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*Gamma (γ): This is the matrix phase. While Co-based superalloys are less-used commercially, alloying elements include C, Cr, W, Ni, Ti, Al, Ir, and Ta. As in stainless steels, Chromium is used (occasionally up to 20 wt.%) to improve resistance to oxidation and corrosion via the formation of a CrO passive layer, which is critical for use in gas turbines, but also provides solid-solution strengthening due to the mismatch in the atomic radii of Co and Cr, and precipitation hardening due to the formation of MC-type carbides.
* Gamma Prime (γ): Constitutes the precipitate used to strengthen the alloy. It is usually close-packed with a L1 structure of CoTi or FCC CoTa, though both W and Al integrate into these cuboidal precipitates. Ta, Nb, and Ti integrate into the γ phase and are stabilize it at high temperatures.
* Carbide Phases: Carbides strengthen the alloy through precipitation hardening but decrease low-temperature ductility.
* Topologically Close-Packed (TCP) phases may appear in some Co-based superalloys, but embrittle the alloy and are thus undesirable. | 8 | Metallurgy |
Because the Edman degradation proceeds from the N-terminus of the protein, it will not work if the N-terminus has been chemically modified (e.g. by acetylation or formation of pyroglutamic acid). Sequencing will stop if a non-α-amino acid is encountered (e.g. isoaspartic acid), since the favored five-membered ring intermediate is unable to be formed. Edman degradation is generally not useful to determine the positions of disulfide bridges. It also requires peptide amounts of 1 picomole or above for discernible results. | 0 | Organic Chemistry |
Paraffinic hydrocarbons are part of the alkane series, and are the most common hydrocarbon found in crude oil. Paraffins are often a part of gasoline, making them comparatively more valuable.
Paraffinic hydrocarbons are also known as alkanes, and are represented by the formula CH, where n is a positive integer. | 9 | Geochemistry |
Rotation axes are denoted by a number n – 1, 2, 3, 4, 5, 6, 7, 8, ... (angle of rotation ). For improper rotations, Hermann–Mauguin symbols show rotoinversion axes, unlike Schoenflies and Shubnikov notations, that shows rotation-reflection axes. The rotoinversion axes are represented by the corresponding number with a macron, – , , , , , , , , ... . is equivalent to a mirror plane and usually notated as m. The direction of the mirror plane is defined as the direction perpendicular to it (the direction of the axis).
Hermann–Mauguin symbols show non-equivalent axes and planes in a symmetrical fashion. The direction of a symmetry element corresponds to its position in the Hermann–Mauguin symbol. If a rotation axis n and a mirror plane m have the same direction (i.e. the plane is perpendicular to axis n), then they are denoted as a fraction or n/m.
If two or more axes have the same direction, the axis with higher symmetry is shown. Higher symmetry means that the axis generates a pattern with more points. For example, rotation axes 3, 4, 5, 6, 7, 8 generate 3-, 4-, 5-, 6-, 7-, 8-point patterns, respectively. Improper rotation axes , , , , , generate 6-, 4-, 10-, 6-, 14-, 8-point patterns, respectively. If a rotation and a rotoinversion axis generate the same number of points, the rotation axis should be chosen. For example, the combination is equivalent to . Since generates 6 points, and 3 generates only 3, should be written instead of (not , because already contains the mirror plane m). Analogously, in the case when both 3 and axes are present, should be written. However we write , not , because both 4 and generate four points. In the case of the combination, where 2, 3, 6, , and axes are present, axes , , and 6 all generate 6-point patterns, as we can see on the figure in the right, but the latter should be used because it is a rotation axis – the symbol will be
Finally, the Hermann–Mauguin symbol depends on the type of the group. | 3 | Analytical Chemistry |
Many carbonyl compounds exhibit keto–enol tautomerism. This effect is especially pronounced in 1,3-dicarbonyl compounds that can form hydrogen-bonded enols. The equilibrium constant is dependent upon the solvent polarity, with the cis-enol form predominating at low polarity and the diketo form predominating at high polarity. The intramolecular H-bond formed in the cis-enol form is more pronounced when there is no competition for intermolecular H-bonding with the solvent. As a result, solvents of low polarity that do not readily participate in H-bonding allow cis-enolic stabilization by intramolecular H-bonding. | 7 | Physical Chemistry |
Similar to microbial fuel cells, biological photovoltaic systems which employ whole organisms have the advantage over non-biological fuel cells and photovoltaic systems of being able to self-assemble and self-repair (i.e. the photosynthetic organism is able to reproduce itself). The ability of the organism to store energy allows for power generation from biological photovoltaic systems in the dark, circumventing the grid supply and demand problems sometimes faced by conventional photovoltaics. Additionally, the use of photosynthetic organisms that fix carbon dioxide means the assembly of the light harvesting material in a biological photovoltaic system could have a negative carbon footprint.
Compared to microbial fuel cells, which use heterotrophic microorganisms, biological photovoltaic systems need no input of organic compounds to supply reducing equivalents to the system. This improves the efficiency of light-to-electricity conversion by minimising the number of reactions separating the capture of light energy and reduction of the anode. A disadvantage of using oxygenic photosynthetic material in bioelectrochemical systems is that the production of oxygen in the anodic chamber has a detrimental effect on the cell voltage. | 7 | Physical Chemistry |
Phosphine is used as a dopant in the semiconductor industry, and a precursor for the deposition of compound semiconductors. Commercially significant products include gallium phosphide and indium phosphide. | 0 | Organic Chemistry |
Vargulin is found in certain ostracods and deep-sea fish, to be specific, Poricthys. Like the compound coelenterazine, it is an imidazopyrazinone and emits primarily blue light in the animals. | 1 | Biochemistry |
Yakov Frenkel represented diffusion process in condensed matter as an ensemble of elementary jumps and quasichemical interactions of particles and defects. Henry Eyring applied his theory of absolute reaction rates to this quasichemical representation of diffusion. Mass action law for diffusion leads to various nonlinear versions of Fick's law. | 7 | Physical Chemistry |
Vibronic spectroscopy is a branch of molecular spectroscopy concerned with vibronic transitions: the simultaneous changes in electronic and vibrational energy levels of a molecule due to the absorption or emission of a photon of the appropriate energy. In the gas phase, vibronic transitions are accompanied by changes in rotational energy also.
Vibronic spectra of diatomic molecules have been analysed in detail; emission spectra are more complicated than absorption spectra. The intensity of allowed vibronic transitions is governed by the Franck–Condon principle. Vibronic spectroscopy may provide information, such as bond length, on electronic excited states of stable molecules. It has also been applied to the study of unstable molecules such as dicarbon, C, in discharges, flames and astronomical objects. | 7 | Physical Chemistry |
In mathematics and empirical science, quantification (or quantitation) is the act of counting and measuring that maps human sense observations and experiences into quantities. | 3 | Analytical Chemistry |
Ionized matter was first identified in a discharge tube (or Crookes tube), and so described by Sir William Crookes in 1879 (he called it "radiant matter"). The nature of the Crookes tube "cathode ray" matter was subsequently identified by English physicist Sir J.J. Thomson in 1897, and dubbed "plasma" by Irving Langmuir in 1928, perhaps because it reminded him of a blood plasma. | 7 | Physical Chemistry |
Diimide reductions result in the syn addition of dihydrogen to alkenes and alkynes. This observation has led to the proposal that the mechanism involves concerted hydrogen transfer from cis-diimide to the substrate. The cis isomer is the less stable of the two; however, acid catalysis may speed up equilibration of the trans and cis isomers.
Diimide is typically generated either through the oxidation of hydrazine or the decarboxylation of potassium azodicarboxylate. Kinetic experiments suggest that regardless of its method of generation, the formation of diimide is rate-limiting. The transition state of the hydrogen transfer step is likely early; however, high stereoselectivity has been obtained in many reductions of chiral alkenes.
The order of reactivity of unsaturated substrates is: alkynes, allenes > terminal or strained alkenes > substituted alkenes. Trans alkenes react more rapidly than cis alkenes in general. The reactivity difference between alkynes and alkenes is usually not great enough to isolate intermediate alkenes; however, alkenes can be isolated from allene reductions.
Diimide reduces symmetrical double bonds i.e.,C=C. N=N, O=O etc. unsymmetrical double bonds can not be reduced | 0 | Organic Chemistry |
A wide variety of alkyl Nb compounds have been prepared. Low coordination number complexes require the absence of any β-hydrogen to prevent rapid β-hydride elimination. The simplest compounds are salts of , which is prepared by alkylation of using methyl lithium: | 0 | Organic Chemistry |
Dioxiranes may be produced through the action of KHSO on carbonyl compounds. Because of their low-lying σ* orbital, they are highly electrophilic oxidants and react with unsaturated functional groups, Y-H bonds (yielding oxygen insertion products), and heteroatoms. The most common dioxiranes employed for organic synthesis are dimethyldioxirane (DMD) and trifluoromethyl-methyldioxirane (TFD). The latter is effective for chemoselective oxidations of C-H and Si-H bonds. Although this class of reagents is most famous for the epoxidation of alkenes, dioxiranes have been used extensively for other kinds of oxidations as well. | 0 | Organic Chemistry |
The material has the unusual property of changing to ammonium thiocyanate upon heating above . Upon cooling, the ammonium salt converts back to thiourea. | 0 | Organic Chemistry |
Oocyte selection is a procedure that is performed prior to in vitro fertilization, in order to use oocytes with maximal chances of resulting in pregnancy. In contrast, embryo selection takes place after fertilization.
Not all women can conceive naturally, leaving them with a need for technologies and research that can help them have children. Women who might not be able to have their kids naturally may have the option of in vitro fertilization. In vitro fertilization can be a series of treatments that involves the fertilization of a mature egg with a sperm in a laboratory. Oocyte selection is a part the process for in vitro fertilization. An Oocyte is an egg/ovum that is not fully mature or developed and has not been fertilized; Therefore an oocyte is an undeveloped ovum.
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Perera is the pioneer campaigner in Sri Lanka for Social Inclusion focusing equal opportunity, justice and dignity for People of ALL Abilities in day-to-day life – the key concept in this context being universal design for inclusion of people.- (meaning construction of environments that enable by design so as to include all and exclude none.) | 3 | Analytical Chemistry |
In the U.S. in 1975, under the authority of the Safe Drinking Water Act, the U.S. Environmental Protection Agency determined the National Interim Primary Drinking Water Regulation levels of arsenic (inorganic contaminant – IOCs) to be 0.05 mg/L (50 parts per billion – ppb).
Throughout the years, many studies reported dose-dependent effects of arsenic in drinking water and skin cancer. In order to prevent new cases and death from cancerous and non-cancerous diseases, the Safe Drinking Water Act directed the Environmental Protection Agency to revise arsenic's levels and specified the maximum contaminant level (MCL). MCLs are set as close to the health goals as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies.
In 2001, Environmental Protection Agency adopted a lower standard of MCL 0.01 mg/L (10 ppb) for arsenic in drinking water that applies to both community water systems and non-transient non-community water systems.
In some other countries, when developing national drinking water standards based on the guideline values, it is necessary to take account of a variety of geographical, socio-economic, dietary and other conditions affecting potential exposure. These factors lead to national standards that differ appreciably from the guideline values. That is the case in countries such as India and Bangladesh, where the permissible limit of arsenic in absence of an alternative source of water is 0.05 mg/L. | 1 | Biochemistry |
As an abstract graph, the Laves graph can be constructed as the maximal abelian covering graph of the complete graph . Being an abelian covering graph of means that the vertices of the Laves graph can be four-colored such that each vertex has neighbors of the other three colors and so that there are color-preserving symmetries taking any vertex to any other vertex with the same color. For the Laves graph in its geometric form with integer coordinates, these symmetries are translations that add even numbers to each coordinate (additionally, the offsets of all three coordinates must be congruent modulo four). When applying two such translations in succession, the net translation is irrespective of their order: they commute with each other, forming an abelian group. The translation vectors of this group form a three-dimensional lattice. Finally, being a maximal abelian covering graph means that there is no other covering graph of involving a higher-dimensional lattice. This construction justifies an alternative name of the Laves graph, the crystal.
A maximal abelian covering graph can be constructed from any finite graph ; applied to , the construction produces the (abstract) Laves graph, but does not give it the same geometric layout. Choose a spanning tree of , let be the number of edges that are not in the spanning tree (in this case, three non-tree edges), and choose a distinct unit vector in for each of these non-tree edges. Then, fix the set of vertices of the covering graph to be the ordered pairs where is a vertex of and is a vector in . For each such pair, and each edge adjacent to in , make an edge from to where is the zero vector if belongs to the spanning tree, and is otherwise the basis vector associated with , and where the plus or minus sign is chosen according to the direction the edge is traversed. The resulting graph is independent of the chosen spanning tree, and the same construction can also be interpreted more abstractly using homology.
Using the same construction, the hexagonal tiling of the plane is the maximal abelian covering graph of the three-edge dipole graph, and the diamond cubic is the maximal abelian covering graph of the four-edge dipole. The -dimensional integer lattice (as a graph with unit-length edges) is the maximal abelian covering graph of a graph with one vertex and self-loops. | 3 | Analytical Chemistry |
It is known that muscarinic acetylcholine receptors also appear on the pre-synaptic membrane of somatic neurons in the neuro-muscular junction, where they are involved in the regulation of acetylcholine release. | 1 | Biochemistry |
Sulfenyl chlorides are typically prepared by chlorination of disulfides: This reaction is sometimes called the Zincke disulfide reaction, in recognition of Theodor Zincke.
Some thioethers () with electron-withdrawing substituents undergo chlorinolysis of a bond to afford the sulfenyl chloride.
In a variation on the Reed reaction, sulfur dichloride displaces hydrogen under UV light. | 0 | Organic Chemistry |
In autoimmunity the immune system wrongly recognizes certain native molecules in the body as foreign (self-antigen), and mounts an immune response against them. Since these native molecules, as normal parts of the body, will naturally always exist in the body, the attacks against them can get stronger over time (akin to secondary immune response). Moreover, many organisms exhibit molecular mimicry, which involves showing those antigens on their surface that are antigenically similar to the host proteins. This has two possible consequences: first, either the organism will be spared as a self antigen; or secondly, that the antibodies produced against it will also bind to the mimicked native proteins. The antibodies will attack the self-antigens and the tissues harboring them by activating various mechanisms like the complement activation and antibody-dependent cell-mediated cytotoxicity. Hence, wider the range of antibody-specificities, greater the chance that one or the other will react against self-antigens (native molecules of the body). | 1 | Biochemistry |
If half of the tetrahedral sites of the parent FCC lattice are filled by ions of opposite charge, the structure formed is the zincblende crystal structure. If all the tetrahedral sites of the parent FCC lattice are filled by ions of opposite charge, the structure formed is the fluorite structure or antifluorite structure. If all the octahedral sites of the parent FCC lattice are filled by ions of opposite charge, the structure formed is the rock-salt structure. | 3 | Analytical Chemistry |
Polarized light (PL) is very useful when studying the structure of metals with non-cubic crystal structures (mainly metals with hexagonal close-packed (hcp) crystal structures). If the specimen is prepared with minimal damage to the surface, the structure can be seen vividly in cross-polarized light (the optic axis of the polarizer and analyzer are 90 degrees to each other, i.e., crossed). In some cases, an hcp metal can be chemically etched and then examined more effectively with PL. Tint etched surfaces, where a thin film (such as a sulfide, molybdate, chromate or elemental selenium film) is grown epitaxially on the surface to a depth where interference effects are created when examined with BF producing color images, can be improved with PL. If it is difficult to get a good interference film with good coloration, the colors can be improved by examination in PL using a sensitive tint (ST) filter. | 8 | Metallurgy |
Zooplankton-mediated release of DOC occurs through sloppy feeding, excretion and defecation which can be important energy sources for microbes. Such DOC production is largest during periods with high food concentration and dominance of large zooplankton species. | 2 | Environmental Chemistry |
Nesfatin-1 can cross the blood–brain barrier without saturation.
The receptors within the brain are in the hypothalamus and the solitary nucleus, where nesfatin-1 is believed to be produced via peroxisome proliferator-activated receptors (PPARs). It appears there is a relationship between nesfatin-1 and cannabinoid receptors. Nesfatin-1-induced inhibition of feeding may be mediated through the inhibition of orexigenic NPY neurons.
Nesfatin/NUCB2 expression has been reported to be modulated by starvation and re-feeding in the Paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the brain. Nesfatin-1 influences the excitability of a large proportion of different subpopulations of neurons located in the PVN. It is also reported that magnocellular oxytocin neurons are activated during feeding, and ICV infusion of oxytocin antagonist increases food intake, indicating a possible role of oxytocin in the regulation of feeding behavior. In addition, it is proposed that feeding-activated nesfatin-1 neurons in the PVN and SON could play an important role in the postprandial regulation of feeding behavior and energy homeostasis.
Nesfatin-1 immunopositive neurons are also located in the arcuate nucleus (ARC). Nesfatin-1 immunoreactive neurons in the ARC are activated by simultaneous injection of ghrelin and desacyl ghrelin, nesfatin-1 may be involved in the desacyl ghrelin-induced inhibition of the orexigenic effect of peripherally administered ghrelin in freely fed rat.
Nesfatin-1 was co-expressed with melanin concentrating hormone (MCH) in tuberal hypothalamic neurons. Nesfatin-1 co-expressed in MCH neurons may play a complex role not only in the regulation of food intake, but also in other essential integrative brain functions involving MCH signaling, ranging from autonomic regulation, stress, mood, cognition to sleep. | 1 | Biochemistry |
Ethanol can be made from mineral oil or from sugars or starches. Starches are cheapest. The starchy crop with highest energy content per acre is cassava, which grows in tropical countries.
Thailand already had a large cassava industry in the 1990s, for use as cattle feed and as a cheap admixture to wheat flour. Nigeria and Ghana are already establishing cassava-to-ethanol plants. Production of ethanol from cassava is currently economically feasible when crude oil prices are above US$120 per barrel.
New varieties of cassava are being developed, so the future situation remains uncertain.
Currently, cassava can yield between 25 and 40 tonnes per hectare (with irrigation and fertilizer), and from a tonne of cassava roots, circa 200 liters of ethanol can be produced (assuming cassava with 22% starch content). A liter of ethanol contains circa 21.46 MJ of energy. The overall energy efficiency of cassava-root to ethanol conversion is circa 32%.
The yeast used for processing cassava is Endomycopsis fibuligera, sometimes used together with bacterium Zymomonas mobilis. | 1 | Biochemistry |
The functional significance of respirasomes is not entirely clear but more recent research is beginning to shed some light on their purpose. It has been hypothesized that the organization of respiratory enzymes into supercomplexes reduces oxidative damage and increases metabolism efficiency. Schäfer et al. (2006) demonstrated that supercomplexes comprising Complex IV had higher activities in Complex I and III, indicating that the presence of Complex IV modifies the conformation of the other complexes to enhance catalytic activity. Evidence has also been accumulated to show that the presence of respirasomes is necessary for the stability and function of Complex I. In 2013, Lapuente-Brun et al. demonstrated that supercomplex assembly is "dynamic and organizes electron flux to optimize the use of available substrates." | 1 | Biochemistry |
In chemistry, the electromeric effect is a molecular polarization occurring by an intramolecular electron displacement characterized by the substitution of one electron pair for another within the same atomic octet of electrons. It is sometimes called the conjugative mechanism, and previously, the tautomeric mechanism). The electromeric effect is often considered along with the inductive effect as types of electron displacement. Although some people refer it as an effect produced by the presence of a reagent like an electrophile or a nucleophile, IUPAC does not define it as such. The term electromeric effect is no longer used in standard texts and is considered as obsolete. The concepts implied by the terms electromeric effect and mesomeric effect are absorbed in the term resonance effect. This effect can be represented using curved arrows which symbolize the electron shift, as in the diagram below: | 7 | Physical Chemistry |
Adkins' study found that global salinity increased with a global sea level drop of 120 m. Analyzing O data they also found that deep waters were within error of the freezing point, with oceanic waters exhibiting a greater degree of homogeneity in temperatures. In contrast, variations in salinity were much greater than they are today. Modern day salinities are all within 0.5 psu of the global average salinity of 34.7 psu, whereas salinities during the last glacial maximum (LGM) ranged from 35.8 psu in the North Atlantic to 37.1 in the Southern Ocean.
There are some notable differences in the hydrography at the LGM and present day. Today the North Atlantic Deep Water (NADW) is observed to be more saline than Antarctic Bottom Water (AABW), whereas at the last glacial maximum it was observed that the AABW was in fact more saline; a complete reversal. Today the NADW is more salty because of the Gulf Stream; this could thus indicate a reduction of flow through the Florida Straits due to lowered sea level.
Another observation is that the Southern Ocean was vastly more salty at the LGM than today. This is particularly intriguing given the assumed importance of the Southern Ocean in oceanic dynamical regulation of ice ages. The extreme value of 37.1 psu is assumed to be a consequence of an increased degree of sea ice formation and export. This would account for the increased salinity, but would also account for the lack of oxygen isotopic fractionation; brine rejection without oxygen isotopic fractionation is thought to be highly characteristic of sea ice formation. | 9 | Geochemistry |
MITF recognizes E-box (CAYRTG) and M-box (TCAYRTG or CAYRTGA) sequences in the promoter regions of target genes. Known target genes (confirmed by at least two independent sources) of this transcription factor include,
Additional genes identified by a microarray study (which confirmed the above targets) include the following, | 1 | Biochemistry |
Nanofluidic devices have been built for application in chemistry, molecular biology and medicine. The main purposes to use nanofluidic devices are separation and measurement of solutions containing nanoparticles for drug delivery, gene therapy and nanoparticle toxicology on a micro-total-analysis system. An important advantage of micro- and nano-scaled systems is the small amount of sample or reagent used in analysis. This reduces the time required for sample processing. It is also possible to achieve analysis in an array, which further speeds up processes and increases throughput of analysis.
Nanochannels are utilized to achieve single-molecule sensing and diagnosis, as well as DNA separation. In many cases, nanofluidic devices are integrated within a microfluidic system to facilitate logic operation of fluids. The future of nanofluidic systems will be focused on several areas such as analytical chemistry and biochemistry, liquid transport and metering, and energy conversion.
In nanofluidics, the valence numbers of the ions determines their net electrophoretic velocities. In other words, the velocity of an ion in the nano-channel is related not only to its ion mobility but also its ion valence. This enables the sorting function of nanofluidics, which cannot be done in a micro-channel. Therefore, it is possible to do sorting and separation for short strand DNA by using a nanochannel. For the single-molecule DNA application, the final goal is to sequence a strand of genomic DNA in a reproducible and precise result. Similar application can also be found in chromatography, or separation of various ingredients in the solution.
Application also can be found in synthesis of fibers. Polymer fibers can be created by electrospinning the monomers at an interface between liquid and vacuum. An organized polymer structure is formed from a flow of monomers aligning on a substrate.
There is also an attempt to bring nanofluidic technology into energy conversion. In this case, the electrical charged wall behaves as the stator, while the flowing solution as the rotor. It is observed that when the pressure-driven solvent flowing through a charged nanochannel, it can generate a streaming current and a streaming potential. This phenomenon can be used in electrical energy harvesting.
Advances in nanofabrication techniques and concerns about energy shortage make people interested in this idea. The main challenge is to increase efficiency, which is now only a few percent, compared with efficiencies of up to about 95 per cent for standard rotational electromagnetic generators. | 7 | Physical Chemistry |
A polar organic chemical integrative sampler (POCIS) is a passive sampling device which allows for the in situ collection of a time-integrated average of hydrophilic organic contaminants developed by researchers with the United States Geological Survey in Columbia, Missouri. POCIS provides a means for estimating the toxicological significance of waterborne contaminants. The POCIS sampler mimics the respiratory exposure of organisms living in the aquatic environment and can provide an understanding of bioavailable contaminants present in the system. POCIS can be deployed in a wide range of aquatic environments and is commonly used to assist in environmental monitoring studies.
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In condensed matter physics, a string-net is an extended object whose collective behavior has been proposed as a physical mechanism for topological order by Michael A. Levin and Xiao-Gang Wen. A particular string-net model may involve only closed loops; or networks of oriented, labeled strings obeying branching rules given by some gauge group; or still more general networks. | 7 | Physical Chemistry |
Fluorescence polarization immunoassay (FPIA) is a class of in vitro biochemical test used for rapid detection of antibody or antigen in sample. FPIA is a competitive homogenous assay, that consists of a simple prepare and read method, without the requirement of separation or washing steps.
The basis of the assay is fluorescence anisotropy, also known as fluorescence polarization. If a fluorescent molecule is stationary and exposed to plane-polarized light, it will become excited and consequently emit radiation back to the polarized-plane. However, if the excited fluorescent molecule is in motion (rotational or translational) during the fluorescent lifetime, it will emit light in a different direction than the excitation plane. The fluorescent lifetime is the amount of time between the absorption moment and the fluorescent emission moment.
Typically, the rate at which a molecule rotates is indicative of its size. When a fluorescent-labelled molecule (tracer) binds to another molecule the rotational motion will change, resulting in an altered intensity of plane-polarized light, which results in altered fluorescence polarization. Fluorescence polarization immunoassays employ a fluorophore bound antigen that when bound to the antibody of interest, will increase fluorescence polarization. The change in polarization is proportional to the amount of antigen in sample, and is measured by a fluorescence polarization analyzer. | 1 | Biochemistry |
Beryllium can coordinate with an N-hetereocyclic carbene (NHC). NHCs are defined as heterocyclic species containing a carbene carbon and at least one nitrogen atom within the ring structure. NHCs have found numerous applications in some of the most important catalytic transformations in chemical industry, but their reactivity in coordinating with main group elements especially with beryllium’s potential as a reactive organocatalyst has opened new areas of research. | 0 | Organic Chemistry |
Organothiophosphates are a subclass of organophosphorus compounds that are structurally related to the inorganic thiophosphates. Common members have formulas of the type (RO)RPS and related compounds where RO is replaced by RS. Many of these compounds are used as insecticides, some have medical applications, and some have been used as oil additives.
Oligonucleotide phosphorothioates (OPS) are modified oligonucleotides where one of the oxygen atoms in the phosphate moiety is replaced by sulfur. They are the basis of antisense therapy, e.g., the drugs fomivirsen (Vitravene), oblimersen, alicaforsen, and mipomersen (Kynamro). | 0 | Organic Chemistry |
The Schlenk equilibrium, named after its discoverer Wilhelm Schlenk, is a chemical equilibrium taking place in solutions of Grignard reagents and Hauser bases
:2 RMgX MgX + MgR
The process described is an equilibrium between two equivalents of an alkyl or aryl magnesium halide on the left of the equation and on the right side, one equivalent of the dialkyl or diaryl magnesium compound and magnesium halide salt. Organomagnesium halides in solution also form dimers and higher oligomers, especially at high concentration. Alkyl magnesium chlorides in ether are present as dimers.
The position of the equilibrium is influenced by solvent, temperature, and the nature of the various substituents. It is known that magnesium center in Grignard reagents typically coordinates two molecules of ether such as diethyl ether or tetrahydrofuran (THF). Thus they are more precisely described as having the formula RMgXL where L = an ether. In the presence of monoethers, the equilibrium typically favors the alkyl- or arylmagnesium halide. Addition of dioxane to such solutions, however, leads to precipitation of the coordination polymers MgX(μ-dioxane)2, driving the equilibrium completely to the right. The dialkylmagnesium compounds are popular in the synthesis of organometallic compounds. | 0 | Organic Chemistry |
Liquid is the primary component of hydraulic systems, which take advantage of Pascal's law to provide fluid power. Devices such as pumps and waterwheels have been used to change liquid motion into mechanical work since ancient times. Oils are forced through hydraulic pumps, which transmit this force to hydraulic cylinders. Hydraulics can be found in many applications, such as automotive brakes and transmissions, heavy equipment, and airplane control systems. Various hydraulic presses are used extensively in repair and manufacturing, for lifting, pressing, clamping and forming. | 7 | Physical Chemistry |
A solar-powered desalination unit produces potable water from saline water by using a photovoltaic system to supply the energy. Solar power works well for water purification in settings lacking grid electricity and can reduce operating costs and greenhouse emissions. For example, a solar-powered desalination unit designed passed tests in Australia's Northern Territory.
Sunlight's intermittent nature makes output prediction difficult without an energy storage capability. However batteries or thermal energy storage systems can provide power when the sun does not. | 3 | Analytical Chemistry |
The dystrophin-associated protein complex is important for cell structure and cell signalling. It is one of two protein complexes found in the costamere in striated muscle fibres. | 1 | Biochemistry |
Eudistomin U is a β-carboline derivative. The structure of this molecule is made up of a β-carboline with an aromatic indole at the 1 position, thus also functioning as an indole. Eudistomin C is also a cytotoxic molecule, and its cytotoxicity have been shown to affect certain cancer cell line and human pathogens. A recent study suggested that this cytotoxicity may allow Eudistomin C to bind to DNA molecules. In addition to this, Eudistomin C displayed antibacterial property in Gram-Positive Bacteria. This is due to Eudistomin C damaging the bacterias cell membrane and interfering with the DNA gyrase function, which directly leads to cell death. | 1 | Biochemistry |
This type of phase transformation is known as spinodal decomposition, and can be illustrated on a phase diagram exhibiting a miscibility gap. Thus, phase separation occurs whenever a material transition into the unstable region of the phase diagram. The boundary of the unstable region sometimes referred to as the binodal or coexistence curve, is found by performing a common tangent construction of the free-energy diagram. Inside the binodal is a region called the spinodal, which is found by determining where the curvature of the free-energy curve is negative. The binodal and spinodal meet at the critical point. It is when a material is moved into the spinodal region of the phase diagram that spinodal decomposition can occur.
The [https://www.doitpoms.ac.uk/tlplib/phase-diagrams/freeenergy.php#:~:text=The%20phase%20with%20the%20lowest,the%20liquid%20phase%20is%20stable. free energy curve] is plotted as a function of composition for a temperature below the convolute temperature, T. Equilibrium phase compositions are those corresponding to the free energy minima. Regions of negative curvature (∂f/∂c f/∂c = 0 ) which are called the spinodes. Their locus as a function of temperature defines the spinodal curve. For compositions within the spinodal, a homogeneous solution is unstable against infinitesimal fluctuations in density or composition, and there is no thermodynamic barrier to the growth of a new phase. Thus, the spinodal represents the limit of physical and chemical stability.
To reach the spinodal region of the phase diagram, a transition must take the material through the binodal region or the critical point. Often phase separation will occur via nucleation during this transition, and spinodal decomposition will not be observed. To observe spinodal decomposition, a very fast transition, often called a quench, is required to move from the stable to the spinodal unstable region of the phase diagram.
In some systems, ordering of the material leads to a compositional instability and this is known as a conditional spinodal, e.g. in the feldspars. | 7 | Physical Chemistry |
The rise of systems biology, seeking to comprehend biological processes as a whole, highlighted the need to not only develop corresponding quantitative models but also to create standards allowing their exchange and integration. This concern drove the community to design common data formats, such as SBML and CellML. SBML is now largely accepted and used in the field. However, as important as the definition of a common syntax is, it is also necessary to make clear the semantics of models. SBO tries to give us a way to label models with words that describe how they should be used in a large group of models that are commonly used in computational systems biology. The development of SBO was first discussed at the 9th SBML Forum Meeting in Heidelberg on October 14–15, 2004. During the forum, Pedro Mendes mentioned that modellers possessed a lot of knowledge that was necessary to understand the model and, more importantly, to simulate it, but this knowledge was not encoded in SBML. Nicolas Le Novère proposed to create a controlled vocabulary to store the content of Pedro Mendes' mind before he wandered out of the community. The development of the ontology was announced more officially in a message from Le Novère to Michael Hucka and Andrew Finney on October 19. | 1 | Biochemistry |
CFCs and HCFCs are used in various applications because of their low toxicity, reactivity and flammability. Every permutation of fluorine, chlorine and hydrogen based on methane and ethane has been examined and most have been commercialized. Furthermore, many examples are known for higher numbers of carbon as well as related compounds containing bromine. Uses include refrigerants, blowing agents, aerosol propellants in medicinal applications, and degreasing solvents.
Billions of kilograms of chlorodifluoromethane are produced annually as a precursor to tetrafluoroethylene, the monomer that is converted into Teflon. | 2 | Environmental Chemistry |
Currently, receptor modulators are categorized in the Agonist, Partial Agonist, Selective Tissue Modulators, Antagonist, and Inverse Agonist categories in terms of the effect they cause. They are further divided into Orthosteric or Allosteric Modulators according to how they effect said result. Typically, a chemical acts in an agonist fashion whenever it instigates or else facilitates a particular reaction by binding to a particular receptor. In contract, a chemical acts as an antagonist whenever binding to a particular receptor blocks or inhibits a particular response. Between these endpoints exists a gradient defined by a number of variables. One example is Selective Tissue Modulators, which mean a given ligand can behave differently according to the tissue type it is in. As for orthosteric and allosteric modulation, this describes the manner in which the ligand binds to the receptor in question: if it binds directly to the prescribed binding site of a receptor, the ligand is orthosteric in this instance; if the ligand alters the receptor by interacting with it at any place other than a binding site, allosteric interaction occurred. Note that a drug's categorization does not dictate how another drug of the same family could be categorized or whether the same drug may also function in another category. An example is found in medications used to treat opioid addiction, with methadone, buprenorphine, naloxone, and naltrexone all in separate categories or in more than one simultaneously. In addition, depending on the cell type, the specific effect, whether agonist, antagonist, inverse agonist, etc., could have a unique specific effect. An example is seen in insulin, under "Receptor Agonists," as it interacts with multiple different cell types as an agonist, but incites multiple and different responses in both. | 1 | Biochemistry |
Although the cost of acquiring hyperspectral images is typically high for specific crops and in specific climates, hyperspectral remote sensing use is increasing for monitoring the development and health of crops. In Australia, work is under way to use imaging spectrometers to detect grape variety and develop an early warning system for disease outbreaks. Furthermore, work is under way to use hyperspectral data to detect the chemical composition of plants, which can be used to detect the nutrient and water status of wheat in irrigated systems. On a smaller scale, NIR hyperspectral imaging can be used to rapidly monitor the application of pesticides to individual seeds for quality control of the optimum dose and homogeneous coverage.
Another application in agriculture is the detection of animal proteins in compound feeds to avoid bovine spongiform encephalopathy (BSE), also known as mad-cow disease. Different studies have been done to propose alternative tools to the reference method of detection, (classical microscopy). One of the first alternatives is near infrared microscopy (NIR), which combines the advantages of microscopy and NIR. In 2004, the first study relating this problem with hyperspectral imaging was published. Hyperspectral libraries that are representative of the diversity of ingredients usually present in the preparation of compound feeds were constructed. These libraries can be used together with chemometric tools to investigate the limit of detection, specificity and reproducibility of the NIR hyperspectral imaging method for the detection and quantification of animal ingredients in feed.
HSI cameras can also be used to detect stress from heavy metals in plants and become an earlier and faster alternative to post-harvest wet chemical methods. | 7 | Physical Chemistry |
Norrish and Smith, Trommsdorff, and later, Schultz and Harborth, concluded that autoacceleration must be caused by a totally different polymerization mechanism. They rationalized through experiment that a decrease in the termination rate was the basis of the phenomenon. This decrease in termination rate, k, is caused by the raised viscosity of the polymerization region when the concentration of previously formed polymer molecules increases. Before autoacceleration, chain termination by combination of two free-radical chains is a very rapid reaction that occurs at very high frequency (about one in 10 collisions). However, when the growing polymer molecules – with active free-radical ends – are surrounded in the highly viscous mixture consisting of a growing concentration of "dead" polymer, the rate of termination becomes limited by diffusion. The Brownian motion of the larger molecules in the polymer "soup" is restricted, therefore limiting the frequency of their effective (termination) collisions. | 7 | Physical Chemistry |
One-step RT-PCR subjects mRNA targets (up to 6 kb) to reverse transcription followed by PCR amplification in a single test tube. It is important to note that using intact, high quality RNA and a sequence-specific primer will produce the best results.
Once a one-step RT-PCR kit with a mix of reverse transcriptase, Taq DNA polymerase, and a proofreading polymerase is selected and all necessary materials and equipment are obtained a reaction mix is to be prepared. The reaction mix includes dNTPs, primers, template RNA, necessary enzymes, and a buffer solution. The reaction mix is added to a PCR tube for each reaction, followed by template RNA. The PCR tubes are then placed in a thermal cycler to begin cycling. In the first cycle, synthesis of cDNA occurs. The second cycle is the initial denaturation wherein reverse transcriptase is inactivated. The remaining 40-50 cycles are the amplification, which includes denaturation, annealing, and elongation. When amplification is complete, the RT-PCR products can be analyzed with gel electrophoresis.
(PCR Applications Manual and Biotools) | 1 | Biochemistry |
Tang's research interests encompass photocatalytic/thermocatalytic small molecule activation (e.g. CH, N, HO, CH and CO) and microwave catalysis (e.g. plastic recycling), together with the investigation of the underlying charge dynamics and kinetics by state-of-the-art spectroscopies. According to Google Scholar, these research activities result into >250 journal papers in reputable journals. | 5 | Photochemistry |
Magnetic roasting involves controlled roasting of the ore to convert it into a magnetic form, thus enabling easy separation and processing in subsequent steps. For example, controlled reduction of haematite (non magnetic FeO) to magnetite (magnetic FeO). | 8 | Metallurgy |
Following the successful clinical trials in LCA, researchers have been developing similar treatments using adeno-associated virus for age-related macular degeneration (AMD). To date, efforts have focused on long-term delivery of VEGF inhibitors to treat the wet form of macular degeneration. Whereas wet AMD is currently treated using frequent injections of recombinant protein into the eyeball, the goal of these treatments is long-term disease management following a single administration. One such study is being conducted at the Lions Eye Institute in Australia in collaboration with Avalanche Biotechnologies, a US-based biotechnology start-up. Another early-stage study is sponsored by Genzyme Corporation. | 1 | Biochemistry |
A safety concern has been raised on the basis of several studies regarding the effect of toothpaste SDS on aphthous ulcers (more specifically, mouth ulcers or "canker sores"), commonly referred to as canker or white sores. According to the NHS, SLS is a cause for concern for mouth ulcers. As Lippert notes, of 2013, "very few... marketed toothpastes contain a surfactant other than SLS [SDS]," and leading manufacturers continue to formulate their produce with SDS. | 1 | Biochemistry |
In chemistry and materials science, molecular self-assembly is the process by which molecules adopt a defined arrangement without guidance or management from an outside source. There are two types of self-assembly: intermolecular and intramolecular. Commonly, the term molecular self-assembly refers to the former, while the latter is more commonly called folding. | 6 | Supramolecular Chemistry |
Last but not least prof. E.J.Zoqui has summarized in his work the approach proposed by several researchers in the criteria for semi-solid processing, which involves the stability of the solid phase fs with the temperature; to process semisolid alloys the sensitivity to variation of solid fraction with temperature should be minimal: in one direction it could evolve to a difficult to deform solid, on the other to a liquid which may be difficult to shape without proper moulding. It turns out that we can express this criterion again by evaluating the slope of the solidification curve, in fact ∂(fS)/∂T should be less than a certain threshold, which is commonly accepted in the scientific and technical literature to be below 0.03 1/K. Mathematically this may be expressed by an inequation, ∂(fS)/∂T < 0.03 (1/K) - where K stands for Kelvin degrees - could be equally assumed for a rough estimate of the two main semi-solid casting processing: both rheocasting ( 0.3<fs<0.4 ) and thixoforming (0.6<fs<0.7). If one would go back just to the (numerical) and functional approaches above, one should consider the reciprocal value i.e. ∂T/∂(fS)> 33 (K) | 8 | Metallurgy |
Calcareous soils are relatively alkaline, in other words they have a high pH. This is because of the very weak acidity of carbonic acid. Note that this is not the only reason for a high soil pH. They are characterized by the presence of calcium carbonate in the parent material and may have a calcic horizon, a layer of secondary accumulation of carbonates (usually calcium or Mg) in excess of 15% calcium carbonate equivalent and at least 5% more carbonate than an underlying layer. | 9 | Geochemistry |
The mechanism of PICUP require the tris(bipyridyl)Ru(II) complex, an electron acceptor, ammonium persulfate (APS), and reactive amino acid side chains. Tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate, a tris(bipyridyl)Ru(II) complex, initially contains a Ru. Upon visible light irradiation and in the presence of ammonium persulfate (APS), Ru enters its excited state and is oxidized to Ru. Ru is now an extremely reactive oxidizer that only wants to accept one electron instead of the standard two. The reaction can proceed in the absence of an electron acceptor, but it will have a much lower efficiency, producing byproducts resulting from the excited Ru(Bpy) reacting with oxygen. As an effective single electron oxidizer, Ru will pick up a single electron from amino acids of the neighboring proteins, most commonly Tryptophan and Tyrosine. This produces a radical that is highly unstable on the amino acid side chains, which proceeds through reactions to reach a more stable state.
The unpaired single electron on the side chain reacts with another amino acid side chain of a polypeptide in the vicinity, resulting in a dimer with a covalent bond. With the regeneration of Ru when Ru picks up an electron from the amino acids allows for continuous formation of radicals with Ru being oxidized by APS.
In the PCR tube that the reaction takes place in, numerous unstable protein radicals come in contact with each other through simple diffusion and react both intra- and intermolecularly to achieve a more stable state. The monomeric protein radicals are able to achieve a lower energy state through forming a covalent bond to produce a dimer and releasing a hydrogen atom. PLEASE NOTE: The image mistakenly shows the release of a proton and should not be used in this form (See also ref. 4). The creator has been contacted. This newly formed dimer is also able to react with numerous other monomers or dimers through the same mechanism, creating higher numbers of cross-linked oligomers. This allows for a distribution of variety of oligomers to be present in the mixture. | 1 | Biochemistry |
Microwave-assisted peptide synthesis has been used to complete long peptide sequences with high degrees of yield and low degrees of racemization. | 1 | Biochemistry |
It is a useful reagent for the preparation of other diphenylarsenic compounds, e.g. by reactions with Grignard reagents:
:RMgBr + (CH)AsCl → (CH)AsR + MgBrCl
:(R = alkyl, aryl) | 1 | Biochemistry |
A yeast commonly used for protein production is Pichia pastoris. Examples of yeast expression vector in Pichia are the pPIC series of vectors, and these vectors use the AOX1 promoter which is inducible with methanol. The plasmids may contain elements for insertion of foreign DNA into the yeast genome and signal sequence for the secretion of expressed protein. Proteins with disulphide bonds and glycosylation can be efficiently produced in yeast. Another yeast used for protein production is Kluyveromyces lactis and the gene is expressed, driven by a variant of the strong lactase LAC4 promoter.
Saccharomyces cerevisiae is particularly widely used for gene expression studies in yeast, for example in yeast two-hybrid system for the study of protein-protein interaction. The vectors used in yeast two-hybrid system contain fusion partners for two cloned genes that allow the transcription of a reporter gene when there is interaction between the two proteins expressed from the cloned genes. | 1 | Biochemistry |
Prions are proteins of particular amino acid sequences in particular conformations. They propagate themselves in host cells by making conformational changes in other molecules of protein with the same amino acid sequence, but with a different conformation that is functionally important or detrimental to the organism. Once the protein has been transconformed to the prion folding it changes function. In turn it can convey information into new cells and reconfigure more functional molecules of that sequence into the alternate prion form. In some types of prion in fungi this change is continuous and direct; the information flow is Protein → Protein.
Some scientists such as Alain E. Bussard and Eugene Koonin have argued that prion-mediated inheritance violates the central dogma of molecular biology. However, Rosalind Ridley in Molecular Pathology of the Prions (2001) has written that "The prion hypothesis is not heretical to the central dogma of molecular biology—that the information necessary to manufacture proteins is encoded in the nucleotide sequence of nucleic acid—because it does not claim that proteins replicate. Rather, it claims that there is a source of information within protein molecules that contributes to their biological function, and that this information can be passed on to other molecules." | 1 | Biochemistry |
Lake Chichoj is located within 2 km of the Chixoy-Polochic fault, a major fault of the North America-Caribbean plate boundary, which constitutes the closest and largest seismic hazard for San Cristóbal Verapaz, but lies within a broader array of large to intermediate seismogenic faults. The latest noticeable earthquakes include a M 4.1 quake in 2006 on the Polochic fault and a M4.8 in June 2009 on a secondary fault, NW of the lake. The sediments of the lake host a rich record of disruptions produced by past earthquakes, most notably the M 7.8 February 4th 1978 earthquake on the Motagua fault as well as a series of older M 7 earthquakes along the Polochic fault between 850 CE and 1450 CE. The lake adds hazard to the ground shaking of earthquakes. The low-lying marshlands that surround the lake are increasingly filled and urbanized. They are susceptible to seismic wave amplification, seismic wave refraction, and soil liquefaction during earthquakes, but also susceptible to flooding during earthquakes if the lake spillovers. Large waves can be produced during earthquakes, either as a result of landslides affecting the lake inner slopes, or by seismic resonance (seiche waves). | 2 | Environmental Chemistry |
Fineman and Ross rearranged the copolymer equation into a linear form:
where and
Thus, a plot of versus yields a straight line with slope and intercept | 7 | Physical Chemistry |
The total energy of the system is where S is entropy, and the are the other extensive parameters of the system (e.g. volume, particle number, etc.). The entropy of the system may likewise be written as a function of the other extensive parameters as . Suppose that X is one of the which varies as a system approaches equilibrium, and that it is the only such parameter which is varying. The principle of maximum entropy may then be stated as:
: and at equilibrium.
The first condition states that entropy is at an extremum, and the second condition states that entropy is at a maximum. Note that for the partial derivatives, all extensive parameters are assumed constant except for the variables contained in the partial derivative, but only U, S, or X are shown. It follows from the properties of an exact differential (see equation 8 in the exact differential article) and from the energy/entropy equation of state that, for a closed system:
It is seen that the energy is at an extremum at equilibrium. By similar but somewhat more lengthy argument it can be shown that
which is greater than zero, showing that the energy is, in fact, at a minimum. | 7 | Physical Chemistry |
In organic chemistry, the propargyl group is a functional group of 2-propynyl with the structure . It is an alkyl group derived from propyne ().
The term propargylic refers to a saturated position (sp-hybridized) on a molecular framework next to an alkynyl group. The name comes from mix of propene and argentum, which refers to the typical reaction of the terminal alkynes with silver salts.
The term homopropargylic designates in the same manner
* a saturated position on a molecular framework next to a propargylic group and thus two bonds from an alkyne moiety.
* a 3-butynyl fragment, , or substituted homologue. | 0 | Organic Chemistry |
In chemical separation terminology, the raffinate (from French raffiner, to refine) is a product which has had a component or components removed. The product having the removed materials is referred to as the extract. For example, in solvent extraction, the raffinate is the liquid stream which remains after solutes from the original liquid are removed through contact with an immiscible liquid. In metallurgy, raffinating refers to a process in which impurities are removed from liquid material.
In pressure swing adsorption the raffinate refers to the gas which is not adsorbed during the high pressure stage. The species which is desorbed from the adsorbent at low pressure may be called the "extract" product. | 3 | Analytical Chemistry |
The alpha effect refers to the increased nucleophilicity of an atom due to the presence of an adjacent (alpha) atom with lone pair electrons. This first atom does not necessarily exhibit increased basicity compared with a similar atom without an adjacent electron-donating atom, resulting in a deviation from the classical Brønsted-type reactivity-basicity relationship. In other words, the alpha effect refers to nucleophiles presenting higher nucleophilicity than the predicted value obtained from the Brønsted basicity. The representative examples would be high nucleophilicities of hydroperoxide (HO) and hydrazine (NH). The effect is now well established with numerous examples and became an important concept in mechanistic chemistry and biochemistry. However, the origin of the effect is still controversial without a clear winner. | 7 | Physical Chemistry |
- For visible light,
- For neutrons,
- For "hard" X-rays,
while typical values for polymers range in . This makes small-angle measurements in neutrons and X-rays a bit more tedious, as very small angles are needed, and the data in those angles is often "overpowered" by the spot emerging in usual scattering experiments. The problem is mitigated by conducting longer experiments with more exposure time, which allows the required data to "intensify". One must take care though, as to not allow the prolonged exposure to high levels of radiation damage the polymers (which might be a real problem when considering biological polymer samples – proteins, for example).
On the other hand, to resolve smaller polymers and structurals subtleties, one cannot always resort to using the long-wavelength rays, as the diffraction limit comes into play. | 7 | Physical Chemistry |
De Silva and McClenaghan designed a proof-of-principle arithmetic device based on molecular logic gates. As depicted in Figure 10 A, Compound A is a push-pull olefin with the top receptor containing four carboxylic acid anion groups (and non-disclosed counter cations) capable of binding to calcium. The bottom part is a quinoline molecule which is a receptor for hydrogen ions. The logic gate operates as follows. Without any chemical input of Ca or H, the chromophore shows a maximum absorbance in UV/VIS spectroscopy at 390 nm. When calcium is introduced a hypsochromic shift (blue shift) takes place and the absorbance at 390 nm decreases. Likewise, addition of protons causes a bathochromic shift (red shift), and when both cations are in the water, the net result is absorption at the original 390 nm wavelength. This system represents an XNOR logic gate in absorption and an XOR logic gate in transmittance.
In another XOR logic gate system, the chemistry is based on the pseudorotaxane depicted in Figure 11. In organic solution the electron-deficient diazapyrenium salt (rod) and the electron-rich 2,3-dioxynaphthalene units of the crown ether (ring) self-assemble by formation of a charge transfer complex. An added tertiary amine like tributylamine forms a 1:2 adduct with the diazapyrene and the complex gets dethreaded. This process is accompanied by an increase in emission intensity at 343 nm resulting from freed crown ether. Added trifluoromethanesulfonic acid reacts with the amine and the process is reverted. Excess acid locks the crown ether by protonation and again the complex is de-threaded. | 6 | Supramolecular Chemistry |
Mikhail Semyonovich Tsvet, also spelt Tsvett, Tswett, Tswet, Zwet, and Cvet (Russian: Михаил Семёнович Цвет; 14 May 1872 – 26 June 1919) was a Russian-Italian botanist who invented chromatography. His last name is Russian for "colour" and is also the root word of "flower." | 3 | Analytical Chemistry |
In the study of heat transfer, critical heat flux (CHF) is the heat flux at which boiling ceases to be an effective form of transferring heat from a solid surface to a liquid. | 7 | Physical Chemistry |
The biopolymer poly-3-hydroxybutyrate (PHB) is a polyester produced by certain bacteria processing glucose, corn starch or wastewater. Its characteristics are similar to those of the petroplastic polypropylene (PP). PHB production is increasing. The South American sugar industry, for example, has decided to expand PHB production to an industrial scale. PHB is distinguished primarily by its physical characteristics. It can be processed into a transparent film with a melting point higher than 130 degrees Celsius, and is biodegradable without residue. | 7 | Physical Chemistry |
Selenols are important in certain biological processes. Three enzymes found in mammals contain selenols at their active sites: glutathione peroxidase, iodothyronine deiodinase, and thioredoxin reductase. The selenols in these proteins are part of the essential amino acid selenocysteine. The selenols function as reducing agents to give selenenic acid derivative (), which in turn are re-reduced by thiol-containing enzymes. Methaneselenol (commonly named "methylselenol") (), which can be produced in vitro by incubating selenomethionine with a bacterial methionine gamma-lyase (METase) enzyme, by biological methylation of selenide ion or in vivo by reduction of methaneseleninic acid (), has been invoked to explain the anticancer activity of certain organoselenium compounds. Precursors of methaneselenol are under active investigation in cancer prevention and therapy. In these studies, methaneselenol is found to be more biologically active than ethaneselenol () or 2-propaneselenol (). | 0 | Organic Chemistry |
A fourth international conference on the Gaia hypothesis, sponsored by the Northern Virginia Regional Park Authority and others, was held in October 2006 at the Arlington, VA campus of George Mason University.
Martin Ogle, Chief Naturalist, for NVRPA, and long-time Gaia hypothesis proponent, organized the event. Lynn Margulis, Distinguished University Professor in the Department of Geosciences, University of Massachusetts-Amherst, and long-time advocate of the Gaia hypothesis, was a keynote speaker. Among many other speakers: Tyler Volk, co-director of the Program in Earth and Environmental Science at New York University; Dr. Donald Aitken, Principal of Donald Aitken Associates; Dr. Thomas Lovejoy, President of the Heinz Center for Science, Economics and the Environment; Robert Corell, Senior Fellow, Atmospheric Policy Program, American Meteorological Society and noted environmental ethicist, J. Baird Callicott. | 9 | Geochemistry |
Buffer capacity is a quantitative measure of the resistance to change of pH of a solution containing a buffering agent with respect to a change of acid or alkali concentration. It can be defined as follows:
where is an infinitesimal amount of added base, or
where is an infinitesimal amount of added acid. pH is defined as −log[H], and d(pH) is an infinitesimal change in pH.
With either definition the buffer capacity for a weak acid HA with dissociation constant K can be expressed as
where [H] is the concentration of hydrogen ions, and is the total concentration of added acid. K is the equilibrium constant for self-ionization of water, equal to 1.0. Note that in solution H exists as the hydronium ion HO, and further aquation of the hydronium ion has negligible effect on the dissociation equilibrium, except at very high acid concentration.
This equation shows that there are three regions of raised buffer capacity (see figure 2).
* In the central region of the curve (coloured green on the plot), the second term is dominant, and Buffer capacity rises to a local maximum at pH = pK. The height of this peak depends on the value of pK. Buffer capacity is negligible when the concentration [HA] of buffering agent is very small and increases with increasing concentration of the buffering agent. Some authors show only this region in graphs of buffer capacity. Buffer capacity falls to 33% of the maximum value at pH = pK ± 1, to 10% at pH = pK ± 1.5 and to 1% at pH = pK ± 2. For this reason the most useful range is approximately pK ± 1. When choosing a buffer for use at a specific pH, it should have a pK value as close as possible to that pH.
* With strongly acidic solutions, pH less than about 2 (coloured red on the plot), the first term in the equation dominates, and buffer capacity rises exponentially with decreasing pH: This results from the fact that the second and third terms become negligible at very low pH. This term is independent of the presence or absence of a buffering agent.
* With strongly alkaline solutions, pH more than about 12 (coloured blue on the plot), the third term in the equation dominates, and buffer capacity rises exponentially with increasing pH: This results from the fact that the first and second terms become negligible at very high pH. This term is also independent of the presence or absence of a buffering agent. | 7 | Physical Chemistry |
When carbon dioxide is the substrate, the product of the carboxylase reaction is an unstable six-carbon phosphorylated intermediate known as 3-keto-2-carboxyarabinitol-1,5-bisphosphate, which decays rapidly into two molecules of glycerate-3-phosphate. This product, also known as 3-phosphoglycerate, can be used to produce larger molecules such as glucose.
When molecular oxygen is the substrate, the products of the oxygenase reaction are phosphoglycolate and 3-phosphoglycerate. Phosphoglycolate is recycled through a sequence of reactions called photorespiration, which involves enzymes and cytochromes located in the mitochondria and peroxisomes (this is a case of metabolite repair). In this process, two molecules of phosphoglycolate are converted to one molecule of carbon dioxide and one molecule of 3-phosphoglycerate, which can reenter the Calvin cycle. Some of the phosphoglycolate entering this pathway can be retained by plants to produce other molecules such as glycine. At ambient levels of carbon dioxide and oxygen, the ratio of the reactions is about 4 to 1, which results in a net carbon dioxide fixation of only 3.5. Thus, the inability of the enzyme to prevent the reaction with oxygen greatly reduces the photosynthetic capacity of many plants. Some plants, many algae, and photosynthetic bacteria have overcome this limitation by devising means to increase the concentration of carbon dioxide around the enzyme, including carbon fixation, crassulacean acid metabolism, and the use of pyrenoid.
Rubisco side activities can lead to useless or inhibitory by-products. Important inhibitory by-products include xylulose 1,5-bisphosphate and glycero-2,3-pentodiulose 1,5-bisphosphate, both caused by "misfires" halfway in the enolisation-carboxylation reaction. In higher plants, this process causes RuBisCO self-inhibition, which can be triggered by saturating and RuBP concentrations and solved by Rubisco activase (see below). | 5 | Photochemistry |
The research shortened photosynthetic pathways in tobacco. Engineered crops grew taller and faster, yielding up to 40% more biomass. The study employed synthetic biology to construct new metabolic pathways and assessed their efficiency with and without transporter RNAi. The most efficient pathway increased light-use efficiency by 17%. | 5 | Photochemistry |
Wood particles used to make various types of products rely on particle-size analysis to maintain high quality standards. By doing so, companies reduce waste and become more productive. | 3 | Analytical Chemistry |
The viral vectors described above have natural host cell populations that they infect most efficiently. Retroviruses have limited natural host cell ranges, and although adenovirus and adeno-associated virus are able to infect a relatively broader range of cells efficiently, some cell types are resistant to infection by these viruses as well. Attachment to and entry into a susceptible cell is mediated by the protein envelope on the surface of a virus. Retroviruses and adeno-associated viruses have a single protein coating their membrane, while adenoviruses are coated with both an envelope protein and fibers that extend away from the surface of the virus. The envelope proteins on each of these viruses bind to cell-surface molecules such as heparin sulfate, which localizes them upon the surface of the potential host, as well as with the specific protein receptor that either induces entry-promoting structural changes in the viral protein, or localizes the virus in endosomes wherein acidification of the lumen induces this refolding of the viral coat. In either case, entry into potential host cells requires a favorable interaction between a protein on the surface of the virus and a protein on the surface of the cell.
For the purposes of gene therapy, one might either want to limit or expand the range of cells susceptible to transduction by a gene therapy vector. To this end, many vectors have been developed in which the endogenous viral envelope proteins have been replaced by either envelope proteins from other viruses, or by chimeric proteins. Such chimera would consist of those parts of the viral protein necessary for incorporation into the virion as well as sequences meant to interact with specific host cell proteins. Viruses in which the envelope proteins have been replaced as described are referred to as pseudotyped viruses. For example, the most popular retroviral vector for use in gene therapy trials has been the lentivirus Simian immunodeficiency virus coated with the envelope proteins, G-protein, from Vesicular stomatitis virus. This vector is referred to as VSV G-pseudotyped lentivirus, and infects an almost universal set of cells. This tropism is characteristic of the VSV G-protein with which this vector is coated. Many attempts have been made to limit the tropism of viral vectors to one or a few host cell populations. This advance would allow for the systemic administration of a relatively small amount of vector. The potential for off-target cell modification would be limited, and many concerns from the medical community would be alleviated. Most attempts to limit tropism have used chimeric envelope proteins bearing antibody fragments. These vectors show great promise for the development of "magic bullet" gene therapies. | 1 | Biochemistry |
It is assumed that the Beer–Lambert law applies.
where is the optical path length, is a molar absorbance at unit path length and is a concentration. More than one of the species may contribute to the absorbance. In principle absorbance may be measured at one wavelength only, but in present-day practice it is common to record complete spectra. | 7 | Physical Chemistry |
Photophoresis denotes the phenomenon that small particles suspended in gas (aerosols) or liquids (hydrocolloids) start to migrate when illuminated by a sufficiently intense beam of light. The existence of this phenomenon is owed to a non-uniform distribution of temperature of an illuminated particle in a fluid medium. Separately from photophoresis, in a fluid mixture of different kinds of particles, the migration of some kinds of particles may be due to differences in their absorptions of thermal radiation and other thermal effects collectively known as thermophoresis. In laser photophoresis, particles migrate once they have a refractive index different from their surrounding medium. The migration of particles is usually possible when the laser is slightly or not focused. A particle with a higher refractive index compared to its surrounding molecule moves away from the light source due to momentum transfer from absorbed and scattered light photons. This is referred to as a radiation pressure force. This force depends on light intensity and particle size but has nothing to do with the surrounding medium. Just like in Crookes radiometer, light can heat up one side and gas molecules bounce from that surface with greater velocity, hence push the particle to the other side. Under certain conditions, with particles of diameter comparable to the wavelength of light, the phenomenon of a negative indirect photophoresis occurs, due to the unequal heat generation on the laser irradiation between the back and front sides of particles, this produces a temperature gradient in the medium around the particle such that molecules at the far side of the particle from the light source may get to heat up more, causing the particle to move towards the light source.
If the suspended particle is rotating, it will also experience the Yarkovsky effect.
Discovery of photophoresis is usually attributed to Felix Ehrenhaft in the 1920s, though earlier observations were made by others including Augustin-Jean Fresnel. | 7 | Physical Chemistry |
Alkaliphiles promise several interesting uses for biotechnology and future research. Alkaliphilic methods of regulating pH and producing ATP are of interest in the scientific community. However, perhaps the greatest area of interest from alkaliphiles lies in their enzymes: alkaline proteases; starch-degrading enzymes; cellulases; lipases; xylanases; pectinases; chitinases and their metabolites, including: 2-phenylamine; carotenoids; siderophores; cholic acid derivatives and organic acids. It is hoped that further research into alkaliphilic enzymes will allow scientists to harvest alkaliphiles' enzymes for use in basic conditions. Research aimed at discovering alkaliphile-produced antibiotics showed some success, yet has been held at bay by the fact that some products produced at high pH are unstable and unusable at a physiological pH range. | 1 | Biochemistry |
The extended double-stranded adapters are cleaved by HpyCH4III at a specific restriction site located at 3’ side of the tag sequence and will result in a 3’-dT overhang that will be ligated to the 3’-dA overhang on DNA libraries in the adapter ligation step (Figure 1). | 1 | Biochemistry |
Anomers can be interconverted through a process known as mutarotation. The anomeric effect more accurately called the endo-anomeric effect is the propensity for heteroatoms at C-1 to be oriented axially. This is counter intuitive as one would expect the equatorially anomer to be the thermodynamic product. This effect has been rationalized through dipole–dipole repulsion and n–σ* arguments. | 0 | Organic Chemistry |
Levorphanol is the INN, BAN, and DCF. As the medically used tartrate salt, the drug is also known as levorphanol tartrate (USAN, BANM). The former developmental code name of levorphanol at Roche was Ro 1-5431. | 4 | Stereochemistry |
* Hoerr, John P. And the Wolf Finally Came: The Decline of the American Steel Industry (1988) [https://www.amazon.com/Wolf-Finally-Came-American-Industry/dp/0822953986/ excerpt and text search]
* Hogan, William T. Economic History of the Iron and Steel Industry in the United States (5 vol 1971) monumental detail
* Ingham, John N. The Iron Barons: A Social Analysis of an American Urban Elite, 1874-1965 (1978)
* Krass, Peter. Carnegie (2002). .
* Livesay, Harold C. Andrew Carnegie and the Rise of Big Business, 2nd Edition (1999). .
* Misa, Thomas J. A Nation of Steel: The Making of Modern America, 1865–1925 (1995) Chapter 1 "[http://www.tc.umn.edu/~tmisa//NOS/1.1_intro.html The Dominance of Rails]"
* Nasaw, David. Andrew Carnegie (The Penguin Press, 2006).
* Paskoff, Paul F. Iron and Steel in the Nineteenth Century (Encyclopedia of American Business History and Biography) (1989) 385 pp; biographies and brief corporate histories
* Rogers, Robert P. An Economic History of the American Steel Industry (2009) [https://www.amazon.com/Economic-American-Industry-Routledge-Explorations/dp/0415777607/ excerpt and text search]
* Scamehorn, H. Lee. Mill & Mine: The Cf&I in the Twentieth Century University of Nebraska Press, 1992
* Scheuerman, William. The Steel Crisis: The Economics and Politics of a Declining Industry (1986)
* Skrabec Jr, Quentin R. The Carnegie Boys: The Lieutenants of Andrew Carnegie that Changed America (McFarland, 2012).
* Seely, Bruce E., ed The Iron and Steel Industry in the 20th Century (1994) (Encyclopedia of American Business History and Biography)
* Temin, Peter. Iron and Steel in Nineteenth-Century America, An Economic Inquiry (1964)
* Wall, Joseph Frazier. Andrew Carnegie (1989). .
* Warren, Kenneth, Big Steel: The First Century of the United States Steel Corporation, 1901–2001. (University of Pittsburgh Press, 2001) [https://web.archive.org/web/20070211162744/http://eh.net/bookreviews/library/0558.shtml online review]
* Warren, Kenneth. Bethlehem Steel: Builder and Arsenal of America (2010) [https://www.amazon.com/gp/reader/0822960672/ excerpt and text search]
* Warren, Kenneth. The American Steel Industry, 1850–1970: A Geographical Interpretation (1973) ()
* Whaples, Robert. "Andrew Carnegie", EH.Net Encyclopedia of Economic and Business History [https://web.archive.org/web/20061216082029/http://eh.net/encyclopedia/article/Whaples.Carnegie online]
* [https://web.archive.org/web/20110717180737/http://www.ussteel.com/corp/about.htm#The%20History%20of%20United%20States%20Steel U.S. Steel's History of U.S. Steel]
* Urofsky, Melvin I. Big Steel and the Wilson Administration: A Study in Business-Government Relations (1969) | 8 | Metallurgy |
Structural isomers have the same number of atoms of each element (hence the same molecular formula), but the atoms are connected in distinct ways. | 4 | Stereochemistry |
Lithol Rubine BK is a reddish synthetic azo dye. It has the appearance of a red powder and is magenta when printed. It is slightly soluble in hot water, insoluble in cold water, and insoluble in ethanol. When dissolved in dimethylformamide, its absorption maximum lies at about 442 nm. It is usually supplied as a calcium salt. It is prepared by azo coupling with 3-hydroxy-2-naphthoic acid.
It is used to dye plastics, paints, printing inks, and for textile printing. It is normally used as a standard magenta in the three and four color printing processes.
When used as a food dye, it has E number E180. It is used to color cheese rind, and it is a component in some lip balms. | 0 | Organic Chemistry |
There are four basic techniques for acquiring the three-dimensional (x, y, λ) dataset of a hyperspectral cube. The choice of technique depends on the specific application, seeing that each technique has context-dependent advantages and disadvantages. | 7 | Physical Chemistry |
RIP140 is part of the chain by which tumors can cause cachexia.
Levels of RIP140 expression in various tissues varies during aging in mice, suggesting changes in metabolic function. RIP140 is implicated in certain human disease processes. In morbid obesity, RIP140 levels are down-regulated in visceral adipose tissue. In breast cancer, RIP140 is involved in regulation of E2F1, an oncogene which discriminates between luminal and basal types of tumours. RIP140 has an influence upon cancer phenotype and prognosis. In addition, RIP140 has a role in inflammation, since it acts as a coactivator for NFkappaB/RelA-dependent cytokine gene expression. Lack of RIP140 leads to an inhibition of proinflammatory pathways in macrophages. | 1 | Biochemistry |
CaCrO is a frustrated kagome bilayer magnet, which does not develop long-range order even below 1 K, and has a diffuse spectrum of gapless excitations. | 7 | Physical Chemistry |
: M–R + M–X → M–X + M–R.
In redox-transmetalation/ligand exchange the ligands of two metal complexes switch places with each other, bonding with the other metal center. The R ligand can be an alkyl, aryl, alkynyl, or allyl group and the X ligand can be a halogen, pseudo-halogen, alkyl, or aryl group. The reaction can proceed by two possible intermediate steps. The first is an associative intermediate, where the R and X ligands bridge the two metals, stabilizing the transition state. The second and less common intermediate is the formation of a cation where R is bridging the two metals and X is anionic. The RTLE reaction proceeds in a concerted manner. Like in RT reactions, the reaction is driven by electronegativity values. The X ligand is attracted to highly electropositive metals. If M is a more electropositive metal than M, it is thermodynamically favorable for the exchange of the R and X ligands to occur. | 0 | Organic Chemistry |
RT-PCR is commonly used in research methods to measure gene expression. For example, Lin et al. used qRT-PCR to measure expression of Gal genes in yeast cells. First, Lin et al. engineered a mutation of a protein suspected to participate in the regulation of Gal genes. This mutation was hypothesized to selectively abolish Gal expression. To confirm this, gene expression levels of yeast cells containing this mutation were analyzed using qRT-PCR. The researchers were able to conclusively determine that the mutation of this regulatory protein reduced Gal expression. Northern blot analysis is used to study the RNA's gene expression further. | 1 | Biochemistry |
* Due to the structure, the pressure difference is theoretically limited to atmospheric pressure (1 bar), and in practice somewhat lower.
* Besides the drum, other accessories, for example, agitators and vacuum pump, vacuum receivers, slurry pumps are required.
* The discharge cake contains residual moisture.
* The cake tends to crack due to their air drawn through by the vacuum system, so that washing and drying are not efficient.
* High energy consumption by the vacuum pump. | 3 | Analytical Chemistry |
Screening falls under two general categories: dry screening, and wet screening. From these categories, screening separates a flow of material into grades, these grades are then either further processed to an intermediary product or a finished product. Additionally, the machines can be categorized into a moving screen and static screen machines, as well as by whether the screens are horizontal or inclined. | 8 | Metallurgy |
A glide plane is a reflection in a plane, followed by a translation parallel with that plane. This is noted by , , or , depending on which axis the glide is along. There is also the glide, which is a glide along the half of a diagonal of a face, and the glide, which is a fourth of the way along either a face or space diagonal of the unit cell. The latter is called the diamond glide plane as it features in the diamond structure. In 17 space groups, due to the centering of the cell, the glides occur in two perpendicular directions simultaneously, i.e. the same glide plane can be called b or c, a or b, a or c. For example, group Abm2 could be also called Acm2, group Ccca could be called Cccb. In 1992, it was suggested to use symbol e for such planes. The symbols for five space groups have been modified: | 4 | Stereochemistry |
The illustrations to the right shows the main regions that may be present in a glow discharge. Regions described as "glows" emit significant light; regions labeled as "dark spaces" do not. As the discharge becomes more extended (i.e., stretched horizontally in the geometry of the illustrations), the positive column may become striated. That is, alternating dark and bright regions may form. Compressing the discharge horizontally will result in fewer regions. The positive column will be compressed while the negative glow will remain the same size, and, with small enough gaps, the positive column will disappear altogether. In an analytical glow discharge, the discharge is primarily a negative glow with dark region above and below it. | 3 | Analytical Chemistry |
Cicadia wings have a surface of hexagonally close packed nanopillars that have been shown to have self-cleaning properties. Similarly templated nanopatterned silica arrays have been shown to have hydrophobic, anti-reflective, and self-cleaning properties. These silica arrays begin as non-close packed monolayers, and are patterned in a series of etching steps involving chlorine and oxygen reactive ion etching, and a hydrofluoric acid wash. These properties have implicated that this surface pattern may prove to be useful in solar cell applications. Biomimetic materials based on the cicadia wing have also been made from polytetrafluoroethylene films with carbon/epoxy supports treated with argon and oxygen ion beams. A nanoimprint patterned surface based on the cicadia wings has been made by electrochemically templating and aluminum sheet with alumina oxide, and using this template to pattern a polymer surface. | 7 | Physical Chemistry |
The most critical eyespot proteins are the photoreceptor proteins that sense light. The photoreceptors found in unicellular organisms fall into two main groups: flavoproteins and retinylidene proteins (rhodopsins). Flavoproteins are characterized by containing flavin molecules as chromophores, whereas retinylidene proteins contain retinal. The photoreceptor protein in Euglena is likely a flavoprotein. In contrast, Chlamydomonas phototaxis is mediated by archaeal-type rhodopsins.
Besides photoreceptor proteins, eyespots contain a large number of structural, metabolic and signaling proteins. The eyespot proteome of Chlamydomonas cells consists of roughly 200 different proteins. | 1 | Biochemistry |
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