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The four reactions in the Cu–Cl cycle are listed as follows:
#2 Cu + 2 HCl(g) → 2 CuCl(l) + H(g) (430–475 °C)
#2 CuCl + HO(g) → CuOCl + 2 HCl(g) (400 °C)
#2 CuOCl → 4 CuCl + O(g) (500 °C)
#2 CuCl → CuCl(aq) + Cu (ambient-temperature electrolysis)
: Net reaction: 2 HO → 2 H + O
: Legend: (g)—gas; (l)—liquid; (aq)—aqueous solution; the balance of the species are in a solid phase.
Atomic Energy of Canada Limited has demonstrated experimentally a CuCl electrolyzer in which hydrogen is produced electrolytically at the cathode and Cu(I) is oxidized to Cu(II) at the anode, thereby combining above steps 1 and 4 to eliminate the intermediate production and subsequent transport of solid copper.
Approximately 50% of the heat required to drive this reaction can be captured from the reaction itself. The other heat can be provided by any suitable process. Recent research has focused on a cogeneration scheme using the waste heat from nuclear reactors, specifically the CANDU supercritical water reactor. | 0 | Theoretical and Fundamental Chemistry |
The most noticeable form of foam is foam floating on the stock surface. It is easy to monitor and relatively easy to handle and is more a cosmetic issue. Surface foam may cause problems with liquid levels and give overflow leading to pools of oils around the equipment which is a safety concern.
Additionally, this might reduce the process speed and availability of process equipment. The main mechanical problem tends to be when foam enters the system as air is a poor lubricant, meaning metal to metal contact can occur. | 0 | Theoretical and Fundamental Chemistry |
The salt can be easily prepared by oxidizing a soluble silver salt with excess potassium peroxydisulfate in aqueous pyridine solution, where upon the product precipitates out almost quantitatively.
: 2 AgNO + 8 CHN + 3 KSO → 2 [Ag(CHN)]SO + 2 KSO + 2 KNO | 0 | Theoretical and Fundamental Chemistry |
A common pathological cause for a high BMR is fever, since a rise in body temperature increases the rate of cellular metabolic reactions. It is estimated that for every degree Fahrenheit of rise in body temperature, the BMR increases by 7 percent.
Thyroid disease also has a marked effect on BMR, since thyroid hormones regulate the rate of cellular metabolism. Hyperthyroidism—in which there is an increase in the production of thyroid hormones—leads to a high BMR, while hypothyroidism—in which thyroid hormones are depleted—causes a low BMR.
Prolonged periods of abnormal nutrition cause an adaptive change in BMR; this helps the body to maintain a stable body weight in response to the change in food supply. In prolonged malnutrition, the BMR declines, while in prolonged overnutrition, the BMR is increased. Cancer sometimes causes an increase in BMR, perhaps because the cancer cells that form tumors have a high level of metabolic activity. | 1 | Applied and Interdisciplinary Chemistry |
In the first step, manganese(II) sulphate (at 48% of the total volume) is added to an environmental water sample. Next, potassium iodide (15% in potassium hydroxide 70%) is added to create a pinkish-brown precipitate. In the alkaline solution, dissolved oxygen will oxidize manganese(II) ions to the tetravalent state.
: 2 Mn + O + 2 HO → 2 MnO(OH)
Mn has been oxidised to 4+, and MnO(OH) appears as a brown precipitate. There is some uncertainty about whether the oxidised manganese is tetravalent or trivalent. Some sources claim that Mn(OH) is the brown precipitate, but hydrated MnO may also give the brown colour.
: 4 Mn(OH) + O + 2 HO → 4 Mn(OH)
The second part of the Winkler test reduces (acidifies) the solution. The precipitate will dissolve back into solution as the H reacts with the O and OH to form water.
: MnO(OH) + 4 H → Mn + 3 HO
The acid facilitates the conversion by the brown, Manganese-containing precipitate of the Iodide ion into elemental Iodine.
The Mn(SO) formed by the acid converts the iodide ions into iodine, itself being reduced back to manganese(II) ions in an acidic medium.
: Mn(SO) + 2 I → Mn + I + 2
Thiosulfate is used, with a starch indicator, to titrate the iodine.
: 2 + I → + 2 I | 0 | Theoretical and Fundamental Chemistry |
In October 2018, Dr. Khaled received the People First Leader GCC HR Award for his government services at the 6th Annual GOV HR Summit. Abu Dhabi, UAE. | 1 | Applied and Interdisciplinary Chemistry |
The NGO scandal heavily disturbed his image and also his private life. Even though he cooperated with intelligence agencies in hope of being released, and went back to PAEC; he was declined any partial freedom. He was harshly interrogated for a long time, which also resulted in his death. Bashir Syed, former President of the Association of Pakistani Scientists and Engineers of North America (APSENA), said: "I know both of these persons and can tell you there is not an iota of truth that both these respected scientists and friends will do anything to harm the interest of their own country." | 0 | Theoretical and Fundamental Chemistry |
Different processes and techniques have been developed around melt spinning which offer advantages to the industrial applications and product consistency. | 1 | Applied and Interdisciplinary Chemistry |
The Mandelin reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It is composed of a mixture of ammonium metavanadate and concentrated sulfuric acid. Its primary use is for the detection of ketamine and PMA Unlike the most common reagent test chemicals, it has a deep red colour that changes to yellow if there is no alkaloid, which occurs within about 48 hours of mixing.
The United States Department of Justice method for producing the reagent is the addition of 100 mL of concentrated (95–98%) sulfuric acid to 0.5-1 g of Ammonium metavanadate.
This reagent was invented by the German pharmacologist, Karl Friedrich Mandelin (1854–1906) at the University of Dorpat. | 0 | Theoretical and Fundamental Chemistry |
Thioredoxin reductase uses a cysteine-selenocysteine pair to reduce the disulfide in thioredoxin. The selenocysteine is arranged in an unusual Sec-His-Glu catalytic triad, which tunes its pKa. | 1 | Applied and Interdisciplinary Chemistry |
Anandamide and N-arachidonoyl dopamine (NADA) have been shown to act on temperature-sensing TRPV1 channels, which are involved in thermoregulation. TRPV1 is activated by the exogenous ligand capsaicin, the active component of chili peppers, which is structurally similar to endocannabinoids. NADA activates the TRPV1 channel with The high potency makes it the putative endogenous TRPV1 agonist. Anandamide has also been found to activate TRPV1 on sensory neuron terminals, and subsequently cause vasodilation. TRPV1 may also be activated by methanandamide and arachidonyl-2'-chloroethylamide (ACEA). | 1 | Applied and Interdisciplinary Chemistry |
The liver, gastrointestinal tract (GIT), lungs, kidney, and brain are among the tissues that participate in the chiral inversion of medicines. The liver has been shown to be the most crucial organ in the development of this mechanism. Although some studies contend that rat liver homogenates lack the enzymatic mechanisms necessary to invert the R-enantiomers of flurbiprofen, naproxen, suprofen, and ibuprofen, the liver may also be involved in the inversion of R-ibuprofen in rats. On the other hand, it was noted that certain medicines underwent chiral inversion without the involvement of the liver (hepatocytes). Although liver did not play a substantial role in the inversion of benoxaprofen, studies using benoxaprofen and ketoprofen show that one of the primary sites of inversion in rats is the GI tract. | 0 | Theoretical and Fundamental Chemistry |
Multiple chemical approaches exist to encourage selectivity of α- and β-glycosidic bonds. The highly substrate specific nature of the selectivity and the overall activity of the pyranoside can provide major synthetic difficulties. The overall specificity of the glycosylation can be improved by utilizing approaches which take into account the relative transition states that the anomeric carbon can undergo during a typical glycosylation. Most notably, recognition and incorporation of Felkin-Ahn-Eisenstein models into rationale chemical design can generally provide reliable results provided the transformation can undergo this type of conformational control in the transition state.
Fluorine directed glycosylations represent an encouraging handle for both B selectivity and introduction of a non-natural biomimetic C2 functionality on the carbohydrate. One innovative example provided by Bucher et al. provides a way to utilize a fluoro oxonium ion and the trichloroacetimidate to encourage B stereoselectivity through the gauche effect. This reasonable stereoselectivity is clear through visualization of the Felkin-Ahn models of the possible chair forms.
This method represents an encouraging way to selectivity incorporate B-ethyl, isopropyl and other glycosides with typical trichloroacetimidate chemistry. | 0 | Theoretical and Fundamental Chemistry |
Samples for dating need to be converted into a form suitable for measuring the content; this can mean conversion to gaseous, liquid, or solid form, depending on the measurement technique to be used. Before this can be done, the sample must be treated to remove any contamination and any unwanted constituents. This includes removing visible contaminants, such as rootlets that may have penetrated the sample since its burial. Alkali and acid washes can be used to remove humic acid and carbonate contamination, but care has to be taken to avoid removing the part of the sample that contains the carbon to be tested. | 0 | Theoretical and Fundamental Chemistry |
The idea of boosting was originally developed between late 1947 and late 1949 at Los Alamos. The primary benefit of boosting is further miniaturization of nuclear weapons as it reduces the minimum inertial confinement time required for a supercritical nuclear explosion by providing a sudden influx of fast neutrons before the critical mass would blow itself apart. This would eliminate the need for an aluminum pusher and uranium tamper and the explosives needed to push them and the fissile material into a supercritical state. While the bulky Fat Man had a diameter of and required 3 tons of high explosives for implosion, a boosted fission primary can be fitted on a small nuclear warhead (such as the W88) to ignite the thermonuclear secondary. | 0 | Theoretical and Fundamental Chemistry |
Many elegant structural mimics have been synthesized reproducing the atomic content and connectivity of the active site. The work by Pickett is a prime example of this field. The catalytic activity of these mimics do not however compare to the native enzyme. In contrast, functional mimics, also known as bio-inspired catalysts, aim to reproduce only the functional features of an enzyme often through the use of different atomic content and connectivity from that found in the native enzymes. Functional mimics have made advances in the reactive chemistry and have implications on the mechanistic activity of the enzyme as well as acting as catalysts in their own right. | 1 | Applied and Interdisciplinary Chemistry |
The outgassing of volatile silicones on low Earth orbit devices leads to presence of a cloud of contaminants around the spacecraft. Together with atomic oxygen bombardment, this may lead to gradual deposition of thin layers of carbon-containing silicon dioxide. Their poor transparency is a concern in case of optical systems and solar panels. Deposits of up to several micrometers were observed after 10 years of service on the solar panels of the Mir space station.
Other sources of problems for structures subjected to outer space are erosion and redeposition of the materials by sputtering caused by fast atoms and micrometeoroids. Another major concern, though of non-corrosive kind, is material fatigue caused by cyclical heating and cooling and associated thermal expansion mechanical stresses. | 1 | Applied and Interdisciplinary Chemistry |
p75NTR is a type I transmembrane protein, with a molecular weight of 75 kDa, determined by glycosylation through both N- and O-linkages in the extracellular domain.
It consists of an extracellular domain, a transmembrane domain and an intracellular domain. The extracellular domain consists of a stalk domain connecting the transmembrane domain and four cysteine-rich repeat domains, CRD1, CRD2, CRD3, and CRD4; which are negatively charged, a property that facilitates Neurotrophin binding. The intracellular part is a global-like domain, known as a death domain, which consists of two sets of perpendicular helixes arranged in sets of three. It connects the transmembrane domain through a flexible linker region N-terminal domain. It is important to say that, in contrast to the type I death domain found in other TNFR proteins, the type II intracellular death domain of p75NTR does nor self-associated. This was an early indication that p75NTR does nor signal death through the same mechanism as the TNFR death domains, although the ability of the p75NTR death domain to activate other second messengers is conserved.
The p75ECD-binding interface to NT-3 can be divided into three main contact sites, two in the case of NGF, that are stabilized by hydrophobic interactions, salt bridges, and hydrogen bonds. The junction regions between CDR1 and CDR2 form the site 1 that contains five hydrogen bonds and one salt bridge. Site 2 is formed by equal contributions from CDR3 and CRD4 and involves two salt bridges and two hydrogen bonds. Site 3, in the CRD4, includes only one salt bridge. | 1 | Applied and Interdisciplinary Chemistry |
In polymer systems, the general definition () holds; the elementary constituents are now the monomers making up the chains. However, the structure factor being a measure of the correlation between particle positions, one can reasonably expect that this correlation will be different for monomers belonging to the same chain or to different chains.
Let us assume that the volume contains identical molecules, each composed of monomers, such that ( is also known as the degree of polymerization). We can rewrite () as:
where indices label the different molecules and the different monomers along each molecule. On the right-hand side we separated intramolecular () and intermolecular () terms. Using the equivalence of the chains, () can be simplified:
where is the single-chain structure factor. | 0 | Theoretical and Fundamental Chemistry |
The mechanism of action of AVEC relies upon the immunity acquired through vaccination or natural illness against microbials (e.g., viruses, bacteria, etc.) being redirected, amplified, and accelerated against the cancer cells. For example, a person vaccinated against hepatitis B virus, but suffering from HER2+ breast cancer receives AVEC, consisting of the antibody against HER2 and vaccine against HBV (AVEC: anti-HER2 - HBV). Since this persons immune system has already prepared a response to the HBV virus, it will instantly attack any cell tagged by it, in this case the breast cancer cells, overexpressing HER2. As such, AVEC attracts the components of the immune response like a lightning-rod attracts the thunderbolts during storms. | 1 | Applied and Interdisciplinary Chemistry |
Kerogen formation continued to a depth of about 1 km from the Earths surface where temperatures may reach around 50 °C. Kerogen formation represents a halfway point between organic matter and fossil fuels: kerogen can be exposed to oxygen, oxidize and thus be lost, or it could be buried deeper inside the Earths crust and be subjected to conditions which allow it to slowly transform into fossil fuels like petroleum. The latter happened through catagenesis in which the reactions were mostly radical rearrangements of kerogen. These reactions took thousands to millions of years and no external reactants were involved. Due to the radical nature of these reactions, kerogen reacted towards two classes of products: those with low H/C ratio (anthracene or products similar to it) and those with high H/C ratio (methane or products similar to it); i.e., carbon-rich or hydrogen-rich products. Because catagenesis was closed off from external reactants, the resulting composition of the fuel mixture was dependent on the composition of the kerogen via reaction stoichiometry. Three types of kerogen exist: type I (algal), II (liptinic) and III (humic), which were formed mainly from algae, plankton and woody plants (this term includes trees, shrubs and lianas) respectively.
Catagenesis was pyrolytic despite the fact that it happened at relatively low temperatures (when compared to commercial pyrolysis plants) of 60 to several hundred °C. Pyrolysis was possible because of the long reaction times involved. Heat for catagenesis came from the decomposition of radioactive materials of the crust, especially K, Th, U and U. The heat varied with geothermal gradient and was typically 10–30 °C per km of depth from the Earth's surface. Unusual magma intrusions, however, could have created greater localized heating. | 0 | Theoretical and Fundamental Chemistry |
A longitudinal facial crack is a specialized type of defect that only occurs in continuous casting processes. This defect is caused by uneven cooling, both primary cooling and secondary cooling, and includes molten steel qualities, such as the chemical composition being out of specification, cleanliness of the material, and homogeneity. | 1 | Applied and Interdisciplinary Chemistry |
In host–guest chemistry, an inclusion compound (also known as an inclusion complex) is a chemical complex in which one chemical compound (the "host") has a cavity into which a "guest" compound can be accommodated. The interaction between the host and guest involves purely van der Waals bonding. The definition of inclusion compounds is very broad, extending to channels formed between molecules in a crystal lattice in which guest molecules can fit. | 0 | Theoretical and Fundamental Chemistry |
Plants in temperate and polar regions adapt to winter and sub zero temperatures by relocating nutrients from leaves and shoots to storage organs. Freezing temperatures induce dehydrative stress on plants, as water absorption in the root and water transport in the plant decreases. Water in and between cells in the plant freezes and expands, causing tissue damage. Cold hardening is a process in which a plant undergoes physiological changes to avoid, or mitigate cellular injuries caused by sub-zero temperatures. Non-acclimatized individuals can survive −5 °C, while an acclimatized individual in the same species can survive −30 °C. Plants that originated in the tropics, like tomato or maize, don't go through cold hardening and are unable to survive freezing temperatures. The plant starts the adaptation by exposure to cold yet still not freezing temperatures. The process can be divided into three steps. First the plant perceives low temperature, then converts the signal to activate or repress expression of appropriate genes. Finally, it uses these genes to combat the stress, caused by sub-zero temperatures, affecting its living cells. Many of the genes and responses to low temperature stress are shared with other abiotic stresses, like drought or salinity.
When temperature drops, the membrane fluidity, RNA and DNA stability, and enzyme activity change. These, in turn, affect transcription, translation, intermediate metabolism, and photosynthesis, leading to an energy imbalance. This energy imbalance is thought to be one of the ways the plant detects low temperature. Experiments on arabidopsis show that the plant detects the change in temperature, rather than the absolute temperature. The rate of temperature drop is directly connected to the magnitude of calcium influx, from the space between cells, into the cell. Calcium channels in the cell membrane detect the temperature drop, and promotes expression of low temperature responsible genes in alfalfa and arabidopsis. The response to the change in calcium elevation depends on the cell type and stress history. Shoot tissue will respond more than root cells, and a cell that already is adapted to cold stress will respond more than one that has not been through cold hardening before. Light doesn't control the onset of cold hardening directly, but shortening of daylight is associated with fall, and starts production of reactive oxygen species and excitation of photosystem 2, which influences low-temp signal transduction mechanisms. Plants with compromised perception of day length have compromised cold acclimation.
Cold increases cell membrane permeability and makes the cell shrink, as water is drawn out when ice is formed in the extracellular matrix between cells. To retain the surface area of the cell membrane so it will be able to regain its former volume when temperature rises again, the plant forms more and stronger Hechtian strands. These are tubelike structures that connect the protoplast with the cell wall. When the intracellular water freezes, the cell will expand, and without cold hardening the cell would rupture. To protect the cell membrane from expansion induced damage, the plant cell changes the proportions of almost all lipids in the cell membrane, and increases the amount of total soluble protein and other cryoprotecting molecules, like sugar and proline.
Chilling injury occurs at 0–10 degrees Celsius, as a result of membrane damage, metabolic changes, and toxic buildup. Symptoms include wilting, water soaking, necrosis, chlorosis, ion leakage, and decreased growth. Freezing injury may occur at temperatures below 0 degrees Celsius. Symptoms of extracellular freezing include structural damage, dehydration, and necrosis. If intracellular freezing occurs, it will lead to death. Freezing injury is a result of lost permeability, plasmolysis, and post-thaw cell bursting.
When spring comes, or during a mild spell in winter, plants de-harden, and if the temperature is warm for long enough – their growth resumes. | 1 | Applied and Interdisciplinary Chemistry |
Canada deuterium uranium fuel (CANDU) fuel bundles are about long and in diameter. They consist of sintered (UO) pellets in zirconium alloy tubes, welded to zirconium alloy end plates. Each bundle weighs roughly , and a typical core loading is on the order of 4500–6500 bundles, depending on the design. Modern types typically have 37 identical fuel pins radially arranged about the long axis of the bundle, but in the past several different configurations and numbers of pins have been used. The CANFLEX bundle has 43 fuel elements, with two element sizes. It is also about 10 cm (4 inches) in diameter, 0.5 m (20 in) long and weighs about 20 kg (44 lb) and replaces the 37-pin standard bundle. It has been designed specifically to increase fuel performance by utilizing two different pin diameters. Current CANDU designs do not need enriched uranium to achieve criticality (due to the lower neutron absorption in their heavy water moderator compared to light water), however, some newer concepts call for low enrichment to help reduce the size of the reactors. The Atucha nuclear power plant in Argentina, a similar design to the CANDU but built by German KWU was originally designed for non-enriched fuel but since switched to slightly enriched fuel with a content about 0.1 percentage points higher than in natural uranium. | 0 | Theoretical and Fundamental Chemistry |
Human fat was mentioned in European pharmacopoeias since the 16th century as an important fatty component of quality deemed ointments and other pharmaceuticals in Europe. In old recipes human adipose tissue was mentioned as Pinguedo hominis, or Axungia hominis. The German medicinal Johann Agricola (1496–1570) described the recovery of human fat and its applications.
In traditional medicine in Europe, human fat was believed to have a healing magic significance until the 19th century. Many executioners recovered the fat from the bodies of their executants, called "Armsünderfett" or "Armsünderschmalz" (German: fat or grease from poor sinners put to death), and sold it. For some executioners the marketing of human fat was a major source of revenue. The human fat was used to make ointments for treatment of various diseases such as bone pain, toothache and gout. It was also regarded as a panacea for particular diseases associated with cachexia (e.g. tuberculosis). Also an analgesic effect in rheumatoid arthritis was given to human fat.
From the late 19th century, human fat was produced and offered under the trade name Humanol as a sterile, liquified preparation for injections in Germany. In 1909 it was introduced for surgical treatment of scars, wound disinfection, and wound revisions. In the 1920s it became out of fashion after low cure rates and the incidence of fat embolisms caused by its application.
Until the 1960s various manufacturers offered alleged wrinkle creams for external use (Hormocenta of Hormocenta Cosmetic Böttger GmbH, or Placentubex C of Merz Pharmaceuticals) containing human fat from placentas collected from midwives and obstetric departments for industrial purposes. The use of human placentas was terminated in favour of animal products. In Peru a group of gangsters called pishtacos was accused of having manufactured and marketed human fat; the case turned out as a free invention of the investigators. | 1 | Applied and Interdisciplinary Chemistry |
Methanesulfonyl chloride react with primary and secondary amines to give methanesulfonamides. Unlike methanesulfonates, methanesulfonamides are very resistant toward hydrolysis under both acidic and basic conditions. When used as a protecting group, they can be converted back to amines using lithium aluminium hydride or a dissolving metal reduction. | 0 | Theoretical and Fundamental Chemistry |
A sperm bank, semen bank, or cryobank is a facility or enterprise which purchases, stores and sells human semen. The semen is produced and sold by men who are known as sperm donors. The sperm is purchased by or for other persons for the purpose of achieving a pregnancy or pregnancies other than by a sexual partner. Sperm sold by a sperm donor is known as donor sperm.
A sperm bank may be a separate entity supplying donor sperm to individuals or to fertility centers or clinics, or it may be a facility which is run by a clinic or other medical establishment mainly or exclusively for their patients or customers.
A pregnancy may be achieved using donor sperm for insemination with similar outcomes to sexual intercourse. By using sperm from a donor rather than from the sperm recipient's partner, the process is a form of third party reproduction. In the 21st century artificial insemination with donor sperm from a sperm bank is most commonly used for individuals with no male partner, i.e. single women and coupled lesbians.
A sperm donor must generally meet specific requirements regarding age and screening for medical history. In the United States, sperm banks are regulated as Human Cell and Tissue or Cell and Tissue Bank Product (HCT/Ps) establishments by the Food and Drug Administration. Many states also have regulations in addition to those imposed by the FDA. In the European Union a sperm bank must have a license according to the EU Tissue Directive. In the United Kingdom, sperm banks are regulated by the Human Fertilisation and Embryology Authority. | 1 | Applied and Interdisciplinary Chemistry |
Oxide dispersion strengthened alloys (ODS) are alloys that consist of a metal matrix with small oxide particles dispersed within it. They have high heat resistance, strength, and ductility. Alloys of nickel are the most common but includes iron aluminum alloys.
Applications include high temperature turbine blades and heat exchanger tubing, while steels are used in nuclear applications. ODS materials are used on spacecraft to protect the vehicle, especially during re-entry. Noble metal ODS alloys, for example, platinum-based alloys, are used in glass production.
When it comes to re-entry at hypersonic speeds, the properties of gases change dramatically. Shock waves that can cause serious damage on any structure are created. At these speeds and temperatures, oxygen becomes aggressive. | 1 | Applied and Interdisciplinary Chemistry |
Note: The table only lists a few examples, there are many more crosses. The possibilities of this technology are great; however, not all species are easily put into protoplast culture. | 1 | Applied and Interdisciplinary Chemistry |
As hyrax middens have been developed as palaeoenvironmental archives, there has been increasing emphasis on the application of stable isotope analyses to midden sequences. Initially this focussed on the use of bulk C data, with an emphasis on identifying changes in the relative abundance of C/C/CAM vegetation and associated palaeoecological/palaeoenvironmental inferences. This is useful in climatic transition zones, such as the Western Cape Province of South Africa, where modern rainfall seasonality has a strong impact on C/C grass distributions. δC records can also be used in some ecoregions, such as the dry savannah at Spitzkoppe in Namibia, as an indicator of the reliability of grass cover. As hyraxes will preferentially graze (grasses are C in the region), more depleted δC values from hyrax middens have been interpreted as evidence that the animals were forced to obtain a greater proportion of their diet from trees and shrubs, which are less susceptible to extended periods of drought. However, these data do not necessarily provide a direct and unambiguous indicator of past arid/humid shifts. As such, other studies have focussed on the use of δN data as a potential proxy for water availability in the environment | 0 | Theoretical and Fundamental Chemistry |
Transposon mutagenesis was first studied by Barbara McClintock in the mid-20th century during her Nobel Prize-winning work with corn. McClintock received her BSc in 1923 from Cornell’s College of Agriculture. By 1927 she had her PhD in botany, and she immediately began working on the topic of maize chromosomes. In the early 1940s, McClintock was studying the progeny of self-pollinated maize plants which resulted from crosses having a broken chromosome 9. These plants were missing their telomeres. This research prompted the first discovery of a transposable element, and from there transposon mutagenesis has been exploited as a biological tool. | 1 | Applied and Interdisciplinary Chemistry |
This experiment shows the catalyzed decomposition of hydrogen peroxide. Hydrogen peroxide (HO) decomposes into water and oxygen gas, which is in the form of foam, but normally the reaction is too slow to be easily perceived or measured:
In normal conditions, this reaction takes place very slowly, therefore a catalyst is added to speed up the reaction, which will result in rapid formation of foam. The iodide ion from potassium iodide acts as a catalyst and speeds up the reaction while remaining chemically unchanged in the reaction process. The iodide ion changes the mechanism by which the reaction occurs:
The reaction is exothermic; the foam produced is hot (about 75°C or 167°F). A glowing splint can be used to show that the gas produced is oxygen.
The rate of foam formation measured in volume per time unit has a positive correlation with the peroxide concentration (v/V%), which means that more foam will be generated per unit time when a more concentrated peroxide solution is used. | 1 | Applied and Interdisciplinary Chemistry |
Time crystals seem to break time-translation symmetry and have repeated patterns in time even if the laws of the system are invariant by translation of time. The time crystals that are experimentally realized show discrete time-translation symmetry breaking, not the continuous one: they are periodically driven systems oscillating at a fraction of the frequency of the driving force. (According to Philip Ball, DTC are so-called because "their periodicity is a discrete, integer multiple of the driving period".)
The initial symmetry, which is the discrete time-translation symmetry () with , is spontaneously broken to the lower discrete time-translation symmetry with , where is time, the driving period, an integer.
Many systems can show behaviors of spontaneous time-translation symmetry breaking but may not be discrete (or Floquet) time crystals: convection cells, oscillating chemical reactions, aerodynamic flutter, and subharmonic response to a periodic driving force such as the Faraday instability, NMR spin echos, parametric down-conversion, and period-doubled nonlinear dynamical systems.
However, discrete (or Floquet) time crystals are unique in that they follow a strict definition of discrete time-translation symmetry breaking:
* it is a broken symmetry the system shows oscillations with a period longer than the driving force,
* the system is in crypto-equilibrium these oscillations generate no entropy, and a time-dependent frame can be found in which the system is indistinguishable from an equilibrium when measured stroboscopically (which is not the case of convection cells, oscillating chemical reactions and aerodynamic flutter),
* the system exhibits long-range order the oscillations are in phase (synchronized) over arbitrarily long distances and time.
Moreover, the broken symmetry in time crystals is the result of many-body interactions: the order is the consequence of a collective process, just like in spatial crystals. This is not the case for NMR spin echos.
These characteristics makes discrete time crystals analogous to spatial crystals as described above and may be considered a novel type or phase of nonequilibrium matter. | 0 | Theoretical and Fundamental Chemistry |
The most commonly used surface modification protocols are plasma activation, wet chemical treatment, including grafting, and thin-film coating. Surface energy mimicking is a technique that enables merging the device manufacturing and surface modifications, including patterning, into a single processing step using a single device material.
Many techniques can be used to enhance wetting. Surface treatments, such as corona treatment, plasma treatment and acid etching, can be used to increase the surface energy of the substrate. Additives can also be added to the liquid to decrease its surface tension. This technique is employed often in paint formulations to ensure that they will be evenly spread on a surface. | 0 | Theoretical and Fundamental Chemistry |
OVERFLOW was developed as part of a collaborative effort between NASAs Johnson Space Center in Houston, Texas and NASA Ames Research Center (ARC) in Moffett Field, California. The driving force behind this work was the need for evaluating the flow about the Space Shuttle launch vehicle. Originally developed in the early 1990s by NASAs Pieter Buning, Dennis Jespersen and others, the code is an outgrowth of earlier codes F3D and ARC3D, and a result of ARC's long history of flow-solver development. | 1 | Applied and Interdisciplinary Chemistry |
Mediated transport refers to transport mediated by a membrane transport protein. Substances in the human body may be hydrophobic, electrophilic, contain a positively or negatively charge, or have another property. As such there are times when those substances may not be able to pass over the cell membrane using protein-independent movement. The cell membrane is imbedded with many membrane transport proteins that allow such molecules to travel in and out of the cell. There are three types of mediated transporters: uniport, symport, and antiport. Things that can be transported are nutrients, ions, glucose, etc, all depending on the needs of the cell. One example of a uniport mediated transport protein is GLUT1. GLUT1 is a transmembrane protein, which means it spans the entire width of the cell membrane, connecting the extracellular and intracellular region. It is a uniport system because it specifically transports glucose in only one direction, down its concentration gradient across the cell membrane.
Another example of a uniporter mediated transport protein is microsomal triglyceride transfer protein (MTTP) who is responsible for catalyzing the assembly of the triglyceride rich lipoproteins as well mediating their release from the lumen of the endoplasmic reticulum. What is distinguishable about this specific transfer protein is that it requires the protein PRAP1 to bind to the lipoprotein to facilitate the transport of said lipoprotein. MTTP only recognizes the PRAP1-lipoprotein complex and only then will it catalyze the transport reaction. In a way, the PRAP1 protein acts as a signal for MTTP. The importance of such interactions implies that mediated transport is not only dependent on transmembrane proteins but can also require the presence of additional non-transmembrane proteins. For instance, studies show that in the absence of a fully functional PRAP1 protein, MTTP fails to transport specific lipoproteins across the endoplasmic reticulum membrane.
An example of a symporter mediated transport protein is SGLT1, a sodium/glucose co-transporter protein that is mainly found in the intestinal tract. The SGLT1 protein is a symporter system because it passes both glucose and sodium in the same direction, from the lumen of the intestine to inside the intestinal cells.
An example of an antiporter mediated transport protein is the sodium-calcium antiporter, a transport protein involved in keeping the cytoplasmic concentration of calcium ions in the cells, low. This transport protein is an antiporter system because it transports three sodium ions across the plasma membrane in exchange for a calcium ion, which is transported in the opposite direction.
Mechanism of transport. A molecule will bind to a transporter protein, altering its shape. The change of shape or other added substances such as ATP will, in turn, cause the transport protein to alter its shape and release the molecule onto the other side of the cell membrane. | 1 | Applied and Interdisciplinary Chemistry |
Methane was premixed with fuel in the form of either O, NO, or air and burned at ambient pressure. The source of nitrogen was introduced by addition of 1-5 mole% NH gas and sulfur by 0.01-0.5 mol% HS or SF gas. A steady state concentration of NS within the flame front is observed by laser-induced fluorescence (LIF) spectrum. | 0 | Theoretical and Fundamental Chemistry |
Proto-porcelain material has been discovered dating back to the Neolithic period, with shards of material found in archaeological sites from the Eastern Han period in China. These wares are estimated to have been fired from 1260 °C to 1300 °C. In the 8th century, porcelain was invented in Tang Dynasty, China. Porcelain in china resulted in a methodical development of widely used kilns that increased the quality and quantity that porcelain could be produced. Tin-glazing of ceramics is invented by Arabic chemists and potters in Basra, Iraq.
During the Early Middle Ages, the technique of creating windows steered more towards glass blowing non-tinted balls that were later flattened, but then in the late Middle Ages; the methodology returned to that from antiquity with a few minor adjustments, which included rolling with metallic rollers.
In the 9th century, stonepaste ceramics were invented in Iraq, and lustreware appeared in Mesopotamia. In the 11th century, Damascus steel is developed in the Middle East. In the 15th century, Johann Gutenberg develops type metal alloy and Angelo Barovier invents cristallo, a clear soda-based glass. | 1 | Applied and Interdisciplinary Chemistry |
Triplet-triplet annihilation combines the energy of two triplet-excited molecules onto one molecule to produce a higher excited state. Since the higher excited state is an emissive singlet state, TTA can be used to achieve photon upconversion which is a process that converts the energy of two photons into one photon of higher energy.
To achieve photon upconversion through triplet-triplet annihilation two types of molecules are often combined: a sensitizer and an emitter (annihilator). The sensitizer absorbs the low energy photon and populates its first excited triplet state (T) through intersystem crossing. The sensitizer then transfers the excitation energy to the emitter, resulting in a triplet excited emitter and a ground state sensitizer. Two triplet-excited emitters can then undergo triplet-triplet annihilation to produce a singlet excited state (S) of the emitter, which can emit an upconverted photon. | 0 | Theoretical and Fundamental Chemistry |
Hydrazones are a class of organic compounds with the structure . They are related to ketones and aldehydes by the replacement of the oxygen =O with the = functional group. They are formed usually by the action of hydrazine on ketones or aldehydes. | 0 | Theoretical and Fundamental Chemistry |
CellViewer allows to visualize the sample material in four modes widely used in material research:
* 3D model of atomic structure (direct space),
* simulated diffraction pattern (reciprocal space),
* stereographic projection (projection of 3D space of crystallographic planes and directions to 2D),
* inverse pole figure (defined part of stereographic projection).
Graphical user interface provides user with two interactive views side by side. These views can display arbitrary combination of the four aforementioned visualization modes allowing to perceive their mutual relations. For instance, rotation of the atomic structure in direct space leads (if set so) to an instant update of the simulated diffraction pattern. If any diffraction spot is selected, corresponding crystallographic planes are shown in the unit cell etc. Such interconnections are implemented for each pair of the four available visualization modes. The electronic visualization allows to simplify understanding of widely used, yet less intuitive representations such as the inverse pole figure. For instance by drawing the coloured triangle of the inverse pole figure into the stereographic projection or to the more intuitive 3D atomic structure. | 0 | Theoretical and Fundamental Chemistry |
Kaminsky's discovery of well-defined, high activity homogeneous catalysts led to many innovations in the design of novel cyclopentadienyl ligands. These innovations include ansa-metallocenes, C-symmetric fluorenyl-Cp ligands, constrained geometry catalysts, Some Kaminsky-inspired catalysts use of chiral metallocenes that have bridged cyclopentadienyl rings. These innovations made possible highly stereoselective (or stereoregular) polymerization of α-olefins, some of which have been commercialized. | 0 | Theoretical and Fundamental Chemistry |
The most familiar yeast in food production, Saccharomyces cerevisiae, has been used in brewing and baking for thousands of years.
S. cerevisiae feeds on the sugars present in the bread dough and produces the gas carbon dioxide. This forms bubbles within the dough, causing it to expand and the bread to rise.
Several different yeasts are used in brewing beer, where they ferment the sugars present in malted barley to produce alcohol. One of the most common is S. cerevisiae. The same strain of S. cerevisiae which can also be used in breadmaking is used to make ale-type beers. It is known as a top-fermenting yeast because it creates a foam on the top of the brew. Bottom-fermenting yeasts, such as S. pastorianus, are more commonly used to make lagers. They ferment more of the sugars in the mixture than top-fermenting yeasts, which gives a cleaner taste.
The alcohol in wine is formed by the fermentation of the sugars in grape juice, with carbon dioxide as a by-product. Yeast is naturally present on grapeskins, and this alone can be sufficient for the fermentation of sugars to alcohol to occur. A pure yeast culture, most often S. cerevisiae, is usually added to ensure the fermentation is reliable. Other yeast cultures like Pichia, Torulaspora and Kluyveromyces are naturally present or added to create special flavours in the wine. Sparkling wine, including champagne, is made by adding further yeast to the wine when it is bottled. The carbon dioxide formed in this second fermentation is trapped as bubbles.
Yeasts are also used to produce kefir products, semi-soft ripened cheeses and fermented soy drinks. | 1 | Applied and Interdisciplinary Chemistry |
John A. Cranston, who had also come from Glasgow to Aberdeen with Soddy as a research assistant, was drafted in March 1915. Hitchins continued Cranston's research before she herself was drafted for war work in 1916. This research resulted in the successful identification of a new element in the decay chain between uranium-235 and actinium, later named protactinium. The discovery of protactinium completed the early version of the periodic table proposed by Dmitri Mendeleev, who predicted the existence of an element between thorium and uranium in 1871. The same isotope, Pa, was independently discovered around the same time by Otto Hahn and Lise Meitner.
Soddy and Cranston published their paper in 1918. Although Hitchins was not included as a co-author, Soddy gave Hitchins significant credit for the contributions she had made to the research: | 0 | Theoretical and Fundamental Chemistry |
A radioligand is a microscopic particle which consists of a therapeutic radioactive isotope and the cell-targeting compound - the ligand. The ligand is the target binding site, it may be on the surface of the targeted cancer cell for therapeutic purposes. Radioisotopes can occur naturally or be synthesized and produced in a cyclotron/nuclear reactor. The different types of radioisotopes include Y-90, H-3, C-11, Lu-177, Ac-225, Ra-223, In-111, I-131, I-125, etc. Thus, radioligands must be produced in special nuclear reactors for the radioisotope to remain stable. Radioligands can be used to analyze/characterize receptors, to perform binding assays, to help in diagnostic imaging, and to provide targeted cancer therapy. Radiation is a novel method of treating cancer and is effective in short distances along with being unique/personalizable and causing minimal harm to normal surrounding cells. Furthermore, radioligand binding can provide information about receptor-ligand interactions in vitro and in vivo. Choosing the right radioligand for the desired application is important. The radioligand must be radiochemically pure, stable, and demonstrate a high degree of selectivity, and high affinity for their target. | 1 | Applied and Interdisciplinary Chemistry |
In order to be functional, STAT5 proteins must first be activated. This activation is carried out by kinases associated with transmembrane receptors:
* Ligands binding to these transmembrane receptors on the outside of the cell activate the kinases;
* The stimulated kinases add a phosphate group to a specific tyrosine residue on the receptor;
* STAT5 then binds to these phosphorylated-tyrosines using their SH2 domain (STAT domains illustrated below);
* The bound STAT5 is then phosphorylated by the kinase, the phosphorylation occurring at particular tyrosine residues on the C-terminus of the protein;
* Phosphorylation causes STAT5 to dissociate from the receptor;
* The phosphorylated STAT5 finally goes on to form either homodimers, STAT5-STAT5, or heterodimers, STAT5-STATX, with other STAT proteins. The SH2 domains of the STAT5 proteins are once again used for this dimerization. STAT5 can also form homo-tetramers, usually in concert with the histone methyltransferase EZH2, and act as a transcriptional repressor.
In the activation pathway illustrated to the left, the ligand involved is a cytokine and the specific kinase taking part in activation is JAK. The dimerized STAT5 represents the active form of the protein, which is ready for translocation into the nucleus.
Once in the nucleus, the dimers bind to STAT5 response elements, inducing transcription of specific sets of genes. Upregulation of gene expression by STAT5 dimers has been observed for genes dealing with:
* Controlled cell growth and division, or cell proliferation
* Programmed cell death, or apoptosis
* Cell specialization, or differentiation and
* Inflammation.
Activated STAT5 dimers are, however, short-lived and the dimers are made to undergo rapid deactivation. Deactivation may be carried out by a direct pathway, removing the phosphate groups using phosphatases like PIAS or SHP-2 for example, or by an indirect pathway, which involves reducing cytokine signalling. | 1 | Applied and Interdisciplinary Chemistry |
Desorption, specifically thermal desorption, can be applied as an environmental remediation technique. This physical process is designed to remove contaminants at relatively low temperatures, ranging from 90 to 560 °C, from the solid matrix. The contaminated media is heated to volatilize water and organic contaminants, followed by treatment in a gas treatment system in which after removal, the contaminants are collected or thermally destroyed. They are transported using a carrier gas or vacuum to a vapor treatment system for removal/transformation into less toxic compounds.
Thermal desorption systems operate at a lower design temperature, which is sufficiently high to achieve adequate volatilization of organic contaminants. Temperatures and residence times are designed to volatilize selected contaminants but typically will not oxidize them. It is applicable at sites where high direct waste burial is present, and a short timeframe is necessary to allow for continued use or redevelopment of the site. | 0 | Theoretical and Fundamental Chemistry |
DNA fragmentation is the separation or breaking of DNA strands into pieces. It can be done intentionally by laboratory personnel or by cells, or can occur spontaneously. Spontaneous or accidental DNA fragmentation is fragmentation that gradually accumulates in a cell. It can be measured by e.g. the Comet assay or by the TUNEL assay.
Its main units of measurement is the DNA Fragmentation Index (DFI). A DFI of 20% or more significantly reduces the success rates after ICSI.
DNA fragmentation was first documented by Williamson in 1970 when he observed discrete oligomeric fragments occurring during cell death in primary neonatal liver cultures. He described the cytoplasmic DNA isolated from mouse liver cells after culture as characterized by DNA fragments with a molecular weight consisting of multiples of 135 kDa. This finding was consistent with the hypothesis that these DNA fragments were a specific degradation product of nuclear DNA. | 1 | Applied and Interdisciplinary Chemistry |
A widespread application of pneumatic motors is in hand-held tools, impact wrenches, pulse tools, screwdrivers, nut runners, drills, grinders, sanders and so on. Pneumatic motors are also used stationary in a wide range of industrial applications. Though overall energy efficiency of pneumatics tools is low and they require access to a compressed-air source, there are several advantages over electric tools. They offer greater power density (a smaller pneumatic motor can provide the same amount of power as a larger electric motor), do not require an auxiliary speed controller (adding to its compactness), generate less heat, and can be used in more volatile atmospheres as they do not require electric power and do not create sparks. They can be loaded to stop with full torque without damages. The efficiency of a rotary piston engine is highly dependent on mechanical energy losses. The value of mechanical losses, according to various estimates, can be 20% of the energy supplied to the engine. At the same time it was experimentally shown that efficiency of a motor can be increased by the usage of anti-friction additives to the lubricating oil.
Historically, many individuals have tried to apply pneumatic motors to the transportation industry. Guy Negre, CEO and founder of Zero Pollution Motors, has pioneered this field since the late 1980s. Recently Engineair has also developed a rotary motor for use in automobiles. Engineair places the motor immediately beside the wheel of the vehicle and uses no intermediate parts to transmit motion which means almost all of the motor's energy is used to rotate the wheel. | 1 | Applied and Interdisciplinary Chemistry |
It is known that the sub critical flow of a stratified fluid past a barrier produce motions upstream of the barrier. Sub critical flow may be defined as a flow for which the Froude number based on channel height is less than 1/π, so that one
or more stationary lee waves would be present. Some of the upstream motions do not decompose with the distance upstream. These ‘columnar’ modes have zero frequency and a sinusoidal structure in the direction of the density gradient; they effectively lead to a continuous change in upstream conditions. If the barrier is two-dimensional (i.e. of infinite extent in the direction perpendicular to the upstream flow and the direction of density gradient), inviscid theories show that the length of the upstream
region affected by the columnar modes increases without bound as t->infinity. Non-zero viscosity (and/or diffusivity) will, however, limit the region affected, since the wave amplitudes will then slowly decay. | 1 | Applied and Interdisciplinary Chemistry |
The gray (symbol: Gy) is the unit of ionizing radiation dose in the International System of Units (SI), defined as the absorption of one joule of radiation energy per kilogram of matter.
It is used as a unit of the radiation quantity absorbed dose that measures the energy deposited by ionizing radiation in a unit mass of absorbing material, and is used for measuring the delivered dose in radiotherapy, food irradiation and radiation sterilization. It is important in predicting likely acute health effects, such as acute radiation syndrome and is used to calculate equivalent dose using the sievert, which is a measure of the stochastic health effect on the human body.
The gray is also used in radiation metrology as a unit of the radiation quantity kerma; defined as the sum of the initial kinetic energies of all the charged particles liberated by uncharged ionizing radiation in a sample of matter per unit mass. The unit was named after British physicist Louis Harold Gray, a pioneer in the measurement of X-ray and radium radiation and their effects on living tissue.
The gray was adopted as part of the International System of Units in 1975. The corresponding cgs unit to the gray is the rad (equivalent to 0.01 Gy), which remains common largely in the United States, though "strongly discouraged" in the style guide for U.S. National Institute of Standards and Technology. | 0 | Theoretical and Fundamental Chemistry |
Wagner's gene network model is a computational model of artificial gene networks, which explicitly modeled the developmental and evolutionary process of genetic regulatory networks. A population with multiple organisms can be created and evolved from generation to generation. It was first developed by Andreas Wagner in 1996 and has been investigated by other groups to study the evolution of gene networks, gene expression, robustness, plasticity and epistasis. | 1 | Applied and Interdisciplinary Chemistry |
Diffusion is part of the transport phenomena. Of mass transport mechanisms, molecular diffusion is known as a slower one. | 1 | Applied and Interdisciplinary Chemistry |
The first example of an inverted ligand field was demonstrated in paper form 1995 by James Snyder. In this theoretical paper, Snyder proposed that the [Cu(CF)] complexes reported by Naumann et al. and assigned a formal oxidation state of 3+ at the copper would be better thought of as Cu(I). By comparing the d-orbital occupation, calculated charges and orbital population of [Cu(CF)] "Cu(III)" complex and the formally Cu(I) [Cu(CH)] complex, they illustrated how the former could be better described as a d10 copper complex experiencing two electron donation from the CF ligands. The phenomenon, termed an inverted ligand field by Roald Hoffman, began to be described by Aullón and Alvarez as they identified this phenonmenon as being a result of relative electronegativities. Lancaster and co-workers later provided experimental evidence to support the assignment of this oxidation state. Using UV/visible/near IR spectroscopy, Cu K-edge X-ray absorption spectroscopy, and 1s2p resonant inelastic X-ray scattering in concert with density functional theory, multiplet theory, and multireference calculations, they were able to map the ground state electronic configuration. This showed that the lowest unoccupied orbital was of primarily trifluoromethyl character. This confirmed the presence of an inverted ligand field and started building experimental tools to probe this phenomenon. Since the Snyder case, many other complexes of later transition metals have been shown to display inverted ligand field through both theoretical and experimental methods. | 0 | Theoretical and Fundamental Chemistry |
Sepro supplies horizontal slurry pumps, vertical sump pumps, vertical froth pumps, vertical tank pumps and horizontal fluid process pump models which are metal lined or rubber lined, one option being SH46® material for advanced wear resistance. They are designed to operate in the mining, aggregate, chemical and industrial sectors. Applications suitable for Sepro Pumps include mill discharge, mineral concentrate, dense media, coarse / fine tailings, process water and aggregates. Sepro engineers mobile, modular and fixed mineral processing plant designs which incorporate the complete line of slurry, sump, froth, tank and fluid Sepro Pumps. | 1 | Applied and Interdisciplinary Chemistry |
Dextromethorphan was once thought to cause Olney's lesions when administered intravenously; however, this was later proven inconclusive, due to lack of research on humans. Tests were performed on rats, giving them 50 mg or more every day for as long as a month. Neurotoxic changes, including vacuolation, have been observed in posterior cingulate and retrosplenial cortices of rats administered other NMDA receptor antagonists such as PCP, but not with dextromethorphan. | 0 | Theoretical and Fundamental Chemistry |
Aqueous normal-phase chromatography (ANP) is a chromatographic technique that involves the mobile phase compositions and polarities between reversed-phase chromatography (RP) and normal-phase chromatography (NP), while the stationary phases are polar. | 0 | Theoretical and Fundamental Chemistry |
High precision iron isotope measurements are obtained either via thermal ionization mass spectrometry (TIMS) or multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). | 0 | Theoretical and Fundamental Chemistry |
Preparation of the trifluoromethyltrimethylsilane was reported by Ingo Ruppert in 1984. In 1989, Prakash and Olah first reported activation of TMSCF by fluoride to perform nucleophilic trifluoromethylation of carbonyl compounds. In the same year, Stahly described similar reactions for the synthesis of trifluoromethylated phenols and anilines. Since then TMSCF has been widely used as a nucleophilic trifluoromethylating agent.
An example is the trifluoromethylation of cyclohexanone in THF using tetrabutylammonium fluoride.
The substrates can be aryl halides. Potassium (trifluoromethyl)trimethoxyborate for this purpose has been synthesised from B(OMe), CFSiMe and KF. Aryl functionalization by C-H activation has also been reported. | 0 | Theoretical and Fundamental Chemistry |
Exposure to radioactive waste may cause health impacts due to ionizing radiation exposure. In humans, a dose of 1 sievert carries a 5.5% risk of developing cancer, and regulatory agencies assume the risk is linearly proportional to dose even for low doses. Ionizing radiation can cause deletions in chromosomes. If a developing organism such as a fetus is irradiated, it is possible a birth defect may be induced, but it is unlikely this defect will be in a gamete or a gamete-forming cell. The incidence of radiation-induced mutations in humans is small, as in most mammals, because of natural cellular-repair mechanisms, many just now coming to light. These mechanisms range from DNA, mRNA and protein repair, to internal lysosomic digestion of defective proteins, and even induced cell suicide—apoptosis
Depending on the decay mode and the pharmacokinetics of an element (how the body processes it and how quickly), the threat due to exposure to a given activity of a radioisotope will differ. For instance, iodine-131 is a short-lived beta and gamma emitter, but because it concentrates in the thyroid gland, it is more able to cause injury than caesium-137 which, being water soluble, is rapidly excreted through urine. In a similar way, the alpha emitting actinides and radium are considered very harmful as they tend to have long biological half-lives and their radiation has a high relative biological effectiveness, making it far more damaging to tissues per amount of energy deposited. Because of such differences, the rules determining biological injury differ widely according to the radioisotope, time of exposure, and sometimes also the nature of the chemical compound which contains the radioisotope. | 0 | Theoretical and Fundamental Chemistry |
In electron spectroscopy, depending on the technique, irradiating the sample with high-energy particles such as X-ray photons, electron beam electrons, or ultraviolet radiation photons, causes Auger electrons and photoelectrons to be emitted. Figure 1 illustrates this on the basis of a single particle in which, for example, the incoming X-ray photon from a particular energy range (E=hν) transfers its energy to an electron in the inner shell of an atom. Photon absorption caused electron emission leaves a hole in the atomic shell (see figure 1 (a)). The hole can be filled in two ways, forming different characteristic rays that are specific to each element. As the electron in the shell of a higher energy level fills the hole, a fluorescent photon is emitted (figure 1 (b)). In the Auger phenomenon, the electron in the shell of the higher energy level fills the hole that causes the adjacent or nearby electron to emit, forming the Auger electron (figure 1 (c)).
As can be seen from discussed above and figure 1, Auger electrons and photoelectrons are different in their physical origin, however, both types of electrons carry similar information about the chemical elements in material surfaces. Each element has its own special Auger electron or photon electron energy from which these can be identified. The binding energy of a photoelectron can be calculated by the formula below.
where E is the binding energy of the photoelectron, hν is the energy of the incoming radiation particle, E is the kinetic energy of the photoelectron measured by the device and is the work function.
The kinetic energy of the Auger electron is approximately equal to the energy difference between the binding energies of the electron shells involved in the Auger process. This can be calculated as follows:
where E is the kinetic energy of the Auger electron, hν is the energy of the incoming radiation particle and E is first outer shell binding energy and E is second outer shell binding energies. | 0 | Theoretical and Fundamental Chemistry |
Wastewater produced by mining industries contribute to the acidity, suspended material and dissolved heavy metal ions in the aquatic environment, causing environmental problems for biological life and discoloration of the receiving waters. The application of settling basins by the Coeur d'Alene mining district of northern Idaho, United States, globally known to produce lead, zinc and silver, to treat wastewater has greatly improved the quality of water discharge from mining operations. | 1 | Applied and Interdisciplinary Chemistry |
Image formation is a plotting method that produces a color mapping through changing the x–y position of the tip while scanning and recording the measured variable, i.e. the intensity of control signal, to each x–y coordinate. The color mapping shows the measured value corresponding to each coordinate. The image expresses the intensity of a value as a hue. Usually, the correspondence between the intensity of a value and a hue is shown as a color scale in the explanatory notes accompanying the image.
Operation mode of image forming of the AFM are generally classified into two groups from the viewpoint whether it uses z-Feedback loop (not shown) to maintain the tip-sample distance to keep signal intensity exported by the detector. The first one (using z-Feedback loop), said to be "constant XX mode" (XX is something which kept by z-Feedback loop).
Topographic image formation mode is based on abovementioned "constant XX mode", z-Feedback loop controls the relative distance between the probe and the sample through outputting control signals to keep constant one of frequency, vibration and phase which typically corresponds to the motion of cantilever (for instance, voltage is applied to the Z-piezoelectric element and it moves the sample up and down towards the Z direction. | 0 | Theoretical and Fundamental Chemistry |
Cavicularin is a natural phenolic secondary metabolite isolated from the liverwort Cavicularia densa. This macrocycle is unusual because it was the first compound isolated from nature displaying optical activity solely due to the presence of planar chirality and axial chirality. The specific rotation for (+)-cavicularin is +168.2°. It is also a very strained molecule. The para-substituted phenol ring is bent about 15° out of planarity, adopting a somewhat boat-like geometry. This type of angle strain in aromatic compounds is normally reserved for synthetic cyclophanes.
The liverwort was obtained from Mount Ishizuchi in the district of Shikoku. The material was dried for one day, ground to a powder and 5 grams were refluxed in methanol for 4 months to yield 2.5 mg (0.049%) of cavicularin after column chromatography and preparative TLC. | 0 | Theoretical and Fundamental Chemistry |
Many organic compounds—two examples are ethanol and insulin—are manufactured industrially using organisms such as bacteria and yeast. Typically, the DNA of an organism is altered to express compounds not ordinarily produced by the organism. Many such biotechnology-engineered compounds did not previously exist in nature. | 0 | Theoretical and Fundamental Chemistry |
A stinger line is similar to a flow line, but unlike a flow line is not used to maintain circulation. The stinger line is attached to the blowout preventer to allow for the pressure from a blowout to be released. The stinger line usually will run parallel to the flow line. | 1 | Applied and Interdisciplinary Chemistry |
In many photo-productive systems this charge separation is kinetically isolated by delivery of the electron to a lower energy conductor attached to the p/n junction or into an electron transport chain. In this case some of the energy can be captured to do work. If the electron is not kinetically isolated thermodynamics will take over and the products will react with each other to regenerate the ground state starting material. This process is called recombination and the photon's energy is released as heat.
:Recombination of photoinduced oxidation
:[ML] + donor → [ML] + donor | 0 | Theoretical and Fundamental Chemistry |
Sarfati is a chess FIDE Master, and achieved a draw against former world champion Boris Spassky during a tournament in Wellington in 1988, and was New Zealand's national chess champion in 1987–88.
Although tied with Rey Casse for first place in the Australian Junior Championship of 1981, he was not eligible to share the title as he was a resident of New Zealand at the time. He represented New Zealand in three Chess Olympiads: the 27th in Dubai in 1986, the 28th in Thessaloniki in 1988, and the 30th in Manila in 1992. He also represented New Zealand on top board at the 5th Asian Teams in New Delhi.
He has given blindfold chess exhibitions at chess clubs and other events, and has played twelve such games simultaneously. His previous best was winning 11/11 at the Kāpiti Chess Club in New Zealand. | 0 | Theoretical and Fundamental Chemistry |
As the most prevalent morphology of nanomaterials used in consumer products, nanoparticles have an enormous range of potential and actual applications. Table below summarizes the most common nanoparticles used in various product types available on the global markets.
Scientific research on nanoparticles is intense as they have many potential applications in pre-clinical and clinical medicine, physics, optics, and electronics. The U.S. National Nanotechnology Initiative offers government funding focused on nanoparticle research. The use of nanoparticles in laser dye-doped poly(methyl methacrylate) (PMMA) laser gain media was demonstrated in 2003 and it has been shown to improve conversion efficiencies and to decrease laser beam divergence. Researchers attribute the reduction in beam divergence to improved dn/dT characteristics of the organic-inorganic dye-doped nanocomposite. The optimum composition reported by these researchers is 30% w/w of SiO (~ 12 nm) in dye-doped PMMA. Nanoparticles are being investigated as potential drug delivery system. Drugs, growth factors or other biomolecules can be conjugated to nano particles to aid targeted delivery. This nanoparticle-assisted delivery allows for spatial and temporal controls of the loaded drugs to achieve the most desirable biological outcome. Nanoparticles are also studied for possible applications as dietary supplements for delivery of biologically active substances, for example mineral elements. | 0 | Theoretical and Fundamental Chemistry |
Cytochrome c is widely believed to be localised solely in the mitochondrial intermembrane space under normal physiological conditions. The release of cytochrome c from mitochondria to the cytosol, where it activates the caspase family of proteases, is believed to be the primary trigger leading to the onset of apoptosis. Measuring the amount of cytochrome c leaking from mitochondria to cytosol, and out of the cell to culture medium, is a sensitive method to monitor the degree of apoptosis. However, detailed immuno-electronmicroscopic studies with rat tissues sections employing cytochrome c specific antibodies provide compelling evidence that cytochrome c under normal cellular conditions is also present at extramitochondrial locations. In pancreatic acinar cells and the anterior pituitary, strong and specific presence of cytochrome c was detected in zymogen granules and in growth hormone granules, respectively. In the pancreas, cytochrome c was also found in condensing vacuoles and in the acinar lumen. The extramitochondrial localisation of cytochrome c was shown to be specific as it was completely abolished upon adsorption of the primary antibody with purified cytochrome c. Besides cytochrome c, extramitochondrial localisation has also been observed for large numbers of other proteins including those encoded by mitochondrial DNA. This raises the possibility of the existence of yet-unidentified specific mechanisms for protein translocation from mitochondria to other cellular destinations. | 1 | Applied and Interdisciplinary Chemistry |
In binary compounds the more electropositive element is placed first in the formula. The formal list is used. The name of the most electronegative element is modified to end in -ide and the more electropositive elements name is left unchanged.
Taking the binary compound of sodium and chlorine: chlorine is found first in the list so therefore comes last in the name. Other examples are
* PCl phosphorus pentachloride
* CaP dicalcium triphosphide
* NiSn nickel stannide
* CrC tricosachromium hexacarbide | 0 | Theoretical and Fundamental Chemistry |
Silicon carbide was the first commercially important semiconductor material. A crystal radio "carborundum" (synthetic silicon carbide) detector diode was patented by Henry Harrison Chase Dunwoody in 1906. It found much early use in shipboard receivers. | 1 | Applied and Interdisciplinary Chemistry |
This technique is also used for detection of illicit drugs in various samples. The most common method of drug detection has been an immunoassay. This method is much more convenient. However, convenience comes at the cost of specificity and coverage of a wide range of drugs, therefore, HPLC has been used as well as an alternative method. As HPLC is a method of determining (and possibly increasing) purity, using HPLC alone in evaluating concentrations of drugs was somewhat insufficient. Therefore, HPLC in this context is often performed in conjunction with mass spectrometry. Using liquid chromatography-mass spectrometry (LC-MS) instead of gas chromatography-mass spectrometry (GC-MS) circumvents the necessity for derivitizing with acetylating or alkylation agents, which can be a burdensome extra step. LC-MS has been used to detect a variety of agents like doping agents, drug metabolites, glucuronide conjugates, amphetamines, opioids, cocaine, BZDs, ketamine, LSD, cannabis, and pesticides. Performing HPLC in conjunction with mass spectrometry reduces the absolute need for standardizing HPLC experimental runs. | 0 | Theoretical and Fundamental Chemistry |
Interspecies hydrogen transfer (IHT) is a form of interspecies electron transfer. It is a syntrophic process by which H is transferred from one organism to another, particularly in the rumen and other anaerobic environments.
IHT was discovered between Methanobacterium bryantii strain M.o.H and an "S" organism in 1967 by Marvin Bryant, Eileen Wolin, Meyer Wolin, and Ralph Wolfe at the University of Illinois. The two form a culture that was mistaken as a species Methanobacillus omelianskii. It was shown in 1973 that this process occurs between Ruminococcus albus and Wolinella succinogenes. A more recent publication describes how the gene expression profiles of these organisms changes when they undergo interspecies hydrogen transfer; of note, a switch to an electron-confurcating hydrogenase occurs in R. albus 7.
This process affects the carbon cycle: methanogens can participate in interspecies hydrogen transfer combining H and CO to produce CH. Besides methanogens, acetogens, and sulfate-reducing bacteria can participate in IHT. | 1 | Applied and Interdisciplinary Chemistry |
Lacking any other plausible explanation, the anomalous excess heat produced during such electrolysis was attributed by Pons and Fleischmann to cold fusion. Later, it was discovered that such excess heat can easily be the product of conventional chemistry, i.e. internal recombination of hydrogen and oxygen. Such recombination leads to a reduction in the Faraday efficiency of the electrolysis. The Faraday-efficiency effect is the observation of anomalous excess heat due to a reduction in the Faraday efficiency. | 0 | Theoretical and Fundamental Chemistry |
Many compounds exhibit polymorphism. It has been claimed that "every compound has different polymorphic forms, and that, in general, the number of forms known for a given compound is proportional to the time and money spent in research on that compound." | 0 | Theoretical and Fundamental Chemistry |
The NSEC contains only multiple choice questions. The questions include physical chemistry, organic chemistry, and inorganic chemistry. The stress on biochemistry is more in the NSEC than in the typical school syllabi. | 1 | Applied and Interdisciplinary Chemistry |
In chemistry, a polyoxometalate (abbreviated POM) is a polyatomic ion, usually an anion, that consists of three or more transition metal oxyanions linked together by shared oxygen atoms to form closed 3-dimensional frameworks. The metal atoms are usually group 6 (Mo, W) or less commonly group 5 (V, Nb, Ta) and group 7 (Tc , Re) transition metals in their high oxidation states. Polyoxometalates are often colorless, orange or red diamagnetic anions. Two broad families are recognized, isopolymetalates, composed of only one kind of metal and oxide, and heteropolymetalates, composed of one or more metals, oxide, and eventually a main group oxyanion (phosphate, silicate, etc.). Many exceptions to these general statements exist. | 0 | Theoretical and Fundamental Chemistry |
Photochromic units have been employed extensively in supramolecular chemistry. Their ability to give a light-controlled reversible shape change means that they can be used to make or break molecular recognition motifs, or to cause a consequent shape change in their surroundings. Thus, photochromic units have been demonstrated as components of molecular switches. The coupling of photochromic units to enzymes or enzyme cofactors even provides the ability to reversibly turn enzymes "on" and "off", by altering their shape or orientation in such a way that their functions are either "working" or "broken". | 0 | Theoretical and Fundamental Chemistry |
Reactive compatibilization is the process of modifying a mixed immiscible blend of polymers to arrest phase separation and allow for the formation of a stable, long-term continuous phase. It is done via the addition of a reactive polymer, miscible with one blend component and reactive towards functional groups on the second component, which result in the "in-situ" formation of block or grafted copolymers.
A large number of commercial polymeric products are derived from the blending of two or more polymers to achieve a favorable balance of physical properties. However, since most polymer blends are immiscible, it is rare to find a pair of polymers that both are miscible and have desired characteristics. An example of such pair is the miscible resin NORYL™, a mix of poly(phenylene oxide) and polystyrene. Immiscible blends will phase separate and form a dispersed phase, which may improve physical properties (figure 1). DuPont’s rubber toughened Nylon consists of small particles of poly(cis-isoprene) (natural rubber) in a Nylon matrix that toughen the material by arresting crack propagation. | 0 | Theoretical and Fundamental Chemistry |
Fermionic condensates are attained at lower temperatures than Bose–Einstein condensates. Fermionic condensates are a type of superfluid. As the name suggests, a superfluid possesses fluid properties similar to those possessed by ordinary liquids and gases, such as the lack of a definite shape and the ability to flow in response to applied forces. However, superfluids possess some properties that do not appear in ordinary matter. For instance, they can flow at high velocities without dissipating any energy—i.e. zero viscosity. At lower velocities, energy is dissipated by the formation of quantized vortices, which act as "holes" in the medium where superfluidity breaks down. Superfluidity was originally discovered in liquid helium-4 whose atoms are bosons, not fermions. | 0 | Theoretical and Fundamental Chemistry |
Meteorin-like/Meteorin-Beta (Metrnl)/IL-41, also known as subfatin and cometin, is a small (~27kDa) secreted cytokine, protein encoded by a gene called meteorin-like (METRNL). METRNL is highly expressed in mucosal tissues, skin and activated macrophages.
Metrnl has also been described to be a hormone
A screen of human skin-associated diseases showed significant over-expression of METRNL in psoriasis, prurigo nodularis, actinic keratosis and atopic dermatitis. METRNL is also up-regulated in synovial membranes of human rheumatoid arthritis.
Adipocyte Metrnl antagonizes obesity-induced insulin resistance by improving adipose function, including adipocyte differentiation, metabolism activation, and inflammation inhibition Lower serum levels of Metrnl might be a risk factor for developing coronary artery disease and type 2 diabetes mellitus | 1 | Applied and Interdisciplinary Chemistry |
A selector gene can be used to distinguish successfully genetically modified cells from unmodified ones. The selector gene is integrated into the plasmid along with the desired target gene, providing the cells with resistance to an antibiotic, such as kanamycin, ampicillin, spectinomycin or tetracycline. The desired cells, along with any other organisms growing within the culture, can be treated with an antibiotic, allowing only the modified cells to survive. The antibiotic gene is not usually transferred to the plant cell but instead remains within the bacterial cell. | 1 | Applied and Interdisciplinary Chemistry |
Transparent conducting electrodes are essential components of solar cells. It is either a continuous film of indium tin oxide or a conducting wire network, in which wires are charge collectors while voids between wires are transparent for light. An optimum density of wire network is essential for the maximum solar cell performance as higher wire density blocks the light transmittance while lower wire density leads to high recombination losses due to more distance traveled by the charge carriers. | 0 | Theoretical and Fundamental Chemistry |
T can be quantified (relaxometry) by curve fitting the signal expression above as a function of the duration of the spin-lock pulse while the amplitude of spin-lock pulse (γB~0.1-few kHz) is fixed. Quantitative T MRI relaxation maps reflect the biochemical composition of tissues. | 0 | Theoretical and Fundamental Chemistry |
Pioneering structural studies in the 1980s by Aaron Klug's group provided the first evidence that an octamer of histone proteins wraps DNA around itself in about 1.7 turns of a left-handed superhelix. In 1997 the first near atomic resolution crystal structure of the nucleosome was solved by the Richmond group, showing the most important details of the particle. The human alpha satellite palindromic DNA critical to achieving the 1997 nucleosome crystal structure was developed by the Bunick group at Oak Ridge National Laboratory in Tennessee. The structures of over 20 different nucleosome core particles have been solved to date, including those containing histone variants and histones from different species. The structure of the nucleosome core particle is remarkably conserved, and even a change of over 100 residues between frog and yeast histones results in electron density maps with an overall root mean square deviation of only 1.6Å. | 1 | Applied and Interdisciplinary Chemistry |
The effects of a particular signal transduction pathway can be very different among distinct cell types. For example, the same signal transduction pathway may promote the survival of one cell type but the maturation of another. This depends both on the nature of a cell but also on its particular state which may change over the course of its lifetime. Identifying cell types where a signal transduction pathway is operational is a first step to uncovering potentially new properties of this pathway.
The STAT3-Ser/Hes3 signaling axis has been shown to operate on various cell types. So far, research has mostly focused on stem cells and cancerous tissue and, more recently, in the function of the endocrine pancreas:
:* Fetal and adult mouse and rat neural stem cells.
:* Adult monkey (rhesus macaque) neural stem cells.
:* Human cancer stem cells from glioblastoma multiforme.
:* In a human prostate cancer cell line, STAT3-Ser was shown to promote tumorigenesis independently of STAT3-Tyr.
:* Chromaffin progenitor cells of the bovine adrenal medulla.
:* Mouse insulinoma cells (MIN6 cell line) and mouse pancreatic islet cells.
:* Mouse embryonic fibroblasts (MEF) during reprogramming to the induced pluripotent stem cell state.
:* Human embryonic stem cells
:* Mouse neural stem cells derived from induced pluripotent stem cells. | 1 | Applied and Interdisciplinary Chemistry |
UV curing (ultraviolet curing) is the process by which ultraviolet light initiates a photochemical reaction that generates a crosslinked network of polymers through radical polymerization or cationic polymerization. UV curing is adaptable to printing, coating, decorating, stereolithography, and in the assembly of a variety of products and materials. UV curing is a low-temperature, high speed, and solventless process as curing occurs via polymerization. Originally introduced in the 1960s, this technology has streamlined and increased automation in many industries in the manufacturing sector. | 0 | Theoretical and Fundamental Chemistry |
Recommended strategies to prevent mold include avoiding mold-contamination; utilization of environmental controls; the use of personal protective equipment (PPE), including skin and eye protection and respiratory protection; and environmental controls such as ventilation and suppression of dust. When mold cannot be prevented, the CDC recommends clean-up protocol including first taking emergency action to stop water intrusion. Second, they recommend determining the extent of water damage and mold contamination. And third, they recommend planning remediation activities such as establishing containment and protection for workers and occupants; eliminating water or moisture sources if possible; decontaminating or removing damaged materials and drying any wet materials; evaluating whether space has been successfully remediated; and reassembling the space to control sources of moisture. | 1 | Applied and Interdisciplinary Chemistry |
Obsidian hydration dating was introduced in 1960 by Irving Friedman and Robert Smith of the U.S. Geological Survey. Their initial work focused on obsidians from archaeological sites in western North America.
The use of Secondary ion mass spectrometry (SIMS) in the measurement of obsidian hydration dating was introduced by two independent research teams in 2002.
Today the technique is applied extensively by archaeologists to date prehistoric sites and sites from prehistory in California and the Great Basin of North America. It has also been applied in South America, the Middle East, the Pacific Islands, including New Zealand and Mediterranean Basin. | 0 | Theoretical and Fundamental Chemistry |
In canonical notch signaling, ligand proteins bind to the extracellular domain of the notch receptor and induce the cleavage and release of the intracellular domain into the cytoplasm. This subsequently interacts with other proteins, enters the nucleus, and regulates gene expression.
In 2006, a non-canonical branch of the notch signaling pathway was discovered. Using cultures of mouse neural stem cells, notch activation was shown to lead to the phosphorylation of several kinases (PI3K, Akt, mTOR) and subsequent phosphorylation of the serine residue of STAT3 in the absence of any detectable phosphorylation of the tyrosine residue of STAT3, a modification that is widely studied in the context of cancer biology. Following this event, Hes3 mRNA was elevated within 30 minutes. Subsequently, the consequences of this pathway were studied. | 1 | Applied and Interdisciplinary Chemistry |
The novel MEMS cantilever approach detects pressure changes in a photoacoustic cell. High sensitivity is achieved by using a cantilever pressure sensor that is over hundred times more sensitive compared to a membrane, which is conventionally used in photoacoustic spectroscopy. A laser-based readout interferometer is able to accurately measure displacement from well under a picometer up to millimeters. | 0 | Theoretical and Fundamental Chemistry |
At a certain voltage E, equilibrium will attain and the forward and backward rates (v and v) will be equal. This is represented by the green curve in the above figure. The equilibrium rate constants will be written as k and k, and the equilibrium concentrations will be written c and c. The equilibrium currents (j and j) will be equal and are written as j, which is known as the exchange current density.
Note that the net current density at equilibrium will be zero. The equilibrium rate constants are then:
Solving the above for k and k in terms of the equilibrium concentrations c and c and the exchange current density j, the current density j as a function of applied potential E may now be written:
Assuming that equilibrium holds in the bulk solution, with concentrations and , it follows that and , and the above expression for the current density j is then the Butler–Volmer equation. Note that E-E is also known as η, the activation overpotential. | 0 | Theoretical and Fundamental Chemistry |
In non-photosynthetic eukaryotes such as animals, insects, fungi, and protozoa, as well as the α-proteobacteria group of bacteria, the committed step for porphyrin biosynthesis is the formation of δ-aminolevulinic acid (δ-ALA, 5-ALA or dALA) by the reaction of the amino acid glycine with succinyl-CoA from the citric acid cycle. In plants, algae, bacteria (except for the α-proteobacteria group) and archaea, it is produced from glutamic acid via glutamyl-tRNA and glutamate-1-semialdehyde. The enzymes involved in this pathway are glutamyl-tRNA synthetase, glutamyl-tRNA reductase, and glutamate-1-semialdehyde 2,1-aminomutase. This pathway is known as the C5 or Beale pathway.
Two molecules of dALA are then combined by porphobilinogen synthase to give porphobilinogen (PBG), which contains a pyrrole ring. Four PBGs are then combined through deamination into hydroxymethyl bilane (HMB), which is hydrolysed to form the circular tetrapyrrole uroporphyrinogen III. This molecule undergoes a number of further modifications. Intermediates are used in different species to form particular substances, but, in humans, the main end-product protoporphyrin IX is combined with iron to form heme. Bile pigments are the breakdown products of heme.
The following scheme summarizes the biosynthesis of porphyrins, with references by EC number and the OMIM database. The porphyria associated with the deficiency of each enzyme is also shown: | 1 | Applied and Interdisciplinary Chemistry |
Ventilation Rate Procedure is rate based on standard and prescribes the rate at which ventilation air must be delivered to space and various means to the condition that air. Air quality is assessed (through CO measurement) and ventilation rates are mathematically derived using constants.
Indoor Air Quality Procedure uses one or more guidelines for the specification of acceptable concentrations of certain contaminants in indoor air but does not prescribe ventilation rates or air treatment methods. This addresses both quantitative and subjective evaluations and is based on the Ventilation Rate Procedure. It also accounts for potential contaminants that may have no measured limits, or for which no limits are not set (such as formaldehyde off-gassing from carpet and furniture). | 1 | Applied and Interdisciplinary Chemistry |
Needham's "silver age of Chinese alchemy" (c. 800-1300) was from the late Tang to the end of the Song dynasty. During the Tang, literature gradually changed from emphasizing ritual practices to cosmological principles. Early Taiqing tradition texts stress the performance of alchemical rites and ceremonies when compounding, and described elixirs as tools for either summoning benevolent gods or expelling malicious spirits. Most post-Tang texts related to alchemy stress the cosmological significance of elixir compounding and employ numerous abstract notions. After the late Tang period, gradually declined and the soteriological immortality significance of alchemy was transferred to .
Imperial interest in alchemy continued during the Song dynasty (960-1279). Emperor Zhenzong (r. 997-1022) established a laboratory in the Imperial Academy, where the Daoist alchemist Wang Jie "produced and presented to the throne artificial gold and silver amounting to many tens of thousands (of cash), brilliant and glittering beyond all ordinary treasures".
Most sources dating from the Song and later periods are either anthologies of earlier writings or deal with metallurgical techniques. alchemy subsequently declined in the Yuan, Ming, and Qing dynasties. | 1 | Applied and Interdisciplinary Chemistry |
In aqueous solution, boric acid can act as a weak Brønsted acid, that is, a proton donor, with pK ~ 9. However, it more often acts as a Lewis acid, accepting an electron pair from a hydroxyl ion produced by the water autoprotolysis:
: + 2 + (pK = 8.98)
This reaction is very fast, with characteristic time less than 10 μs. Polymeric boron oxoanions are formed in aqueous solution of boric acid at pH 7–10 if the boron concentration is higher than about 0.025 mol/L. The best known of these is the tetraborate ion , found in the mineral borax:
Other anions observed in solution are triborate(1−) and pentaborate(1−), in equilibrium with boric acid and tetrahydroxyborate according to the following overall reactions:
: 2 + + 3 (fast, pK = —1.92)
: 4 + + 6 (slow, pK = —2.05)
In the pH range 6.8 to 8.0, any alkali salts of "boric oxide" anions with general formula where 3x+q = 2y + z will eventually equilibrate in solution to a mixture of , , , and .
These ions, similarly to the complexed borates mentioned above, are more acidic than boric acid itself. As a result of this, the pH of a concentrated polyborate solution will increase more than expected when diluted with water. | 0 | Theoretical and Fundamental Chemistry |
The Boltzmann equation or Boltzmann transport equation (BTE) describes the statistical behaviour of a thermodynamic system not in a state of equilibrium; it was devised by Ludwig Boltzmann in 1872.
The classic example of such a system is a fluid with temperature gradients in space causing heat to flow from hotter regions to colder ones, by the random but biased transport of the particles making up that fluid. In the modern literature the term Boltzmann equation is often used in a more general sense, referring to any kinetic equation that describes the change of a macroscopic quantity in a thermodynamic system, such as energy, charge or particle number.
The equation arises not by analyzing the individual positions and momenta of each particle in the fluid but rather by considering a probability distribution for the position and momentum of a typical particle—that is, the probability that the particle occupies a given very small region of space (mathematically the volume element ) centered at the position , and has momentum nearly equal to a given momentum vector (thus occupying a very small region of momentum space ), at an instant of time.
The Boltzmann equation can be used to determine how physical quantities change, such as heat energy and momentum, when a fluid is in transport. One may also derive other properties characteristic to fluids such as viscosity, thermal conductivity, and electrical conductivity (by treating the charge carriers in a material as a gas). See also convection–diffusion equation.
The equation is a nonlinear integro-differential equation, and the unknown function in the equation is a probability density function in six-dimensional space of a particle position and momentum. The problem of existence and uniqueness of solutions is still not fully resolved, but some recent results are quite promising. | 1 | Applied and Interdisciplinary Chemistry |
Smelting and melting of copper and its alloys such as leaded bronze was done in crucibles similar to those of the Roman period which have thinner walls and flat bases to sit within the furnaces. The technology for this type of smelting started to change at the end of the Medieval period with the introduction of new tempering material for the ceramic crucibles. Some of these copper alloy crucibles were used in the making of bells. Bell foundry crucibles had to be larger at about 60 cm. These later medieval crucibles were a more mass-produced product.
The cementation process, which was lost from the end of the Roman to the early Medieval period, continued in the same way with brass. Brass production increased during the medieval period due to a better understanding of the technology behind it. Furthermore, the process for carrying out cementation for brass did not change greatly until the 19th century.
However, during this period a vast and highly important technological innovation happened using the cementation process, the production of crucible steel. Steel production using iron and carbon works similarly to brass, with the iron metal being mixed with carbon to produce steel. The first examples of cementation steel are wootz steel from India, where the crucibles were filled with good quality low-carbon wrought iron and carbon in the form of organics such as leaves, wood, etc. However, no charcoal was used within the crucible. These early crucibles would only produce a small amount of steel as they would have to be broken once the process has finished.
By the late Medieval period, steel production had moved from India to modern-day Uzbekistan where new materials were being used in the production of steel crucibles, for example, Mullite crucibles were introduced. These were sandy clay crucibles which had been formed around a fabric tube. These crucibles were used in the same way as other cementation vessels but with a hole in the top of the vessel to allow pressure to escape. | 0 | Theoretical and Fundamental Chemistry |
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