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Some nitrones oligimerize: Syntheses with nitrone precursors obviate the issue with increased temperature, to exaggerate entropic factors; or with a nitrone excess. | 0 | Theoretical and Fundamental Chemistry |
For a cylindrical tube, the Knudsen equation is:
where:
For nitrogen (or air) at room temperature, the conductivity (in liters per second) of a tube can be calculated from this equation: | 1 | Applied and Interdisciplinary Chemistry |
These thermocouples are well-suited for measuring extremely high temperatures. Typical uses are hydrogen and inert atmospheres, as well as vacuum furnaces. They are not used in oxidizing environments at high temperatures because of embrittlement. A typical range is 0 to 2315 °C, which can be extended to 2760 °C in inert atmosphere and to 3000 °C for brief measurements.
Pure tungsten at high temperatures undergoes recrystallization and becomes brittle. Therefore, types C and D are preferred over type G in some applications.
In presence of water vapor at high temperature, tungsten reacts to form tungsten(VI) oxide, which volatilizes away, and hydrogen. Hydrogen then reacts with tungsten oxide, after which water is formed again. Such a "water cycle" can lead to erosion of the thermocouple and eventual failure. In high temperature vacuum applications, it is therefore desirable to avoid the presence of traces of water.
An alternative to tungsten/rhenium is tungsten/molybdenum, but the voltage–temperature response is weaker and has minimum at around 1000 K.
The thermocouple temperature is limited also by other materials used. For example beryllium oxide, a popular material for high temperature applications, tends to gain conductivity with temperature; a particular configuration of sensor had the insulation resistance dropping from a megaohm at 1000 K to 200 ohms at 2200 K. At high temperatures, the materials undergo chemical reaction. At 2700 K beryllium oxide slightly reacts with tungsten, tungsten-rhenium alloy, and tantalum; at 2600 K molybdenum reacts with BeO, tungsten does not react. BeO begins melting at about 2820 K, magnesium oxide at about 3020 K. | 1 | Applied and Interdisciplinary Chemistry |
Water based pipe coatings, are an environmentally friendly coating that is applied to the inner & outer diameter of ductile iron pipe. They protect against corrosion from the outside and inside, and also protect the product from contamination. The coating is an emulsion manufactured using asphaltene and water primarily, with other raw materials according to the manufacturer's specifications.
They came in use in the early 1990s, replacing coatings based on dangerous and environmental harmful solvents, such as benzenes, toluenes, hexanes and other volatile organic compounds. | 1 | Applied and Interdisciplinary Chemistry |
In organometallic chemistry, a coordinatively unsaturated complex has fewer than 18 valence electrons and thus is susceptible to oxidative addition or coordination of an additional ligand. Unsaturation is characteristic of many catalysts. The opposite of coordinatively unsaturated is coordinatively saturated. Complexes that are coordinatively saturated rarely exhibit catalytic properties. | 0 | Theoretical and Fundamental Chemistry |
The repressor is an allosteric protein, i.e. it can assume either one of two slightly different shapes, which are in equilibrium with each other. In one form the repressor will bind to the operator DNA with high specificity, and in the other form it has lost its specificity. According to the classical model of induction, binding of the inducer, either allolactose or IPTG, to the repressor affects the distribution of repressor between the two shapes. Thus, repressor with inducer bound is stabilized in the non-DNA-binding conformation. However, this simple model cannot be the whole story, because repressor is bound quite stably to DNA, yet it is released rapidly by addition of inducer. Therefore, it seems clear that an inducer can also bind to the repressor when the repressor is already bound to DNA. It is still not entirely known what the exact mechanism of binding is. | 1 | Applied and Interdisciplinary Chemistry |
Sodium amide decomposes violently on contact with water, producing ammonia and sodium hydroxide:
When burned in oxygen, it will give oxides of sodium (which react with the produced water, giving sodium hydroxide) along with nitrogen oxides:
In the presence of limited quantities of air and moisture, such as in a poorly closed container, explosive mixtures of peroxides may form. This is accompanied by a yellowing or browning of the solid. As such, sodium amide is to be stored in a tightly closed container, under an atmosphere of an inert gas. Sodium amide samples which are yellow or brown in color represent explosion risks. | 0 | Theoretical and Fundamental Chemistry |
Solid state fermentation (SSF) is a biomolecule manufacturing process used in the food, pharmaceutical, cosmetic, fuel and textile industries. These biomolecules are mostly metabolites generated by microorganisms grown on a solid support selected for this purpose. This technology for the culture of microorganisms is an alternative to liquid or submerged fermentation, used predominantly for industrial purposes. | 1 | Applied and Interdisciplinary Chemistry |
Evamarie Hey-Hawkins is a German inorganic chemist and professor at Leipzig University. Her research is focused on main group and transition metal chemistry. | 0 | Theoretical and Fundamental Chemistry |
Acetone cyanohydrin, (CH)C(OH)CN is the cyanohydrin of acetone. It is generated as an intermediate in the industrial production of methyl methacrylate. In the laboratory, this liquid serves as a source of HCN, which is inconveniently volatile. Thus, acetone cyanohydrin can be used for the preparation of other cyanohydrins, for the transformation of HCN to Michael acceptors, and for the formylation of arenes. Treatment of this cyanohydrin with lithium hydride affords anhydrous lithium cyanide: | 0 | Theoretical and Fundamental Chemistry |
The mechanism of action of bottromycin was confirmed nearly 20 years following the discovery of bottromycin. Bottromycin functions as an antibiotic through inhibition of protein synthesis. It blocks aminoacyl tRNA binding to the ribosome by binding to the A site of the 50s subunit. This results in release of aminoacyl tRNA from the ribosome and premature termination of protein synthesis. A comparison of other antibiotics known to bind to the A site of the ribosome, including micrococcin, tetracycline, streptomycin, and chloramphenicol, suggested that only bottromycin and chloramphenicol caused release of aminoacyl tRNA from the ribosome. Of those antibiotics, only micrococcin is also a macrocyclic peptide. | 0 | Theoretical and Fundamental Chemistry |
Mitogen-activated protein kinase (MAPK) pathways can induce enzymes such as the COX-2 enzyme. MAPK pathways may also play a role in the regulation of PTGS2. | 1 | Applied and Interdisciplinary Chemistry |
He is known for the so-called Zinin reaction or Zinin reduction, in which nitro aromates like nitrobenzene are converted to amines by reduction with ammonium sulfides.
In 1842 Zinin played an important role in identifying aniline. | 0 | Theoretical and Fundamental Chemistry |
The surface energy of a liquid may be measured by stretching a liquid membrane (which increases the surface area and hence the surface energy). In that case, in order to increase the surface area of a mass of liquid by an amount, , a quantity of work, , is needed (where is the surface energy density of the liquid). However, such a method cannot be used to measure the surface energy of a solid because stretching of a solid membrane induces elastic energy in the bulk in addition to increasing the surface energy.
The surface energy of a solid is usually measured at high temperatures. At such temperatures the solid creeps and even though the surface area changes, the volume remains approximately constant. If is the surface energy density of a cylindrical rod of radius and length at high temperature and a constant uniaxial tension , then at equilibrium, the variation of the total Helmholtz free energy vanishes and we have
where is the Helmholtz free energy and is the surface area of the rod:
Also, since the volume () of the rod remains constant, the variation () of the volume is zero, that is,
Therefore, the surface energy density can be expressed as
The surface energy density of the solid can be computed by measuring , , and at equilibrium.
This method is valid only if the solid is isotropic, meaning the surface energy is the same for all crystallographic orientations. While this is only strictly true for amorphous solids (glass) and liquids, isotropy is a good approximation for many other materials. In particular, if the sample is polygranular (most metals) or made by powder sintering (most ceramics) this is a good approximation.
In the case of single-crystal materials, such as natural gemstones, anisotropy in the surface energy leads to faceting. The shape of the crystal (assuming equilibrium growth conditions) is related to the surface energy by the Wulff construction. The surface energy of the facets can thus be found to within a scaling constant by measuring the relative sizes of the facets. | 0 | Theoretical and Fundamental Chemistry |
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to electrons making a transition from a high energy state to a lower energy state. The photon energy of the emitted photons is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances. | 0 | Theoretical and Fundamental Chemistry |
A riboside is any glycoside of ribose. Ribosides in the form of ribonucleosides and ribonucleotides play an important role in biochemistry. | 1 | Applied and Interdisciplinary Chemistry |
In 1940, Ernst Chain and Edward Abraham reported the first indication of antibiotic resistance to penicillin, an E. coli strain that produced the penicillinase enzyme, which was capable of breaking down penicillin and negating its antibacterial effect. Chain and Abraham worked out the chemical nature of penicillinase which they reported in Nature as:
In his Nobel lecture, Fleming warned of the possibility of penicillin resistance in clinical conditions:
At the time, only poisons required a doctor's prescription, and self-treatment was a real possibility. Legislation was passed in the UK in 1947 to require a prescription for antibiotics. The United States followed in 1951. Elsewhere in the world, the export of Western pharmaceuticals diffused faster than Western medical knowledge and practices, and penicillin was often dispensed by practitioners of traditional medicine. As late as 1999, a study in the UK found that 39 per cent of respondents erroneously believed that antibiotics could cure colds and flu, and 12 per cent believed that they were the best treatment for them. The misplaced faith in antibiotics had serious consequences. It reduced the status of doctors to providers of pills. Many more people sought medical attention for ailments they would have ignored before, and they often demanded antibiotics. For their part, overworked doctors were increasingly willing to provide them even if not asked to do so.
By 1942, some strains of Staphylococcus aureus had developed a strong resistance to penicillin and many strains were resistant by the 1960s. In 1946, bacteriologist Mary Barber began a study of penicillin resistance through natural selection at Hammersmith Hospital in London. She found that in 1946, seven out of eight bacterial infections were susceptible to penicillin, but two years later only three out of eight were. Nurses were exposed to both bacteria and penicillin and harboured and transmitted bacterial infections. Miller found that three out of ten student midwives were colonized by bacteria when they arrived; after three months, seven out of ten were. The problem was sloppy hygiene practices by health care workers, poor medical practices like prophylactic use of antibiotics, and slipshod administrative practices, such as taking babies from their mothers to large hospital nurseries where they could infect each other.
Antibiotic-resistant infections were reported in Australia in 1952. During the 1957–1958 influenza pandemic there were 16,000 deaths in the UK and 80,000 in US from bacterial complications; 28 per cent of those who contracted pneumonia died. Most cases of pneumonia were contracted in hospitals, and many of these were antibiotic-resistant strains that had been nurtured there. In 1965, the first case of penicillin resistance in Streptococcus pneumoniae was reported from Boston. Since then other strains and species of bacteria have developed resistance. | 1 | Applied and Interdisciplinary Chemistry |
He spent his childhood in a small town in Transylvania, Chișineu-Criș, graduating from the local high school in 1966. He is nicknamed "Tanu". His mother died in 2019 while still living in Timisoara, Romania where he graduated from the university. Traian is married to Mika, who is from Japan, and they have a son, Sebastian. | 0 | Theoretical and Fundamental Chemistry |
For the special case of simple cubic crystals, the lattice vectors are orthogonal and of equal length (usually denoted a), as are those of the reciprocal lattice. Thus, in this common case, the Miller indices (hkℓ) and [hkℓ] both simply denote normals/directions in Cartesian coordinates.
For cubic crystals with lattice constant a, the spacing d between adjacent (hkℓ) lattice planes is (from above)
Because of the symmetry of cubic crystals, it is possible to change the place and sign of the integers and have equivalent directions and planes:
*Indices in angle brackets such as ⟨100⟩ denote a family of directions which are equivalent due to symmetry operations, such as [100], [010], [001] or the negative of any of those directions.
*Indices in curly brackets or braces such as {100} denote a family of plane normals which are equivalent due to symmetry operations, much the way angle brackets denote a family of directions.
For face-centered cubic and body-centered cubic lattices, the primitive lattice vectors are not orthogonal. However, in these cases the Miller indices are conventionally defined relative to the lattice vectors of the cubic supercell and hence are again simply the Cartesian directions. | 0 | Theoretical and Fundamental Chemistry |
Different rules (4n, 5n, or 6n) are invoked depending on the number of electrons per vertex.
The 4n rules are reasonably accurate in predicting the structures of clusters having about 4 electrons per vertex, as is the case for many boranes and carboranes. For such clusters, the structures are based on deltahedra, which are polyhedra in which every face is triangular. The 4n clusters are classified as closo-, nido-, arachno- or hypho-, based on whether they represent a complete (closo-) deltahedron, or a deltahedron that is missing one (nido-), two (arachno-) or three (hypho-) vertices.
However, hypho clusters are relatively uncommon due to the fact that the electron count is high enough to start to fill antibonding orbitals and destabilize the 4n structure. If the electron count is close to 5 electrons per vertex, the structure often changes to one governed by the 5n rules, which are based on 3-connected polyhedra.
As the electron count increases further, the structures of clusters with 5n electron counts become unstable, so the 6n rules can be implemented. The 6n clusters have structures that are based on rings.
A molecular orbital treatment can be used to rationalize the bonding of cluster compounds of the 4n, 5n, and 6n types. | 0 | Theoretical and Fundamental Chemistry |
Zinc refining is the process of purifying zinc to special high grade (SHG) zinc, which is at least 99.995% pure. This process is not usually required when smelting of zinc is done through electrolysis processes, but is needed when zinc is produced by pyrometallurgical processes, because it is only 98.5% pure.
There are various refining methods, but the refluxing process is the most commonly used.
High purity zinc is required industrially to avoid zinc pest, a slow distortion and cracking of zinc die castings caused by impurities precipitating out. | 1 | Applied and Interdisciplinary Chemistry |
Azo violet can be synthesised by reacting 4-nitroaniline with nitrous acid (generated in situ with an acid and a nitrite salt) to produce a diazonium intermediate. This is then reacted with resorcinol, dissolved in a sodium hydroxide solution, via an azo coupling reaction.
This is consistent with the generalized strategy for preparing azo dyes. | 0 | Theoretical and Fundamental Chemistry |
These are stoichiometric compounds of hydrogen. Ionic or saline hydrides are composed of hydride bound to an electropositive metal, generally an alkali metal or alkaline earth metal. The divalent lanthanides such as europium and ytterbium form compounds similar to those of heavier alkaline earth metals. In these materials the hydride is viewed as a pseudohalide. Saline hydrides are insoluble in conventional solvents, reflecting their non-molecular structures. Ionic hydrides are used as bases and, occasionally, as reducing reagents in organic synthesis.
Typical solvents for such reactions are ethers. Water and other protic solvents cannot serve as a medium for ionic hydrides because the hydride ion is a stronger base than hydroxide and most hydroxyl anions. Hydrogen gas is liberated in a typical acid-base reaction.
:ΔH = −83.6 kJ/mol, ΔG = −109.0 kJ/mol
Often alkali metal hydrides react with metal halides. Lithium aluminium hydride (often abbreviated as LAH) arises from reactions of lithium hydride with aluminium chloride. | 0 | Theoretical and Fundamental Chemistry |
The Ranch-style house is underground and has brick veneer siding but is enclosed in a waterproof concrete shell measuring approximately and covered with a compacted earth berm. The Clark County, Nevada Records show that the Underground House is on . The main house itself encompasses three bedrooms and three bathrooms, and includes a small guest quarters. The home, designed to sustain life for approximately one year, was equipped with an underground generator and fuel tank."
The interior design of this home serves as a reflection of the Cold War era during which it was constructed. The prevailing atmosphere at the time, particularly in the aftermath of the Cuban Missile Crisis, was one of heightened concern among Americans regarding the looming threat of nuclear war. The homeowner held a firm conviction that the United States and the Soviet Union might continue to intensify their conflict, ultimately leading to a catastrophic nuclear confrontation.
The underground area has been designed to imitate an above-ground setting, including grass-looking carpet as an imitation lawn, artificial trees and wall to wall, floor to ceiling scenery. A fireplace chimney channeled smoke through a "trunk and branches" of a fake tree on the surface. The house was lit with nearly 1,000 fluorescent lights. These lights, in four colors, enabled the night sky to simulate a sunrise.
The muralist Jewel Smith painted the Trompe-lœil murals to depict Hendersons sheep ranch in Cecil Peak Station, New Zealand, the ranch he owned in Colorado, a view of Los Angeles from Beverly Hills, and a depiction of his childhood home in Suffern, New York. | 0 | Theoretical and Fundamental Chemistry |
"In the years between 1770 and 1785, chemists all over Europe started catching, isolating, and weighing different gasses."
The pneumatic trough was integral to the work with gases (or, as contemporary chemists called them, airs). Work done by Joseph Black, Joseph Priestley, Herman Boerhaave, and Henry Cavendish revolved largely around the use of the instrument, allowing them to collect airs given off by different chemical reactions and combustion analyses. Their work led to the discovery of many types of airs, such as dephlogisticated air (discovered by Joseph Priestley).
Moreover, the chemistry of airs was not limited to combustion analyses. During the eighteenth century, many chymists used the discovery of airs as a new path for exploring old problems, with one example being the field of medicinal chemistry. One particular Englishman, James Watt, began to take the idea of airs and use them in what was referred to as pneumatic therapy, or the use of airs to make laboratories more workable with fresh airs and also aid patients with different illnesses, with varying degrees of success. Most human experimentation done was performed on the chymists themselves, as they believed that self-experimentation was a necessary part or progressing the field. | 1 | Applied and Interdisciplinary Chemistry |
The Beilstein database is a database in the field of organic chemistry, in which compounds are uniquely identified by their Beilstein Registry Number. The database covers the scientific literature from 1771 to the present and contains experimentally validated information on millions of chemical reactions and substances from original scientific publications. The electronic database was created from Handbuch der Organischen Chemie (Beilsteins Handbook of Organic Chemistry'), founded by Friedrich Konrad Beilstein in 1881, but has appeared online under a number of different names, including Crossfire Beilstein. Since 2009, the content has been maintained and distributed by Elsevier Information Systems in Frankfurt under the product name "Reaxys".
The database contains information on reactions, substances, structures and properties. Up to 350 fields containing chemical and physical data (such as melting point, refractive index etc.) are available for each substance. References to the literature in which the reaction or substance data appear are also given.
The Beilstein content made available through Reaxys is complemented by information drawn from Gmelin (which gives access to the Gmelin Database), a very large repository of organometallic and inorganic information, as well as by information drawn from the Patent Chemistry Database. The Reaxys registered trademark and the database itself are owned and protected by Elsevier Properties SA and used under license. | 0 | Theoretical and Fundamental Chemistry |
White etching cracks (WEC), or white structure flaking or brittle flaking, is a type of rolling contact fatigue (RCF) damage that can occur in bearing steels under certain conditions, such as hydrogen embrittlement, high stress, inadequate lubrication, and high temperature. WEC is characterised by the presence of white areas of microstructural alteration in the material, which can lead to the formation of small cracks that can grow and propagate over time, eventually leading to premature failure of the bearing. WEC has been observed in a variety of applications, including wind turbine gearboxes, automotive engines, and other heavy machinery. The exact mechanism of WEC formation is still a subject of research, but it is believed to be related to a combination of microstructural changes, such as phase transformations and grain boundary degradation, and cyclic loading. | 1 | Applied and Interdisciplinary Chemistry |
The Journal of Photochemistry and Photobiology is a series of peer-reviewed scientific journals covering the fields of photochemistry and photobiology, published by Elsevier. It was originally established in 1972, and split into Journal of Photochemistry and Photobiology A: Chemistry and Journal of Photochemistry and Photobiology B: Biology in 1987. A third title; Journal of Photochemistry and Photobiology C: Photochemistry Reviews, was established in 2000 and is the official journal of the Japanese Photochemistry Association. | 0 | Theoretical and Fundamental Chemistry |
When two lipid bilayers approach each other, they experience weak van der Waals attractive forces and much stronger repulsive forces due to hydration repulsion. These forces are normally dominant over the hydrophobic attractive forces between the membranes. Studies done on membrane bilayers using Surface forces apparatus (SFA) indicate that membrane fusion can instantaneously occur when two bilayers are still at a finite distance from each other without them having to overcome the short-range repulsive force barrier. This is attributed to the molecular rearrangements that occur resulting in the bypassing of these forces by the membranes. During fusion, the hydrophobic tails of a small patch of lipids on the cell membrane are exposed to the aqueous phase surrounding them. This results in very strong hydrophobic attractions (which dominate the repulsive force) between the exposed groups leading to membrane fusion. The attractive van der Waals forces play a negligible role in membrane fusion. Thus, fusion is a result of the hydrophobic attractions between internal hydrocarbon chain groups that are exposed to the normally inaccessible aqueous environment. Fusion is observed to start at points on the membranes where the membrane stresses are either the weakest or the strongest. | 0 | Theoretical and Fundamental Chemistry |
Non-essential nutrients are substances within foods that can have a significant impact on health. Dietary fiber is not absorbed in the human digestive tract. Soluble fiber is metabolized to butyrate and other short-chain fatty acids by bacteria residing in the large intestine. Soluble fiber is marketed as serving a prebiotic function with claims for promoting "healthy" intestinal bacteria. | 0 | Theoretical and Fundamental Chemistry |
Kullback gives the following example (Table 2.1, Example 2.1). Let and be the distributions shown in the table and figure. is the distribution on the left side of the figure, a binomial distribution with and . is the distribution on the right side of the figure, a discrete uniform distribution with the three possible outcomes , , (i.e. ), each with probability .
Relative entropies and are calculated as follows. This example uses the natural log with base E (mathematical constant)|, designated to get results in nats (see units of information): | 0 | Theoretical and Fundamental Chemistry |
Reverse cholesterol transport is a multi-step process resulting in the net movement of cholesterol from peripheral tissues back to the liver first via entering the lymphatic system, then the bloodstream.
Cholesterol from non-hepatic peripheral tissues is transferred to HDL by the ABCA1 (ATP-binding cassette transporter). Apolipoprotein A1 (ApoA-1), the major protein component of HDL, acts as an acceptor, and the phospholipid component of HDL acts as a sink for the mobilised cholesterol.
The cholesterol is converted to cholesteryl esters by the enzyme LCAT (lecithin-cholesterol acyltransferase).
The cholesteryl esters can be transferred, with the help of CETP (cholesterylester transfer protein) in exchange for triglycerides, to other lipoproteins (such as LDL and VLDL), and these lipoproteins can be taken up by secreting unesterified cholesterol into the bile or by converting cholesterol to bile acids.
Adiponectin induces ABCA1-mediated reverse cholesterol transport from macrophages by activation of PPAR-γ and LXRα/β.
Uptake of HDL is mediated by hepatic lipase, a special form of lipoprotein lipase found only in the liver. Hepatic lipase activity is increased by androgens and decreased by estrogens, which may account for higher concentrations of HDL in women.
Discoidal (Nascent) HDL:
Initially, HDL is discoidal in shape because it lacks esterified cholesterol but as it keeps accumulating free cholesterol in it, the enzyme LCAT keeps esterifying the free cholesterol.
When the HDL molecule is cholesterol rich, its shape is changed into more spherical and it becomes less dense (HDL 2). This is carried to the liver to release all the esterified cholesterol into the liver. | 1 | Applied and Interdisciplinary Chemistry |
When stormwater is passed through a filter media, solids and other pollutants are removed. Most media remove solids by mechanical processes. The gradation of the media, irregularity of shape, porosity, and surface roughness characteristics all influence solids removal. Many other pollutants such as nutrients and metals can be removed through chemical and/or biological processes. Filtration is a key component to LID sites, especially when infiltration is not feasible. Filter systems can be designed to remove the primary pollutants of concern from runoff and can be configured in decentralized small-scale inlets. This allows for runoff to be treated close to its source without additional collection or conveyance infrastructure. | 1 | Applied and Interdisciplinary Chemistry |
Tebbe's reagent is the organometallic compound with the formula (CH)TiCHClAl(CH). It is used in the methylidenation of carbonyl compounds, that is it converts organic compounds containing the RC=O group into the related RC=CH derivative. It is a red solid that is pyrophoric in the air, and thus is typically handled with air-free techniques. It was originally synthesized by Fred Tebbe at DuPont Central Research.
Tebbe's reagent contains two tetrahedral metal centers linked by a pair of bridging ligands. The titanium has two cyclopentadienyl (, or Cp) rings and aluminium has two methyl groups. The titanium and aluminium atoms are linked together by both a methylene bridge (-CH-) and a chloride atom in a nearly square-planar (Ti–CH–Al–Cl) geometry. The Tebbe reagent was the first reported compound where a methylene bridge connects a transition metal (Ti) and a main group metal (Al). | 0 | Theoretical and Fundamental Chemistry |
The production of ferronickel from laterites takes place in a context that is much more favorable to the Krupp-Renn process than to the steel industry. Lateritic ores in the form of saprolite are poor, very basic and contain iron. Production volumes are moderate, and the nickel chemistry is remarkably amenable to rotary kiln reduction. The process is therefore attractive, but regardless of the metal extracted, mastering all the physical and chemical transformations in a single reactor is a real challenge. The failure of the Larco plant at Lárymna, Greece, illustrates the risk involved in adopting this process: it was only when the ore was ready for industrial processing that it proved incompatible with the Krupp-Renn process.
As a result, lower-temperature reduction followed by electric furnace smelting allows each stage to have its own dedicated tool for greater simplicity and efficiency. Developed in 1950 at the in New Caledonia, this combination has proven to be both cost-effective and, above all, more robust. Large rotating drums (5 m in diameter and 100 m or even 185 m long) are used to produce a dry powder from nickel ore concentrate. This powder contains 1.5 to 3% nickel. It leaves the drum at 800–900 °C and is immediately melted in electric furnaces. Only partial reduction takes place in the drums: a quarter of the nickel comes out in metallic form, the rest is still oxidized. Only 5% of the iron is reduced to metal, leaving unburned coal as fuel for the subsequent melting stage in the electric furnace. This proven process (also known as the RKEF process, for Rotary Kiln-Electric Furnace) has become the norm: at the beginning of the 21st century, it accounted for almost all nickel laterite processing.
In the early 21st century, however, the Nihon Yakin Kogyo foundry in Ōeyama, Japan, continued to use the Krupp-Renn process to produce intermediate grade ferronickel (23% nickel), sometimes called nickel pig iron. With a monthly output of 1,000 tons of Luppen and a production capacity of 13 kt/year, the plant is operating at full capacity. It is the only plant in the world using this process. It is also the only plant using a direct reduction process to extract nickel from laterite. The process, which has been significantly upgraded, is called the "Ōeyama process".
The Ōeyama process differs from the Krupp-Renn process in the use of limestone and the briquetting of the ore prior to charging. It retains its advantages, which are the concentration of all pyrometallurgical reactions in a single reactor and the use of standard (i.e. non-coking) coal, which covers 90% of the energy requirements of the process. Coal consumption is only 140 kg per ton of dry laterite, and the quality of the ferronickel obtained is compatible with direct use by the steel industry. Although marginal, the Krupp-Renn process remains a modern, high-capacity process for the production of nickel pig iron. In this context, it remains a systematically studied alternative to the RKEF process and the "sinter plant-blast furnace" combination. | 1 | Applied and Interdisciplinary Chemistry |
The earliest records of bloomery-type furnaces in East Africa are discoveries of smelted iron and carbon in Nubia n ancient Sudan dated at least to the seventh to the sixth century BC. The ancient bloomeries that produced metal tools for the Nubians and Kushites produced a surplus for sale. All traditional sub-Saharan African iron-smelting processes are variants of the bloomery process. There is considerable discussion about the origins of iron metallurgy in Africa. Smelting in bloomery type furnaces in West Africa and forging of tools appeared in the Nok culture of central Nigeria by at least 550 BC and possibly several centuries earlier. Also, evidence indicates iron smelting with bloomery-style furnaces dated to 750 BC in Opi (Augustin Holl 2009) and Lejja dated to 2,000 BC (Pamela Eze-Uzomaka 2009), both sites in the Nsukka region of southeast Nigeria in what is now Igboland. The site of Gbabiri, in the Central African Republic, has also yielded evidence of iron metallurgy, from a reduction furnace and blacksmith workshop, with earliest dates of 896–773 and 907–796 BC, respectively. | 1 | Applied and Interdisciplinary Chemistry |
The nitrogen-vacancy center (N-V center or NV center) is one of numerous photoluminescent point defects in diamond. Its most explored and useful properties include its spin-dependent photoluminescence (which enables measurement of the electronic spin state using optically detected magnetic resonance), and its relatively long (millisecond) spin coherence at room temperature. The NV center energy levels are modified by magnetic fields, electric fields, temperature, and strain, which allow it to serve as a sensor of a variety of physical phenomena. Its atomic size and spin properties can form the basis for useful quantum sensors. It has also been explored for applications in quantum computing (e.g. for entanglement generation) and spintronics. | 0 | Theoretical and Fundamental Chemistry |
The collision rates for fine particles (50 - 80 μm) can be accurately modeled, but there is no current theory that accurately models bubble-particle collision for particles as large as 300 μm, which are commonly used in flotation processes.
For fine particles, Stokes law underestimates collision probability while the potential equation based on surface charge overestimates collision probability so an intermediate equation is used.
It is important to know the collision rates in the system since this step precedes the adsorption where a three phase system is formed. | 1 | Applied and Interdisciplinary Chemistry |
Lysergic acid, also known as -lysergic acid and (+)-lysergic acid, is a precursor for a wide range of ergoline alkaloids that are produced by the ergot fungus and found in the seeds of Turbina corymbosa (ololiuhqui), Argyreia nervosa (Hawaiian baby woodrose), and Ipomoea tricolor (morning glories, tlitliltzin).
Amides of lysergic acid, lysergamides, are widely used as pharmaceuticals and as psychedelic drugs, e.g. lysergic acid diethylamide (LSD). Lysergic acid is listed as a Table I precursor under the United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.
Lysergic acid received its name as it was a product of the lysis of various ergot alkaloids. | 0 | Theoretical and Fundamental Chemistry |
The common feature of all these routine screening procedures is that the primary analysis is for indicator organisms rather than the pathogens that might cause concern. Indicator organisms are bacteria such as non-specific coliforms, Escherichia coli and Pseudomonas aeruginosa that are very commonly found in the human or animal gut and which, if detected, may suggest the presence of sewage. Indicator organisms are used because even when a person is infected with a more pathogenic bacteria, they will still be excreting many millions times more indicator organisms than pathogens. It is therefore reasonable to surmise that if indicator organism levels are low, then pathogen levels will be very much lower or absent. Judgements as to suitability of water for use are based on very extensive precedents and relate to the probability of any sample population of bacteria being able to be infective at a reasonable statistical level of confidence.
Analysis is usually performed using culture, biochemical and sometimes optical methods. When indicator organisms levels exceed pre-set triggers, specific analysis for pathogens may then be undertaken and these can be quickly detected (where suspected) using specific culture methods or molecular biology. | 0 | Theoretical and Fundamental Chemistry |
The level of the water is measured at a designated point behind weir or in flume using various secondary devices (bubblers, ultrasonic, float, and differential pressure are common methods). This depth is converted to a flow rate according to a theoretical formula of the form where is the flow rate, is a constant, is the water level, and is an exponent which varies with the device used; or it is converted according to empirically derived level/flow data points (a "flow curve"). The flow rate can then be integrated over time into volumetric flow. Level to flow devices are commonly used to measure the flow of surface waters (springs, streams, and rivers), industrial discharges, and sewage. Of these, weirs are used on flow streams with low solids (typically surface waters), while flumes are used on flows containing low or high solids contents. | 1 | Applied and Interdisciplinary Chemistry |
Vinyl sulfone has uses as a molluscicide pesticide.
Phenyl vinyl sulfone has been applied to ruthenium chemistry as part of olefin metathesis reactions.
Vinyl sulfone has applications to protein purification, especially when linked with mercaptoethanol. | 1 | Applied and Interdisciplinary Chemistry |
One modern-day method of chiral resolution is used in the organic synthesis of the drug duloxetine:
In one of its steps the racemic alcohol 1 is dissolved in a mixture of toluene and methanol to which solution is added optically active (S)-mandelic acid 3. The alcohol (S)-enantiomer forms an insoluble diastereomeric salt with the mandelic acid and can be filtered from the solution. Simple deprotonation with sodium hydroxide liberates free (S)-alcohol. In the meanwhile the (R)-alcohol remains in solution unaffected and is recycled back to the racemic mixture by epimerization with hydrochloric acid in toluene. This process is known as RRR synthesis in which the R's stand for Resolution-Racemization-Recycle. | 0 | Theoretical and Fundamental Chemistry |
The term anti-periplanar was first coined by Klyne and Prelog in their work entitled "Description of steric relationships across single bonds", published in 1960. ‘Anti’ refers to the two functional groups lying on opposite sides of the plane of the bond. ‘Peri’ comes from the Greek word for ‘near’ and so periplanar means “approximately planar”. In their article “Periplanar or Coplanar?” Kane and Hersh point out that many organic textbooks use anti-periplanar to mean completely anti-planar, or anti-coplanar, which is technically incorrect. | 0 | Theoretical and Fundamental Chemistry |
Mg is essential for plant growth and is present in higher plants in amounts on the order of 80 μmol g dry weight. The amounts of Mg vary in different parts of the plant and are dependent upon nutritional status. In times of plenty, excess Mg may be stored in vascular cells (Stelzer et al., 1990; and in times of starvation Mg is redistributed, in many plants, from older to newer leaves.
Mg is taken up into plants via the roots. Interactions with other cations in the rhizosphere can have a significant effect on the uptake of the ion.(Kurvits and Kirkby, 1980; The structure of root cell walls is highly permeable to water and ions, and hence ion uptake into root cells can occur anywhere from the root hairs to cells located almost in the centre of the root (limited only by the Casparian strip). Plant cell walls and membranes carry a great number of negative charges, and the interactions of cations with these charges is key to the uptake of cations by root cells allowing a local concentrating effect. Mg binds relatively weakly to these charges, and can be displaced by other cations, impeding uptake and causing deficiency in the plant.
Within individual plant cells, the Mg requirements are largely the same as for all cellular life; Mg is used to stabilise membranes, is vital to the utilisation of ATP, is extensively involved in the nucleic acid biochemistry, and is a cofactor for many enzymes (including the ribosome). Also, Mg is the coordinating ion in the chlorophyll molecule. It is the intracellular compartmentalisation of Mg in plant cells that leads to additional complexity. Four compartments within the plant cell have reported interactions with Mg. Initially, Mg will enter the cell into the cytoplasm (by an as yet unidentified system), but free Mg concentrations in this compartment are tightly regulated at relatively low levels (≈2 mmol/L) and so any excess Mg is either quickly exported or stored in the second intracellular compartment, the vacuole. The requirement for Mg in mitochondria has been demonstrated in yeast and it seems highly likely that the same will apply in plants. The chloroplasts also require significant amounts of internal Mg, and low concentrations of cytoplasmic Mg. In addition, it seems likely that the other subcellular organelles (e.g., Golgi, endoplasmic reticulum, etc.) also require Mg. | 1 | Applied and Interdisciplinary Chemistry |
RiPPs are characterized by a common biosynthetic strategy wherein genetically-encoded peptides undergo translation and subsequent chemical modification by biosynthetic enzymes. | 1 | Applied and Interdisciplinary Chemistry |
In the low- limit, as the system is probed over large length scales, the structure factor contains thermodynamic information, being related to the isothermal compressibility of the liquid by the compressibility equation: | 0 | Theoretical and Fundamental Chemistry |
In addition to temperature and pressure, other thermodynamic properties may be graphed in phase diagrams. Examples of such thermodynamic properties include specific volume, specific enthalpy, or specific entropy. For example, single-component graphs of temperature vs. specific entropy (T vs. s) for water/steam or for a refrigerant are commonly used to illustrate thermodynamic cycles such as a Carnot cycle, Rankine cycle, or vapor-compression refrigeration cycle.
Any two thermodynamic quantities may be shown on the horizontal and vertical axes of a two-dimensional diagram. Additional thermodynamic quantities may each be illustrated in increments as a series of lines – curved, straight, or a combination of curved and straight. Each of these iso-lines represents the thermodynamic quantity at a certain constant value. | 0 | Theoretical and Fundamental Chemistry |
The concept of chromosome territories was proposed by Carl Rabl in 1885 based on studies of Salamandra maculata.
Chromosome territories have gained recognition using fluorescence labeling techniques (fluorescence in situ hybridization).
Studies of genomic proximity using techniques like chromosome conformation capture have supported the chromosome territory concept by showing that DNA-DNA contacts predominantly happen within particular chromosomes. | 1 | Applied and Interdisciplinary Chemistry |
Over recent years, the genome-wide CRISPR screen has emerged as a powerful tool for studying the intricate networks of cellular signaling. Cellular signaling is essential for a number of fundamental biological processes, including cell growth, proliferation, differentiation, and apoptosis.
One practical example is the identification of genes required for proliferative signaling in cancer cells. Cells are transduced with a CRISPR sgRNA library, and studied for growth over time. By comparing sgRNA abundance in selected cells to a control, one can identify which sgRNAs become depleted and in turn which genes may be responsible for the proliferation defect. Such screens have been used to identify cancer-essential genes in acute myeloid leukemia and neuroblastoma, and to describe tumor-specific differences between cancer cell lines. | 1 | Applied and Interdisciplinary Chemistry |
Crystalline sponges are series of organometallic networks developed by Japanese chemist Makoto Fujita. The organic small molecules are absorbed into the void space of the crystalline sponges. Since the organometallic network of crystalline sponges can interact with the small molecule substrates via non-covalent interactions, the absorption can be selective. That is, the crystalline sponge can enrich certain molecules from a mixture.
As the crystal sponges are highly organized frameworks, the structure of the whole host-guest complex can be characterized by X-ray diffraction. Because the absorbate is encapsulated in a pre-organized environment, no single crystal of the substrate is needed in the X-ray diffraction. Besides, the X-ray crystallography of liquid samples can also be conducted. | 0 | Theoretical and Fundamental Chemistry |
An excimer lamp (or excilamp) is a source of ultraviolet light based on spontaneous emission of excimer (exciplex) molecules. | 0 | Theoretical and Fundamental Chemistry |
In heat transfer and thermodynamics, a thermodynamic system is said to be in thermal contact with another system if it can exchange energy through the process of heat. Perfect thermal isolation is an idealization as real systems are always in thermal contact with their environment to some extent.
When two solid bodies are in contact, a resistance to heat transfer exists between the bodies. The study of heat conduction between such bodies is called thermal contact conductance (or thermal contact resistance). | 0 | Theoretical and Fundamental Chemistry |
For an ideal Bose gas we have the equation of state
where is the per-particle volume, is the thermal wavelength, is the fugacity, and
It is noticeable that is a monotonically growing function of in , which are the only values for which the series converge.
Recognizing that the second term on the right-hand side contains the expression for the average occupation number of the fundamental state , the equation of state can be rewritten as
Because the left term on the second equation must always be positive, , and because , a stronger condition is
which defines a transition between a gas phase and a condensed phase. On the critical region it is possible to define a critical temperature and thermal wavelength:
recovering the value indicated on the previous section. The critical values are such that if or , we are in the presence of a Bose–Einstein condensate.
Understanding what happens with the fraction of particles on the fundamental level is crucial. As so, write the equation of state for , obtaining
: and equivalently
So, if , the fraction , and if , the fraction . At temperatures near to absolute 0, particles tend to condense in the fundamental state, which is the state with momentum . | 0 | Theoretical and Fundamental Chemistry |
He was an arbiter of culinary fashion and taste, who also "revolutionized the local cuisine" by introducing new fruit and vegetables such as asparagus, and by introducing the three-course meal served on leathern tablecloths, insisting that meals should be served in three separate courses consisting of soup, the main course, and dessert. He also introduced the use of crystal as a container for drinks, which was more effective than metal. This claim is supported by accounts of him cutting large crystal goblets. Prior to his time, food was served plainly on platters on bare tables, as was the case with the Romans. He is also said to have popularized wine drinking. | 1 | Applied and Interdisciplinary Chemistry |
During the Cold War era, there was an escalation of atmospheric testing of nuclear weapons. After the atomic bombings of Hiroshima and Nagasaki in 1945, testing continued and the scale increased with the first hydrogen bomb in 1952. Soon after the United States tested the hydrogen bomb, the Soviet Union followed, in 1953. The mushroom clouds that occurred from the explosions released radioactive isotopes in mass quantities.
The first comprehensive study of the problem of radioactive isotope release began in spring 1949 with a one-man project called GABRIEL, conducted by Nicholas M. Smith Jr. at Oak Ridge National Laboratory. Smith produced his first report in 1949.
Project GABRIEL was revived in mid-1951 because bombs that were dropped had brought up concerns people had about the dangers of strontium-90. United States Atomic Energy Commission (AEC) was interested by GABRIEL's report though they said it was lacking in hard data and needed independent confirmation of the tests.
After reviewing Project GABRIEL in 1953, it was given first priority status. The secret project would define "practical limits" for using atomic weapons. A task team was assembled and the codename used was "Project HORN." In 1954, AEC argued that fallout was harmless because there was not enough evidence to prove that fallout would harm humans, animals, or crops. The AEC campaign persuaded the public that the worldwide fallout was harmless. This claim was later disputed when scientists announced publicly that there was no safe level of radiation. This was confirmed in a confidential report by a geneticist for the AEC. By 1954 and the Castle Bravo incident, it was obvious that radioactive fallout was dangerous to humans. The United States Atomic Energy Commission Division of Biology and Medicine dealt with efforts directed towards experimental and field studies and the correlation of data dealing with Project GABRIEL.
The RAND Corporation, Laboratories at Columbia University, AEC's New York office, the University of Chicago, an exclusive group of scientists, UCLA, and the United States Air Force were all involved in collection and testing of samples from around the world for radioactive fallout. | 0 | Theoretical and Fundamental Chemistry |
The sequence of exon 1 is highly conserved in mammalian species and editing of the pre-mRNA of this protein is likely to occur in mice, rat, dog and cow as well as humans. Even though the ECS is not conserved in non-mammals, an alternative ECS has been predicted in Zebrafish with a similar structure but in a different location. The Ecs is found downstream of the editing sites. | 1 | Applied and Interdisciplinary Chemistry |
Equilibrium phase transitions (e.g. order/disorder), an equation of state, and the kinetics of colloidal crystallization have all been actively studied, leading to the development of several methods to control the self-assembly of the colloidal particles. Examples include colloidal epitaxy and space-based reduced-gravity techniques, as well as the use of temperature gradients to define a density gradient. This is somewhat counterintuitive as temperature does not play a role in determining the hard-sphere phase diagram. However, hard-sphere single crystals (size 3 mm) have been obtained from a sample in a concentration regime that would remain in the liquid state in the absence of a temperature gradient. | 0 | Theoretical and Fundamental Chemistry |
Consider an infinitely long cylinder of radius starts rotating suddenly at time with an angular velocity . Then the velocity in the direction is given by
where is the modified Bessel function of the second kind. As , the solution approaches that of a rigid vortex. The force per unit area exerted on the cylinder is
where is the modified Bessel function of the first kind. | 1 | Applied and Interdisciplinary Chemistry |
A creamed emulsion increases the likelihood of coalescence due to the close proximity of the globules in the cream. Factors that influence the rate of creaming are similar to those involved in the sedimentation rate of suspension particles. Stokes Law is inadequate to predict creaming but can be used to identify these factors.
Creaming of an emulsion also increases the tendency of an emulsion to inversion. This class of process occurs mainly in special cases, when both the continuous and dispersed phases of an emulsion are liquid, as commonly is the state in dairy cream. It is common where the volume of the two fluid components is about the same or the volume of the dispersed phase is larger than that of the continuous phase. The process of emulsion inversion occurs when the dispersed droplets unite, but retain the formerly continuous material as droplets within the mass.
This is an "invert emulsion" or "inverted emulsion", in which the formerly continuous phase has become the dispersed phase and vice versa. Inversion happens in dairy cream when the butterfat concentration is too high and the resulting invert emulsion looks much like butter.
Commonly invert emulsions look much like a paste or thick cream and typical examples are mayonnaise, margarine (especially "low-fat" grades of margarine), pharmaceutical ointments, and cosmetic "creams".
Emulsion inversion differs from emulsion breaking in that a breaking emulsion tends to separate the two phases into un-emulsified continuous phases. Inversion of an emulsion may or may not be difficult to invert, but generally more difficult than creaming. | 0 | Theoretical and Fundamental Chemistry |
Spontaneous fission happens when a nucleus splits into two (occasionally three) smaller nuclei and generally one or more neutrons. | 0 | Theoretical and Fundamental Chemistry |
Heavy meromyosin (HMM) is the larger of the two fragments obtained from the muscle protein myosin II following limited proteolysis by trypsin or chymotrypsin. HMM contains two domains S-1 and S-2, S-1 contains is the globular head that can bind to actin while the S-2 domain projects at and angle from light meromyosin (LMM) connecting the two meromyosin fragments.
HMM is used to determine the polarity of actin filaments by decorating them with HMM then viewing them under the electron microscope. | 1 | Applied and Interdisciplinary Chemistry |
There are three known mammalian tachykinin receptors termed NK, NK and NK. All are members of the 7 transmembrane G-protein coupled receptor family and induce the activation of phospholipase C, producing inositol triphosphate (so called G-coupled).
Inhibitors of NK-1, known as NK-1 receptor antagonists, can be used as antiemetic agents, such as the drug aprepitant. | 1 | Applied and Interdisciplinary Chemistry |
Steady-state conduction is the form of conduction that happens when the temperature difference(s) driving the conduction are constant, so that (after an equilibration time), the spatial distribution of temperatures (temperature field) in the conducting object does not change any further. Thus, all partial derivatives of temperature concerning space may either be zero or have nonzero values, but all derivatives of temperature at any point concerning time are uniformly zero. In steady-state conduction, the amount of heat entering any region of an object is equal to the amount of heat coming out (if this were not so, the temperature would be rising or falling, as thermal energy was tapped or trapped in a region).
For example, a bar may be cold at one end and hot at the other, but after a state of steady-state conduction is reached, the spatial gradient of temperatures along the bar does not change any further, as time proceeds. Instead, the temperature remains constant at any given cross-section of the rod normal to the direction of heat transfer, and this temperature varies linearly in space in the case where there is no heat generation in the rod.
In steady-state conduction, all the laws of direct current electrical conduction can be applied to "heat currents". In such cases, it is possible to take "thermal resistances" as the analog to electrical resistances. In such cases, temperature plays the role of voltage, and heat transferred per unit time (heat power) is the analog of electric current. Steady-state systems can be modeled by networks of such thermal resistances in series and parallel, in exact analogy to electrical networks of resistors. See purely resistive thermal circuits for an example of such a network. | 1 | Applied and Interdisciplinary Chemistry |
Flotation of flexible objects is a phenomenon in which the bending of a flexible material allows an object to displace a greater amount of fluid than if it were completely rigid. This ability to displace more fluid translates directly into an ability to support greater loads, giving the flexible structure an advantage over a similarly rigid one. Inspiration to study the effects of elasticity are taken from nature, where plants, such as black pepper, and animals living at the water surface have evolved to take advantage of the load-bearing benefits elasticity imparts. | 1 | Applied and Interdisciplinary Chemistry |
The formation of small particles of a substance with a narrow size distribution is an important process in the pharmaceutical and other industries. Supercritical fluids provide a number of ways of achieving this by rapidly exceeding the saturation point of a solute by dilution, depressurization or a combination of these. These processes occur faster in supercritical fluids than in liquids, promoting nucleation or spinodal decomposition over crystal growth and yielding very small and regularly sized particles. Recent supercritical fluids have shown the capability to reduce particles up to a range of 5-2000 nm. | 0 | Theoretical and Fundamental Chemistry |
Born and raised in Taylorville, Illinois, Purcell received his BSEE in electrical engineering from Purdue University, followed by his M.A. and Ph.D. in physics from Harvard University. He was a member of the Alpha Xi chapter of the Phi Kappa Sigma fraternity while at Purdue. After spending the years of World War II working at the MIT Radiation Laboratory on the development of microwave radar, Purcell returned to Harvard to do research. In December 1946, he discovered nuclear magnetic resonance (NMR) with his colleagues Robert Pound and Henry Torrey. NMR provides scientists with an elegant and precise way of determining chemical structure and properties of materials, and is widely used in physics and chemistry. It also is the basis of magnetic resonance imaging (MRI), one of the most important medical advances of the 20th century. For his discovery of NMR, Purcell shared the 1952 Nobel Prize in physics with Felix Bloch of Stanford University.
Purcell also made contributions to astronomy as the first to detect radio emissions from neutral galactic hydrogen (the famous 21 cm line due to hyperfine splitting), affording the first views of the spiral arms of the Milky Way. This observation helped launch the field of radio astronomy, and measurements of the 21 cm line are still an important technique in modern astronomy. He has also made seminal contributions to solid state physics, with studies of spin-echo relaxation, nuclear magnetic relaxation, and negative spin temperature (important in the development of the laser). With Norman F. Ramsey, he was the first to question the CP symmetry of particle physics.
Purcell was the recipient of many awards for his scientific, educational, and civic work. He served as science advisor to Presidents Dwight D. Eisenhower, John F. Kennedy, and Lyndon B. Johnson. He was president of the American Physical Society, and a member of the American Philosophical Society, the National Academy of Sciences, and the American Academy of Arts and Sciences. He was awarded the National Medal of Science in 1979, and the Jansky Lectureship before the National Radio Astronomy Observatory. Purcell was also inducted into his Fraternity's (Phi Kappa Sigma) Hall of Fame as the first Phi Kap ever to receive a Nobel Prize.
Purcell was the author of the innovative introductory text Electricity and Magnetism. The book, a Sputnik-era project funded by an NSF grant, was influential for its use of relativity in the presentation of the subject at this level. The 1965 edition, now freely available due to a condition of the federal grant, was originally published as a volume of the Berkeley Physics Course. The book is also in print as a commercial third edition, as Purcell and Morin. Purcell is also remembered by biologists for his famous lecture "Life at Low Reynolds Number", in which he explained forces and effects dominating in limiting flow regimes (often at the micro scale). He also emphasized the time-reversibility of low Reynolds number flows with a principle referred to as the Scallop theorem.
Purcell died on March 7, 1997, in Cambridge, Massachusetts, aged 84. | 0 | Theoretical and Fundamental Chemistry |
During his life, Pigulevsky became the author of more than 200 publications. He was the author of several monographs, including:
"Essential oils"
"Formation and transformation of essential oils and resins in conifers"
"Chemistry of Terpenes" | 0 | Theoretical and Fundamental Chemistry |
These species feature elements from groups I, II, III, IV, V,VI, VII, 0 (excluding hydrogen) of the periodic table. Due to their often similar reactivity, the elements in group 3 (Sc, Y, and La) and group 12 (Zn, Cd, and Hg) are also generally included, and the lanthanides and actinides are sometimes included as well.
Main group compounds have been known since the beginnings of chemistry, e.g., elemental sulfur and the distillable white phosphorus. Experiments on oxygen, O, by Lavoisier and Priestley not only identified an important diatomic gas, but opened the way for describing compounds and reactions according to stoichiometric ratios. The discovery of a practical synthesis of ammonia using iron catalysts by Carl Bosch and Fritz Haber in the early 1900s deeply impacted mankind, demonstrating the significance of inorganic chemical synthesis.
Typical main group compounds are SiO, SnCl, and NO. Many main group compounds can also be classed as "organometallic", as they contain organic groups, e.g., B(CH)). Main group compounds also occur in nature, e.g., phosphate in DNA, and therefore may be classed as bioinorganic. Conversely, organic compounds lacking (many) hydrogen ligands can be classed as "inorganic", such as the fullerenes, buckytubes and binary carbon oxides.
* Examples: tetrasulfur tetranitride SN, diborane BH, silicones, buckminsterfullerene C.
Noble gas compounds include several derivatives of xenon and krypton.
* Examples: xenon hexafluoride XeF, xenon trioxide XeO, and krypton difluoride KrF | 0 | Theoretical and Fundamental Chemistry |
Wind-driven upwelling brings nutrients from deep waters to the surface which leads to biological productivity. Therefore, wind stress impacts biological activity around the globe. Two important forms of wind-driven upwelling are coastal upwelling and equatorial upwelling.
Coastal upwelling occurs when the wind stress is directed with the coast on its left (right) in the Northern (Southern) Hemisphere. If so, Ekman transport is directed away from the coast forcing waters from below to move upward. Well known coastal upwelling areas are the Canary Current, the Benguela Current, the California Current, the Humboldt Current, and the Somali Current. All of these currents support major fisheries due to the increased biological activities.
Equatorial upwelling occurs due to the trade winds blowing towards the west in both the Northern Hemisphere and the Southern Hemisphere. However, the Ekman transport that is associated with these trade winds is directed 90° to the right of the winds in the Northern Hemisphere and 90° to the left of the winds in the Southern Hemisphere. As a result, to the North of the equator water is transported away from the equator and to the South of the equator water is transported away from the equator. This horizontal divergence of mass has to be compensated and hence upwelling occurs. | 1 | Applied and Interdisciplinary Chemistry |
The non-stoichiometric cycles with a perovskite ABO can be describes with the following reactions:
::Reduction reaction: ABO → ABO + δ/2 O
::Oxidation reaction: ABO + δ HO → ABO + δ H
The reduction thermodynamics of perovskite makes it more favorable during the reduction half-cycle, during which more oxygen is produced; however, the oxidation thermodynamics proves less suitable, and sometimes perovskite is not completely oxidized. The two atomic sites, A and B, offer more doping possibilities and a much larger potential for different configurations. | 0 | Theoretical and Fundamental Chemistry |
SPINA-GD correlates to the T4-T3 conversion rate in slow tissue pools, as determined with isotope-based measurements in healthy volunteers. It was also shown that GD correlates with resting energy expenditure, body mass index and thyrotropin levels in humans, and that it is reduced in nonthyroidal illness with hypodeiodination. Multiple studies demonstrated SPINA-GD to rise after initiation of substitution therapy with selenium, a trace element that is essential for the synthesis of deiodinases. Conversely, it was observed that SPINA-GD is reduced in persons positive for autoantibodies to selenoprotein P, which is assumed to be involved in transport and storage of selenium. | 1 | Applied and Interdisciplinary Chemistry |
Arc is critical as a ubiquitous signaling factor in early embryonic development and is required for growth and patterning during gastrulation. The first knockouts (KOs) for Arc were therefore incompatible with life. Subsequent efforts produced homozygous knockout mice by targeting the entire Arc gene rather than portions of the coding region, eliminating dominant negative effects. These animals proved viable and exhibit no gross malformations in neuronal architecture, but express higher levels of the GluR1 subunit and increased miniature excitatory postsynaptic currents (mEPSCs) in addition to displaying deficiencies in long-term memory. | 1 | Applied and Interdisciplinary Chemistry |
The first kind of muon–catalyzed fusion to be observed experimentally, by L.W. Alvarez et al., was protium (H or H) and deuterium (D or H) muon-catalyzed fusion. The fusion rate for p–d (or pd) muon-catalyzed fusion has been estimated to be about a million times slower than the fusion rate for d–t muon-catalyzed fusion.
Of more practical interest, deuterium–deuterium muon-catalyzed fusion has been frequently observed and extensively studied experimentally, in large part because deuterium already exists in relative abundance and, like protium, deuterium is not at all radioactive. (Tritium rarely occurs naturally, and is radioactive with a half-life of about 12.5 years.)
The fusion rate for d–d muon-catalyzed fusion has been estimated to be only about 1% of the fusion rate for d–t muon-catalyzed fusion, but this still gives about one d–d nuclear fusion every 10 to 100 picoseconds or so. However, the energy released with every d–d muon-catalyzed fusion reaction is only about 20% or so of the energy released with every d–t muon-catalyzed fusion reaction. Moreover, the catalyzing muon has a probability of sticking to at least one of the d–d muon-catalyzed fusion reaction products that Jackson in this 1957 paper estimated to be at least 10 times greater than the corresponding probability of the catalyzing muon sticking to at least one of the d–t muon-catalyzed fusion reaction products, thereby preventing the muon from catalyzing any more nuclear fusions. Effectively, this means that each muon catalyzing d–d muon-catalyzed fusion reactions in pure deuterium is only able to catalyze about one-tenth of the number of d–t muon-catalyzed fusion reactions that each muon is able to catalyze in a mixture of equal amounts of deuterium and tritium, and each d–d fusion only yields about one-fifth of the yield of each d–t fusion, thereby making the prospects for useful energy release from d–d muon-catalyzed fusion at least 50 times worse than the already dim prospects for useful energy release from d–t muon-catalyzed fusion.
Potential "aneutronic" (or substantially aneutronic) nuclear fusion possibilities, which result in essentially no neutrons among the nuclear fusion products, are almost certainly not very amenable to muon-catalyzed fusion. One such essentially aneutronic nuclear fusion reaction involves a deuteron from deuterium fusing with a helion (He) from helium-3, which yields an energetic alpha particle and a much more energetic proton, both positively charged (with a few neutrons coming from inevitable d–d nuclear fusion side reactions). However, one muon with only one negative electric charge is incapable of shielding both positive charges of a helion from the one positive charge of a deuteron. The chances of the requisite two muons being present simultaneously are exceptionally remote. | 0 | Theoretical and Fundamental Chemistry |
Dexlansoprazole is used to heal and maintain healing of erosive esophagitis and to treat heartburn associated with gastroesophageal reflux disease (GERD). It lasts longer than lansoprazole, to which it is chemically related, and needs to be taken less often. There is no good evidence that it works better than other PPIs. | 0 | Theoretical and Fundamental Chemistry |
Biosolids may be defined as organic wastewater solids that can be reused after suitable sewage sludge treatment processes leading to sludge stabilization, such as anaerobic digestion and composting.
Alternatively, the definition of biosolids may be restricted by local regulations to wastewater solids only after those solids have completed a specified treatment sequence and have concentrations of pathogens and toxic chemicals below specified levels.
The United States Environmental Protection Agency (EPA) defines the two terms – sewage sludge and biosolids – in the Code of Federal Regulations (CFR), Title 40, Part 503 as follows: Sewage sludge refers to the solids separated during the treatment of municipal wastewater (including domestic septage). In contrast, biosolids refers to treated sewage sludge that meets the EPA pollutant and pathogen requirements for land application and surface disposal. A similar definition has been used internationally, for example, in Australia.
Use of the term "biosolids" may officially be subject to government regulations. However, informal use describes a broad range of semi-solid organic products from sewage or sewage sludge. This could include any solids, slime solids or liquid slurry residue generated during the treatment of domestic wastewater including, scum and solids removed during primary, secondary or advanced treatment processes. Materials that do not conform to the regulatory definition of "biosolids" can be given alternative terms like "wastewater solids. | 1 | Applied and Interdisciplinary Chemistry |
Nuclear fission can occur without neutron bombardment as a type of radioactive decay. This type of fission is called spontaneous fission, and was first observed in 1940. | 0 | Theoretical and Fundamental Chemistry |
* Lower digestive tract: laxatives, antispasmodics, antidiarrhoeals, bile acid sequestrants, opioids.
* Upper digestive tract: antacids, reflux suppressants, antiflatulents, antidopaminergics, proton pump inhibitors (PPIs), H-receptor antagonists, cytoprotectants, prostaglandin analogues. | 1 | Applied and Interdisciplinary Chemistry |
Structural genomics seeks to describe the 3-dimensional structure of every protein encoded by a given genome. This genome-based approach allows for a high-throughput method of structure determination by a combination of experimental and modeling approaches. The principal difference between structural genomics and traditional structural prediction is that structural genomics attempts to determine the structure of every protein encoded by the genome, rather than focusing on one particular protein. With full-genome sequences available, structure prediction can be done more quickly through a combination of experimental and modeling approaches, especially because the availability of large number of sequenced genomes and previously solved protein structures allows scientists to model protein structure on the structures of previously solved homologs.
Because protein structure is closely linked with protein function, the structural genomics has the potential to inform knowledge of protein function. In addition to elucidating protein functions, structural genomics can be used to identify novel protein folds and potential targets for drug discovery. Structural genomics involves taking a large number of approaches to structure determination, including experimental methods using genomic sequences or modeling-based approaches based on sequence or structural homology to a protein of known structure or based on chemical and physical principles for a protein with no homology to any known structure.
As opposed to traditional structural biology, the determination of a protein structure through a structural genomics effort often (but not always) comes before anything is known regarding the protein function. This raises new challenges in structural bioinformatics, i.e. determining protein function from its 3D structure.
Structural genomics emphasizes high throughput determination of protein structures. This is performed in dedicated centers of structural genomics.
While most structural biologists pursue structures of individual proteins or protein groups, specialists in structural genomics pursue structures of proteins on a genome wide scale. This implies large-scale cloning, expression and purification. One main advantage of this approach is economy of scale. On the other hand, the scientific value of some resultant structures is at times questioned. A Science article from January 2006 analyzes the structural genomics field.
One advantage of structural genomics, such as the Protein Structure Initiative, is that the scientific community gets immediate access to new structures, as well as to reagents such as clones and protein. A disadvantage is that many of these structures are of proteins of unknown function and do not have corresponding publications. This requires new ways of communicating this structural information to the broader research community. The Bioinformatics core of the Joint center for structural genomics (JCSG) has recently developed a wiki-based approach namely Open protein structure annotation network (TOPSAN) for annotating protein structures emerging from high-throughput structural genomics centers. | 1 | Applied and Interdisciplinary Chemistry |
Activation, in chemistry and biology, is the process whereby something is prepared or excited for a subsequent reaction. | 0 | Theoretical and Fundamental Chemistry |
The MRS technique was originally conceived in the 1960s by Russell H. Varian, one of the inventors of the proton magnetometer. SNMR is a product of a joint effort by many scientists and engineers who started developing this method in the USSR under the guidance of A.G. Semenov and continued this work all over the world. Semenov's team used nuclear magnetic resonance (NMR) for non-invasive detection of proton-containing liquids (hydrocarbons or water) in the subsurface. The Voevodsky Institute of Chemical Kinetics and Combustion of the Siberian Branch of the Russian Academy of Sciences fabricated the first version of the instrument for measurements of magnetic resonance signals from subsurface water ("hydroscope") in 1981. | 0 | Theoretical and Fundamental Chemistry |
MB-003 is a cocktail of three humanized or human–mouse chimeric mAbs: c13C6, h13F6, and c6D8. A study published in September 2012 found that rhesus macaques infected with Ebola virus (EBOV) survived when receiving MB-003 (mixture of 3 chimeric monoclonal antibodies) one hour after infection. When treated 24 or 48 hours after infection, four of six animals survived and had little to no viremia and few, if any, clinical symptoms.
MB-003 was created by scientists at the U.S. Army Medical Research Institute of Infectious Diseases, Gene Olinger, and Jamie Pettitt in collaboration with Mapp Biopharmaceutical with years of funding from US government agencies including the National Institute of Allergy and Infectious Disease, Biomedical Advanced Research and Development Authority, and the Defense Threat Reduction Agency. | 1 | Applied and Interdisciplinary Chemistry |
Boronic acids can be obtained via several methods. The most common way is reaction of organometallic compounds based on lithium or magnesium (Grignards) with borate esters. For example, phenylboronic acid is produced from phenylmagnesium bromide and trimethyl borate followed by hydrolysis
:PhMgBr + B(OMe) → PhB(OMe) + MeOMgBr
:PhB(OMe) + 2 HO → PhB(OH) + 2 MeOH
Another method is reaction of an arylsilane (RSiR) with boron tribromide (BBr) in a transmetallation to RBBr followed by acidic hydrolysis.
A third method is by palladium catalysed reaction of aryl halides and triflates with diboronyl esters in a coupling reaction known as the Miyaura borylation reaction. An alternative to esters in this method is the use of diboronic acid or tetrahydroxydiboron ([B(OH)]). | 0 | Theoretical and Fundamental Chemistry |
Ascorbic acid is a furan-based lactone of 2-ketogluconic acid. It contains an adjacent enediol adjacent to the carbonyl. This −C(OH)=C(OH)−C(=O)− structural pattern is characteristic of reductones, and increases the acidity of one of the enol hydroxyl groups. The deprotonated conjugate base is the ascorbate anion, which is stabilized by electron delocalization that results from resonance between two forms:
For this reason, ascorbic acid is much more acidic than would be expected if the compound contained only isolated hydroxyl groups. | 1 | Applied and Interdisciplinary Chemistry |
As for aldehydes, the hydrogen atoms on the carbon adjacent ("α to") the carboxyl group in esters are sufficiently acidic to undergo deprotonation, which in turn leads to a variety of useful reactions. Deprotonation requires relatively strong bases, such as alkoxides. Deprotonation gives a nucleophilic enolate, which can further react, e.g., the Claisen condensation and its intramolecular equivalent, the Dieckmann condensation. This conversion is exploited in the malonic ester synthesis, wherein the diester of malonic acid reacts with an electrophile (e.g., alkyl halide), and is subsequently decarboxylated. Another variation is the Fráter–Seebach alkylation. | 0 | Theoretical and Fundamental Chemistry |
Rho-dependent transcription terminators require a large protein called a Rho factor which exhibits RNA helicase activity to disrupt the mRNA-DNA-RNA polymerase transcriptional complex. Rho-dependent terminators are found in bacteria and phages. The Rho-dependent terminator occurs downstream of translational stop codons and consists of an unstructured, cytosine-rich sequence on the mRNA known as a Rho utilization site (rut), and a downstream transcription stop point (tsp). The rut serves as a mRNA loading site and as an activator for Rho; activation enables Rho to efficiently hydrolyze ATP and translocate down the mRNA while it maintains contact with the rut site. Rho is able to catch up with the RNA polymerase because it is being stalled at the downstream tsp sites. Multiple different sequences can function as a tsp site. Contact between Rho and the RNA polymerase complex stimulates dissociation of the transcriptional complex through a mechanism involving allosteric effects of Rho on RNA polymerase. | 1 | Applied and Interdisciplinary Chemistry |
ATSDR is an agency within the US Department of Health and Human Services concerned with the effects of hazardous substances on human health. ATSDR is charged with assessing the presence and nature of health hazards at specific Superfund sites, as well as helping prevent or reduce further exposure and the illnesses that can result from such exposures. ATSDR is an oversight agency created to ensure that public health protection and environmental regulation work hand in hand.
ATSDR functions include public health assessments of National Priority List (NPL or Superfund) hazardous waste sites; petitioned health consultations or assessments concerning specific waste sites or industrial facilities that US citizens have requested further action upon; the conduct of health studies (including surveillance and registries) to determine the long-term impact of these facilities; response to emergency releases of hazardous substances, applied research in support of public health assessments, information development and dissemination, and education and training concerning hazardous substances. ATSDR also prepares [https://wwwn.cdc.gov/TSP/index.aspx toxicological profiles] for hazardous substances found at National Priorities List sites, as well as at federal sites administered by the Department of Defense and Department of Energy. | 1 | Applied and Interdisciplinary Chemistry |
Organic chemistry studies the structure, properties, composition, reactions, and preparation by synthesis (or other means) of chemical compounds of carbon and hydrogen, which may contain any number of other elements such as nitrogen, oxygen and the halogens: fluorine, chlorine, bromine and iodine. Some organic compounds may also contain the elements phosphorus or sulfur. Examples of organic solids include wood, paraffin wax, naphthalene and a wide variety of polymers and plastics. | 0 | Theoretical and Fundamental Chemistry |
Lavello and Grubbs discovered the compound unexpectedly when trying to prepare noncarbonyl, low coordinate, Fe(0) complexes of N-heterocyclic carbenes (NHCs). They found that reactions of Fe(COT) and the NHC, 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene (SIMes), produced tetrametallic, Fe(I)-Fe(0) mixed valent NHC-COT complexes. In an attempt to characterize intermediates of the unusual transformation, they employed the more sterically hindered NHC, 1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene (SIPr) (with Dipp substituents).In benzene, the Dipp substituted NHC reacts with Fe(COT) to produce large black rhomboidal crystals of tris(cyclooctatetraene)triiron over 24 h at room temperature. Notably, the reaction was found to occur with catalytic amounts of NHC (10 mol%) yielding 67% of Fe(COT) after 24 h (turn over number=9.5). The synthesis is optimized when the reaction is conducted at 45 °C, yielding 95% conversion to the tris(cyclooctatetraene)triiron cluster. They also highlighted that heating Fe(COT) in benzene without any NHC to 100 °C for 24 h forms trace amounts of Fe(COT), but also large amounts of iron metal. Unsurprisingly, elemental analysis of the cluster affirms a 1:1 Fe:COT ratio.
The formation of Fe(COT) from Fe(COT) has been calculated to be slightly exothermic(15 kcal/mol).
Other NHCs lead to other unique mixed NHC-COT low valent iron complexes. Lavallo and Grubbs rationalize the transformation by emphasizing the capacity of NHCs to catalytically induce the formation of metal-metal bonds, where the steric hinderance of the NHC is essential, in particular, for the lability of the NHC (in coordination and dissociation) in the cycle. The bulky NHC is proposed to prevent reduction of COT by a bimetallic [(L)Fe(COT)] intermediate, where steric constraints block the bonding hapticity required to ligate a reduced form of COT. Another possibility put forward is that reduction of COT occurs only following coordination by a second carbene in the case of SIMes during the catalytic cycle. The sterically hindered NHC prevents such a transformation from occurring. | 0 | Theoretical and Fundamental Chemistry |
Response factor, usually in chromatography and spectroscopy, is the ratio between a signal produced by an analyte, and the quantity of analyte which produces the signal. Ideally, and for easy computation, this ratio is unity (one). In real-world scenarios, this is often not the case. | 0 | Theoretical and Fundamental Chemistry |
Several lanthanides produced at CERN-MEDICIS, samarium and terbium, are of interest for targeted therapy alike lutetium already used in the clinics. Lutetium emits low energy β particles with a short range, used for irradiation of smaller volume tumor targets. Terbium-149 emits short-range alpha particles, gamma-rays and positrons, in its decay scheme, which makes it suitable for targeted alpha therapy. The particular study of Tb produced by ISOLDE has been in folate receptor therapy, prominent in ovarian and lung cancer.
Sm, produced in the BR2 reactor at SCK CEN, followed by the subsequent mass separation by MEDICIS to increase its molar activity, was found to be suitable for targeted radionuclide therapy (TRNT) in a proof-of-concept research project. It emits low energy β particles and gamma peaks, and presents acceptable half-life for logistics and ambulatory care, making it a candidate of choice for theranostics approaches. | 0 | Theoretical and Fundamental Chemistry |
The energy of a low-angle boundary is dependent on the degree of misorientation between the neighbouring grains up to the transition to high-angle status. In the case of simple tilt boundaries the energy of a boundary made up of dislocations with Burgers vector b and spacing h is predicted by the Read–Shockley equation:
where:
with is the shear modulus, is Poisson's ratio, and is the radius of the dislocation core. It can be seen that as the energy of the boundary increases the energy per dislocation decreases. Thus there is a driving force to produce fewer, more misoriented boundaries (i.e., grain growth).
The situation in high-angle boundaries is more complex. Although theory predicts that the energy will be a minimum for ideal CSL configurations, with deviations requiring dislocations and other energetic features, empirical measurements suggest the relationship is more complicated. Some predicted troughs in energy are found as expected while others missing or substantially reduced.
Surveys of the available experimental data have indicated that simple relationships such as low are misleading: | 1 | Applied and Interdisciplinary Chemistry |
The developing embryo expresses cannabinoid receptors early in development that are responsive to anandamide secreted in the uterus. This signaling is important in regulating the timing of embryonic implantation and uterine receptivity. In mice, it has been shown that anandamide modulates the probability of implantation to the uterine wall. For example, in humans, the likelihood of miscarriage increases if uterine anandamide levels are too high or low. These results suggest that intake of exogenous cannabinoids (e.g., cannabis) can decrease the likelihood for pregnancy for women with high anandamide levels, and alternatively, it can increase the likelihood for pregnancy in women whose anandamide levels were too low. | 1 | Applied and Interdisciplinary Chemistry |
Oxhide ingots are heavy (20–30 kg) metal slabs, usually of copper but sometimes of tin, produced and widely distributed during the Mediterranean Late Bronze Age (LBA). Their shape resembles the hide of an ox with a protruding handle in each of the ingot’s four corners. Early thought was that each ingot was equivalent to the value of one ox. However, the similarity in shape is simply a coincidence. The ingots' producers probably designed these protrusions to make the ingots easily transportable overland on the backs of pack animals. Complete or partial oxhide ingots have been discovered in Sardinia, Crete, Peloponnese, Cyprus, Cannatello in Sicily, Boğazköy in Turkey (ancient Hattusa, the Hittite capital), Qantir in Egypt (ancient Pi-Ramesses), and Sozopol in Bulgaria. Archaeologists have recovered many oxhide ingots from two shipwrecks off the coast of Turkey (one off Uluburun and one in Cape Gelidonya). | 1 | Applied and Interdisciplinary Chemistry |
M2DS was first described in 1999.
In a Nature article published on November 25, 2015, it was revealed that researchers at the Baylor College of Medicine, led by Dr. Huda Y. Zoghbi, have reversed MECP2 Duplication Syndrome in adult symptomatic mice using antisense therapy. Mice treated with an experimental ASO administered through the central nervous system had a reduction of MECP2 protein to normal levels and symptoms of hypoactivity, anxiety, and abnormal social behavior were resolved. Additionally, the seizure activity of the mice and abnormal EEG discharges were abolished. Initial studies demonstrated that reducing the MECP2 protein levels to the correct amount also normalized the expression of the other genes controlled by the MECP2 protein. | 1 | Applied and Interdisciplinary Chemistry |
Cryoneurolysis is performed with a cryoprobe, which is composed of a hollow cannula that contains a smaller inner lumen. The pressurized coolant (nitrous oxide, carbon dioxide or liquid nitrogen) travels down the lumen and expands at the end of the lumen into the tip of the hollow cannula. No coolant exits the cryoprobe. The expansion of the pressurized liquid causes the surrounding area to cool (known as the Joule–Thomson effect) and the phase change of the liquid to gas also causes the surrounding area to cool. This causes a visible iceball to form and the tissue surrounding the end of the cryoprobe to freeze. The gas form of the coolant then travels up the length of the cryoprobe and is safely expelled. The tissue surrounding the end of the cryoprobe can reach as low as −88.5 °C with nitrous oxide as the coolant, and as low as −195.8 °C with liquid nitrogen. Temperatures below −100 °C are damaging to nerves.
Cryo-S Painless cryoanalgesia device is the next generation of apparatus used by many experts in the field since 1992. The working medium for Cryo-S Painless is carbon dioxide: (−78 °C) or nitrous oxide: (−89 °C), very efficient and easy to use gases. Cryo-S Painless is controlled by a microprocessor and all the parameters are displayed and monitored on a LCD screen. Mode selection probe, cleaning and freezing can be performed automatically using footswitch or touch screen which allows to keep the site of a procedure under sterile conditions. Electronic communication (chip system) between the connected probe and device allows recognition of optimal operating parameters and auto-configures to cryoprobe characteristics. Pressure and gas flow are set automatically, any manual adjustment is not necessary. Cryoprobe temperature, cylinder pressure, gas flow inside of cryoprobe and procedure time are displayed during freezing. Built-in voice communication Built-in neurostimulation (sensory, motor). | 1 | Applied and Interdisciplinary Chemistry |
In 2015 TTFRI acquired a set of UAVs from Australia for use their typhoon research program. Early attempts to acquire UAVs in 2005 were scrapped due to stricter air traffic controls imposed as a result of global terrorism. | 1 | Applied and Interdisciplinary Chemistry |
The identity operation corresponds to doing nothing to the object. Because every molecule is indistinguishable from itself if nothing is done to it, every object possesses at least the identity operation. The identity operation is denoted by or . In the identity operation, no change can be observed for the molecule. Even the most asymmetric molecule possesses the identity operation. The need for such an identity operation arises from the mathematical requirements of group theory. | 0 | Theoretical and Fundamental Chemistry |
Perfluorohexanoic acid (PFHxA) is a fluorinated carboxylic acid derivative of hexanoic acid. Fluorinated polymers with six carbon or less commonly degrade into perfluorohexanoic acid.
Perfluorohexanoic acid has been found to rapidly bioaccumulate.
In 2020 Michigan adopted drinking water standards for 5 previously unregulated PFAS compounds including PFHxA which has a maximum contaminant level (MCL) of 400 parts per billion (ppb). | 1 | Applied and Interdisciplinary Chemistry |
The cyclic trimer anions dissociate almost completely in aqueous solution giving mainly tetrahydroxyborate anions:
Other molecules and anions, such as , , , and are less than 5% at 26 °C.
In 1937, Nielsen and Ward claimed that the metaborate anion in solution has a linear symmetric structure with negative charges on the oxygens and a positive charge on the boron, or with negative charge on the boron. However, this claim has been disproved. | 0 | Theoretical and Fundamental Chemistry |
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