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Rhodizonic acid is a chemical compound with formula or . It can be seen as a twofold enol and fourfold ketone of cyclohexene, more precisely 5,6-dihydroxycyclohex-5-ene-1,2,3,4-tetrone. is usually obtained in the form of a dihydrate . The latter is actually 2,3,5,5,6,6-hexahydroxycyclohex-2-ene-1,4-dione, where two of the original ketone groups are replaced by two pairs of geminal diols. The orange to deep-red and highly hygroscopic anhydrous acid can be obtained by low-pressure sublimation of the dihydrate. Like many other enols, rhodizonic acid can lose the hydrogen cations H from the hydroxyls (p"K" = , p"K" = at 25 °C), yielding the hydrogenrhodizonate anion and the rhodizonate anion . The latter is aromatic and symmetric, as the double bond and the negative charges are delocalized and evenly distributed over the six CO units. Rhodizonates tend to have various shades of red, from yellowish to purplish. has been used in chemical assays for barium, lead, and other metals. In particular, the sodium rhodizonate test can be used to detect gunshot residue (which contains lead) in a subject's hands, and to distinguish arrow wounds from gunshot wounds for hunting regulation enforcement. was discovered by Austrian chemist Johann Heller in 1837, by analyzing the products of heating a mixture of potassium carbonate and charcoal. The name comes from Greek ("rhodizō", "to tinge red"), on account of the color of its salts | https://en.wikipedia.org/wiki?curid=23805592 |
Rhodizonic acid Rhodizonates tend to have various shades of red, from yellowish to purplish, in transmitted light, with a greenish luster in reflected light. Potassium rhodizonate can be prepared with good yield and purity by oxidizing inositol with nitric acid and reacting the result with potassium acetate in the presence of oxygen. The rhodizonate crystallizes out of the solution due to its relative insolubility in water. Sodium rhodizonate is dark brown and stable when dry, but the aqueous solution decomposes in a few days, even in the refrigerator. Lead rhodizonate is dark violet. is a member of a chain of oxidation products: benzenehexol , tetrahydroxybenzoquinone (THBQ) , rhodizonic acid , and cyclohexanehexone . Lithium rhodizonate, together with salts of THBQ and benzenehexol, has been considered for possible use in rechargeable electrical batteries. The monovalent anion has been detected in mass spectrometry experiments. and the rhodizonate anion can lose one of the CO units to yield croconic acid and the croconate anion , respectively, by mechanisms that are still imperfectly known. In basic solutions (pH > 10), rhodizonic acid quickly converts to the THBQ anion in the absence of oxygen, and to croconic acid in its presence. At pH 8.3 and exposure to light, solutions are stable for days in the absence of oxygen, and decompose to croconic acid and other products (possibly including cyclohexanehexone or dodecahydroxycyclohexane) in its presence | https://en.wikipedia.org/wiki?curid=23805592 |
Rhodizonic acid In solution, the acid and the hydrogenrhodizonate ion are mostly hydrated, with some of the carbonyl groups >C=O replaced by geminal hydroxyls, . In anhydrous rubidium rhodizonate , the rhodizonate anions are stacked in parallel columns, as are the rubidium ions. In the plane perpendicular to the columns, these are arranged as two interleaved hexagonal grids. The anions are planar. Anhydrous potassium rhodizonate has a distinct but similar structure. The anions and cations are arranged in alternate planes. Within each plane, the anions are arranged in an hexagonal grid. Each potassium ion is arranged so that it connects symmetrically to eight oxygens of four anions, two from each adjacent plane. The anions are slightly twisted in the "boat" shape (with 0.108 Å of rms deviation from mean plane). Sodium rhodizonate has the same structure, with slightly more distorted anions (0.113 Å rms) In solution, the rhodizonate anion is not hydrated. | https://en.wikipedia.org/wiki?curid=23805592 |
Journal of Cheminformatics The is a peer-reviewed open access scientific journal that covers cheminformatics and molecular modelling. It was established in 2009 with David Wild (Indiana University) and Christoph Steinbeck (then at EMBL-EBI) as founding editors-in-chief, and was originally published by Chemistry Central. At the end of 2015, the Chemistry Central brand was retired and its titles, including "Journal of Cheminformatics", were merged with the SpringerOpen portfolio of open access journals. , the editors-in-chief are Rajarshi Guha (National Center for Advancing Translational Sciences) and Egon Willighagen (Maastricht University). The journal has issued a few special issues ("article collections") in 2011 and 2012, covering topics like PubChem3D, the Resource Description Framework, and the International Chemical Identifier. The journal is abstracted and indexed in: According to the "Journal Citation Reports", the journal has a 2018 impact factor of 4.154. The most cited paper is on a cross-platform molecule editor and visualizer called Avogadro, which has been cited more than 1800 times as of September 2019 according to the Web of Science. | https://en.wikipedia.org/wiki?curid=23814141 |
Diazirine Diazirines are a class of organic molecules consisting of a carbon bound to two nitrogen atoms, which are double-bonded to each other, forming a cyclopropene-like ring, 3"H"-diazirene. Upon irradiation with ultraviolet light, diazirines form reactive carbenes, which can insert into C-H, N-H, and O-H bonds. Hence, diazirines have grown in popularity as small photo-reactive crosslinking reagents. They are often used in photoaffinity labeling studies to observe a variety of interactions, including ligand-receptor, ligand-enzyme, protein-protein, and protein-nucleic acid interactions. A number of methods exist in the literature for the preparation of diazirines, which begin from a variety of reagents. Generally, synthetic schemes that begin with ketones involve conversion of the ketone with the desired substituents to diaziridines. These diaziridenes are then subsequently oxidized to form the desired diazirines. Diaziridines can be prepared from ketones by oximation, followed by tosylation (or mesylation), and then finally by treatment with ammonia. Generally, oximation reactions are performed by reacting the ketone with hydroxylammonium chloride under heat in the presence of a base such as pyridine. Subsequent tosylation or mesylation of the alpha substituted oxygen with tosyl or mesyl chloride in the presence of base yields the tosyl or mesyl oxime. The final treatment of the tosyl or mesyl oxime with ammonia produces the diaziridine | https://en.wikipedia.org/wiki?curid=23814189 |
Diazirine Diaziridines can be also produced directly by the reaction of ketones with ammonia in the presence of an aminating agent such as a monochloramine or hydroxyl amine O-sulfonic acid. Diaziridines can be oxidized to diazirines by a number of methods. These include oxidation by chromium based reagents such as the Jones oxidation, oxidation by iodine and triethylamine, oxidation by silver oxide, oxidation by oxalyl chloride, or even electrochemical oxidation on a platinum-titanium anode. Diazirines can be alternatively formed in a one-pot process using the Graham reaction. In these schemes, amidines can be directly converted to diazirines by hypohalite oxidation. This reaction yields a halogenated diazirine, which can further be modified. The resulting aforementioned halodiazirine can undergo an exchange reaction to further functionalize the diazirene. In these reactions, anion nucleophiles, such as tetra-n-butylammonium fluoride or methoxytetra-n-butylammonium, can replace the halogen substituents yielding a fluorodiazirine or methoxydiazirine respectively. Upon irradiation with UV light, diazirines form reactive carbene species. The carbene may exist in the singlet form, in which the two free electrons occupy the same orbital, or the triplet form, with two unpaired electrons in different orbitals. The substituents on the diazirine affect which carbene species is generated upon irradiation and subsequent photolytic cleavage | https://en.wikipedia.org/wiki?curid=23814189 |
Diazirine substituents that are electron donating in nature can donate electron density to the empty p-orbital of the carbene that will be formed, and hence can stabilize the singlet state. For example, phenyldiazirine produces phenylcarbene in the singlet carbene state whereas p-nitrophenylchlorodiazirine or trifluorophenyldiazirine produce the respective triplet carbene products. Electron donating substituents can also encourage photoisomerization to the linear diazo compound, rather than the singlet carbene, and hence these compounds are unfavorable for use in biological assays. On the other hand, trifluoroaryldiazirines in particular show favorable stability and photolytic qualities and are most commonly used in biological applications. Carbenes produced from diazirines are quickly quenched by reaction with water molecules, and hence yields for photoreactive crosslinking assays are often low. Yet, as this feature minimizes unspecific labeling, it is actually an advantage of using diazirines. Diazirines are often used as photoreactive crosslinking reagents, as the reactive carbenes they form upon irradiation with UV light can insert into C-H, N-H, and O-H bonds. This results in proximity dependent labeling of other species with the diazirine containing compound | https://en.wikipedia.org/wiki?curid=23814189 |
Diazirine Diazirines are often preferred to other photoreactive crosslinking reagents due to their smaller size, longer irradiation wavelength, short period of irradiation required, and stability in the presence of various nucleophiles, and in both acidic and basic conditions. Benzophenones, which form reactive triplet carbonyl species upon irradiation, often require long periods of irradiation which can result in non-specific labeling, and moreover are often inert to various polar solvents. Aryl azides require a low wavelength of irradiation, which can damage the biological macromolecules under investigation. Diazirines are widely used in receptor labeling studies. This is because diazirine-containing analogs of various ligands can be synthesized and incubated with their respective receptors, and then subsequently exposed to light to produce reactive carbenes. The carbene will covalently bond to residues in the binding site of the receptor. The carbene compound may include a bioorthogonal tag or handle by which the protein of interest can be isolated. The protein can then be digested and sequenced by mass spectrometry in order to the identity which residues the carbene containing ligand is bound to, and hence the identity of the binding site in the receptor. Examples of diazirines used in receptor labeling studies include: In a manner analogous to receptor labeling, diazirine containing compounds that are analogs of natural substrates have also been used to identify binding pockets of enzymes | https://en.wikipedia.org/wiki?curid=23814189 |
Diazirine Examples include: Diazirines have been used in photoaffinity labeling experiments involving nucleic acids as well. Examples include: Diazirines have also been used to study protein lipid interactions, for example the interaction of various sphingolipids with proteins in vivo. | https://en.wikipedia.org/wiki?curid=23814189 |
Norbert Bischofberger Dr. (born 10 January 1956 in Mellau, Austria) is an Austrian scientist and one of the inventors of the antiviral drug Tamiflu generically known as oseltamivir, which is, as of 2009, the only oral medication on the market to treat influenza A and B as well as the 2009 Pandemic H1N1 (swine flu), the spread of which caused an ongoing pandemic in 2009. Bischofberger was the Executive Vice President, Research and Development and Chief Scientific Officer at Gilead Sciences, a biopharmaceutical company specializing in antivirals. Bischofberger has received a Bachelor of Science in Chemistry from the University of Innsbruck, a Ph.D. in Organic Chemistry at the ETH Zurich with Oskar Jeger, and has done postdoctoral work at Harvard University with George M. Whitesides and Syntex Research. He worked as part of the DNA synthesis group at Genentech from 1986–1990, before joining Gilead in 1990 as Director of Organic Chemistry. In 1993, he began work, as head of a team, to create Tamiflu. In 1996, clinical studies were carried out on the drug, which was the first orally active commercially developed anti-influenza medication. Explaining the motivation behind this, he said, "We decided to create a pill and not a medication to inhale because especially people who suffer from influenza struggle with breathing difficulties. And the agent would only reach the lung," Three years later, the right to market and develop Tamiflu were sold to Roche, with Bischofberger and Gilead retaining the intellectual rights to it | https://en.wikipedia.org/wiki?curid=23815844 |
Norbert Bischofberger Bischofberger has publicly displayed pessimism over the risk viruses pose, saying, "I think the threat by new bacterial or viral agents is higher than the potential of a nuclear war." | https://en.wikipedia.org/wiki?curid=23815844 |
Filter strip Filter strips, also referred to as buffer strips, are small, edge-of-field tracts of vegetated land that are used to reduce the contamination of surface water. They are primarily used in agriculture to control non-point source pollution, however, they may also be used to reduce sediment in storm water runoff from construction sites. There are several types of filter strips including vegetative filter strips, forested riparian buffers, and wind buffers. In agriculture, they are highly effective in reducing the concentration of nitrogen (N) and phosphorus (P) in runoff into surface water and are also effective in reducing sediment erosion and removing pesticides. This helps to prevent eutrophication and associated fishkills and loss of biodiversity. The use of filter strips is very common in developed countries and is required by law in some areas. The implementation and maintenance of filter strips is inexpensive and their use has been shown to be cost effective. Filter strips are primarily used in agriculture to control nonpoint source pollution. They function by decreasing the velocity of water, allowing runoff and dissolved inorganic molecules to infiltrate the soil. Vegetation then uptakes these inorganic molecules, notably nitrogen and phosphorus, reducing their concentrations in nearby surface water. Filter strips may also be used as sediment traps to reduce sediment in storm water runoff from construction sites | https://en.wikipedia.org/wiki?curid=23820249 |
Filter strip Eutrophication in a lake caused by nonpoint pollution from agriculture Filter strips are commonly used to prevent eutrophication in surface waters. Eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, directly caused by the over-enrichment of nitrogen and phosphorus; the source of which is overwhelmingly nonpoint pollution from agriculture. The excess of these nutrients leads to uncontrolled growth of plants and algae (and phytoplankton in saltwater environments). As they are decomposed by microorganisms, oxygen is depleted, resulting in hypoxia. This can lead to fishkills and the mass deaths of other fauna, creating a state of severely reduced biodiversity. By reducing the concentration of chemical fertilizers in surface water, filter strips have a positive effect on human health. Although elevated concentrations of phosphorus in water is not directly toxic to humans, nitrates poses a serious risk to human health. At high concentrations, the ingestion of nitrates can result in an acute condition known as methemoglobinemia in which the oxygen carrying capacity of hemoglobin is impaired. Infants are especially susceptible, which is why the disease is colloquially referred to as "blue baby syndrome." In areas where humans rely on fishing or aquafarming for nourishment, decreased populations of fish and shellfish can lead to undernourishment and associated diseases. Vegetative filter strips are small, edge-of-field tracts of vegetated land | https://en.wikipedia.org/wiki?curid=23820249 |
Filter strip This type of filter strip is planted with a perennial grass or legumes that have a high rate of nitrogen fixation. Several species are used. The most common grasses are switchgrass, orchardgrass, and tall fescue. Typical legumes are clovers and alfalfa. Prairie filter strips function in the same manner as vegetative filter strips, however they are populated with local prairie grasses. The use of prairie grass has some benefits, especially increased biodiversity, as opposed to vegetative filter strips, and their multilayered root systems and strong stems make them better suited for adverse weather. Like prairie filter strips, forested riparian buffers are filter strips that are not planted, but rather, are populated by indigenous trees and other flora. They are better able to support local terrestrial fauna. As opposed to undisturbed land, riparian buffers support a significantly greater number of avian and arthropod species. However, they are not able to support as large of a number of species as undisturbed land. Wind buffers (also referred to as windbreaks) are rows of planted trees or shrubs which are used to prevent soil erosion in fields. Additionally, they may be used to prevent the drifting of snow onto roadways and can reduce noise along highways. Filter strips are highly effective in reducing the concentration of nitrogen (N) and phosphorus (P) in runoff into surface water. Zhou et al | https://en.wikipedia.org/wiki?curid=23820249 |
Filter strip (2014) found that prairie filter strips reduced the concentration of nitrate, total nitrogen, and total phosphorus in runoff by 35%, 73%, and 82% respectively. Abu-Zreig, Majed, et al. (2003) found that vegetated filter strips were effective in reducing the concentration of phosphorus, with results ranging from 61% to 89% for 2m-wide filter strips and 15m-wide filter strips respectively. This indicates that filter strips are effective at even small widths. Filter strips have also been shown to be very effective in sediment trapping. A study of sediment removal found that prairie filter strips had a 96% sediment trapping efficiency over a 4-year period. As with nitrogen and phosphorus reduction, the sediment trapping efficiency of a filter strip varies by a number of factors, including subsurface conditions, surface conditions, and sediment characteristics. The use of filter strips is very common throughout the developed world. Their use is stipulated by law in some areas. Minnesota, for example, requires farmers to install a filter strip along all public bodies of water and drainage ditches. The main cost associated with filter strips is the decrease in yield due to a loss of cultivatable land. Other costs are those associated with creating, planting, and maintaining a filter strip. The annual private cost of maintaining two filter strips on a Missouri watershed was found to be $62.40/ac.(4046.86m), though cost varies by location due to different land values. | https://en.wikipedia.org/wiki?curid=23820249 |
ILPR The insulin-linked polymorphic region (ILPR) is a regulatory sequence on the insulin gene starting at position -363 upstream from the transcriptional start location of the 5' region and consists of multiple repeats of a ACA-GGGGT(G/C)(T/C)GGG consensus sequence. The polymorphic aspect of this region is due to three possible combinations of sequences according to their length: 700bp, 1600bp and 2500bp. | https://en.wikipedia.org/wiki?curid=23823532 |
Phosphine ligand Phosphine ligands are phosphines, compound of the formula PRR'R" (R, R', R" = H, alkyl, aryl, etc) that are used as ligands in metal complexes, often related to organometallic chemistry and homogeneous catalysis. These compounds are also used in other areas of chemistry. The most common phosphine ligands are of the type PR. They are three-fold symmetric with equivalent substituents. Some routine phosphine ligands are triphenylphosphine and trimethylphosphine. The triarylphosphines are usually white shelf-stable solids, whereas the trialkylphosphines are colorless liquids that tend to air-oxidize to the corresponding phosphine oxides (RPO). Such ligands can be classified according to their donor strength and steric bulk. These properties can be quantified by the Tolman electronic parameter and ligand cone angle, respectively. Generally alkyl phosphines are stronger bases and σ-donors. Common bidentate chelating phosphine ligands include dppe and dmpe, RPCHCHPR (R = Ph, Me, respectively). Tridentate triphosphines come in two classes, linear and tripodal. These ligands are both (confusingly) called triphos. The phenyl-substituted versions have the formula CHC(CHPPh) and PhP(CHCHPPh). Examples of tetradentate tripodal phosphines include tris[2-(diphenylphosphino)ethyl]phosphine (pp3). Two basic types of chiral phosphine ligands exist. These are of interest for asymmetric catalysis, e.g., asymmetric hydrogenation. Chiral diphosphines have been particularly popularized | https://en.wikipedia.org/wiki?curid=23827852 |
Phosphine ligand "P"-Chiral phosphines such as DIPAMP have three different phosphorus substituents. BINAP is a well known example of a C2-symmetric diphosphine which forms chiral complexes due to atropisomerism. | https://en.wikipedia.org/wiki?curid=23827852 |
Intravital microscopy is a form of microscopy that allows observing biological processes in live animals ("in vivo") at a high resolution that makes distinguishing between individual cells of a tissue possible. Before an animal can be used for intravital microscopy imaging it has to undergo a surgery involving implantation of an imaging window. For example, if researchers want to visualize liver cells of a live mouse they will implant an imaging window into mouse’s abdomen. Mice are the most common choice of animals for intravital microscopy but in special cases other rodents such as rats might be more suitable. Animals are always anesthetized throughout surgeries and imaging sessions. is used in several areas of research including neurology, immunology, stem cell and others. This technique is particularly useful to assess a progression of a disease or an effect of a drug. involves imaging cells of a live animal through an imaging window that is implanted into the animal tissue during a special surgery. The main advantage of intravital microscopy is that it allows imaging living cells while they are in the true environment of a complex multicellular organism. Thus, intravital microscopy allows researchers to study the behavior of cells in their natural environment or in vivo rather than in a cell culture. Another advantage of intravital microscopy is that the experiment can be set up in a way to allow observing changes in a living tissue of an organism over a period of time | https://en.wikipedia.org/wiki?curid=23843184 |
Intravital microscopy This is useful for many areas of research including immunology and stem cell research. <br> High quality of modern microscopes and imaging software also permits subcellular imaging in live animals that in turn allows studying cell biology at molecular level "in vivo". Advancements in fluorescent protein technology and genetic tools that enable controlled expression of a given gene at a specific time in a tissue of interest also played important role in intravital microscopy development. The possibility of generating appropriate transgenic mice is crucial for intravital microscopy studies. For example, in order to study the behavior of microglial cells in Alzheimer’s disease researchers will need to crossbreed a transgenic mouse that is a mouse model of Alzheimer’s disease with another transgenic mouse that is a mouse model for visualization of microglial cells. Cells need to produce a fluorescent protein to be visualized and this can be achieved by introducing a transgene. can be performed using several light microscopy techniques including widefield fluorescence, confocal, multiphoton, spinning disc microscopy and others. The main consideration for the choice of a particular technique is the penetration depth needed to image the area and the amount of cell-cell interaction details required. If the area of interest is located more than 50–100 µm below the surface or there is a need to capture small-scale interactions between cells, multiphoton microscopy is required | https://en.wikipedia.org/wiki?curid=23843184 |
Intravital microscopy Multiphoton microscopy provides considerably greater depth of penetration than single-photon confocal microscopy. Multiphoton microscopy also allows visualizing cells located underneath bone tissues such as cells of the bone marrow. The maximum depth for the imaging with multiphoton microscopy depends on the optical properties of the tissue and experimental equipment. The more homogenous the tissue is the better it is suited for intravital microscopy. More vascularized tissues are generally more difficult to image because red blood cells cause absorption and scattering of the microscope light beam. Fluorescence labeling of different cell lineages with differently coloured proteins allows visualizing cellular dynamics in a context of their microenvironment. If the image resolution is high enough (50 – 100 μm) it can be possible to use several images to generate 3D models of cellular interactions, including protrusions that cells make while extending toward each other. 3D models from time-lapse image sequences allow assessing speed and directionality of cellular movements. Vascular structures can also be reconstructed in 3D space and changes of their permeability can be monitored throughout a period of time as fluorescent signal intensity of dyes changes when vascular permeability does. High resolution intravital microscopy can be used to visualize spontaneous and transient events | https://en.wikipedia.org/wiki?curid=23843184 |
Intravital microscopy <br> It might be useful to pair up multiphoton and confocal microscopy as this allows getting more information from every imaging session. This includes visualization of more different cell types and structures to obtain more informative images and using a single animal to obtain images of all the different cell types and structures that are of interest for a given experiment. This latter is an example of The Three Rs principle implementation. In the past, intravital microscopy could only be used to image biological processes at tissue or single-cell levels. However, due to development of subcellular labeling techniques and advances in minimizing motion artifacts (errors generated by heartbeat, breath and peristaltic movements of an animal during imaging session) it is now becoming possible to image dynamics of intracellular organelles in some tissues. One of the main advantages of intravital microscopy is the opportunity to observe how cells interact with their microenvironment. However, visualization of all the cell types of the microenvironment is limited by the number of distinguishable fluorescent labels available. It is also widely accepted that some tissues such as brain can be visualized easier than others such as skeletal muscle. These differences occur due to variability in homogeneity and transparency of different tissues. In addition, generating transgenic mice with a phenotype of interest and fluorescent proteins in appropriate cell types is often challenging and time consuming | https://en.wikipedia.org/wiki?curid=23843184 |
Intravital microscopy Another problem associated with the use of transgenic mice is that it is sometimes difficult to interpret changes observed between a wild-type mouse and a transgenic mouse that represents the phenotype of interest. The reason for this is that genes of similar function can often compensate for the altered gene that leads to some degree of adaptation. | https://en.wikipedia.org/wiki?curid=23843184 |
DMPEA can refer to two subclasses of substituted phenethylamines: Dimethoxy-phenethylamines Dimethyl-phenethylamines | https://en.wikipedia.org/wiki?curid=23846773 |
Field emission probes are used in scanning electron microscopy for imaging. When a voltage is applied to these probes, electrons are emitted from the tips through a process known as field electron emission. When a body is subjected to ion milling in vacuum, we do not get to know about the geometry of the surface of the body. So to study it we will keep the field emission probes which will emit electrons as soon as a voltage is applied across it. This in turn will cause emission of secondary electrons from the surface of the body that is subjected to ion milling, by collecting these secondary emitted electrons we get a clear image of the surface of the ion milled body. This is the technique that is used in the or scanning electron microscope(SEM). There exist various well defined techniques for preparing field emission probes. Ideally, a field emission probe should be extremely sharp, possibly terminating in a single atom, in order to resolve details at the atomic level; it should have a small aspect ratio to reduce mechanical vibration while scanning, have a stable atomic configuration at its apex to yield reliable and reproducible images, and be clean to ensure a stable tunnel junction, since the presence of contaminants like oxides or etching by products could alter its metallic behavior. Our experimental setup helps us obtain tips with an apex radius of a few nanometres. There are various well-known methods to make field emission probes but still it is difficult to get an ideal probe. One of them is the Drop-off method | https://en.wikipedia.org/wiki?curid=23850454 |
Field emission probes Field emission electron microscope Scanning electron microscope Scanning tunneling microscope | https://en.wikipedia.org/wiki?curid=23850454 |
Alpha glucan α-Glucans (alpha-glucans) are polysaccharides of D-glucose monomers linked with glycosidic bonds of the alpha form. α-Glucans use cofactors in a cofactor site in order to activate a glucan phosphorylase enzyme. This enzyme causes a reaction that transfers a glucosyl portion between orthophosphate and α-I,4-glucan. The position of the cofoactors to the active sites on the enzyme are critical to the overall reaction rate thus, any alteration to the cofactor site leads to the disruption of the glucan binding site. Alpha-glucan is also commonly found in bacteria, yeasts, plants, and insects. Whereas the main pathway of α-glucan synthesis is via glycosidic bonds of glucose monomers, α-glucan can be comparably synthesized via the maltosyl transferase GlgE and branching enzyme GlgB. This alternative pathway is common in many bacteria, which use GlgB and GlgE or the GlgE pathway exclusively for the biosynthesis of α-glucan. The GlgE pathway is especially prominent in actinomycetes, such as mycobacteria and streptomycetes. However, α-glucans in mycobacteria have a slight variation in the length of linear chains, which point to the fact that the branching enzyme in mycobacteria makes shorter branches compared to glycogen synthesis. For organisms that can utilize both classic glycogen synthesis and the GlgE pathway, only GlgB enzyme is present, which indicates that the GlgB enzyme is shared between both pathways. Other uses for α-glucan have been developed based on its availability in bacteria | https://en.wikipedia.org/wiki?curid=23850944 |
Alpha glucan The accumulation of glycogen "Neisseria polysacchera" and other bacteria are able to use in α-glucan to catalyze glucose units to form α-1,4-glucan and liberating fructose in the process. To regulate carbohydrate metabolism, more resistant starch was necessary. An α-glucan coated starch molecule produced from "Neisseria polysacchera" was able to improve some of the physiochemical properties in comparison to raw normal starch, especially in loading efficiency of bioactive molecules. Alpha-glucan was used in conjunction with modified starch molecules that contained porous starch granules via hydrolysis with amylotic enzymes such as α-amylase, β-amylase, and glucoamylase. An α-glucan coating boasts protection from digestive environments, such as the small intestine, efficient encapsulation, and preservation rates. This design promotes the growth of the development of α-glucan-based bio-materials and many implications for its usage in food and pharmaceutical industries. Page that explains alpha-glucan linkages in starch. | https://en.wikipedia.org/wiki?curid=23850944 |
Linus Pauling Award The is an award recognizing outstanding achievement in chemistry. It is awarded annually by the Puget Sound, Oregon, and Portland sections of the American Chemical Society, and is named after the US chemist Linus Pauling (1901–1994), to whom it was first awarded in 1966. Another is given annually by the Chemistry Department at Buffalo State College. Source: ACS | https://en.wikipedia.org/wiki?curid=23854892 |
Catecholaminergic means "related to catecholamines". The catecholamine neurotransmitters include dopamine, epinephrine (adrenaline), and norepinephrine (noradrenaline). A catecholaminergic agent (or drug) is a chemical which functions to directly modulate the catecholamine systems in the body or brain. Examples include adrenergics and dopaminergics. | https://en.wikipedia.org/wiki?curid=23857643 |
Cortistatin can refer to: | https://en.wikipedia.org/wiki?curid=23860425 |
Isohydric principle The isohydric principle is the phenomenon whereby multiple acid/base pairs in solution will be in equilibrium with one another, tied together by their common reagent: the hydrogen ion and hence, the pH of solution. That is, when several buffers are present together in the same solution, they are all exposed to the same hydrogen ion activity. Hence, the pK of each buffer will dictate the ratio of the concentrations of its base and weak acid forms at the given pH, in accordance with the Henderson-Hasselbalch equation. Any condition that changes the balance of one of the buffer systems, also changes the balance of all the others because the buffer systems actually buffer one another by shifting hydrogen ions back and forth from one to the other. The isohydric principle has special relevance to in vivo biochemistry where multiple acid/ base pairs are in solution. The simplifying isohydric principle gives two important concepts. First, all of the buffers in a multiple-buffered system contribute to pH of the system. Secondly, the pH (at equilibrium) can be calculated from an individual buffer system regardless of other buffers present. That is, in vivo, knowing the PCO2 (weak acid) and the bicarbonate (conjugate base) and the pKa of that buffer system, the pH can be calculated regardless of the presence of other contributing buffers | https://en.wikipedia.org/wiki?curid=23868617 |
Isohydric principle The clinical relevance is that arterial blood gas often directly measures the CO2 levels and the pH, but the bicarbonate levels are then calculated from that information—without regard to other buffers present | https://en.wikipedia.org/wiki?curid=23868617 |
Reynolds number The () is an important dimensionless quantity in fluid mechanics used to help predict flow patterns in different fluid flow situations. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow (eddy currents). These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of cavitation. The has wide applications, ranging from liquid flow in a pipe to the passage of air over an aircraft wing. It is used to predict the transition from laminar to turbulent flow, and is used in the scaling of similar but different-sized flow situations, such as between an aircraft model in a wind tunnel and the full size version. The predictions of the onset of turbulence and the ability to calculate scaling effects can be used to help predict fluid behaviour on a larger scale, such as in local or global air or water movement and thereby the associated meteorological and climatological effects. The concept was introduced by George Stokes in 1851, but the was named by Arnold Sommerfeld in 1908 after Osborne Reynolds (1842–1912), who popularized its use in 1883. The is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number A region where these forces change behavior is known as a boundary layer, such as the bounding surface in the interior of a pipe. A similar effect is created by the introduction of a stream of high-velocity fluid into a low-velocity fluid, such as the hot gases emitted from a flame in air. This relative movement generates fluid friction, which is a factor in developing turbulent flow. Counteracting this effect is the viscosity of the fluid, which tends to inhibit turbulence. The quantifies the relative importance of these two types of forces for given flow conditions, and is a guide to when turbulent flow will occur in a particular situation. This ability to predict the onset of turbulent flow is an important design tool for equipment such as piping systems or aircraft wings, but the is also used in scaling of fluid dynamics problems, and is used to determine dynamic similitude between two different cases of fluid flow, such as between a model aircraft, and its full-size version. Such scaling is not linear and the application of Reynolds numbers to both situations allows scaling factors to be developed. With respect to laminar and turbulent flow regimes: The is defined as where: The can be defined for several different situations where a fluid is in relative motion to a surface. These definitions generally include the fluid properties of density and viscosity, plus a velocity and a characteristic length or characteristic dimension (L in the above equation) | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number This dimension is a matter of convention – for example radius and diameter are equally valid to describe spheres or circles, but one is chosen by convention. For aircraft or ships, the length or width can be used. For flow in a pipe, or for a sphere moving in a fluid, the internal diameter is generally used today. Other shapes such as rectangular pipes or non-spherical objects have an "equivalent diameter" defined. For fluids of variable density such as compressible gases or fluids of variable viscosity such as non-Newtonian fluids, special rules apply. The velocity may also be a matter of convention in some circumstances, notably stirred vessels. In practice, matching the is not on its own sufficient to guarantee similitude. Fluid flow is generally chaotic, and very small changes to shape and surface roughness of bounding surfaces can result in very different flows. Nevertheless, Reynolds numbers are a very important guide and are widely used. Osborne Reynolds famously studied the conditions in which the flow of fluid in pipes transitioned from laminar flow to turbulent flow. In his 1883 paper Reynolds described the transition from laminar to turbulent flow in a classic experiment in which he examined the behaviour of water flow under different flow velocities using a small stream of dyed water introduced into the centre of clear water flow in a larger pipe | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number The larger pipe was glass so the behaviour of the layer of the dyed stream could be observed, and at the end of this pipe there was a flow control valve used to vary the water velocity inside the tube. When the velocity was low, the dyed layer remained distinct through the entire length of the large tube. When the velocity was increased, the layer broke up at a given point and diffused throughout the fluid's cross-section. The point at which this happened was the transition point from laminar to turbulent flow. From these experiments came the dimensionless for dynamic similarity—the ratio of inertial forces to viscous forces. Reynolds also proposed what is now known as the Reynolds-averaging of turbulent flows, where quantities such as velocity are expressed as the sum of mean and fluctuating components. Such averaging allows for 'bulk' description of turbulent flow, for example using the Reynolds-averaged Navier–Stokes equations. For flow in a pipe or tube, the is generally defined as where For shapes such as squares, rectangular or annular ducts where the height and width are comparable, the characteristic dimension for internal-flow situations is taken to be the hydraulic diameter, , defined as where is the cross-sectional area, and is the wetted perimeter. The wetted perimeter for a channel is the total perimeter of all channel walls that are in contact with the flow. This means that the length of the channel exposed to air is "not" included in the wetted perimeter | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number For a circular pipe, the hydraulic diameter is exactly equal to the inside pipe diameter: For an annular duct, such as the outer channel in a tube-in-tube heat exchanger, the hydraulic diameter can be shown algebraically to reduce to where For calculation involving flow in non-circular ducts, the hydraulic diameter can be substituted for the diameter of a circular duct, with reasonable accuracy, if the aspect ratio AR of the duct cross-section remains in the range < AR < 4. In boundary layer flow over a flat plate, experiments confirm that, after a certain length of flow, a laminar boundary layer will become unstable and turbulent. This instability occurs across different scales and with different fluids, usually when ≈ , where is the distance from the leading edge of the flat plate, and the flow velocity is the freestream velocity of the fluid outside the boundary layer. For flow in a pipe of diameter , experimental observations show that for "fully developed" flow, laminar flow occurs when < 2300 and turbulent flow occurs when > 2900. At the lower end of this range, a continuous turbulent-flow will form, but only at a very long distance from the inlet of the pipe. The flow in between will begin to transition from laminar to turbulent and then back to laminar at irregular intervals, called intermittent flow. This is due to the different speeds and conditions of the fluid in different areas of the pipe's cross-section, depending on other factors such as pipe roughness and flow uniformity | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number Laminar flow tends to dominate in the fast-moving center of the pipe while slower-moving turbulent flow dominates near the wall. As the increases, the continuous turbulent-flow moves closer to the inlet and the intermittency in between increases, until the flow becomes fully turbulent at > 2900. This result is generalized to non-circular channels using the hydraulic diameter, allowing a transition to be calculated for other shapes of channel. These transition Reynolds numbers are also called "critical Reynolds numbers", and were studied by Osborne Reynolds around 1895. The critical is different for every geometry. For a fluid moving between two plane parallel surfaces—where the width is much greater than the space between the plates—then the characteristic dimension is equal to twice the distance between the plates. This is consistent with the annular duct and rectangular duct cases above taken to a limiting aspect ratio. For flow of liquid with a free surface, the hydraulic radius must be determined. This is the cross-sectional area of the channel divided by the wetted perimeter. For a semi-circular channel, it is quarter the diameter (in case of full pipe flow). For a rectangular channel, the hydraulic radius is the cross-sectional area divided by the wetted perimeter | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number Some texts then use a characteristic dimension that is four times the hydraulic radius, chosen because it gives the same value of Re for the onset of turbulence as in pipe flow, while others use the hydraulic radius as the characteristic length-scale with consequently different values of for transition and turbulent flow. Reynolds numbers are used in airfoil design to (among other things) manage "scale effect" when computing/comparing characteristics (a tiny wing, scaled to be huge, will perform differently). Fluid dynamicists define the chord like this: , where is the flight speed, is the chord length, and is the kinematic viscosity of the fluid in which the airfoil operates, which is for the atmosphere at sea level. In some special studies a characteristic length other than chord may be used; rare is the "span Reynolds number", which is not to be confused with spanwise stations on a wing, where chord is still used. The for an object moving in a fluid, called the particle and often denoted , characterizes the nature of the surrounding flow and its fall velocity. Where the viscosity is naturally high, such as polymer solutions and polymer melts, flow is normally laminar. The is very small and Stokes' law can be used to measure the viscosity of the fluid. Spheres are allowed to fall through the fluid and they reach the terminal velocity quickly, from which the viscosity can be determined | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number The laminar flow of polymer solutions is exploited by animals such as fish and dolphins, who exude viscous solutions from their skin to aid flow over their bodies while swimming. It has been used in yacht racing by owners who want to gain a speed advantage by pumping a polymer solution such as low molecular weight polyoxyethylene in water, over the wetted surface of the hull. It is, however, a problem for mixing of polymers, because turbulence is needed to distribute fine filler (for example) through the material. Inventions such as the "cavity transfer mixer" have been developed to produce multiple folds into a moving melt so as to improve mixing efficiency. The device can be fitted onto extruders to aid mixing. For a sphere in a fluid, the characteristic length-scale is the diameter of the sphere and the characteristic velocity is that of the sphere relative to the fluid some distance away from the sphere, such that the motion of the sphere does not disturb that reference parcel of fluid. The density and viscosity are those belonging to the fluid. Note that purely laminar flow only exists up to = 10 under this definition. Under the condition of low , the relationship between force and speed of motion is given by Stokes' law. The equation for a rectangular object is identical to that of a sphere, with the object being approximated as an ellipsoid and the axis of length being chosen as the characteristic length scale | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number Such considerations are important in natural streams, for example, where there are few perfectly spherical grains. For grains in which measurement of each axis is impractical, sieve diameters are used instead as the characteristic particle length-scale. Both approximations alter the values of the critical Reynolds number. The particle is important in determining the fall velocity of a particle. When the particle indicates laminar flow, Stokes' law can be used to calculate its fall velocity. When the particle indicates turbulent flow, a turbulent drag law must be constructed to model the appropriate settling velocity. For fluid flow through a bed, of approximately spherical particles of diameter in contact, if the "voidage" is and the "superficial velocity" is , the can be defined as or or The choice of equation depends on the system involved: the first is successful in correlating the data for various types of packed and fluidized beds, the second suits for the liquid-phase data, while the third was found successful in correlating the fluidized bed data, being first introduced for liquid fluidized bed system. Laminar conditions apply up to = 10, fully turbulent from = 2000. In a cylindrical vessel stirred by a central rotating paddle, turbine or propeller, the characteristic dimension is the diameter of the agitator . The velocity is where is the rotational speed in rad per second. Then the is: The system is fully turbulent for values of above | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number Pressure drops seen for fully developed flow of fluids through pipes can be predicted using the Moody diagram which plots the Darcy–Weisbach friction factor against and relative roughness . The diagram clearly shows the laminar, transition, and turbulent flow regimes as increases. The nature of pipe flow is strongly dependent on whether the flow is laminar or turbulent. In order for two flows to be similar, they must have the same geometry and equal Reynolds and Euler numbers. When comparing fluid behavior at corresponding points in a model and a full-scale flow, the following holds: where formula_11 is the for the model, and formula_12 is full-scale Reynolds number, and similarly for the Euler numbers. The model numbers and design numbers should be in the same proportion, hence This allows engineers to perform experiments with reduced scale models in water channels or wind tunnels and correlate the data to the actual flows, saving on costs during experimentation and on lab time. Note that true dynamic similitude may require matching other dimensionless numbers as well, such as the Mach number used in compressible flows, or the Froude number that governs open-channel flows. Some flows involve more dimensionless parameters than can be practically satisfied with the available apparatus and fluids, so one is forced to decide which parameters are most important. For experimental flow modeling to be useful, it requires a fair amount of experience and judgment of the engineer | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number An example where the mere is not sufficient for similarity of flows (or even the flow regime – laminar or turbulent) are bounded flows, i.e. flows that are restricted by walls or other boundaries. A classical example of this is the Taylor–Couette flow, where the dimensionless ratio of radii of bounding cylinders is also important, and many technical applications where these distinctions play an important role. Principles of these restrictions were developed by Maurice Marie Alfred Couette and Geoffrey Ingram Taylor and developed further by Floris Takens and David Ruelle. In a turbulent flow, there is a range of scales of the time-varying fluid motion. The size of the largest scales of fluid motion (sometimes called eddies) are set by the overall geometry of the flow. For instance, in an industrial smoke stack, the largest scales of fluid motion are as big as the diameter of the stack itself. The size of the smallest scales is set by the Reynolds number. As the increases, smaller and smaller scales of the flow are visible. In a smoke stack, the smoke may appear to have many very small velocity perturbations or eddies, in addition to large bulky eddies. In this sense, the is an indicator of the range of scales in the flow. The higher the Reynolds number, the greater the range of scales. The largest eddies will always be the same size; the smallest eddies are determined by the Reynolds number | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number What is the explanation for this phenomenon? A large indicates that viscous forces are not important at large scales of the flow. With a strong predominance of inertial forces over viscous forces, the largest scales of fluid motion are undamped—there is not enough viscosity to dissipate their motions. The kinetic energy must "cascade" from these large scales to progressively smaller scales until a level is reached for which the scale is small enough for viscosity to become important (that is, viscous forces become of the order of inertial ones). It is at these small scales where the dissipation of energy by viscous action finally takes place. The indicates at what scale this viscous dissipation occurs. Poiseuille's law on blood circulation in the body is dependent on laminar flow. In turbulent flow the flow rate is proportional to the square root of the pressure gradient, as opposed to its direct proportionality to pressure gradient in laminar flow. Using the definition of the we can see that a large diameter with rapid flow, where the density of the blood is high, tends towards turbulence. Rapid changes in vessel diameter may lead to turbulent flow, for instance when a narrower vessel widens to a larger one. Furthermore, a bulge of atheroma may be the cause of turbulent flow, where audible turbulence may be detected with a stethoscope. interpretation has been extended into the area of arbitrary complex systems. Such as financial flows, nonlinear networks, etc | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number In the latter case an artificial viscosity is reduced to nonlinear mechanism of energy distribution in complex network media. then represents a basic control parameter which expresses a balance between injected and dissipated energy flows for open boundary system. It has been shown that Reynolds critical regime separates two types of phase space motion: accelerator (attractor) and decelerator. High leads to a chaotic regime transition only in frame of strange attractor model. The can be obtained when one uses the nondimensional form of the incompressible Navier–Stokes equations for a newtonian fluid expressed in terms of the Lagrangian derivative: Each term in the above equation has the units of a "body force" (force per unit volume) with the same dimensions of a density times an acceleration. Each term is thus dependent on the exact measurements of a flow. When one renders the equation nondimensional, that is when we multiply it by a factor with inverse units of the base equation, we obtain a form that does not depend directly on the physical sizes. One possible way to obtain a nondimensional equation is to multiply the whole equation by the factor where If we now set we can rewrite the Navier–Stokes equation without dimensions: where the term . Finally, dropping the primes for ease of reading: This is why mathematically all Newtonian, incompressible flows with the same are comparable. Notice also that in the above equation, the viscous terms vanish for | https://en.wikipedia.org/wiki?curid=23868856 |
Reynolds number Thus flows with high Reynolds numbers are approximately inviscid in the free stream. There are many dimensionless numbers in fluid mechanics. The measures the ratio of advection and diffusion effects on structures in the velocity field, and is therefore closely related to Péclet numbers, which measure the ratio of these effects on other fields carried by the flow, for example temperature and magnetic fields. Replacement of the kinematic viscosity in by the thermal or magnetic diffusivity results in respectively the thermal Péclet number and the magnetic Reynolds number. These are therefore related to by products with ratios of diffusivities, namely the Prandtl number and magnetic Prandtl number. | https://en.wikipedia.org/wiki?curid=23868856 |
Negative-index metamaterial or negative-index material (NIM) is a metamaterial whose refractive index for an electromagnetic wave has a negative value over some frequency range. NIMs are constructed of periodic basic parts called unit cells, which are usually significantly smaller than the wavelength of the externally applied electromagnetic radiation. The unit cells of the first experimentally investigated NIMs were constructed from circuit board material, or in other words, wires and dielectrics. In general, these artificially constructed cells are stacked or planar and configured in a particular repeated pattern to compose the individual NIM. For instance, the unit cells of the first NIMs were stacked horizontally and vertically, resulting in a pattern that was repeated and intended (see below images). Specifications for the response of each unit cell are predetermined prior to construction and are based on the intended response of the entire, newly constructed, material. In other words, each cell is individually tuned to respond in a certain way, based on the desired output of the NIM. The aggregate response is mainly determined by each unit cell's "geometry" and substantially differs from the response of its constituent materials. In other words, the way the NIM responds is that of a new material, unlike the wires or metals and dielectrics it is made from. Hence, the NIM has become an effective medium | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Also, in effect, this metamaterial has become an “ordered macroscopic material, synthesized from the bottom up”, and has emergent properties beyond its components. Metamaterials that exhibit a negative value for the refractive index are often referred to by any of several terminologies: left-handed media or left-handed material (LHM), backward-wave media (BW media), media with negative refractive index, double negative (DNG) metamaterials, and other similar names. Electrodynamics of media with negative indices of refraction were first studied by Russian theoretical-physicist Victor Veselago from Moscow Institute of Physics and Technology in 1967. The proposed "left-handed" or "negative-index" materials were theorized to exhibit optical properties opposite to those of glass, air, and other transparent media. Such materials were predicted to exhibit counterintuitive properties like bending or refracting light in unusual and unexpected ways. However, the first practical metamaterial was not constructed until 33 years later and it does produce Veselago's concepts. In 1978, Sergei P. Efimov from Bauman Moscow State Technical University found unexpected effect in theory of the wave refraction. His research is based on fundamental property of Maxwell's equations to overcome restrictions of Fresnel equations. He found parameters of totally non-reflecting crystal i.e. of anisotropic medium. Found property is important for developing concepts of metamaterials | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Currently, negative-index metamaterials are being developed to manipulate electromagnetic radiation in new ways. For example, optical and electromagnetic properties of natural materials are often altered through chemistry. With metamaterials, optical and electromagnetic properties can be engineered by changing the geometry of its unit cells. The unit cells are materials that are ordered in geometric arrangements with dimensions that are fractions of the wavelength of the radiated electromagnetic wave. Each artificial unit responds to the radiation from the source. The collective result is the material's response to the electromagnetic wave that is broader than normal. Subsequently, transmission is altered by adjusting the shape, size, and configurations of the unit cells. This results in control over material parameters known as permittivity and magnetic permeability. These two parameters (or quantities) determine the propagation of electromagnetic waves in matter. Therefore, controlling the values of permittivity and permeability means that the refractive index can be negative or zero as well as conventionally positive. It all depends on the intended application or desired result. So, optical properties can be expanded beyond the capabilities of lenses, mirrors, and other conventional materials. Additionally, one of the effects most studied is the negative index of refraction. When a negative index of refraction occurs, propagation of the electromagnetic wave is reversed | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Resolution below the diffraction limit becomes possible. This is known as subwavelength imaging. Transmitting a beam of light via an electromagnetically flat surface is another capability. In contrast, conventional materials are usually curved, and cannot achieve resolution below the diffraction limit. Also, reversing the electromagnetic waves in a material, in conjunction with other ordinary materials (including air) could result in minimizing losses that would normally occur. The reverse of the electromagnetic wave, characterized by an antiparallel phase velocity is also an indicator of negative index of refraction. Furthermore, negative-index materials are customized composites. In other words, materials are combined with a desired result in mind. Combinations of materials can be designed to achieve optical properties not seen in nature. The properties of the composite material stem from its lattice structure constructed from components smaller than the impinging electromagnetic wavelength separated by distances that are also smaller than the impinging electromagnetic wavelength. Likewise, by fabricating such metamaterials researchers are trying to overcome fundamental limits tied to the wavelength of light. The unusual and counter intuitive properties currently have practical and commercial use manipulating electromagnetic microwaves in wireless and communication systems. Lastly, research continues in the other domains of the electromagnetic spectrum, including visible light | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial The first actual metamaterials worked in the microwave regime, or centimeter wavelengths, of the electromagnetic spectrum (about 4.3 GHz). It was constructed of split-ring resonators and conducting straight wires (as unit cells). The unit cells were sized from 7 to 10 millimeters. The unit cells were arranged in a two-dimensional (periodic) repeating pattern which produces a crystal-like geometry. Both the unit cells and the lattice spacing were smaller than the radiated electromagnetic wave. This produced the first left-handed material when both the permittivity and permeability of the material were negative. This system relies on the resonant behavior of the unit cells. Below a group of researchers develop an idea for a left-handed metamaterial that does not rely on such resonant behavior. Research in the microwave range continues with split-ring resonators and conducting wires. Research also continues in the shorter wavelengths with this configuration of materials and the unit cell sizes are scaled down. However, at around 200 terahertz issues arise which make using the split ring resonator problematic. ""Alternative materials become more suitable for the terahertz and optical regimes"." At these wavelengths selection of materials and size limitations become important. For example, in 2007 a 100 nanometer mesh wire design made of silver and woven in a repeating pattern transmitted beams at the 780 nanometer wavelength, the far end of the visible spectrum | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial The researchers believe this produced a negative refraction of 0.6. Nevertheless, this operates at only a single wavelength like its predecessor metamaterials in the microwave regime. Hence, the challenges are to fabricate metamaterials so that they "refract light at ever-smaller wavelengths" and to develop broad band capabilities. In the metamaterial literature, medium or media refers to transmission medium or optical medium. In 2002, a group of researchers came up with the idea that in contrast to materials that depended on resonant behavior, non-resonant phenomena could surpass narrow bandwidth constraints of the wire/split-ring resonator configuration. This idea translated into a type of medium with broader bandwidth abilities, negative refraction, backward waves, and focusing beyond the diffraction limit. They dispensed with split-ring-resonators and instead used a network of L–C loaded transmission lines. metamaterial literature this became known as artificial transmission-line media. At that time it had the added advantage of being more compact than a unit made of wires and split ring resonators. The network was both scalable (from the megahertz to the tens of gigahertz range) and tunable. It also includes a method for focusing the wavelengths of interest. By 2007 the negative refractive index transmission line was employed as a subwavelength focusing free-space flat lens. That this is a free-space lens is a significant advance | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Part of prior research efforts targeted creating a lens that did not need to be embedded in a transmission line. Metamaterial components shrink as research explores shorter wavelengths (higher frequencies) of the electromagnetic spectrum in the infrared and visible spectrums. For example, theory and experiment have investigated smaller horseshoe shaped split ring resonators designed with lithographic techniques, as well as paired metal nanorods or nanostrips, and nanoparticles as circuits designed with lumped element models The science of negative-index materials is being matched with conventional devices that broadcast, transmit, shape, or receive electromagnetic signals that travel over cables, wires, or air. The materials, devices and systems that are involved with this work could have their properties altered or heightened. Hence, this is already happening with metamaterial antennas and related devices which are commercially available. Moreover, in the wireless domain these metamaterial apparatuses continue to be researched. Other applications are also being researched. These are electromagnetic absorbers such as radar-microwave absorbers, electrically small resonators, waveguides that can go beyond the diffraction limit, phase compensators, advancements in focusing devices (e.g. microwave lens), and improved electrically small antennas. In the optical frequency regime developing the superlens may allow for imaging below the diffraction limit | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Other potential applications for negative-index metamaterials are optical nanolithography, nanotechnology circuitry, as well as a near field superlens (Pendry, 2000) that could be useful for biomedical imaging and subwavelength photolithography. To describe any electromagnetic properties of a given material such as an optical lens, there are two significant parameters. These are permittivity, ε, and permeability, μ, which could allow for accurate prediction of light waves traveling within materials, and electromagnetic phenomena that occur at the surface between two materials (interface). For example, refractive index is an electromagnetic phenomenon which occurs at the surface (or interface) between two materials. Snell's law states that the relationship between the radiated angle of incidence, and the resulting refracted angle of transmission, rests on the refractive index, "n", of the two media (materials). Mathematics provides a visualization with formula_1. Hence, it can be seen that the behavior of the refractive index is dependent on the association of these two parameters, as well as their quantitative values. Therefore, if designed or arbitrarily modified values can be inputs for "ε" and "μ", then the behavior of propagating electromagnetic waves inside the material can be manipulated at will. This ability then allows for intentional determination of the refractive index | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial For example, in 1967, Victor Veselago analytically determined that light will refract in the reverse direction (negatively) at the interface between a material with negative refractive index and a material exhibiting conventional refractive index. This extraordinary material was realized on paper with simultaneous negative values for "ε", and, "μ", and could therefore be termed a double negative material. However, in Veselago's day a material which exhibits double negative parameters simultaneously seemed impossible because no natural materials exist which can produce this effect. Therefore, his work was ignored for three decades.. It was nominated for the Nobel Prize later. In 1987, Sergei P. Efimov used fundamental property of Maxwell's equations to overcome restrictions of Fresnel formulas. He changed scale of Z-axis: Z'=Z/K, i.e. empty medium with ε=1 is compressed along Z. Therefore, Maxwell's equations go to equations for macroscopic anisotropic medium with tensors ε and μ. Permittivity ε along axis Z is equal to K when transverse ε is equal to 1/K. Permeability μ is equal to K and transverse that μ is equal to 1/K. Wave in empty space goes to refracted wave. Consequently, found crystal has no reflection at any angle and for any frequency. Straight calculation gives the reflection coefficient to be equal to zero what is similar to "quantum effect". It is very important that parameter K can be "negative" and "complex" even as far as the origin of effect is the "compression" property only. Sergei P | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Efimov applied analogous transformation for the acoustic wave equations. Three conceptions- negative-index medium, non-reflective crystal and super-lense are foundations of the metamaterial theory. In general the physical properties of natural materials cause limitations. Most dielectrics only have positive permittivities, ε > 0 . Metals will exhibit negative permittivity, ε < 0 at optical frequencies, and plasmas exhibit negative permittivity values in certain frequency bands. Pendry et al. demonstrated that the plasma frequency can be made to occur in the lower microwave frequencies for metals with a material made of metal rods that replaces the bulk metal. However, in each of these cases permeability remains always positive. At microwave frequencies it is possible for negative μ to occur in some ferromagnetic materials. But the inherent drawback is they are difficult to find above terahertz frequencies. In any case, a natural material that can achieve negative values for permittivity and permeability simultaneously has not been found or discovered. Hence, all of this has led to constructing artificial composite materials known as metamaterials in order to achieve the desired results. Theoretical articles were published in 1996 and 1999 which showed that synthetic materials could be constructed to purposely exhibit a negative permittivity and permeability | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial These papers, along with Veselago's 1967 theoretical analysis of the properties of negative-index materials, provided the background to fabricate a metamaterial with negative effective permittivity and permeability. See below. A metamaterial developed to exhibit negative-index behavior is typically formed from individual components. Each component responds differently and independently to a radiated electromagnetic wave as it travels through the material. Since these components are smaller than the radiated wavelength it is understood that a macroscopic view includes an effective value for both permittivity and permeability. In the year 2000, David R. Smith's team of UCSD researchers produced a new class of composite materials by depositing a structure onto a circuit-board substrate consisting of a series of thin copper split-rings and ordinary wire segments strung parallel to the rings. This material exhibited unusual physical properties that had never been observed in nature. These materials obey the laws of physics, but behave differently from normal materials. In essence these "negative-index metamaterials" were noted for having the ability to reverse many of the physical properties that govern the behavior of ordinary optical materials. One of those unusual properties is the ability to reverse, for the first time, Snell's law of refraction. Until the demonstration of negative refractive index for microwaves by the UCSD team, the material had been unavailable | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Advances during the 1990s in fabrication and computation abilities allowed these first metamaterials to be constructed. Thus, the "new" metamaterial was tested for the effects described by Victor Veselago 30 years earlier. Studies of this experiment, which followed shortly thereafter, announced that other effects had occurred. With antiferromagnets and certain types of insulating ferromagnets, effective negative magnetic permeability is achievable when polariton resonance exists. To achieve a negative index of refraction, however, permittivity with negative values must occur within the same frequency range. The artificially fabricated split-ring resonator is a design that accomplishes this, along with the promise of dampening high losses. With this first introduction of the metamaterial, it appears that the losses incurred were smaller than antiferromagnetic, or ferromagnetic materials. When first demonstrated in 2000, the composite material (NIM) was limited to transmitting microwave radiation at frequencies of 4 to 7 gigahertz (4.28–7.49 cm wavelengths). This range is between the frequency of household microwave ovens (~2.45 GHz, 12.23 cm) and military radars (~10 GHz, 3 cm). At demonstrated frequencies, pulses of electromagnetic radiation moving through the material in one direction are composed of constituent waves moving in the opposite direction. The metamaterial was constructed as a periodic array of copper split ring and wire conducting elements deposited onto a circuit-board substrate | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial The design was such that the cells, and the lattice spacing between the cells, were much smaller than the radiated electromagnetic wavelength. Hence, it behaves as an effective medium. The material has become notable because its range of (effective) permittivity ε and permeability μ values have exceeded those found in any ordinary material. Furthermore, the characteristic of negative (effective) permeability evinced by this medium is particularly notable, because it has "not" been found in ordinary materials. In addition, the negative values for the magnetic component is directly related to its left-handed nomenclature, and properties (discussed in a section below). The split-ring resonator (SRR), based on the prior 1999 theoretical article, is the tool employed to achieve negative permeability. This first composite "metamaterial" is then composed of split-ring resonators and electrical conducting posts. Initially, these materials were only demonstrated at wavelengths longer than those in the visible spectrum. In addition, early NIMs were fabricated from opaque materials and usually made of non-magnetic constituents. As an illustration, however, if these materials are constructed at visible frequencies, and a flashlight is shone onto the resulting NIM slab, the material should focus the light at a point on the other side. This is not possible with a sheet of ordinary opaque material. In 2007, the NIST in collaboration with the Atwater Lab at Caltech created the first NIM active at optical frequencies | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial More recently (), layered "fishnet" NIM materials made of silicon and silver wires have been integrated into optical fibers to create active optical elements. Negative permittivity ε < 0 had already been discovered and realized in metals for frequencies all the way up to the plasma frequency, before the first metamaterial. There are two requirements to achieve a negative value for refraction. First, is to fabricate a material which can produce negative permeability μ < 0. Second, negative values for both permittivity and permeability must occur simultaneously over a common range of frequencies. Therefore, for the first metamaterial, the nuts and bolts are one split-ring resonator electromagnetically combined with one (electric) conducting post. These are designed to resonate at designated frequencies to achieve the desired values. Looking at the make-up of the split ring, the associated magnetic field pattern from the SRR is dipolar. This dipolar behavior is notable because this means it mimics nature's atom, but on a much larger scale, such as in this case at 2.5 millimeters. Atoms exist on the scale of picometers. The splits in the rings create a dynamic where the SRR unit cell can be made resonant at radiated wavelengths "much larger" than the diameter of the rings. If the rings were closed, a half wavelength boundary would be electromagnetically imposed as a requirement for resonance. The split in the second ring is oriented opposite to the split in the first ring | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial It is there to generate a large capacitance, which occurs in the small gap. This capacitance substantially decreases the resonant frequency while concentrating the electric field. The individual SRR depicted on the right had a resonant frequency of 4.845 GHz, and the resonance curve, inset in the graph, is also shown. The radiative losses from absorption and reflection are noted to be small, because the unit dimensions are much smaller than the free space, radiated wavelength. When these units or cells are combined into a periodic arrangement, the magnetic coupling between the resonators is strengthened, and a "strong magnetic coupling occurs". Properties unique in comparison to ordinary or conventional materials begin to emerge. For one thing, this periodic strong coupling creates a material, which now has an effective magnetic permeability μ in response to the radiated-incident magnetic field. Graphing the general dispersion curve, a region of propagation occurs from zero up to a lower band edge, followed by a gap, and then an upper passband. The presence of a 400 MHz gap between 4.2 GHz and 4.6 GHz implies a band of frequencies where μ < 0 occurs. Furthermore, when wires are added symmetrically between the split rings, a passband occurs within the previously forbidden band of the split ring dispersion curves | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial That this passband occurs within a previously forbidden region indicates that the negative ε for this region has combined with the negative μ to allow propagation, which fits with theoretical predictions. Mathematically, the dispersion relation leads to a band with negative group velocity everywhere, and a bandwidth that is independent of the plasma frequency, within the stated conditions. Mathematical modeling and experiment have both shown that periodically arrayed conducting elements (non-magnetic by nature) respond predominantly to the magnetic component of incident electromagnetic fields. The result is an effective medium and negative μ over a band of frequencies. The permeability was verified to be the region of the forbidden band, where the gap in propagation occurred – from a finite section of material. This was combined with a negative permittivity material, ε < 0, to form a “left-handed” medium, which formed a propagation band with negative group velocity where previously there was only attenuation. This validated predictions. In addition, a later work determined that this first metamaterial had a range of frequencies over which the refractive index was predicted to be negative for one direction of propagation (see ref #). Other predicted electrodynamic effects were to be investigated in other research. From the conclusions in the above section a left-handed material (LHM) can be defined | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial It is a material which exhibits simultaneous negative values for permittivity, ε, and permeability, μ, in an overlapping frequency region. Since the values are derived from the effects of the composite medium system as a whole, these are defined as effective permittivity, ε, and effective permeability, μ. Real values are then derived to denote the value of negative index of refraction, and wave vectors. This means that in practice losses will occur for a given medium used to transmit electromagnetic radiation such as microwave, or infrared frequencies, or visible light – for example. In this instance, real values describe either the amplitude or the intensity of a transmitted wave relative to an incident wave, while ignoring the negligible loss values. In the above sections first fabricated metamaterial was constructed with resonating elements, which exhibited one direction of incidence and polarization. In other words, this structure exhibited left-handed propagation in one dimension. This was discussed in relation to Veselago's seminal work 33 years earlier (1967). He predicted that intrinsic to a material, which manifests negative values of effective permittivity and permeability, are several types of reversed physics phenomena. Hence, there was then a critical need for a higher-dimensional LHMs to confirm Veselago's theory, as expected. The confirmation would include reversal of Snell's law (index of refraction), along with other reversed phenomena | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial In the beginning of 2001 the existence of a higher-dimensional structure was reported. It was two-dimensional and demonstrated by both experiment and numerical confirmation. It was an LHM, a composite constructed of wire strips mounted behind the split-ring resonators (SRRs) in a periodic configuration. It was created for the express purpose of being suitable for further experiments to produce the effects predicted by Veselago. A theoretical work published in 1967 by Soviet physicist Victor Veselago showed that a refractive index with negative values is possible and that this does not violate the laws of physics. As discussed previously (above), the first metamaterial had a range of frequencies over which the refractive index was predicted to be negative for one direction of propagation. It was reported in May 2000. In 2001, a team of researchers constructed a prism composed of metamaterials (negative-index metamaterials) to experimentally test for negative refractive index. The experiment used a waveguide to help transmit the proper frequency and isolate the material. This test achieved its goal because it successfully verified a negative index of refraction. The experimental demonstration of negative refractive index was followed by another demonstration, in 2003, of a reversal of Snell's law, or reversed refraction. However, in this experiment negative index of refraction material is in free space from 12.6 to 13.2 GHz | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial Although the radiated frequency range is about the same, a notable distinction is this experiment is conducted in free space rather than employing waveguides. Furthering the authenticity of negative refraction, the power flow of a wave transmitted through a dispersive left-handed material was calculated and compared to a dispersive right-handed material. The transmission of an incident field, composed of many frequencies, from an isotropic nondispersive material into an isotropic dispersive media is employed. The direction of power flow for both nondispersive and dispersive media is determined by the time-averaged Poynting vector. Negative refraction was shown to be possible for multiple frequency signals by explicit calculation of the Poynting vector in the LHM. In a slab of conventional material with an ordinary refractive index – a right-handed material (RHM) – the wave front is transmitted away from the source. In a NIM the wavefront travels toward the source. However, the magnitude and direction of the flow of energy essentially remains the same in both the ordinary material and the NIM. Since the flow of energy remains the same in both materials (media), the impedance of the NIM matches the RHM. Hence, the sign of the intrinsic impedance is still positive in a NIM. Light incident on a left-handed material, or NIM, will bend to the same side as the incident beam, and for Snell's law to hold, the refraction angle should be negative | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial In a passive metamaterial medium this determines a negative real and imaginary part of the refractive index. In 1968 Victor Veselago's paper showed that the opposite directions of EM plane waves and the flow of energy was derived from the individual Maxwell curl equations. In ordinary optical materials, the curl equation for the electric field show a "right hand rule" for the directions of the electric field E, the magnetic induction B, and wave propagation, which goes in the direction of wave vector k. However, the direction of energy flow formed by E × H is right-handed only when "permeability is greater than zero". This means that when permeability is less than zero, e.g. "negative", wave propagation is reversed (determined by k), and contrary to the direction of energy flow. Furthermore, the relations of vectors E, H, and k form a ""left-handed" system" – and it was Veselago who coined the term "left-handed" (LH) material, which is in wide use today (2011). He contended that an LH material has a negative refractive index and relied on the steady-state solutions of Maxwell's equations as a center for his argument. After a 30-year void, when LH materials were finally demonstrated, it could be said that the designation of negative refractive index is unique to LH systems; even when compared to photonic crystals. Photonic crystals, like many other known systems, can exhibit unusual propagation behavior such as reversal of phase and group velocities | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial But, negative refraction does not occur in these systems, and not yet realistically in photonic crystals. The negative refractive index in the optical range was first demnstrated in 2005 by Shalaev et al. (at the telecom wavelength λ = 1.5 μm) and by Brueck et al. (at λ = 2 μm) at nearly the same time. , several anomalous studies have announced negative refraction at single frequencies in the visible spectrum, but the results of some of these demonstrations are considered ambiguous by later studies. Besides reversed values for index of refraction, Veselago predicted the occurrence of reversed Cherenkov radiation (also known simply as CR) in a left-handed medium. In 1934 Pavel Cherenkov discovered a coherent radiation that occurs when certain types of media are bombarded by fast moving electron beams. In 1937 a theory built around CR stated that when charged particles, such as electrons, travel through a medium at speeds faster than the speed of light in the medium only then will CR radiate. As the CR occurs, electromagnetic radiation is emitted in a cone shape, fanning out in the forward direction. CR and the 1937 theory has led to a large array of applications in high energy physics. A notable application are the Cherenkov counters. These are used to determine various properties of a charged particle such as its velocity, charge, direction of motion, and energy. These properties are important in the identification of different particles | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial For example, the counters were applied in the discovery of the antiproton and the J/ψ meson. Six large Cherenkov counters were used in the discovery of the J/ψ meson. It has been difficult to experimentally prove the reversed Cherenkov radiation. Theoretical work, along with numerical simulations, began in the early 2000s on the abilities of DNG slabs for subwavelength focusing. The research began with Pendry's proposed "Perfect lens." Several research investigations that followed Pendry's concluded that the "Perfect lens" was possible in theory but impractical. One direction in subwavelength focusing proceeded with the use of negative-index metamaterials, but based on the enhancements for imaging with surface plasmons. In another direction researchers explored paraxial approximations of NIM slabs. The existence of negative refractive materials can result in a change in electrodynamic calculations for the case of "permeability μ" = 1 . A change from a conventional refractive index to a negative value gives incorrect results for conventional calculations, because some properties and effects have been altered. When "permeability μ" has values other than 1 this affects Snell's law, the Doppler effect, the Cherenkov radiation, Fresnel's equations, and Fermat's principle. The refractive index is basic to the science of optics. Shifting the refractive index to a negative value may be a cause to revisit or reconsider the interpretation of some norms, or basic laws | https://en.wikipedia.org/wiki?curid=23870096 |
Negative-index metamaterial The first US patent granted for a fabricated metamaterial is , titled "Left handed composite media." The listed inventors are David R. Smith, Sheldon Schultz, Norman Kroll, Richard A. Shelby. The invention achieves simultaneous negative permittivity and permeability over a common band of frequencies. The material can integrate media which is already composite or continuous, but which will produce negative permittivity and permeability within the same spectrum of frequencies. Different types of continuous or composite may be deemed appropriate when combined for the desired effect. However, the inclusion of a periodic array of conducting elements is preferred. The array scatters electromagnetic radiation at wavelengths longer than the size of the element and lattice spacing. The array is then viewed as an effective medium. Propagation of a Gaussian Light Pulse through an Anomalous Dispersion Medium. However the speed of transmitting information is always limited to "c". -NIST | https://en.wikipedia.org/wiki?curid=23870096 |
C15H13NO4 The molecular formula CHNO may refer to: | https://en.wikipedia.org/wiki?curid=23876318 |
C6H12S2 The molecular formula CHS (molar mass: 148.28 g/mol) may refer to: | https://en.wikipedia.org/wiki?curid=23876659 |
C14H11N The molecular formula CHN may refer to: | https://en.wikipedia.org/wiki?curid=23876878 |
Formulation is a term used in various senses in various applications, both the material and the abstract or formal. Its fundamental meaning is the putting together of components in appropriate relationships or structures, according to a formula. Etymologically "formula" is the diminutive of the Latin "forma", meaning shape. In that sense a "formulation" is created according to the standard for the product. Disciplines in which one might use the word "formulation" in the abstract sense include logic, mathematics, linguistics, legal theory, and computer science. For details, see the related articles. In more material senses the concept of "formulation" appears in the physical sciences, such as physics, chemistry, and biology. It also is ubiquitous in industry, engineering and medicine, especially pharmaceutics. In pharmacy, a formulation is a mixture or a structure such as a capsule, tablet, or an emulsion, prepared according to a specific procedure (called a “formula”). Formulations are a very important aspect of creating medicines, since they are essential to ensuring that the active part of the drug is delivered to the correct part of the body, in the right concentration, and at the right rate (not too fast and not too slowly). A good example is a drug delivery system that exploits supersaturation | https://en.wikipedia.org/wiki?curid=23876971 |
Formulation They also need to have an acceptable taste (in the case of pills, tablets or syrups), last long enough in storage still to be safe and effective when used, and be sufficiently stable both physically and chemically to be transported from where they are manufactured to the eventual consumer. Competently designed formulations for particular applications are safer, more effective, and more economical than any of their components used singly. Formulations are commercially produced for drugs, cosmetics, coatings, dyes, alloys, cleaning agents, foods, lubricants, fuels, fertilisers, pesticides and many others. Components (also called ingredients), when mixed according to a formula, create a formulation. Some components impart specific properties to the formulation when it is put into use. For example, certain components (polymers) are used in paint formulations to achieve deforming or levelling properties. Some components of a formulation may only be active in particular applications. A formulation may be created for any of the following purposes: | https://en.wikipedia.org/wiki?curid=23876971 |
Azo violet (4-(4-nitrophenylazo)resorcinol) (or p-nitrobenzeneazoresorcinol) is an azo compound with the chemical formula CHNO. It is used commercially as a violet dye and experimentally as a pH indicator, appearing yellow below pH 11, and violet above pH 13. It also turns deep blue in the presence of magnesium salt in a slightly alkaline, or basic, environment. may also be used to test for the presence of ammonium ions. The color of ammonium chloride or ammonium hydroxide solution will vary depending upon the concentration of azo violet used. The intense color from which the compound gets its name results from irradiation and subsequent excitation and relaxation of the extended π electron system across the R-N=N-R’ linked phenols. Absorption of these electrons falls in the visible region of the electromagnetic spectrum. Azo violet's intense indigo color (λ 432 nm) approximates Pantone R: 102 G: 15 B: 240. can be synthesised by reacting 4-nitroaniline with nitrous acid (generated "in situ" with an acid and a nitrite salt) to produce a diazonium intermediate. This is then reacted with resorcinol, dissolved in a sodium hydroxide solution, via an azo coupling reaction. This is consistent with the generalized strategy for preparing azo dyes. The chemical character of azo violet may be attributed to its azo group (-N=N-), six-membered rings, and hydroxyl side groups. Due to steric repulsions, azo violet is most stable in the "trans"-configuration, but isomerization of azo dyes by irradiation is not uncommon | https://en.wikipedia.org/wiki?curid=23877002 |
Azo violet The "para"-position tautomerization of azo violet provides mechanical insight into the behavior of the compound in an acidic environment, and thus its use as a basic pH indicator. The predicted H-NMR of pure azo violet shows the hydroxyl protons as the most deshielded and acidic protons. The participation of these hydroxyl groups' electron-donation to the conjugated π system likewise influences azo violet's λ and p"K" value. | https://en.wikipedia.org/wiki?curid=23877002 |
List of chemistry societies The following is a list of chemistry societies: I* | https://en.wikipedia.org/wiki?curid=23877045 |
C20H24O4 The molecular formula CHO may refer to: | https://en.wikipedia.org/wiki?curid=23878134 |
C17H19NO3 The molecular formula CHNO may refer to: | https://en.wikipedia.org/wiki?curid=23878138 |
C11H22O2 The molecular formula CHO may refer to: | https://en.wikipedia.org/wiki?curid=23878151 |
Benzofluoranthene can refer to: | https://en.wikipedia.org/wiki?curid=23879397 |
C4H7ClO The molecular formula CHClO may refer to: | https://en.wikipedia.org/wiki?curid=23879713 |
Adenosinergic means "working on adenosine". An adenosinergic agent (or drug) is a chemical which functions to directly modulate the adenosine system in the body or brain. Examples include adenosine receptor agonists, adenosine receptor antagonists (such as caffeine), and adenosine reuptake inhibitors. | https://en.wikipedia.org/wiki?curid=23882970 |
Methylenedioxyphenylpropene (CHO) can refer to either: | https://en.wikipedia.org/wiki?curid=23883083 |
Methylenedioxyphenylpropanone (CHO) can refer to: | https://en.wikipedia.org/wiki?curid=23883195 |
Glycinergic A glycinergic agent (or drug) is a chemical which functions to directly modulate the glycine system in the body or brain. Examples include glycine receptor agonists, glycine receptor antagonists, and glycine reuptake inhibitors. | https://en.wikipedia.org/wiki?curid=23884776 |
C17H34O2 The molecular formula CHO may refer to: | https://en.wikipedia.org/wiki?curid=23886739 |
C7H17N The molecular formula CHN may refer to: | https://en.wikipedia.org/wiki?curid=23887124 |
C12H24O11 The molecular formula CHO (molar mass : 344.31 g/mol) may refer to: | https://en.wikipedia.org/wiki?curid=23887490 |
C12H22O10 The chemical formula CHO (molar mass : 326.29 g/mol, exact mass: 326.121297) may refer to: | https://en.wikipedia.org/wiki?curid=23887506 |
C7H7ClO The molecular formula CHClO (molar mass: 142.58 g/mol) may refer to: | https://en.wikipedia.org/wiki?curid=23887562 |
C19H18ClN3O The molecular formula CHClNO (molar mass: 339.819 g/mol) may refer to: | https://en.wikipedia.org/wiki?curid=23887822 |
C10H20 The molecular formula CH may refer to: | https://en.wikipedia.org/wiki?curid=23887860 |
Hermann Leuchs Friedrich (8 August 1879 – 2 May 1945) was a German chemist. Leuchs studied chemistry at the University of Munich from 1898. He transferred to the University of Berlin and received his Ph.D. there in 1902 under Emil Fischer. He steadily advanced in the hierarchy of the university, becoming a lecturer in 1910, assistant professor in 1914, and full professor in 1916. The ministry of education assured him that he would succeed Wilhelm Schlenk as head of the chemistry institute of the University of Berlin, but this never happened. His personality became strongly misanthropic. The Nazi regime, World War II and the destruction of Berlin increased his psychological problems, and shortly before the war ended he committed suicide in his flat in Berlin. This happened most likely on 2 May 1945. He was buried in a mass grave with numerous soldiers and citizens. Leuchs's research dealt with the chemistry of amino acids and the chemistry of strychnine. The Leuchs reaction and the Leuchs anhydride were named after him. | https://en.wikipedia.org/wiki?curid=23889593 |
Sulfolipid Sulfolipids are a class of lipids which possess a sulfur-containing functional group. An abundant sulfolipid is sulfoquinovosyl diacylglycerol, which is composed of a glycoside of sulfoquinovose and diacylglycerol. In plants, sulfoquinovosyl diacylglycerides (SQDG) are important members of the sulfur cycle. Other important sulfolipids include sulfatide and seminolipid, each of which are sulfated glycolipids. | https://en.wikipedia.org/wiki?curid=23889683 |
Ethynyl In organic chemistry, the term ethynyl designates | https://en.wikipedia.org/wiki?curid=23890912 |
Thiokol (polymer) Thiokol is a trade mark for various organic polysulfide polymers, Thiokol polymers are used as an elastomer in seals and sealants. The distinction between the polymers first commercialized by the Thiokol Corporation and subsequent polysulfide materials is often unclear. A variety of thiokols are recognized. Typically they are prepared by the combination of 2-chloroethanol, formaldehyde, and sodium polysulfide (NaS). The chloroethanol is produced in situ from ethylene oxide and hydrogen chloride. The rank x of the polysulfide is an important variable. Crosslinking agents are used, such as 1,2,3-trichloropropane. An idealized polymer is represented by this formula HS(CHCHOCHOCHCHSS)CHCHOCHOCHCHSH. Thiol-terminated resins can be cured oxidatively. In 1838, Swiss chemists reported the preparation of hydrophobilic rubbery materials by the alkylation of sodium polysulfide with 1,2-dichloroethane. In 1926 chemists Joseph C. Patrick and Nathan Mnookin further developed this class of materials, which first achieved commercial success as sealants for fuel lines, exploiting the solvent resistance of these materials. The first production plant was started in 1948 in Elkton, Maryland. The company Thiokol was founded in 1929 to produce these polymers. In the 1940s, thiol-terminated liquid resins were produced. Curing could be effected oxidatively, e.g. using lead oxides and later perborates. Thiokol polymers were used as a binder in solid rocket fuel, a commercial success | https://en.wikipedia.org/wiki?curid=41286524 |
Thiokol (polymer) The name "Thiokol" derives from the Greek words for sulfur and glue. | https://en.wikipedia.org/wiki?curid=41286524 |
C16H13N3O3 The molecular formula CHNO may refer to: | https://en.wikipedia.org/wiki?curid=41295500 |
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