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An antichlor is a substance used to decompose residual hypochlorite or chlorine after chlorine-based bleaching, in order to prevent ongoing reactions with, and therefore damage to, the material that has been bleached. Antichlors include sodium bisulfite, potassium bisulfite, sodium metabisulfite, sodium thiosulfate, and hydrogen peroxide.
In the textile industry, the antichlor is usually added right before the end of the bleaching process. Antichlors are used mainly on fiber, textiles, and paper pulp. Rinsing with water should follow the antichlor treatment in order to flush out by-products of the procedure. For household use, rinsing both before and after use is recommended.
Hydrogen peroxide is by itself a strong bleaching agent and should be used only in diluted form, such as a 3% solution in water. Hypochlorite plus peroxide releases triplet oxygen, which is itself a bleaching agent, but is short-lived in water solution. Reacting large amounts of peroxide can release enough oxygen to create a fire or explosion hazard.
Antichlors are sometimes added to shampoos for treating hair after swimming in chlorinated water. | 0 | Theoretical and Fundamental Chemistry |
A variety of different polymerization methods may be utilized for the synthesis of the polymer chains that make up hydrogels. Their properties depend on how these chains are crosslinked. | 0 | Theoretical and Fundamental Chemistry |
With positive selection, the cells expressing the antigen(s) of interest, which attached to the magnetic column, are washed out to a separate vessel, after removing the column from the magnetic field. This method is useful for isolation of a particular cell type, for instance CD4 lymphocytes.
Moreover, it enables early detection of sperm which initiate apoptosis, although they may show an adequate appearance and motility. A magnetic-labelled receptor that binds to annexin is added to sperm. Inside normal cells, phosphatidylserine molecules are located within the cell membrane towards the cytoplasm. Nevertheless, in those cells that initiate the apoptotic process phosphatidylserine instead faces the cell membrane outer side, binding to the annexin conjugate. Therefore, normal spermatozoa will pass through the column without binding to the labelled receptor.
On the other hand, proapoptotic sperm will remain trapped, which turns out as a sperm selection process thanks to the magnetic- labeled antibody. Finally, this technique has shown its efficacy, even though it remains limited.
With negative selection, the antibody used is against surface antigen(s) which are known to be present on cells that are not of interest. After administration of the cells/magnetic nanoparticles solution onto the column the cells expressing these antigens bind to the column and the fraction that goes through is collected, as it contains almost no cells with these undesired antigens. | 1 | Applied and Interdisciplinary Chemistry |
In 1871, Lord Kelvin (William Thomson) obtained the following relation governing a liquid-vapor interface:
where:
: = vapor pressure at a curved interface of radius
: = vapor pressure at flat interface () =
: = surface tension
: = density of vapor
: = density of liquid
: , = radii of curvature along the principal sections of the curved interface.
In his dissertation of 1885, Robert von Helmholtz (son of the German physicist Hermann von Helmholtz) derived the Ostwald–Freundlich equation and showed that Kelvin's equation could be transformed into the Ostwald–Freundlich equation. The German physical chemist Wilhelm Ostwald derived the equation apparently independently in 1900; however, his derivation contained a minor error which the German chemist Herbert Freundlich corrected in 1909. | 0 | Theoretical and Fundamental Chemistry |
Zwitterionic (ampholytic) surfactants have both cationic and anionic centers attached to the same molecule. The cationic part is based on primary, secondary, or tertiary amines or quaternary ammonium cations. The anionic part can be more variable and include sulfonates, as in the sultaines CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) and cocamidopropyl hydroxysultaine. Betaines such as cocamidopropyl betaine have a carboxylate with the ammonium. The most common biological zwitterionic surfactants have a phosphate anion with an amine or ammonium, such as the phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelins.
Lauryldimethylamine oxide and myristamine oxide are two commonly used zwitterionic surfactants of the tertiary amine oxides structural type. | 0 | Theoretical and Fundamental Chemistry |
As only particles that exhibit non-linear velocity experience the SCODA concentrating force, small charged particles that respond linearly to electrophoretic fields are not concentrated. These particles instead of spiraling towards the center of the SCODA gel orbit at a constant radius. If a weak DC field is superimposed on the SCODA rotating fields these particles will be "washed" off from the SCODA gel resulting in highly pure DNA remaining in the gel center. | 1 | Applied and Interdisciplinary Chemistry |
To date, there have been few examples of hydrogen-bond catalysis in the synthesis of natural products despite the large number of reactions being discovered. Generally, with high required catalyst loading and often extreme substrate specificity, hydrogen-bond catalysis is not yet developed enough to provide useful, general reactions that represent a significant improvement over traditional methods. In the published examples, hydrogen-bond catalysis is mainly used in the beginning stages to quickly access early intermediates with high enantiomeric enrichment.
In the Jacobsen synthesis of (+)-yohimbine, an indole alkaloid, an early enantioselective Pictet-Spengler reaction using a pyrrole-substituted thiourea catalyst produced gram-scale quantities of product in 94% ee and 81% yield. The remainder of the synthesis was short, using a reductive amination and an intramolecular Diels-Alder reaction.
In 2008, Takemoto disclosed a concise synthesis of (−)-epibatidine that relied on a Michael cascade, catalyzed by a bifunctional catalyst. After initial asymmetric Michael addition to the β-nitrostyrene, intramolecular Michael addition furnishes the cyclic ketoester product in 75% ee. Standard functional group manipulations and an intramolecular cyclization yields the natural product. | 0 | Theoretical and Fundamental Chemistry |
Decarboxylative cross coupling reactions are chemical reactions in which a carboxylic acid is reacted with an organic halide to form a new carbon-carbon bond, concomitant with loss of CO. Aryl and alkyl halides participate. Metal catalyst, base, and oxidant are required.
A significant advantage of this reaction is that it uses relatively inexpensive carboxylic acids (or their salts) and is far less air and moisture sensitive in comparison to typical cross-coupling organometallic reagents. Furthermore, the carboxylic acid moiety is a common feature of natural products and can also be prepared by relatively benign air oxidations. Additional benefits include the broad tolerance of functional groups, as well as the capacity to avoid the use of strong bases. An important elementary step in this reaction is protodecarboxylation or metalation to first convert the C–COOH bond to a C–H or C–M bond respectively. | 0 | Theoretical and Fundamental Chemistry |
A bridging ligand links two or more metal centers. Virtually all inorganic solids with simple formulas are coordination polymers, consisting of metal ion centres linked by bridging ligands. This group of materials includes all anhydrous binary metal ion halides and pseudohalides. Bridging ligands also persist in solution. Polyatomic ligands such as carbonate are ambidentate and thus are found to often bind to two or three metals simultaneously. Atoms that bridge metals are sometimes indicated with the prefix "μ". Most inorganic solids are polymers by virtue of the presence of multiple bridging ligands. Bridging ligands, capable of coordinating multiple metal ions, have been attracting considerable interest because of their potential use as building blocks for the fabrication of functional multimetallic assemblies. | 0 | Theoretical and Fundamental Chemistry |
EA-3148 (Substance 100A) is a "V-series" nerve agent related to the better-known compounds VX and VR. It was studied by both the US and Soviet chemical weapons programmes during the Cold War, and is notable as the only V-series organophosphate nerve agent specifically identified in public domain sources as having a higher absolute potency as an acetylcholinesterase inhibitor than VX (around 50% more potent by weight). However, both the US and Soviet investigations of the compound concluded that despite its high potency, the physicochemical properties of the substance made it unsuitable for weaponisation, and further research was not conducted.
The chemical structure of EA-3148 falls within the scope of compounds designated "Toxic chemicals" under Schedule 1 of the Chemical Weapons Convention and so it is illegal throughout the world under international law and may only be used for certain types of scientific and medical research. | 1 | Applied and Interdisciplinary Chemistry |
Thiols react with this compound, cleaving the disulfide bond to give 2-nitro-5-thiobenzoate (TNB), which ionizes to the TNB dianion in water at neutral and alkaline pH. This TNB ion has a yellow color.
This reaction is rapid and stoichiometric, with the addition of one mole of thiol releasing one mole of TNB. The TNB is quantified in a spectrophotometer by measuring the absorbance of visible light at 412 nm, using an extinction coefficient of 14,150 M cm for dilute buffer solutions, and a coefficient of 13,700 M cm for high salt concentrations, such as 6 M guanidinium hydrochloride or 8 M urea. Ellman's original 1959 publication estimated the molar extinction at 13,600 M cm, and this value can be found in some modern applications of the method despite improved determinations. Commercial DTNB may not be completely pure, so may require recrystallization to obtain completely accurate and reproducible results.
Ellman's reagent can be used for measuring low-molecular mass thiols such as glutathione in both pure solutions and biological samples, such as blood. It can also measure the number of thiol groups on proteins. | 1 | Applied and Interdisciplinary Chemistry |
The diaphragm is an important part of the body's digestive system. The muscular diaphragm separates the thoracic cavity from the abdominal cavity where most of the digestive organs are located. The suspensory muscle attaches the ascending duodenum to the diaphragm. This muscle is thought to be of help in the digestive system in that its attachment offers a wider angle to the duodenojejunal flexure for the easier passage of digesting material. The diaphragm also attaches to, and anchors the liver at its bare area. The esophagus enters the abdomen through a hole in the diaphragm at the level of T10. | 1 | Applied and Interdisciplinary Chemistry |
In the negative feedback loops, CK1ε periodically binds to and phosphorylates the PER proteins (PER1, PER2, and PER3), which form heterodimers with each other and interact with CRY1 and CRY2. The effects of phosphorylation are two-fold. It has been shown in Drosophila that phosphorylation of the PER proteins increase their ubiquitination, which leads to degradation. Phosphorylation of the PER proteins also leaves them unable to enter the nucleus, where they suppress transcription of clock genes. The blocking of nuclear translocation occurs via phosphorylation of PER at the nuclear localization signal, which masks the signal and prevents nuclear entry. However, this CK1ε-mediated constraint to the cytoplasm can be overcome when the PER protein complex is bound to CRY. CK1ε has been shown to phosphorylate CRY when both CK1ε and CRY are complexed with PER in vitro, but the functional significance of this remains undetermined.
CK1ε may also have a role in positive feedback; the transcription factor BMAL1 is a CK1ε substrate in vitro, and increased CK1ε activity has been shown to positively regulate transcription of genes under the influence of BMAL1-dependent circadian gene promoters. This has not yet been studied in vivo. | 1 | Applied and Interdisciplinary Chemistry |
*(1901) About the sulfurized dibutolactone, Reports of the German Chemical Society
*(1903), Ueber organische Synthesen mittels Kohlenoxysulfid. Ber. Dtsch. Chem. Ges., 36: 1007–1013. doi:10.1002/cber.190303601208 [https://onlinelibrary.wiley.com/doi/abs/10.1002/cber.190303601208]
*(1905) About reversible photochemical reactions in the homogeneous system
*(1908) About Chemical Light Effects
*(1911), Die chemischen Wirkungen des Lichts (The Chemical Effects of Light)
*(1913) About the activation of oxygen by radiation, Reports of the German Chemical Society
*(1919), A new effect of radiation in photosensitive layers
*(1916), Über Absorptionsspektren und über eine einfache Methode zu ihrer quantitativen Bestimmung. Ber. Dtsch. Chem. Ges., 49: 1496–1532. doi:10.1002/cber.191604901176 [https://onlinelibrary.wiley.com/doi/abs/10.1002/cber.191604901176]
*(1917) About real photochemical processes. Zeitschrift für Physikalische Chemie, Volume 130U, Issue 1, Pages 607–615, ISSN (Online) 2196–7156, ISSN (Print) 0942–9352, doi: 10.1515/zpch-1927-13065.
*(1920), Über die spezifische Wirkung der polarisierten Strahlung. Ann. Phys., 368: 681–725. doi:10.1002/andp.19203682402 [https://onlinelibrary.wiley.com/doi/abs/10.1002/andp.19203682402]
*(1921) Weigert, F. Pflügers Arch. 190: 177. https://doi.org/10.1007/BF01723387 [https://link.springer.com/article/10.1007/BF01723387#citeas]
*(1921) Weigert, F. Z. Physik. Über einen neuen Effekt der Strahlung 5: 410. https://doi.org/10.1007/BF01327678 [https://link.springer.com/article/10.1007%2FBF01327678?LI=true#citeas]
*(1923) On the photochemistry of chlorine. Journal of Physical Chemistry
*(1924) About the polarization state of the resonance radiation and about its influence by weak magnetic fields. Polarisierte Fluoreszenz in Farbstofflösungen Zeitschrift für Physik, Volume 25, Number 1, Page 99-117 [https://link.springer.com/article/10.1007/BF01327512]
*(1927) Optische Methoden der Chemie (Optical Methods of Chemistry)
*(1927) About the mechanism of photochemical polymerization of anthracene. Natural Sciences
*(1929) Photochemical to the theory of color vision. Zeitschrift für Physikalische Chemie, Volume 3B, Issue 1, Pages 377–388, ISSN (Online) 2196–7156, ISSN (Print) 0942–9352, doi: /10.1515/zpch-1929-0328.
*(1929) About monochromatic light filters.
*(1930) Color-ability, a new property of the latent photographic image. Natural Sciences
*(1933) The Colloid Chemistry of Photoanisotrophy
*(1940) Photochemical Studies on Color Vision
*Berenblum and Halban, in: Nature, no. 159 (1947), 733. | 0 | Theoretical and Fundamental Chemistry |
There were three EXPOSE experiments completed between 2008 and 2015: EXPOSE-E, EXPOSE-R and EXPOSE-R2.
The EXPOSE-E was launched on 7 February 2008 on board the Space Shuttle Atlantis and was mounted on the ISS European module Columbus to the European Technology Exposure Facility (EuTEF). EXPOSE-R was launched to the ISS on 26 November 2008 from Baikonur Cosmodrome in Kazakhstan on board of a Progress capsule and was mounted on the ISS Russian module Zevzda. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110 nm and cosmic radiation (trays 1 and 3) or to simulated Martian surface conditions (tray 2). The different experiments consisted in exposing solid molecules, gas mixtures or biological samples to the solar ultraviolet (UV) radiation, cosmic rays, vacuum and temperature fluctuations of outer space as the ISS repeatedly passed between areas of direct sunlight and the cold darkness of Earth's shadow.
At the end of the exposition period, EXPOSE-E was brought back to the ground in September 2009 as part of the Space Shuttle Discovery mission STS-128. EXPOSE-R was brought back in 2011 by a Soyuz spacecraft. From the landing site in Kazakhstan, the trays were returned via Moscow and distributed to scientists for further analysis in their laboratories. EXPOSE-R2 was launched on 24 July 2014, exposure was finished in April 2015, and was returned to Earth in early 2016 where it is still undergoing analyses. | 1 | Applied and Interdisciplinary Chemistry |
There are several common types of nonsynonymous substitutions.
Missense mutations are nonsynonymous substitutions that arise from point mutations, mutations in a single nucleotide that result in the substitution of a different amino acid, resulting in a change to the protein encoded.
Nonsense mutations are nonsynonymous substitutions that arise when a mutation in the DNA sequence causes a protein to terminate prematurely by changing the original amino acid to a stop codon. Another type of mutation that deals with stop codons is known as a nonstop mutation or readthrough mutation, which occurs when a stop codon is exchanged for an amino acid codon, causing the protein to be longer than specified. | 1 | Applied and Interdisciplinary Chemistry |
The Department of Chemistry () is a department under the Faculty of Science, University of Copenhagen. It is the largest basic research institute in chemistry in Denmark, and is responsible for the teaching of chemistry at all levels at the University of Copenhagens Faculty of Science: from undergraduate courses in chemistry to Ph.D.-level courses. Its office is located at the University of Copenhagens North Campus. | 1 | Applied and Interdisciplinary Chemistry |
A virtually imaged phased array (VIPA) is an angular dispersive device that, like a prism or a diffraction grating, splits light into its spectral components. The device works almost independently of polarization. In contrast to prisms or regular diffraction gratings, the VIPA has a much higher angular dispersion but has a smaller free spectral range. This aspect is similar to that of an Echelle grating, since it also uses high diffraction orders. To overcome this disadvantage, the VIPA can be combined with a diffraction grating. The VIPA is a compact spectral disperser with high wavelength resolving power. | 0 | Theoretical and Fundamental Chemistry |
The arginine catabolic mobile element (ACME) is a mobile genetic element of Staphylococcus bacterial species. This genetic element provides for several immune modulating functions, including resistance to polyamines which serve as a non-specific immune response both on intact skin and following the inflammatory response in wound healing. Diverse ACME are present in several species of Staphylococcus, including Staphylococcus epidermidis. | 1 | Applied and Interdisciplinary Chemistry |
The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder). Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body. The process of digestion has three stages: the cephalic phase, the gastric phase, and the intestinal phase.
The first stage, the cephalic phase of digestion, begins with secretions from gastric glands in response to the sight and smell of food. This stage includes the mechanical breakdown of food by chewing, and the chemical breakdown by digestive enzymes, that takes place in the mouth. Saliva contains the digestive enzymes amylase, and lingual lipase, secreted by the salivary and serous glands on the tongue. Chewing, in which the food is mixed with saliva, begins the mechanical process of digestion. This produces a bolus which is swallowed down the esophagus to enter the stomach.
The second stage, the gastric phase, happens in the stomach. Here, the food is further broken down by mixing with gastric acid until it passes into the duodenum, the first part of the small intestine.
The third stage, the intestinal phase, begins in the duodenum. Here, the partially digested food is mixed with a number of enzymes produced by the pancreas.
Digestion is helped by the chewing of food carried out by the muscles of mastication, the tongue, and the teeth, and also by the contractions of peristalsis, and segmentation. Gastric acid, and the production of mucus in the stomach, are essential for the continuation of digestion.
Peristalsis is the rhythmic contraction of muscles that begins in the esophagus and continues along the wall of the stomach and the rest of the gastrointestinal tract. This initially results in the production of chyme which when fully broken down in the small intestine is absorbed as chyle into the lymphatic system. Most of the digestion of food takes place in the small intestine. Water and some minerals are reabsorbed back into the blood in the colon of the large intestine. The waste products of digestion (feces) are defecated from the rectum via the anus. | 1 | Applied and Interdisciplinary Chemistry |
Companion planting in gardening and agriculture is the planting of different crops in proximity for any of a number of different reasons, including weed suppression, pest control, pollination, providing habitat for beneficial insects, maximizing use of space, and to otherwise increase crop productivity. Companion planting is a form of polyculture.
Companion planting is used by farmers and gardeners in both industrialized and developing countries for many reasons. Many of the modern principles of companion planting were present many centuries ago in forest gardens in Asia, and thousands of years ago in Mesoamerica. The technique may allow farmers to reduce costly inputs of artificial fertilisers and pesticides. | 1 | Applied and Interdisciplinary Chemistry |
2DPs as two dimensional sheet macromolecules have a crystal lattice, that is they consist of monomer units that repeat in two dimensions. Therefore, a clear diffraction pattern from their crystal lattice should be observed as a proof of crystallinity. The internal periodicity is supported by electron microscopy imaging, electron diffraction and Raman-spectroscopic analysis.
2DPs should in principle also be obtainable by, e.g., an interfacial approach whereby proving the internal structure, however, is more challenging and has not yet been achieved.
In 2014 a 2DP was reported synthesised from a trifunctional photoreactive anthracene derived monomer, preorganised in a lamellar crystal and photopolymerised in a [4+4]cycloaddition. Another reported 2DP also involved an anthracene-derived monomer | 0 | Theoretical and Fundamental Chemistry |
Accidental or inadvertent poisoning of agricultural workers due to exposure to pesticides is a very serious matter resulting in many deaths and hospitalizations. The effects of pesticides at high concentrations on human health is a thus a matter of much study, resulting in many publications on the toxicology of pesticides. However the maximum residue limits of pesticides in food are low, and are carefully set by the authorities to ensure, to their best judgement, no health impacts.
According to the American Cancer Society there is no evidence that pesticide residues increase the risk of people getting cancer. The ACA advises washing fruit and vegetables before eating to remove both pesticide residue and other undesirable contaminants.
There are many studies on the health differences between consumers of organic foods vs consumers of organically grown foods. When the American Academy of Pediatrics reviewed the literature on organic foods in 2012, they found that "current evidence does not support any meaningful nutritional benefits or deficits from eating organic compared with conventionally grown foods, and there are no well-powered human studies that directly demonstrate health benefits or disease protection as a result of consuming an organic diet." | 1 | Applied and Interdisciplinary Chemistry |
Waste containing unusually low BOD concentrations may fail to sustain the secondary treatment population required for normal waste concentrations. The reduced population surviving the starvation event may be unable to completely utilize available BOD when waste loads return to normal. Dilution may be caused by addition of large volumes of relatively uncontaminated water such as stormwater runoff into a combined sewer. Smaller sewage treatment plants may experience dilution from cooling water discharges, major plumbing leaks, firefighting, or draining large swimming pools.
A similar problem occurs as BOD concentrations drop when low flow increases waste residence time within the secondary treatment bioreactor. Secondary treatment ecosystems of college communities acclimated to waste loading fluctuations from student work/sleep cycles may have difficulty surviving school vacations. Secondary treatment systems accustomed to routine production cycles of industrial facilities may have difficulty surviving industrial plant shutdown. Populations of species feeding on incoming waste initially decline as concentration of those food sources decrease. Population decline continues as ecosystem predator populations compete for a declining population of lower trophic level organisms. | 1 | Applied and Interdisciplinary Chemistry |
Back titration is a titration done in reverse; instead of titrating the original sample, a known excess of standard reagent is added to the solution, and the excess is titrated. A back titration is useful if the endpoint of the reverse titration is easier to identify than the endpoint of the normal titration, as with precipitation reactions. Back titrations are also useful if the reaction between the analyte and the titrant is very slow, or when the analyte is in a non-soluble solid. | 0 | Theoretical and Fundamental Chemistry |
Plastic crystals were discovered in 1938 by J. Timmermans by their anomalously low melting entropy. He found that organic substances having a melting entropy lower than approximately 17 J·K·mol (~2Rg) are having peculiar properties. Timmermans named them .
Michils showed in 1948 that these organic compounds are easily deformed and accordingly named them, plastic crystals (). Perfluorocyclohexane for example is plastic to such a degree that it will start to flow under its own weight. | 0 | Theoretical and Fundamental Chemistry |
Phosphorus-32 is a short-lived high energy beta emitter, which is used in research in radiotracers. It has a half-life of 14 days. It can be used in DNA research. Phosphorus-32 can be made by the neutron irradiation (np reaction) of sulfur-32 or from phosphorus-31 by neutron capture. | 0 | Theoretical and Fundamental Chemistry |
Hydrogen rich substances as ammonia and hydrazine are great for storing hydrogen. This is due to their energy density, for ammonia at least 1.3 times that of liquid hydrogen. Hydrazine is almost twice as dense in energy compared to liquid hydrogen, however a downside is that dilution is required in the use of direct hydrazine fuel cells, which lowers the overall power one can get from this fuel cell. Besides the high volumetric density, ammonia and hydrous hydrazine have a low flammability, which makes it superior to hydrogen by lowering the storage and transportation costs. | 0 | Theoretical and Fundamental Chemistry |
In the eighteenth century, as the field of chemistry was evolving from alchemy, a field of the natural philosophy was created around the idea of air as a reagent. Before this, air was primarily considered a static substance that would not react and simply existed. However, as Lavoisier and several other pneumatic chemists would insist, the air was indeed dynamic, and would not only be influenced by combusted material, but would also influence the properties of different substances.
The initial concern of pneumatic chemistry was combustion reactions, beginning with Stephen Hales. These reactions would give off different "airs" as chemists would call them, and these different airs contained more simple substances. Until Lavoisier, these airs were considered separate entities with different properties; Lavoisier was responsible largely for changing the idea of air as being constituted by these different airs that his contemporaries and earlier chemists had discovered.
This study of gases was brought about by Hales with the invention of the pneumatic trough, an instrument capable of collecting the gas given off by reactions with reproducible results. The term gas was coined by J. B. van Helmont, in the early seventeenth century. This term was derived from the Ancient Greek word χάος, chaos, as a result of his inability to collect properly the substances given off by reactions, as he was the first natural philosopher to make an attempt at carefully studying the third type of matter. However, it was not until Lavoisier performed his research in the eighteenth century that the word was used universally by scientists as a replacement for airs.
Van Helmont (1579 – 1644) is sometimes considered the founder of pneumatic chemistry, as he was the first natural philosopher to take an interest in air as a reagent. Alessandro Volta began investigating pneumatic chemistry in 1776 and argued that there were different types of inflammable air based on experiments on marsh gases. Pneumatic chemists credited with discovering chemical elements include Joseph Priestley, Henry Cavendish, Joseph Black, Daniel Rutherford, and Carl Scheele. Other individuals who investigated gases during this period include Robert Boyle, Stephen Hales, William Brownrigg, Antoine Lavoisier, Joseph Louis Gay-Lussac, and John Dalton. | 1 | Applied and Interdisciplinary Chemistry |
Let be the normal stress in the liquid that points radially outward from the center of the bubble. In spherical coordinates, for a fluid with constant density and constant viscosity,
Therefore at some small portion of the bubble surface, the net force per unit area acting on the lamina is
where is the surface tension. If there is no mass transfer across the boundary, then this force per unit area must be zero, therefore
and so the result from momentum conservation becomes
whereby rearranging and letting gives the Rayleigh–Plesset equation
Using dot notation to represent derivatives with respect to time, the Rayleigh–Plesset equation can be more succinctly written as | 1 | Applied and Interdisciplinary Chemistry |
Deflagration (Lat: de + flagrare, to burn down) is subsonic combustion in which a pre-mixed flame propagates through an explosive or a mixture of fuel and oxidizer. Deflagrations in high and low explosives or fuel–oxidizer mixtures may transition to a detonation depending upon confinement and other factors. Most fires found in daily life are diffusion flames. Deflagrations with flame speeds in the range of 1 m/s differ from detonations which propagate supersonically with detonation velocities in the range of km/s. | 0 | Theoretical and Fundamental Chemistry |
Experimental studies in animals have shown that PDE5 inhibitors may reverse kidney damage independently of their effects on blood pressure through intra-renal mechanisms. In humans, PDE5 inhibitors have also been shown to reduce proteinuria, a marker of kidney damage. However, the successful introduction of SGLT2 inhibitors and endothelin receptor antagonists to the field of renal therapeutics makes the development of PDE5 inhibitors for this purpose unlikely. | 1 | Applied and Interdisciplinary Chemistry |
Metabolic suppression is the regulated and reversible reduction of metabolic rate below basal metabolic rate (called standard metabolic rate in ectothermic animals). This reduces the fishs rate of ATP use, which prolongs its survival time at severely hypoxic sub-P P</sub>s by reducing the rate at which the fishs finite anaerobic fuel stores (glycogen) are used. Metabolic suppression also reduces the accumulation rate of deleterious anaerobic end-products (lactate and protons), which delays their negative impact on the fish.
The mechanisms that fish use to suppress metabolic rate occur at behavioral, physiological and biochemical levels. Behaviorally, metabolic rate can be lowered through reduced locomotion, feeding, courtship, and mating. Physiologically, metabolic rate can be lowered through reduced growth, digestion, gonad development, and ventilation efforts. And biochemically, metabolic rate can be further lowered below standard metabolic rate through reduced gluconeogenesis, protein synthesis and degradation rates, and ion pumping across cellular membranes. Reductions in these processes lower ATP use rates, but it remains unclear whether metabolic suppression is induced through an initial reduction in ATP use or ATP supply.
The prevalence of metabolic suppression use among fish species has not been thoroughly explored. This is partly because the metabolic rates of hypoxia-exposed fish, including suppressed metabolic rates, can only be accurately measured using direct calorimetry, and this technique is seldom used for fish. The few studies that have used calorimetry reveal that some fish species employ metabolic suppression in hypoxia/anoxia (e.g., goldfish, tilapia, European eel) while others do not (e.g. rainbow trout, zebrafish). The species that employ metabolic suppression are more hypoxia-tolerant than the species that do not, which suggests that metabolic suppression enhances hypoxia tolerance. Consistent with this, differences in hypoxia tolerance among isolated threespine stickleback populations appear to result from differences in the use of metabolic suppression, with the more tolerant stickleback using metabolic suppression.
Fish that are capable of hypoxia-induced metabolic suppression reduce their metabolic rates by 30% to 80% relative to standard metabolic rates. Because this is not a complete cessation of metabolic rate, metabolic suppression can only prolong hypoxic survival, not sustain it indefinitely. If the hypoxic exposure lasts sufficiently long, the fish will succumb to a depletion of its glycogen stores and/or the over-accumulation of deleterious anaerobic end-products. Furthermore, the severely limited energetic scope that comes with a metabolically suppressed state means that the fish is unable to complete critical tasks such a predator avoidance and reproduction. Perhaps for these reasons, goldfish prioritize their use of aerobic metabolism in most hypoxic environments, reserving metabolic suppression for the extreme case of anoxia. | 0 | Theoretical and Fundamental Chemistry |
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum. | 0 | Theoretical and Fundamental Chemistry |
Jadwiga Barbara Ostrowska-Czubenko (born 18 January 1949 in Kołobrzeg) is a Polish chemist at the Nicolaus Copernicus University in Toruń. | 0 | Theoretical and Fundamental Chemistry |
FLiNaK salt was researched heavily during the late 1950s by Oak Ridge National Laboratory as potential candidate for a coolant in the molten salt reactor because of its low melting point, its high heat capacity, and its chemical stability at high temperatures. Ultimately, its sister salt, FLiBe, was chosen as the solvent salt for the molten salt reactor due to a more desirable nuclear cross section. FLiNaK still gathers interest as an intermediate coolant for a high-temperature molten salt reactor where it could transfer heat without being in the presence of the fuel. | 0 | Theoretical and Fundamental Chemistry |
*In Final Fantasy: The Spirits Within, soldiers use power backpacks based on bacteria.
*In Subnautica, the player can build a bioreactor that serves the same purpose as a bioelectrochemical reactor. | 1 | Applied and Interdisciplinary Chemistry |
Dimitra Markovitsi is a Greek-French photochemist. She is currently an Emeritus Research Director at the French National Center for Scientific Research (CNRS). She pioneered studies on the electronically excited states of liquid crystals and made significant advances to the understanding of processes triggered in DNA upon absorption of UV radiation. The two facets of her work have been the subject of a recent Marie Skodowska Curie European training network entitled "Light DyNAmics - DNA as a training platform for photodynamic processes in soft materials." | 0 | Theoretical and Fundamental Chemistry |
In theoretical chemistry, the Empirical Valence Bond (EVB) approach is an approximation for calculating free-energies of a chemical reaction in condensed-phase. It was first developed by Israeli chemist Arieh Warshel, and was inspired by the way Marcus theory uses potential surfaces to calculate the probability of electron transfer.
Where most methods for reaction free-energy calculations require at least some part of the modeled system to be treated using quantum mechanics, EVB uses a calibrated Hamiltonian to approximate the potential energy surface of a reaction. For a simple 1-step reaction, that typically means that a reaction is modeled using 2 states. These states are valence bond descriptions of the reactants and products of the reaction. The function that gives the ground energy then becomes:
where and are the valence bond descriptions of the reactant and product state respectively, and is the coupling parameter. The and potentials are usually modeled using force field descriptions and . is a bit trickier as it needs to be parameterized using a reference reaction. This reference reaction can be experimental, typically from a reaction in water or other solvents. Alternatively quantum chemical calculations can be used for calibration. | 0 | Theoretical and Fundamental Chemistry |
For the solvent isotope effects to be measurable, a finite fraction of the solvent must have a different isotopic composition than the rest. Therefore, large amounts of the less common isotopic species must be available, limiting observable solvent isotope effects to isotopic substitutions involving hydrogen. Detectable kinetic isotope effects occur only when solutes exchange hydrogen with the solvent or when there is a specific solute-solvent interaction near the reaction site. Both such phenomena are common for protic solvents, in which the hydrogen is exchangeable, and they may form dipole-dipole interactions or hydrogen bonds with polar molecules. | 0 | Theoretical and Fundamental Chemistry |
During retrodialysis, the microdialysis probe is perfused with an analyte-containing solution and the disappearance of drug from the probe is monitored. The recovery for this method can be computed as the ratio of drug lost during passage (C−C) and drug entering the microdialysis probe (C). In principle, retrodialysis can be performed using either the analyte itself (retrodialysis by drug) or a reference compound (retrodialysis by calibrator) that closely resembles both the physiochemical and the biological properties of the analyte. Despite the fact that retrodialysis by drug cannot be used for endogenous compounds as it requires absence of analyte from the sampling site, this calibration method is most commonly used for exogenous compounds in clinical settings. | 1 | Applied and Interdisciplinary Chemistry |
* environmentally friendly, non-toxic applications
* high durability, especially on masonry products, and lightfast
* mineral paints with high vapor permeability
* acid rain resistance
* antifungal properties
* reduces carbonation of cement-based materials | 0 | Theoretical and Fundamental Chemistry |
AOAC Official Method for detecting the addition of sugar in a fruit juice or in maple syrup. It is the only reliable method to detect addition of C3 sugar (ex: beet sugar). | 0 | Theoretical and Fundamental Chemistry |
The cell has a non-conductive housing. The cathode is composed of thousands of sub-millimeter microspheres (co-polymer beads), with a flash coat of copper and multiple layers of electrolytically deposited thin film (650 Angstrom) nickel and palladium. The beads are submerged in water with a lithium sulfate (LiSO) electrolyte solution. | 0 | Theoretical and Fundamental Chemistry |
One resolution to irreversibility is to say that the constant increase of entropy we observe happens only because of the initial state of our universe. Other possible states of the universe (for example, a universe at heat death equilibrium) would actually result in no increase of entropy. In this view, the apparent T-asymmetry of our universe is a problem in cosmology: why did the universe start with a low entropy? This view, supported by cosmological observations (such as the isotropy of the cosmic microwave background) connects this problem to the question of initial conditions of the universe. | 0 | Theoretical and Fundamental Chemistry |
Substances in the chain-melted state display properties of both a solid and a liquid. The co-author of a study regarding the chain-melted state, Andreas Hermann, stated that if the matter were hypothetically to be handled by a person, it would be like holding a wet sponge that is leaking water, while the sponge itself is actually made of water. Described more formally, the potassium metal developed two internal structures, a chain-like lattice that dissolved, and a stronger Bravais lattice that remained in a solid state. This is a type of host–guest chemistry where, in this case, the host lattice of metal atoms remains solid while some of the material binds weakly and resembles a liquid. | 0 | Theoretical and Fundamental Chemistry |
Mount Polley determines what qualifies as ore and what qualifies as waste using drilling and blasting. Ore is then sorted according to blast ball assays. High value sulfide ore is hauled to a crusher for processing at the on site plant. Chalcopyrite and bornite are the main copper-bearing minerals of value at the Mount Polley mine. | 1 | Applied and Interdisciplinary Chemistry |
Advanced oxidation processes are used to remove some persistent organic pollutants and concentrations remaining after biochemical oxidation. Disinfection by chemical oxidation kills bacteria and microbial pathogens by adding hydroxyl radicals such as ozone, chlorine or hypochlorite to wastewater. These hydroxyl radical then break down complex compounds in the organic pollutants into simple compounds such as water, carbon dioxide, and salts. | 1 | Applied and Interdisciplinary Chemistry |
The first application of the pump–probe technique in biology was in vitro imaging of stimulated emission of a dye-labelled cell. Pump–probe imaging is now widely used for melanin imaging to differentiate between the two main forms of melanin eumelanin (brown/black) and pheomelanin (red/yellow). In melanoma, eumelanin is substantially increased. Therefore, imaging the distribution of eumelanin and pheomelanin can help to distinguish benign lesions and melanoma with high sensitivity | 0 | Theoretical and Fundamental Chemistry |
NMR has now entered the arena of real-time process control and process optimization in oil refineries and petrochemical plants. Two different types of NMR analysis are utilized to provide real time analysis of feeds and products in order to control and optimize unit operations. Time-domain NMR (TD-NMR) spectrometers operating at low field (2–20 MHz for ) yield free induction decay data that can be used to determine absolute hydrogen content values, rheological information, and component composition. These spectrometers are used in mining, polymer production, cosmetics and food manufacturing as well as coal analysis. High resolution FT-NMR spectrometers operating in the 60 MHz range with shielded permanent magnet systems yield high resolution NMR spectra of refinery and petrochemical streams. The variation observed in these spectra with changing physical and chemical properties is modeled using chemometrics to yield predictions on unknown samples. The prediction results are provided to control systems via analogue or digital outputs from the spectrometer. | 0 | Theoretical and Fundamental Chemistry |
When surfactants are present in a liquid, they tend to adsorb in the liquid-air or liquid-liquid interface. Interfacial rheology deals with the response of the adsorbed interfacial layer on the deformation. The response depends on the layer composition, and thus interfacial rheology is relevant in many applications in which adsorbed layer play a crucial role, for example in development surfactants, foams and emulsions. Many biological systems like pulmonary surfactant and meibum are dependent on interfacial viscoelasticity for their functionality. Interfacial rheology has been employed to understand the structure-function relationship of these physiological interfaces, how compositional deviations cause diseases such as infant respiratory distress syndrome or dry eye syndrome, and has helped to develop therapies like artificial pulmonary surfactant replacements and eye drops.
Interfacial rheology enables the study of surfactant kinetics, and the viscoelastic properties of the adsorbed interfacial layer correlate well with emulsion and foam stability. Surfactants and surface active polymers used are for stabilising emulsions and foams in food and cosmetic industries. Proteins are surface active and tend to adsorb at the interface, where they can change conformation and influence the interfacial properties. Natural surfactants like asphaltenes and resins stabilize water-oil emulsions in crude oil applications, and by understanding their behavior the crude oil separation process can be enhanced. Also enhanced oil recovery efficiency can be optimized.
Specialized setups that allow bulk exchange during interfacial rheology measurements are used to investigate the response of adsorbed proteins or surfactants upon changes in pH or salinity. These setups can also be used to mimic more complex conditions like the gastric environment to investigate the in vitro displacement or enzymatic hydrolysis of polymers adsorbed at oil-water interfaces to understand how respective emulsion are digested the stomach.
Interfacial rheology allows the probation of bacteria adsorption and biofilm formation at liquid-air or liquid-liquid interfaces.
In food science, interfacial rheology was used to understand the stability of emulsions like mayonnaise, the stability of espresso foam, the film formed on black tea, or the formation of kombucha biofilms. | 0 | Theoretical and Fundamental Chemistry |
After a talk by Lage-Castellanos at the First Workshop on Complex Matter Physics in Havana (MarchCOMeeting'2012), professor Troy Shinbrot of Rutgers University became interested in the subject. Together with student Theo Siu, Cuban results were confirmed and expanded with new experiments and numerical simulations at Rutgers, which resulted in a joint peer-reviewed paper.
Later on, the phenomenon was confirmed independently by others. Whether dynamical behaviors of the falling water play a role remains as an open question.
Videos of the effect are available on YouTube. | 1 | Applied and Interdisciplinary Chemistry |
In physiology, the primary ions of electrolytes are sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), chloride (Cl), hydrogen phosphate (HPO), and hydrogen carbonate (HCO). The electric charge symbols of plus (+) and minus (−) indicate that the substance is ionic in nature and has an imbalanced distribution of electrons, the result of chemical dissociation. Sodium is the main electrolyte found in extracellular fluid and potassium is the main intracellular electrolyte; both are involved in fluid balance and blood pressure control.
All known multicellular lifeforms require a subtle and complex electrolyte balance between the intracellular and extracellular environments. In particular, the maintenance of precise osmotic gradients of electrolytes is important. Such gradients affect and regulate the hydration of the body as well as blood pH, and are critical for nerve and muscle function. Various mechanisms exist in living species that keep the concentrations of different electrolytes under tight control.
Both muscle tissue and neurons are considered electric tissues of the body. Muscles and neurons are activated by electrolyte activity between the extracellular fluid or interstitial fluid, and intracellular fluid. Electrolytes may enter or leave the cell membrane through specialized protein structures embedded in the plasma membrane called "ion channels". For example, muscle contraction is dependent upon the presence of calcium (Ca), sodium (Na), and potassium (K). Without sufficient levels of these key electrolytes, muscle weakness or severe muscle contractions may occur.
Electrolyte balance is maintained by oral, or in emergencies, intravenous (IV) intake of electrolyte-containing substances, and is regulated by hormones, in general with the kidneys flushing out excess levels. In humans, electrolyte homeostasis is regulated by hormones such as antidiuretic hormones, aldosterone and parathyroid hormones. Serious electrolyte disturbances, such as dehydration and overhydration, may lead to cardiac and neurological complications and, unless they are rapidly resolved, will result in a medical emergency. | 0 | Theoretical and Fundamental Chemistry |
This spectroscopic technique complements another recently developed method of chemical characterisation or fingerprinting, namely micro-thermal analysis (micro-TA). This also uses an “active” SThM probe, which acts as a heater as well as a thermometer, so as to inject evanescent temperature waves into a sample and to allow sub-surface imaging of polymers and other materials. The sub-surface detail detected corresponds to variations in heat capacity or thermal conductivity. Ramping the temperature of the probe, and thus the temperature of the small sample region in contact with it, allows localized thermal analysis and/or thermomechanometry to be performed. | 0 | Theoretical and Fundamental Chemistry |
Bouguer-Lambert law: This law is based on observations made by Pierre Bouguer before 1729. It is often attributed to Johann Heinrich Lambert, who cited Bouguers (Claude Jombert, Paris, 1729) – and even quoted from it – in his Photometria' in 1760. Lambert expressed the law, which states that the loss of light intensity when it propagates in a medium is directly proportional to intensity and path length, in the mathematical form used today.
Lambert began by assuming that the intensity of light traveling into an absorbing body would be given by the differential equation: which is compatible with Bouguer's observations. The constant of proportionality was often termed the "optical density" of the body. Integrating to find the intensity at a distance into the body, one obtains: For a homogeneous medium, this reduces to: from which follows the exponential attenuation law:
Beers law: Much later, in 1852, the German scientist August Beer studied another attenuation relation. In the introduction to his classic paper, he wrote: "The absorption of light during the irradiation of a colored substance has often been the object of experiment; but attention has always been directed to the relative diminution of the various colors or, in the case of crystalline bodies, the relation between the absorption and the direction of polarization. Concerning the absolute magnitude of the absorption that a particular ray of light suffers during its propagation through an absorbing medium, there is no information available." By studying absorption of red light in colored aqueous solutions of various salts, he concluded that "the transmittance of a concentrated solution can be derived from a measurement of the transmittance of a dilute solution". It is clear that he understood the exponential relationship, as he wrote: "If is the coefficient (fraction) of diminution, then this coefficient (fraction) will have the value for double this thickness." Furthermore Beer stated: "We shall take the absorption coefficient to be the coefficient giving the diminution in amplitude suffered by a light ray as it passes through a unit length of an absorbing material. We then have, according to theory, and as I have found verified by experiment, where is the absorption coefficient and D the length of the absorbing material traversed in the experiment." This is the relationship that might properly be called Beers law. There is no evidence that Beer saw concentration and path length as symmetrical variables in an equation in the manner of the Beer-Lambert law.
Beer-Lambert law: The modern formulation of the Beer–Lambert law combines the observations of Bouguer and Beer into the mathematical form of Lambert. It correlates the absorbance, most often expressed as the negative decadic logarithm of the transmittance, to both the concentrations of the attenuating species and the thickness of the material sample. An early, possibly the first, modern formulation was given by Robert Luther and Andreas Nikolopulos in 1913. | 0 | Theoretical and Fundamental Chemistry |
Despite the widespread interest in organocatalysis and the large number of new catalytic systems that are continuously being discovered, progress in the understanding of mechanism and catalyst design in the field of hydrogen-bond catalysis is extremely limited. Compared to a more developed field like palladium-catalyzed coupling reactions, hydrogen-bond catalysis presents many challenges that have not yet been successfully tackled.
*Turnover: While palladium-catalyzed reactions can often be effective with catalyst loading of less than 0.1 mol%, hydrogen-bond catalysts are often added in more than 10 mol%. Poor rate acceleration is a general trend that will have to be overcome in order for hydrogen-bond catalysis to be a practical synthetic strategy.
*Mechanism: In the future, further investigation of the precise steps involved in the mechanism of hydrogen-bond catalysis will be required that will enable chemists to rationally design catalytic strategies for more complex or more useful transformations. For comparison, the basic steps of palladium-catalyzed cross coupling have been systematically and thoroughly studied over the last few decades and have led to dramatic advances in catalytic scope, control and reaction design principles. For example, improved understanding of oxidative addition has led to aryl chlorides becoming practical coupling partners, while improved understanding of reductive elimination has led to the development of new reactions involving sp centers. Knowing these fundamental catalytic steps, the ability to rationally plan new reactions and cascades has been extremely useful in the field of total synthesis. In contrast, we lack a general, systematic mechanistic understanding of the steps of hydrogen-bond catalysis and how to influence them. Detailed mechanistic studies have so far been limited to individual systems, and their findings have not been of demonstrable predictive use.
*Catalyst: A related challenge is the investigation of how changes in catalyst, structural, conformational, and electronic can be used to rationally influence the reaction. The goal would be to fully understand how to use multiple co-operative interactions to best accelerate a reaction and impart selectivity. Ideally, rational catalyst design will eventually replace screening of families of catalysts and the choice of building blocks will become more systematic.
*Scope: While new reactions are constantly being discovered, most reactions have extremely narrow substrate scope and the reason for such narrow scope is often not understood. In the field of palladium catalysis, after the foundations of mechanistic understanding were established, the scope of reactions saw rapid growth. Knowing the factors that affected each step of catalysis allowed for the chemists to envision and pursue new reactions of high synthetic utility, such as C-H bond activation reactions. In the field hydrogen-bond catalysis, chemists have not yet reached a stage where new types of reactivity can be easily and systematically targeted. At this point, reaction discovery is useful, but more detailed mechanistic study is required to realize the full potential of hydrogen-bond catalysis. | 0 | Theoretical and Fundamental Chemistry |
Viruses can be present in humans due to direct infection or co-infections which makes diagnosis difficult using classical techniques and can result in an incorrect prognosis and treatment. The use of qPCR allows both the quantification and genotyping (characterization of the strain, carried out using melting curves) of a virus such as the hepatitis B virus. The degree of infection, quantified as the copies of the viral genome per unit of the patient's tissue, is relevant in many cases; for example, the probability that the type 1 herpes simplex virus reactivates is related to the number of infected neurons in the ganglia. This quantification is carried out either with reverse transcription or without it, as occurs if the virus becomes integrated in the human genome at any point in its cycle, such as happens in the case of HPV (human papillomavirus), where some of its variants are associated with the appearance of cervical cancer. Real-time PCR has also brought the quantization of human cytomegalovirus (CMV) which is seen in patients who are immunosuppressed following solid organ or bone marrow transplantation. | 1 | Applied and Interdisciplinary Chemistry |
It is also helpful in diagnosing:
* Fungal infections. Some forms of tinea, such as Trichophyton tonsurans, do not fluoresce.
* Bacterial infections
**Corynebacterium minutissimum is coral red
**Pseudomonas is yellow-green
* Cutibacterium acnes, a bacterium involved in acne causation, exhibits an orange glow under a Wood's lamp. | 0 | Theoretical and Fundamental Chemistry |
Iterons have an important role in plasmid replication. An iteron-containing plasmid origin of replication can be found containing about five iterons about 20 base pairs in length total. These iterons provide a saturation site for initiator receptor proteins and promote replication thus increasing plasmid copy number in a given cell. | 1 | Applied and Interdisciplinary Chemistry |
An example of artificial ratchets is the work by Serreli et al. (2007). Serreli et al. constructed a nanomachine, a rotaxane, that consists of a ring-shaped molecule, that moves along a tiny molecular axle between two different equal compartments, A and B. The normal, random movement of molecules sends the ring back and forth. Since the rings move freely, half of the rotaxanes have the ring on site B and the other half on site A. But the system used by Serreli et al. has a chemical gate on the rotaxane molecule and the axle contains two sticky parts, one at either side of the gate. This gate opens when the ring is close by. The sticky part in B is close to the gate and the rings pass more readily to A than from A to B. They obtained a deviation from equilibrium of 70:50 for A and B respectively, a bit like the demon of Maxwell. But this system works only when light is shone on it and thus needs external energy, just like molecular demons. | 0 | Theoretical and Fundamental Chemistry |
The D-gun atomises the powder feedstock into extremely small particles (80–95% of particles by total number are of size <100 nm). This means proper extraction facilities are required for inhalation safety purposes. Also isolation of the D-gun is recommended to avoid operators breathing in the dangerous dust and fumes. If operators are to enter the room they should wear appropriate dust masks or respirators. Many of the compounds used as the feedstock in detonation spraying are detrimental to human health if ingested or inhaled. Airborne metals from the detonation gun in particular are harmful to the lungs. Exposure to cadmium for example can cause harm to the kidneys and lungs, vomiting, loss of consciousness and even reduced fertility. Also heavy metals have been shown in recent studies to be carcinogenic such as lead, nickel, chromium, and cadmium. Some serious lung conditions caused by metal dust inhalation include:
* Silicosis - a lung disease cause by inhaling silica present in the feedstock compounds.
* Siderosis - (silver polishers lung or welders lung), a lung disease cause by inhaling iron present in the feedstock compounds.
* Alzheimer's - a memory loss disease more common among the elderly has been shown by some studies to be caused by high levels of exposure to aluminum (among many other causes). However, it must be noted that these studies were not conclusive, and others have proven otherwise.
* Metal fume fever - this can occur in some individuals following exposure certain metal compounds (such as copper, zinc, magnesium and aluminum alloys or oxides) that have a particularly unpleasant odour. The fumes are caused as a byproduct when the metals are heated and can trigger a fever-like reaction that may need medical attention. | 1 | Applied and Interdisciplinary Chemistry |
The first measurements of photoinhibition were published in 1956 by Bessel Kok. Even in the very first studies, it was obvious that plants have a repair mechanism that continuously repairs photoinhibitory damage. In 1966, Jones and Kok measured the action spectrum of photoinhibition and found that ultraviolet light is highly photoinhibitory. The visible-light part of the action spectrum was found to have a peak in the red-light region, suggesting that chlorophylls act as photoreceptors of photoinhibition. In the 1980s, photoinhibition became a popular topic in photosynthesis research, and the concept of a damaging reaction counteracted by a repair process was re-invented. Research was stimulated by a paper by Kyle, Ohad and Arntzen in 1984, showing that photoinhibition is accompanied by selective loss of a 32-kDa protein, later identified as the PSII reaction center protein D1. The photosensitivity of PSII from which the oxygen evolving complex had been inactivated with chemical treatment was studied in the 1980s and early 1990s. A paper by Imre Vass and colleagues in 1992 described the acceptor-side mechanism of photoinhibition. Measurements of production of singlet oxygen by photoinhibited PSII provided further evidence for an acceptor-side-type mechanism. The concept of a repair cycle that continuously repairs photoinhibitory damage, evolved and was reviewed by Aro et al. in 1993. Many details of the repair cycle, including the finding that the FtsH protease plays an important role in the degradation of the D1 protein, have been discovered since. In 1996, a paper by Tyystjärvi and Aro showed that the rate constant of photoinhibition is directly proportional to light intensity, a result that opposed the former assumption that photoinhibition is caused by the fraction of light energy that exceeds the maximum capability of photosynthesis. The following year, laser pulse photoinhibition experiments done by Itzhak Ohad's group led to the suggestion that charge recombination reactions may be damaging because they can lead to production of singlet oxygen. The molecular mechanism(s) of photoinhibition are constantly under discussion. The newest candidate is the manganese mechanism suggested 2005 by the group of Esa Tyystjärvi. A similar mechanism was suggested by the group of Norio Murata, also in 2005. | 0 | Theoretical and Fundamental Chemistry |
AMPP offers individual training and certification programs. Many are merged programs that originated as competing programs under the former NACE and SSPC organizations. Other programs are still being administered under the legacy NACE or SSPC frameworks until the merger is complete. | 1 | Applied and Interdisciplinary Chemistry |
Kelvin probe force microscopy (KPFM), also known as surface potential microscopy, is a noncontact variant of atomic force microscopy (AFM). By raster scanning in the x,y plane the work function of the sample can be locally mapped for correlation with sample features. When there is little or no magnification, this approach can be described as using a scanning Kelvin probe (SKP). These techniques are predominantly used to measure corrosion and coatings.
With KPFM, the work function of surfaces can be observed at atomic or molecular scales. The work function relates to many surface phenomena, including catalytic activity, reconstruction of surfaces, doping and band-bending of semiconductors, charge trapping in dielectrics and corrosion. The map of the work function produced by KPFM gives information about the composition and electronic state of the local structures on the surface of a solid. | 0 | Theoretical and Fundamental Chemistry |
* A straightforward method for reversible immobilization, involving the enzymes being adsorbed or attached physically onto a support substance. Adsorption can take place through weak non-specific forces, such as van der waals, hydrogen bonds, and hydrophobic interactions, whereas in ionic bonding the enzymes are bound through salt linkages.
* Adsorption on glass, alginate beads or matrix: Enzyme is attached to the outside of an inert material. In general, this method is the slowest among those listed here. As adsorption is not a chemical reaction, the active site of the immobilized enzyme may be blocked by the matrix or bead, greatly reducing the activity of the enzyme. | 0 | Theoretical and Fundamental Chemistry |
Five states are located along about of Caspian coastline. The length of the coastline of these countries:
# Kazakhstan -
# Turkmenistan -
# Azerbaijan -
# Russia -
# Iran - | 1 | Applied and Interdisciplinary Chemistry |
The tendency of a given chemical species to partition itself
preferentially between liquid and vapor phases is the Henry's law constant. There can be VLE data for mixtures of four or more components, but such a boiling-point diagram is hard to show in either tabular or graphical form. For such multi-component mixtures, as well as binary
mixtures, the vapor–liquid equilibrium data are represented in terms of values (vapor–liquid distribution ratios) defined by
where and are the mole fractions of component in the phases and respectively.
For Raoult's law
For modified Raoult's law
where is the activity coefficient, is the partial pressure and is the pressure.
The values of the ratio are correlated empirically or theoretically in terms of temperature, pressure and phase compositions in the form of equations, tables or graph such as the DePriester charts.
For binary mixtures, the ratio of the values for the two components is called the relative volatility denoted by
which is a measure of the relative ease or difficulty of separating the two components. Large-scale industrial distillation is rarely undertaken if the relative volatility is less than 1.05 with the volatile component being and the less volatile component being .
values are widely used in the design calculations of continuous distillation columns for distilling multicomponent mixtures. | 0 | Theoretical and Fundamental Chemistry |
Although the origin and function of homing endonucleases is still being researched, the most established hypothesis considers them as selfish genetic elements, similar to transposons, because they facilitate the perpetuation of the genetic elements that encode them independent of providing a functional attribute to the host organism.
Homing endonuclease recognition sequences are long enough to occur randomly only with a very low probability (approximately once every ), and are normally found in one or very few instances per genome. Generally, owing to the homing mechanism, the gene encoding the endonuclease (the HEG, "homing endonuclease gene") is located within the recognition sequence which the enzyme cuts, thus interrupting the homing endonuclease recognition sequence and limiting DNA cutting only to sites that do not (yet) carry the HEG.
Prior to transmission, one allele carries the gene (HEG) while the other does not (HEG), and is therefore susceptible to being cut by the enzyme. Once the enzyme is synthesized, it breaks the chromosome in the HEG allele, initiating a response from the cellular DNA repair system. The damage is repaired using recombination, taking the pattern of the opposite, undamaged DNA allele, HEG, that contains the gene for the endonuclease. Thus, the gene is copied to the allele that initially did not have it and it is propagated through successive generations. This process is called "homing". | 1 | Applied and Interdisciplinary Chemistry |
Milk oligosaccharides seem to be more abundant in humans than in other animals and to be more complex and varied. Oligosaccharides in primate milk are generally more complex and diverse than in non-primates.
Human milk oligosaccharides (HMOs) form the third most abundant solid component (dissolved or emulsified or suspended in water) of human milk, after lactose and fat. HMOs are present in a concentration of 11.3 – 17.7 g/L (1.5 oz/gal – 2.36 oz/gal) in human milk, depending on lactation stages. Approximately 200 structurally different human milk oligosaccharides are known, and they can be categorized into fucosylated, sialylated and neutral core HMOs. The composition of human milk oligosaccharides in breast milk is individual to each mother and varies over the period of lactation. The dominant oligosaccharide in 80% of all women is 2′-fucosyllactose, which is present in human breast milk at a concentration of approximately 2.5 g/L; other abundant oligosacchadies include lacto-N-tetraose, lacto-N-neotetraose, and lacto-N-fucopentaose. It has been found by numerous studies that the concentration of each individual human milk oligosaccharide changes throughout the different periods of lactation (colostrum, transitional, mature and late milk) and depend on various factors such as the mother's genetic secretor status and length of gestation. | 0 | Theoretical and Fundamental Chemistry |
Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms a hexahydrate with the formula , containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour.
The anhydrous form is important commercially. It has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium, but large amounts are also used in other areas of the chemical industry. The compound is often cited as a Lewis acid. It is an example of an inorganic compound that reversibly changes from a polymer to a monomer at mild temperature. | 0 | Theoretical and Fundamental Chemistry |
Self-healing hydrogels are a specialized type of polymer hydrogel. A hydrogel is a macromolecular polymer gel constructed of a network of crosslinked polymer chains. Hydrogels are synthesized from hydrophilic monomers by either chain or step growth, along with a functional crosslinker to promote network formation. A net-like structure along with void imperfections enhance the hydrogel's ability to absorb large amounts of water via hydrogen bonding. As a result, hydrogels, self-healing alike, develop characteristic firm yet elastic mechanical properties. Self-healing refers to the spontaneous formation of new bonds when old bonds are broken within a material. The structure of the hydrogel along with electrostatic attraction forces drive new bond formation through reconstructive covalent dangling side chain or non-covalent hydrogen bonding. These flesh-like properties have motivated the research and development of self-healing hydrogels in fields such as reconstructive tissue engineering as scaffolding, as well as use in passive and preventive applications. | 0 | Theoretical and Fundamental Chemistry |
In most vertebrates, digestion is a multistage process in the digestive system, starting from ingestion of raw materials, most often other organisms. Ingestion usually involves some type of mechanical and chemical processing. Digestion is separated into four steps:
# Ingestion: placing food into the mouth (entry of food in the digestive system),
# Mechanical and chemical breakdown: mastication and the mixing of the resulting bolus with water, acids, bile and enzymes in the stomach and intestine to break down complex chemical species into simple structures,
# Absorption: of nutrients from the digestive system to the circulatory and lymphatic capillaries through osmosis, active transport, and diffusion, and
# Egestion (Excretion): Removal of undigested materials from the digestive tract through defecation.
Underlying the process is muscle movement throughout the system through swallowing and peristalsis. Each step in digestion requires energy, and thus imposes an "overhead charge" on the energy made available from absorbed substances. Differences in that overhead cost are important influences on lifestyle, behavior, and even physical structures. Examples may be seen in humans, who differ considerably from other hominids (lack of hair, smaller jaws and musculature, different dentition, length of intestines, cooking, etc.).
The major part of digestion takes place in the small intestine. The large intestine primarily serves as a site for fermentation of indigestible matter by gut bacteria and for resorption of water from digests before excretion.
In mammals, preparation for digestion begins with the cephalic phase in which saliva is produced in the mouth and digestive enzymes are produced in the stomach. Mechanical and chemical digestion begin in the mouth where food is chewed, and mixed with saliva to begin enzymatic processing of starches. The stomach continues to break food down mechanically and chemically through churning and mixing with both acids and enzymes. Absorption occurs in the stomach and gastrointestinal tract, and the process finishes with defecation. | 1 | Applied and Interdisciplinary Chemistry |
In ion exchange chromatography, the Gibbs–Donnan effect is observed when the pH of the applied buffer and the ion exchanger differ, even up to one pH unit. For example, in anion-exchange columns, the ion exchangers repeal protons so the pH of the buffer near the column differs is higher than the rest of the solvent. As a result, an experimenter has to be careful that the protein(s) of interest is stable and properly charged in the "actual" pH.
This effect comes as a result of two similarly charged particles, one from the resin and one from the solution, failing to distribute properly between the two sides; there is a selective uptake of one ion over another. For example, in a sulphonated polystyrene resin, a cation exchange resin, the chlorine ion of a hydrochloric acid buffer should equilibrate into the resin. However, since the concentration of the sulphonic acid in the resin is high, the hydrogen of HCl has no tendency to enter the column. This, combined with the need of electroneutrality, leads to a minimum amount of hydrogen and chlorine entering the resin. | 0 | Theoretical and Fundamental Chemistry |
Reductive stress (RS) is defined as an abnormal accumulation of reducing equivalents despite being in the presence of intact oxidation and reduction systems. A redox reaction involves the transfer of electrons from reducing agents (reductants) to oxidizing agents (oxidants) and redox couples are accountable for the majority of the cellular electron flow. RS is a state where there are more reducing equivalents compared to reductive oxygen species (ROS) in the form of known biological redox couples such as GSH/GSSG, NADP+/NADPH, and NAD+/NADH. Reductive stress is the counterpart to oxidative stress, where electron acceptors are expected to be mostly reduced. Reductive stress is likely derived from intrinsic signals that allow for the cellular defense against pro-oxidative conditions. There is a feedback regulation balance between reductive and oxidative stress where chronic RS induce oxidative species (OS), resulting in an increase in production of RS, again. | 1 | Applied and Interdisciplinary Chemistry |
p75NTR serves as a regulator for actin assembly. Ras homolog family member A (RhoA) causes the actin cytoskeleton to become rigid which limits growth cone mobility and inhibits neuronal elongation in the developing nervous system. p75NTR without a ligand bound activates RhoA and limits actin assembly, but neurotrophin binding to p75NTR can inactivate RhoA and promote actin assembly. p75NTR associates with the Rho GDP dissociation inhibitor (RhoGDI), and RhoGDI associates with RhoA. Interactions with Nogo can strengthen the association between p75NTR and RhoGDI. Neurotrophin binding to p75NTR inhibits the association of RhoGDI and p75NTR, thereby suppressing RhoA release and promoting growth cone elongation (inhibiting RhoA actin suppression). | 1 | Applied and Interdisciplinary Chemistry |
After World War II, with the IG Farben conglomerate dismantled because of its central role in the Nazi regime, Sterling Products bought half of Bayer Ltd, the British Bayer subsidiary—the other half of which it already owned. However, Bayer Aspirin made up only a small fraction of the British aspirin market because of competition from Aspro, Disprin (a soluble aspirin drug) and other brands. Bayer Ltd began searching for new pain relievers to compete more effectively. After several moderately successful compound drugs that mainly utilized aspirin (Anadin and Excedrin), Bayer Ltds manager Laurie Spalton ordered an investigation of a substance that scientists at Yale had, in 1946, found to be the metabolically active derivative of acetanilide: acetaminophen. After clinical trials, Bayer Ltd brought acetaminophen to market as Panadol' in 1956.
However, Sterling Products did not market Panadol in the United States or other countries where Bayer Aspirin still dominated the aspirin market. Other firms began selling acetaminophen drugs, most significantly, McNeil Laboratories with liquid Tylenol in 1955, and Tylenol pills in 1958. By 1967, Tylenol was available without a prescription. Because it did not cause gastric irritation, acetaminophen rapidly displaced much of aspirins sales. Another analgesic, anti-inflammatory drug was introduced in 1962: ibuprofen (sold as Brufen in the U.K. and Motrin' in the U.S.). By the 1970s, aspirin had a relatively small portion of the pain reliever market, and in the 1980s sales decreased even more when ibuprofen became available without prescription.
Also in the early 1980s, several studies suggested a link between childrens consumption of aspirin and Reyes syndrome, a potentially fatal disease. By 1986, the U.S. Food and Drug Administration required warning labels on all aspirin, further suppressing sales. The makers of Tylenol also filed a lawsuit against Anacin aspirin maker American Home Products, claiming that the failure to add warning labels before 1986 had unfairly held back Tylenol sales, though this suit was eventually dismissed. | 1 | Applied and Interdisciplinary Chemistry |
The relatively small number of atomic absorption lines (compared to atomic emission lines) and their narrow width (a few pm) make spectral overlap rare; there are only few examples known that an absorption line from one element will overlap with another. Molecular absorption, in contrast, is much broader, so that it is more likely that some molecular absorption band will overlap with an atomic line. This kind of absorption might be caused by un-dissociated molecules of concomitant elements of the sample or by flame gases. We have to distinguish between the spectra of di-atomic molecules, which exhibit a pronounced fine structure, and those of larger (usually tri-atomic) molecules that don't show such fine structure. Another source of background absorption, particularly in ET AAS, is scattering of the primary radiation at particles that are generated in the atomization stage, when the matrix could not be removed sufficiently in the pyrolysis stage.
All these phenomena, molecular absorption and radiation scattering, can result in artificially high absorption and an improperly high (erroneous) calculation for the concentration or mass of the analyte in the sample. There are several techniques available to correct for background absorption, and they are significantly different for LS AAS and HR-CS AAS. | 0 | Theoretical and Fundamental Chemistry |
Homologous desensitization occurs when a receptor decreases its response to an agonist at high concentration. It is a process through which, after prolonged agonist exposure, the receptor is uncoupled from its signaling cascade and thus the cellular effect of receptor activation is attenuated.
Homologous desensitization is distinguished from heterologous desensitization, a process in which repeated stimulation of a receptor by an agonist results in desensitization of the stimulated receptor as well as other, usually inactive, receptors on the same cell. They are sometimes denoted as agonist-dependent and agonist-independent desensitization respectively. While heterologous desensitization occurs rapidly at low agonist concentrations, homologous desensitization shows a dose dependent response and usually begins at significantly higher concentrations.
Homologous desensitization serves as a mechanism for tachyphylaxis and helps organisms to maintain homeostasis. The process of homologous desensitization has been extensively studied utilizing G protein–coupled receptors (GPCRs). While the different mechanisms for desensitization are still being characterized, there are currently four known mechanisms: uncoupling of receptors from associated G proteins, endocytosis, degradation, and downregulation. The degradation and downregulation of receptors is often also associated with drug tolerance since it has a longer onset, from hours to days. It has been shown that these mechanisms can happen independently of one another, but that they also influence one another. In addition, the same receptor expressed in different cell types can be desensitized by different mechanisms. | 1 | Applied and Interdisciplinary Chemistry |
ANAs are found in many disorders, as well as some healthy individuals. These disorders include: systemic lupus erythematosus (SLE), rheumatoid arthritis, Sjögren syndrome, scleroderma, polymyositis, dermatomyositis, primary biliary cirrhosis, drug induced lupus, autoimmune hepatitis, multiple sclerosis, discoid lupus, thyroid disease, antiphospholipid syndrome, juvenile idiopathic arthritis, psoriatic arthritis, juvenile dermatomyositis, idiopathic thrombocytopaenic purpura, infection and cancer. These antibodies can be subdivided according to their specificity, and each subset has different propensities for specific disorders. | 1 | Applied and Interdisciplinary Chemistry |
Turning is a metal cutting process for producing a cylindrical surface with a single point tool. The workpiece is rotated on a spindle and the cutting tool is fed into it radially, axially or both. Producing surfaces perpendicular to the workpiece axis is called facing. Producing surfaces using both radial and axial feeds is called profiling.
A lathe is a machine tool which spins a block or cylinder of material so that when abrasive, cutting, or deformation tools are applied to the workpiece, it can be shaped to produce an object which has rotational symmetry about an axis of rotation. Examples of objects that can be produced on a lathe include candlestick holders, crankshafts, camshafts, and bearing mounts.
Lathes have four main components: the bed, the headstock, the carriage, and the tailstock. The bed is a precise & very strong base which all of the other components rest upon for alignment. The headstock's spindle secures the workpiece with a chuck, whose jaws (usually three or four) are tightened around the piece. The spindle rotates at high speed, providing the energy to cut the material. While historically lathes were powered by belts from a line shaft, modern examples uses electric motors. The workpiece extends out of the spindle along the axis of rotation above the flat bed. The carriage is a platform that can be moved, precisely and independently parallel and perpendicular to the axis of rotation. A hardened cutting tool is held at the desired height (usually the middle of the workpiece) by the toolpost. The carriage is then moved around the rotating workpiece, and the cutting tool gradually removes material from the workpiece. The tailstock can be slid along the axis of rotation and then locked in place as necessary. It may hold centers to further secure the workpiece, or cutting tools driven into the end of the workpiece.
Other operations that can be performed with a single point tool on a lathe are:
Chamfering: Cutting an angle on the corner of a cylinder.<br />
Parting: The tool is fed radially into the workpiece to cut off the end of a part.<br />
Threading: A tool is fed along and across the outside or inside surface of rotating parts to produce external or internal threads.<br />
Boring: A single-point tool is fed linearly and parallel to the axis of rotation to create a round hole.<br />
Drilling: Feeding the drill into the workpiece axially.<br />
Knurling: Uses a tool to produce a rough surface texture on the work piece. Frequently used to allow grip by hand on a metal part.
Modern computer numerical control (CNC) lathes and (CNC) machining centres can do secondary operations like milling by using driven tools. When driven tools are used the work piece stops rotating and the driven tool executes the machining operation with a rotating cutting tool. The CNC machines use x, y, and z coordinates in order to control the turning tools and produce the product. Most modern day CNC lathes are able to produce most turned objects in 3D.
Nearly all types of metal can be turned, although more time & specialist cutting tools are needed for harder workpieces. | 1 | Applied and Interdisciplinary Chemistry |
Mouse Genome Informatics (MGI) is a free, online database and bioinformatics resource hosted by The Jackson Laboratory, with funding by the National Human Genome Research Institute (NHGRI), the National Cancer Institute (NCI), and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). MGI provides access to data on the genetics, genomics and biology of the laboratory mouse to facilitate the study of human health and disease. The database integrates multiple projects, with the two largest contributions coming from the Mouse Genome Database and Mouse Gene Expression Database (GXD). , MGI contains data curated from over 230,000 publications.
The MGI resource was first published online in 1994 and is a collection of data, tools, and analyses created and tailored for use in the laboratory mouse, a widely used model organism. It is "the authoritative source of official names for mouse genes, alleles, and strains", which follow the guidelines established by the International Committee on Standardized Genetic Nomenclature for Mice. The history and focus of Jackson Laboratory research and production facilities generates tremendous knowledge and depth which researchers can mine to advance their research. A dedicated community of mouse researchers, worldwide enhances and contributes to the knowledge as well. This is an indispensable tool for any researcher using the mouse as a model organism for their research, and for researchers interested in genes that share homology with the mouse genes. Various mouse research support resources including animal collections and free colony management software are also available at the MGI site. | 1 | Applied and Interdisciplinary Chemistry |
A photocatalyst activity indicator ink quickly and easily identifies the presence of an underlying heterogeneous photocatalyst and provides a measure of its activity. A heterogeneous photocatalyst is a material that uses absorbed light energy (usually UV) to drive desired reactions that would not otherwise proceed under ambient conditions. Commercial photocatalytic products, which include: architectural glass, ceramic tiles, roof tiles, cement, paint, and fabrics are marketed on their ability to clean their own surfaces (i.e. are self-cleaning) and the ambient air. Paiis address the industry need for a rapid, simple, inexpensive method to demonstrate and assess the activities of the usually thin, invisible to the eye, photocatalytic coatings present on self-cleaning products. A paii, coated onto the surface of a photocatalyst material under test, works via a photoreductive mechanism, in which light absorbed by the photocatalyst drives the reduction of the dye in the paii, thereby producing a striking color change, which can be measured through the use of a simple mobile phone camera + app, in lieu of any sophisticated analytical equipment. Uses of paiis include: (i) laboratory, factory and on-site commercial photocatalyst product quality control (ii) marketing, for the rapid and striking demonstration of the efficacy of the usually invisible and otherwise slow-acting photocatalyst coating, (iii) counterfeit detection and (iv) evaluating new photocatalytic materials. The development and applications for such paiis have been reviewed in detail. | 0 | Theoretical and Fundamental Chemistry |
Non-systematic, less-recognized and often unverified syntheses of silicon carbide include:
* César-Mansuète Despretz's passing an electric current through a carbon rod embedded in sand (1849)
* Robert Sydney Marsden's dissolution of silica in molten silver in a graphite crucible (1881)
* Paul Schuetzenberger's heating of a mixture of silicon and silica in a graphite crucible (1881)
* Albert Colson's heating of silicon under a stream of ethylene (1882). | 1 | Applied and Interdisciplinary Chemistry |
Recently the possibility of study such compounds using molecular modeling assisted by informatic software has opened new possibilities in the study of the redox reaction of biomimetic compounds. For example, using "Density Functional Theory" (DFT) computer modeling made it possible to propose a catalytic pathway of H binding on the catalytic center of hydrogenase (Greco). Other example of the application of computational modeling in the study of hydrogenases is the work done by Breglia et al., whose results shows the chemical pathway of how oxygen inhibited the redox reaction of [NiFe] hydrogenases. | 1 | Applied and Interdisciplinary Chemistry |
The geologic component of the carbon cycle operates slowly in comparison to the other parts of the global carbon cycle. It is one of the most important determinants of the amount of carbon in the atmosphere, and thus of global temperatures.
Most of the Earths carbon is stored inertly in the Earths lithosphere. Much of the carbon stored in the Earth's mantle was stored there when the Earth formed. Some of it was deposited in the form of organic carbon from the biosphere. Of the carbon stored in the geosphere, about 80% is limestone and its derivatives, which form from the sedimentation of calcium carbonate stored in the shells of marine organisms. The remaining 20% is stored as kerogens formed through the sedimentation and burial of terrestrial organisms under high heat and pressure. Organic carbon stored in the geosphere can remain there for millions of years.
Carbon can leave the geosphere in several ways. Carbon dioxide is released during the metamorphism of carbonate rocks when they are subducted into the earth's mantle. This carbon dioxide can be released into the atmosphere and ocean through volcanoes and hotspots. It can also be removed by humans through the direct extraction of kerogens in the form of fossil fuels. After extraction, fossil fuels are burned to release energy and emit the carbon they store into the atmosphere. | 0 | Theoretical and Fundamental Chemistry |
With the rise of the environmentalist movement has also come an increased appreciation for social justice, and mining has showed similar trends lately. Societies located near potential mining sites are at increased risk to be subjected to injustices as their environment is affected by the changes made to mined lands—either public or private—that could eventually lead to problems in social structure, identity, and physical health (Franks 2009). Many have argued that by cycling mine power through local citizens, this disagreement can be alleviated, since both interest groups would have shared and equal voice and understanding in future goals. However, it is often difficult to match corporate mining interests with local social interests, and money is often a deciding factor in the successes of any disagreements. If communities are able to feel like they have a valid understanding and power in issues concerning their local environment and society, they are more likely to tolerate and encourage the positive benefits that come with mining, as well as more effectively promote alternative methods to heap leach mining using their intimate knowledge of the local geography (Franks 2009). | 1 | Applied and Interdisciplinary Chemistry |
Neuropeptides are released by dense core vesicles after depolarization of the cell. Compared to classical neurotransmitter signaling, neuropeptide signaling is more sensitive. Neuropeptide receptor affinity is in the nanomolar to micromolar range while neurotransmitter affinity is in the micromolar to millimolar range. Additionally, dense core vesicles contain a small amount of neuropeptide (3 - 10mM) compared to synaptic vesicles containing neurotransmitters (e.g. 100mM for acetylcholine). Evidence shows that neuropeptides are released after high-frequency firing or bursts, distinguishing dense core vesicle from synaptic vesicle release. Neuropeptides utilize volume transmission and are not reuptaken quickly, allowing diffusion across broad areas (nm to mm) to reach targets. Almost all neuropeptides bind to GPCRs, inducing second messenger cascades to modulate neural activity on long time-scales.
Expression of neuropeptides in the nervous system is diverse. Neuropeptides are often co-released with other neuropeptides and neurotransmitters, yielding a diversity of effects depending on the combination of release. For example, vasoactive intestinal peptide is typically co-released with acetylcholine. Neuropeptide release can also be specific. In Drosophila larvae, for example, eclosion hormone is expressed in just two neurons. | 1 | Applied and Interdisciplinary Chemistry |
Since the neutron is not charged it does not interact via the Coulomb force and therefore does not ionize the scintillation material. It must first transfer some or all of its energy via the strong force to a charged atomic nucleus. The positively charged nucleus then produces ionization. Fast neutrons (generally >0.5 MeV ) primarily rely on the recoil proton in (n,p) reactions; materials rich in hydrogen, e.g. plastic scintillators, are therefore best suited for their detection. Slow neutrons rely on nuclear reactions such as the (n,γ) or (n,α) reactions, to produce ionization. Their mean free path is therefore quite large unless the scintillator material contains nuclides having a high cross section for these nuclear reactions such as Li or B. Materials such as LiI(Eu) or glass silicates are therefore particularly well-suited for the detection of slow (thermal) neutrons. | 0 | Theoretical and Fundamental Chemistry |
When the days sky is overcast, sunlight passes through the turbidity layer of the clouds, resulting in scattered, diffuse light on the ground (sunbeam). This exhibits Mie scattering instead of Tyndall scattering because the cloud droplets are larger than the wavelength of the light and scatters all colors approximately equally. When the daytime sky is cloudless, the skys color is blue due to Rayleigh scattering instead of Tyndall scattering because the scattering particles are the air molecules, which are much smaller than the wavelengths of visible light. Similarly, the term Tyndall effect is incorrectly applied to light scattering by large, macroscopic dust particles in the air as due to their large size, they do not exhibit Tyndall scattering. | 0 | Theoretical and Fundamental Chemistry |
Southern Research is a not-for-profit US 501(c)(3) research organization that conducts basic and applied research for commercial and non-commercial organizations across four divisions: Drug development, Drug discovery, Energy & Environment, and Engineering. | 1 | Applied and Interdisciplinary Chemistry |
An organogel is a non-crystalline, non-glassy thermoreversible (thermoplastic) solid material composed of a liquid organic phase entrapped in a three-dimensionally cross-linked network. The liquid can be, for example, an organic solvent, mineral oil, or vegetable oil. The solubility and particle dimensions of the structurant are important characteristics for the elastic properties and firmness of the organogel. Often, these systems are based on self-assembly of the structurant molecules. (An example of formation of an undesired thermoreversible network is the occurrence of wax crystallization in petroleum.)
Organogels have potential for use in a number of applications, such as in pharmaceuticals, cosmetics, art conservation, and food. | 0 | Theoretical and Fundamental Chemistry |
In a chain-growth polymerization reaction, the reactive end-groups of a polymer chain react in each propagation step with a new monomer molecule transferring the reactive group to the last unit. Here the chain carrier is the polymer molecule with a reactive end-group, and at each step it is regenerated with the addition of one monomer unit: | 0 | Theoretical and Fundamental Chemistry |
On 23 September 1885, Auer von Welsbach received a patent on his development of the gas mantle, which he called Auerlicht, using a chemical mixture of 60% magnesium oxide, 20% lanthanum oxide and 20% yttrium oxide, which he called Actinophor. To produce a mantle, guncotton is impregnated with a mixture of Actinophor and then heated, the cotton eventually burns away, leaving a solid (albeit fragile) ash, which glows brightly when heated. These original mantles gave off a green-tinted light and were not very successful, and his first company formed to sell them failed in 1889.
In 1890 he introduced a new form of the mantle based on a mixture of 99% thorium dioxide and 1% cerium(IV) oxide, which he developed in collaboration with his colleague Ludwig Haitinger. These proved both more robust and having a much "whiter" light. Another company founded to produce the newer design was formed in 1891, working with fellow student from the university Ignaz Kreidl, and the device quickly spread throughout Europe.
In the United States this technique was adopted by The Coleman Company and became their logo for the company. In the 1980s it was reported that Thorium's radio-daughters (Decay products)
could be volatilized and released into the air upon incandescence of the mantle.
A lawsuit (Wagner v. Coleman) was brought against Coleman. The company changed its formulation to use non-radioactive materials, which apparently cost less and last longer. | 1 | Applied and Interdisciplinary Chemistry |
Dialkyl (E)-enones have been most commonly epoxidized using either lanthanide/BINOL systems or a magnesium tartrate catalyst.
For alkyl aryl (E)-enones, both polypeptides and lanthanide/BINOL catalysts give good yields and enantioselectivities. The most common polypeptide employed is poly-L-leucine.
Aryl alkyl (E)-enones have been epoxidized with high enantioselectivity using stoichiometric zinc peroxide systems. Polyleucine may be used with these substrates as well; when an existing stereocenter in the substrate biases the sense of selectivity of the epoxidation, polyleucine is able to overcome this bias.
Phase-transfer catalysis has been applied successfully to epoxidations of diaryl (E)-enones (chalcones). Lanthanide/BINOL is effective for this class of substrates as well.
(Z)-Enones are difficult to epoxidize without intermediate bond rotation to afford trans-epoxides. Lanthanide catalysts do effectively prevent bond rotation, however, and provide access to cis epoxide products.
With the lone exception of methylidene tetralone substrates, no general methods are available for the asymmetric nucleophilic epoxidation of trisubstituted double bonds. | 0 | Theoretical and Fundamental Chemistry |
When the temperature of a system changes, the Henry constant also changes. The temperature dependence of equilibrium constants can generally be described with the van t Hoff equation, which also applies to Henrys law constants:
where is the enthalpy of dissolution. Note that the letter in the symbol refers to enthalpy and is not related to the letter for Henrys law constants. This applies to the Henrys solubility ratio, ; for Henry's volatility ratio,, the sign of the right-hand side must be reversed.
Integrating the above equation and creating an expression based on at the reference temperature = 298.15 K yields:
The van 't Hoff equation in this form is only valid for a limited temperature range in which does not change much with temperature (around 20K of variations).
The following table lists some temperature dependencies:
Solubility of permanent gases usually decreases with increasing temperature at around room temperature. However, for aqueous solutions, the Henrys law solubility constant for many species goes through a minimum. For most permanent gases, the minimum is below 120 °C. Often, the smaller the gas molecule (and the lower the gas solubility in water), the lower the temperature of the maximum of the Henrys law constant. Thus, the maximum is at about 30 °C for helium, 92 to 93 °C for argon, nitrogen and oxygen, and 114 °C for xenon. | 0 | Theoretical and Fundamental Chemistry |
Via hydrogenation, benzene and its derivatives convert to cyclohexane and derivatives. This reaction is achieved by the use of high pressures of hydrogen in the presence of heterogeneous catalysts, such as finely divided nickel. Whereas alkenes can be hydrogenated near room temperatures, benzene and related compounds are more reluctant substrates, requiring temperatures >100 °C. This reaction is practiced on a large scale industrially. In the absence of the catalyst, benzene is impervious to hydrogen. Hydrogenation cannot be stopped to give cyclohexene or cyclohexadienes as these are superior substrates. Birch reduction, a non catalytic process, however selectively hydrogenates benzene to the diene. | 1 | Applied and Interdisciplinary Chemistry |
The general process control method is to monitor sludge blanket level, SVI (Sludge Volume Index), MCRT (Mean Cell Residence Time), F/M (Food to Microorganism), as well as the biota of the activated sludge and the major nutrients DO (Dissolved oxygen), nitrogen, phosphate, BOD (Biochemical oxygen demand), and COD (Chemical oxygen demand). In the reactor/aerator and clarifier system, the sludge blanket is measured from the bottom of the clarifier to the level of settled solids in the clarifier's water column; this, in large plants, can be done up to three times a day.
The SVI is the volume of settled sludge occupied by a given mass of dry sludge solids. It is calculated by dividing the volume of settled sludge in a mixed liquor sample, measured in milliliters per liter of sample (after 30 minutes of settling), by the MLSS (Mixed Liquor Suspended Solids), measured in grams per liter. The MCRT is the total mass (in kilograms or pounds) of mixed liquor suspended solids in the aerator and clarifier divided by the mass flow rate (in kilograms/pounds per day) of mixed liquor suspended solids leaving as WAS and final effluent. The F/M is the ratio of food fed to the microorganisms each day to the mass of microorganisms held under aeration. Specifically, it is the amount of BOD fed to the aerator (in kilograms/pounds per day) divided by the amount (in kilograms or pounds) of Mixed Liquor Volatile Suspended Solids (MLVSS) under aeration. Note: Some references use MLSS (Mixed Liquor Suspended Solids) for expedience, but MLVSS is considered more accurate for the measure of microorganisms. Again, due to expedience, COD is generally used, in lieu of BOD, as BOD takes five days for results.
Based on these control methods, the amount of settled solids in the mixed liquor can be varied by wasting activated sludge (WAS) or returning activated sludge (RAS).
The returning activated sludge is designed to recycle a portion of the activated sludge from the secondary clarifier back t the aeration tank. It usually includes a pump that draws the portion back.
The RAS line is designed considering the potential for clogging, settling, and other relatable issues that manage to impact the flow of the activated sludge back to the aeration tank. This line must handle the required flow of the plant and has to be designed to minimize the risk of solids settling or accumulating. | 1 | Applied and Interdisciplinary Chemistry |
Carbohydrate Research is a peer-reviewed scientific journal covering research on the chemistry of carbohydrates. It is published by Elsevier and was established in 1965. The editor-in-chief is M. Carmen Galan (University of Bristol). According to the Journal Citation Reports, the journal has a 2022 impact factor of 3.1. | 0 | Theoretical and Fundamental Chemistry |
Antonio de Ulloa was born in Seville, Spain, into an aristocratic and intellectually distinguished family. His father, Bernardo de Ulloa, was noted for his writings on economics. His brother Fernando would become an engineer and the chief of works of the Canal de Castilla. Destined for a naval career, at the age of thirteen Antonio embarked in Cádiz on the galleon San Luis, bound for the port of Cartagena de Indias (in present-day Colombia). After returning to Cádiz, Antonio entered the Real Compañía de Guardias Marinas (the Spanish Naval Academy) in 1733. | 1 | Applied and Interdisciplinary Chemistry |
Escape and radiate coevolution is a hypothesis proposing that a coevolutionary arms-race between primary producers and their consumers contributes to the diversification of species by accelerating speciation rates. The hypothesized process involves the evolution of novel defenses in the host, allowing it to "escape" and then "radiate" into differing species. | 1 | Applied and Interdisciplinary Chemistry |
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