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Cryoelectronics In electronics, cryoelectronics or cryolectronics is the study of superconductivity under cryogenic conditions and its applications. It is also described as the operation of power electronic devices at cryogenic temperatures. Practical applications of this field is quite broad, although it is particular... | https://en.wikipedia.org/wiki?curid=233631 |
Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory technique combining reverse transcription of RNA into DNA (in this context called complementary DNA or cDNA) and amplification of specific DNA targets using polymerase chain reaction (PCR). It is primarily used to measure the amount of a specific ... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction Since its introduction in 1977, Northern blot has been used extensively for RNA quantification despite its shortcomings: (a) time-consuming technique, (b) requires a large quantity of RNA for detection, and (c) quantitatively inaccurate in the low abundance of RNA content... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction The use of RT-PCR for the detection of RNA transcript has revolutionalized the study of gene expression in the following important ways: The quantification of mRNA using RT-PCR can be achieved as either a one-step or a two-step reaction. The difference between the two app... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction It is also the preferred method of analysis when using DNA binding dyes such as SYBR Green since the elimination of primer-dimers can be achieved through a simple change in the melting temperature. Nevertheless, the one-step approach is a relatively convenient solution fo... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction Currently, there are four different fluorescent DNA probes available for the real-time RT-PCR detection of PCR products: SYBR Green, TaqMan, molecular beacons, and scorpion probes. All of these probes allow the detection of PCR products by generating a fluorescent signal.... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction To confirm this, gene expression levels of yeast cells containing this mutation were analyzed using qRT-PCR. The researchers were able to conclusively determine that the mutation of this regulatory protein reduced Gal expression. Northern blot analysis is used to study th... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction Circulating tumor cells produce unique mRNA transcripts depending on the type of cancer. The goal is to determine which mRNA transcripts serve as the best biomarkers for a particular cancer cell type and then analyze its expression levels with RT-PCR. RT-PCR is commonly u... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction One-step RT-PCR take mRNA targets (up to 6 kb) and subjects them to reverse transcription and then PCR amplification in a single test tube. Use only intact, high quality RNA for the best results. Be sure to use a sequence-specific primer. Two-step RT-PCR, as the name impl... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction The MIQE guidelines describe the minimum information necessary for evaluating quantitative PCR experiments that should be required for publication for encouraging better experimental practice and ensuring the relevance, accuracy, correct interpretation, and repeatability ... | https://en.wikipedia.org/wiki?curid=235077 |
Reverse transcription polymerase chain reaction Those labelled E are considered critical and indispensable while those labelled D are considered peripheral yet important for best-practices. | https://en.wikipedia.org/wiki?curid=235077 |
Trace element A trace element is a chemical element whose concentration (or other measure of amount) is very low (a "trace amount"). The exact definition depends on the field of science: | https://en.wikipedia.org/wiki?curid=235175 |
Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. is a free radical, i.e., it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula (·N=O or ·NO). is also a heteronuclear diatomic molecule, a historic c... | https://en.wikipedia.org/wiki?curid=235287 |
Nitric oxide The reaction is thought to proceed via the following stoichiometry: reacts with fluorine, chlorine, and bromine to form the nitrosyl halides, such as nitrosyl chloride: With NO, also a radical, NO combines to form the intensely blue dinitrogen trioxide: The addition of a nitric oxide moiety to another mole... | https://en.wikipedia.org/wiki?curid=235287 |
Nitric oxide In commercial settings, nitric oxide is produced by the oxidation of ammonia at 750–900 °C (normally at 850 °C) with platinum as catalyst: The uncatalyzed endothermic reaction of oxygen (O) and nitrogen (N), which is effected at high temperature (>2000 °C) by lightning has not been developed into a practic... | https://en.wikipedia.org/wiki?curid=235287 |
Nitric oxide One of the few practical methods is spin trapping of nitric oxide with iron-dithiocarbamate complexes and subsequent detection of the mono-nitrosyl-iron complex with electron paramagnetic resonance (EPR). A group of fluorescent dye indicators that are also available in acetylated form for intracellular mea... | https://en.wikipedia.org/wiki?curid=235287 |
Nitric oxide Nitric oxide, known as an endothelium-derived relaxing factor (EDRF), is biosynthesized endogenously from -arginine, oxygen, and NADPH by various nitric oxide synthase (NOS) enzymes. Reduction of inorganic nitrate may also serve to make nitric oxide. One of the main enzymatic targets of nitric oxide is gua... | https://en.wikipedia.org/wiki?curid=235287 |
Nitric oxide , the Occupational Safety and Health Administration (OSHA) has set the legal limit (permissible exposure limit) for nitric oxide exposure in the workplace as 25 ppm (30 mg/m) over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL)... | https://en.wikipedia.org/wiki?curid=235287 |
Potassium hydroxide is an inorganic compound with the formula KOH, and is commonly called caustic potash. Along with sodium hydroxide (NaOH), this colorless solid is a prototypical strong base. It has many industrial and niche applications, most of which exploit its caustic nature and its reactivity toward acids. An es... | https://en.wikipedia.org/wiki?curid=235343 |
Potassium hydroxide Like NaOH, KOH exhibits high thermal stability. The gaseous species is dimeric. Because of its high stability and relatively low melting point, it is often melt-cast as pellets or rods, forms that have low surface area and convenient handling properties. About 121 g of KOH dissolve in 100 mL water a... | https://en.wikipedia.org/wiki?curid=235343 |
Potassium hydroxide KOH reacts with carbon dioxide to give bicarbonate: Historically, KOH was made by adding potassium carbonate to a strong solution of calcium hydroxide (slaked lime) The salt metathesis reaction results in precipitation of solid calcium carbonate, leaving potassium hydroxide in solution: Filtering of... | https://en.wikipedia.org/wiki?curid=235343 |
Potassium hydroxide The saponification of fats with KOH is used to prepare the corresponding "potassium soaps", which are softer than the more common sodium hydroxide-derived soaps. Because of their softness and greater solubility, potassium soaps require less water to liquefy, and can thus contain more cleaning agent ... | https://en.wikipedia.org/wiki?curid=235343 |
Potassium hydroxide Entomologists wishing to study the fine structure of insect anatomy may use a 10% aqueous solution of KOH to apply this process. In chemical synthesis, the choice between the use of KOH and the use of NaOH is guided by the solubility or keeping quality of the resulting salt. The corrosive properties... | https://en.wikipedia.org/wiki?curid=235343 |
Potassium hydroxide Certain species of gilled mushrooms, boletes, polypores, and lichens are identifiable based on this color-change reaction. and its solutions are severe irritants to skin and other tissue. | https://en.wikipedia.org/wiki?curid=235343 |
Hydrogenation – meaning, to treat with hydrogen – is a chemical reaction between molecular hydrogen (H) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds. typically constitutes the additi... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation The hydrogenation process often uses greater than 1 atmosphere of H, usually conveyed from the cylinders and sometimes augmented by "booster pumps". Gaseous hydrogen is produced industrially from hydrocarbons by the process known as steam reforming. For many applications, hydrogen is transferred from dono... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation The trade-off is activity (speed of reaction) vs. cost of the catalyst and cost of the apparatus required for use of high pressures. Notice that the Raney-nickel catalysed hydrogenations require high pressures: Catalysts are usually classified into two broad classes: homogeneous catalysts and heterogeneou... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation In industry, precious metal hydrogenation catalysts are deposited from solution as a fine powder on the support, which is a cheap, bulky, porous, usually granular material, such as activated carbon, alumina, calcium carbonate or barium sulfate. For example, platinum on carbon is produced by reduction of c... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation For example, when the catalyst palladium is placed on barium sulfate and then treated with quinoline, the resulting catalyst reduces alkynes only as far as alkenes. The Lindlar catalyst has been applied to the conversion of phenylacetylene to styrene. Transfer hydrogenation uses other hydrogen donor molec... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation In the hydrogenation of vegetable oils and fatty acids, for example, the heat released, about 25 kcal per mole (105 kJ/mol), is sufficient to raise the temperature of the oil by 1.6–1.7 °C per iodine number drop. However, the reaction rate for most hydrogenation reactions is negligible in the absence of c... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation The cyclohexene is ordinarily reduced immediately to a fully saturated cyclohexane, but special modifications to the catalysts (such as the use of the anti-solvent water on ruthenium) can preserve some of the cyclohexene, if that is a desired product. In many homogeneous hydrogenation processes, the metal... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation Changing the degree of saturation of the fat changes some important physical properties, such as the melting range, which is why liquid oils become semi-solid. Solid or semi-solid fats are preferred for baking because the way the fat mixes with flour produces a more desirable texture in the baked product.... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation trans fats) and towards fully hydrogenated fats and interesterified fats in response to bad publicity about trans fats, labeling requirements, and removal of trans fats from the FDA list of foods Generally Recognized as Safe. In petrochemical processes, hydrogenation is used to convert alkenes and aromati... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation Primary amines can be synthesized by hydrogenation of nitriles, while nitriles are readily synthesized from cyanide and a suitable electrophile. For example, isophorone diamine, a precursor to the polyurethane monomer isophorone diisocyanate, is produced from isophorone nitrile by a tandem nitrile hydroge... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation In 1922, Voorhees and Adams described an apparatus for performing hydrogenation under pressures above one atmosphere. The Parr shaker, the first product to allow hydrogenation using elevated pressures and temperatures, was commercialized in 1926 based on Voorhees and Adams' research and remains in widespr... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation One such system for reduction of ketones consists of "tert"-butanol and potassium tert-butoxide and very high temperatures. The reaction depicted below describes the hydrogenation of benzophenone: A chemical kinetics study found this reaction is first-order in all three reactants suggesting a cyclic 6-mem... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation Since many hydrogenation reactions such as hydrogenolysis of protecting groups and the reduction of aromatic systems proceed extremely sluggishly at atmospheric temperature and pressure, pressurised systems are popular. In these cases, catalyst is added to a solution of reactant under an inert atmosphere ... | https://en.wikipedia.org/wiki?curid=235968 |
Hydrogenation Catalyst loading is typically much lower than in laboratory batch hydrogenation, and various promoters are added to the metal, or mixed metals are used, to improve activity, selectivity and catalyst stability. The use of nickel is common despite its low activity, due to its low cost compared to precious m... | https://en.wikipedia.org/wiki?curid=235968 |
Éleuthère Irénée du Pont de Nemours (; ; 24 June 1771 – 31 October 1834), known as Irénée du Pont, or E. I. du Pont, was a French-American chemist and industrialist who founded the gunpowder manufacturer E. I. du Pont de Nemours and Company. His descendants, the du Pont family, have been one of America's richest and mo... | https://en.wikipedia.org/wiki?curid=235994 |
Éleuthère Irénée du Pont Two years later, he was accepted by the friend of his father and noted chemist Antoine Lavoisier as a student in the "Régie des poudres", the government agency responsible for the manufacture of gunpowder. It was from Lavoisier that he gained his expertise in nitrate extraction and manufacture.... | https://en.wikipedia.org/wiki?curid=235994 |
Éleuthère Irénée du Pont These events led his father to lose hope in the political situation in France, and so he began making plans to move their family to America and aspired to create a model community of French "émigrés." On 2 October 1799, the du Pont family sold their publishing house and set sail for the United ... | https://en.wikipedia.org/wiki?curid=235994 |
Éleuthère Irénée du Pont Du Pont commented on the inferior quality of the American-made powder they were using for hunting despite its high price. At his request, Tousard arranged a tour of an American powder plant. He quickly deduced that the saltpeter being used was of good enough quality, however, the American refin... | https://en.wikipedia.org/wiki?curid=235994 |
Éleuthère Irénée du Pont The company he founded would become one of the largest and most successful American corporations. By the mid-19th century it was the largest supplier of gunpowder to the U.S. military, and supplied as much as 40 percent of the powder used by the Union Army forces during the Civil War. His sons,... | https://en.wikipedia.org/wiki?curid=235994 |
Ribozyme Ribozymes (ribonucleic acid enzymes) are RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of protein enzymes. The 1982 discovery of ribozymes demonstrated that RNA can be both genetic material (like DNA) and a biolo... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme The "tC19Z" ribozyme can add up to 95 nucleotides with a fidelity of 0.0083 mutations/nucleotide. Attempts have been made to develop ribozymes as therapeutic agents, as enzymes which target defined RNA sequences for cleavage, as biosensors, and for applications in functional genomics and gene discovery. Before... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme RNA, in essence, can be both the chicken and the egg. In the 1980s Thomas Cech, at the University of Colorado at Boulder, was studying the excision of introns in a ribosomal RNA gene in "Tetrahymena thermophila". While trying to purify the enzyme responsible for the splicing reaction, he found that the intron ... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme Many ribozymes have either a hairpin – or hammerhead – shaped active center and a unique secondary structure that allows them to cleave other RNA molecules at specific sequences. It is now possible to make ribozymes that will specifically cleave any RNA molecule. These RNA catalysts may have pharmaceutical app... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme In the first mechanism, the internal 2’- OH group attacks phosphorus center in a SN mechanism. Metal ions promote this reaction by first coordinating the phosphate oxygen and later stabling the oxyanion. The second mechanism also follows a SN displacement, but the nucleophile comes from water or exogenous hydr... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme For example, the functional part of the ribosome, the biological machine that translates RNA into proteins, is fundamentally a ribozyme, composed of RNA tertiary structural motifs that are often coordinated to metal ions such as Mg as cofactors. In a model system, there is no requirement for divalent cations i... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme An example of a self-replicating ribozyme that ligates two substrates to generate an exact copy of itself was described in 2002. Since the discovery of ribozymes that exist in living organisms, there has been interest in the study of new synthetic ribozymes made in the laboratory. For example, artificially-pro... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme One approach for selecting a ligase ribozyme involves using biotin tags, which are covalently linked to the substrate. If a molecule possesses the desired ligase activity, a streptavidin matrix can be used to recover the active molecules. Lincoln and Joyce developed an RNA enzyme system capable of self replica... | https://en.wikipedia.org/wiki?curid=237132 |
Ribozyme Much of this RNA engineering work was based on rational design and previously determined RNA structures rather than directed evolution as in the above examples. More recent work has broadened the ligands used in ribozyme riboswitches to include thymine pyrophosphate (2). Fluorescence-activated_cell_sorting has... | https://en.wikipedia.org/wiki?curid=237132 |
Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or formula_1 within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials the ultimate tensile strength is close to the yield point, whereas in duc... | https://en.wikipedia.org/wiki?curid=237207 |
Ultimate tensile strength For some non-homogeneous materials (or for assembled components) it can be reported just as a force or as a force per unit width. In the International System of Units (SI), the unit is the pascal (Pa) (or a multiple thereof, often megapascals (MPa), using the SI prefix "mega"); or, equivalentl... | https://en.wikipedia.org/wiki?curid=237207 |
Ultimate tensile strength After the yield point, ductile metals undergo a period of strain hardening, in which the stress increases again with increasing strain, and they begin to neck, as the cross-sectional area of the specimen decreases due to plastic flow. In a sufficiently ductile material, when necking becomes su... | https://en.wikipedia.org/wiki?curid=237207 |
Ultimate tensile strength This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers. This practical correlation helps quality assurance in metalworking industries to extend well beyond the... | https://en.wikipedia.org/wiki?curid=237207 |
Electron density In chemistry electron density is the measure of the probability of an electron being present at a specific location. According to quantum mechanics, due to the uncertainty principle on an atomic scale the exact location of an electron cannot be predicted, only the probability of its being at a given po... | https://en.wikipedia.org/wiki?curid=237630 |
Electron density Conjugated systems can sometimes represent regions where electromagnetic radiation is absorbed at different wavelengths resulting in compounds appearing coloured. In polymers, these areas are known as chromophores. In quantum chemical calculations, the electron density, ρ(r), is a function of the coord... | https://en.wikipedia.org/wiki?curid=237630 |
Electron density Depending on the isovalue (typical units are electrons per cubic bohr), or the percentage of total electrons enclosed, the electron density surface can be used to locate atoms, emphasize electron densities associated with chemical bonds , or to indicate overall molecular size and shape. Graphically, th... | https://en.wikipedia.org/wiki?curid=237630 |
Electron density Quantum electrodynamics and some branches of quantum theory also study and analyze electron superposition and other related phenomena, such as the NCI index which permits the study of non-covalent interactions using electron density. Mulliken population analysis is based on electron densities in molecu... | https://en.wikipedia.org/wiki?curid=237630 |
Conjugated system In chemistry, a conjugated system is a system of connected p orbitals with delocalized electrons in a molecule, which in general lowers the overall energy of the molecule and increases stability. It is conventionally represented as having alternating single and multiple bonds. Lone pairs, radicals or ... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system Oxygen has two lone pairs, one of which occupies a p orbital perpendicular to the ring on that position, thereby maintaining the conjugation of that five-membered ring by overlap with the perpendicular p orbital on each of the adjacent carbon atoms. The other lone pair remains in plane and does not pa... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system Although σ bonding can be treated using a delocalized approach as well, it is generally the π bonding that is being considered when delocalized bonding is invoked in the context of simple organic molecules. "Sigma (σ) framework": The σ framework is described by a strictly localized bonding scheme and ... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system The interaction that results in π bonding takes place between p orbitals that are adjacent by virtue of a σ bond joining the atoms and takes the form of side-to-side overlap of the two equally large lobes that make up each p orbital. Atoms that are sp-hybridized do not have an unhybridized p orbital a... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system Bonds in strained small rings (such as cyclopropane or epoxide) are not well-described by strict σ/π separation, as bonding between atoms in the ring consists of "bent bonds" or "banana bonds" that are bowed outward and are intermediate in nature between σ and π bonds. Nevertheless, organic chemists f... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system In compliance with the Pauli exclusion principle, overlapping p orbitals "do not" result in the formation of one large MO containing more than two electrons. Hückel MO theory is commonly used approach to obtain a zeroth order picture of delocalized π molecular orbitals, including the mathematical sign... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system Comparison of heats of hydrogenation of 1,4-pentadiene and 1,3-pentadiene estimates a slightly more modest value of 3.5 kcal/mol. For comparison, allyl cation has a gas-phase rotation barrier of around 38 kcal/mol, a much greater penalty for loss of conjugation. Comparison of hydride ion affinities of... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system Unambiguous examples are comparatively rare in neutral systems, due to a comparatively minor energetic benefit that is easily overridden by a variety of other factors; however, they are common in cationic systems in which a large energetic benefit can be derived from delocalization of positive charge ... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system The classic example benzene has a system of six π electrons, which, together with the planar ring of C–C σ bonds containing 12 electrons and radial C–H σ bonds containing six electrons, forms the thermodynamically and kinetically stable "benzene ring", the common core of the benzenoid aromatic compoun... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system The molecule typically adopts a "tub" conformation. Because the p orbitals of the molecule do not align themselves well in this non-planar molecule, the π bonds are essentially isolated and not conjugated. The lack of conjugation allows the 8 π electron molecule to avoid antiaromaticity, a destabilizi... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system In a conjugated pi-system, electrons are able to capture certain photons as the electrons resonate along a certain distance of p-orbitals - similar to how a radio antenna detects photons along its length. Typically, the more conjugated (longer) the pi-system is, the longer the wavelength of photon can... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system For a chain of "n" C=C bonds or 2"n" carbon atoms in the molecular ground state, there are 2"n" π electrons occupying "n" molecular orbitals, so that the energy gap is Since the box length "L" increases approximately linearly with the number of C=C bonds "n", this means that the energy Δ"E" of a photo... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system Conjugated systems of fewer than eight conjugated double bonds absorb only in the ultraviolet region and are colorless to the human eye. With every double bond added, the system absorbs photons of longer wavelength (and lower energy), and the compound ranges from yellow to red in color. Compounds that... | https://en.wikipedia.org/wiki?curid=237636 |
Conjugated system A similar molecular structural ring unit called chlorin is similarly complexed with magnesium instead of iron when forming part of the most common forms of chlorophyll molecules, giving them a green color. Another similar macrocycle unit is corrin, which complexes with cobalt when forming part of coba... | https://en.wikipedia.org/wiki?curid=237636 |
Rydberg formula In atomic physics, the calculates the wavelengths of a spectral line in many chemical elements. The formula was primarily presented as a generalization of the Balmer series for all atomic electron transitions of hydrogen. It was first empirically stated in 1888 by the Swedish physicist Johannes Rydberg,... | https://en.wikipedia.org/wiki?curid=237708 |
Rydberg formula Rydberg was trying: formula_2 when he became aware of Balmer's formula for the hydrogen spectrum formula_3 In this equation, "m" is an integer and "h" is a constant (not to be confused with the later Planck constant). Rydberg therefore rewrote Balmer's formula in terms of wavenumbers, as formula_4. This... | https://en.wikipedia.org/wiki?curid=237708 |
Rydberg formula Ritz's "pre-quantum" 1908 explanation for the "mechanism" underlying the spectral series was that atomic electrons behaved like magnets and that the magnets could vibrate with respect to the atomic nucleus (at least temporarily) to produce electromagnetic radiation, but this theory was superseded in 191... | https://en.wikipedia.org/wiki?curid=237708 |
Rydberg formula But the also provides correct wavelengths for distant electrons, where the effective nuclear charge can be estimated as the same as that for hydrogen, since all but one of the nuclear charges have been screened by other electrons, and the core of the atom has an effective positive charge of +1. Finally,... | https://en.wikipedia.org/wiki?curid=237708 |
Rydberg formula See the biography of Henry Moseley for the historical importance of this law, which was derived empirically at about the same time it was explained by the Bohr model of the atom. For other spectral transitions in multi-electron atoms, the generally provides "incorrect" results, since the magnitude of th... | https://en.wikipedia.org/wiki?curid=237708 |
Deformation (engineering) In engineering, deformation refers to the change in size or shape of an object. "Displacements" are the "absolute" change in position of a point on the object. Deflection is the relative change in external displacements on an object. Strain is the "relative" internal change in shape of an infi... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) In the figure it can be seen that the compressive loading (indicated by the arrow) has caused deformation in the cylinder so that the original shape (dashed lines) has changed (deformed) into one with bulging sides. The sides bulge because the material, although strong enough to not crack or o... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) Engineering strain is modeled by infinitesimal strain theory, also called "small strain theory", "small deformation theory", "small displacement theory", or "small displacement-gradient theory" where strains and rotations are both small. For some materials, e.g. elastomers and polymers, subjec... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) Since we disregard the change of area during deformation above, the true stress and strain curve should be re-derived. For deriving the stress strain curve, we can assume that the volume change is 0 even if we deformed the materials. We can assume that: Then, the true stress can be expressed a... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) 2) In reality, stress is also highly dependent on the rate of strain variation. Thus, we can induce the empirical equation based on the strain rate variation. Where formula_19 is constant related to the material flow stress. formula_20 indicates the derivative of strain by the time, which is a... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) 4) A graphical method, so-called "Considere construction", can help determine the behavior of stress-strain curve whether necking or drawing happens on the sample. By setting formula_26as determinant, the true stress and strain can be expressed with engineering stress and strain as below: Ther... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) An object in the plastic deformation range, however, will first have undergone elastic deformation, which is undone simply be removing the applied force, so the object will return part way to its original shape. Soft thermoplastics have a rather large plastic deformation range as do ductile me... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) After many deformations, cracks will begin to appear, followed soon after by a fracture, with no apparent plastic deformation in between. Depending on the material, shape, and how close to the elastic limit it is deformed, failure may require thousands, millions, billions, or trillions of defo... | https://en.wikipedia.org/wiki?curid=237876 |
Deformation (engineering) According to the properties of the material, failure modes are yielding for materials with ductile behavior (most metals, some soils and plastics) or rupturing for brittle behavior (geomaterials, cast iron, glass, etc.). In long, slender structural elements — such as columns or truss bars — an... | https://en.wikipedia.org/wiki?curid=237876 |
Warfarin Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to treat blood clots such as deep vein thrombosis and pulmonary embolism and to prevent stroke in people who have atrial fibrillation, valvular heart disease or artif... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin In 1954 it was approved for medical use in the United States. It is on the World Health Organization's List of Essential Medicines, the safest and most effective medicines needed in a health system. is available as a generic medication. The wholesale cost in the developing world is about US$1.12 to 7.20 for a ... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin Prevention of clotting in arteries is usually undertaken with antiplatelet drugs, which act by a different mechanism from warfarin (which normally has no effect on platelet function). It can be used to treat people following an ischemic strokes due to atrial fibrillation, though direct oral anticoagulants (DOA... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin In addition, for the first three days of "warfarinization", the levels of protein C and protein S (anticoagulation factors) drop faster than procoagulation proteins such as factor II, VII, IX, and X. Therefore, bridging anticoagulant therapies (usually heparin) are often used to reverse this temporary hypercoa... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin The guidelines stated: "The consensus agrees that patient self-testing and patient self-management are effective methods of monitoring oral anticoagulation therapy, providing outcomes at least as good as, and possibly better than, those achieved with an anticoagulation clinic. All patients must be appropriatel... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin This includes people with active bleeding conditions (such as gastrointestinal ulcers), or disease states with increased risk of bleeding e.g. low platelets, severe liver disease, uncontrolled hypertension. For patients undergoing surgery, treatment with anticoagulants is generally suspended. Similarly, spinal... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin With heparin, risk of maternal haemorrhage and other complications are still increased, but heparins do not cross the placental barrier, so do not cause birth defects. Various solutions exist for the time around delivery. When warfarin (or another 4-hydroxycoumarin derivative) is given during the first trimest... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin Because of such later pregnancy birth defects, anticoagulation with warfarin poses a problem in pregnant women requiring warfarin for vital indications, such as stroke prevention in those with artificial heart valves. According to the American College of Chest Physicians (ACCP), warfarin may be used in lactati... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin aspirin) or alcohol misuse (D). While their use is recommended in clinical practice guidelines, they are only moderately effective in predicting bleeding risk and do not perform well in predicting hemorrhagic stroke. Bleeding risk may be increased in people on hemodialysis. Another score used to assess bleedin... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin After initial reports that warfarin could reduce bone mineral density, several studies have demonstrated a link between warfarin use and osteoporosis-related fracture. A 1999 study in 572 women taking warfarin for deep venous thrombosis, risk of vertebral fracture and rib fracture was increased; other fracture... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin It is typically thought to affect the big toe, but it affects other parts of the feet as well, including the bottom of the foot (plantar surface). The occurrence of purple toe syndrome may require discontinuation of warfarin. Several studies have also implicated warfarin use in valvular and vascular calcificat... | https://en.wikipedia.org/wiki?curid=238097 |
Warfarin Details on reversing warfarin are provided in clinical practice guidelines from the American College of Chest Physicians. For people with an international normalized ratio (INR) between 4.5 and 10.0, a small dose (about 1000 mcg = one milligram) of oral vitamin K is sufficient. When warfarin is being given and... | https://en.wikipedia.org/wiki?curid=238097 |
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