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In some situations in which a traditional treatment plant cannot fulfill required treatment (due to higher loading rates, stringent treatment requirements, etc.), the owner might opt to convert their traditional system into a multi-SBR plant. Conversion to SBR will create a longer sludge age, minimizing sludge handling requirements downstream of the SBR.
The reverse can also be done, in which SBR Systems would be converted into extended aeration (EA) systems. SBR treatment systems that cannot cope up with a sudden constant increase of influent may easily be converted into EA plants. Extended aeration plants are more flexible in flow rate, eliminating restrictions presented by pumps located throughout the SBR systems. Clarifiers can be retrofitted in the equalization tanks of the SBR. | 1 | Applied and Interdisciplinary Chemistry |
Protein–protein interaction screening refers to the identification of Protein–protein interaction with high-throughput screening methods such as computer- and/or robot-assisted plate reading, flow cytometry analyzing.
The interactions between proteins are central to virtually every process in a living cell. Information about these interactions improves understanding of diseases and can provide the basis for new therapeutic approaches. | 1 | Applied and Interdisciplinary Chemistry |
Because the timescale for the development of reconstructions is so recent, most reconstructions have been built manually. However, now, there are quite a few resources that allow for the semi-automatic assembly of these reconstructions that are utilized due to the time and effort necessary for a reconstruction. An initial fast reconstruction can be developed automatically using resources like PathoLogic or ERGO in combination with encyclopedias like MetaCyc, and then manually updated by using resources like PathwayTools. These semi-automatic methods allow for a fast draft to be created while allowing the fine tune adjustments required once new experimental data is found. It is only in this manner that the field of metabolic reconstructions will keep up with the ever-increasing numbers of annotated genomes. | 1 | Applied and Interdisciplinary Chemistry |
The Trust for Public Land is working in partnership with the City of Los Angeles Community Redevelopment Agency, Bureau of Sanitation, the University of Southern Californias Center for Sustainable Cities, and Jefferson High School by converting the existing 900 miles of alleys in the city to green alleys. The concept is to re-engineer existing alleyways to reflect more light to mitigate heat island effect, capture storm water, and make the space beautiful and usable by the neighboring communities. The first alley, completed in 2015, saved more than 750,000 gallons in its first year. The Green alleys will provide open space on top of these ecological benefits, converting spaces which used to feel unsafe, or used for dumping into a playground, and walking/biking corridor. | 1 | Applied and Interdisciplinary Chemistry |
The term carbon sequestration is used in different ways in the literature and media. The IPCC Sixth Assessment Report defines it as "The process of storing carbon in a carbon pool". Subsequently, a pool is defined as "a reservoir in the Earth system where elements, such as carbon and nitrogen, reside in various chemical forms for a period of time".
The United States Geological Survey (USGS) defines carbon sequestration as follows: "Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide." Therefore, the difference between carbon sequestration and carbon capture and storage (CCS) is sometimes blurred in the media. The IPCC however defines CCS as "a process in which a relatively pure stream of carbon dioxide (CO) from industrial sources is separated, treated and transported to a long-term storage location".
Hence CCS is a technology application that utilizes artificial carbon sequestration techniques. | 0 | Theoretical and Fundamental Chemistry |
To control pollutants found in surface runoff, permeable paving surfaces capture the stormwater in the soil or aggregate base below the road or pathway, and subsequently treat the runoff via percolation, which allows water to infiltrate, supporting groundwater recharge or contain the stormwater to be released back into municipal stormwater management systems after a storm. Permeable paving systems have shown effective in reducing suspended solids, Biochemical Oxygen Demand (BOD), chemical oxygen demand, and ammonium concentrations within groundwater. In areas where infiltration is not possible due to unsuitable soil conditions, permeable pavements are used in the attenuation mode where water is retained in the pavement and slowly released to surface water systems between storm events. | 1 | Applied and Interdisciplinary Chemistry |
Impact wrenches, pulse tools, torque wrenches, screwdrivers, drills, grinders, die grinders, sanders, dental drills, tire changers and other pneumatic tools use a variety of air motors. These include vane type motors, turbines and piston motors. | 1 | Applied and Interdisciplinary Chemistry |
Khimera incorporates up to date achievements in the development of the wide range of models of elementary physicochemical processes; these models are of particular importance for hi-tech applications in:
*microelectronics
*materials science
*chemical industry
*automobile and aviation industry
*power engineering. | 0 | Theoretical and Fundamental Chemistry |
Solutions of methanesulfonic acid are used for the electroplating of tin and tin-lead solders. It is displacing the use of fluoroboric acid, which releases corrosive and volatile hydrogen fluoride.
Methanesulfonic acid is also a primary ingredient in rust and scale removers. It is used to clean off surface rust from ceramic, tiles and porcelain which are usually susceptible to acid attack. | 0 | Theoretical and Fundamental Chemistry |
For uniaxial extension in the -direction, the principal stretches are . From incompressibility . Hence .
Therefore,
The left Cauchy–Green deformation tensor can then be expressed as
If the directions of the principal stretches are oriented with the coordinate basis vectors, we have
If , we have
Therefore,
The engineering strain is . The engineering stress is | 0 | Theoretical and Fundamental Chemistry |
Traditionally, the recognition of protein-protein interactions was carried out through chemical cross-linking, that involved the use of moderately reactive bifunctional reagent, commonly attached to free amino groups. However, photochemical cross-linking is much more specific due to the short lifetime of the excited intermediates. In addition, photochemical cross-linking does not interfere with the antibodies recognition whilst the former does.
But photo-leucines advantages go further, because in addition to having a lot of advantages, it doesnt have negative effects. For example, although unnatural amino acids are in general toxic to cells, photo-leucine has been proved not to have any substantial effect to cell viability. Those results have been corroborate by many experiments. For example, an essay with Escherichia coli-galactosidase showed that the addition of either of the three photo-amino acids or of a mixture of them had no effect on enzyme activity. That helps to conclude that photo-amino acids are nontoxic to cultivated mammalian cells and can, at least partially, functionally replace their natural forms.
However, currently photo-reactive amino acids are used in combination with chemical cross-linkers in order to achieve the most reliable results possible within protein-protein interaction studies. | 0 | Theoretical and Fundamental Chemistry |
The heating (dry distilling) of wood causes tar and pitch to drip away from the wood and leave behind charcoal. Birchbark is used to make birch-tar, a particularly fine tar. The terms tar and pitch are often used interchangeably. However, pitch is considered more solid, while tar is more liquid. Traditionally, pitch that was used for waterproofing buckets, barrels and ships was drawn from pine. It is used to make Cutler's resin.
A 10th-century redaction of an earlier Greek Byzantine agricultural work brings down the ancient method of applying pitch to ceramic wine casks:
The ceramic ware was pitched, both inside and out, immediately while they were removed from the kiln and still hot. | 0 | Theoretical and Fundamental Chemistry |
Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur derivatives, e.g., saccharin. Nature is abound with organosulfur compounds—sulfur is vital for life. Of the 20 common amino acids, two (cysteine and methionine) are organosulfur compounds, and the antibiotics penicillin and sulfa drugs both contain sulfur. While sulfur-containing antibiotics save many lives, sulfur mustard is a deadly chemical warfare agent. Fossil fuels, coal, petroleum, and natural gas, which are derived from ancient organisms, necessarily contain organosulfur compounds, the removal of which is a major focus of oil refineries.
Sulfur shares the chalcogen group with oxygen, selenium, and tellurium, and it is expected that organosulfur compounds have similarities with carbon–oxygen, carbon–selenium, and carbon–tellurium compounds.
A classical chemical test for the detection of sulfur compounds is the Carius halogen method. | 0 | Theoretical and Fundamental Chemistry |
Carbon nanotubes and graphene-based materials can be used as electrocatalysts. The carbon surfaces of graphene and carbon nanotubes are well suited to the adsorption of many chemical species, which can promote certain electrocatalytic reactions. In addition, their conductivity means they are good electrode materials. Carbon nanotubes have a very high surface area, maximizing surface sites at which electrochemical transformations can occur. Graphene can also serve as a platform for constructing composites with other kinds of nanomaterials such as single atom catalysts. Because of their conductivity, carbon-based materials can potentially replace metal electrodes to perform metal-free electrocatalysis. | 0 | Theoretical and Fundamental Chemistry |
When inactive, the PKA apoenzyme exists as a tetramer which consists of two regulatory subunits and two catalytic subunits. The catalytic subunit contains the active site, a series of canonical residues found in protein kinases that bind and hydrolyse ATP, and a domain to bind the regulatory subunit. The regulatory subunit has domains to bind to cyclic AMP, a domain that interacts with catalytic subunit, and an auto inhibitory domain. There are two major forms of regulatory subunit; RI and RII.
Mammalian cells have at least two types of PKAs: type I is mainly in the cytosol, whereas type II is bound via its regulatory subunits and special anchoring proteins, described in the anchorage section, to the plasma membrane, nuclear membrane, mitochondrial outer membrane, and microtubules. In both types, once the catalytic subunits are freed and active, they can migrate into the nucleus (where they can phosphorylate transcription regulatory proteins), while the regulatory subunits remain in the cytoplasm.
The following human genes encode PKA subunits:
* catalytic subunit – PRKACA, PRKACB, PRKACG
* regulatory subunit type I - PRKAR1A, PRKAR1B
* regulatory subunit type II - PRKAR2A, PRKAR2B | 1 | Applied and Interdisciplinary Chemistry |
The RNA-editing system seen in the animal may have evolved from mononucleotide deaminases, which have led to larger gene families that include the apobec-1 and adar genes. These genes share close identity with the bacterial deaminases involved in nucleotide metabolism. The adenosine deaminase of E. coli cannot deaminate a nucleoside in the RNA; the enzymes reaction pocket is too small for the RNA strand to bind to. However, this active site is widened by amino acid changes in the corresponding human analog genes, APOBEC1 and ADAR', allowing deamination.
The gRNA-mediated pan-editing in trypanosome mitochondria, involving templated insertion of U residues, is an entirely different biochemical reaction. The enzymes involved have been shown in other studies to be recruited and adapted from different sources. But the specificity of nucleotide insertion via the interaction between the gRNA and mRNA is similar to the tRNA editing processes in the animal and Acanthamoeba mitochondria. Eukaryotic ribose methylation of rRNAs by guide RNA molecules is a similar form of modification.
Thus, RNA editing evolved more than once. Several adaptive rationales for editing have been suggested. Editing is often described as a mechanism of correction or repair to compensate for defects in gene sequences. However, in the case of gRNA-mediated editing, this explanation does not seem possible because if a defect happens first, there is no way to generate an error-free gRNA-encoding region, which presumably arises by duplication of the original gene region. A more plausible alternative for the evolutionary origins of this system is through constructive neutral evolution, where the order of steps is reversed, with the gratuitous capacity for editing preceding the "defect". | 1 | Applied and Interdisciplinary Chemistry |
In 1955, S. Winstein and T. G. Traylor published a study of the mechanism of acetolysis of organomercury compounds. They propose a series of possible mechanisms for the process, which they rule out through based on their kinetic data. A concerted metalation deprotonation is considered, and they are unable to rule it out through the data they collect.
The metalation of organic C–H bonds was extended from mercury to palladium in 1968 by J. M. Davidson and C. Triggs who identified that palladium acetate reacts with benzene in perchloric acid and acetic acid to give biphenyl, palladium(0), and 2 equivalents of acetic acid through an organopalladium intermediate. Early mechanistic studies found that palladium acetate was the best palladium precatalyst due to the presence of the acetate ligand. Mechanistic investigation has been ongoing since these initial discoveries, and infrared spectroscopy on the picosecond–millisecond time scale was used in 2021 to observe the states involved in proton transfer from acetic acid to a metalated ligand, which is the microscopic reverse of a concerted metalation deprotonation process. | 0 | Theoretical and Fundamental Chemistry |
The Marschalk reaction in chemistry is the sodium dithionite promoted reaction of a phenolic anthraquinone with an aldehyde to yield a substituted phenolic anthraquinone after the addition of acid.
The mechanism can be found in the book Named Reactions in Organic Chemistry, and its more intuitive version is provided below:
One of the first applications of this reaction was reported in 1985. | 0 | Theoretical and Fundamental Chemistry |
A variety of further synthetic procedures are particularly useful in opening carbocyclic and other rings, generally which contain a double bound or other functional group "handle" to facilitate chemistry; these are termed ring-opening reactions. Examples include:
* ring opening metathesis, which can also be used to accomplish a specific type of polymerization. | 0 | Theoretical and Fundamental Chemistry |
In biochemistry, a metabolon is a temporary structural-functional complex formed between sequential enzymes of a metabolic pathway, held together both by non-covalent interactions and by structural elements of the cell, such as integral membrane proteins and proteins of the cytoskeleton.
The formation of metabolons allows the intermediate product from one enzyme to be passed (channelling) directly into the active site of the next consecutive enzyme of the metabolic pathway. The citric acid cycle is an example of a metabolon that facilitates substrate channeling. Another example is the dhurrin synthesis pathway in sorghum, in which the enzymes assemble as a metabolon in lipid membranes. During the functioning of metabolons, the amount of water needed to hydrate the enzymes is reduced and enzyme activity is increased. | 1 | Applied and Interdisciplinary Chemistry |
Lorentz force flowmeters are usually classified in several main conceptual setups. Some of them designed as static flowmeters where the magnet system is at rest and one measures the force acting on it. Alternatively, they can be designed as rotary flowmeters where the magnets are arranged on a rotating wheel and the spinning velocity is a measure of the flow velocity. Obviously, the force acting on a Lorentz force flowmeter depends both on the velocity distribution and on the shape of the magnet system. This classification depends on the relative direction of the magnetic field that is being applied respect to the direction of the flow. In Figure 3 one can distinguish diagrams of the longitudinal and the transverse Lorentz force flowmeters.
It is important to mention that even that in figures only a coil or a magnet are sketched, the principle holds for both.
Rotary LFF consists of a freely rotating permanent magnet (or an array of magnets mounted on a flywheel as shown in figure 4), which is magnetized perpendicularly to the axle it is mounted on. When such a system is placed close to a duct carrying an electrically conducting fluid flow, it rotates so that the driving torque due to the eddy currents induced by the flow is balanced by the braking torque induced by the rotation itself. The equilibrium rotation rate varies directly with the flow velocity and inversely with the distance between the magnet and the duct. In this case it is possible to measure either the torque on the magnet system or the angular velocity at which the wheel spins. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to the general similarity in structure and function of the electron transport chains in eukaryotes, bacteria and archaea possess a large variety of electron-transfer enzymes. These use an equally wide set of chemicals as substrates. In common with eukaryotes, prokaryotic electron transport uses the energy released from the oxidation of a substrate to pump ions across a membrane and generate an electrochemical gradient. In the bacteria, oxidative phosphorylation in Escherichia coli is understood in most detail, while archaeal systems are at present poorly understood.
The main difference between eukaryotic and prokaryotic oxidative phosphorylation is that bacteria and archaea use many different substances to donate or accept electrons. This allows prokaryotes to grow under a wide variety of environmental conditions. In E. coli, for example, oxidative phosphorylation can be driven by a large number of pairs of reducing agents and oxidizing agents, which are listed below. The midpoint potential of a chemical measures how much energy is released when it is oxidized or reduced, with reducing agents having negative potentials and oxidizing agents positive potentials.
As shown above, E. coli can grow with reducing agents such as formate, hydrogen, or lactate as electron donors, and nitrate, DMSO, or oxygen as acceptors. The larger the difference in midpoint potential between an oxidizing and reducing agent, the more energy is released when they react. Out of these compounds, the succinate/fumarate pair is unusual, as its midpoint potential is close to zero. Succinate can therefore be oxidized to fumarate if a strong oxidizing agent such as oxygen is available, or fumarate can be reduced to succinate using a strong reducing agent such as formate. These alternative reactions are catalyzed by succinate dehydrogenase and fumarate reductase, respectively.
Some prokaryotes use redox pairs that have only a small difference in midpoint potential. For example, nitrifying bacteria such as Nitrobacter oxidize nitrite to nitrate, donating the electrons to oxygen. The small amount of energy released in this reaction is enough to pump protons and generate ATP, but not enough to produce NADH or NADPH directly for use in anabolism. This problem is solved by using a nitrite oxidoreductase to produce enough proton-motive force to run part of the electron transport chain in reverse, causing complex I to generate NADH.
Prokaryotes control their use of these electron donors and acceptors by varying which enzymes are produced, in response to environmental conditions. This flexibility is possible because different oxidases and reductases use the same ubiquinone pool. This allows many combinations of enzymes to function together, linked by the common ubiquinol intermediate. These respiratory chains therefore have a modular design, with easily interchangeable sets of enzyme systems.
In addition to this metabolic diversity, prokaryotes also possess a range of isozymes – different enzymes that catalyze the same reaction. For example, in E. coli, there are two different types of ubiquinol oxidase using oxygen as an electron acceptor. Under highly aerobic conditions, the cell uses an oxidase with a low affinity for oxygen that can transport two protons per electron. However, if levels of oxygen fall, they switch to an oxidase that transfers only one proton per electron, but has a high affinity for oxygen. | 1 | Applied and Interdisciplinary Chemistry |
The history of aluminium was shaped by the usage of its compound alum. The first written record of alum was in the 5th century BCE by Greek historian Herodotus. The ancients used it as a dyeing mordant, in medicine, in chemical milling, and as a fire-resistant coating for wood to protect fortresses from enemy arson. Aluminium metal was unknown. Roman writer Petronius mentioned in his novel Satyricon that an unusual glass had been presented to the emperor: after it was thrown on the pavement, it did not break but only deformed. It was returned to its former shape using a hammer. After learning from the inventor that nobody else knew how to produce this material, the emperor had the inventor executed so that it did not diminish the price of gold. Variations of this story were mentioned briefly in Natural History by Roman historian Pliny the Elder (who noted the story had "been current through frequent repetition rather than authentic") and Roman History by Roman historian Cassius Dio. Some sources suggest this glass could be aluminium. It is possible aluminium-containing alloys were produced in China during the reign of the first Jin dynasty (266–420).
After the Crusades, alum was a commodity of international commerce; it was indispensable in the European fabric industry. Small alum mines were worked in Catholic Europe but most alum came from the Middle East. Alum continued to be traded through the Mediterranean Sea until the mid-15th century, when the Ottomans greatly increased export taxes. In a few years, alum was discovered in great abundance in Italy. Pope Pius II forbade all imports from the east, using the profits from the alum trade to start a war with the Ottomans. This newly found alum long played an important role in European pharmacy, but the high prices set by the papal government eventually made other states start their own production; large-scale alum mining came to other regions of Europe in the 16th century. | 1 | Applied and Interdisciplinary Chemistry |
Because many definitions of standard temperature and pressure differ in temperature significantly from standard laboratory temperatures (e.g. 0 °C vs. ~25 °C), reference is often made to "standard laboratory conditions" (a term deliberately chosen to be different from the term "standard conditions for temperature and pressure", despite its semantic near identity when interpreted literally). However, what is a "standard" laboratory temperature and pressure is inevitably geography-bound, given that different parts of the world differ in climate, altitude and the degree of use of heat/cooling in the workplace. For example, schools in New South Wales, Australia use 25 °C at 100 kPa for standard laboratory conditions.
ASTM International has published Standard ASTM E41- Terminology Relating to Conditioning and hundreds of special conditions for particular materials and test methods. Other standards organizations also have specialized standard test conditions. | 0 | Theoretical and Fundamental Chemistry |
There are two types of target peptides directing to peroxisome, which are called peroxisomal targeting signals (PTS). One is PTS1, which is made of three amino acids on the C-terminus. The other is PTS2, which is made of a 9-amino-acid sequence often present on the N-terminus of the protein. | 1 | Applied and Interdisciplinary Chemistry |
Consider a rectangular channel of width much longer than the height. Let the distance between the top and bottom wall be and choose the coordinates such that lies in the midway between the two walls, with points perpendicular to the planes. Let both walls be porous with equal velocity . Then the continuity equation and Navier–Stokes equations for incompressible fluid become
with boundary conditions
The boundary conditions at the center is due to symmetry. Since the solution is symmetric above the plane , it is enough to describe only half of the flow, say for . If we look for a solution, that is independent of , the continuity equation dictates that the horizontal velocity can at most be a linear function of . Therefore, Berman introduced the following form,
where is the average value (averaged cross-sectionally) of at , that is to say
This constant will be eliminated out of the problem and will have no influence on the solution. Substituting this into the momentum equation leads to
Differentiating the second equation with respect to gives this can substituted into the first equation after taking the derivative with respect to which leads to
where is the Reynolds number. Integrating once, we get
with boundary conditions
This third order nonlinear ordinary differential equation requires three boundary condition and the fourth boundary condition is to determine the constant . and this equation is found to possess multiple solutions. The figure shows the numerical solution for low Reynolds number, solving the equation for large Reynolds number is not a trivial computation. | 1 | Applied and Interdisciplinary Chemistry |
In nuclear physics, transient equilibrium is a situation in which equilibrium is reached by a parent-daughter radioactive isotope pair where the half-life of the daughter is shorter than the half-life of the parent. Contrary to secular equilibrium, the half-life of the daughter is not negligible compared to parents half-life. An example of this is a molybdenum-99 generator producing technetium-99 for nuclear medicine diagnostic procedures. Such a generator is sometimes called a cow ' because the daughter product, in this case technetium-99, is milked at regular intervals. Transient equilibrium occurs after four half-lives, on average. | 0 | Theoretical and Fundamental Chemistry |
Vinyl and aryl Grignard reagents couple with primary alkyl halides in the presence of a catalytic amount of a copper(I) halide salt. The use of LiCuCl rather than simple copper(I) halide salts (CuX) improves yields of these coupling reactions.
The addition of Grignard reagents to alkynes is facilitated by a catalytic amount of copper halide. Transmetalation to copper and carbocupration are followed by transmetalation of the product alkene back to magnesium. The addition is syn unless a coordinating group is nearby in the substrate, in which case the addition becomes anti and yields improve. | 0 | Theoretical and Fundamental Chemistry |
In humans, two isoforms of glycogenin can be expressed: glycogenin-1, with a molecular weight of 37 kDa and codified by GYG1 gen, which is expressed mostly in muscles; and glycogenin-2, with a molecular weight of 66 kDa and codified by GYG2 gen, which is expressed mainly in liver, cardiac muscle and other types of tissue, but not in skeletal muscle.
Glycogenin-1 was described by analyzing the glycogen of skeletal muscle. It was determined that this molecule was united by a covalent bond to each mature molecule of muscular glycogen. | 1 | Applied and Interdisciplinary Chemistry |
Descaling agents are typically acidic compounds such as hydrochloric acid that react with the calcium carbonate and magnesium carbonate compounds present in the scale, producing carbon dioxide gas and a soluble salt.
Strongly acidic descaling agents are usually corrosive to the eyes and skin and can also attack and degrade clothing fibres, so appropriate protection such as rubber gloves and plastic aprons should be used in cleaning operations.
Descaling can also cause erosion and dezincification of brass, causing the brass to leach lead which is thereby released into potable water lines. Descaling of steam boilers such as those found in espresso machines can be difficult as the boilers do not fill completely and the descaling agent is unable to reach the top of the boiler. If this problem occurs the device's safety valves, probes, and pressure sensors may not be cleared of limescale. | 1 | Applied and Interdisciplinary Chemistry |
Sulfenamides are usually prepared by the reaction of sulfenyl chlorides and amines:
:RSCl + RNH → RSNR + HCl
The S-N bond formation generally obeys standard bimolecular nucleophilic substitution rules, with the basic nitrogen centre being the nucleophile. Primary sulfenamide formation as shown above occurs with the reaction of the sulfenyl halide with ammonia. Additionally primary as well as secondary and tertiary amines form sulfenamides through reaction with, thiols, disulfides, and sulfenyl thiocyanates. In one illustrative synthesis, triphenylmethanesulphenyl chloride and butylamine react in benzene at 25 C:
:PhCSCl + 2BuNH → PhCSN(H)Bu + BuNHCl
Many other routes to sulfenamides are known, starting from thiols and disulfides.
:RSSR + 2RNH + Ag → RSNR + AgSR + R'NH | 0 | Theoretical and Fundamental Chemistry |
In response to the arrival of food in the stomach and small intestine, the activity of the parasympathetic nervous system increases and the activity of the sympathetic nervous system decreases. This shift in the balance of autonomic tone towards the parasympathetic system results in a subjective state of low energy and a desire to be at rest, the opposite of the fight-or-flight state induced by high sympathetic tone. The larger the meal, the greater the shift in autonomic tone towards the parasympathetic system, regardless of the composition of the meal. | 1 | Applied and Interdisciplinary Chemistry |
Many cofactors (non-protein-based helper molecules) feature thiols. The biosynthesis and degradation of fatty acids and related long-chain hydrocarbons is conducted on a scaffold that anchors the growing chain through a thioester derived from the thiol Coenzyme A. The biosynthesis of methane, the principal hydrocarbon on Earth, arises from the reaction mediated by coenzyme M, 2-mercaptoethyl sulfonic acid. Thiolates, the conjugate bases derived from thiols, form strong complexes with many metal ions, especially those classified as soft. The stability of metal thiolates parallels that of the corresponding sulfide minerals. | 0 | Theoretical and Fundamental Chemistry |
Dolomitization is a geological process by which the carbonate mineral dolomite is formed when magnesium ions replace calcium ions in another carbonate mineral, calcite. It is common for this mineral alteration into dolomite to take place due to evaporation of water in the sabkha area. Dolomitization involves substantial amount of recrystallization. This process is described by the stoichiometric equation:
:2 CaCO + Mg ↔ CaMg(CO) + Ca
Dolomitization depends on specific conditions which include low Ca:Mg ratio in solution, reactant surface area, the mineralogy of the reactant, high temperatures which represents the thermodynamic stability of the system, and the presence of kinetic inhibitors such as sulfate.
If the kinetic inhibitors and high temperatures are compatible, then dolomitization can take place in saline environments above thermodynamic and kinetic saturation with respect to dolomite. This type of environment includes, freshwater and seawater mixing zones, normal saline to hypersaline subtidal environments, schizohaline environments (fluctuating salinity: fresh-water to hypersaline conditions) and hypersaline supratidal environments. When requirements are fulfilled, dolomitization can take place in alkaline environments which are those under the influence of bacterial reduction and fermentation processes, and areas with high input alkaline continental groundwaters. Environments with high temperatures (about 50 °C) such as subsurface and hydrothermal environments are conducive to dolomitization. | 0 | Theoretical and Fundamental Chemistry |
In 1977 the US Federal Drug Administration published a clinical trial guideline that excluded women of "childbearing potential" from the early phases of most clinical trials, which in practice led to their exclusion from later trial phases as well. This 1977 FDA guideline was implemented in response to a protectionist climate caused by the thalidomide tragedy. In the 1980s, a US task force on womens health concluded that a lack of womens health research (in part due to the FDA guideline) had compromised the amount and quality of information available about diseases and treatments affecting women. This led to the National Institute of Health policy that women should, when beneficial, be included in clinical trials. | 0 | Theoretical and Fundamental Chemistry |
There may exist proxies for salinity, but to date the main way that salinity has been measured has been by directly measuring chlorinity in pore fluids. Adkins et al. (2002) used pore fluid chlorinity in ODP cores, with the paleo-depth estimated from nearby coral horizons. Chlorinity was measured rather than pure salinity because the major ions in seawater are not constant with depth in the sediment column; for example, sulfate reduction and cation-clay interactions can change overall salinity, whereas chlorinity is not heavily affected. | 0 | Theoretical and Fundamental Chemistry |
Chemical and geological evidence indicate that photosynthetic cyanobacteria existed about 2.6 billion years ago and anoxygenic photosynthesis had been taking place since a billion years before that. Oxygenic photosynthesis was the primary source of free oxygen and led to the Great Oxidation Event roughly 2.4 to 2.1 billion years ago during the Neoarchean-Paleoproterozoic boundary. Although the end of the Great Oxidation Event was marked by a significant decrease in gross primary productivity that eclipsed extinction events, the development of aerobic respiration enabled more energetic metabolism of organic molecules, leading to symbiogenesis and the evolution of eukaryotes, and allowing the diversification of complex life on Earth. | 0 | Theoretical and Fundamental Chemistry |
In Huntleys second approach, he holds that it is sometimes useful (e.g., in fluid mechanics and thermodynamics) to distinguish between mass as a measure of inertia (inertial mass'), and mass as a measure of the quantity of matter. Quantity of matter is defined by Huntley as a quantity only to inertial mass, while not implicating inertial properties. No further restrictions are added to its definition.
For example, consider the derivation of Poiseuille's Law. We wish to find the rate of mass flow of a viscous fluid through a circular pipe. Without drawing distinctions between inertial and substantial mass, we may choose as the relevant variables:
There are three fundamental variables, so the above five equations will yield two independent dimensionless variables:
If we distinguish between inertial mass with dimension and quantity of matter with dimension , then mass flow rate and density will use quantity of matter as the mass parameter, while the pressure gradient and coefficient of viscosity will use inertial mass. We now have four fundamental parameters, and one dimensionless constant, so that the dimensional equation may be written:
where now only is an undetermined constant (found to be equal to by methods outside of dimensional analysis). This equation may be solved for the mass flow rate to yield Poiseuille's law.
Huntleys recognition of quantity of matter as an independent quantity dimension is evidently successful in the problems where it is applicable, but his definition of quantity of matter is open to interpretation, as it lacks specificity beyond the two requirements he postulated for it. For a given substance, the SI dimension amount of substance, with unit mole, does satisfy Huntleys two requirements as a measure of quantity of matter, and could be used as a quantity of matter in any problem of dimensional analysis where Huntley's concept is applicable. | 1 | Applied and Interdisciplinary Chemistry |
*Compressibility
*Mach number
*Diffusion
Gas dynamics is the overview of the average value in the distance between two molecules of gas that has collided with out ignoring the structure in which the molecules are contained. The field requires a great amount of knowledge and practical use in the ideas of the kinetic theory of gases, and it links the kinetic theory of gases with the solid state physics through the study of how gas reacts with surfaces. | 1 | Applied and Interdisciplinary Chemistry |
Lithium enolates, one of the precursors to silyl enol ethers, can also be generated from silyl enol ethers using methyllithium. The reaction occurs via nucleophilic substitution at the silicon of the silyl enol ether, producing the lithium enolate and tetramethylsilane. | 0 | Theoretical and Fundamental Chemistry |
The Langmuir adsorption model explains adsorption by assuming an adsorbate behaves as an ideal gas at isothermal conditions. According to the model, adsorption and desorption are reversible processes. This model even explains the effect of pressure i.e. at these conditions the adsorbate's partial pressure is related to its volume adsorbed onto a solid adsorbent. The adsorbent, as indicated in the figure, is assumed to be an ideal solid surface composed of a series of distinct sites capable of binding the adsorbate. The adsorbate binding is treated as a chemical reaction between the adsorbate gaseous molecule and an empty sorption site . This reaction yields an adsorbed species with an associated equilibrium constant :
From these basic hypotheses the mathematical formulation of the Langmuir adsorption isotherm can be derived in various independent and complementary ways: by the kinetics, the thermodynamics, and the statistical mechanics approaches respectively (see below for the different demonstrations).
The Langmuir adsorption equation is
where is the fractional occupancy of the adsorption sites, i.e., the ratio of the volume of gas adsorbed onto the solid to the volume of a gas molecules monolayer covering the whole surface of the solid and completely occupied by the adsorbate. A continuous monolayer of adsorbate molecules covering a homogeneous flat solid surface is the conceptual basis for this adsorption model. | 0 | Theoretical and Fundamental Chemistry |
London dispersion forces, named after the German-American physicist Fritz London, are weak intermolecular forces that arise from the interactive forces between instantaneous multipoles in molecules without permanent multipole moments. In and between organic molecules the multitude of contacts can lead to larger contribution of dispersive attraction, particularly in the presence of heteroatoms. London dispersion forces are also known as dispersion forces, London forces, or instantaneous dipole–induced dipole forces. The strength of London dispersion forces is proportional to the polarizability of the molecule, which in turn depends on the total number of electrons and the area over which they are spread. Hydrocarbons display small dispersive contributions, the presence of heteroatoms lead to increased LD forces as function of their polarizability, e.g. in the sequence RI>RBr>RCl>RF. In absence of solvents weakly polarizable hydrocarbons form crystals due to dispersive forces; their sublimation heat is a measure of the dispersive interaction. | 0 | Theoretical and Fundamental Chemistry |
Carboxypeptidases hydrolyze peptides at the first amide or polypeptide bond on the C-terminal end of the chain. Carboxypeptidases act by replacing the substrate water with a carbonyl (C=O) group. The carboxypeptidase A hydrolysis reaction has two mechanistic hypotheses, via a nucleophilic water and via an anhydride.
In the first proposed mechanism, a promoted-water pathway is favoured as Glu270 deprotonates the nucleophilic water. The Zn ion, along with positively charged residues, decreases the pKa of the bound water to approximately 7. Glu 270 has a dual role in this mechanism as it acts as a base to allow for the attack at the amide carbonyl group during nucleophilic addition. It acts as an acid during elimination when the water proton is transferred to the leaving nitrogen group. The oxygen on the amide carbonyl group does not coordinate to the Zn until the addition of the water. The deprotonation of the Zn coordinated water by Glu 270 provides an activated hydroxide nucleophile which attacks the amide carbonyl group in the peptide bond in a nucleophilic addition. The negatively charged intermediates that are formed during hydrolysis are stabilized by the Zn ion. The interaction between the carbonyl group and the neighbouring arginine, Arg 217, also stabilizes the negatively charged intermediates. The zinc-bound hydroxide interacts with the amide with the electrostatic stabilization of the transition state provided by the Zn ion and the neighbouring arginine.
The second proposed mechanism via an anhydride has similar steps but there is a direct attack of Glu270 on the carbonyl group, and then the interaction of Glu270 on the Zn-bound amide forms an anhydride instead which can subsequently be hydrolyzed by water. | 1 | Applied and Interdisciplinary Chemistry |
Selenium yeast is a feed additive for livestock, used to increase the selenium content in their fodder. It is a form of selenium currently approved for human consumption in the EU and Britain. Inorganic forms of selenium are used in feeds (namely sodium selenate and sodium selenite, which appear to work in roughly the same manner). Since these products can be patented, producers can demand premium prices. It is produced by fermenting Saccharomyces cerevisiae (baker's yeast) in a selenium-rich media.
There is considerable variability in products described as Se-yeast and the selenium compounds found within. Many manufacturers and products on the market are simply mixtures of largely inorganic selenium and some yeast. Selenium is found in different forms based upon the food in which it is found. For instance, the form found in mustard and garlic is different from the form found in wheat or corn. In some products, the added selenium is structurally substituted for sulfur in the amino acid methionine, thus forming an organic chemical called selenomethionine via the same pathways and enzymes. Owing to its similarity to sulfur-containing methionine, selenomethionine is mistaken for an amino acid by the yeast anabolism and incorporated in its proteins. It has been claimed that selenomethionine makes a better source of dietary selenium in animal nutrition, since it is an organic chemical compound sometimes found in some common crops such as wheat. | 1 | Applied and Interdisciplinary Chemistry |
*A phase is a form of matter that is homogeneous in chemical composition and physical state. Typical phases are solid, liquid and gas. Two immiscible liquids (or liquid mixtures with different compositions) separated by a distinct boundary are counted as two different phases, as are two immiscible solids.
*The number of components (C) is the number of chemically independent constituents of the system, i.e. the minimum number of independent species necessary to define the composition of all phases of the system.
*The number of degrees of freedom (F) in this context is the number of intensive variables which are independent of each other.
The basis for the rule is that equilibrium between phases places a constraint on the intensive variables. More rigorously, since the phases are in thermodynamic equilibrium with each other, the chemical potentials of the phases must be equal. The number of equality relationships determines the number of degrees of freedom. For example, if the chemical potentials of a liquid and of its vapour depend on temperature (T) and pressure (p), the equality of chemical potentials will mean that each of those variables will be dependent on the other. Mathematically, the equation , where , the chemical potential, defines temperature as a function of pressure or vice versa. (Caution: do not confuse as pressure with , number of phases.)
To be more specific, the composition of each phase is determined by intensive variables (such as mole fractions) in each phase. The total number of variables is , where the extra two are temperature T and pressure p. The number of constraints is , since the chemical potential of each component must be equal in all phases. Subtract the number of constraints from the number of variables to obtain the number of degrees of freedom as .
The rule is valid provided the equilibrium between phases is not influenced by gravitational, electrical or magnetic forces, or by surface area, and only by temperature, pressure, and concentration. | 0 | Theoretical and Fundamental Chemistry |
HNMT could be a potential target for the treatment of symptoms of methamphetamine overdose. It is a central nervous system stimulant, which can be abused up to the lethal consequences: numerous deaths related to methamphetamine overdoses have been reported. The reasoning behind this is that such overdose often leads to behavioral abnormalities, and it has been observed that elevated levels of histamine in the brain can attenuate these methamphetamine-induced behaviors. Therefore, by targeting HNMT, it might be possible to increase the levels of histamine in the brain, which could, in turn, help to mitigate the effects of a methamphetamine overdose. This effect could be achieved by using HNMT inhibitors. Studies predict that one such inhibitor can be metoprine, which crosses the blood-brain barrier and can potentially increase brain histamine levels by inhibiting HNMT; still, treatment of methamphetamine overdose by HNMT inhibitors is still an area of research. | 1 | Applied and Interdisciplinary Chemistry |
Flooding occurs when a watercourse is unable to convey the quantity of runoff flowing downstream. The frequency with which this occurs is described by a return period. Flooding is a natural process, which maintains ecosystem composition and processes, but it can also be altered by land use changes such as river engineering. Floods can be both beneficial to societies or cause damage. Agriculture along the Nile floodplain took advantage of the seasonal flooding that deposited nutrients beneficial for crops. However, as the number and susceptibility of settlements increase, flooding increasingly becomes a natural hazard. In urban areas, surface runoff is the primary cause of urban flooding, known for its repetitive and costly impact on communities. Adverse impacts span loss of life, property damage, contamination of water supplies, loss of crops, and social dislocation and temporary homelessness. Floods are among the most devastating of natural disasters. The use of supplemental irrigation is also recognized as a significant way in which crops such as maize can retain nitrogen fertilizers in soil, resulting in improvement of crop water availability. | 1 | Applied and Interdisciplinary Chemistry |
If the fecal sludge is liquid enough, it is usually collected by using vacuum pumps or centrifugal style booster pumps. A variety of manual and motorized devices designed to excavate thick and viscous sludge and accumulated trash are also available in the market.
After sitting for years in septic tanks and pit latrines, the accumulated sludge becomes hardened and is very difficult to remove. It is still common that workers enter pits in order to desludge them, even though this practice is generally unsafe and undesirable (in India, this practice is called "manual scavenging"). A number of low-cost pumping systems exist to remove this hardened sludge hygienically from the ground surface, although many of them are still in the experimental stage (e.g. Excravator, Gulper, e-Vac).
Fecal sludge can also be treated inside the tank or pit as well, by use of the "in-pit lime stabilization process", which treats the waste before it is removed from the tank or pit. Once removed, it is transported to onsite or off site treatment and processing facilities.
Some advanced transfer stations and vacuum trucks can dewater fecal sludge to some extent, and this water may be placed in sewer lines to be treated in wastewater treatment plants. This allows more sludge to be dealt with more efficiently and may constitute one of the best cases of co-treatment of fecal sludge in wastewater treatment plants. | 1 | Applied and Interdisciplinary Chemistry |
* [http://dspace.mit.edu/handle/1721.1/50230 MIT Open Access Articles].
* (manuscript).
* In the foreword by the president of ENEA the belief is expressed that the cold fusion phenomenon is proved. | 0 | Theoretical and Fundamental Chemistry |
Rather than one large central plant, that has to be fed a large amount of feedstock, such as a refinery that can unload a tanker shipment of petroleum if located next to an ocean, the discipline of process miniaturization envisions the distribution of the process technology to areas where the feedstock is not readily transportable in large quantities to a large centralized processing plant. The miniaturized process technology may simply involve transformation of solid biomass materials from multiple distributed microprocesses into more easily manageable fluids. The fluids can then be transported or distributed to larger-scale intelligent processing nodes using conventional fluid transport technology.
Historically, small processes or microprocesses per se have always existed. For example, small vineyards and breweries have produced feedstock, processed it, and stored product in what could be considered “microprocess” when compared to processes designed based on the petrochemical industry model or, for example, large-scale production of beer. Small villages in India and other places in the world have learned to produce biogas from animal manure in what could be considered small-scale microprocesses for the production of energy. However, microprocesses and process miniaturization as a design philosophy includes the notion of approaching total automation, and is a new technology which has been enabled by computer hardware miniaturization, for example, the microprocessor. It is easy to envision processes which can be mass-produced and transported. For example, many appliances such as air conditioners, domestic washing machines, and refrigerators could be considered microprocesses.
The design philosophy of process miniaturization envisions that “scale-down” of complex processes involving multiple process unit operations can be achieved, and that economy of scale will be more related to the size of a network of distributed autonomous microprocesses. Since failure of one autonomous microprocess does not cause shutdown of the entire network, microprocesses will lead to more economically efficient, robust, and stable production of products that have traditionally been produced for a petroleum-based society.
Since fossil fuels by definition are being consumed and are non-renewable, future fuel and materials will be based on renewable biomass. | 1 | Applied and Interdisciplinary Chemistry |
The isothermal compressibility is generally related to the isentropic (or adiabatic) compressibility by a few relations:
where is the heat capacity ratio, is the volumetric coefficient of thermal expansion, is the particle density, and is the thermal pressure coefficient.
In an extensive thermodynamic system, the application of statistical mechanics shows that the isothermal compressibility is also related to the relative size of fluctuations in particle density:
where is the chemical potential.
The term "compressibility" is also used in thermodynamics to describe deviations of the thermodynamic properties of a real gas from those expected from an ideal gas.
The compressibility factor is defined as
where is the pressure of the gas, is its temperature, and is its molar volume, all measured independently of one another. In the case of an ideal gas, the compressibility factor is equal to unity, and the familiar ideal gas law is recovered:
can, in general, be either greater or less than unity for a real gas.
The deviation from ideal gas behavior tends to become particularly significant (or, equivalently, the compressibility factor strays far from unity) near the critical point, or in the case of high pressure or low temperature. In these cases, a generalized compressibility chart or an alternative equation of state better suited to the problem must be utilized to produce accurate results. | 1 | Applied and Interdisciplinary Chemistry |
Recent excavations in Middle Ganges Valley conducted by archaeologist Rakesh Tewari show iron working in India may have begun as early as 1800 BCE. Archaeological sites in India, such as Malhar, Dadupur, Raja Nala Ka Tila and Lahuradewa in the state of Uttar Pradesh show iron implements in the period between 1800 BCE-1200 BCE. Sahi (1979: 366) concluded that by the early 13th century BCE, iron smelting was definitely practiced on a bigger scale in India, suggesting that the date the technology's early period may well be placed as early as the 16th century BCE.
Some of the early iron objects found in India are dated to 1400 BCE by employing the method of radio carbon dating. Spikes, knives, daggers, arrow-heads, bowls, spoons, saucepans, axes, chisels, tongs, door fittings etc. ranging from 600 BCE—200 BCE have been discovered from several archaeological sites. In Southern India (present day Mysore) iron appeared as early as the 12th or 11th century BCE. These developments were too early for any significant close contact with the northwest of the country.
The earliest available Bronze age swords of copper discovered from the Harappan sites in Pakistan date back to 2300 BCE. Swords have been recovered in archaeological findings throughout the Ganges-Jamuna Doab region of India, consisting of bronze but more commonly copper. Diverse specimens have been discovered in Fatehgarh, where there are several varieties of hilt. These swords have been variously dated to periods between 1700 and 1400 BCE, but were probably used more extensively during the opening centuries of the 1st millennium BCE.
The beginning of the 1st millennium BCE saw extensive developments in iron metallurgy in India. Technological advancement and mastery of iron metallurgy was achieved during this period of peaceful settlements. The years between 322 and 185 BCE saw several advancements being made to the technology involved in metallurgy during the politically stable Maurya period (322—185 BCE). Greek historian Herodotus (431—425 BCE) wrote the first western account of the use of iron in India.
Perhaps as early as 300 BCE—although certainly by 200 CE—high quality steel was being produced in southern India by what Europeans would later call the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in a crucible and heated until the iron melted and absorbed the carbon. The first crucible steel was the wootz steel that originated in India before the beginning of the common era. Wootz steel was widely exported and traded throughout ancient Europe, China, the Arab world, and became particularly famous in the Middle East, where it became known as Damascus steel. Archaeological evidence suggests that this manufacturing process was already in existence in South India well before the common era.
Zinc mines of Zawar, near Udaipur, Rajasthan, were active during 400 BCE. There are references of medicinal uses of zinc in the Charaka Samhita (300 BCE). The Rasaratna Samuccaya (800 CE) explains the existence of two types of ores for zinc metal, one of which is ideal for metal extraction while the other is used for medicinal purpose. The Periplus Maris Erythraei mentions weapons of Indian iron and steel being exported from India to Greece. | 1 | Applied and Interdisciplinary Chemistry |
Confusion between "grassed waterway" and "vegetative filter strips" should be avoided. The latter are generally narrower (only a few metres wide) and rather installed along rivers as well as along or within cultivated fields. However, buffer strip can be a synonym, with shrubs and trees added to the plant component, as does a riparian zone. | 1 | Applied and Interdisciplinary Chemistry |
Although antibodies exhibit nanomolar affinities toward protein antigens, the specificity against glycans is very limited. In fact, available antibodies may bind only <4% of the 7000 mammalian glycan antigens; moreover, most of those antibodies have low affinity and exhibit cross-reactivity. | 1 | Applied and Interdisciplinary Chemistry |
The MIQE guidelines were created due to the low quality of qPCR data submitted to academic journals at the time, which was only becoming more common as Next Generation Sequencing machinery allowed for such experiments to be run for a cheaper cost. Because the technique is utilized across all of science in multiple fields, the instruments, methods, and designs of how qPCR is used differs greatly. To help improve overall quality, the MIQE guidelines were made as generalized suggestions on basic experimental procedures and forms of data that should be collected as a minimum level of reported information for other researchers to understand and use when reading the published material. Setting up a recognized and largely agreed upon set of guidelines such as these was deemed important by the scientific community especially due to the ever increasing amount of scientific work coming from developing countries with many different languages and protocols. | 1 | Applied and Interdisciplinary Chemistry |
In alchemy, fixation is a process by which a previously volatile substance is "transformed" into a form (often solid) that is not affected by fire. It separates the substance or object and puts it back in the same or different shape at a subatomic level.
Fixation is sometimes listed as one of the processes required for transformation of a substance, or completion of the alchemical magnum opus. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, the square planar molecular geometry describes the stereochemistry (spatial arrangement of atoms) that is adopted by certain chemical compounds. As the name suggests, molecules of this geometry have their atoms positioned at the corners. | 0 | Theoretical and Fundamental Chemistry |
Until recently, real-time monitoring of BOD was unattainable owing to its complex nature. Recent research by a leading UK university has discovered the link between multiple water quality parameters including electrical conductivity, turbidity, TLF and CDOM. These parameters are all capable of being monitored in real-time through a combination of traditional methods (electrical conductivity via electrodes) and newer methods such as fluorescence. The monitoring of tryptophan-like fluorescence (TLF) has been successfully utilised as a proxy for biological activity and enumeration, particularly with a focus on Escherichia coli (E. Coli). TLF based monitoring is applicable across a wide range of environments, including but by no means limited to sewage treatment works and freshwaters. Therefore, there has been a significant movement towards combined sensor systems that can monitor parameters and use them, in real-time, to provide a reading of BOD that is of laboratory quality. | 0 | Theoretical and Fundamental Chemistry |
Exorphins are exogenous opioid peptides, distinguished from endorphins, or endogenous opioid peptides.
Exorphins include opioid food peptides like gluten exorphin and microbial opioid peptides and any other opioid peptide foreign to a host that have metabolic efficacy for that host. Exorphins can be converted from plants and animals but also dairy products and certain vegetables like spinach and soy.
Exorphins can be released for many different kinds of proteins and thus can be isolated from various sources such as from plant proteins or from enzymes of the digestive system of animals. The study of exorphins as a bioactive peptide can be a source of discovery for new kinds of food and drugs to treat and prevent diseases associated with the accumulation of exorphins. | 1 | Applied and Interdisciplinary Chemistry |
In Europe and Australia, ductile iron pipe is typically manufactured with a zinc coating overlaid by either a bituminous, polymeric, or epoxy finishing layer. EN 545/598 mandates a minimum zinc content of 200 g/m (at 99.99% purity) and a minimum average finishing layer thickness of 70 μm (with local minimum of 50 μm). AS/NZS 2280 mandates a minimum zinc content of 200 g/m (with a local minimum of 180 g/m at 99.99% purity) and a minimum average finishing layer thickness of 80 μm.
No current AWWA standards are available for bonded coatings (zinc, coal tar epoxy, tape-wrap systems as seen on steel pipe) for ductile iron pipe, DIPRA does not endorse bonded coatings, and AWWA M41 generally views them unfavourably, recommending they be used only in conjunction with cathodic protection. | 1 | Applied and Interdisciplinary Chemistry |
A range of bacteria can grow on sulfoquinovose or its glycosides as sole carbon source. E. coli can grow on sulfoquinovose, methyl α-sulfoquinovoside and α-sulfoquinovosyl glycerol. Growth on sulfoquinovosyl glycerol is both faster and leads to higher cell density than for growth on sulfoquinovose. Pseudomonas aeruginosa strain SQ1, Klebsiella sp. strain ABR11, Klebsiella oxytoca TauN1, Agrobacterium sp. strain ABR2, and Bacillus aryabhattai can grow on sulfoquinovose as sole carbon source. A strain of Flavobacterium was identified that could grow on methyl α-sulfoquinovoside. | 1 | Applied and Interdisciplinary Chemistry |
While the MPT modulation has been widely studied, little is known about its structure. Initial experiments by Szabó and Zoratti proposed the MPT may comprise Voltage Dependent Anion Channel (VDAC) molecules. Nevertheless, this hypothesis was shown to be incorrect as VDAC mitochondria were still capable to undergo MPT. Further hypothesis by Halestrap's group convincingly suggested the MPT was formed by the inner membrane Adenine Nucleotide Translocase (ANT), but genetic ablation of such protein still led to MPT onset. Thus, the only MPTP components identified so far are the TSPO (previously known as the peripheral benzodiazepine receptor) located in the mitochondrial outer membrane and cyclophilin-D in the mitochondrial matrix. Mice lacking the gene for cyclophilin-D develop normally, but their cells do not undergo Cyclosporin A-sensitive MPT, and they are resistant to necrotic death from ischemia or overload of Ca or free radicals. However, these cells do die in response to stimuli that kill cells through apoptosis, suggesting that MPT does not control cell death by apoptosis. | 1 | Applied and Interdisciplinary Chemistry |
In the pedosphere it is safe to assume that gases are in equilibrium with the atmosphere. Because plant roots and soil microbes release CO to the soil, the concentration of bicarbonate () in soil waters is much greater than that in equilibrium with the atmosphere, the high concentration of CO and the occurrence of metals in soil solutions results in lower pH levels in the soil. Gases that escape from the pedosphere to the atmosphere include the gaseous byproducts of carbonate dissolution, decomposition, redox reactions and microbial photosynthesis. The main inputs from the atmosphere are aeolian sedimentation, rainfall and gas diffusion. Eolian sedimentation includes anything that can be entrained by wind or that stays suspended in air and includes a wide variety of aerosol particles, biological particles like pollen, and dust particles. Nitrogen is the most abundant constituent in rain (after water), as water vapor utilizes aerosol particles to nucleate rain droplets. | 0 | Theoretical and Fundamental Chemistry |
The basic mechanism of the Payne rearrangement involves deprotonation of the free hydroxyl group, invertive nucleophilic attack on the proximal epoxide carbon, and re-protonation of the newly freed alkoxide. Each step of the process is reversible.
Several observations suggest that this mechanistic picture is oversimplified. Epoxide migration either does not occur or is very sluggish under aprotic conditions—it has been suggested that nucleophilic attack is slowed by the coordination of metal ions to the nucleophilic oxygen under aprotic conditions. In addition, when an external nucleophile is added to equilibrating epoxide isomers, the ratio of opened products does not reflect the ratio of epoxide isomers in solution or their relative thermodynamic stability. In situ nucleophilic opening of equilibrating epoxides is an example of Curtin-Hammett conditions—because the epoxides are equilibrating rapidly relative to the rate of epoxide opening, it is the kinetic barriers of ring opening that control the observed product ratio. In the example below, the product of opening of the terminal epoxide is the major product, even though the terminal epoxide itself is less thermodynamically stable than the internal isomer.
Halo diols may be used as precursors to 2,3-epoxy alcohols prior to rearrangement. Issues of site selectivity may arise if the two hydroxyl groups flanking the halide are not equivalent. In general, the formation of internal, substituted epoxides is more rapid than the formation of terminal epoxides. This idea can be used to predict the course of migrations of in situ-generated epoxides. | 0 | Theoretical and Fundamental Chemistry |
DPN is a direct write technique so it can be used for top-down and bottom-up lithography applications. In top-down work, the tips are used to deliver an etch resist to a surface, which is followed by a standard etching process. In bottom-up applications, the material of interest is delivered directly to the surface via the tips. | 1 | Applied and Interdisciplinary Chemistry |
Forgione, P., Bilodeau, F. et al. reported that heteroatoms containing a carboxylic acid also are tolerated by palladium monometallic systems and undergo decarboxylative cross coupling with aryl halides. In the proposed mechanism the initial step is oxidative addition of the aryl halide forming an aryl–palladium intermediate. Electrophilic palladation then occurs at carbon-3 of the heteroatom. From this intermediate there are two possible pathways for the cycle to continue on. The first is palladium migration from carbon-3 to carbon-2 along with the expulsion of carbon dioxide. This forms the aryl–palladium–heteroatom intermediate, which undergoes reductive elimination to form the final heteroaromatic compound. The second pathway only occurs when R is a proton. If this is the case, deprotonation occurs to regain aromaticity of the heteroatom. This intermediate then undergoes reductive elimination, coupling the aryl to the carbon-3 position of the heteroatom. As this compound still contains the carboxylic acid it is then free to re enter the catalytic cycle where it undergoes coupling at the carbon 2 position, along with the expulsion of carbon dioxide to form a biaryl heteroatom. As this pathway competes with the decarboxylation step, two products are formed making this reaction less selective. As a result, heteroatoms, which are substituted at the carbon 3 position and are more favored due to the higher level of control they provide. | 0 | Theoretical and Fundamental Chemistry |
In interfacial shear rheology, the interfacial area remains the same throughout the measurement. Instead, the interfacial area is sheared in order to be able to measure the surface stress present. The equations are similar to dilatational interfacial rheology but shear modulus is often marked with G instead of E like in dilational methods. In a general case, G and E are not equal.
Since interfacial rheological properties are relatively weak, it causes challenges for the measurement equipment. For high sensitivity, it is essential to maximize the contribution of the interface while minimizing the contribution of the bulk phase. The Boussinesq number, Bo, depicts how sensitive a measurement method is for detecting the interfacial viscoelasticity.
The commercialized measurement techniques for interfacial shear rheology include magnetic needle method, rotating ring method and rotating bicone method. The magnetic needle method, developed by Brooks et al., has the highest Boussinesq number of the commercialized methods. In this method, a thin magnetic needle is oscillated at the interface using a magnetic field. By following the movement of the needle with a camera, the viscoelastic properties of the interface can be detected. This method is often used in combination with a Langmuir trough in order to be able to conduct the experiment as a function of the packing density of the molecules or particles. | 0 | Theoretical and Fundamental Chemistry |
Cannabis Analytical Science Program (CASP) is a forum where the science of hemp and cannabis analysis can be discussed and cannabis standards and methods developed. | 0 | Theoretical and Fundamental Chemistry |
As series resistance increases, the voltage drop between the junction voltage and the terminal voltage becomes greater for the same current. The result is that the current-controlled portion of the I-V curve begins to sag toward the origin, producing a significant decrease in the terminal voltage V and a slight reduction in I, the short-circuit current. Very high values of R will also produce a significant reduction in I; in these regimes, series resistance dominates and the behavior of the solar cell resembles that of a resistor. These effects are shown for crystalline silicon solar cells in the I-V curves displayed in the figure to the right.
Losses caused by series resistance are in a first approximation given by P = VI = IR and increase quadratically with (photo-)current. Series resistance losses are therefore most important at high illumination intensities. | 0 | Theoretical and Fundamental Chemistry |
A number of computational tools have been developed for the prediction of the location of binding sites on proteins. These can be broadly classified into sequence based or structure based. Sequence based methods rely on the assumption that the sequences of functionally conserved portions of proteins such as binding site are conserved. Structure based methods require the 3D structure of the protein. These methods in turn can be subdivided into template and pocket based methods. Template based methods search for 3D similarities between the target protein and proteins with known binding sites. The pocket based methods search for concave surfaces or buried pockets in the target protein that possess features such as hydrophobicity and hydrogen bonding capacity that would allow them to bind ligands with high affinity. Even though the term pocket is used here, similar methods can be used to predict binding sites used in protein-protein interactions that are usually more planar, not in pockets. | 1 | Applied and Interdisciplinary Chemistry |
Dioxane has affected groundwater supplies in several areas. Dioxane at the level of 1 μg/L (~1 ppb) has been detected in many locations in the US. In the U.S. state of New Hampshire, it had been found at 67 sites in 2010, ranging in concentration from 2 ppb to over 11,000 ppb. Thirty of these sites are solid waste landfills, most of which have been closed for years. In 2019, the Southern Environmental Law Center successfully sued Greensboro, North Carolina's Wastewater treatment after 1,4-Dioxane was found at 20 times above EPA safe levels in the Haw River. | 0 | Theoretical and Fundamental Chemistry |
Pre-synthesized LAGP powders can be sprayed on a substrate to form a LAGP film by means of aerosol deposition. The powders are loaded into the aerosol deposition chamber and purified air is used as the carrier gas to drive the particles towards the substrate, where they impinge and coalesce to generate the film. Since the as-produced film is amorphous, an annealing treatment is usually performed to improve the film crystallinity and its conduction properties. | 0 | Theoretical and Fundamental Chemistry |
Synthetic molecular motors are molecular machines capable of continuous directional rotation under an energy input. Although the term "molecular motor" has traditionally referred to a naturally occurring protein that induces motion (via protein dynamics), some groups also use the term when referring to non-biological, non-peptide synthetic motors. Many chemists are pursuing the synthesis of such molecular motors.
The basic requirements for a synthetic motor are repetitive 360° motion, the consumption of energy and unidirectional rotation. The first two efforts in this direction, the chemically driven motor by Dr. T. Ross Kelly of Boston College with co-workers and the light-driven motor by Ben Feringa and co-workers, were published in 1999 in the same issue of Nature.
As of 2020, the smallest atomically precise molecular machine has a rotor that consists of four atoms. | 0 | Theoretical and Fundamental Chemistry |
Asymmetric hydrogenation is a chemical reaction that adds two atoms of hydrogen to a target (substrate) molecule with three-dimensional spatial selectivity. Critically, this selectivity does not come from the target molecule itself, but from other reagents or catalysts present in the reaction. This allows spatial information (what chemists refer to as chirality) to transfer from one molecule to the target, forming the product as a single enantiomer. The chiral information is most commonly contained in a catalyst and, in this case, the information in a single molecule of catalyst may be transferred to many substrate molecules, amplifying the amount of chiral information present. Similar processes occur in nature, where a chiral molecule like an enzyme can catalyse the introduction of a chiral centre to give a product as a single enantiomer, such as amino acids, that a cell needs to function. By imitating this process, chemists can generate many novel synthetic molecules that interact with biological systems in specific ways, leading to new pharmaceutical agents and agrochemicals. The importance of asymmetric hydrogenation in both academia and industry contributed to two of its pioneers — William Standish Knowles and Ryōji Noyori — being collectively awarded one half of the 2001 Nobel Prize in Chemistry. | 0 | Theoretical and Fundamental Chemistry |
;In marine species of the food web
Bioaccumulation controls internal concentrations of pollutants, including PFAS, in individual organisms. When bioaccumulation is looked at in the perspective of the entire food web, it is called biomagnification, which is incredibly important to track because lower concentrations of pollutants in environmental matrices such as seawater or sediments, can very quickly grow to harmful concentrations in organisms at higher trophic levels, including humans. Notably, concentrations in biota can even by >5000 times those present in water for PFOS and C10-C14 PFCAs. PFAS can enter an organism by ingestion of sediment, through the water, or directly via their diet. It accumulates namely in areas with high protein content, in the blood and liver, but its also found to a lesser extent in tissues.
Biomagnification can be described using the estimation of the trophic magnification factor (TMF), this describes the relationship between the contamination levels in a species and their trophic level in the food web. TMFs are determined by graphing the log transformed concentrations of PFAS against the assigned trophic level, and taking the antilog of the regression slope (10).
In a study done on a macrotidal estuary in Gironde, SW France, TMFs were >1 for nearly all 19 PFAS compounds considered in the study and were particularly high for PFOA and PFNA (6.0 and 3.1 respectively). A TMF> 1 means that accumulation in the organism is greater than that of the medium, in this case the medium being sea water.
PFOS, a long chain sulfonic acid, was found at the highest concentrations relative to other PFASs measured in fish and birds in Northern seas such as the Barents Sea and the Canadian Arctic. A study and an interactive map by the EWG using its results showed freshwater fish in the U.S. ubiquitously contain high levels of harmful PFAS, with a single serving typically significantly increasing the blood PFOS level.
Bioaccumulation and biomagnification of PFASs in marine species throughout the food web, particularly frequently consumed fish and shellfish, can have important impacts on human populations. PFASs have been frequently documented in both fish and shellfish that are commonly consumed by human populations, which poses health risks to humans and studies on the bioaccumulation in certain species are important to determine daily tolerable limits for human consumption, and where those limits may be exceeded causing potential health risks. This has particular implications for populations that consume larger numbers of wild fish and shellfish species. In addition to health risks, populations may be impacted by advisories, limits of fishing closures for certain species that are put in place to help mitigate health risks from potential consumption of species with higher levels of accumulated PFASs, but result in a loss of food sources and important subsistence species depended on by local communities. There is research being done in this area, including into spatial patterns of PFAS bioaccumulation in fish and crustaceans. | 0 | Theoretical and Fundamental Chemistry |
Van Bekkum was born on 26 September 1932 in Rotterdam. He studied technological chemistry at Delft University of Technology and graduated in 1959. He subsequently worked two years for Royal Dutch Shell before returning to Delft University to work as lecturer. In 1971 he was named professor of Catalysis in Organic Chemistry. From 1975 to 1976 he served as rector magnificus of the university. As professor van Bekkum specialized in carbohydrate chemistry and the study of zeolites. In 1995 van Bekkum was appointed as the first president of the newly-founded Federation of the European Zeolite Association.
In 1998 he officially retired, however, by 2013 he was still working at the university. In his period at Delft University van Bekkum was doctoral advisor to 75 students.
Van Bekkum was elected member of the Royal Netherlands Academy of Arts and Sciences in 1995. He became an honorary member of the Royal Netherlands Chemical Society in 1998.
Apart from his career in chemistry van Bekkum was a competitive chess player.
He died on 30 November 2020 in Rotterdam, at age 88. | 0 | Theoretical and Fundamental 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 | 0 | Theoretical and Fundamental Chemistry |
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems.
The nitrogen cycle is of particular interest to ecologists because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers, and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle. Human modification of the global nitrogen cycle can negatively affect the natural environment system and also human health. | 1 | Applied and Interdisciplinary Chemistry |
For an amino acid with only one amine and one carboxyl group, the pI can be calculated from the mean of the pKas of this molecule.
The pH of an electrophoretic gel is determined by the buffer used for that gel. If the pH of the buffer is above the pI of the protein being run, the protein will migrate to the positive pole (negative charge is attracted to a positive pole). If the pH of the buffer is below the pI of the protein being run, the protein will migrate to the negative pole of the gel (positive charge is attracted to the negative pole). If the protein is run with a buffer pH that is equal to the pI, it will not migrate at all. This is also true for individual amino acids. | 0 | Theoretical and Fundamental Chemistry |
2-Furoic acid crystals are highly transparent in the 200–2000 nm wavelength region, are stable up to 130 °C, and generally have low absorption in the UV, visible, and IR ranges. In optical and dielectric studies, 2-furoic acid crystals may act as paraelectrics in the temperature range < 318 K and ferroelectrics in temperature ranges > 318 K. | 0 | Theoretical and Fundamental Chemistry |
Terrestrial planets are believed to have come from the same nebular material as the giant planets, but they have lost most of the lighter elements and have different histories. Planets closer to the Sun might be expected to have a higher fraction of refractory elements, but if their later stages of formation involved collisions of large objects with orbits that sampled different parts of the Solar System, there could be little systematic dependence on position.
Direct information on Mars, Venus and Mercury largely comes from spacecraft missions. Using gamma-ray spectrometers, the composition of the crust of Mars has been measured by the Mars Odyssey orbiter, the crust of Venus by some of the Venera missions to Venus, and the crust of Mercury by the MESSENGER spacecraft. Additional information on Mars comes from meteorites that have landed on Earth (the Shergottites, Nakhlites, and Chassignites, collectively known as SNC meteorites). Abundances are also constrained by the masses of the planets, while the internal distribution of elements is constrained by their moments of inertia.
The planets condensed from the solar nebula, and much of the details of their composition are determined by fractionation as they cooled. The phases that condense fall into five groups. First to condense are materials rich in refractory elements such as Ca and Al. These are followed by nickel and iron, then magnesium silicates. Below about 700 kelvins (700 K), FeS and volatile-rich metals and silicates form a fourth group, and in the fifth group FeO enter the magnesium silicates. The compositions of the planets and the Moon are chondritic, meaning that within each group the ratios between elements are the same as in carbonaceous chondrites.
The estimates of planetary compositions depend on the model used. In the equilibrium condensation model, each planet was formed from a feeding zone in which the compositions of solids were determined by the temperature in that zone. Thus, Mercury formed at 1400 K, where iron remained in a pure metallic form and there was little magnesium or silicon in solid form; Venus at 900 K, so all the magnesium and silicon condensed; Earth at 600 K, so it contains FeS and silicates; and Mars at 450 K, so FeO was incorporated into magnesium silicates. The greatest problem with this theory is that volatiles would not condense, so the planets would have no atmospheres and Earth no atmosphere.
In chondritic mixing models, the compositions of chondrites are used to estimate planetary compositions. For example, one model mixes two components, one with the composition of C1 chondrites and one with just the refractory components of C1 chondrites. In another model, the abundances of the five fractionation groups are estimated using an index element for each group. For the most refractory group, uranium is used; iron for the second; the ratios of potassium and thallium to uranium for the next two; and the molar ratio FeO/(FeO+MgO) for the last. Using thermal and seismic models along with heat flow and density, Fe can be constrained to within 10 percent on Earth, Venus, and Mercury. U can be constrained within about 30% on Earth, but its abundance on other planets is based on "educated guesses". One difficulty with this model is that there may be significant errors in its prediction of volatile abundances because some volatiles are only partially condensed. | 0 | Theoretical and Fundamental Chemistry |
A number of SRCD beamlines exist, or are being constructed (), around the world as listed in the table.
As of 2022 components from former SRCD beamline CD12 (on [https://www.ibpt.kit.edu/kara.php KARA]) are now installed on the [https://www.synchrotron-soleil.fr/en/beamlines/disco DISCO] beamline
This facility also runs as part of the Beijing Electron Positron Collider (BEPC)
Two modules (A and B) exist on this beamline
This beamline is under construction and received its "first light" as of June 2023 | 0 | Theoretical and Fundamental Chemistry |
Many of the species that form harmful algae blooms will undergo a dual-stage life system. These species will alternate between a benthic resting stage and a pelagic vegetative state. The benthic resting stage corresponds to when these species are resting near the ocean floor. In this stage, the species cells are waiting for optimal conditions so that they can move towards the surface. These species will then transition from the benthic resting stage into the pelagic vegetative state - where they are more active and found near the water body surface. In the pelagic vegetative state, these cells are able to grow and multiply. It is within the pelagic vegetative state that a bloom is able to occur - as the cells rapidly reproduce and take over the upper regions of the body of water. The transition between these two life stages can have multiple effects on the algae bloom (such as rapid termination of the HAB as cells convert from the pelagic state to the benthic state). Many of the algal species that undergo this dual-stage life cycle are capable of rapid vertical migration. This migration is required for the movement from the benthic area of bodies of water to the pelagic zone. These species require immense amounts of energy as they pass through the various thermoclines, haloclines, and pycnoclines that are associated with the bodies of water in which these cells exist. | 0 | Theoretical and Fundamental Chemistry |
The purpose of the USNCO is to stimulate all young people to achieve excellence in chemistry. Therefore, the focus of the exam is not necessarily to select the top twenty students, and instead to present a wide selection of basic questions. Therefore, the scope of the USNCO is different than the scope of what would be expected at the training camp or IChO. | 1 | Applied and Interdisciplinary Chemistry |
Forming a composite of a material with (ordinary) positive thermal expansion with a material with (anomalous) negative thermal expansion could allow for tailoring the thermal expansion of the composites or even having composites with a thermal expansion close to zero. Negative and positive thermal expansion hereby compensate each other to a certain amount if the temperature is changed. Tailoring the overall thermal expansion coefficient (CTE) to a certain value can be achieved by varying the volume fractions of the different materials contributing to the thermal expansion of the composite.
Especially in engineering there is a need for having materials with a CTE close to zero i.e. with constant performance over a large temperature range e.g. for application in precision instruments. But also in everyday life materials with a CTE close to zero are required. Glass-ceramic cooktops like Ceran cooktops need to withstand large temperature gradients and rapid changes in temperature while cooking because only certain parts of the cooktops will be heated while other parts stay close to ambient temperature. In general, due to its brittleness temperature gradients in glass might cause cracks. However, the glass-ceramics used in cooktops consist of multiple different phases, some exhibiting positive and some others exhibiting negative thermal expansion. The expansion of the different phases compensate each other so that there is not much change in volume of the glass-ceramic with temperature and crack formation is avoided.
An everyday life example for the need for materials with tailored thermal expansion are dental fillings. If the fillings tend to expand by an amount different from the teeth, for example when drinking a hot or cold drink, it might cause a toothache. If dental fillings are, however, made of a composite material containing a mixture of materials with positive and negative thermal expansion then the overall expansion could be precisely tailored to that of tooth enamel. | 0 | Theoretical and Fundamental Chemistry |
CRPF in India had tested skunk for possible usage in crowd control situations in India but the tests failed to meet the required standards. Testing the product on crowd consisting of police personnel and general public reportedly failed to convince the local police crowd control units on its effectiveness. The test subjects were found to have tolerated the smell. According to an official associated with the test, Indians possibly had higher threshold to tolerate the stench. | 1 | Applied and Interdisciplinary Chemistry |
Surfactin, like other surfactants, affects the surface tension of liquids in which it is dissolved. It can lower the waters surface tension from 72 mN/m to 27 mN/m at concentrations as low as 20 μM. Surfactin accomplishes this effect by occupying the intermolecular space between water molecules, decreasing the attractive forces between adjacent water molecules, mainly hydrogen bonds, to increase the solutions fluidity. This property makes surfactin and other surfactants useful as detergents and soaps. | 0 | Theoretical and Fundamental Chemistry |
The Owens/Wendt theory (after D. K. Owens and R. C. Wendt) divides the surface energy into two components: surface energy due to dispersive interactions and surface energy due to polar interactions. This theory is derived from the combination of Youngs relation, which relates the contact angle to the surface energies of the solid and liquid and to the interface tension, and Goods equation (after R. J. Good), which relates the interface tension to the polar and dispersive components of the surface energy. The resulting equation is
Note that this equation has the form of y = mx + b, with
As such, the polar and dispersive components of the solid's surface energy are determined by the slope and intercept of the resulting graph. Of course, the problem at this point is that in order to make that graph, knowing the surface energy of the probe liquid is not enough, as it is necessary to know specifically how it breaks down into its polar and dispersive components as well.
To do this, one can simply reverse the procedure by testing the probe liquid against a standard reference solid that is not capable of polar interactions, such as PTFE. If the contact angle of a sessile drop of the probe liquid is measured on a PTFE surface with
the principle equation reduces to
Since the total surface tension of the liquid is already known, this equation determines the dispersive component, and the difference between the total and dispersive components gives the polar component. | 0 | Theoretical and Fundamental Chemistry |
Depending on the field of physics, it may be advantageous to choose one or another extended set of dimensional symbols. In electromagnetism, for example, it may be useful to use dimensions of T, L, M and Q, where Q represents the dimension of electric charge. In thermodynamics, the base set of dimensions is often extended to include a dimension for temperature, Θ. In chemistry, the amount of substance (the number of molecules divided by the Avogadro constant, ≈ ) is also defined as a base dimension, N.
In the interaction of relativistic plasma with strong laser pulses, a dimensionless relativistic similarity parameter, connected with the symmetry properties of the collisionless Vlasov equation, is constructed from the plasma-, electron- and critical-densities in addition to the electromagnetic vector potential. The choice of the dimensions or even the number of dimensions to be used in different fields of physics is to some extent arbitrary, but consistency in use and ease of communications are common and necessary features. | 1 | Applied and Interdisciplinary Chemistry |
In contrast to selenonic and seleninic acids, selenenic acids are unstable with respect to a self-condensation reaction to form the corresponding selenoseleninates or disproportionation into corresponding seleninic acids and diselenides:
:2 RSeOH → RSe(O)SeR + HO
:2 RSeOH → RSeOH + 1/2 RSeSeR
Even the very bulky 2,4,6-tri-tert-butylbenzeneselenenic acid disproportionates readily. A stable selenenic acid was synthesized by burying the SeOH functional group within the cavity of a [[Calixarene|p-tert-butyl[calix[6]arene macrocycle]]]. X-ray crystallographic analysis revealed the Se-O bond length to be 1.763 Å. The Se-O absorbs in the IR spectrum at 680–700 cm. In a stable selenenic acid prepared by oxidizing a highly hindered selenol, BmtSeH, the Se-O bond length was found to be 1.808 Å while the O-Se-C angle was 96.90°. Oxidation of BmtSeOH gave BmtSeOH.
Selenenic acids are believed to be transient intermediates in a number of redox reactions involving organoselenium compounds. One notable example is the syn-elimination of selenoxides. Selenenic acids are also transient intermediates in the reduction of seleninic acids as well as the oxidation of diselenides. The reasoning for postulating selenenic acids as reactive intermediates is based in part on analogy with their more extensively studied sulfenic acid analogs. | 0 | Theoretical and Fundamental Chemistry |
In the Middle Ages the Imperial Free City of Nuremberg, an important trading place in the south of Germany, produced large amounts of nesting weight pieces to various European standards. In the 1540s, the first pharmacopoeia in the modern sense was also printed there. In 1555, a weight standard for the apothecaries pound of 12 ounces was set in Nuremberg. Under the name Nuremberg pharmaceutical weight' () it would become the standard for most of the north-east of Europe. However, some cities kept local copies of the standard.
As of 1800 all German states and cities except Lübeck (which had the Dutch troy standard) followed the Nuremberg standard. It was also the standard for Denmark, Norway, the Russian Empire, and most cantons of Switzerland. Poland and Sweden had their own variants of the standard, which differed from each other by 0.6%.
In 1811, Bavaria legally defined the apothecaries pound as 360.00 g (an ounce of 30.00 g). In 1815, Nuremberg lost its status as a free city and became part of Bavaria. From now on the Nuremberg apothecaries pound was no longer the official apothecaries pound in Nuremberg; but the difference was only 0.6%. In 1836 the Greek apothecaries pound was officially defined by this standard, four years after Otto, the son of the king of Bavaria, became the first king of Greece. But only few German states followed the example of Bavaria, and with a long delay. The apothecaries' pound of 360 g was also adopted in Lübeck, where it was official as of 1861.
Austria and the states of the Habsburg monarchy officially had a different standard since 1761, and Prussia, followed by its neighbours Anhalt, Lippe and Mecklenburg, would diverge in the opposite direction with a reform in 1816. But in both cases apothecaries continued to use the Nuremberg standard unofficially for a long time after it became illegal.
In Russia the apothecaries' system survived well into the 20th century. The Soviet Union officially abolished it only in January 1927. | 1 | Applied and Interdisciplinary Chemistry |
Isopentenyl pyrophosphate (IPP, isopentenyl diphosphate, or IDP) is an isoprenoid precursor. IPP is an intermediate in the classical, HMG-CoA reductase pathway (commonly called the mevalonate pathway) and in the non-mevalonate MEP pathway of isoprenoid precursor biosynthesis. Isoprenoid precursors such as IPP, and its isomer DMAPP, are used by organisms in the biosynthesis of terpenes and terpenoids. | 1 | Applied and Interdisciplinary Chemistry |
The journal is able to be open-access, yet not have page or process charges levied against authors, due to sponsorship from the Education Division of the RSC. The RSC is a charity, as well as a learned society, and support for an open-access educational journal is seen as furthering its educational mission. | 1 | Applied and Interdisciplinary Chemistry |
Butyryl phosphate is an intermediate in the fermentation of butyric acid. The glutamate oxidation of butyryl phosphate may provide the main source of energy for Clostridium tetanomorphum. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, nitrosamines (or more formally N-nitrosamines) are organic compounds with the chemical structure , where R is usually an alkyl group. They feature a nitroso group () bonded to a deprotonated amine. Most nitrosamines are carcinogenic in nonhuman animals. A 2006 systematic review supports a "positive association between nitrite and nitrosamine intake and gastric cancer, between meat and processed meat intake and gastric cancer and oesophageal cancer, and between preserved fish, vegetable and smoked food intake and gastric cancer, but is not conclusive". | 0 | Theoretical and Fundamental Chemistry |
In 1925 in Germany, Walter Noddack, Ida Tacke, and Otto Berg reported that they detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite.
In 1928 they were able to extract 1 gram of the element by processing 660 kg of molybdenite. In 2020 a memorial medal of the discovery was issued by ISTR (art-designer: Igor Petrov). | 1 | Applied and Interdisciplinary Chemistry |
Recombinant subunit vaccines are used in development for tuberculosis, dengue fever, soil-transmitted helminths, feline leukaemia and COVID-19.
Subunit vaccines are not only considered effective for SARS-COV-2, but also as candidates for evolving immunizations against malaria, tetanus, salmonella enterica, and other diseases. | 1 | Applied and Interdisciplinary Chemistry |
Bond forming reactions between carbon and nitrogen are the most widely used in dynamic covalent chemistry. They have been used more broadly in materials chemistry for molecular switches, covalent organic frameworks, and in self-sorting systems.
Imine formation takes place between an aldehyde or ketone and a primary amine. Similarly, aminal formation takes place between an aldehyde or ketone and a vicinal secondary amine. Both reactions are commonly used in DCvC. While both reactions can initially be categorized as formation reactions, in the presence of one or more of either reagent, the dynamic equilibrium between carbonyl and amine becomes an exchange reaction. | 0 | Theoretical and Fundamental Chemistry |
(born July 16, 1943) is a prominent organic chemist and currently a member of the faculty at the University of Chicago and professor of Chubu University. | 0 | Theoretical and Fundamental Chemistry |
The reaction center is in the thylakoid membrane. It transfers absorbed light energy to a dimer of chlorophyll pigment molecules near the periplasmic (or thylakoid lumen) side of the membrane. This dimer is called a special pair because of its fundamental role in photosynthesis. This special pair is slightly different in PSI and PSII reaction centers. In PSII, it absorbs photons with a wavelength of 680 nm, and is therefore called P680. In PSI, it absorbs photons at 700 nm and is called P700. In bacteria, the special pair is called P760, P840, P870, or P960. "P" here means pigment, and the number following it is the wavelength of light absorbed.
Electrons in pigment molecules can exist at specific energy levels. Under normal circumstances, they are at the lowest possible energy level, the ground state. However, absorption of light of the right photon energy can lift them to a higher energy level. Any light that has too little or too much energy cannot be absorbed and is reflected. The electron in the higher energy level is unstable and will quickly return to its normal lower energy level. To do this, it must release the absorbed energy. This can happen in various ways. The extra energy can be converted into molecular motion and lost as heat, or re-emitted by the electron as light (fluorescence). The energy, but not the electron itself, may be passed onto another molecule; this is called resonance energy transfer. If an electron of the special pair in the reaction center becomes excited, it cannot transfer this energy to another pigment using resonance energy transfer. Under normal circumstances, the electron would return to the ground state, but because the reaction center is arranged so that a suitable electron acceptor is nearby, the excited electron is taken up by the acceptor. The loss of the electron gives the special pair a positive charge and, as an ionization process, further boosts its energy. The formation of a positive charge on the special pair and a negative charge on the acceptor is referred to as photoinduced charge separation. The electron can be transferred to another molecule. As the ionized pigment returns to the ground state, it takes up an electron and gives off energy to the oxygen evolving complex so it can split water into electrons, protons, and molecular oxygen (after receiving energy from the pigment four times). Plant pigments usually utilize the last two of these reactions to convert the sun's energy into their own.
This initial charge separation occurs in less than 10 picoseconds (10 seconds). In their high-energy states, the special pigment and the acceptor could undergo charge recombination; that is, the electron on the acceptor could move back to neutralize the positive charge on the special pair. Its return to the special pair would waste a valuable high-energy electron and simply convert the absorbed light energy into heat. In the case of PSII, this backflow of electrons can produce reactive oxygen species leading to photoinhibition. Three factors in the structure of the reaction center work together to suppress charge recombination nearly completely:
* Another electron acceptor is less than 1 nanometer away from the first acceptor, and so the electron is rapidly transferred farther away from the special pair.
* An electron donor is less than 1 nm away from the special pair, and so the positive charge is neutralized by the transfer of another electron.
* The electron transfer back from the electron acceptor to the positively charged special pair is especially slow. The rate of an electron transfer reaction increases with its thermodynamic favorability up to a point and then decreases. The back transfer is so favorable that it takes place in the inverted region where electron-transfer rates become slower.
Thus, electron transfer proceeds efficiently from the first electron acceptor to the next, creating an electron transport chain that ends when it has reached NADPH. | 0 | Theoretical and Fundamental Chemistry |
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