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Charles William Shoppee FAA FRS (1904–1994) was a British-born organic chemist who performed major research into steroids. He was Professor of Chemistry at the University College of Swansea (1946–1956) and Professor of Organic Chemistry at the University of Sydney (1956–1969).
The short citation on his election as Fellow of the Australian Academy of Science (in 1958) reads: [Shoppee] "is distinguished for his contributions to organic chemistry, with special reference to the investigation of problems of reaction mechanism, the establishment of the structures of the adreno-cortical hormones, and the elucidation of stereochemical relationships in the steroid field."
Born on 24 February 1904 at Crouch End, (London, UK), to Joseph William and Emma Elizabeth Shoppee (née Hawkswell of York), he was educated at the Stationers Companys School and Imperial College (Royal College of Science). Early positions were at the University of Leeds (1924-1938), Basel (1938-1945) and the University of London (1945-1948). He married Eileen West on 18 July 1929 and completed a D.Sc. from the University of London in 1931.
From 1948 to 1956 he was Professor of Chemistry at the University College, Swansea, of the University of Wales, and from 1956 until his compulsory retirement he was Professor of Organic Chemistry at the University of Sydney. He was elected Fellow of the Royal Society (1956) and Fellow of the Australian Academy of Science (1958).
On his retirement in 1969, aged 65, he accepted the position of Foundation Welch Professorship of Chemistry at Texas Technological University (1970–1974). He returned to Australia in 1975, where he served as an honorary professorial fellow at Macquarie University (1976–1979) and was honorary visiting professor at La Trobe University from 1980 where he was still active in the laboratory in 1991. He died on . | 0 | Organic Chemistry |
The United Nations framework for Sustainable Development Goals recognizes the damaging effects of eutrophication for marine environments. It has established a timeline for creating an Index of Coastal Eutrophication and Floating Plastic Debris Density (ICEP) within Sustainable Development Goal 14 (life below water). SDG 14 specifically has a target to: "by 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution".
Policy and regulations are a set of tools to minimize causes of eutrophication. Nonpoint sources of pollution are the primary contributors to eutrophication, and their effects can be minimized through common agricultural practices. Reducing the amount of pollutants that reach a watershed can be achieved through the protection of its forest cover, reducing the amount of erosion leeching into a watershed. Also, through the efficient, controlled use of land using sustainable agricultural practices to minimize land degradation, the amount of soil runoff and nitrogen-based fertilizers reaching a watershed can be reduced. Waste disposal technology constitutes another factor in eutrophication prevention.
Because a body of water can have an effect on a range of people reaching far beyond that of the watershed, cooperation between different organizations is necessary to prevent the intrusion of contaminants that can lead to eutrophication. Agencies ranging from state governments to those of water resource management and non-governmental organizations, going as low as the local population, are responsible for preventing eutrophication of water bodies. In the United States, the most well known inter-state effort to prevent eutrophication is the Chesapeake Bay. | 2 | Environmental Chemistry |
Syntheses of large complex catalysts are time and resource consuming. An unexpected deviation from the design could be disastrous. Once a catalyst is discovered, modification for further adjustment could be so synthetically challenging that it is easier to study the poor catalyst than to improve it. | 6 | Supramolecular Chemistry |
An organophosphinic acid is an organophosphorus compound with the formula RHPOH (R = alkyl, aryl). One or both P-H bonds in the parent hypophosphorous acid (aka phosphinic acid) are replaced by organic groups. The Cyanex family of dialkylphosphinic acids are used in hydrometallurgy to extract metals from ores. | 0 | Organic Chemistry |
Tartaric acid is a white, crystalline organic acid that occurs naturally in many fruits, most notably in grapes but also in tamarinds, bananas, avocados, and citrus. Its salt, potassium bitartrate, commonly known as cream of tartar, develops naturally in the process of fermentation. Potassium bitartrate is commonly mixed with sodium bicarbonate and is sold as baking powder used as a leavening agent in food preparation. The acid itself is added to foods as an antioxidant E334 and to impart its distinctive sour taste. Naturally occurring tartaric acid is a useful raw material in organic chemical synthesis. Tartaric acid, an alpha-hydroxy-carboxylic acid, is diprotic and aldaric in acid characteristics and is a dihydroxyl derivative of succinic acid. | 4 | Stereochemistry |
The SH2 (Src Homology 2) domain is a structurally conserved protein domain contained within the Src oncoprotein and in many other intracellular signal-transducing proteins. SH2 domains bind to phosphorylated tyrosine residues on other proteins, modifying the function or activity of the SH2-containing protein. The SH2 domain may be considered the prototypical modular protein-protein interaction domain, allowing the transmission of signals controlling a variety of cellular functions. SH2 domains are especially common in adaptor proteins that aid in the signal transduction of receptor tyrosine kinase pathways. | 1 | Biochemistry |
A bilayer is a double layer of closely packed atoms or molecules.
The properties of bilayers are often studied in condensed matter physics, particularly in the context of semiconductor devices, where two distinct materials are united to form junctions, such as p–n junctions, Schottky junctions, etc. Layered materials, such as graphene, boron nitride, or transition metal dichalcogenides, have unique electronic properties as a bilayer system and are an active area of current research.
In biology, a common example is the lipid bilayer, which describes the structure of multiple organic structures, such as the membrane of a cell. | 7 | Physical Chemistry |
Australia and New Zealand published nutrient reference values including guidelines for dietary vitamin D intake in 2006. About a third of Australians have vitamin D deficiency. | 1 | Biochemistry |
Molecular machines are a class of molecules typically described as an assembly of a discrete number of molecular components intended to produce mechanical movements in response to specific stimuli, mimicking macromolecular devices such as switches and motors. Naturally occurring or biological molecular machines are responsible for vital living processes such as DNA replication and ATP synthesis. Kinesins and ribosomes are examples of molecular machines, and they often take the form of multi-protein complexes. For the last several decades, scientists have attempted, with varying degrees of success, to miniaturize machines found in the macroscopic world. The first example of an artificial molecular machine (AMM) was reported in 1994, featuring a rotaxane with a ring and two different possible binding sites. In 2016 the Nobel Prize in Chemistry was awarded to Jean-Pierre Sauvage, Sir J. Fraser Stoddart, and Bernard L. Feringa for the design and synthesis of molecular machines.
AMMs have diversified rapidly over the past few decades and their design principles, properties, and characterization methods have been outlined better. A major starting point for the design of AMMs is to exploit the existing modes of motion in molecules, such as rotation about single bonds or cis-trans isomerization. Different AMMs are produced by introducing various functionalities, such as the introduction of bistability to create switches. A broad range of AMMs has been designed, featuring different properties and applications; some of these include molecular motors, switches, and logic gates. A wide range of applications have been demonstrated for AMMs, including those integrated into polymeric, liquid crystal, and crystalline systems for varied functions (such as materials research, homogenous catalysis and surface chemistry). | 6 | Supramolecular Chemistry |
The branched and cyclic nature of carbohydrates poses particular problems to structure validation tools. At higher resolutions, it is possible to determine the sequence/structure of oligo- and poly-saccharides, both as covalent modifications and as ligands. However, at lower resolutions (typically lower than 2.0Å), sequences/structures should either match known structures, or be supported by complementary techniques such as Mass Spectrometry. Also, monosaccharides have clear conformational preferences (saturated rings are typically found in chair conformations), but errors introduced during model building and/or refinement (wrong linkage chirality or distance, or wrong choice of model - see for recommendations on carbohydrate model building and refinement and for reviews on general errors in carbohydrate structures) can bring their atomic models out of the more likely low-energy state. Around 20% of the deposited carbohydrate structures are in a higher-energy conformation not justified by the structural data (measured using real-space correlation coefficient).
A number of carbohydrate validation web services are available at [http://ww.glycosciences.de glycosciences.de] (including nomenclature checks and linkage checks by [http://www.glycosciences.de/tools/pdb-care/ pdb-care], and cross-validation with Mass Spectrometry data through the use of GlycanBuilder), whereas the CCP4 suite currently distributes [http://www.ccp4.ac.uk/html/privateer.html Privateer], which is a tool that is integrated into the model building and refinement process itself. Privateer is able to check stereo- and regio-chemistry, ring conformation and puckering, linkage torsions, and real-space correlation against positive omit density, generating aperiodic torsion restraints on ring bonds, which can be used by any refinement software in order to maintain the monosaccharide's minimal energy conformation.
Privateer also generates scalable two-dimensional SVG diagrams according to the Essentials of Glycobiology standard symbol nomenclature containing all the validation information as tooltip annotations (see figure). This functionality is currently integrated into other CCP4 programs, such as the molecular graphics program CCP4mg (through the Glycoblocks 3D representation, which conforms to the standard symbol nomenclature) and the suite's graphical interface, CCP4i2. | 1 | Biochemistry |
Hemiaminal formation is a key step in an asymmetric total synthesis of saxitoxin:
In this reaction step the alkene group is first oxidized to an intermediate acyloin by action of osmium(III) chloride, oxone (sacrificial catalyst) and sodium carbonate (base). | 0 | Organic Chemistry |
In comparison to cationic cyclizations, radical cyclizations avoid issues associated with Wagner-Meerwein rearrangements, do not require strongly acidic conditions, and can be kinetically controlled. Cationic cyclizations are usually thermodynamically controlled. Radical cyclizations are much faster than analogous anionic cyclizations, and avoid β-elimination side reactions. Anionic Michael-type cyclization is an alternative to radical cyclization of activated olefins. Metal-catalyzed cyclization reactions usually require mildly basic conditions, and substrates must be chosen to avoid β-hydride elimination. The primary limitation of radical cyclizations with respect to these other methods is the potential for radical side reactions. | 0 | Organic Chemistry |
Sodium ions () are necessary in small amounts for some types of plants, but sodium as a nutrient is more generally needed in larger amounts by animals, due to their use of it for generation of nerve impulses and for maintenance of electrolyte balance and fluid balance. In animals, sodium ions are necessary for the aforementioned functions and for heart activity and certain metabolic functions. The health effects of salt reflect what happens when the body has too much or too little sodium.
Characteristic concentrations of sodium in model organisms are: 10 mM in E. coli, 30 mM in budding yeast, 10 mM in mammalian cell and 100 mM in blood plasma.
Additionally, sodium ions are essential to several cellular processes. They are responsible for the co-transport of glucose in the sodium glucose symport, are used to help maintain membrane polarity with the help of the sodium potassium pump, and are paired with water to thin the mucus of the airway lumen when the active Cystic Fibrosis Transport Receptor moves chloride ions into the airway. | 1 | Biochemistry |
In the oil and gas industry, green oil refers to oligomers formed in all C2, C3, and C4 hydrogenation reactors of ethylene plants and other petrochemical production facilities; it is a mixture of C4 to C20 unsaturated and reactive components with about 90% aliphatic dienes and 10% of alkanes plus alkenes. Different heterogeneous and homogeneous catalysts are operative in producing green oils via the oligomerization of alkenes. | 7 | Physical Chemistry |
Spherical top molecules have no net dipole moment. A pure rotational spectrum cannot be observed by absorption or emission spectroscopy because there is no permanent dipole moment whose rotation can be accelerated by the electric field of an incident photon. Also the polarizability is isotropic, so that pure rotational transitions cannot be observed by Raman spectroscopy either. Nevertheless, rotational constants can be obtained by ro–vibrational spectroscopy. This occurs when a molecule is polar in the vibrationally excited state. For example, the molecule methane is a spherical top but the asymmetric C-H stretching band shows rotational fine structure in the infrared spectrum, illustrated in rovibrational coupling. This spectrum is also interesting because it shows clear evidence of Coriolis coupling in the asymmetric structure of the band. | 7 | Physical Chemistry |
Life That Glows (also known as David Attenborough’s Light on Earth) is a 2016 British nature documentary programme made for BBC Television, first shown in the UK on BBC Two on 9 May 2016. The programme is presented and narrated by Sir David Attenborough.
Life That Glows depicts the biology and ecology of bioluminescent organisms, that is, organisms capable of creating light. The programme features fireflies, who use light as a means of sexual attraction, luminous fungi, luminous marine bacteria responsible for the Milky seas effect, the flashlight fish, the aposematism of the Sierra luminous millipede, earthworms, and the bioluminescent tides created by blooms of dinoflagellates in Tasmania, as well as dolphins swimming in the bloom in the Sea of Cortez, the defensive flashes of brittle stars and ostracods, sexual attraction in ostracods, prey attraction by luminous click beetles in Cerrado, Brazil and Arachnocampa gnats in New Zealand.
The programme then introduces many luminous deep sea animals, including the vampire squid, the polychaete worm Tomopteris that generates yellow light, the jellyfish Atolla, the comb jelly Beroe, the viper fish, pyrosomes, a dragonfish, and the polychaete worm Flota. Next, the programme discusses specialised adaptations in the eyes of particular animals to see bioluminescence, such as the barreleye fish and the cock-eyed squid. Lastly, the programme features the mass spawning event of the firefly squid in Japan. | 1 | Biochemistry |
For samples which scatter light, absorbance is defined as "the negative logarithm of one minus absorptance (absorption fraction: ) as measured on a uniform sample". For decadic absorbance, this may be symbolized as If a sample both transmits and remits light, and is not luminescent, the fraction of light absorbed remitted and transmitted add to 1: Note that and the formula may be written as For a sample which does not scatter, and yielding the formula for absorbance of a material discussed below.
Even though this absorbance function is very useful with scattering samples, the function does not have the same desirable characteristics as it does for non-scattering samples. There is, however, a property called absorbing power which may be estimated for these samples. The absorbing power of a single unit thickness of material making up a scattering sample is the same as the absorbance of the same thickness of the material in the absence of scatter. | 7 | Physical Chemistry |
Non-ferrous extractive metallurgy is one of the two branches of extractive metallurgy which pertains to the processes of reducing valuable, non-iron metals from ores or raw material. Metals like zinc, copper, lead, aluminium as well as rare and noble metals are of particular interest in this field, while the more common metal, iron, is considered a major impurity. Like ferrous extraction, non-ferrous extraction primarily focuses on the economic optimization of extraction processes in separating qualitatively and quantitatively marketable metals from its impurities (gangue).
Any extraction process will include a sequence of steps or unit processes for separating highly pure metals from undesirables in an economically efficient system. Unit processes are usually broken down into three categories: pyrometallurgy, hydrometallurgy, and electrometallurgy. In pyrometallurgy, the metal ore is first oxidized through roasting or smelting. The target metal is further refined at high temperatures and reduced to its pure form. In hydrometallurgy, the object metal is first dissociated from other materials using a chemical reaction, which is then extracted in pure form using electrolysis or precipitation. Finally, electrometallurgy generally involves electrolytic or electrothermal processing. The metal ore is either distilled in an electrolyte or acid solution, then magnetically deposited onto a cathode plate (electrowinning); or smelted then melted using an electric arc or plasma arc furnace (electrothermic reactor).
Another major difference in non-ferrous extraction is the greater emphasis on minimizing metal losses in slag. This is widely due to the exceptional scarcity and economic value of certain non-ferrous metals which are, inevitably, discarded during the extraction process to some extent. Thus, material resource scarcity and shortages are of great concern to the non-ferrous industry. Recent developments in non-ferrous extractive metallurgy now emphasize the reprocessing and recycling of rare and non-ferrous metals from secondary raw materials (scrap) found in landfills. | 8 | Metallurgy |
First held in 1908, the [https://iifiir.org/en/iir-conferences-series International Congress of Refrigeration] of the IIR is a flagship event that converges industry and research.
Covering all fields of refrigeration, the Congress, which takes place every four years, reunites key international stakeholders and provides perspectives on the future of the industry in line with sustainable development. | 7 | Physical Chemistry |
In Complex I (NADH ubiquinone oxidoreductase, Type I NADH dehydrogenase, or mitochondrial complex I; ), two electrons are removed from NADH and transferred to a lipid-soluble carrier, ubiquinone (Q). The reduced product, ubiquinol (QH), freely diffuses within the membrane, and Complex I translocates four protons (H) across the membrane, thus producing a proton gradient. Complex I is one of the main sites at which premature electron leakage to oxygen occurs, thus being one of the main sites of production of superoxide.
The pathway of electrons is as follows:
NADH is oxidized to NAD, by reducing flavin mononucleotide to FMNH in one two-electron step. FMNH is then oxidized in two one-electron steps, through a semiquinone intermediate. Each electron thus transfers from the FMNH to an Fe–S cluster, from the Fe-S cluster to ubiquinone (Q). Transfer of the first electron results in the free-radical (semiquinone) form of Q, and transfer of the second electron reduces the semiquinone form to the ubiquinol form, QH. During this process, four protons are translocated from the mitochondrial matrix to the intermembrane space. As the electrons move through the complex an electron current is produced along the 180 Angstrom width of the complex within the membrane. This current powers the active transport of four protons to the intermembrane space per two electrons from NADH. | 1 | Biochemistry |
A first order reaction depends on the concentration of only one reactant (a unimolecular reaction). Other reactants can be present, but their concentration has no effect on the rate. The rate law for a first order reaction is
Although not affecting the above math, the majority of first order reactions proceed via intermolecular collisions. Such collisions, which contribute the energy to the reactant, are necessarily second order. The rate of these collisions is, however, masked by the fact that the rate determining step remains the unimolecular breakdown of the energized reactant.
The half-life is independent of the starting concentration and is given by . The mean lifetime is τ = 1/k.
Examples of such reactions are:
In organic chemistry, the class of S1 (nucleophilic substitution unimolecular) reactions consists of first-order reactions. For example, in the reaction of aryldiazonium ions with nucleophiles in aqueous solution, , the rate equation is where Ar indicates an aryl group. | 7 | Physical Chemistry |
The evaluated parameters are:
* time to specimen failure (e.g., breakage, or from other "failure" criteria)
* ductility (by elongation to fracture or the reduction of the area)
* ultimate tensile strength (from the maximum load)
* area under the elongation - load curve (which represents the fracture energy)
* percent of ductile/brittle fracture on the fracture surface
* threshold stress for cracking
The results of the SSRT tests are evaluated using the ratio:
The departure of the ratio below unity quantifies the increased susceptibility to cracking.
The test is best used in combination with electrochemical measurements and other stress corrosion cracking tests. | 8 | Metallurgy |
An estimated 30% of agrichemical compounds contain fluorine. Most of them are used as poisons, but a few stimulate growth instead.
Sodium fluoroacetate has been used as an insecticide, but it is especially effective against mammalian pests. The name "1080" refers to the catalogue number of the poison, which became its brand name. Fluoroacetate is similar to acetate, which has a pivotal role in the Krebs cycle (a key part of cell metabolism). Fluoroacetate halts the cycle and causes cells to be deprived of energy. Several other insecticides contain sodium fluoride, which is much less toxic than fluoroacetate. Insects fed 29-fluorostigmasterol use it to produce fluoroacetates. If a fluorine is transferred to a body cell, it blocks metabolism at the position occupied.
Trifluralin was widely used in the 20th century, for example, in over half of U.S. cotton field acreage in 1998. Because of its suspected carcinogenic properties some Northern European countries banned it in 1993. As of 2015, the European Union has banned it, although Dow made a case to cancel the decision in 2011. | 1 | Biochemistry |
RNA polymerase II (also called RNAP II and Pol II) is an enzyme found in eukaryotic cells. It catalyzes the transcription of DNA to synthesize precursors of mRNA and most snRNA and microRNA. In humans, RNAP II consists of seventeen protein molecules (gene products encoded by POLR2A-L, where the proteins synthesized from POLR2C, POLR2E, and POLR2F form homodimers). | 1 | Biochemistry |
Dedicated or partially dedicated GISAXS beamlines exist at most synchrotron light sources (for instance Advanced Light Source (ALS), Australian Synchrotron, APS, ELETTRA (Italy), Diamond (UK), ESRF, National Synchrotron Light Source II (NSLS-II), Pohang Light Source (South Korea), SOLEIL (France), Shanghai Synchrotron (PR China), SSRL
At neutron research facilities, GISANS is increasingly used, typically on small-angle (SANS) instruments or on reflectometers.
GISAS does not require any specific sample preparation other than thin film deposition techniques. Film thicknesses may range from a few nm to several 100 nm, and such thin films are still fully penetrated by the x-ray beam. The film surface, the film interior, as well as the substrate-film interface are all accessible. By varying the incidence angle the various contributions can be identified. | 7 | Physical Chemistry |
Gold mined from the Cordillera Mountain Range were brought down to the coast through the Aringay-Tonglo-Balatok gold trail, making commercial trade centers out of Aringay and the neighboring settlement of Agoo, whose coast at the time was shaped in such a way that it was a good harbor for foreign vessels coming into Lingayen Gulf. On the island of Mindanao, gold was mined along the Agusan River in the Butuan-Surigao area and extensively worked in the Butuan polity located at the mouth of the Agusan River. | 8 | Metallurgy |
There are two major classes of Neuraminidase that cleave exo or endo poly-sialic acids:
* Exo hydrolysis of α-(2→3)-, α-(2→6)-, α-(2→8)-glycosidic linkages of terminal sialic acid residues
* Endo hydrolysis of (2→8)-α-sialosyl linkages in oligo- or poly(sialic) acids (see endo-α-sialidase.) | 0 | Organic Chemistry |
Hydrogen embrittlement is a volume effect: it affects the volume of the material. Environmental embrittlement is a surface effect where molecules from the atmosphere surrounding the material under test are adsorbed onto the fresh crack surface. This is most clearly seen from fatigue measurements where the measured crack growth rates can be an order of magnitude higher in hydrogen than in air. That this effect is due to adsorption, which saturates when the crack surface is completely covered, is understood from the weak dependence of the effect on the pressure of hydrogen.
Environmental embrittlement is also observed to reduce fracture toughness in fast fracture tests, but the severity is much reduced compared with the same effect in fatigue
Hydrogen embrittlement is the effect where a previously embrittled material has low fracture toughness whatever atmosphere it is tested in. Environmental embrittlement is the effect when the low fracture toughness is only observed when the testing happens in that atmosphere. | 7 | Physical Chemistry |
Secondary electrons are also the main means of viewing images in the scanning electron microscope (SEM). The range of secondary electrons depends on the energy. Plotting the inelastic mean free path as a function of energy often shows characteristics of the "universal curve" familiar to electron spectroscopists and surface analysts. This distance is on the order of a few nanometers in metals and tens of nanometers in insulators. This small distance allows such fine resolution to be achieved in the SEM.
For SiO, for a primary electron energy of 100 eV, the secondary electron range is up to 20 nm from the point of incidence. | 7 | Physical Chemistry |
Total thyroxine is rarely measured, having been largely superseded by free thyroxine tests. Total thyroxine (Total T) is generally elevated in hyperthyroidism and decreased in hypothyroidism. It is usually slightly elevated in pregnancy secondary to increased levels of thyroid binding globulin (TBG).
Total T4 is measured to see the bound and unbound levels of T4. The total T4 is less useful in cases where there could be protein abnormalities. The total T4 is less accurate due to the large amount of T4 that is bound. The total T3 is measured in clinical practice since the T3 has decreased amount that is bound as compared to T4.
Reference ranges depend on the method of analysis. Results should always be interpreted using the range from the laboratory that performed the test. Example values are: | 1 | Biochemistry |
Tebbe's reagent itself does not react with carbonyl compounds, but must first be treated with a mild Lewis base, such as pyridine, which generates the active Schrock carbene.
Also analogous to the Wittig reagent, the reactivity appears to be driven by the high oxophilicity of Ti(IV). The Schrock carbene (1) reacts with carbonyl compounds (2) to give a postulated oxatitanacyclobutane intermediate (3). This cyclic intermediate has never been directly isolated, presumably because it breaks down immediately to the produce the desired alkene (5). | 0 | Organic Chemistry |
*Zelinsky did not patent the gas mask he invented, believing that one should not profit from human misfortunes, and Russia transferred the right to produce it to the Allies.
*The only surviving copy of the first gas mask is in Zelinsky's apartment.
*During an internship in Germany before the start of the war, Zelinsky synthesized chloropicrin for the first time, and became the first person to experience its toxic effects. Later, chloropicrin, discovered by Zelinsky, was widely used as a chemical warfare agent. | 0 | Organic Chemistry |
The basic idea of quantum typicality is that the vast majority of all pure states featuring a common expectation value of some generic observable at a given time will yield very similar expectation values of the same observable at any later time.
This is meant to apply to Schrödinger type dynamics in high dimensional Hilbert spaces. As a consequence individual dynamics of expectation values are then typically well described by the ensemble average.
Quantum ergodic theorem originated by John von Neumann is a strong result arising from the mere mathematical structure of quantum mechanics. The QET is a precise formulation of termed normal typicality, i.e. the statement that, for typical large systems, every initial wave function from an energy shell is ‘normal’: it evolves in such a way that for most t, is macroscopically equivalent to the micro-canonical density matrix. | 7 | Physical Chemistry |
* Generically: Rg + X + hν → RgX + X, where Rg is a rare gas and X is a halogen
* Ba...FCH + hν → BaF + CH
*K + CHI → KI + CH | 7 | Physical Chemistry |
While the synthesis of nanocrystalline feedstocks in the form of foils, powders, and wires is relatively straightforward, the tendency of nanocrystalline feedstocks to coarsen upon extended exposure to elevated temperatures means that low-temperature and rapid densification techniques are necessary to consolidate these feedstocks into bulk components. A variety of techniques show potential in this respect, such as spark plasma sintering or ultrasonic additive manufacturing, although the synthesis of bulk nanocrystalline components on a commercial scale remains untenable. | 8 | Metallurgy |
Soil supplementation with molasses increases microbial synthesis of MA. This is thought to occur naturally as part of soil microbe suppression of disease, so soil amendment with molasses can be used as a crop treatment in horticulture. | 1 | Biochemistry |
Cytochrome f is the largest subunit of cytochrome bf complex (plastoquinol—plastocyanin reductase; ). In its structure and functions, the cytochrome b6f complex bears extensive analogy to the cytochrome bc1 complex of mitochondria and photosynthetic purple bacteria. Cytochrome f (cyt f) plays a role analogous to that of cytochrome c1, in spite of their different structures.
The 3D structure of Brassica rapa (Turnip) cyt f has been determined. The lumen-side segment of cyt f includes two structural domains: a small one above a larger one that, in turn, is on top of the attachment to the membrane domain. The large domain consists of an anti-parallel beta-sandwich and a short haem-binding peptide, which form a three-layer structure. The small domain is inserted between beta-strands F and G of the large domain and is an all-beta domain. The haem nestles between two short helices at the N terminus of cyt f. Within the second helix is the sequence motif for the c-type cytochromes, CxxCH (residues 21–25), which is covalently attached to the haem through thioether bonds to Cys-21 and Cys-24. His-25 is the fifth haem iron ligand. The sixth haem iron ligand is the alpha-amino group of Tyr-1 in the first helix. Cyt f has an internal network of water molecules that may function as a proton wire. The water chain appears to be a conserved feature of cyt f. | 5 | Photochemistry |
Alain Berton was awarded the Medal of the International Bureau of Analytical Chemistry (BICA)- International fight against chemical weapons. led by :fr:Paul Nicolardot. | 3 | Analytical Chemistry |
A more complex, specific example of crosstalk between two major signaling pathways can be observed with the interaction of the cAMP and MAPK signaling pathways in the activation of lymphocytes. In this case, components of the cAMP pathway directly and indirectly affect MAPK signaling pathway meant to activate genes involving immunity and lymphocytes.
Newly formed cAMP is released from the membrane and diffuses across the intracellular space where it serves to activate PKA. The catalytic subunit of PKA must bind four molecules of cAMP to be activated, whereupon activation consists of cleavage between the regulatory and catalytic subunits. This cleavage in turn activates PKA by exposing the catalytic sites of the C subunits, which can then phosphorylate an array of proteins in the cell.
In lymphocytes, the intracellular levels of cAMP increase upon antigen-receptor stimulation and even more so in response to prostaglandin E and other immunosuppression agents. In this case, cAMP serves to inhibit immunity players. PKA type I colocalizes with the T-cell and B-cell antigen receptors and causes inhibition of T- and B-cell activation. PKA has even been highlighted as a direct inducer of genes contributing to immunosuppression.
Additionally, the cAMP pathway also interacts with the MAPK pathway in a more indirect manner through its interaction with hematopoietic PTPase (HePTP). HePTP is expressed in all leukocytes. When overexpressed in T-cells, HePTP reduces the transcriptional activation of the interleukin-2 promoter typically induced by the activated T-cell receptor through a MAPK signaling cascade. The way that HePTP effectively inhibits the MAPK signaling is by interacting with the MAP kinases Erk1, Erk2, and p38 through a short sequence in HePTP's non-catalytic N terminus termed the kinase interaction motif (KIM)., The highly-specific binding of Erk and p38 to this subunit of HePTP results in rapid inactivation of the signaling cascade (see figure 3).
Yet, since both HePTP and Erk are cytosolic enzymes, it is reasonable to conclude that there exists a mechanism for the inhibition of Erk by HePTP to cease in order to allow for the translocation of activated Erk to the nucleus. Indeed, like in many other cases of protein-protein interaction, HePTP appears to be phosphorylated by Erk and p38 at the sites Thr45 and Ser72. Importantly though, a third phosphorylation site in the non-catalytic N terminus (the KIM region) of HePTP has been found—one that is phosphorylated to a much higher stoichiometry by the cAMP pathway, in yet another instance of crosstalk between the cAMP and MAPK pathways.
Phosphorylation of this third site by PKAs from the cAMP pathway inhibits binding of MAP kinases to HePTP and thereby upregulates the MAPK/ERK signaling cascade. The MAPK pathway, through Ras, Raf, Mek, and Erk, shows low activity in the presence of unphosphorylated (active) HePTP. However, activation the cAMP pathway stimulates the activation of PKA, which in turn phosphorylates HePTP at Ser23. This prevents HePTP from binding to Erk and frees the MAPK pathway from inhibition, allowing downstream signaling to continue (see figure 4).
Moreover, studies involving smooth muscle cells from the atrium of the heart have shown that PKA can reduce the activation of MAP kinases in response to platelet-derived growth factor (PDGF) by phosphorylating the kinase c-Raf. Thus, it seems plausible that PKA in the cAMP pathway could even be further involved in the regulation of lymphocyte activation not only by inhibiting the antigen-receptor MAPK signal pathway at its final stage, but even further upstream. | 1 | Biochemistry |
Because of their low vapour pressure, PCBs accumulate primarily in the hydrosphere, despite their hydrophobicity, in the organic fraction of soil, and in organisms including the human body. The hydrosphere is the main reservoir. The immense volume of water in the oceans is still capable of dissolving a significant quantity of PCBs.
As the pressure of ocean water increases with depth, PCBs become heavier than water and sink to the deepest ocean trenches where they are concentrated. | 2 | Environmental Chemistry |
Eukaryotic RNA must undergo a series of modifications in order to be exported from the nucleus and successfully translated into function proteins, many of which are dependent on mRNA capping, the first mRNA modification to take place. 5 capping is essential for mRNA stability, enhancing mRNA processing, mRNA export and translation. After successful capping, an additional phosphorylation event initiates the recruitment of machinery necessary for RNA splicing, a process by which introns are removed to produce a mature mRNA. The addition of the cap onto mRNA confers protection to the transcript from exonucleases that degrade unprotected RNA and assist in the nuclear export transport process so that the mRNA can be translated to form proteins. The function of the 5 cap is essential to the ultimate expression of the RNA. | 1 | Biochemistry |
Combustion spraying equipment produces an intense flame, which may have a peak temperature more than 3,100 °C and is very bright. Electric arc spraying produces ultra-violet light which may damage delicate body tissues. Plasma also generates quite a lot of UV radiation, easily burning exposed skin and can also cause "flash burn" to the eyes. Spray booths and enclosures should be fitted with ultra-violet absorbent dark glass. Where this is not possible, operators, and others in the vicinity should wear protective goggles containing BS grade 6 green glass. Opaque screens should be placed around spraying areas. The nozzle of an arc pistol should never be viewed directly unless it is certain that no power is available to the equipment. | 8 | Metallurgy |
Neculai Costăchescu (18 February 1876–14 July 1939) was a Romanian chemist and politician.
Born in Huși, he obtained a degree in physics and chemistry from Iași University in 1901. Costăchescu earned a doctorate from the same institution in 1905, with a thesis on the gases found in Romanias salt deposits and muddy volcanoes; he was the universitys first doctor in chemistry. He took specialty courses at the University of Zurich from 1906 to 1908, then was hired as professor of mineral chemistry at the Iași science faculty in 1912. There, he set up an organic chemistry laboratory. Thanks to his scientific activity, he was elected a corresponding member of the Romanian Academy in 1925, and was granted honorary membership in 1936.
Costăchescu entered politics in December 1918, at the close of World War I, and was a founding member of the Peasants Party, serving as vice president until its 1926 merger with the Romanian National Party to form the National Peasants Party (PNȚ). A prominent member of the latter, he was elected senator in 1926 and deputy in 1928. Between November 1928 and April 1931, he served as Public Instruction Minister in the PNȚ cabinets of Iuliu Maniu and Gheorghe Mironescu. He was Senate President from August 1932 to November 1933.
Costăchescu contributed to a number of specialized publications in Iași, such as Annales scientifiques de la Université de Jassy and Revista științifică V. Adamachi. His works included Fluosels de cobalt et de nikel (1911), Sels complexes de fer (1912) and Fluorures complexes de chrôme (1912–14). | 0 | Organic Chemistry |
Iron ore in the form of siderite, commonly known as iron stone or historically as mine, occurs in patches or bands in the Cretaceous clays of the Weald. Differing qualities of ore were extracted and mixed by experienced smelters to give the best results. Sites of opencast quarries survive from the pre-Roman and Roman eras, but medieval ore extraction was mainly done by digging a series of minepits about five metres in diameter and up to twelve metres deep with material being winched up in baskets suspended from a wooden tripod. This was less destructive of the land as spoil from one pit was used to backfill the previous pit allowing continued land use.
The fuel for smelting was charcoal, which needed to be produced as close as possible to the smelting sites because it would crumble to dust if transported far by cart over rough tracks. Wood was also needed for pre-roasting the ore on open fires, a process which broke down the lumps or nodules and converted the carbonate into oxide. Large areas of woodland were available in the Weald and coppicing woodlands could provide a sustainable source of wood. Sustainable charcoal production for a post-medieval blast furnace required the timber production from a radius of a furnace in a landscape that was a quarter to a third wooded. Forging and finishing of the iron from bloomeries and blast furnaces also required large quantities of charcoal and was usually carried out at a separate site.
Water power became important with the introduction of blast furnaces and finery forges in the late medieval period. Blast furnaces needed to operate continuously for as long as possible and a series of ponds were often created in a valley to give a sustainable flow for the waterwheel. A campaign, as the production run was known, usually ran from October through to late spring when streams began to dry up, although Lamberhurst Furnace driven by the River Teise ran continuously for more than three years in the 1740s. Finery forges with three or four waterwheels to drive bellows and hammers needed more water than a furnace at times, although continuity was not as important. They tended to be sited downstream from a furnace if they were in the same valley. Ponds were created by building a dam known as a pond bay, which often served as a road, across one of the many valleys in the undulating Wealden landscape. In 1754 one furnace was so drought-stricken that its manager considered hiring workmen to turn the wheel as a treadmill. This need for continuous water power was an incentive in the development of the water-returning engine, a waterwheel driven by water raised by a steam engine pump. | 8 | Metallurgy |
Translation promotes transcription elongation and regulates transcription termination. Functional coupling between transcription and translation is caused by direct physical interactions between the ribosome and RNA polymerase ("expressome complex"), ribosome-dependent changes to nascent mRNA secondary structure which affect RNA polymerase activity (e.g. "attenuation"), and ribosome-dependent changes to nascent mRNA availability to transcription termination factor Rho ("polarity"). | 1 | Biochemistry |
Most of the alkaloids have a tertiary amine group, so the explanation for color reaction could be the following:
:( = anions of acid)
Then the insoluble complex salt is formed from the reaction between ammonium salt and potassium tetraiodobismuthate.
This ion pair has different colors: yellow, orange, red, and brown, which depend on the nature of alkaloids. | 3 | Analytical Chemistry |
ClSOOH is used to prepare alkyl sulfates, which are useful as detergents and as chemical intermediates:
:ROH + ClSOH → ROSOH + HCl
An early synthesis of saccharin begins with the reaction of toluene with ClSOOH to give the ortho- and para-toluenesulfonyl chloride derivatives:
:CHCH + 2 ClSOOH → CHCHSOCl + HSO + HCl
Oxidation of the ortho isomer gives the benzoic acid derivative that then is cyclized with ammonia and neutralized with base to afford saccharin.
Reaction with hydrogen peroxide is used to produce peroxydisulfuric acid ("persulfuric acid") and peroxydisulfates. These are used as oxidizing agents and for initiating free radical polymerization, for example to produce polytetrafluoroethylene (Teflon).
Chlorosulfonic acid has been used as an anti-contrail agent in Ryan Model 147 reconnaissance drones, and to produce smoke screens. | 0 | Organic Chemistry |
An inverted repeat (or IR) is a single stranded sequence of nucleotides followed downstream by its reverse complement. The intervening sequence of nucleotides between the initial sequence and the reverse complement can be any length including zero. For example, is an inverted repeat sequence. When the intervening length is zero, the composite sequence is a palindromic sequence.
Both inverted repeats and direct repeats constitute types of nucleotide sequences that occur repetitively. These repeated DNA sequences often range from a pair of nucleotides to a whole gene, while the proximity of the repeat sequences varies between widely dispersed and simple tandem arrays. The short tandem repeat sequences may exist as just a few copies in a small region to thousands of copies dispersed all over the genome of most eukaryotes. Repeat sequences with about 10–100 base pairs are known as minisatellites, while shorter repeat sequences having mostly 2–4 base pairs are known as microsatellites. The most common repeats include the dinucleotide repeats, which have the bases AC on one DNA strand, and GT on the complementary strand. Some elements of the genome with unique sequences function as exons, introns and regulatory DNA. Though the most familiar loci of the repetitive sequences are the centromere and the telomere, a large portion of the repeated sequences in the genome are found among the noncoding DNA.
Inverted repeats have a number of important biological functions. They define the boundaries in transposons and indicate regions capable of self-complementary base pairing (regions within a single sequence which can base pair with each other). These properties play an important role in genome instability and contribute not only to cellular evolution and genetic diversity but also to mutation and disease. In order to study these effects in detail, a number of programs and databases have been developed to assist in discovery and annotation of inverted repeats in various genomes. | 1 | Biochemistry |
Acquired conditions in which mitochondrial dysfunction has been involved are:
* diabetes
* Huntington's disease
* cancer
* Alzheimer's disease,
* Parkinson's disease
* bipolar disorder, schizophrenia, aging and senescence, anxiety disorders
* cardiovascular disease
* sarcopenia
* chronic fatigue syndrome
* ALS
The body, and each mutation, is modulated by other genome variants; the mutation that in one individual may cause liver disease might in another person cause a brain disorder. The severity of the specific defect may also be great or small. Some defects include exercise intolerance. Defects often affect the operation of the mitochondria and multiple tissues more severely, leading to multi-system diseases.
It has also been reported that drug tolerant cancer cells have an increased number and size of mitochondria, which suggested an increase in mitochondrial biogenesis. Interestingly, a recent study in Nature Nanotechnology has reported that cancer cells can hijack the mitochondria from immune cells via physical tunneling nanotubes.
As a rule, mitochondrial diseases are worse when the defective mitochondria are present in the muscles, cerebrum, or nerves, because these cells use more energy than most other cells in the body.
Although mitochondrial diseases vary greatly in presentation from person to person, several major clinical categories of these conditions have been defined, based on the most common phenotypic features, symptoms, and signs associated with the particular mutations that tend to cause them.
An outstanding question and area of research is whether ATP depletion or reactive oxygen species are in fact responsible for the observed phenotypic consequences.
Cerebellar atrophy or hypoplasia has sometimes been reported to be associated. | 1 | Biochemistry |
Speisses are alloys of heavy metals like iron, cobalt, nickel and copper with arsenic, antimony and, occasionally, tin. The latter elements lower the melting point to around 1000 °C. Speisses commonly occur in lead smelting operations and copper smelting operations.
Speisses are only partially miscible with mattes, and if there is enough arsenic or antimony in the copper feed to a matte smelting furnace, a separate speiss melt can form. Speisses show high affinities for platinum group metals and gold. The mass concentration of platinum group metals in the speiss phase is about 1000 times that of the concentration in the matte phase, while the ratio for gold is about 100 times.
Speisses are also immiscible in liquid lead and flow out of lead blast furnaces as a separate phase. | 8 | Metallurgy |
Some molecular tweezers bind aromatic guests. These molecular tweezers consist of a pair of anthracene arms held at a distance that allows aromatic guests to gain π–π interactions from both (see Figure). Other molecular tweezers feature a pair of tethered porphyrins.
Yet another type of molecular tweezers bind fullerenes. Such "buckycatchers" are composed of two corannulene pincers that complement the surface of the convex fullerene guest (Figure 2). An association constant (K) of 8,600 M was calculated using H NMR spectroscopy.
Stoermer and co-workers described clefts capable of capturing cyclohexane or chloroform molecules. Intriguingly, pi interactions played key roles in guest capture as well as cleft formation rate.
Water-soluble phosphate-substituted molecular tweezers made of alternating phenyl and norbornenyl substituents bind to positively charged aliphatic side chains of basic amino acids, such as lysine and arginine (Figure 3). Similar compounds called "molecular clips", whose side walls are flat rather than convex, prefer to enclose flat pyridinium rings (for example the nicotinamide ring of NAD(P)+) between their plane naphthalene sidewalls (Figure 4). These mutually exclusive binding modes make these compounds valuable tools for probing critical biological interactions of basic amino acid side chains in peptides and proteins as well as of NAD(P) and similar cofactors. For example, both types of compounds inhibit the oxidation reactions of ethanol by alcohol dehydrogenase or of glucose-6-phosphate by glucose-6-phosphate dehydrogenase, respectively.
The molecular tweezers, but not the clips, efficiently inhibit the formation of toxic oligomers and aggregates by amyloidogenic proteins associated with different diseases. Examples include the proteins involved in Alzheimers disease – amyloid β-protein (Aβ) and tau; α-synuclein, which is thought to cause Parkinsons disease and other synucleinopathies and is involved in spinal-cord injury; mutant huntingtin, which causes Huntington's disease; islet amyloid polypeptide (amylin), which kills pancreatic β-cells in type-2 diabetes; transthyretin (TTR), which causes familial amyloid polyneuropathy, familial amyloid cardiomyopathy, and senile systemic amyloidosis; aggregation-prone mutants of the tumor-suppressor protein p53; and semen proteins whose aggregation enhances HIV infection. Importantly, the molecular tweezers have been found to be effective and safe not only in the test tube but also in animal models of different diseases, suggesting that they may be developed as drugs against diseases caused by abnormal protein aggregation, all of which currently have no cure. They were also shown to destroy the membranes of enveloped viruses, such as HIV, herpes, and hepatitis C, which makes them good candidates for development of microbicides.
The above examples show the potential reactivity and specificity of these molecules. The binding cavity between the side arms of the tweezer can evolve to bind to an appropriate guest with high specificity, depending on the configuration of the tweezer. That makes this overall class of macromolecule truly synthetic molecular receptors with important application to biology and medicine. | 6 | Supramolecular Chemistry |
Quantum efficiency (QE) is the fraction of photon flux that contributes to the photocurrent in a photodetector or
a pixel. Quantum efficiency is one of the most important parameters used to evaluate the quality of a detector and is often called the spectral response to reflect its wavelength dependence. It is defined as the number of signal electrons created per incident photon. In some cases it can exceed 100% (i.e. when more than one electron is created per incident photon). | 7 | Physical Chemistry |
Up-regulated expression of genes in mammals can be initiated when signals are transmitted to the promoters associated with the genes. Cis-regulatory DNA sequences that are located in DNA regions distant from the promoters of genes can have very large effects on gene expression, with some genes undergoing up to 100-fold increased expression due to such a cis-regulatory sequence. These cis-regulatory sequences include enhancers, silencers, insulators and tethering elements. Among this constellation of sequences, enhancers and their associated transcription factor proteins have a leading role in the regulation of gene expression.
Enhancers are sequences of the genome that are major gene-regulatory elements. Enhancers control cell-type-specific gene expression programs, most often by looping through long distances to come in physical proximity with the promoters of their target genes. In a study of brain cortical neurons, 24,937 loops were found, bringing enhancers to promoters. Multiple enhancers, each often at tens or hundred of thousands of nucleotides distant from their target genes, loop to their target gene promoters and coordinate with each other to control expression of their common target gene.
The schematic illustration in this section shows an enhancer looping around to come into close physical proximity with the promoter of a target gene. The loop is stabilized by a dimer of a connector protein (e.g. dimer of CTCF or YY1), with one member of the dimer anchored to its binding motif on the enhancer and the other member anchored to its binding motif on the promoter (represented by the red zigzags in the illustration). Several cell function specific transcription factor proteins (in 2018 Lambert et al. indicated there were about 1,600 transcription factors in a human cell) generally bind to specific motifs on an enhancer and a small combination of these enhancer-bound transcription factors, when brought close to a promoter by a DNA loop, govern the level of transcription of the target gene. Mediator (coactivator) (a complex usually consisting of about 26 proteins in an interacting structure) communicates regulatory signals from enhancer DNA-bound transcription factors directly to the RNA polymerase II (RNAP II) enzyme bound to the promoter.
Enhancers, when active, are generally transcribed from both strands of DNA with RNA polymerases acting in two different directions, producing two eRNAs as illustrated in the Figure. An inactive enhancer may be bound by an inactive transcription factor. Phosphorylation of the transcription factor may activate it and that activated transcription factor may then activate the enhancer to which it is bound (see small red star representing phosphorylation of a transcription factor bound to an enhancer in the illustration). An activated enhancer begins transcription of its RNA before activating a promoter to initiate transcription of messenger RNA from its target gene. | 1 | Biochemistry |
Yttrium is used in the production of a large variety of synthetic garnets, and yttria is used to make yttrium iron garnets (, also "YIG"), which are very effective microwave filters which were recently shown to have magnetic interactions more complex and longer-ranged than understood over the previous four decades. Yttrium, iron, aluminium, and gadolinium garnets (e.g. and ) have important magnetic properties. YIG is also very efficient as an acoustic energy transmitter and transducer. Yttrium aluminium garnet ( or YAG) has a hardness of 8.5 and is also used as a gemstone in jewelry (simulated diamond). Cerium-doped yttrium aluminium garnet (YAG:Ce) crystals are used as phosphors to make white LEDs.
YAG, yttria, yttrium lithium fluoride (), and yttrium orthovanadate () are used in combination with dopants such as neodymium, erbium, ytterbium in near-infrared lasers. YAG lasers can operate at high power and are used for drilling and cutting metal. The single crystals of doped YAG are normally produced by the Czochralski process. | 8 | Metallurgy |
Quantum logic spectroscopy (QLS) is an ion control scheme that maps quantum information between two co-trapped ion species. Quantum logic operations allow desirable properties of each ion species to be utilized simultaneously. This enables work with ions and molecular ions that have complex internal energy level structures which preclude laser cooling and direct manipulation of state. QLS was first demonstrated by NIST in 2005. QLS was first applied to state detection in diatomic molecules in 2016 by Wolf et al, and later applied to state manipulation and detection of diatomic molecules by the Liebfried group at NIST in 2017 | 7 | Physical Chemistry |
In environmental terms, the residence time definition is adapted to fit with ground water, the atmosphere, glaciers, lakes, streams, and oceans. More specifically it is the time during which water remains within an aquifer, lake, river, or other water body before continuing around the hydrological cycle. The time involved may vary from days for shallow gravel aquifers to millions of years for deep aquifers with very low values for hydraulic conductivity. Residence times of water in rivers are a few days, while in large lakes residence time ranges up to several decades. Residence times of continental ice sheets is hundreds of thousands of years, of small glaciers a few decades.
Ground water residence time applications are useful for determining the amount of time it will take for a pollutant to reach and contaminate a ground water drinking water source and at what concentration it will arrive. This can also work to the opposite effect to determine how long until a ground water source becomes uncontaminated via inflow, outflow, and volume. The residence time of lakes and streams is important as well to determine the concentration of pollutants in a lake and how this may affect the local population and marine life.
Hydrology, the study of water, discusses the water budget in terms of residence time. The amount of time that water spends in each different stage of life (glacier, atmosphere, ocean, lake, stream, river), is used to show the relation of all of the water on the earth and how it relates in its different forms. | 9 | Geochemistry |
This enzyme is often listed in medical literature under incorrect name "creatinine kinase". Creatinine is not a substrate or a product of the enzyme. | 1 | Biochemistry |
Agmatine produces mild reductions in heart rate and blood pressure, apparently by activating both central and peripheral control systems via modulation of several of its molecular targets including: imidazoline receptors subtypes, norepinephrine release and NO production. | 1 | Biochemistry |
Dielectric relaxation as a whole is the result of the movement of dipoles (dipole relaxation) and electric charges (ionic relaxation) due to an applied alternating field, and is usually observed in the frequency range 10-10 Hz. Relaxation mechanisms are relatively slow compared to resonant electronic transitions or molecular vibrations, which usually have frequencies above 10 Hz. | 7 | Physical Chemistry |
In photonics, band gaps or stop bands are ranges of photon frequencies where, if tunneling effects are neglected, no photons can be transmitted through a material. A material exhibiting this behaviour is known as a photonic crystal. The concept of hyperuniformity has broadened the range of photonic band gap materials, beyond photonic crystals. By applying the technique in supersymmetric quantum mechanics, a new class of optical disordered materials has been suggested, which support band gaps perfectly equivalent to those of crystals or quasicrystals.
Similar physics applies to phonons in a phononic crystal. | 7 | Physical Chemistry |
Recently, photoredox catalysis has been applied to biocatalysis, enabling unique, previously inaccessible transformations. Photoredox chemistry relies upon light to generate free radical intermediates. These radical intermediates are achiral thus racemic mixtures of product are obtained when no external chiral environment is provided. Enzymes can provide this chiral environment within the active site and stabilize a particular conformation and favoring formation of one, enantiopure product. Photoredox enabled biocatalysis reactions fall into two categories:
# Internal coenzyme/cofactor photocatalyst
# External photocatalyst
Certain common hydrogen atom transfer (HAT) cofactors (NADPH and Flavin) can operate as single electron transfer (SET) reagents. Although these species are capable of HAT without irradiation, their redox potentials are enhance by nearly 2.0 V upon visible light irradiation. When paired with their respective enzymes (typically ene-reductases) This phenomenon has been utilized by chemists to develop enantioselective reduction methodologies. For example medium sized lactams can be synthesized in the chiral environment of an ene-reductase through a reductive, baldwin favored, radical cyclization terminated by enantioselective HAT from NADPH.
The second category of photoredox enabled biocatalytic reactions use an external photocatalyst (PC). Many types of PCs with a large range of redox potentials can be utilized, allowing for greater tunability of reactive compared to using a cofactor. Rose bengal, and external PC, was utilized in tandem with an oxidoreductase to enantioselectively deacylate medium sized alpha-acyl-ketones.
Using an external PC has some downsides. For example, external PCs typically complicate reaction design because the PC may react with both the bound and unbound substrate. If a reaction occurs between the unbound substrate and the PC, enantioselectivity is lost and other side reactions may occur. | 0 | Organic Chemistry |
In 2010, CDP was called "The most powerful green NGO you've never heard of" by the Harvard Business Review. In 2012 it won the Zayed Future Energy Prize. | 2 | Environmental Chemistry |
Several key technologies are used for the production of fine chemicals, including
*Chemical synthesis, either from petrochemical starting materials or from natural products extracts
*Biotechnology, for small molecules biocatalysis (enzymatic methods), biosynthesis (fermentation), and, for big molecules, cell culture technology
*Extraction from animals, microorganisms, or plants; isolation and purification, used, for example, for alkaloids, antibacterials (especially penicillins), and steroids
*Hydrolysis of proteins, especially when combined with ion exchange chromatography, used, for instance, for amino acids
Chemical synthesis and biotechnology are most frequently used; sometimes also in combination. | 0 | Organic Chemistry |
Some fisheye lenses use a stereographic projection to capture a wide-angle view. Compared to more traditional fisheye lenses which use an equal-area projection, areas close to the edge retain their shape, and straight lines are less curved. However, stereographic fisheye lenses are typically more expensive to manufacture. Image remapping software, such as Panotools, allows the automatic remapping of photos from an equal-area fisheye to a stereographic projection.
The stereographic projection has been used to map spherical panoramas, starting with Horace Bénédict de Saussures in 1779. This results in effects known as a little planet (when the center of projection is the nadir) and a tube' (when the center of projection is the zenith).
The popularity of using stereographic projections to map panoramas over other azimuthal projections is attributed to the shape preservation that results from the conformality of the projection. | 3 | Analytical Chemistry |
The effective overall energy unit for the available body energy is referred to as the daily glycogen generation capacity, and is used to compare the mitochondrial output of affected or chronically glycogen-depleted individuals to healthy individuals. This value is slow to change in a given individual, as it takes between 18 and 24 months to complete a full cycle.
The glycogen generation capacity is entirely dependent on, and determined by, the operating levels of the mitochondria in all of the cells of the human body; however, the relation between the energy generated by the mitochondria and the glycogen capacity is very loose and is mediated by many biochemical pathways. The energy output of full healthy mitochondrial function can be predicted exactly by a complicated theoretical argument, but this argument is not straightforward, as most energy is consumed by the brain and is not easily measurable. | 1 | Biochemistry |
Bismuth polycations form despite the fact that they possess fewer total valence electrons than would seem necessary for the number of sigma bonds. The shapes of these clusters are generally dictated by Wade's rules, which are based on the treatment of the electronic structure as delocalized molecular orbitals. The bonding can also be described with three-center two-electron bonds in some cases, such as the cluster.
Bismuth clusters have been observed to act as ligands for copper and ruthenium ions. This behavior is possible due to the otherwise fairly inert lone pairs on each of the bismuth that arise primarily from the s-orbitals left out of Bi–Bi bonding. | 7 | Physical Chemistry |
Reactions of relatively simple coordination complexes have been examined as tests of PCET.
*The comproportionation of a Ru(II) aquo and a Ru(IV) oxo (bipy = (2,2'-bipyridine, py = pyridine):
:[(bipy)(py)Ru(O)] + [(bipy)(py)Ru(OH)] → 2 [(bipy)(py)Ru(OH)]
*Electrochemical reactions where reduction is coupled to protonation or where oxidation is coupled to deprotonation. | 7 | Physical Chemistry |
The AFLP technology has the capability to detect various polymorphisms in different genomic regions simultaneously. It is also highly sensitive and reproducible. As a result, AFLP has become widely used for the identification of genetic variation in strains or closely related species of plants, fungi, animals, and bacteria. The AFLP technology has been used in criminal and paternity tests, also to determine slight differences within populations, and in linkage studies to generate maps for quantitative trait locus (QTL) analysis.
There are many advantages to AFLP when compared to other marker technologies including randomly amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP), and microsatellites. AFLP not only has higher reproducibility, resolution, and sensitivity at the whole genome level compared to other techniques, but it also has the capability to amplify between 50 and 100 fragments at one time. In addition, no prior sequence information is needed for amplification (Meudt & Clarke 2007). As a result, AFLP has become extremely beneficial in the study of taxa including bacteria, fungi, and plants, where much is still unknown about the genomic makeup of various organisms.
The AFLP technology is covered by patents and patent applications of Keygene N.V. AFLP is a registered trademark of Keygene N.V. | 1 | Biochemistry |
In this group of mechanisms, the strain is accommodated by migration of vacancies in crystallographic lattice. This results in a change in crystal shape involving the transfer of mass by diffusion. These migrations are oriented towards sites of maximum stress and are limited by the grain boundaries; which conditions a crystallographic shape fabric or strain. The result is a more perfect crystal. This process is grain-size sensitive and occurs at low strain rates or very high temperatures, and is accommodated by migration of lattice defects from areas of low to those of high compressive stress. The main mechanisms of diffusive mass transfer are Nabarro-Herring creep, Coble creep, and pressure solution.
Nabarro–herring creep, or volume diffusion, acts at high homologous temperatures and is grain size dependent with the strain-rate inversely proportional to the square of the grain size (creep rate decreases as the grain size increases). During Nabarro-Herring creep, the diffusion of vacancies occurs through the crystal lattice (microtectonics), which causes grains to elongate along the stress axis. Nabarro-Herring creep has a weak stress dependence.
Coble creep, or grain-boundary diffusion, is the diffusion of vacancies occurs along grain-boundaries to elongate the grains along the stress axis. Coble creep has a stronger grain-size dependence than Nabarro–Herring creep, and occurs at lower temperatures while remaining temperature dependent. It play a more important role than Nabarro–Herring creep and is more important in the deformation of the plastic crust. | 8 | Metallurgy |
AGEs have a range of pathological effects, such as:
* Increased vascular permeability.
* Increased arterial stiffness
* Inhibition of vascular dilation by interfering with nitric oxide.
* Oxidizing LDL.
* Binding cells—including macrophage, endothelial, and mesangial—to induce the secretion of a variety of cytokines.
* Enhanced oxidative stress.
* Hemoglobin-AGE levels are elevated in diabetic individuals and other AGE proteins have been shown in experimental models to accumulate with time, increasing from 5-50 fold over periods of 5–20 weeks in the retina, lens and renal cortex of diabetic rats. The inhibition of AGE formation reduced the extent of nephropathy in diabetic rats. Therefore, substances that inhibit AGE formation may limit the progression of disease and may offer new tools for therapeutic interventions in the therapy of AGE-mediated disease.
* AGEs have specific cellular receptors; the best-characterized are those called RAGE. The activation of cellular RAGE on endothelium, mononuclear phagocytes, and lymphocytes triggers the generation of free radicals and the expression of inflammatory gene mediators. Such increases in oxidative stress lead to the activation of the transcription factor NF-κB and promote the expression of NF-κB regulated genes that have been associated with atherosclerosis. | 1 | Biochemistry |
In the study of plants' photorespiration, the labeling of atmosphere by oxygen-18 allows for the measurement of oxygen uptake by the photorespiration pathway. Labeling by gives the unidirectional flux of uptake, while there is a net photosynthetic evolution. It was demonstrated that, under preindustrial atmosphere, most plants reabsorb, by photorespiration, half of the oxygen produced by photosynthesis. Then, the yield of photosynthesis was halved by the presence of oxygen in atmosphere. | 9 | Geochemistry |
Gilbert Stork (December 31, 1921 – October 21, 2017) was an organic chemist. For a quarter of a century he was the Eugene Higgins Professor of Chemistry Emeritus at Columbia University. He is known for making significant contributions to the total synthesis of natural products, including a lifelong fascination with the synthesis of quinine. In so doing he also made a number of contributions to mechanistic understanding of reactions, and performed pioneering work on enamine chemistry, leading to development of the Stork enamine alkylation.
It is believed he was responsible for the first planned stereocontrolled synthesis as well as the first natural product to be synthesised with high stereoselectivity.
Stork was also an accomplished mentor of young chemists and many of his students have gone on to make significant contributions in their own right. | 0 | Organic Chemistry |
Primary ketimines can be synthesized via a Grignard reaction with a nitrile. This method is known as Moureu-Mignonac ketimine synthesis. For example, benzophenone imine can also be synthesized by addition of phenylmagnesium bromide to benzonitrile followed by careful hydrolysis (lest the imine be hydrolyzed):
:CHCN + CHMgBr → (CH)C=NMgBr
:(CH)C=NMgBr + HO → (CH)C=NH + MgBr(OH) | 0 | Organic Chemistry |
*Post-translational modification of proteins in proteins generated by cell-free protein synthesis is still limited compared to the traditional methods, and may not be as biologically relevant. | 1 | Biochemistry |
GABA receptor antagonists are drugs that inhibit the action of GABA. In general these drugs produce stimulant and convulsant effects, and are mainly used for counteracting overdoses of sedative drugs.
Examples include bicuculline, securinine and metrazol, and the benzodiazepine GABA receptor antagonist flumazenil.
Other agents which may have GABA receptor antagonism include the antibiotic ciprofloxacin, tranexamic acid, thujone, ginkgo biloba, and kudzu. | 1 | Biochemistry |
Segregation of a solute to surfaces and grain boundaries in a solid produces a section of material with a discrete composition and its own set of properties that can have important (and often deleterious) effects on the overall properties of the material. These zones with an increased concentration of solute can be thought of as the cement between the bricks of a building. The structural integrity of the building depends not only on the material properties of the brick, but also greatly on the properties of the long lines of mortar in between.
Segregation to grain boundaries, for example, can lead to grain boundary fracture as a result of temper brittleness, creep embrittlement, stress relief cracking of weldments, hydrogen embrittlement, environmentally assisted fatigue, grain boundary corrosion, and some kinds of intergranular stress corrosion cracking. A very interesting and important field of study of impurity segregation processes involves AES of grain boundaries of materials. This technique includes tensile fracturing of special specimens directly inside the UHV chamber of the Auger Electron Spectrometer that was developed by Ilyin.
Segregation to grain boundaries can also affect their respective migration rates, and so affects sinterability, as well as the grain boundary diffusivity (although sometimes these effects can be used advantageously).
Segregation to free surfaces also has important consequences involving the purity of metallurgical samples. Because of the favorable segregation of some impurities to the surface of the material, a very small concentration of impurity in the bulk of the sample can lead to a very significant coverage of the impurity on a cleaved surface of the sample. In applications where an ultra-pure surface is needed (for example, in some nanotechnology applications), the segregation of impurities to surfaces requires a much higher purity of bulk material than would be needed if segregation effects did not exist. The following figure illustrates this concept with two cases in which the total fraction of impurity atoms is 0.25 (25 impurity atoms in 100 total). In the representation on the left, these impurities are equally distributed throughout the sample, and so the fractional surface coverage of impurity atoms is also approximately 0.25. In the representation to the right, however, the same number of impurity atoms are shown segregated on the surface, so that an observation of the surface composition would yield a much higher impurity fraction (in this case, about 0.69). In fact, in this example, were impurities to completely segregate to the surface, an impurity fraction of just 0.36 could completely cover the surface of the material. In an application where surface interactions are important, this result could be disastrous.
While the intergranular failure problems noted above are sometimes severe, they are rarely the cause of major service failures (in structural steels, for example), as suitable safety margins are included in the designs. Perhaps the greater concern is that with the development of new technologies and materials with new and more extensive mechanical property requirements, and with the increasing impurity contents as a result of the increased recycling of materials, we may see intergranular failure in materials and situations not seen currently. Thus, a greater understanding of all of the mechanisms surrounding segregation might lead to being able to control these effects in the future. Modeling potentials, experimental work, and related theories are still being developed to explain these segregation mechanisms for increasingly complex systems. | 7 | Physical Chemistry |
In a colloid, the colloidal particles are said to be in sedimentation equilibrium if the rate of sedimentation is equal to the rate of movement from Brownian motion. For dilute colloids, this is described using the Laplace-Perrin distribution law:
where
is the colloidal particle volume fraction as a function of vertical distance above reference point ,
is the colloidal particle volume fraction at reference point ,
is the buoyant mass of the colloidal particles,
is the standard acceleration due to gravity,
is the Boltzmann constant,
is the absolute temperature,
and is the sedimentation length.
The buoyant mass is calculated using
where is the difference in mass density between the colloidal particles and the suspension medium, and is the colloidal particle volume found using the volume of a sphere ( is the radius of the colloidal particle). | 1 | Biochemistry |
Protein skimming removes certain organic compounds, including proteins and amino acids found in food particles and fish waste, by using the polarity of the protein itself. Due to their intrinsic charge, water-borne proteins are either repelled or attracted by the air/water interface and these molecules can be described as hydrophobic (such as fats or oils) or hydrophilic (such as salt, sugar, ammonia, most amino acids, and most inorganic compounds). However, some larger organic molecules can have both hydrophobic and hydrophilic portions. These molecules are called amphipathic or amphiphilic. Commercial protein skimmers work by generating a large air/water interface, specifically by injecting large numbers of bubbles into the water column. In general, the smaller the bubbles the more effective the protein skimming is because the surface area of small bubbles occupying the same volume is much greater than the same volume of larger bubbles. Large numbers of small bubbles present an enormous air/water interface for hydrophobic organic molecules and amphipathic organic molecules to collect on the bubble surface (the air/water interface). Water movement hastens diffusion of organic molecules, which effectively brings more organic molecules to the air/water interface and lets the organic molecules accumulate on the surface of the air bubbles. This process continues until the interface is saturated, unless the bubble is removed from the water or it bursts, in which case the accumulated molecules release back into the water column. However, it is important to note that further exposure of a saturated air bubble to organic molecules may continue to result in changes as compounds that bind more strongly may replace those molecules with a weaker binding that have already accumulated on the interface. Although some aquarists believe that increasing the contact time (or dwell time as it is sometimes called) is always good, it is incorrect to claim that it is always better to increase the contact time between bubbles and the aquarium water. As the bubbles increase near the top of the protein skimmer water column, they become denser and the water begins to drain and create the foam that will carry the organic molecules to the skimmate collection cup or to a separate skimmate waste collector and the organic molecules, and any inorganic molecules that may have become bound to the organic molecules, will be exported from the water system.
In addition to the proteins removed by skimming, there are a number of other organic and inorganic molecules that are typically removed. These include a variety of fats, fatty acids, carbohydrates, metals such as copper, and trace elements such as iodine. Particulates, phytoplankton, bacteria, and detritus are also removed; this is desired by some aquarists, and is often enhanced by placement of the skimmer before other forms of filtration, lessening the burden on the filtration system as a whole. There is at least one published study that provides a detailed list of the export products removed by the skimmer. Aquarists who keep filter-feeding invertebrates, however, sometimes prefer to keep these particulates in the water to serve as natural food.
Protein skimmers are used to harvest algae and phytoplankton gently enough to maintain viability for culturing or commercial sale as live cultures.
Alternative forms of water filtration have recently come into use, including the algae scrubber, which leaves food particles in the water for corals and small fish to consume, but removes the noxious compounds including ammonia, nitrite, nitrate, and phosphate that protein skimmers do not remove. | 3 | Analytical Chemistry |
No single method can assess impact of contamination-induced degradation of sediment across aquatic communities. Methods of each component of the triad should be selected for efficacy and relevance in lab and field tests. Application of the SQT is typically location-specific and can be used to compare differences in sediment quality temporally or across regions (Chapman, 1997). | 2 | Environmental Chemistry |
CSMBLM publishes the scientific journal Biochemia Medica in the English language three times a year. It is included in databases such as Current Contents (Clinical Medicine), Medline, PubMed Central (PMC), Science Citation Index Expanded™ (SCIE, Thomson Reuters), Journal Citation Reports/Science Edition (JCR, Thomson Reuters), EMBASE/Excerpta Medica, Scopus, CAS (Chemical Abstracts Service), EBSCO/Academic Search Complete and DOAJ (Directory of Open Access Journals). | 1 | Biochemistry |
Non-expendable mold casting differs from expendable processes in that the mold need not be reformed after each production cycle. This technique includes at least four different methods: permanent, die, centrifugal, and continuous casting. This form of casting also results in improved repeatability in parts produced and delivers near net shape results. | 8 | Metallurgy |
The ada gene has regulatory and repair activities, both really close to each other. For the regulation to occur, the ada protein must be activated, which is a consequence of the DNA repair activity. | 1 | Biochemistry |
To measure the rate constants, known concentrations of receptor and ligand are mixed in solution and the quantity of free receptor is repeatedly measured over time as the solution phase reaction occurs. The time course of the free receptor depletion is then fit with a standard bimolecular rate equation.
(4) dLR/dt = k∙R∙L - K∙k∙RL
where K * k has been substituted for k . | 1 | Biochemistry |
The development of metal carbonyl clusters such as Ni(CO) and Fe(CO) led quickly to the isolation of Fe(CO) and Fe(CO). Rundle and Dahl discovered that Mn(CO) featured an "unsupported" Mn-Mn bond, thereby verifying the ability of metals to bond to one another in molecules. In the 1970s, Paolo Chini demonstrated that very large clusters could be prepared from the platinum metals, one example being [Rh(CO)H]. This area of cluster chemistry has benefited from single-crystal X-ray diffraction.
Many metal carbonyl clusters contain ligands aside from CO. For example, the CO ligand can be replaced with myriad alternatives such as phosphines, isocyanides, alkenes, hydride, etc. Some carbonyl clusters contain two or more metals. Others contain carbon vertices. One example is the methylidyne-tricobalt cluster [Co(CH)(CO)]. The above-mentioned cluster serves as an example of an overall zero-charged (neutral) cluster. In addition, cationic (positively charged) rather than neutral organometallic trimolybdenum or tritungsten clusters are also known. The first representative of these ionic organometallic clusters is [Mo(CCH)(OCCH)(HO)]. | 7 | Physical Chemistry |
A large number of chemical compounds are known to exhibit one or several liquid crystalline phases. Despite significant differences in chemical composition, these molecules have some common features in chemical and physical properties. There are three types of thermotropic liquid crystals: discotic, conic (bowlic), and rod-shaped molecules. Discotics are disc-like molecules consisting of a flat core of adjacent aromatic rings, whereas the core in a conic LC is not flat, but is shaped like a rice bowl (a three-dimensional object). This allows for two dimensional columnar ordering, for both discotic and conic LCs. Rod-shaped molecules have an elongated, anisotropic geometry which allows for preferential alignment along one spatial direction.
*The molecular shape should be relatively thin, flat or conic, especially within rigid molecular frameworks.
*The molecular length should be at least 1.3 nm, consistent with the presence of long alkyl group on many room-temperature liquid crystals.
*The structure should not be branched or angular, except for the conic LC.
*A low melting point is preferable in order to avoid metastable, monotropic liquid crystalline phases. Low-temperature mesomorphic behavior in general is technologically more useful, and alkyl terminal groups promote this.
An extended, structurally rigid, highly anisotropic shape seems to be the main criterion for liquid crystalline behavior, and as a result many liquid crystalline materials are based on benzene rings. | 7 | Physical Chemistry |
The typical FCS setup consists of a laser line (wavelengths ranging typically from 405–633 nm (cw), and from 690–1100 nm (pulsed)), which is reflected into a microscope objective by a dichroic mirror. The laser beam is focused in the sample, which contains fluorescent particles (molecules) in such high dilution, that only a few are within the focal spot (usually 1–100 molecules in one fL). When the particles cross the focal volume, they fluoresce. This light is collected by the same objective and, because it is red-shifted with respect to the excitation light it passes the dichroic mirror reaching a detector, typically a photomultiplier tube, an avalanche photodiode detector or a superconducting nanowire single-photon detector. The resulting electronic signal can be stored either directly as an intensity versus time trace to be analyzed at a later point, or computed to generate the autocorrelation directly (which requires special acquisition cards). The FCS curve by itself only represents a time-spectrum. Conclusions on physical phenomena have to be extracted from there with appropriate models. The parameters of interest are found after fitting the autocorrelation curve to modeled functional forms. | 7 | Physical Chemistry |
Contraindications of drospirenone include renal impairment or chronic kidney disease, adrenal insufficiency, presence or history of cervical cancer or other progestogen-sensitive cancers, benign or malignant liver tumors or hepatic impairment, undiagnosed abnormal uterine bleeding, and hyperkalemia (high potassium levels). Renal impairment, hepatic impairment, and adrenal insufficiency are contraindicated because they increase exposure to drospirenone and/or increase the risk of hyperkalemia with drospirenone. | 4 | Stereochemistry |
In organic chemistry, the Murai reaction is an organic reaction that uses C-H activation to create a new C-C bond between a terminal or strained internal alkene and an aromatic compound using a ruthenium catalyst. The reaction, named after Shinji Murai, was first reported in 1993. While not the first example of C-H activation, the Murai reaction is notable for its high efficiency and scope. Previous examples of such hydroarylations required more forcing conditions and narrow scope. | 0 | Organic Chemistry |
Due to the experimental ease of its use, BMS has become common in hydroboration reactions. In hydroborations with BMS, the dimethylsulfide dissociates in situ, liberating diborane, which rapidly adds to the unsaturated bonds. The resulting organoborane compounds are useful intermediates in organic synthesis. Boranes add to alkenes in an anti-Markovnikov fashion and allow conversion of alkynes to the corresponding cis-alkenes. | 0 | Organic Chemistry |
Pelletizing of animal feeds can result in pellets from (shrimp feeds), through to (poultry feeds) up to (stock feeds). The pelletizing of stock feed is done with the pellet mill machinery, which is done in a feed mill. | 8 | Metallurgy |
Naturally occurring alcohol derivatives of capnellene have been isolated using simple acetone extraction from Capnella imbricata, a species of soft coral (order Alcyonacea) known as Kenya Tree Coral. Capnella is a widely distributed genus of soft coral, found primarily in the tropical reefs of Indonesia. These corals produce a variety of sterols, sesquiterpenes and diterpenes. Specifically, the capnellanol derivatives found in Capnella serve as a defense system by inhibiting the growth of microorganisms and the settlement of larvae on the coral’s surface. However, the details of this defense mechanism have not been extensively explored. Although the natural synthesis of capnellene and its derivatives is not yet understood, the sesquiterpene hydrocarbon precapnelladiene has been isolated from the same coral and research suggests that may be a biogenetic precursor. | 0 | Organic Chemistry |
Before the mission of Lunar Prospector lunar satellite, it was commonly thought that these KREEP materials had been formed in a widespread layer beneath the crust. However, the measurements from the gamma-ray spectrometer on-board this satellite showed that the KREEP-containing rocks are primarily concentrated underneath the Oceanus Procellarum and the Mare Imbrium. This is a unique lunar geological province that is now known as the Procellarum KREEP Terrane.
Basins far from this province that dug deeply into the crust (and possibly the mantle), such as the Mare Crisium, the Mare Orientale, and the South Pole–Aitken basin, show only little or no enhancements of KREEP within their rims or ejecta. The enhancement of heat-producing radioactive elements within the crust (and/or the mantle) of the Procellarum KREEP Terrane is almost certainly responsible for the longevity and intensity of mare volcanism on the nearside of the Moon. | 9 | Geochemistry |
The fraction collector is typically a rotating rack that can be filled with test tubes or similar containers. It allows samples to be collected in fixed volumes, or can be controlled to direct specific fractions detected as peaks of protein concentration, into separate containers.
Many systems include various optional components. A filter may be added between the mixer and column to minimize clogging. In large FPLC columns the sample may be loaded into the column directly using a small peristaltic pump rather than an injection loop. When the buffer contains dissolved gas, bubbles may form as pressure drops where the buffer exits the column; these bubbles create artifacts if they pass through the flow cells. This may be prevented by degassing the buffers, e.g. with a degasser, or by adding a flow restrictor downstream of the flow cells to maintain a pressure of 1-5 bar in the eluant line. | 3 | Analytical Chemistry |
By applying an additional electrode on a nanochannel as the gate electrode, it is possible to adjust the electrical potential inside the channel. A nanofluidic field-effect transistor can be made of silica nanotubes with an oxide as the dielectric material between the metal gate electrode and the channel. The tuning of the ionic current, therefore, can be achieved by changing the voltage applied on the gate. The gate bias and the source-drain bias are applied to adjust the cation and anion concentration within the nanochannel, therefore tuning the ionic current flowing through it.
This concept is an analogy to the structure of a metal-oxide semiconductor field-effect transistor (MOSFET) in electronic circuits. Similar to a MOSFET, a nanofluidic transistor is the fundamental element for building a nanofluidic circuitry. There is possibility to achieve a nanofluidic circuitry, which is capable of logic operation and manipulation for ionic particles.
Since the conductance of ionic current flow is controlled by the gate voltage, using a material with high dielectric constant as the wall of the channel is desired. In this case, there is a stronger field seen within the channel due to a higher gate capacitance. A channel surface with a low surface charge is also desired in order to strengthen the effect of potential tuning by gate electrode. This increases the ability to spatially and temporally tune the ionic and electrostatic environment in the channel. | 7 | Physical Chemistry |
The Creutz–Taube complex is a robust, readily analyzed, mixed-valence complex consisting of otherwise equivalent Ru(II) and Ru(III) centers bridged by the pyrazine. This complex serves as a model for the bridged intermediate invoked in inner-sphere electron transfer. | 7 | Physical Chemistry |
The Alternative Splicing and Transcript Diversity database (ASTD) was a database of transcript variants maintained by the European Bioinformatics Institute from 2008 to 2012. It contained transcription initiation, polyadenylation and splicing variant data. | 1 | Biochemistry |
Considering as example the decomposition of nitrogen dioxide into nitrogen monoxide and molecular oxygen:
Based on the red "line of best fit" plotted in the graph given above:
Points read from graph:
Slope of red line = (4.1 − 2.2) / (0.0015 − 0.00165) = −12,667
Intercept [y-value at x = 0] of red line = 4.1 + (0.0015 × 12667) = 23.1
Inserting these values into the form above:
yields:
as shown in the plot at the right.
for:
* k in 10 cm mol s
* T in K
Substituting for the quotient in the exponent of :
where the approximate value for R is 8.31446 J K mol
The activation energy of this reaction from these data is then: | 7 | Physical Chemistry |
Early items designed and produced by Friedrich Deusch are very classical, and this was followed by an abstract phase of Art Déco in its purest form. From the 1950s, it was more a concrete style with flowers and so forth. Deusch applied silver overlay to vases, plates, coffee and tea services, and other items.
From the outset, the firm of Alfred Veyhl had its own style. It was mostly the combination of polychromatic painted details of birds, flowers, and similar motifs, framed with silver.
The more abstract designs are rare. Alfred, and later his son Manfred Veyhl, were the only ones who used a varnish to avoid silver oxidation. Alfred used more softer and rounder lines in his designs, whereas Manfred had a more angular, expressive style. A specialty for this company was that clients could choose from a certain range of porcelain forms and décors. The items were then produced exclusively in a single production run.
An outstanding figure is Friedrich Wilhelm Spahr. There is evidence that he learned his skill from Friedrich Deusch (some items of both firms have very similar formal designs). He was not only an artisan but an artist in developing repeating circumferential forms in a perfect and harmonic proportion. Very often it is the pure arrangement of lines (curved or straight), or their combination, with flowers or birds. Never over-designed, but enough to divide the small surface (for example of a vase) in a self-evident and harmonious way. Like the others, not only did he design and apply the silver overlay, he also prepared the porcelain with his own enamel colors, painted the motifs and engraved the silver. Of course he did not produce all these items by himself. Spahr's factory employed about forty specialized workers. The outstanding engraved pieces show the unrivaled quality of Spahr.
The early items typically have a thicker silver layer. One can also see the stroke of the brush which proves the overlay and painted surface were handcrafted. Printed designs were used more often on items produced later, especially those of Manfred Vehyl. These can be recognized by studying the design: if the color is flat and full of small dots, this strongly indicates a printed design. Also, the silver work on printed color designs appears not to cover the design closely, as it should.
The three companies bought and used porcelain blanks from several well known producers such as Rosenthal, Hutschenreuther, Thomas Bavaria, Krautheim & Adelberg and marketed the finished products under their own names. They also produced silver overlay glass in the same manner. A large amount of glassware came from WMF in Geislingen, which is not far from Schwäbisch Gmünd. A respectable amount of glass to be overlaid also came from Jean Beck, a famous glass designer in Munich. Until recently, it was believed that Beck created the brilliant silver designs himself and that Deusch only produced them. However, this was not the case. As with the porcelain, Deusch and others bought the delightfully stylized glass blanks, decorated them in silver overlay, and sold them under their own names. | 8 | Metallurgy |
Hemoglobin (haemoglobin, Hb or Hgb) is a protein containing iron that facilitates the transport of oxygen in red blood cells. Almost all vertebrates contain hemoglobin, with the exception of the fish family Channichthyidae. Hemoglobin in the blood carries oxygen from the respiratory organs (lungs or gills) to the other tissues of the body, where it releases the oxygen to enable aerobic respiration which powers the animal's metabolism. A healthy human has 12to 20grams of hemoglobin in every 100mL of blood. Hemoglobin is a metalloprotein, a chromoprotein, and globulin.
In mammals, hemoglobin makes up about 96% of a red blood cell's dry weight (excluding water), and around 35% of the total weight (including water). Hemoglobin has an oxygen-binding capacity of 1.34mL of O per gram, which increases the total blood oxygen capacity seventy-fold compared to dissolved oxygen in blood plasma alone. The mammalian hemoglobin molecule can bind and transport up to four oxygen molecules.
Hemoglobin also transports other gases. It carries off some of the body's respiratory carbon dioxide (about 20–25% of the total) as carbaminohemoglobin, in which CO binds to the heme protein. The molecule also carries the important regulatory molecule nitric oxide bound to a thiol group in the globin protein, releasing it at the same time as oxygen.
Hemoglobin is also found in other cells, including in the A9 dopaminergic neurons of the substantia nigra, macrophages, alveolar cells, lungs, retinal pigment epithelium, hepatocytes, mesangial cells of the kidney, endometrial cells, cervical cells, and vaginal epithelial cells. In these tissues, hemoglobin absorbs unneeded oxygen as an antioxidant, and regulates iron metabolism. Excessive glucose in the blood can attach to hemoglobin and raise the level of hemoglobin A1c.
Hemoglobin and hemoglobin-like molecules are also found in many invertebrates, fungi, and plants. In these organisms, hemoglobins may carry oxygen, or they may transport and regulate other small molecules and ions such as carbon dioxide, nitric oxide, hydrogen sulfide and sulfide. A variant called leghemoglobin serves to scavenge oxygen away from anaerobic systems such as the nitrogen-fixing nodules of leguminous plants, preventing oxygen poisoning.
The medical condition hemoglobinemia, a form of anemia, is caused by intravascular hemolysis, in which hemoglobin leaks from red blood cells into the blood plasma. | 7 | Physical Chemistry |
As a result of McCrones work on the Vinland Map, British author and researcher Ian Wilson approached McCrone in 1974 about the possibility of scientifically analyzing the Shroud of Turin, a length of linen cloth that has been venerated for centuries as the burial shroud of Jesus upon which his image is miraculously imprinted. This led to McCrones involvement with the Shroud of Turin Research Project (STURP). In 1977, a team of scientists affiliated with STURP proposed a barrage of tests to be carried out on the Shroud. With permission from the Archbishop of Turin, Cardinal Anastasio Ballestrero, STURP researchers conducted tests over a period of five days in October 1978, also using adhesive tape to obtain samples of the fibers from various parts on the Shroud's surface.
Based on his microscopic and chemical analysis of the tape samples obtained by STURP, McCrone concluded that the image on the Shroud was painted with a dilute pigment of red ochre in a collagen tempera (i.e., gelatin) medium, using a technique similar to the grisaille employed in the 14th century by Simone Martini and other European artists. McCrone also found that the "bloodstains" in the image had been highlighted with vermilion (a bright red pigment made from mercury sulfide), also in a collagen tempera medium. McCrone reported that no actual blood was present in the samples taken from the Shroud.
McCrones results were rejected by other members of STURP and McCrone resigned from STURP in June 1980. Two other members of STURP, John Heller and Alan Adler, published their own analysis concluding that Shroud did show traces of blood. Other STURP members also disputed McCrones conclusion that the Shroud image was painted, finding that physical analyses excluded the presence of pigments in sufficient quantities to account for the visible image.
McCrone continued to defend his results and to insist that polarized light microscopy, in which he was the only expert among the original members of STURP, was the correct technique to apply to the study of the Shroud. In 1983 he confidently predicted that radiocarbon dating of the Shrouds linen would show that it had been made shortly before the first historically recorded exhibition of the Shroud in 1356. The results of the 1988 radiocarbon dating of the Shroud vindicated McCrones microscopic and chemical analyses.
Until McCrones death in 2002, he continued to comment upon and explain the analysis that he had performed, becoming a prominent figure in the ongoing controversies surrounding the Shroud that attracted considerable attention in the public press. He re-stated and summarized his evidence that the Shroud was painted in an article published in 1990 in the journal Accounts of Chemical Research. He later wrote a book on the subject, Judgment Day for the Shroud of Turin, which was published in 1996 by the McCrone Research Institutes Microscope Publications and re-issued in 1999 by Prometheus Books (). In 2000, the American Chemical Society presented McCrone with its National Award in Analytical Chemistry for his work on the Shroud and for "his enduring patience for the defense of his methodologies." | 3 | Analytical Chemistry |
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