Chemistry |
In recent years, pheromone traps also partook in the digital transformation in agriculture, and agritech companies introduced digital pheromone traps. Also known as Pest Traps, digital pheromone traps are IoT devices that include systems to detect and identify pests in the field. Their main goal is to notice pests and manage pesticide spraying. They involve sticky papers, in-built cameras, and various software systems that enable pest detection and identification. Some pheromone traps such as [https://doktar.com Doktar]'s [https://www.doktar.com/en/pheromone-trap PestTrapp], utilize machine learning technologies to automatize the detection process for farmers and agricultural busines<nowiki/>ses. Smart farming practices have adapted using Digital Pest Traps as financially beneficial and environmentally friendly tools. | 1 | Biochemistry |
Tetsuo Nozoe (野副 鉄男, 16 May 1902 – 4 April 1996) was a Japanese organic chemist. He is known for the discovery of hinokitiol, a seven-membered aromatic compound, and studying non-benzenoid aromatic compounds. | 0 | Organic Chemistry |
The Graduate Institute of Ferrous Technology (GIFT POSTECH) is an institute for graduate-level education and research in the field of iron and steel technology at Pohang University of Science and Technology, South Korea. It has nine specialized laboratories covering all sides of metallurgy. However, the Institute now has a reduced focus on steels, having introduced laboratories on battery electronics,. | 8 | Metallurgy |
The great austrapede (Tsawltsping in Navi) is a bipedal, flightless, bird-like creature resembling the emu, ostrich, or the extinct Phorusrhacids that live in Pandoran savannah, and can be tamed and ridden as a mount by certain Navi clans. It has dark grey skin with blue-grey striping on its body and yellow markings on its wings, which it uses for threat displays and the long-clawed fingers at the ends for hunting and battling rivals. Great austrapedes stand slightly taller than their genetic cousin, the austrapede, and is a far more imposing creature overall. They first appear in the musical Toruk – The First Flight. | 1 | Biochemistry |
Near infrared fluorescence (NIR) detection is a method that can reveal what kinds of chemicals are present in a sample based on their physical properties. By hitting a sample with near infrared light, chemical bonds in the sample vibrate and re-release the light energy at a wavelength characteristic for a specific molecule or chemical bond. It is not yet known if the differences between GMOs and conventional plants are large enough to detect with NIR imaging. Although the technique would require advanced machinery and data processing tools, a non-chemical approach could have some advantages such as lower costs and enhanced speed and mobility. | 1 | Biochemistry |
Norvaline is used as a dietary supplement for bodybuilding.
Recently, it was suggested in the treatment of Alzheimer's disease. | 1 | Biochemistry |
The following outline is provided as an overview of and topical guide to organic chemistry:
Organic chemistry is the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of carbon-based compounds, hydrocarbons, and their derivatives. These compounds may contain any number of other elements, including hydrogen, nitrogen, oxygen, the halogens as well as phosphorus, silicon, and sulfur. | 0 | Organic Chemistry |
In binary (two component) mixtures, the binodal can be determined at a given temperature by drawing a tangent line to the free energy. | 7 | Physical Chemistry |
Henrys law has been shown to apply to a wide range of solutes in the limit of infinite dilution (x' → 0), including non-volatile substances such as sucrose. In these cases, it is necessary to state the law in terms of chemical potentials. For a solute in an ideal dilute solution, the chemical potential depends only on the concentration. For non-ideal solutions, the activity coefficients of the components must be taken into account:
where for a volatile solute; c° = 1 mol/L.
For non-ideal solutions, the infinite dilution activity coefficient γ depends on the concentration and must be determined at the concentration of interest. The activity coefficient can also be obtained for non-volatile solutes, where the vapor pressure of the pure substance is negligible, by using the Gibbs-Duhem relation:
By measuring the change in vapor pressure (and hence chemical potential) of the solvent, the chemical potential of the solute can be deduced.
The standard state for a dilute solution is also defined in terms of infinite-dilution behavior. Although the standard concentration c° is taken to be 1 mol/L by convention, the standard state is a hypothetical solution of 1 mol/L in which the solute has its limiting infinite-dilution properties. This has the effect that all non-ideal behavior is described by the activity coefficient: the activity coefficient at 1 mol/L is not necessarily unity (and is frequently quite different from unity).
All the relations above can also be expressed in terms of molalities b rather than concentrations, e.g.:
where for a volatile solute; b° = 1 mol/kg.
The standard chemical potential μ°, the activity coefficient γ and the Henrys law constant H' all have different numerical values when molalities are used in place of concentrations. | 7 | Physical Chemistry |
According to the Greek-Russian archaeologist, Sarianidi, who explored the tepes, Gonurtepe was the "capital or the imperial city of a complex Bronze Age state, one that stretched at least a thousand square miles and encompassing hundreds of satellite settlements". He also called it the "worlds fifth center of ancient civilization" with its refined society called the "Turkmenistans Morghab River society", formally called the "Bactria-Margiana Archaeological Complex". It is said to be in league with the "cultural cradles of antiquity" of Egypt, Mesopotamia, India, and China.
The meandering Morghab River along which the Morghab civilization developed by Gonurdepe and Merv, which was once an important place along the Silk Route. But the river flows through the regional capital city of Mary, about 40 miles away from the exploration site of Gonurtepe.
The site is dated to late 3rd millennium BC. Excavations have taken place for more than 35 years and still continue at a slow pace due to a lack of adequate funding. The main findings of the excavations are that the site was "an agricultural and herding community who grew grain, raised sheep, built sophisticated irrigation and sewage systems, and produced ceramics in the many kilns that dot the landscape."
A fort had been built with thick walls and the enclosed area within the fort had single storied houses, and also a palace, two observatories and cremation grounds. The excavation of the cemeteries revealed many objects, both local and imported (from Indus Valley and Egypt).
Religious practices indicated that it was the birthplace of the Zoroastrian religion, a monolithic religion. The practices of sheep sacrifices, temples dedicated to fire and water, drinking of soma-haoma (a brew presumed to be made of opium, ephedra, and a local narcotic) have been deduced as practices followed by Zoroastrians. | 8 | Metallurgy |
A recently growing way to analyze T-RFLP profiles is use multivariate statistical methods to interpret the T-RFLP data. Usually the methods applied are those commonly used in ecology and especially in the study of biodiversity. Among them ordinations and cluster analysis are the most widely used.
In order to perform multivariate statistical analysis on T-RFLP data, the data must first be converted to table known as a “sample by species table“ which depicts the different samples (T-RFLP profiles) versus the species (T-RFS) with the height or area of the peaks as values. | 1 | Biochemistry |
Petroleum is used mostly, by volume, for refining into fuel oil and gasoline, both important primary energy sources. 84% by volume of the hydrocarbons present in petroleum is converted into fuels, including gasoline, diesel, jet, heating, and other fuel oils, and liquefied petroleum gas.
Due to its high energy density, easy transportability and relative abundance, oil has become the worlds most important source of energy since the mid-1950s. Petroleum is also the raw material for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics; the 16 percent not used for energy production is converted into these other materials. Petroleum is found in porous rock formations in the upper strata of some areas of the Earths crust. There is also petroleum in oil sands (tar sands). Known oil reserves are typically estimated at 190 km (1.2 trillion (short scale) barrels) without oil sands, or 595 km (3.74 trillion barrels) with oil sands. Consumption is currently around per day, or 4.9 km per year, yielding a remaining oil supply of only about 120 years, if current demand remains static. More recent studies, however, put the number at around 50 years.
Closely related to fuels for combustion engines are Lubricants, greases, and viscosity stabilizers. All are derived from petroleum. | 7 | Physical Chemistry |
Brain cytoplasmic 200 long-noncoding RNA (or BC200 lncRNA) is a 200 nucleotide RNA transcript found predominantly in the brain with a primary function of regulating translation by inhibiting its initiation. As a long non-coding RNA, it belongs to a family of RNA transcripts that are not translated into protein (ncRNAs). Of these ncRNAs, lncRNAs are transcripts of 200 nucleotides or longer and are almost three times more prevalent than protein-coding genes. Nevertheless, only a few of the almost 60,000 lncRNAs have been characterized, and little is known about their diverse functions (transcriptional interference, chromatin remodeling, splicing, translation regulation, interaction with miRNAs and siRNAs, and mRNA degradation). BC200 is one lncRNA that has given insight into their specific role in translation regulation, and implications in various forms of cancer as well as Alzheimer's disease.
The accepted gene symbol for the BC200-coding gene is BCYRN1, for Brain cytoplasmic RNA 1. | 1 | Biochemistry |
Potassium thioacetate is an organosulfur compound and a salt with the formula . This white, water-soluble solid is used as a reagent for preparing thioacetate esters and other derivatives. | 0 | Organic Chemistry |
The recent development of electron spectroscopy makes it possible to reveal the electronic structures of molecules. Although this is mainly accomplished by electron analysers, electrostatic lenses also play a significant role in the development of electron spectroscopy.
Since electron spectroscopy detects several physical phenomena from the electrons emitted from samples, it is necessary to transport the electrons to the electron analyser. Electrostatic lenses satisfy the general properties of lenses. | 7 | Physical Chemistry |
Levosulpiride is a substituted benzamide derivative and a selective dopamine D antagonist with antipsychotic and antidepressant activity. Other benzamide derivatives include metoclopramide, tiapride, and sultopride. | 4 | Stereochemistry |
DOC is a basic nutrient, supporting growth of microorganisms and plays an important role in the global carbon cycle through the microbial loop. In some organisms (stages) that do not feed in the traditional sense, dissolved matter may be the only external food source. Moreover, DOC is an indicator of organic loadings in streams, as well as supporting terrestrial processing (e.g., within soil, forests, and wetlands) of organic matter. Dissolved organic carbon has a high proportion of biodegradable dissolved organic carbon (BDOC) in first order streams compared to higher order streams. In the absence of extensive wetlands, bogs, or swamps, baseflow concentrations of DOC in undisturbed watersheds generally range from approximately 1 to 20 mg/L carbon. Carbon concentrations considerably vary across ecosystems. For example, the Everglades may be near the top of the range and the middle of oceans may be near the bottom. Occasionally, high concentrations of organic carbon indicate anthropogenic influences, but most DOC originates naturally.
The BDOC fraction consists of organic molecules that heterotrophic bacteria can use as a source of energy and carbon. Some subset of DOC constitutes the precursors of disinfection byproducts for drinking water. BDOC can contribute to undesirable biological regrowth within water distribution systems.
The dissolved fraction of total organic carbon (TOC) is an operational classification. Many researchers use the term "dissolved" for compounds that pass through a 0.45 μm filter, but 0.22 μm filters have also been used to remove higher colloidal concentrations.
A practical definition of dissolved typically used in marine chemistry is all substances that pass through a GF/F filter, which has a nominal pore size of approximately 0.7 μm (Whatman glass microfiber filter, 0.6–0.8 μm particle retention). The recommended procedure is the HTCO technique, which calls for filtration through pre-combusted glass fiber filters, typically the GF/F classification. | 2 | Environmental Chemistry |
In the early 1930s, 90 percent of the urban population of the United States had electric power, in comparison to only 10 percent of rural homes. At the time, power companies did not feel that extending power to rural areas (rural electrification) would produce enough profit to make it worth their while. However, in the midst of the Great Depression, President Franklin D. Roosevelt realized that rural areas would continue to lag behind urban areas in both poverty and production if they were not electrically wired. On May 11, 1935, the president signed an executive order called the Rural Electrification Administration, also known as REA. The agency provided loans to fund electric infrastructure in the rural areas. In just a few years, 300,000 people in rural areas of the United States had received power in their homes.
While electricity dramatically improved working conditions on farms, it also had a large impact on the safety of food production. Refrigeration systems were introduced to the farming and food distribution processes, which helped in food preservation and kept food supplies safe. Refrigeration also allowed for shipment of perishable commodities throughout the United States. As a result, United States farmers quickly became the most productive in the world, and entire new food systems arose. | 7 | Physical Chemistry |
Pdr1p (Pleiotropic Drug Resistance 1p) is a transcription factor found in yeast and is a key regulator of genes involved in general drug response. It induces the expression of ATP-binding cassette transporter, which can export toxic substances out of the cell, allowing cells to survive under general toxic chemicals. It binds to DNA sequences that contain certain motifs called pleiotropic drug response element (PDRE). Pdr1p is encoded by a gene called PDR1 (also known as YGL013C) on chromosome VII. | 1 | Biochemistry |
Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, and this complex links the glycolysis metabolic pathway to the citric acid cycle. Pyruvate decarboxylation is also known as the "pyruvate dehydrogenase reaction" because it also involves the oxidation of pyruvate.
This multi-enzyme complex is related structurally and functionally to the oxoglutarate dehydrogenase and branched-chain oxo-acid dehydrogenase multi-enzyme complexes. | 1 | Biochemistry |
1,2 carboboration delivers the carbon-carbon bond and the carbon-boron bond to adjacent carbons in the substrate. It is typically facilitated by transition metal catalysis, but transition-metal-free 1,2 carboborations have been developed and continue to be of interest to synthetic chemists. The benefit of utilizing transition metals is that the reactions can often have enantioselective control based on the ligands used on the metal complex. Common metals used are palladium, nickel, and copper, which are often coupled with an organoborane or a boron source with an electrophile or nucleophile. | 0 | Organic Chemistry |
Future applications of this information could include:
* Constructing a more accurate and nuanced definition of the phenomenon of "death".
* Helping forensic pathologists (or biologists or veterinarians) establish a more precise time of death (for example, in an eco-health investigation, when the practitioner needs information on the time or cause of poisoning, without a case of zoonosis). With a better understanding of the steps of this phenomenon in the human thanatomicrobiome, a coroner could, via a "postmortem serology", establish with greater precision the time since death (by the hour, or even by the minute), which can be useful for investigations to reconstruct the conditions of death.
* Illuminating the phenomena of cell death, apoptosis, and in particular the phenomenon of ischemia (including myocardial ischemia) and the process of healing and resilience, perhaps even for the purpose of facilitating them. The post-mortem gene revival means that, for up to 48 hours following death, enough energy remains in the cells to activate some cellular machinery. At least some of these genes appear to be those involved in physiological healing, or "auto-resuscitation". Previous studies have shown that in people who have died by trauma, heart attack, or suffocation, various genes including those involved in cardiac muscle contraction and wound healing were active more than 12 hours after death. Similar genetic evidence has been found in dental pulp. Some authors in 2015 introduced the concept of "thanatotranscriptome apoptotic".
* Understanding cancer. It has been found that genes involved in carcinogenesis are among those reactivated soon after death, with a peak of activity about 24 hours post-mortem. A better understanding of this activity could shed light on the phenomenon of carcinogenesis and potentially lead to new tools to combat it.
* Improving the quality of organ transplants. The fact that cancer-related genes are activated following death can shed light on the timing of organ transplantation to reduce the incidence of cancer in transplant recipients. Liver transplant recipients have been shown to be more prone to cancers after treatment than would be statistically normal. This phenomenon has been attributed to their post-operative diet, or to the immunosuppressive drugs administered to prevent their body from rejecting the transplant. One hypothesis (yet to be verified) is that post-mortem cancer genes activated in the liver of the donor may also play a role.
* Testing the hypothesis that after death, a rapid decrease of "suppressor gene" activity (which normally inhibit the activation of other genes, including those no longer needed after the fetal stage) would allow dormant genes wake up, at least for a short period of time. | 1 | Biochemistry |
Monopolin is composed of a 4 CSM1:2 LRS4 complex which forms a V-shaped structure with two globular heads at the ends, which are responsible for directly crosslinking sister kinetochores. Bound to each CSM1 head is a MAM1 protein which recruits one copy of the HRR25 kinase. The hydrophobic cavity on the CSM1 subunit allows the hydrophobic regions of Monopolin receptor and kinetochore protein, DSN1, to bind to and fuse the sister kinetochores. Microtubules can then attach to the kinetochores on the homologous centromeres and pull them toward opposite mitotic spindles to complete anaphase of meiosis I. | 1 | Biochemistry |
Hypothermia usually occurs from exposure to low temperatures, and is frequently complicated by alcohol consumption. Any condition that decreases heat production, increases heat loss, or impairs thermoregulation, however, may contribute. Thus, hypothermia risk factors include: substance use disorders (including alcohol use disorder), homelessness, any condition that affects judgment (such as hypoglycemia), the extremes of age, poor clothing, chronic medical conditions (such as hypothyroidism and sepsis), and living in a cold environment. Hypothermia occurs frequently in major trauma, and is also observed in severe cases of anorexia nervosa. Hypothermia is also associated with worse outcomes in people with sepsis. While most people with sepsis develop fevers (elevated body temperature), some develop hypothermia.
In urban areas, hypothermia frequently occurs with chronic cold exposure, such as in cases of homelessness, as well as with immersion accidents involving drugs, alcohol or mental illness. While studies have shown that people experiencing homelessness are at risk of premature death from hypothermia, the true incidence of hypothermia-related deaths in this population is difficult to determine. In more rural environments, the incidence of hypothermia is higher among people with significant comorbidities and less able to move independently. With rising interest in wilderness exploration, and outdoor and water sports, the incidence of hypothermia secondary to accidental exposure may become more frequent in the general population. | 1 | Biochemistry |
Inelastic scattering is common in molecular collisions. Any collision which leads to a chemical reaction will be inelastic, but the term inelastic scattering is reserved for those collisions which do not result in reactions. There is a transfer of energy between the translational mode (kinetic energy) and rotational and vibrational modes.
If the transferred energy is small compared to the incident energy of the scattered particle, one speaks of quasielastic scattering. | 7 | Physical Chemistry |
Thermochemical changes involve decomposition of the explosives and binders, loss of strength of binder as it softens or melts, or stiffening of the binder if the increased temperature causes crosslinking of the polymer chains. The changes can also significantly alter the porosity of the material, whether by increasing it (fracturing of crystals, vaporization of components) or decreasing it (melting of components). The size distribution of the crystals can be also altered, e.g. by Ostwald ripening. Thermochemical decomposition starts to occur at the crystal nonhomogeneities, e.g. intragranular interfaces between crystal growth zones, on damaged parts of the crystals, or on interfaces of different materials (e.g. crystal/binder). Presence of defects in crystals (cracks, voids, solvent inclusions...) may increase the explosive's sensitivity to mechanical shocks. | 7 | Physical Chemistry |
The way that porosity develops during the dealloying process has been studied computationally to understand the diffusional pathways on an atomistic level. Firstly, the less noble atoms must be dissolved away from the surface of the alloy. This process is easiest for the lower coordinated atoms, i.e., those bonded to fewer other atoms, usually found as single atoms sitting on the surface ("adatoms"), but it is more difficult for higher coordinated atoms, i.e., those sitting at "steps" or in the bulk of the material. Thus, the slowest step, and that which is most important for determining rate of porosity evolution is the dissolution of these higher coordinated less noble atoms. Just as the less noble metal is less stable as an adatom on the surface, so is an atom of the more noble metal. Therefore, as dissolution proceeds, any more noble atoms will move to more stable positions, like steps, where its coordination is higher. This diffusion process is similar to spinodal decomposition. Eventually, clusters of more noble atoms form this way, and surrounding less noble atoms dissolve away, leaving behind a "bicontinuous structure" and providing a pathway for dissolution to continue deeper into the metal. | 8 | Metallurgy |
Sir John Conroy, 3rd Baronet, FRS (16 August 1845 – 15 December 1900) was an English analytical chemist.
Conroy was born in Kensington, west London, the son of Sir Edward Conroy, 2nd Baronet (1809–1869) and Lady Alicia Conroy. He was descended from the Ó Maolconaire family of Elphin, County Roscommon. The family had been the hereditary Ollamhs to the O'Connor Kings of Connacht. He was descended from Maoilin Ó Maolchonaire who was the last recognised Chief of the Sept. He was educated at Eton College and then Christ Church, Oxford, also the college of his father, where he read Natural Science, gaining a first class degree in 1868. His tutor was the chemical kinetics pioneer Augustus George Vernon Harcourt FRS.
He lived mostly with his mother at Arborfield Grange in Berkshire until 1880. His scientific interests were in analytical chemistry, especially optical measurements. He worked mainly in a laboratory at Christ Church in Oxford. He had teaching posts at Keble College (1880–90), and Balliol College and Trinity College (1886–1900). He worked at the Balliol-Trinity Laboratories with Sir Harold Hartley and others.
In 1890, he became a Fellow of Balliol College. In 1891, he was elected a Fellow of the Royal Society.
Conroy's religious leanings were High Church and he was involved with the English Church Union. From 1897, he was treasurer of the Radcliffe Infirmary in Oxford.
Conroy never married and died in Rome. His baronetcy became extinct as a result. | 3 | Analytical Chemistry |
A meta-analysis reported that vitamin D supplementation significantly reduced the risk of type 2 diabetes for non-obese people with prediabetes. Another meta-analysis reported that vitamin D supplementation significantly improved glycemic control [homeostatic model assessment-insulin resistance (HOMA-IR)], hemoglobin A1C (HbA1C), and fasting blood glucose (FBG) in individuals with type 2 diabetes. In prospective studies, high versus low level of vitamin D was respectively associated with significant decrease in risk of type 2 diabetes, combined type 2 diabetes and prediabetes, and prediabetes. A 2011 Cochrane systematic review examined one study that showed vitamin D together with insulin maintained levels of fasting C-peptide after 12 months better than insulin alone. However, it is important to highlight that the studies available to be included in this review presented considerable flaws in quality and design. | 1 | Biochemistry |
Although the International Bureau of Weights and Measures (an international standards organization known also by its French-language initials BIPM) recognizes the use of parts-per notation, it is not formally part of the International System of Units (SI). Note that although "percent" (%) is not formally part of the SI, both the BIPM and the International Organization for Standardization (ISO) take the position that "in mathematical expressions, the internationally recognized symbol % (percent) may be used with the SI to represent the number 0.01" for dimensionless quantities. According to IUPAP, "a continued source of annoyance to unit purists has been the continued use of percent, ppm, ppb, and ppt". Although SI-compliant expressions should be used as an alternative, the parts-per notation remains nevertheless widely used in technical disciplines. The main problems with the parts-per notation are set out below. | 2 | Environmental Chemistry |
The volume concentration (not to be confused with volume fraction) is defined as the volume of a constituent divided by the volume of the mixture :
Being dimensionless, it is expressed as a number, e.g., 0.18 or 18%; its unit is 1.
There seems to be no standard notation in the English literature.
The letter used here is normative in German literature (see Volumenkonzentration). | 3 | Analytical Chemistry |
The zeroth law of thermodynamics states: If two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other.
This statement implies that thermal equilibrium is an equivalence relation on the set of thermodynamic systems under consideration. Systems are said to be in equilibrium if the small, random exchanges between them (e.g. Brownian motion) do not lead to a net change in energy. This law is tacitly assumed in every measurement of temperature. Thus, if one seeks to decide whether two bodies are at the same temperature, it is not necessary to bring them into contact and measure any changes of their observable properties in time. The law provides an empirical definition of temperature, and justification for the construction of practical thermometers.
The zeroth law was not initially recognized as a separate law of thermodynamics, as its basis in thermodynamical equilibrium was implied in the other laws. The first, second, and third laws had been explicitly stated already, and found common acceptance in the physics community before the importance of the zeroth law for the definition of temperature was realized. As it was impractical to renumber the other laws, it was named the zeroth law. | 7 | Physical Chemistry |
*[http://www.crystalimpact.com/match/Default.htm Match!] (method: powder diffraction fingerprinting)
*[https://web.archive.org/web/20080616153210/http://www.nist.gov/srd/nist3.htm NIST Crystal Data] (method: lattice matching)
*[http://www.icdd.com/ Powder Diffraction File (PDF)] (method: powder diffraction fingerprinting) | 7 | Physical Chemistry |
The success of this method is critically dependent upon the manner in which the sample is manipulated. At all stages, steps must be taken to ensure that oxygen is neither introduced to nor lost from the sample. Furthermore, the water sample must be free of any solutes that will oxidize or reduce iodine.
Instrumental methods for measurement of dissolved oxygen have widely supplanted the routine use of the Winkler test, although the test is still used to check instrument calibration. | 3 | Analytical Chemistry |
An ion channel can be characterized by its opening characteristics, ion selectivity, and control of flux (gating). Many synthetic ion channels show unique properties in one or more of these aspects. | 6 | Supramolecular Chemistry |
A colloidal gel consists of a percolated network of particles in a fluid medium, providing mechanical properties in particular the rise of elastic behaviour. The particles can show attractive interactions through osmotic depletion or through polymeric links.
Colloidal gels have three phases in their lifespan: gelation, aging and collapse. The gel is initially formed by the assembly of particles into a space-spanning network, leading to a phase arrest. In the aging phase, the particles slowly rearrange to form thicker strands, increasing the elasticity of the material. Gels can also be collapsed and separated by external fields such as gravity. Colloidal gels show linear response rheology at low amplitudes. These materials have been explored as candidates for a drug release matrix. | 7 | Physical Chemistry |
Cataracts are the primary cause of blindness in humans and mutations in one particular protein, γD-crystallin, have been linked to a number of congenital forms of this disease. An amino acid mutation, proline (P) to threonine (T) at position 23 of the polypeptide chain has been linked to at least four different forms of this ailment. SRCD investigations were conducted on the wild-type protein and two variants, the P23T mutant found in the disease, and a related modification, P23S (proline to serine, a chemically similar amino acid to threonine), to establish the nature of the cause of cataract formation. Two possible reasons were suggested as the causative factor; the reduced solubility of the mutant protein, or an instability in the structure of the protein being introduced by the mutation. Significantly, because the mutant had limited solubility, lab-based CD machines were only able to provide very noisy spectra and the data were uninterpretable as a result. However, the SRCD spectra produced had very low noise associated with their data, including the mutant, and showed clearly that the structures of the wild-type, the mutant, and the related protein all had very similar conformations. These data also established that the mutant retained stability to thermal denaturation, very similar to that of the wild-type protein. The data confirmed that the causative factor for the cataracts was the reduction in solubility associated with the P23T mutation and not changes in the stability of the protein.
Because of a high degree of flexibility, it had proven difficult to determine the structure of the extramembranous C-terminal domain of bacterial voltage-gated sodium channels. Using a series of synthesised channels where this C-terminal domain had been truncated, in some cases by a single amino acid difference between the constructs, the Wallace lab used SRCD to successfully identify the structure of this region. | 7 | Physical Chemistry |
Lead isotope analysis is a technique for determining the source of ore in ancient smelting. Lead isotope composition is a signature of ore deposits and varies very little throughout the whole deposit. Also, lead isotope composition is unchanged in the smelting process.
The amount of each of the four stable isotopes of lead are used in the analysis. They are Pb, Pb, Pb and Pb. Ratios: Pb/Pb, Pb/Pb and Pb/Pb are measured by mass spectrometry. Apart from Pb, the lead isotopes are all products of the radioactive decay of uranium and thorium. When ore is deposited, uranium and thorium are separated from the ore. Thus, deposits formed in different geological periods will have different lead isotope signatures.
:::::::U →Pb
:::::::U →Pb
:::::::Th→Pb
For example, Hauptmann performed lead isotope analysis on slags from Faynan, Jordan. The resulting signature was the same as that from ores from the dolomite, limestone and shale deposits in the Wadi Khalid and Wadi Dana areas of Jordan. | 8 | Metallurgy |
Despite being generally inert, carbon tetrachloride can undergo various reactions. Hydrogen or an acid in the presence of an iron catalyst can reduce carbon tetrachloride to chloroform, dichloromethane, chloromethane and even methane. When its vapours are passed through a red-hot tube, carbon tetrachloride dechlorinates to tetrachloroethylene and hexachloroethane.
Carbon tetrachloride, when treated with HF, gives various compounds such as trichlorofluoromethane (R-11), dichlorodifluoromethane (R-12), chlorotrifluoromethane (R-13) and carbon tetrafluoride with HCl as the by-product:
This was once one of the main uses of carbon tetrachloride, as R-11 and R-12 were widely used as refrigerants.
An alcohol solution of potassium hydroxide decomposes it to potassium chloride and potassium carbonate in water:
When a mixture of carbon tetrachloride and carbon dioxide is heated to 350 degrees C, it gives phosgene: A similar reaction with carbon monoxide instead gives phosgene and tetrachloroethylene:
Reaction with hydrogen sulfide gives thiophosgene:
Reaction with sulfur trioxide gives phosgene and pyrosulfuryl chloride:
Reaction with phosphoric anhydride gives phosgene and phosphoryl chloride:
Carbon tetrachloride reacts with dry zinc oxide at 200 degrees Celsius to yield zinc chloride, phosgene and carbon dioxide: | 2 | Environmental Chemistry |
*Koss K, Maxton D, Jankowski JAZ. The potential use of fecal dimeric M2 pyruvate kinase (Tumor M2-PK) in screening for colorectal cancer (CRC). Abstract from Digestive Disease Week, May 2005; Chicago, USA.
*Mc Loughlin R, Shiel E, Sebastian S, Ryan B, O´Connor HJ, O´Morain C. Tumor M2-PK, a novel screening tool for colorectal cancer. Abstract from Digestive Disease Week, May 2005, Chicago/USA | 1 | Biochemistry |
In chemistry, acetylation is an organic esterification reaction with acetic acid. It introduces an acetyl group into a chemical compound. Such compounds are termed acetate esters or simply acetates. Deacetylation is the opposite reaction, the removal of an acetyl group from a chemical compound. | 0 | Organic Chemistry |
Content of anthocyanins in the leaves of colorful plant foods such as purple corn, blueberries, or lingonberries, is about ten times higher than in the edible kernels or fruit.
The color spectrum of grape berry leaves may be analysed to evaluate the amount of anthocyanins. Fruit maturity, quality, and harvest time may be evaluated on the basis of the spectrum analysis. | 3 | Analytical Chemistry |
In organic chemistry, the Malaprade reaction or Malaprade oxidation is a glycol cleavage reaction in which a vicinal diol is oxidized by periodic acid or a periodate salt to give the corresponding carbonyl functional groups. The reaction was first reported by Léon Malaprade in 1928. Amino alcohols are also cleaved.
In terms of mechanism, the reaction is thought to proceed by a cyclic diester of iodine(VII). | 0 | Organic Chemistry |
Transition metal clusters use the d orbitals for bonding. Thus, they have up to nine bonding orbitals, instead of only the four present in boron and main group clusters. PSEPT also applies to metallaboranes | 7 | Physical Chemistry |
The water gas shift reaction (CO + HO → CO + H) occurs in volcanic fluids with diverse catalysts or without catalysts. The combination of ferrous sulfide (FeS, troilite) and hydrogen sulfide () as reducing agents (both reagents are simultaneously oxidized in the reaction here under creating the disulfide bond, S–S) in conjunction with pyrite () formation:
: FeS + HS → FeS + 2 H + 2 e
: or with H directly produced instead of 2 H + 2 e
: FeS + HS → FeS + H
has been demonstrated under mild volcanic conditions. This key result has been disputed. Nitrogen fixation has been demonstrated for the isotope N in conjunction with pyrite formation. Ammonia forms from nitrate with FeS/HS as reductant. Methylmercaptan [CH-SH] and carbon oxysulfide [COS] form from CO and FeS/HS, or from CO and H in the presence of NiS. | 1 | Biochemistry |
* 2003 - Rfam: an RNA family database.
* 2005 - Rfam: annotating non-coding RNAs in complete genomes.
* 2008 - The RNA WikiProject: community annotation of RNA families.
* 2008 - Rfam: updates to the RNA families database.
* 2011 - Rfam: Wikipedia, clans and the “decimal” release.
* 2012 - Rfam 11.0: 10 years of RNA families.
* 2014 - Rfam 12.0: updates to the RNA families database.
* 2017 - Rfam 13.0: shifting to a genome-centric resource for non-coding RNA families.
* 2020 - Rfam 14: expanded coverage of metagenomic, viral and microRNA families. | 1 | Biochemistry |
Source:
A large range of functional groups have already been made into FSL Kode constructs. These include:
* Carbohydrates – ranging from monosaccharides to polysaccharides and including blood group antigens, hyaluronic acid oligomers and sialic acid residues
* Peptide/protein – ranging from single amino acids to proteins as large as antibodies
* Labels – including fluorophores, radioisotopes, biotin, etc.
* Other – chemical moieties such as maleimide, click residues, PEG, charged compounds
Note 1: Multimeric – the presentation of the F residue can be as multimers with controlled spacing and be variable.
Note 2: Mass – the mass that can be anchored by an FSL Kode constructs can range from 200 to >1x10 Da | 1 | Biochemistry |
Methods of MAE detection are based on the difference between alleles, which can be distinguished either by the sequence of expressed mRNA or protein structure. Methods of MAE detection can be divided into single gene or whole genome MAE analysis. Whole genome MAE analysis cannot be performed based on protein structure yet, so these are completely NGS based techniques.
Single-gene analysis
Genome-wide analysis | 1 | Biochemistry |
Primer walking is a method to determine the sequence of DNA up to the 1.3–7.0 kb range whereas chromosome walking is used to produce the clones of already known sequences of the gene. Too long fragments cannot be sequenced in a single sequence read using the chain termination method. This method works by dividing the long sequence into several consecutive short ones. The DNA of interest may be a plasmid insert, a PCR product or a fragment representing a gap when sequencing a genome. The term "primer walking" is used where the main aim is to sequence the genome. The term "chromosome walking" is used instead when the sequence is known but there is no clone of a gene. For example, the gene for a disease may be located near a specific marker such as an RFLP on the sequence. Chromosome walking is a technique used to clone a gene (e.g., disease gene) from its known closest markers (e.g., known gene) and hence is used in moderate modifications in cloning and sequencing projects in plants, fungi, and animals. To put it another way, it's utilized to find, isolate, and clone a specific sequence existing near the gene to be mapped. Libraries of large fragments, mainly bacterial artificial chromosome libraries, are mostly used in genomic projects. To identify the desired colony and to select a particular clone the library is screened first with a desired probe. After screening, the clone is overlapped with the probe and overlapping fragments are mapped. These fragments are then used as a new probe (short DNA fragments obtained from the 3′ or 5′ ends of clones) to identify other clones. A library approximately consists of 96 clones and each clone contains a different insert. Probe one identifies λ1 and λ2 as it overlaps them . Probe two derived from λ2 clones is used to identify λ3, and so on. Orientation of the clones is determined by restriction mapping of the clones. Thus, new chromosomal regions present in the vicinity of a gene could be identified. Chromosome walking is time-consuming, and chromosome landing is the method of choice for gene identification. This method necessitates the discovery of a marker that is firmly related to the mutant locus.
The fragment is first sequenced as if it were a shorter fragment. Sequencing is performed from each end using either universal primers or specifically designed ones. This should identify the first 1000 or so bases. In order to completely sequence the region of interest, design and synthesis of new primers (complementary to the final 20 bases of the known sequence) is necessary to obtain contiguous sequence information. | 1 | Biochemistry |
Sulfur oxidation involves the oxidation of reduced sulfur compounds (such as sulfide ), inorganic sulfur (S), and thiosulfate () to form sulfuric acid (). A classic example of a sulfur-oxidizing bacterium is Beggiatoa, a microbe originally described by Sergei Winogradsky, one of the founders of environmental microbiology. Another example is Paracoccus. Generally, the oxidation of sulfide occurs in stages, with inorganic sulfur being stored either inside or outside of the cell until needed. This two step process occurs because energetically sulfide is a better electron donor than inorganic sulfur or thiosulfate, allowing for a greater number of protons to be translocated across the membrane. Sulfur-oxidizing organisms generate reducing power for carbon dioxide fixation via the Calvin cycle using reverse electron flow, an energy-requiring process that pushes the electrons against their thermodynamic gradient to produce NADH. Biochemically, reduced sulfur compounds are converted to sulfite () and subsequently converted to sulfate () by the enzyme sulfite oxidase. Some organisms, however, accomplish the same oxidation using a reversal of the APS reductase system used by sulfate-reducing bacteria (see above). In all cases the energy liberated is transferred to the electron transport chain for ATP and NADH production. In addition to aerobic sulfur oxidation, some organisms (e.g. Thiobacillus denitrificans) use nitrate () as a terminal electron acceptor and therefore grow anaerobically. | 1 | Biochemistry |
Calmodulin's ability to recognize a tremendous range of target proteins is due in large part to its structural flexibility. In addition to the flexibility of the central linker domain, the N- and C-domains undergo open-closed conformational cycling in the Ca-bound state. Calmodulin also exhibits great structural variability, and undergoes considerable conformational fluctuations, when bound to targets. Moreover, the predominantly hydrophobic nature of binding between calmodulin and most of its targets allows for recognition of a broad range of target protein sequences. Together, these features allow calmodulin to recognize some 300 target proteins exhibiting a variety of CaM-binding sequence motifs. | 1 | Biochemistry |
The Austrian pharmaceutical company, Biochemie, was founded in Kundl in July 1946 at the site of a derelict brewery, at the suggestion of a French officer, Michel Rambaud (a chemist), who was able to obtain a small amount of Penicillium start culture from France. Contamination of the fermentation tanks was a persistent problem and in 1951, the company biologist, Ernst Brandl, attempted to solve this by adding phenoxyethanol to the tanks as an anti-bacterial disinfectant. This resulted unexpectedly in an increase in penicillin production: but, the penicillin produced was not benzylpenicillin, but phenoxymethylpenicillin. Phenoxyethanol was fermented to phenoxyacetic acid in the tanks, which was then incorporated into penicillin via biosynthesis. Importantly, Brandl realised that phenoxymethylpenicillin is not destroyed by stomach acid and can therefore be given by mouth. Phenoxymethyl penicillin was originally discovered by Eli Lilly in 1948 as part of their efforts to study penicillin precursors, but was not further exploited, and there is no evidence that Lilly understood the significance of their discovery at the time.
Biochemie is part of Sandoz. | 4 | Stereochemistry |
RNA polymerases in all three domains of life have some version of factor-independent termination. All of them use poly-uracil tracts, though the exact mechanisms and accessory sequences vary. In archaea and eukaryotes, there appears to be no requirement of a hairpin. | 1 | Biochemistry |
A compositional domain in genetics is a region of DNA with a distinct guanine (G) and cytosine (C) G-C and C-G content (collectively GC content). The homogeneity of compositional domains is compared to that of the chromosome on which they reside. As such, compositional domains can be homogeneous or nonhomogeneous domains. Compositionally homogeneous domains that are sufficiently long (= 300 kb) are termed isochores or isochoric domains.
The compositional domain model was proposed as an alternative to the isochoric model. The isochore model was proposed by Bernardi and colleagues to explain the observed non-uniformity of genomic fragments in the genome. However, recent sequencing of complete genomic data refuted the isochoric model. Its main predictions were:
* GC content of the third codon position (GC3) of protein coding genes is correlated with the GC content of the isochores embedding the corresponding genes. This prediction was found to be incorrect. GC3 could not predict the GC content of nearby sequences.
* The genome organization of warm-blooded vertebrates is a mosaic of isochores. This prediction was rejected by many studies that used the complete human genome data.
* The genome organization of cold-blooded vertebrates is characterized by low GC content levels and lower compositional heterogeneity. This prediction was disproved by finding high and low GC content domains in fish genomes.
The compositional domain model describes the genome as a mosaic of short and long homogeneous and nonhomogeneous domains. The composition and organization of the domains were shaped by different evolutionary processes that either fused or broke down the domains. This genomic organization model was confirmed in many new genomic studies of cow, honeybee, sea urchin, body louse, Nasonia, beetle, and ant genomes. The human genome was described as consisting of a mixture of compositionally nonhomogeneous domains with numerous short compositionally homogeneous domains and relatively few long ones. | 1 | Biochemistry |
Ultraviolet–visible spectroscopy (UV–vis) can distinguish between enantiomers by showing a distinct Cotton effect for each isomer. UV–vis spectroscopy sees only chromophores, so other molecules must be prepared for analysis by chemical addition of a chromophore such as anthracene. Two methods are reported: the octant rule and the exciton chirality method.
The octant rule was introduced in 1961 by William Moffitt, R. B. Woodward, A. Moscowitz, William Klyne and Carl Djerassi. This empirical rule allows the prediction of the sign of the Cotton effect by analysing relative orientation of substituents in three dimensions and in this way the absolute configuration of an enantiomer. | 7 | Physical Chemistry |
The passive hyperspectral imaging spectroscopy remote sensor observes a target in multi-spectral bands. The HSI camera separates the image spectra into 52 "bins" from 500 nanometers (nm) wavelength at the blue end of the visible spectrum to 1100 nm in the infrared, giving the camera a spectral resolution of 11.5 nm. Although ARCHER records data in all 52 bands, the computational algorithms only use the first 40 bands, from 500 nm to 960 nm because the bands above 960 nm are too noisy to be useful. For comparison, the normal human eye will respond to wavelengths from approximately 400 to 700 nm, and is trichromatic, meaning the eye's cone cells only sense light in three spectral bands.
As the ARCHER aircraft flies over a search area, reflected sunlight is collected by the HSI camera lens. The collected light passes through a set of lenses that focus the light to form an image of the ground. The imaging system uses a pushbroom approach to image acquisition. With the pushbroom approach, the focusing slit reduces the image height to the equivalent of one vertical pixel, creating a horizontal line image.
The horizontal line image is then projected onto a diffraction grating, which is a very finely etched reflecting surface that disperses light into its spectra. The diffraction grating is specially constructed and positioned to create a two-dimensional (2D) spectrum image from the horizontal line image. The spectra are projected vertically, i.e., perpendicular to the line image, by the design and arrangement of the diffraction grating.
The 2D spectrum image projects onto a charge-coupled device (CCD) two-dimensional image sensor, which is aligned so that the horizontal pixels are parallel to the image's horizontal. As a result, the vertical pixels are coincident to the spectra produced from the diffraction grating. Each column of pixels receives the spectrum of one horizontal pixel from the original image. The arrangement of vertical pixel sensors in the CCD divides the spectrum into distinct and non-overlapping intervals. The CCD output consists of electrical signals for 52 spectral bands for each of 504 horizontal image pixels.
The on-board computer records the CCD output signal at a frame rate of sixty times each second. At an aircraft altitude of 2,500 ft AGL and a speed of 100 knots, a 60 Hz frame rate equates to a ground image resolution of approximately one square meter per pixel. Thus, every frame captured from the CCD contains the spectral data for a ground swath that is approximately one meter long and 500 meters wide. | 7 | Physical Chemistry |
"The Talking Stone" is a science fiction mystery short story by American writer Isaac Asimov, which first appeared in the October 1955 issue of The Magazine of Fantasy and Science Fiction and was reprinted in the 1968 collection Asimovs Mysteries. "The Talking Stone" was the second of Asimovs Wendell Urth stories. | 1 | Biochemistry |
Waxes prepared with BTA are available commercially, the idea being that the BTA will prevent any reaction by chelating the surface copper and the wax acting as a physical barrier reducing exposure to water, oxygen, and chlorides; but coating an infected object with wax will not stop the problem. Storing the object in a completely dry or oxygen free environment will also prevent bronze disease as will isolation from contact with chlorides. | 8 | Metallurgy |
In enzymology, a NAD glycohydrolase () is an enzyme that catalyzes the chemical reaction
:NAD + HO ADP-ribose + nicotinamide
Thus, the two substrates of this enzyme are NAD and HO, whereas its two products are ADP-ribose and nicotinamide. Unlike ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase (EC 3.2.2.6), which catalyzes the same reaction, this reaction does not proceed through a cyclic ADP-ribose.
This enzyme belongs to the family of hydrolases, specifically those glycosylases that hydrolyse N-glycosyl compounds. The systematic name of this enzyme class is NAD glycohydrolase. Other names in common use include NAD+ nucleosidase, NADase, DPNase, DPN hydrolase, NAD hydrolase, diphosphopyridine nucleosidase, nicotinamide adenine dinucleotide nucleosidase, NAD glycohydrolase, NAD nucleosidase, and nicotinamide adenine dinucleotide glycohydrolase. This enzyme participates in nicotinate and nicotinamide metabolism and calcium signaling pathway. Calcium metabolism involves the regulation of the levels of calcium in the body. The role this calcium plays also includes providing enough calcium for bone mineralization. It serves as the basis for the structure and rigidity of bones. Calcium metabolism can lead to a variety of diseases which can involve renal function. High concentrations of calcium can lead to cell death or apoptosis. | 1 | Biochemistry |
Data analysis methods for chemical imaging data sets typically employ mathematical algorithms common to single point spectroscopy or to image analysis. The reasoning is that the spectrum acquired by each detector is equivalent to a single point spectrum; therefore pre-processing, chemometrics and pattern recognition techniques are utilized with the similar goal to separate chemical and physical effects and perform a qualitative or quantitative characterization of individual sample components. In the spatial dimension, each chemical image is equivalent to a digital image and standard image analysis and robust statistical analysis can be used for feature extraction. | 7 | Physical Chemistry |
Metals can be heat-treated to alter the properties of strength, ductility, toughness, hardness and resistance to corrosion. Common heat treatment processes include annealing, precipitation strengthening, quenching, and tempering:
* Annealing process softens the metal by heating it and then allowing it to cool very slowly, which gets rid of stresses in the metal and makes the grain structure large and soft-edged so that, when the metal is hit or stressed it dents or perhaps bends, rather than breaking; it is also easier to sand, grind, or cut annealed metal.
* Quenching is the process of cooling metal very quickly after heating, thus "freezing" the metal's molecules in the very hard martensite form, which makes the metal harder.
* Tempering relieves stresses in the metal that were caused by the hardening process; tempering makes the metal less hard while making it better able to sustain impacts without breaking.
Often, mechanical and thermal treatments are combined in what are known as thermo-mechanical treatments for better properties and more efficient processing of materials. These processes are common to high-alloy special steels, superalloys and titanium alloys. | 8 | Metallurgy |
CFC-113 can be prepared from hexachloroethane and hydrofluoric acid:
This reaction may require catalysts such as antimony, chromium, iron and alumina at high temperatures.
Another synthesis method uses HF on tetrachloroethylene instead. | 2 | Environmental Chemistry |
One of the best-known ironmasters of the early part of the industrial revolution was John Wilkinson (1728–1808), who was considered to have "iron madness", extending even to making cast iron coffins. Wilkinsons patented method for boring iron cylinders was first used to create cannons, but later provided the precision needed to create James Watts first steam engines. | 8 | Metallurgy |
The reaction of iron powder with o-nitrocinnamic acid reduces the nitro group to a nitroso. The nitrogen then condenses with a carbon on the alkene chain with loss of a molecule of water to form a ring. Decarboxylation gives indole. | 0 | Organic Chemistry |
The density of water is about 1000 kg/m or 1 g/cm, because the size of the gram was originally based on the mass of a cubic centimetre of water.
In chemistry, g/cm is more commonly used. | 3 | Analytical Chemistry |
As outlined above, an efficient pV cell requires a material with an optical phonon mode more energetic than the bandgap, which in turn is much more energetic than the thermal energy at the intended operating temperature . Furthermore, the pV cell requires a material wherein a hot optical phonon prefers to produce an electron rather than multiple low energy acoustic phonons ().
Very few materials offer this combination of properties. Indeed, the vast majority of crystals have optical phonon energies limited to below 50 meV, and those with more energetic optical phonons tend to have much more energetic band gaps. In general, a material with a first-row element (periodic table) is required to have a highly energetic optical phonon. However, the high electronegativity of a first-row elements tends to create a very large band gap, as in diamond and the boron nitride allotropes. Graphene is one of the few materials which diverges from this trend, with no bandgap and an exceptionally energetic optical phonon mode near 200 meV. Thus, graphene has been the initial target for development of a phonovoltaic material through the opening and tuning of its bandgap.
Opening and tuning the bandgap of graphene has received substantial attention, and numerous strategies have been suggested and investigated. These include the use of uniaxial strain, electric fields, and chemical doping and functionalization. In general, these mechanisms work by either changing the symmetry of graphene (both Carbon atoms in the unit cell are identical) or hybridization ().
In the first phonovoltaic material investigations, it has been suggested that the latter technique destroys the electron-phonon coupling while the former preserves it. In particular, these investigations predict that hydrogenating graphene, to produce graphane, reduces the electron-phonon coupling so substantially that the material figure of merit vanishes; and that doping graphene with boron nitride maintains the strong electron-phonon coupling in graphene, such that its figure of merit is predicted to reach 0.65 and enable heat harvesting with twice the efficiency of a typical thermoelectric generator. | 7 | Physical Chemistry |
In chemistry, stereoselectivity is the property of a chemical reaction in which a single reactant forms an unequal mixture of stereoisomers during a non-stereospecific creation of a new stereocenter or during a non-stereospecific transformation of a pre-existing one. The selectivity arises from differences in steric and electronic effects in the mechanistic pathways leading to the different products. Stereoselectivity can vary in degree but it can never be total since the activation energy difference between the two pathways is finite: both products are at least possible and merely differ in amount. However, in favorable cases, the minor stereoisomer may not be detectable by the analytic methods used.
An enantioselective reaction is one in which one enantiomer is formed in preference to the other, in a reaction that creates an optically active product from an achiral starting material, using either a chiral catalyst, an enzyme or a chiral reagent. The degree of selectivity is measured by the enantiomeric excess. An important variant is kinetic resolution, in which a pre-existing chiral center undergoes reaction with a chiral catalyst, an enzyme or a chiral reagent such that one enantiomer reacts faster than the other and leaves behind the less reactive enantiomer, or in which a pre-existing chiral center influences the reactivity of a reaction center elsewhere in the same molecule.
A diastereoselective reaction is one in which one diastereomer is formed in preference to another (or in which a subset of all possible diastereomers dominates the product mixture), establishing a preferred relative stereochemistry. In this case, either two or more chiral centers are formed at once such that one relative stereochemistry is favored, or a pre-existing chiral center (which needs not be optically pure) biases the stereochemical outcome during the creation of another. The degree of relative selectivity is measured by the diastereomeric excess.
Stereoconvergence can be considered an opposite of stereospecificity, when the reaction of two different stereoisomers yield a single product stereoisomer.
The quality of stereoselectivity is concerned solely with the products, and their stereochemistry. Of a number of possible stereoisomeric products, the reaction selects one or two to be formed.
Stereomutation is a general term for the conversion of one stereoisomer into another. For example, racemization (as in S1 reactions), epimerization (as in interconversion of D-glucose and D-mannose in Lobry de Bruyn–Van Ekenstein transformation), or asymmetric transformation (conversion of a racemate into a pure enantiomer or into a mixture in which one enantiomer is present in excess, or of a diastereoisomeric mixture into a single diastereoisomer or into a mixture in which one diastereoisomer predominates). | 4 | Stereochemistry |
Clay soils lack large pores, restricting both water and air movement. During irrigation or rain events, the limited large pore space in fine-textured soils quickly fills with water, reducing soil oxygen levels. In addition to routine application of organic matter, microorganisms and earthworms perform a crucial assist to soil tilth. As microorganisms decompose the organic matter, soil particles bind together into larger aggregates, increasing large pore space. Clay soils are more subject to soil compaction, which reduces large pore spaces. | 9 | Geochemistry |
The IUBMB publishes standards on biochemical nomenclature, including Enzyme Commission number nomenclature, in some cases jointly with the International Union of Pure and Applied Chemistry (IUPAC). The enzyme nomenclature scheme was developed in 1955 at the International Congress of Biochemistry and, with the addition of translocases in 2018, contains 7 classes of enzymes. | 1 | Biochemistry |
Plasma processing provides interfacial energies and injected monomer fragments larger than comparable processes. However, limited fluxes prevent high process rates. In addition, plasmas are thermodynamically unfavorable and therefore plasma-processed surfaces lack uniformity, consistency, and permanence. These obstacles with plasma processing preclude it from being a competitive surface modification method within industry.
The process begins with production of plasma via ionization either by deposition on monomer mixtures or gaseous carrier ions. The power required to produce the necessary plasma flux can be derived from the active volume mass/energy balance:
where
is the active volume
is the ionization rate
is the neutral density
is the electron density
is the ion loss by diffusion, convection, attachment, and recombination
Dissipation is generally initiated via direct current (DC), radio frequency (RF), or microwave power. Gas ionization efficiency can decrease the power efficiency more than tenfold depending on the carrier plasma and substrate. | 7 | Physical Chemistry |
Retroposons are repetitive DNA fragments which are inserted into chromosomes after they had been reverse transcribed from any RNA molecule. | 1 | Biochemistry |
Mercury was surveyed by the MESSENGER mission with its Gamma-Ray Spectrometer. The K/U ratios for Mercury could range between 8,000 and 17,000 which would imply a volatile rich planet. However, metal/silicate partitioning data for K and U still needs additional experiments at the conditions of Mercury's core formation to understand this unusual high ratio. | 9 | Geochemistry |
Söllner married Herta (Helen) Rosenberg on July 23, 1934. Their daughter Barbara Sollner-Webb embarked on a scientific career. | 7 | Physical Chemistry |
The classic view of pRb's role as a tumor suppressor and cell cycle regulator developed through research investigating mechanisms of interactions with E2F family member proteins. Yet, more data generated from biochemical experiments and clinical trials reveal other functions of pRb within the cell unrelated (or indirectly related) to tumor suppression. | 1 | Biochemistry |
The process of equilibration can be described using the H-theorem or the relaxation theorem, see also entropy production. | 7 | Physical Chemistry |
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