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Amines reacts with nitrous acid to give diazonium salts. The alkyl diazonium salts are of little importance because they are too unstable. The most important members are derivatives of aromatic amines such as aniline ("phenylamine") (A = aryl or naphthyl):
Anilines and naphthylamines form more stable diazonium salts, which can be isolated in the crystalline form. Diazonium salts undergo a variety of useful transformations involving replacement of the group with anions. For example, cuprous cyanide gives the corresponding nitriles:
Aryldiazoniums couple with electron-rich aromatic compounds such as a phenol to form azo compounds. Such reactions are widely applied to the production of dyes. | 0 | Theoretical and Fundamental Chemistry |
Salt metathesis reaction of salts such as KCo(CO) with [Ru(CO)Cl] leads selectively to mixed-metal carbonyls such as RuCo(CO).
:4 KCo(CO) + [Ru(CO)Cl] → 2 RuCo(CO) + 4 KCl + 11 CO | 0 | Theoretical and Fundamental Chemistry |
Radiation embrittlement, also known as neutron embrittlement, is a phenomenon more commonly observed in reactors and nuclear plants as these materials are constantly exposed to a steady amount of radiation. When a neutron irradiates the metal, voids are created in the material, which is known as void swelling. If the material is under creep (under low strain rate and high temperature condition), the voids will coalesce into vacancies which compromises the mechanical strength of the workpiece. | 1 | Applied and Interdisciplinary Chemistry |
Among several variants of thermal cracking methods (variously known as the "Shukhov cracking process", "Burton cracking process", "Burton-Humphreys cracking process", and "Dubbs cracking process") Vladimir Shukhov, a Russian engineer, invented and patented, the first in 1891 (Russian Empire, patent no. 12926, November 7, 1891). One installation was used to a limited extent in Russia, but development was not followed up; In the first decade of the 20th century the American engineers William Merriam Burton and Robert E. Humphreys independently developed and patented a similar process as U.S. patent 1,049,667 on June 8, 1908. Among its advantages was that both the condenser and the boiler were continuously kept under pressure.
In its earlier versions it was a batch process, rather than continuous, and many patents were to follow in the US and Europe, though not all were practical. In 1924, a delegation from the American Sinclair Oil Corporation visited Shukhov. Sinclair Oil apparently wished to suggest that the patent of Burton and Humphreys, in use by Standard Oil, was derived from Shukhovs patent for oil cracking, as described in the Russian patent. If that could be established, it could strengthen the hand of rival American companies wishing to invalidate the Burton-Humphreys patent. In the event Shukhov satisfied the Americans that in principle Burtons method closely resembled his 1891 patents, though his own interest in the matter was primarily to establish that "the Russian oil industry could easily build a cracking apparatus according to any of the described systems without being accused by the Americans of borrowing for free".
At that time, just a few years after the Russian Revolution and brutal Russian Civil War, the Soviet Union was desperate to develop industry and earn foreign exchange, so their oil industry eventually did obtain much of their technology from foreign companies, largely American. At about that time, fluid catalytic cracking was being explored and developed and soon replaced most of the purely thermal cracking processes in the fossil fuel processing industry. The replacement was not complete; many types of cracking, including pure thermal cracking, still are in use, depending on the nature of the feedstock and the products required to satisfy market demands. Thermal cracking remains important, for example in producing naphtha, gas oil, and coke, and more sophisticated forms of thermal cracking have been developed for various purposes. These include visbreaking, steam cracking, and coking. | 0 | Theoretical and Fundamental Chemistry |
In atherosclerosis, a severe disease in modern society, coronary blood vessels occlude. These vessels have to be freed and held open i.e. by stents. Unfortunately after certain time these vessels close again and have to be bypassed to allow for upkeep of circulation. Usually autologous vessels from the patient or synthetic polymer grafts are used for this purpose. Both options have disadvantages. Firstly there are only few autologous vessels available in a human body that might be of low quality, considering the health status of the patient. The synthetic polymer based grafts on the other hand often have insufficient haemocompatibility and thus rapidly occlude - a problem that is especially prone in small calibre grafts. In this context the fibrin-gel-based tissue engineering of autologous vessel substitutes is a very promising approach to overcome the current problems. Cells and fibrin are isolated by a low invasive procedure from the patient and shaped in individual moulds to meet the required dimensions. Additional pre-cultivation in a specialized bioreactor is inevitable to ensure appropriate properties of the graft. | 1 | Applied and Interdisciplinary Chemistry |
The spacing d between adjacent (hkℓ) lattice planes is given by:
*Cubic:
*Tetragonal:
*Hexagonal:
*Rhombohedral (primitive setting):
*Orthorhombic:
*Monoclinic:
*Triclinic: | 0 | Theoretical and Fundamental Chemistry |
In a two-layer model, the boundary layer is considered to comprise two layers: inner (close to the surface) and outer. The eddy viscosity is calculated separately for each layer and combined using:
where is the smallest distance from the surface where is equal to .
The inner-region eddy viscosity is given by:
where
with the von Karman constant usually being taken as 0.4, and with
The eddy viscosity in the outer region is given by:
where , is the displacement thickness, given by
and F is the Klebanoff intermittency function given by | 1 | Applied and Interdisciplinary Chemistry |
In 1912, Frederick Gowland Hopkins demonstrated that unknown accessory factors found in milk, other than carbohydrates, proteins, and fats were necessary for growth in rats. Hopkins received a Nobel Prize for this discovery in 1929. By 1913, one of these substances was independently discovered by Elmer McCollum and Marguerite Davis at the University of Wisconsin–Madison, and Lafayette Mendel and Thomas Burr Osborne at Yale University. McCollum and Davis ultimately received credit because they submitted their paper three weeks before Mendel and Osborne. Both papers appeared in the same issue of the Journal of Biological Chemistry in 1913. The "accessory factors" were termed "fat soluble" in 1918, and later "vitamin A" in 1920. In 1919, Harry Steenbock (University of Wisconsin–Madison) proposed a relationship between yellow plant pigments (beta-carotene) and vitamin A. In 1931, Swiss chemist Paul Karrer described the chemical structure of vitamin A. Retinoic acid and retinol were first synthesized in 1946 and 1947 by two Dutch chemists, David Adriaan van Dorp and Jozef Ferdinand Arens.
During World War II, German bombers would attack at night to evade British defenses. In order to keep the 1939 invention of a new on-board Airborne Intercept Radar system secret from Germany, the British Ministry of Information told newspapers an unproven claim that the nighttime defensive success of Royal Air Force pilots was due to a high dietary intake of carrots rich in beta-carotene, successfully convincing many people.
In 1967, George Wald shared the Nobel Prize in Physiology and Medicine for his work on chemical visual processes in the eye. Wald had demonstrated in 1935 that photoreceptor cells in the eye contain rhodopsin, a chromophore composed of the protein opsin and 11-cis-retinal. When struck by light, 11-cis-retinal undergoes photoisomerization to all-trans-retinal and via signal transduction cascade send a nerve signal to the brain. The all-trans-retinal is reduced to all-trans-retinol and travels back to the retinal pigment epithelium to be recycled to 11-cis-retinal and reconjugated to opsin. Wald's work was the culmination of nearly 60 years of research. In 1877, Franz Christian Boll identified a light-sensitive pigment in the outer segments of rod cells of the retina that faded/bleached when exposed to light, but was restored after light exposure ceased. He suggested that this substance, by a photochemical process, conveyed the impression of light to the brain. The research was taken up by Wilhelm Kühne, who named the pigment rhodopsin, also known as "visual purple." Kühne confirmed that rhodopsin is extremely sensitive to light, and thus enables vision in low-light conditions, and that it was this chemical decomposition that stimulated nerve impulses to the brain. Research stalled until after identification of "fat-soluble vitamin A" as a dietary substance found in milkfat but not lard, would reverse night blindness and xerophthalmia. In 1925, Fridericia and Holm demonstrated that vitamin A deficient rats were unable to regenerate rhodopsin after being moved from a light to a dark room. | 1 | Applied and Interdisciplinary Chemistry |
Aromaticity is found in ions as well: the cyclopropenyl cation (2e system), the cyclopentadienyl anion (6e system), the tropylium ion (6e), and the cyclooctatetraene dianion (10e). Aromatic properties have been attributed to non-benzenoid compounds such as tropone. Aromatic properties are tested to the limit in a class of compounds called cyclophanes.
A special case of aromaticity is found in homoaromaticity where conjugation is interrupted by a single sp³ hybridized carbon atom.
When carbon in benzene is replaced by other elements in borabenzene, silabenzene, germanabenzene, stannabenzene, phosphorine or pyrylium salts the aromaticity is still retained. Aromaticity also occurs in compounds that are not carbon-based at all. Inorganic 6-membered-ring compounds analogous to benzene have been synthesized. Hexasilabenzene (SiH) and borazine (BNH) are structurally analogous to benzene, with the carbon atoms replaced by another element or elements. In borazine, the boron and nitrogen atoms alternate around the ring. Quite recently, the aromaticity of planar Si rings occurring in the Zintl phase LiSi was experimentally evidenced by Li solid state NMR.
Metal aromaticity is believed to exist in certain metal clusters of aluminium.
Möbius aromaticity occurs when a cyclic system of molecular orbitals, formed from p atomic orbitals and populated in a closed shell by 4n (n is an integer) electrons, is given a single half-twist to correspond to a Möbius strip. A π system with 4n electrons in a flat (non-twisted) ring would be anti-aromatic, and therefore highly unstable, due to the symmetry of the combinations of p atomic orbitals. By twisting the ring, the symmetry of the system changes and becomes allowed (see also Möbius–Hückel concept for details). Because the twist can be left-handed or right-handed, the resulting Möbius aromatics are dissymmetric or chiral.
As of 2012, there is no proof that a Möbius aromatic molecule was synthesized.
Aromatics with two half-twists corresponding to the paradromic topologies were first suggested by Johann Listing. In carbo-benzene the ring bonds are extended with alkyne and allene groups. | 0 | Theoretical and Fundamental Chemistry |
The different biomolecules that make up a plant's biogenic substances – particularly those in seed exudates - can be identified by using different varieties of chromatography in a lab environment. For metabolite profiling, gas chromatography-mass spectrometry is used to find flavonoids such as quercetin. Compounds can then be further differentiated using reversed-phase high-performance liquid chromatography-mass spectrometry.
When it comes to measuring biogenic substances in a natural environment such as a body of water, a hydroecological CNPSi model can be used to calculate the spatial transport of biogenic substances, in both the horizontal and vertical dimensions. This model takes into account the water exchange and flow rate, and yields the values of biogenic substance rates for any area or layer of the water for any month. There are two main evaluation methods involved: measuring per unit water volume (mg/m year) and measuring substances per entire water volume of layer (t of element/year). The former is mostly used to observe biogenic substance dynamics and individual pathways for flux and transformations, and is useful when comparing individual regions of the strait or waterway. The second method is used for monthly substance fluxes and must take into account that there are monthly variations in the water volume in the layers.
In the study of geochemistry, biogenic substances can be isolated from fossils and sediments through a process of scraping and crushing the target rock sample, then washing with 40% hydrofluoric acid, water, and benzene/methanol in the ratio 3:1. Following this, the rock pieces are ground and centrifuged to produce a residue. Chemical compounds are then derived through various chromatography and mass spectrometry separations. However, extraction should be accompanied by rigorous precautions to ensure there is no amino acid contaminants from fingerprints, or silicone contaminants from other analytical treatment methods. | 0 | Theoretical and Fundamental Chemistry |
The closure member of the valve, plugs are connected to the stem which is slid or screwed up or down to throttle the flow. Plugs are typically of the balance or unbalanced type. Unbalanced plugs are solid and are used with smaller valves or with low pressure drops across the valve. The advantages are simpler design, with one possible leak path at the seat and usually lower cost. The disadvantages are the limited size; with a large unbalanced plug the forces needed to seat and hold the flow often becomes impractical. Balanced plugs have holes through the plug. Advantages include easier shut off as the plug does not have to overcome static forces. However, a second leak path is created between the plug and the cage, and cost is generally higher. | 1 | Applied and Interdisciplinary Chemistry |
HCV research has taken great strides in recent years with the discovery and clinical development of multiple new HCV drugs. Among those drugs are the DAAs which include NS5A inhibitors.
NS5A inhibitors have been found particularly effective in the treatment of HCV where they have been used in combination with other protease inhibitors such as NS5B inhibitors (e.g. sofosbuvir), pegylated interferons (e.g. peginterferon alfa-2a), and ribonucleic analogs (e.g. ribavirin). The ever present risk of viral strains developing resistance has been a main factor in why they are used in combination with one or more complementary drug.
Adverse effects, and extensive and complicated drug regimens with accompanying low compliance rates, have been a hindrance in the development of antiviral treatments. The combination of NS5A and NS5B inhibitors has produced positive results in this regard. | 1 | Applied and Interdisciplinary Chemistry |
Voltage-gated ion channels open and close in response to membrane potential.
*Voltage-gated sodium channels: This family contains at least 9 members and is largely responsible for action potential creation and propagation. The pore-forming α subunits are very large (up to 4,000 amino acids) and consist of four homologous repeat domains (I-IV) each comprising six transmembrane segments (S1-S6) for a total of 24 transmembrane segments. The members of this family also coassemble with auxiliary β subunits, each spanning the membrane once. Both α and β subunits are extensively glycosylated.
*Voltage-gated calcium channels: This family contains 10 members, though these are known to coassemble with αδ, β, and γ subunits. These channels play an important role in both linking muscle excitation with contraction as well as neuronal excitation with transmitter release. The α subunits have an overall structural resemblance to those of the sodium channels and are equally large.
**Cation channels of sperm: This small family of channels, normally referred to as Catsper channels, is related to the two-pore channels and distantly related to TRP channels.
*Voltage-gated potassium channels (K): This family contains almost 40 members, which are further divided into 12 subfamilies. These channels are known mainly for their role in repolarizing the cell membrane following action potentials. The α subunits have six transmembrane segments, homologous to a single domain of the sodium channels. Correspondingly, they assemble as tetramers to produce a functioning channel.
*Some transient receptor potential channels: This group of channels, normally referred to simply as TRP channels, is named after their role in Drosophila phototransduction. This family, containing at least 28 members, is incredibly diverse in its method of activation. Some TRP channels seem to be constitutively open, while others are gated by voltage, intracellular Ca, pH, redox state, osmolarity, and mechanical stretch. These channels also vary according to the ion(s) they pass, some being selective for Ca while others are less selective, acting as cation channels. This family is subdivided into 6 subfamilies based on homology: classical (TRPC), vanilloid receptors (TRPV), melastatin (TRPM), polycystins (TRPP), mucolipins (TRPML), and ankyrin transmembrane protein 1 (TRPA).
*Hyperpolarization-activated cyclic nucleotide-gated channels: The opening of these channels is due to hyperpolarization rather than the depolarization required for other cyclic nucleotide-gated channels. These channels are also sensitive to the cyclic nucleotides cAMP and cGMP, which alter the voltage sensitivity of the channel's opening. These channels are permeable to the monovalent cations K and Na. There are 4 members of this family, all of which form tetramers of six-transmembrane α subunits. As these channels open under hyperpolarizing conditions, they function as pacemaking channels in the heart, particularly the SA node.
*Voltage-gated proton channels: Voltage-gated proton channels open with depolarization, but in a strongly pH-sensitive manner. The result is that these channels open only when the electrochemical gradient is outward, such that their opening will only allow protons to leave cells. Their function thus appears to be acid extrusion from cells. Another important function occurs in phagocytes (e.g. eosinophils, neutrophils, macrophages) during the "respiratory burst." When bacteria or other microbes are engulfed by phagocytes, the enzyme NADPH oxidase assembles in the membrane and begins to produce reactive oxygen species (ROS) that help kill bacteria. NADPH oxidase is electrogenic, moving electrons across the membrane, and proton channels open to allow proton flux to balance the electron movement electrically. | 1 | Applied and Interdisciplinary Chemistry |
Fallout can also refer to nuclear accidents, although a nuclear reactor does not explode like a nuclear weapon. The isotopic signature of bomb fallout is very different from the fallout from a serious power reactor accident (such as Chernobyl or Fukushima).
The key differences are in volatility and half-life. | 0 | Theoretical and Fundamental Chemistry |
Tetramethyl­ammonium fluoride is the quaternary ammonium salt with the formula (CH)NF. This hygroscopic white solid is a source of “naked fluoride": fluoride ions not complexed with a metal atom. Most other soluble salts of fluoride are in fact bifluorides, HF. Historically, there have been two main approaches to prepare tetramethyl­ammonium fluoride: hydrofluoric acid neutralization of tetramethyl­ammonium hydroxide, and salt metathesis between different ammonium salts and inorganic fluoride sources, such as KF or CsF. Because the fluoride anion is extremely basic, the salt slowly reacts with acetonitrile, inducing dimerization to CHC(NH)=CHCN, which co-crystallizes. | 0 | Theoretical and Fundamental Chemistry |
Push-pull agriculture leads to beneficial economic outcomes on the level of individual smallholder and subsistence farmers through larger income streams coming from the sale of surplus grain, desmodium seeds, fodder, and milk. Economic study has calculated the return on investment of push-pull methods for farmers to be over 2.2 as compared to 1.8 for pesticide use, and .8 for monocrop. Although startup costs of push-pull technology are highly variable due to the requirements of labor to plant desmodium and Napier grass and purchase of these seeds, costs significantly decline in following growing years. Push-pull technology has also been seen to help boost local economies. Because these farmers have more income, they are able to spend money in their local economy which boosts the standards of living and prosperity of the community at large.
The primary economic opponents to such methods are large multinational corporations such as Monsanto and others that produce seasonal inputs such as chemical pesticides, fertilizers and high-yield seeds that require such inputs.
After controlling for extraneous maize yield determinants, it was found that there was a 61.9% maize yield increase with a 15.3% increase in the cost of maize production and a 38.6% increase in the average net income brought in from maize.
In households where push-pull technology has been adopted in Kenya, increased economic earnings have been associated with more years of education, improved access to rural institutions, and attendance to a larger number of field days when compared with households that have not adopted the technology. Additionally, if adoption of the technology continues at the current rate of 14.4%, a reduction of 75,077 people considered poor could be expected in a situation where the local economies remain closed, and 76,504 fewer people could be expected to be considered poor if the economies were open. | 1 | Applied and Interdisciplinary Chemistry |
R is the net rate of production of species i by chemical reaction and S is the rate of creation by addition from the dispersed phase and the user defined source. J is the diffusion flux of species i, which arises due to concentration gradients and differs in both laminar and turbulent flows. In turbulent flows, computational fluid dynamics also considers the effects of turbulent diffusivity. The net source of chemical species i due to reaction, R which appeared as the source term in the species transport equation is computed as the sum of the reaction sources over the N reactions among the species. | 1 | Applied and Interdisciplinary Chemistry |
The pressure transmitting medium is the compressible fluid that fills the sample chamber and transmits the applied force to the sample. Hydrostatic pressure is preferred for high-pressure experiments because variation in strain throughout the sample can lead to distorted observations of different behaviors. In some experiments stress and strain relationships are investigated and the effects of non-hydrostatic forces are desired. A good pressure medium will remain a soft, compressible fluid to high pressure.
The full range of techniques that are available has been summarized in a tree diagram by William Bassett. The ability to utilize any and all of these techniques hinges on being able to look through the diamonds which was first demonstrated by visual observations. | 0 | Theoretical and Fundamental Chemistry |
VMA is found in the urine, along with other catecholamine metabolites, including homovanillic acid (HVA), metanephrine, and normetanephrine. In timed urine tests the quantity excreted (usually per 24 hours) is assessed along with creatinine clearance, and the quantity of cortisols, catecholamines, and metanephrines excreted is also measured. | 1 | Applied and Interdisciplinary Chemistry |
"Molecules to the MAX!" is a 41-minute fully animated 3D IMAX film for the Giant Screen. The film re-imagines the characters and story developed for "Molecularium- Riding Snowflakes" for an older audience and a different medium. The film's simulations and rendering were partially computed at the Computational Center for Nanotechnology Innovations. The film was produced by Nanotoon Entertainment and Developed at Rensselaer, with a gift from Curtis R. Priem, co-founder of Nvidia corporation.
The digital version of the film premiered at EMPAC, in Troy, New York, on February 27, 2009. The IMAX version premiered at the Giant Screen Cinema Association International Conference and Trade Show in Indianapolis, Indiana, on September 22, 2009. The IMAX 3D Premiere was at the GSCA Film Expo in Los Angeles on February 24, 2010. It is available in 2D & 3D for 15/70 and 8/70 large format film and in digital 3D. The film has been composed with Omnimax / IMAX Domes in mind. Molecules to the MAX! was nominated for Best Film Produced for the Giant Screen, Best Film for Lifelong Learning and Best Sound Design at the 2010 GSCA’s Achievement Awards. Molecules to the MAX! has shown at the National Museum of Natural Science (Taichung, Taiwan) Maloka Interactive Museum (Bogota, Colombia), The Scientific Center (Salmiya, Kuwait), McWane Science Center (Birmingham, Alabama) Proctor's Theatre (Schenectady, New York) among others. It has been translated and versioned in Spanish, Chinese, Japanese and Arabic. It is distributed to Giant Screen theaters by SK Films. | 1 | Applied and Interdisciplinary Chemistry |
C decays by positron emission with a half-life of ca. 20 min. C is one of the isotopes often used in positron emission tomography.
C decays by beta decay, with a half-life of 5730 years. It is continuously produced in the upper atmosphere of the earth, so it occurs at a trace level in the environment. However, it is not practical to use naturally-occurring C for tracer studies. Instead it is made by neutron irradiation of the isotope C which occurs naturally in carbon at about the 1.1% level. C has been used extensively to trace the progress of organic molecules through metabolic pathways. | 0 | Theoretical and Fundamental Chemistry |
The compound 2-chlorobenzalmalononitrile (also called o-chlorobenzylidene malononitrile; chemical formula: CHClN), a cyanocarbon, is the defining component of tear gas commonly referred to as CS gas, which is used as a riot control agent.
Exposure causes a burning sensation and tearing of the eyes to the extent that the subject cannot keep their eyes open, and a burning irritation of the mucous membranes of the nose, mouth and throat, resulting in profuse coughing, nasal mucus discharge, disorientation, and difficulty breathing, partially incapacitating the subject. CS gas is an aerosol of a volatile solvent (a substance that dissolves other active substances and that easily evaporates) and 2-chlorobenzalmalononitrile, which is a solid compound at room temperature. CS gas is generally accepted as being non-lethal. It was first synthesized by two Americans, Ben Corson and Roger Stoughton, at Middlebury College in 1928, and the chemicals name is derived from the first letters of the scientists surnames.
CS was developed and tested secretly at Porton Down in Wiltshire, UK, in the 1950s and '60s. CS was used first on animals, then subsequently on British Army servicemen volunteers. CS has less effect on animals because they have different tear ducts and, in the case of non-human mammals, their fur inhibits the free entry of the gas. | 1 | Applied and Interdisciplinary Chemistry |
The Magnus effect is an observable phenomenon commonly associated with a spinning object moving through a fluid. A lift force acts on the spinning object. The path of the object may be deflected in a manner not present when the object is not spinning. The deflection can be explained by the difference in pressure of the fluid on opposite sides of the spinning object. The strength of the Magnus effect is dependent on the speed of rotation of the object.
The most readily observable case of the Magnus effect is when a spinning sphere (or cylinder) curves away from the arc it would follow if it were not spinning. It is often used by football (soccer) and volleyball players, baseball pitchers, and cricket bowlers. Consequently, the phenomenon is important in the study of the physics of many ball sports. It is also an important factor in the study of the effects of spinning on guided missiles—and has some engineering uses, for instance in the design of rotor ships and Flettner airplanes.
Topspin in ball games is defined as spin about a horizontal axis perpendicular to the direction of travel that moves the top surface of the ball in the direction of travel. Under the Magnus effect, topspin produces a downward swerve of a moving ball, greater than would be produced by gravity alone. Backspin produces an upwards force that prolongs the flight of a moving ball. Likewise side-spin causes swerve to either side as seen during some baseball pitches, e.g. slider. The overall behaviour is similar to that around an aerofoil (see lift force), but with a circulation generated by mechanical rotation rather than shape of the foil.
The Magnus effect is named after Heinrich Gustav Magnus, the German physicist who investigated it. The force on a rotating cylinder is known as Kutta–Joukowski lift, after Martin Kutta and Nikolay Zhukovsky (or Joukowski), who first analyzed the effect. | 1 | Applied and Interdisciplinary Chemistry |
* Cholera toxin is an AB toxin that has five B subunints and one A subunit. The toxin acts by the following mechanism: First, the B subunit ring of the cholera toxin binds to GM1 gangliosides on the surface of target cells. If a cell lacks GM1 the toxin most likely binds to other types of glycans, such as Lewis Y and Lewis X, attached to proteins instead of lipids. | 1 | Applied and Interdisciplinary Chemistry |
To describe diffraction by a thick mosaic crystal, it is usually assumed that the constituent crystallites are so thin that each of them reflects at most a small fraction of the incident beam. Primary extinction and other dynamical diffraction effects can then be neglected. Reflections by different crystallites add incoherently, and can therefore be treated by classical transport theory. When only beams within the scattering plane are considered, then they obey the Darwin–Hamilton equations (Darwin 1922, Hamilton 1957),
where are the directions of the incident and diffracted beam, are the corresponding currents, μ is the Bragg reflectivity, and σ accounts for losses by absorption and by thermal and elastic diffuse scattering. A generic analytical solution has been obtained remarkably late (Sears 1997; for the case σ=0 Bacon/Lowde 1948). An exact treatment must allow for three-dimensional trajectories of multiply reflected radiation. The Darwin–Hamilton equations are then replaced by a Boltzmann equation with a very special transport kernel. In most cases, resulting corrections to the Darwin–Hamilton–Sears solutions are rather small (Wuttke 2014). | 0 | Theoretical and Fundamental Chemistry |
In eukaryotes, the use of m6A on mRNA involves a methyltransferase complex, commonly termed the Writer, that installs the methyl group. This m6A modification is recognized by special proteins known as Readers. The number of readers varies across different organisms. Notably, in vertebrates, the presence of proteins categorized as Erasers is suggested to facilitate the removal of m6A, which enables a dynamic regulation of m6A deposition on mRNAs.
The mA mark is added by a mA methyltransferase writer complex post-transcriptionally. This writer complex is composed of METTL3, METTL14, Wilms tumor 1-associated protein (WTAP), KIAA1429 and RBM15. METTL3 is the catalytic subunit, whereas METTL14 is involved in the stability of the complex and RNA recruitment. WTAP is also needed in aiding the recruitment of mRNA, whereas RBM15 and its paralog RBM15B are only involved in the recruitment of lncRNAs. The role RBM15 and RBM15B may have in recruiting other types of RNA to the methyltransferase complex remains unknown. The specific recognition sites of the writers are not known, but the minimal sequence required is 5’-RmAC-3’. METTL3 has been proposed to also be a "reader" of the mA mark. This function is localized in the cytoplasm, where it promotes the recruitment of eIF3. Discovery of the METTL3 complex indicated that m6A installation might be a regulated process, which was pivotal for the advancement and interest in the field of epitranscriptomics.
Members of the YTH domain protein family act as "readers" of mA. The study of these proteins has been key in understanding the functions and effects of mRNA methylation. It has been shown that three members of the human YTH domain family of proteins have higher binding affinities to methylated mRNA. The YTH protein YTHDF2 affects mRNA by directing methylated mRNA from the translational pool to mRNA decay sites. As a result, presence of m6A on mRNA is correlated with a shorter half-life than unmethylated mRNA.
So far, two "erasers" of the mA mark have been identified. ALKBH5 is a demethylase found in mammals that removes the methyl group of mA. The second one is the fat mass and obesity associated protein (FTO), a demethylase that converts mA back to adenosine. FTO preferentially demethylates the mA found closer to the mRNA cap. This oxidative process has three steps and two intermediates: N-hydroxymethyladenosine (hmA) and N-formyladenosine (fA). FTO is most commonly found in nuclear speckles; however, in some species low levels of FTO can also be found in the cytoplasm. Dysfunctional FTO correlates with alterations in body weight and disease, while Alkbh5 knockout mice have impaired fertility. These two facts reflect how important the proper regulation of the mA modification is for normal body function. Moreover, mutations in FTO can lead to developmental failures, brain atrophy and physiological disorders in adulthood. | 1 | Applied and Interdisciplinary Chemistry |
The cylindrospermopsin biosynthetic gene cluster (BGC) was described from Cylindrospermopsis raciborskii AWT205 in 2008. | 0 | Theoretical and Fundamental Chemistry |
* Omeprazole (brand names Losec, Prilosec, Zegerid, Ocid, Lomac, Omepral, Omez, Ultop, Ortanol, Gastrozol)
Omeprazole was the first PPI on the market, in 1988. It is a 1:1 racemate drug with a backbone structure of timoprazole, but substituted with two methoxy and two methyl groups. One of the methoxy group is at position 6 of the bensoimidazole and the other at position 4 of the pyridine and the methyl groups are at position 3 and 5 of the pyridine.
Omeprazole is available as enteric-coated tablets, capsules, chewable tablets, powder for oral suspensions and powder for intravenous injection.
* Lansoprazole (brand names: Prevacid, Zoton, Inhibitol, Levant, Lupizole, Lancid, Lansoptol, Epicur)
Lansoprazole was the second of the PPI drugs to reach the market, being launched in Europe in 1991 and the US in 1995.
It has no substitutions at the benzimidazole but two substituents on the pyridine, methyl group at position 3 and a trifluoroethoxy group at position 4. The drug is a 1:1 racemate of the enantiomers dexlansoprazole and levolansoprazole. It is available in gastroresistant capsules and tablets as well as chewable tablets.
* Pantoprazole (brand names: Protonix, Somac, Pantoloc, Pantozol, Zurcal, Zentro, Pan, Nolpaza, Controloc, Sunpras)
Pantoprazole was the third PPI and was introduced to the German market in 1994.
It has a difluoroalkoxy sidegroup on the benzimidazole part and two methoxy groups in position 3 and 4 on the pyridine.
Pantoprazole was first prepared in April 1985 by a small group of scale-up chemists. It is a dimethoxy-substituted pyridine bound to a fluoroalkoxy substituted benzimidazole.
Pantoprazole sodium is available as gastroresistant or delayed release tablets and as lyophilized powder for intravenous use.
* Rabeprazole (brand names: Zechin, Rabecid, Nzole-D, AcipHex, Pariet, Rabeloc, Zulbex, Ontime, Noflux)
Rabeprazole is a novel benzimidazole compound on market, since 1999 in USA. It is similar to lansoprazole in having no substituents on its benzimidazole part and a methyl group at site 3 on the pyridine, the only difference is the methoxypropoxy substitution at site 4 instead of the trifluoroethoxy group on lansoprazole.
Rabeprazole is marketed as rabeprazole sodium salt. It is available as enteric-coated tablets.
* Esomeprazole (brand names: Nexium, Esotrex, Emanera, Neo-Zext)
In 2001 esomeprazole was launched in USA, as a follow-up of omeprazoles patent.
Esomeprazole is the (S)-(−)-enantiomer of omeprazole and provides higher bioavailability and improved efficacy, in terms of stomach acid control, over the (R)-(+)-enantiomer of omeprazole. In theory, by using pure esomeprazole the effects on the proton pump will be equal in all patients, eliminating the "poor metabolizer effect" of the racemate omeprazole. It is available as delayed-release capsules or tablets and as esomeprazole sodium for intravenous injection/infusion. Oral esomeprazole preparations are enteric-coated, due to the rapid degradation of the drug in the acidic condition of the stomach. This is achieved by formulating capsules using the multiple-unit pellet system.
Although the (S)-(−)-isomer is more potent in humans, the (R)-(+)-isomer is more potent in testings of rats, while the enantiomers are equipotent in dogs.
* Dexlansoprazole (brand names: Kapidex, Dexilant)
Dexlansoprazole was launched as a follow up of lansoprazole in 2009.
Dexlansoprazole is an (R)-(+)-enantiomer of lansoprazole, marketed as Dexilant. After oral appliance of the racemic lansoprazole, the circulating drug is 80% dexlansoprazole. Moreover, both enantiomers have similar effects on the proton pump. Consequently, the main advantage of Dexilant is not the fact that it is an enantiopure substance. The advantage is the pharmaceutical formulation of the drug, which is based on a dual release technology, with the first quick release producing a blood plasma peak concentration about one hour after application, and the second retarded release producing another peak about four hours later. | 1 | Applied and Interdisciplinary Chemistry |
Unlike the London Pharmacopoeia, the Edinburgh Pharmacopoeia went through many editions and revisions. In the 142 years from initial publication to the merging into the British Pharmacopoeia, the Edinburgh Pharmacopoeia had twelve acknowledged editions, the last two in English. Opposition to revision argued that it made the pharmacopoeia appear unstable but proponents argued it kept the pharmacopoeia relevant with scientific and medical developments. The last two editions were published in English under the title The Pharmacopoeia of the Royal College of Physicians of Edinburgh. From 1864, the Edinburgh Pharmacopoeia combined with the London and Dublin editions to create the British Pharmacopoeia, which is still in circulation today. | 1 | Applied and Interdisciplinary Chemistry |
In proteomics, the study of the full set of proteins expressed by a genome, identifying diseases biomarkers can involve the usage of stable isotope labeling by amino acids in cell culture (SILAC), that provides isotopic labeled forms of amino acid used to estimate protein levels. In protein recombinant, manipulated proteins are produced in large quantities and isotope labeling is a tool to test for relevant proteins. The method used to be about selectively enrich nuclei with C or N or deplete H from them. The recombinant would be expressed in E.coli with media containing N-ammonium chloride as a source of nitrogen. The resulting N labeled proteins are then purified by immobilized metal affinity and their percentage estimated. In order to increase the yield of labeled proteins and cut down the cost of isotope labeled media, an alternative procedure primarily increases the cell mass using unlabeled media before introducing it in a minimal amount of labeled media. Another application of isotope labeling would be in measuring DNA synthesis, that is cell proliferation in vitro. Uses H-thymidine labeling to compare pattern of synthesis (or sequence) in cells. | 0 | Theoretical and Fundamental Chemistry |
The Song relocated their capital to Hangzhou and the Jin followed. The fighting that ensued would see the first proto-gun, the fire lance, in action – with earliest confirmed employment by Song dynasty forces against the Jin in 1132 during the siege of De'an (modern Anlu, Hubei), Most Chinese scholars reject the appearance of the fire lance prior to the Jin-Song wars, but its first appearance in art with from Dunhuang dates to the Five Dynasties and Ten Kingdoms period in the mid-10th century.
The siege of De'an marks an important transition and landmark in the history of gunpowder weapons as the fire medicine of the fire lances were described using a new word: "fire bomb medicine" (火炮藥), rather than simply "fire medicine." This could imply the use of a new more potent formula, or simply an acknowledgement of the specialized military application of gunpowder. Peter Lorge suggests that this "bomb powder" may have been corned, making it distinct from normal gunpowder. Evidence of gunpowder firecrackers also points to their appearance at roughly around the same time fire medicine was making its transition in the literary imagination.
Fire lances continued to be used as anti-personnel weapons into the Ming dynasty, and were even attached to battle carts on one situation in 1163. Song commander Wei Sheng constructed several hundred of these carts known as "at-your-desire-war-carts" (如意戰車), which contained fire lances protruding from protective covering on the sides. They were used to defend mobile trebuchets that hurled fire bombs. They were used as cavalry weapons by the 13th century. | 1 | Applied and Interdisciplinary Chemistry |
Cotransporters are capable of moving solutes either up or down gradients at rates of 1000 to 100000 molecules per second. They may act as channels or transporters, depending on conditions under which they are assayed. The movement occurs by binding to two molecules or ions at a time and using the gradient of one solute's concentration to force the other molecule or ion against its gradient. Some studies show that cotransporters can function as ion channels, contradicting the classical models. For instance the wheat HKT1 transporter shows two modes of transport by the same protein.
Cotransporters can be classified as antiporters and symporters. Both use electric potential and/or chemical gradients to move protons and ions against their concentration gradient. In plants the proton is considered a secondary substance and high proton concentration in the apoplast powers the inward movement of certain ions by symporters. A Proton gradient moves the ions into the vacuole by proton-sodium antiporter or the proton-calcium antiporter. In plants, sucrose transport is distributed throughout the plant by the proton-pump where the pump, as discussed above, creates a gradient of protons so that there are many more on one side of the membrane than the other. As the protons diffuse back across the membrane, the free energy liberated by this diffusion is used to co-transport sucrose. In mammals, glucose is transported through sodium dependent glucose transporters, which use energy in this process. Here, since both glucose and sodium are transported in the same direction across the membrane, they would be classified as symporters. The glucose transporter system was first hypothesized by Dr. Robert K. Crane in 1960, this is discussed later in the article. | 1 | Applied and Interdisciplinary Chemistry |
Effluent is defined by the United States Environmental Protection Agency (EPA) as "wastewater–treated or untreated–that flows out of a treatment plant, sewer, or industrial outfall. Generally refers to wastes discharged into surface waters". The Compact Oxford English Dictionary defines effluent as "liquid waste or sewage discharged into a river or the sea". Wastewater is not usually described as effluent while being recycled, re-used, or treated until it is released to surface water. Wastewater percolated or injected into groundwater may not be described as effluent if soil is assumed to perform treatment by filtration or ion exchange; although concealed flow through fractured bedrock, lava tubes, limestone caves, or gravel in ancient stream channels may allow relatively untreated wastewater to emerge as springs. | 1 | Applied and Interdisciplinary Chemistry |
In chemical nomenclature, the IUPAC nomenclature of organic chemistry is a method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). It is published in the Nomenclature of Organic Chemistry (informally called the [https://iupac.org/what-we-do/books/bluebook/ Blue Book]). Ideally, every possible organic compound should have a name from which an unambiguous structural formula can be created. There is also an IUPAC nomenclature of inorganic chemistry.
To avoid long and tedious names in normal communication, the official IUPAC naming recommendations are not always followed in practice, except when it is necessary to give an unambiguous and absolute definition to a compound. IUPAC names can sometimes be simpler than older names, as with ethanol, instead of ethyl alcohol. For relatively simple molecules they can be more easily understood than non-systematic names, which must be learnt or looked over. However, the common or trivial name is often substantially shorter and clearer, and so preferred. These non-systematic names are often derived from an original source of the compound. Also, very long names may be less clear than structural formulas. | 0 | Theoretical and Fundamental Chemistry |
Thermal engineering is a specialized sub-discipline of mechanical engineering that deals with the movement of heat energy and transfer. The energy can be transferred between two mediums or transformed into other forms of energy. A thermal engineer will have knowledge of thermodynamics and the process to convert generated energy from thermal sources into chemical, mechanical, or electrical energy. Many process plants use a wide variety of machines that utilize components that use heat transfer in some way. Many plants use heat exchangers in their operations. A thermal engineer must allow the proper amount of energy to be transferred for correct use. Too much and the components could fail, too little and the system will not function at all. Thermal engineers must have an understanding of economics and the components that they will be servicing or interacting with. Some components that a thermal engineer could work with include heat exchangers, heat sinks, bi-metals strips, radiators and many more. Some systems that require a thermal engineer include; Boilers, heat pumps, water pumps, engines, and more.
Part of being a thermal engineer is to improve a current system and make it more efficient than the current system. Many industries employ thermal engineers, some main ones are the automotive manufacturing industry, commercial construction, and Heating Ventilation and Cooling industry. Job opportunities for a thermal engineer are very broad and promising.
Thermal engineering may be practiced by mechanical engineers and chemical engineers.
One or more of the following disciplines may be involved in solving a particular thermal engineering problem: Thermodynamics, Fluid mechanics, Heat transfer, or
Mass transfer.
One branch of knowledge used frequently in thermal engineering is that of thermofluids. | 1 | Applied and Interdisciplinary Chemistry |
An empirical application of the principle was in widespread use on steam locomotives before its formal development as the injector, in the form of the arrangement of the blastpipe and chimney in the locomotive smokebox. The sketch on the right shows a cross section through a smokebox, rotated 90 degrees; it can be seen that the same components are present, albeit differently named, as in the generic diagram of an injector at the top of the article. Exhaust steam from the cylinders is directed through a nozzle on the end of the blastpipe, to reduce pressure inside the smokebox by entraining the flue gases from the boiler which are then ejected via the chimney. The effect is to increase the draught on the fire to a degree proportional to the rate of steam consumption, so that as more steam is used, more heat is generated from the fire and steam production is also increased. The effect was first noted by Richard Trevithick and subsequently developed empirically by the early locomotive engineers; Stephenson's Rocket made use of it, and this constitutes much of the reason for its notably improved performance in comparison with contemporary machines. | 1 | Applied and Interdisciplinary Chemistry |
The department offers undergraduate and graduate programs leading to the degree of chemical engineering:
* Bachelor of Science in Chemical Engineering (BS ChE) — five-year program leading to the understanding of transport processes, chemical engineering thermodynamics and their applications to unit operations design, thermodynamics and reaction kinetics.
* Master of Science in Chemical Engineering (MS ChE) — 24-unit coursework that includes core and elective courses related to chemical engineering and six units of master's thesis.
* Doctor of Philosophy in Chemical Engineering (PhD ChE) | 1 | Applied and Interdisciplinary Chemistry |
Fusion of a cyclooctyne to two aryl rings increases the reaction rate, and the cyclooctyne reagents of the Bertozzi group proceeded through a series of fusions that sought to increase the ring strain even further. DIBO (dibenzo cyclooctyne) was developed as a precursor to BARAC (biarylazacyclooctynone), although calculations had predicted that a single fused aryl ring would be optimal. Attempts to make a difluoro benzo cyclooctyne (DIFBO) were unsuccessful due to the instability of the compound.
The reason for the instability of DIFBO is that it is so reactive that it spontaneously trimerizes to form two asymmetric products that can be characterized by X-ray crystallography. To stabilize the DIFBO, it is trapped by forming a stable inclusion complex with β-cyclodextrin in aqueous media. This complex, formed with the β-cyclodextrin, can then be stored as a lyophilized powder. To obtain the free DIFBO, the lyophilized powder is dissociated with organic solvents to produce the free DIFBO for in situ kinetic and spectroscopic analysis.
Problems with DIFO with in vivo mouse studies illustrate the difficulty of producing bioorthogonal reactions. | 0 | Theoretical and Fundamental Chemistry |
Molybdenum is an essential element in most organisms; a 2008 research paper speculated that a scarcity of molybdenum in the Earth's early oceans may have strongly influenced the evolution of eukaryotic life (which includes all plants and animals).
At least 50 molybdenum-containing enzymes have been identified, mostly in bacteria. Those enzymes include aldehyde oxidase, sulfite oxidase and xanthine oxidase. With one exception, Mo in proteins is bound by molybdopterin to give the molybdenum cofactor. The only known exception is nitrogenase, which uses the FeMoco cofactor, which has the formula FeMoSC.
In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulating nitrogen, sulfur, and carbon. In some animals, and in humans, the oxidation of xanthine to uric acid, a process of purine catabolism, is catalyzed by xanthine oxidase, a molybdenum-containing enzyme. The activity of xanthine oxidase is directly proportional to the amount of molybdenum in the body. An extremely high concentration of molybdenum reverses the trend and can inhibit purine catabolism and other processes. Molybdenum concentration also affects protein synthesis, metabolism, and growth.
Mo is a component in most nitrogenases. Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin. Nitrogenases catalyze the production of ammonia from atmospheric nitrogen:
The biosynthesis of the FeMoco active site is highly complex.
Molybdate is transported in the body as MoO. | 1 | Applied and Interdisciplinary Chemistry |
Methoxy arachidonyl fluorophosphonate, commonly referred as MAFP, is an irreversible active site-directed enzyme inhibitor that inhibits nearly all serine hydrolases and serine proteases. It inhibits phospholipase A2 and fatty acid amide hydrolase with special potency, displaying IC values in the low-nanomolar range. In addition, it binds to the CB receptor in rat brain membrane preparations (IC = 20 nM), but does not appear to agonize or antagonize the receptor, though some related derivatives do show cannabinoid-like properties. | 1 | Applied and Interdisciplinary Chemistry |
For pure inflow, the implicit solution is given by
and the boundary conditions becomes
Pure inflow is possible only when all constants are real and the solution is given by
where is the complete elliptic integral of the first kind. | 1 | Applied and Interdisciplinary Chemistry |
In a colloidal suspension, particles will settle very slowly or not at all because the colloidal particles carry surface electrical charges that mutually repel each other. This surface charge is most commonly evaluated in terms of zeta potential, the electrical potential at the slipping plane. To induce coagulation, a coagulant (typically a metallic salt) with the opposite charge is added to the water to overcome the repulsive charge and "destabilize" the suspension. For example, the colloidal particles are negatively charged and alum is added as a coagulant to create positively charged ions. Once the repulsive charges have been neutralized (since opposite charges attract), van der Waals force will cause the particles to cling together (agglomerate) and form micro floc. | 1 | Applied and Interdisciplinary Chemistry |
Studies suggest dexmedetomidine for sedation in mechanically ventilated adults may reduce time to extubation and ICU stay.
Compared with other sedatives, some studies suggest dexmedetomidine may be associated with less delirium. However, this finding is not consistent across multiple studies. At the very least, when aggregating many study results together, use of dexmedetomidine appears to be associated with less neurocognitive dysfunction compared to other sedatives. Whether this observation has a beneficial psychological impact is unclear. From an economic perspective, dexmedetomidine is associated with lower ICU costs, largely due to a shorter time to extubation. | 0 | Theoretical and Fundamental Chemistry |
The phase speed of a cnoidal wave, both for the KdV and BBM equation, is given by:
In this formulation the phase speed is a function of wave height H and parameter m. However, for the determination of wave propagation for waves of infinitesimal height, it is necessary to determine the behaviour of the phase speed at constant wavelength λ in the limit that the parameter m approaches zero. This can be done by using the equation for the wavelength, which is different for the KdV and BBM equation:
Introducing the relative wavenumber κh:
and using the above equations for the phase speed and wavelength, the factor H / m in the phase speed can be replaced by κh and m. The resulting phase speeds are:
The limiting behaviour for small m can be analysed through the use of the Maclaurin series for K(m) and E(m), resulting in the following expression for the common factor in both formulas for c:
so in the limit m → 0, the factor γ → −. The limiting value of the phase speed for m ≪ 1 directly results.
The phase speeds for infinitesimal wave height, according to the cnoidal wave theories for the KdV equation and BBM equation, are
with κ = 2π / λ the wavenumber and κh the relative wavenumber. These phase speeds are in full agreement with the result obtained by directly searching for sine-wave solutions of the linearised KdV and BBM equations. As is evident from these equations, the linearised BBM equation has a positive phase speed for all κh. On the other hand, the phase speed of the linearised KdV equation changes sign for short waves with κh > . This is in conflict with the derivation of the KdV equation as a one-way wave equation. | 1 | Applied and Interdisciplinary Chemistry |
In fluid dynamics, the Keulegan–Carpenter number, also called the period number, is a dimensionless quantity describing the relative importance of the drag forces over inertia forces for bluff objects in an oscillatory fluid flow. Or similarly, for objects that oscillate in a fluid at rest. For small Keulegan–Carpenter number inertia dominates, while for large numbers the (turbulence) drag forces are important.
The Keulegan–Carpenter number K is defined as:
where:
*V is the amplitude of the flow velocity oscillation (or the amplitude of the object's velocity, in case of an oscillating object),
*T is the period of the oscillation, and
*L is a characteristic length scale of the object, for instance the diameter for a cylinder under wave loading.
The Keulegan–Carpenter number is named after Garbis H. Keulegan (1890–1989) and Lloyd H. Carpenter.
A closely related parameter, also often used for sediment transport under water waves, is the displacement parameter δ:
with A the excursion amplitude of fluid particles in oscillatory flow and L a characteristic diameter of the sediment material. For sinusoidal motion of the fluid, A is related to V and T as A = VT/(2π), and:
The Keulegan–Carpenter number can be directly related to the Navier–Stokes equations, by looking at characteristic scales for the acceleration terms:
*convective acceleration:
*local acceleration:
Dividing these two acceleration scales gives the Keulegan–Carpenter number.
A somewhat similar parameter is the Strouhal number, in form equal to the reciprocal of the Keulegan–Carpenter number. The Strouhal number gives the vortex shedding frequency resulting from placing an object in a steady flow, so it describes the flow unsteadiness as a result of an instability of the flow downstream of the object. Conversely, the Keulegan–Carpenter number is related to the oscillation frequency of an unsteady flow into which the object is placed. | 1 | Applied and Interdisciplinary Chemistry |
Studies have demonstrated that the oxidative stress generated by arsenic may disrupt the signal transduction pathways of the nuclear transcriptional factors PPARs, AP-1, and NF-κB, as well as the pro-inflammatory cytokines IL-8 and TNF-α. The interference of oxidative stress with signal transduction pathways may affect physiological processes associated with cell growth, metabolic syndrome X, glucose homeostasis, lipid metabolism, obesity, insulin resistance, inflammation, and diabetes-2. Recent scientific evidence has elucidated the physiological roles of the PPARs in the ω- hydroxylation of fatty acids and the inhibition of pro-inflammatory transcription factors (NF-κB and AP-1), pro-inflammatory cytokines (IL-1, -6, -8, -12, and TNF-α), cell4 adhesion molecules (ICAM-1 and VCAM-1), inducible nitric oxide synthase, proinflammatory nitric oxide (NO), and anti-apoptotic factors.
Epidemiological studies have suggested a correlation between chronic consumption of drinking water contaminated with arsenic and the incidence of type 2 diabetes. The human liver after exposure to therapeutic drugs may exhibit hepatic non-cirrhotic portal hypertension, fibrosis, and cirrhosis. However, the literature provides insufficient scientific evidence to show cause and effect between arsenic and the onset of diabetes mellitus Type 2. | 1 | Applied and Interdisciplinary Chemistry |
High-content screening technology is mainly based on automated digital microscopy and flow cytometry, in combination with IT-systems for the analysis and storage of the data.
“High-content” or visual biology technology has two purposes, first to acquire spatially or temporally resolved information on an event and second to automatically quantify it. Spatially resolved instruments are typically automated microscopes, and temporal resolution still requires some form of fluorescence measurement in most cases. This means that a lot of HCS instruments are (fluorescence) microscopes that are connected to some form of image analysis package. These take care of all the steps in taking fluorescent images of cells and provide rapid, automated and unbiased assessment of experiments.
HCS instruments on the market today can be separated based on an array of specifications that significantly influence the instruments versatility and overall cost. These include speed, a live cell chamber that includes temperature and control (some also have humidity control for longer term live cell imaging), a built in pipettor or injector for fast kinetic assays, and additional imaging modes such as confocal, bright field, phase contrast and FRET. One of the most incisive difference is whether the instruments are optical confocal or not. Confocal microscopy summarizes as imaging/resolving a thin slice through an object and rejecting out of focus light that comes from outside this slice. Confocal imaging enables higher image signal to noise and higher resolution than the more commonly applied epi-fluorescence microscopy. Depending on the instrument confocality is achieved via laser scanning, a single spinning disk with pinholes or slits, a dual spinning disk, or a virtual slit. There are trade offs of sensitivity, resolution, speed, photo-toxicity, photo-bleaching, instrument complexity, and price between these various confocal techniques.
What all instruments share is the ability to take, store and interpret images automatically and integrate into large robotic cell/medium handling platforms. | 1 | Applied and Interdisciplinary Chemistry |
The general form can be specialized for full pipe flows. Taking the general form
and exponentiating each side by gives (rounding exponents to 3–4 decimals)
Rearranging gives
The flow rate , so
The hydraulic radius (which is different from the geometric radius ) for a full pipe of geometric diameter is ; the pipe's cross sectional area is , so | 1 | Applied and Interdisciplinary Chemistry |
Electrophilic amination is a chemical process involving the formation of a carbon–nitrogen bond through the reaction of a nucleophilic carbanion with an electrophilic source of nitrogen. | 0 | Theoretical and Fundamental Chemistry |
The amg unit for number density can be converted to the SI unit mol/m by the formula
where ≘ indicates correspondence, since the SI unit is of molar concentration and not number density.
The conversion factor (44.615...) is the Loschmidt number divided by the Avogadro constant.
The number density of an ideal gas at pressure p and temperature T can be calculated as
where T = 273.15 K, and p = 101.325 kPa (STP before 1982). | 0 | Theoretical and Fundamental Chemistry |
In building services engineering and HVAC, a bell mouth is a tapered expanding or reducing opening in the end of a ventilation duct, so named because the taper can resemble that of a bell shape. They are primarily designed and used for return air or extract air purposes within building ventilation systems, more commonly located within ceiling voids or other similar plenum. The bellmouth cross-sectional area is normally double that of the duct area so that the air velocity entering the bellmouth is low (to reduce noise, turbulence and pressure drop), and gradually increases to the normal design velocity of the ductwork. The angle of the bellmouth is normally tapered at about 45° as a balance between keeping the bellmouth short without causing too much turbulence or excessive pressure drop. Bellmouths can be manufactured to suit either circular or rectangular ductwork sections.
The bell-mouth shape allows the maximum amount of air to be drawn into the duct with minimum loss.
A bell-mouth inlet duct is a form of convergent inlet air duct used to direct air into the inlet of a gas turbine engine. The area of a convergent duct gets smaller as the air flows into the engine. A bell-mouth inlet duct is extremely efficient and is used where there is little ram pressure available to force the air into the engine. Bell-mouth ducts are used in engine test cells and on engines installed in helicopters.
Examples of the effects of different shape (bellmouth)inlets are shown in the referenced "Good Fabs" article | 1 | Applied and Interdisciplinary Chemistry |
In thermodynamics, a temperature–entropy (T–s) diagram is a thermodynamic diagram used to visualize changes to temperature () and specific entropy () during a thermodynamic process or cycle as the graph of a curve. It is a useful and common tool, particularly because it helps to visualize the heat transfer during a process. For reversible (ideal) processes, the area under the T–s curve of a process is the heat transferred to the system during that process.
Working fluids are often categorized on the basis of the shape of their T–s diagram.
An isentropic process is depicted as a vertical line on a T–s diagram, whereas an isothermal process is a horizontal line. | 0 | Theoretical and Fundamental Chemistry |
Spectrochemistry is the application of spectroscopy in several fields of chemistry. It includes analysis of [https://imagine.gsfc.nasa.gov/science/toolbox/spectra1.html ] in chemical terms, and use of spectra to derive the structure of chemical compounds, and also to qualitatively and quantitively analyze their presence in the sample. It is a method of chemical analysis that relies on the measurement of [https://www.qrg.northwestern.edu/projects/vss/docs/communications/1-what-is-wavelength.html ] and intensity of . | 0 | Theoretical and Fundamental Chemistry |
Density functional theory seeks to solve for an approximate form of the electronic density of a system. In general, atoms are split into ionic cores and valence electrons. The ionic cores (nuclei plus non-bonding electrons) are assumed to be stable and are treated as a single object. Each valence electron is treated separately. Thus, for example, a Lithium atom is treated as two bodies – Li+ and e- – while oxygen is treated as three bodies, namely O and 2e.
The “true” ground state of a crystal system is generally unsolvable. However, the variational theorem assures us that any guess as to the electronic state function of a system will overestimate the ground state energy. Thus, by beginning with a suitably parametrized guess and minimizing the energy with respect to each of those parameters, an extremely accurate prediction may be made. The question as to what one's initial guess should be is a topic of active research.
In the large majority of crystal systems, electronic relaxation times are orders of magnitude shorter than ionic relaxation times. Thus, an iterative scheme is adopted. First, the ions are considered fixed and the electronic state is relaxed by considering the ionic and electron-electron pair potentials. Next, the electronic states are considered fixed and the ions are allowed to move under the influence of the electronic and ion-ion pair potentials. When the decrease in energy between two iterative steps is sufficiently small, the structure of the crystal is considered solved. | 0 | Theoretical and Fundamental Chemistry |
Chemically, levocetirizine is the active levorotary enantiomer of cetirizine, also called the l-enantiomer of cetirizine. It is a member of the diphenylmethylpiperazine group of antihistamines. | 0 | Theoretical and Fundamental Chemistry |
Erosion corrosion, also known as impingement damage, is the combined effect of corrosion and erosion caused by rapid flowing turbulent water. It is probably the second most common cause of copper tube failures behind Type 1 pitting which is also known as Cold Water Pitting of Copper Tube.
Copper Water Tubes
Copper tubes have been used to distribute drinking water within buildings for many years, and hundreds of miles are installed throughout Europe every year. The long life of copper when exposed to natural waters is a result of its thermodynamic stability, its high resistance to reacting with the environment, and the formation of insoluble corrosion products that insulate the metal from the environment. The corrosion rate of copper in most drinkable waters is less than 2.5 µm/year, at this rate a 15 mm tube with a wall thickness of 0.7 mm would last for about 280 years. In some soft waters the general corrosion rate may increase to 12.5 µm/year, but even at this rate it would take over 50 years to perforate the same tube. | 1 | Applied and Interdisciplinary Chemistry |
Pertechnetate is actively accumulated and secreted by the mucoid cells of the gastric mucosa, and therefore, technetate(VII) radiolabeled with Tc99m is injected into the body when looking for ectopic gastric tissue as is found in a Meckels diverticulum with Meckels Scans. | 0 | Theoretical and Fundamental Chemistry |
Friable macro- or micro-scale solid particles can be ground in a ball mill, a planetary ball mill, or other size-reducing mechanism until enough of them are in the nanoscale size range. The resulting powder can be air classified to extract the nanoparticles. | 0 | Theoretical and Fundamental Chemistry |
Gibbs paradox arises when entropy is calculated using an dimensional phase space, where is also the number of particles in the gas. These particles are spatially confined to the one-dimensional interval . The volume of the surface of fixed energy is
The subscripts on are used to define the state variables and will be discussed later, when it is argued that the number of particles, lacks full status as a state variable in this calculation. The integral over configuration space is . As indicated by the underbrace, the integral over velocity space is restricted to the "surface area" of the dimensional hypersphere of radius , and is therefore equal to the "area" of that hypersurface. Thus
After approximating the factorial and dropping the small terms, we obtain
In the second expression, the term was subtracted and added, using the fact that . This was done to highlight exactly how the "entropy" defined here fails to be an extensive property of matter. The first two terms are extensive: if the volume of the system doubles, but gets filled with the same density of particles with the same energy, then each of these terms doubles. But the third term is neither extensive nor intensive and is therefore wrong.
The arbitrary constant has been added because entropy can usually be viewed as being defined up to an arbitrary additive constant. This is especially necessary when entropy is defined as the logarithm of a phase space volume measured in units of momentum-position. Any change in how these units are defined will add or subtract a constant from the value of the entropy. | 0 | Theoretical and Fundamental Chemistry |
* 18 August 1997, Order of Princess Olga, 3rd class, for outstanding personal contribution to the spiritual revival of Ukraine, solving the problems of family, women and children, professional and social activities for the benefit of the Ukrainian people
* 18 November 2009, Order of Liberty, for outstanding personal contribution to the defense of the national idea, the formation and development of the independent Ukrainian state, and active political and social activities | 1 | Applied and Interdisciplinary Chemistry |
Dilute aqueous zinc chloride was used as a disinfectant under the name "Burnett's Disinfecting Fluid".
From 1839 Sir William Burnett promoted its use as a disinfectant as well as a wood preservative. The Royal Navy conducted trials into its use as a disinfectant in the late 1840s, including during the cholera epidemic of 1849; and at the same time experiments were conducted into its preservative properties as applicable to the shipbuilding and railway industries. Burnett had some commercial success with his eponymous fluid. Following his death however, its use was largely superseded by that of carbolic acid and other proprietary products. | 0 | Theoretical and Fundamental Chemistry |
The magnetism of the early full-Heusler compound CuMnAl varies considerably with heat treatment and composition. It has a room-temperature saturation induction of around 8,000 gauss, which exceeds that of the element nickel (around 6100 gauss) but is smaller than that of iron (around 21500 gauss). For early studies see. In 1934, Bradley and Rogers showed that the room-temperature ferromagnetic phase was a fully ordered structure of the L2 Strukturbericht type. This has a primitive cubic lattice of copper atoms with alternate cells body-centered by manganese and aluminium. The lattice parameter is 5.95 Å. The molten alloy has a solidus temperature of about 910 °C. As it is cooled below this temperature, it transforms into disordered, solid, body-centered cubic beta-phase. Below 750 °C, a B2 ordered lattice forms with a primitive cubic copper lattice, which is body-centered by a disordered manganese-aluminium sublattice. Cooling below 610 °C causes further ordering of the manganese and aluminium sub-lattice to the L2 form. In non-stoichiometric alloys, the temperatures of ordering decrease, and the range of anealing temperatures, where the alloy does not form microprecipitates, becomes smaller than for the stoichiometric material.
Oxley found a value of 357 °C for the Curie temperature, below which the compound becomes ferromagnetic. Neutron diffraction and other techniques have shown that a magnetic moment of around 3.7 Bohr magnetons resides almost solely on the manganese atoms. As these atoms are 4.2 Å apart, the exchange interaction, which aligns the spins, is likely indirect and is mediated through conduction electrons or the aluminium and copper atoms.
Electron microscopy studies demonstrated that thermal antiphase boundaries (APBs) form during cooling through the ordering temperatures, as ordered domains nucleate at different centers within the crystal lattice and are often out of step with each other where they meet. The anti-phase domains grow as the alloy is annealed. There are two types of APBs corresponding to the B2 and L2 types of ordering. APBs also form between dislocations if the alloy is deformed. At the APB the manganese atoms will be closer than in the bulk of the alloy and, for non-stoichiometric alloys with an excess of copper (e.g. CuMnAl), an antiferromagnetic layer forms on every thermal APB. These antiferromagnetic layers completely supersede the normal magnetic domain structure and stay with the APBs if they are grown by annealing the alloy. This significantly modifies the magnetic properties of the non-stoichiometric alloy relative to the stoichiometric alloy which has a normal domain structure. Presumably this phenomenon is related to the fact that pure manganese is an antiferromagnet although it is not clear why the effect is not observed in the stoichiometric alloy. Similar effects occur at APBs in the ferromagnetic alloy MnAl at its stoichiometric composition.
Some Heusler compounds also exhibit properties of materials known as ferromagnetic shape-memory alloys. These are generally composed of nickel, manganese and gallium and can change their length by up to 10% in a magnetic field. | 1 | Applied and Interdisciplinary Chemistry |
Ketenes are generally very reactive, and participate in various cycloadditions. One important process is the dimerization to give propiolactones. A specific example is the dimerization of the ketene of stearic acid to afford alkyl ketene dimers, which are widely used in the paper industry. AKD's react with the hydroxyl groups on the cellulose via esterification reaction.
They will also undergo [2+2] cycloaddition reactions with electron-rich alkynes to form cyclobutenones, or carbonyl groups to form beta-lactones. With imines, beta-lactams are formed. This is the Staudinger synthesis, a facile route to this important class of compounds. With acetone, ketene reacts to give isopropenyl acetate.
A variety of hydroxylic compounds can add as nucleophiles, forming either enol or ester products. As examples, a water molecule easily adds to ketene to give 1,1-dihydroxyethene and acetic anhydride is produced by the reaction of acetic acid with ketene. Reactions between diols () and bis-ketenes () yield polyesters with a repeat unit of ().
Ethyl acetoacetate, an important starting material in organic synthesis, can be prepared using a diketene in reaction with ethanol. They directly form ethyl acetoacetate, and the yield is high when carried out under controlled circumstances; this method is therefore used industrially. | 0 | Theoretical and Fundamental Chemistry |
Phosphatidylinositol-4-phosphate (PtdIns4P, PI-4-P, PI4P, or PIP) is a precursor of phosphatidylinositol (4,5)-bisphosphate. PtdIns4P is prevalent in the membrane of the Golgi apparatus.
In the Golgi apparatus, PtdIns4P binds to the GTP-binding protein ARF and to effector proteins, including four-phosphate-adaptor protein 1 and 2 (PLEKHA3 and PLEKHA8). This three molecule complex recruits proteins that need to be carried to the cell membrane.
There is now evidence that PI-4-P is capable of deforming lipid systems into tightly curved assemblies, this is consistent with similar behaviour observed in phosphatidylinositol. | 1 | Applied and Interdisciplinary Chemistry |
*1994 — Tanner Award for Teaching Excellence
*1995 — NSF Special Creativity Award in Organophosphorus Chemistry
*1998 — ACS Award for Encouraging Disadvantaged Students into Careers in the Chemical Sciences
*Chancellor's Award for Excellence in Undergraduate Education
*Howard University Outstanding Achievement Award | 0 | Theoretical and Fundamental Chemistry |
* In the Markó–Lam deoxygenation, an alcohol could be almost instantaneously deoxygenated by electroreducing its toluate ester.
* In concept, adiponitrile is prepared from dimerizing acrylonitrile:
:In practice,the cathodic hydrodimerization of activated olefins is applied industrially in the synthesis of adiponitrile from two equivalents of acrylonitrile :
* The cathodic reduction of arene compounds to the 1,4-dihydro derivatives is similar to a Birch reduction. Examples from industry are the reduction of phthalic acid:
and the reduction of 2-methoxynaphthalene:
* The Tafel rearrangement, named for Julius Tafel, was at one time an important method for the synthesis of certain hydrocarbons from alkylated ethyl acetoacetate, a reaction accompanied by the rearrangement reaction of the alkyl group:
* The cathodic reduction of a nitrile to a primary amine in a divided cell; the cathodic reduction of benzyl cyanide to phenethylamine is shown:
* Cathodic reduction of a nitroalkene can give the oxime in good yield. At higher negative reduction potentials, the nitroalkene can be reduced further, giving the primary amine but with lower yield.
* Azobenzene is prepared in industrial electrosynthesis using nitrobenzene.
* An electrochemical carboxylation of a para-isobutyl benzyl chloride to Ibuprofen is promoted under supercritical carbon dioxide.
* Cathodic reduction of a carboxylic acid (oxalic acid) to an aldehyde (glyoxylic acid, shows as the rare aldehyde form) in a divided cell:
* Originally phenylpropanoic acid could be prepared from reduction of cinnamic acid by electrolysis.
* An electrocatalysis by a copper complex helps reduce carbon dioxide to oxalic acid; this conversion uses carbon dioxide as a feedstock to generate oxalic acid.
* It has been reported that formate can be formed by the electrochemical reduction of (in the form of bicarbonate) at a lead cathode at pH 8.6:
or
If the feed is and oxygen is evolved at the anode, the total reaction is: | 0 | Theoretical and Fundamental Chemistry |
In decay, the weak interaction converts an atomic nucleus into a nucleus with atomic number increased by one, while emitting an electron () and an electron antineutrino (). decay generally occurs in neutron-rich nuclei. The generic equation is:
where and are the mass number and atomic number of the decaying nucleus, and X and X′ are the initial and final elements, respectively.
Another example is when the free neutron () decays by decay into a proton ():
At the fundamental level (as depicted in the Feynman diagram on the right), this is caused by the conversion of the negatively charged () down quark to the positively charged () up quark by emission of a boson; the boson subsequently decays into an electron and an electron antineutrino: | 0 | Theoretical and Fundamental Chemistry |
Diatomic molecules () are molecules composed of only two atoms, of the same or different chemical elements. If a diatomic molecule consists of two atoms of the same element, such as hydrogen () or oxygen (), then it is said to be homonuclear. Otherwise, if a diatomic molecule consists of two different atoms, such as carbon monoxide () or nitric oxide (), the molecule is said to be heteronuclear. The bond in a homonuclear diatomic molecule is non-polar.
The only chemical elements that form stable homonuclear diatomic molecules at standard temperature and pressure (STP) (or at typical laboratory conditions of 1 bar and 25 °C) are the gases hydrogen (), nitrogen (), oxygen (), fluorine (), and chlorine (), and the liquid bromine ().
The noble gases (helium, neon, argon, krypton, xenon, and radon) are also gases at STP, but they are monatomic. The homonuclear diatomic gases and noble gases together are called "elemental gases" or "molecular gases", to distinguish them from other gases that are chemical compounds.
At slightly elevated temperatures, the halogens bromine () and iodine () also form diatomic gases. All halogens have been observed as diatomic molecules, except for astatine and tennessine, which are uncertain.
Other elements form diatomic molecules when evaporated, but these diatomic species repolymerize when cooled. Heating ("cracking") elemental phosphorus gives diphosphorus (). Sulfur vapor is mostly disulfur (). Dilithium () and disodium () are known in the gas phase. Ditungsten () and dimolybdenum () form with sextuple bonds in the gas phase. Dirubidium () is diatomic. | 0 | Theoretical and Fundamental Chemistry |
Using the Bessemer process, it took between 10 and 20 minutes to convert three to five tons of iron into steel — it would previously take at least a full day of heating, stirring and reheating to achieve this. | 1 | Applied and Interdisciplinary Chemistry |
Many peroxides are used as a radical initiators, e.g., to enable polymerization of acrylates. Industrial resins based on acrylic and/or methacrylic acid esters are invariably produced by radical polymerization with organic peroxides at elevated temperatures. The polymerization rate is adjusted by suitable choice of temperature and type of peroxide.
Methyl ethyl ketone peroxide, benzoyl peroxide and to a smaller degree acetone peroxide are used as initiators for radical polymerization of some thermosets, e.g. unsaturated polyester and vinyl ester resins, often encountered when making fiberglass or carbon fiber composites (CFRP), with examples including boats, RV units, bath tubs, pools, sporting equipment, wind turbine blades, and a variety of industrial applications.
Benzoyl peroxide, peroxyesters/peroxyketals, and alkylperoxy monocarbonates are used in production of polystyrene, expanded polystyrene, and High Impact Polystyrene, and benzoyl peroxide is utilized for many acrylate based adhesive applications.
Thermoplastic production techniques for many industrial polymerization applications include processes which are carried out in bulk, solution, or suspension type batches. Relevant polymers include:
polyvinyl chloride (PVC),
low-density polyethylene (LDPE),
high-density polyethylene (HDPE),
polymethyl methacrylate (PMMA), Polystyrene, and
Polycarbonates. | 0 | Theoretical and Fundamental Chemistry |
Carbon satellites can be used to obtain structural information, which is not available by looking at the main peaks in the NMR spectrum.
This usually occurs when the purely C compound is symmetrical but where the 1% of the compound which has a C atom in it is no longer symmetrical.
For example, it is not possible to tell whether stilbene (Ph-CH=CH-Ph) has a cis- or trans- double bond just by examining at the main peaks in the H NMR spectrum. The =CH- proton does not couple to the adjacent =CH- proton as the molecule is symmetrical. However, 1% of the stilbene molecules will have a C atom on one of these double bond carbons (i.e. Ph-CH=CH-Ph). In this situation, the proton adjacent to C atom will couple to the C atom to give a wide doublet. Also, as this molecule is no longer symmetric the C= proton will now couple to the adjacent C= proton, causing a further doubleting. Thus, this additional coupling (additional to the C coupling) is diagnostic of the type of double bond, and will allow one to determine if the stilbene molecule has a cis- or trans- configuration i.e. by examining the size of the diagnostic J coupling constant from -CH=CH- bond. Thus, only a single 1H NMR spectrum is needed, albeit with close inspection of the satellite peaks, rather than any further complex NMR or derivative chemical experiments.
The same would be seen for 1,2-Dichloroethene. | 0 | Theoretical and Fundamental Chemistry |
In this step, two tagged adapters are ligated from 3’-dT-tails to 3’-dA-tails on both sides of double-stranded DNA library fragments. This process results in double-stranded library fragments that contain two random tags (α and β) on each side that are the reverse complement of each other (Figure 1 and 2). The "DNA: adapter" ratio is crucial in determining the success of ligation. | 1 | Applied and Interdisciplinary Chemistry |
1-Tridecanol is an alcohol with the formula CHOH. It is a colorless fatty alcohol that turns white when solid. 1-Tridecanol usually occurs as a mixture of different isomeric to compounds such as 2-tridecanol, 3-tridecanol, 4-tridecanol, 5-tridecanol, 6-tridecanol, and isotridecanol. | 0 | Theoretical and Fundamental Chemistry |
* Kyoto Encyclopedia of Genes and Genomes ([http://www.kegg.jp/ KEGG]): a bioinformatics database containing information on genes, proteins, reactions, and pathways. The ‘KEGG Organisms’ section, which is divided into eukaryotes and prokaryotes, encompasses many organisms for which gene and DNA information can be searched by typing in the enzyme of choice.
* BioCyc, EcoCyc, and MetaCyc: [http://biocyc.org/ BioCyc] Is a collection of 3,000 pathway/genome databases (as of Oct 2013), with each database dedicated to one organism. For example, [http://ecocyc.org/ EcoCyc] is a highly detailed bioinformatics database on the genome and metabolic reconstruction of Escherichia coli, including thorough descriptions of E. coli signaling pathways and regulatory network. The EcoCyc database can serve as a paradigm and model for any reconstruction. Additionally, [http://biocyc.org/metacyc/index.shtml MetaCyc], an encyclopedia of experimentally defined metabolic pathways and enzymes, contains 2,100 metabolic pathways and 11,400 metabolic reactions (Oct 2013).
* [http://enzyme.expasy.org/ ENZYME]: An enzyme nomenclature database (part of the ExPASy proteonomics server of the Swiss Institute of Bioinformatics). After searching for a particular enzyme on the database, this resource gives you the reaction that is catalyzed. ENZYME has direct links to other gene/enzyme/literature databases such as KEGG, BRENDA, and PUBMED.
* [http://www.brenda-enzymes.info/ BRENDA]: A comprehensive enzyme database that allows for an enzyme to be searched by name, EC number, or organism.
* [http://bigg.ucsd.edu/ BiGG]: A knowledge base of biochemically, genetically, and genomically structured genome-scale metabolic network reconstructions.
* [https://web.archive.org/web/20120304065541/http://www.bioinformatics.leeds.ac.uk/metatiger/ metaTIGER]: Is a collection of metabolic profiles and phylogenomic information on a taxonomically diverse range of eukaryotes which provides novel facilities for viewing and comparing the metabolic profiles between organisms. | 1 | Applied and Interdisciplinary Chemistry |
In high-energy nuclear physics, strangeness production in relativistic heavy-ion collisions is a signature and diagnostic tool of quark–gluon plasma (QGP) formation and properties. Unlike up and down quarks, from which everyday matter is made, heavier quark flavors such as strange and charm typically approach chemical equilibrium in a dynamic evolution process. QGP (also known as quark matter) is an interacting localized assembly of quarks and gluons at thermal (kinetic) and not necessarily chemical (abundance) equilibrium. The word plasma signals that color charged particles (quarks and/or gluons) are able to move in the volume occupied by the plasma. The abundance of strange quarks is formed in pair-production processes in collisions between constituents of the plasma, creating the chemical abundance equilibrium. The dominant mechanism of production involves gluons only present when matter has become a quark–gluon plasma. When quark–gluon plasma disassembles into hadrons in a breakup process, the high availability of strange antiquarks helps to produce antimatter containing multiple strange quarks, which is otherwise rarely made. Similar considerations are at present made for the heavier charm flavor, which is made at the beginning of the collision process in the first interactions and is only abundant in the high-energy environments of CERN's Large Hadron Collider. | 0 | Theoretical and Fundamental Chemistry |
A definition of thermodynamic entropy can be based entirely on certain properties of the relation of adiabatic accessibility that are taken as axioms in the Lieb-Yngvason approach. In the following list of properties of the operator, a system is represented by a capital letter, e.g. X, Y or Z. A system X whose extensive parameters are multiplied by is written . (e.g. for a simple gas, this would mean twice the amount of gas in twice the volume, at the same pressure.) A system consisting of two subsystems X and Y is written (X,Y). If and are both true, then each system can access the other and the transformation taking one into the other is reversible. This is an equivalence relationship written . Otherwise, it is irreversible. Adiabatic accessibility has the following properties:
*Reflexivity:
*Transitivity: If and then
*Consistency: if and then
*Scaling Invariance: if and then
*Splitting and Recombination: for all
*Stability: if then
The entropy has the property that if and only if and if and only if in accord with the Second Law. If we choose two states and such that and assign entropies 0 and 1 respectively to them, then the entropy of a state X where is defined as: | 0 | Theoretical and Fundamental Chemistry |
In a delay line detector the electrons are accelerated to 500 eV between the back of the last MCP and a grid. They then fly for 5 mm and are dispersed over an area of 2 mm. A grid follows. Each element has a diameter of 1 mm and consists of an electrostatic lens focusing arriving electrons through a 30 µm hole of a grounded sheet of aluminium. Behind that, a cylinder of the same size follows. The electron cloud induces a 300 ps negative pulse when entering the cylinder and a positive when leaving. After that another sheet, a second cylinder follows, and a last sheet follows. Effectively the cylinders are fused into the center-conductor of a stripline. The sheets minimize cross talk between the layers and adjacent lines in the same layer, which would lead to signal dispersion and ringing. These striplines meander across the anode to connect all cylinders, to offer each cylinder 50 Ω impedance, and to generate a position dependent delay. Because the turns in the stripline adversely affect the signal quality their number is limited and for higher resolutions multiple independent striplines are needed. At both ends the meanders are connected to detector electronics. These electronics convert the measured delays into X- (first layer) and Y-coordinates (second layer). Sometimes a hexagonal grid and 3 coordinates are used. This redundancy reduces the dead space-time by reducing the maximum travel distance and thus the maximum delay, allowing for faster measurements. The microchannel plate detector must not operate over around 60 degree Celsius, otherwise it will degrade rapidly, bakeout without voltage has no influence. | 0 | Theoretical and Fundamental Chemistry |
Options for topical formulation include:
* Cream – Emulsion of oil and water in approximately equal proportions. Penetrates stratum corneum outer layers of skin well.
* Ointment – Combines oil (80%) and water (20%). Effective barrier against moisture loss.
* Gel – Liquefies upon contact with the skin.
* Paste – Combines three agents – oil, water, and powder; an ointment in which a powder is suspended.
* Powder – A finely subdivided solid substance. | 1 | Applied and Interdisciplinary Chemistry |
A problem with transition state analogue selection approach is that catalytic activity is not a screening criterion. TSAs do not necessarily represent real transition states and so a catalyst obtained from screening could just be the best receptor for a TSA but is not necessarily the best catalyst. To circumvent this problem, catalytic activity needs to be measured directly and also quickly. To develop a high-throughput screen, substrates could be designed to change color or release a fluorescent product upon reaction. For example, Crabtree and coworkers utilized this method in screening for a hydrosylation catalysts for alkene and imine. Unfortunately the prerequisite for such substrates narrow down the range of reactions for study. | 0 | Theoretical and Fundamental Chemistry |
Viral RNA modifications use the same machinery as cellular RNA. This involves the use of "writer" and "reader" complexes. The writer complex contains the enzyme methyl transferase-like 3 (METTL3) and its cofactors like METTL14, WTP, KIAA1492 and RBM15/RBM15B which adds the mA modification in the nucleus. The family of proteins known as the YTH like YTHDC1 and YTHDC2 are capable of detecting these modifications within the nucleus. In the cytoplasm, the reading duties are carried out by YTHDF1, YTHDF2, and YTHDF3. The proteins ALKBH5 and FTO remove the mA modification, functionally serving as erasers, with the latter having a more restricted selectivity depending on the position of the modification. | 1 | Applied and Interdisciplinary Chemistry |
In 1985, MIM commissioned Jameson to undertake a project to improve the sparger design for flotation columns. Instead, he developed the concept of using a jet in a downcomer to create the bubbles and eliminate the need for a sparger in conventional flotation columns.
The concept of the Cell followed when further investigations showed that most of the bubble–particle interactions were occurring in the downcomer, rendering unnecessary the collection zone of flotation columns. The idea of the downcomer and short separation tank was developed and a provisional patent application was lodged in 1986. This patent was later assigned to TUNRA Limited ("TUNRA"), the technology transfer company of the University of Newcastle that is now known as "Newcastle Innovation".
A pilot two tonne per hour (t/h) Jameson Cell with a 100 mm downcomer and using an orifice plate to create the jet was tested in MIM's lead–zinc concentrator. Subsequently, in 1988, MIM tested the flotation of a stream of fine lead-bearing particles in a conventional mechanical flotation cell, a conventional column and the Jameson Cell. The Cell gave the best recoveries. This was thought to be a combination of the short residence time of the particles in the Cell and the fact that the hydrophobicity of the lead particles decreased over time.
As a result of this work, in 1989 MIM ordered four full-scale Cells, two for the Mount Isa lead–zinc concentrator and another two for the new Hilton lead–zinc concentrator to be built at the Hilton Mine, located about 20 kilometers north of Mount Isa. The Mount Isa cells had diameters of 1.9 m, with three downcomers each, while those at Hilton were 1.3 m in diameter and had two downcomers each. | 1 | Applied and Interdisciplinary Chemistry |
The famous controversy between Pasteur and Liebig over the nature of alcoholic fermentation was uncovered by Eduard Büchner, a German chemist and zymologist. Influenced by his brother Hans, who became the famous bacteriologist, Büchner developed an interest in the fermentation process in which yeast breaks down sugar into alcohol and carbon dioxide. He published his first paper in 1885 which revealed that fermentation could occur in the presence of oxygen, a conclusion contrary to the view held by Louis Pasteur.
By 1893, Büchner was fully involved in seeking the active agent of fermentation. He obtained pure samples of the inner fluid of yeast cells by pulverizing yeast within a mixture of sand and diatomaceous earth, then squeezing the mixture through a canvas filter. This process avoided using solvents and high temperatures which had foiled previous investigations. He assumed that the collected fluid was incapable of producing fermentation because the yeast cells were dead. However, when he attempted to preserve the fluid in concentrated sugar, he was startled to observe carbon dioxide being released, a sign that fermentation was taking place. Büchner hypothesized that the fermentation was caused by an enzyme which he named zymase. His findings that fermentation was the result of chemical process both inside and outside cells, were published in 1897. | 1 | Applied and Interdisciplinary Chemistry |
* In accordance with the Decree of the Presidium of the Supreme Soviet of USSR on 20 October 1956 the Moscow Institute of Fine Chemical Technology named after M. V. Lomonosov awarded the medal "For the development of virgin land";
* In accordance with the Decree of the Presidium of the Supreme Soviet of USSR on 11 February 1971 for services on the training of specialists for the national economy and the development of research Moscow Institute of Fine Chemical Technology named after M. V. Lomonosov awarded the Order of Red Banner of Labour. | 1 | Applied and Interdisciplinary Chemistry |
The quantity is commonly referred to as the "generalized Rabi frequency." For cases in which , Rabi flopping actually occurs at this frequency, where is the detuning, a measure of how far the light is off-resonance relative to the transition. For instance, examining the above animation at an offset frequency of ±1.73, one can see that during the 1/2 Rabi cycle (at resonance) shown during the animation, the oscillation instead undergoes one full cycle, thus at twice the (normal) Rabi frequency , just as predicted by this equation. Also note that as the incident light frequency shifts further from the transition frequency, the amplitude of the Rabi oscillation decreases, as is illustrated by the dashed envelope in the above plot. | 0 | Theoretical and Fundamental Chemistry |
In the field of molecular physics, microwave spectroscopy is commonly used to probe the rotation of molecules. | 0 | Theoretical and Fundamental Chemistry |
The parent metallacyclobenzene has the formula LM(CH). They can be viewed as derivatives of benzene wherein a CH center has been replaced by a transition metal complex. Most metallabenzenes do not feature the M(CH) ring itself, but, instead, some of the H atoms are replaced by other substituents. | 0 | Theoretical and Fundamental Chemistry |
When the accumulation charge carrier removes the ground state of the neutral polymer, there is more transmission in the ground state. This is called bleaching . With the excess hole or electrons at the polymer, there will be new transitions at low energy levels, therefore the transmission intensity is reduced , this is related to charge absorption. | 0 | Theoretical and Fundamental Chemistry |
As it is only effective for primary amines, the carbylamine reaction can be used as a chemical test for their presence. In this context, the reaction is also known as Saytzeff's isocyanide test. In this reaction, the analyte is heated with alcoholic potassium hydroxide and chloroform. If a primary amine is present, the isocyanide (carbylamine) is formed, as indicated by a foul odour. The carbylamine test does not give a positive reaction with secondary and tertiary amines. | 0 | Theoretical and Fundamental Chemistry |
Because carbon is more electronegative than magnesium, the carbon attached to magnesium acts as a nucleophile and attacks the electrophilic carbon atom in the polar bond of a carbonyl group. The addition of the Grignard reagent to the carbonyl group typically proceeds through a six-membered ring transition state, as shown below.
Based on the detection of radical coupling side products, an alternative single electron transfer (SET) mechanism that involves the initial formation of a ketyl radical intermediate has also been proposed. A recent computational study suggests that the operative mechanism (polar vs. radical) is substrate-dependent, with the reduction potential of the carbonyl compound serving as a key parameter. | 0 | Theoretical and Fundamental Chemistry |
When the particles of a stabilized suspension transition from an immobile state to mobile state, small groupings of particles form hydroclusters, increasing the viscosity. These hydroclusters are composed of particles momentarily compressed together, forming an irregular, rod-like chain of particles akin to a logjam or traffic jam. In theory the particles have extremely small interparticle gaps, rendering this momentary, transient hydrocluster as incompressible. It is possible that additional hydroclusters will form through aggregation. | 1 | Applied and Interdisciplinary Chemistry |
Metal carbonyls are used in a number of industrially important carbonylation reactions. In the oxo process, an alkene, hydrogen gas, and carbon monoxide react together with a catalyst (such as dicobalt octacarbonyl) to give aldehydes. Illustrative is the production of butyraldehyde from propylene:
:CHCH=CH + H + CO → CHCHCHCHO
Butyraldehyde is converted on an industrial scale to 2-ethylhexanol, a precursor to PVC plasticizers, by aldol condensation, followed by hydrogenation of the resulting hydroxyaldehyde. The "oxo aldehydes" resulting from hydroformylation are used for large-scale synthesis of fatty alcohols, which are precursors to detergents. The hydroformylation is a reaction with high atom economy, especially if the reaction proceeds with high regioselectivity.
Another important reaction catalyzed by metal carbonyls is the hydrocarboxylation. The example below is for the synthesis of acrylic acid and acrylic acid esters:
Also the cyclization of acetylene to cyclooctatetraene uses metal carbonyl catalysts:
In the Monsanto and Cativa processes, acetic acid is produced from methanol, carbon monoxide, and water using hydrogen iodide as well as rhodium and iridium carbonyl catalysts, respectively. Related carbonylation reactions afford acetic anhydride. | 0 | Theoretical and Fundamental Chemistry |
Bioinformatic analysis identified four methyltransferases within the cluster. Bioinformatics suggest that btmB, is an O-methyltransferase, while the other three, btmC, G and K, are radical S-adenosyl methionine (SAM) methyltransferases. The radical SAM methyltransferases are believed to β-methylate amino acid residues within the precursor peptide. btmC is believed to methylate phenylalanine, btmG is believed to methylate both valines, and btmK is believed to methylate proline based on gene deletion studies.
The three putative radical SAM methyltransferases encoded within the pathway are interesting for both mechanistic and biosynthetic reasons. Radical SAM methyltransferases are likely to methylate substrates by an unusual mechanism. Biosynthetically, β-methylations of amino acids are highly unusual in natural products. Polytheonamide B, a peptide natural product produced by a marine symbiont, is the only other structurally characterized example of direct β-methylation of a peptide natural product. The proposed methyl transfer from a SAM-utilizing enzyme was supported by earlier feeding studies with labeled methionine; labeled methionine is used because methionine is converted into SAM within cells. Even further, this study used stereospecifically labeled methionine ([methyl-(H-H)]-(2S, methyl-R)-methionine) to show that methylation occurred with a net retention of stereochemistry at the methyl group. The author speculated that net retention indicated a radical mechanism with a B12 intermediate. Radical transfer with a Cobalamin B12 cofactor and SAM has been shown with the few characterized radical SAM methyltransferases. Although the evidence points to radical β-methylation during bottromycin biosynthesis, it remains to be seen whether bioinformatic hypothesis and feeding studies will be supported by in vitro activity assays.
The Val3Ala substitution in bottromycin D does not change the β-methylation pattern between bottromycin A2 and D because Val3 is the only valine not methylated in bottromycin A2. As such, there are still three predicted radical SAM dependent enzymes in the bottromycin D biosynthetic cluster: bstC, bstF, and bstJ.
As of 2013, all published biosynthetic studies have been bioinformatic or cell-based. No biochemical assays directly demonstrating protein function have yet been published. It is likely that in vitro mechanistic studies to better elucidate the biosynthetic pathway will be forthcoming. | 0 | Theoretical and Fundamental Chemistry |
Ocean dynamics define and describe the flow of water within the oceans. Ocean temperature and motion fields can be separated into three distinct layers: mixed (surface) layer, upper ocean (above the thermocline), and deep ocean.
Ocean dynamics has traditionally been investigated by sampling from instruments in situ.
The mixed layer is nearest to the surface and can vary in thickness from 10 to 500 meters. This layer has properties such as temperature, salinity and dissolved oxygen which are uniform with depth reflecting a history of active turbulence (the atmosphere has an analogous planetary boundary layer). Turbulence is high in the mixed layer. However, it becomes zero at the base of the mixed layer. Turbulence again increases below the base of the mixed layer due to shear instabilities. At extratropical latitudes this layer is deepest in late winter as a result of surface cooling and winter storms and quite shallow in summer. Its dynamics is governed by turbulent mixing as well as Ekman transport, exchanges with the overlying atmosphere, and horizontal advection.
The upper ocean, characterized by warm temperatures and active motion, varies in depth from 100 m or less in the tropics and eastern oceans to in excess of 800 meters in the western subtropical oceans. This layer exchanges properties such as heat and freshwater with the atmosphere on timescales of a few years. Below the mixed layer the upper ocean is generally governed by the hydrostatic and geostrophic relationships. Exceptions include the deep tropics and coastal regions.
The deep ocean is both cold and dark with generally weak velocities (although limited areas of the deep ocean are known to have significant recirculations). The deep ocean is supplied with water from the upper ocean in only a few limited geographical regions: the subpolar North Atlantic and several sinking regions around the Antarctic. Because of the weak supply of water to the deep ocean the average residence time of water in the deep ocean is measured in hundreds of years. In this layer as well the hydrostatic and geostrophic relationships are generally valid and mixing is generally quite weak. | 1 | Applied and Interdisciplinary Chemistry |
A pepper-spray projectile, also called a pepper-spray ball, pepper-ball, pepper bomb, or pepper-spray pellet, is a frangible projectile containing a powdered chemical that irritates the eyes and nose in a manner similar to pepper spray. These projectiles are fired from specially designed forced compliance weapons or modified paintball guns. | 1 | Applied and Interdisciplinary Chemistry |
PEC further opened the following regional offices in the provincial capitals of Pakistan:
* Karachi Branch Office (inaugurated on 23 June 1987)
* Lahore Branch Office (inaugurated on 30 January 1988)
* Quetta Branch Office (inaugurated on 17 February 1988)
* Peshawar Branch Office (inaugurated on 27 March 1988)
* Multan Branch Office (inaugurated on 1 June 2016)
* Hyderabad Branch Office (inaugurated on 1 June 2016) | 1 | Applied and Interdisciplinary Chemistry |
Several synthesis routes exist, the most common being the reaction between alkyl halides and alkali thiocyanate in aqueous media. Illustrative is the preparation of isopropyl thiocyanate by treatment of isopropyl bromide with sodium thiocyanate in boiling ethanol. The main complication with this route is the competing formation of alkyisothiocyanates. "SN1-type" substrates (e.g., benzyl halides) tend to give the isothiocyanate derivatives.
Some organic thiocyanates are generated by cyanation of some organosulfur compounds. Sulfenyl thiosulfates (RSSO) react with alkali metal cyanides to give thiocyanates with displacement of sulfite. This approach has been applied to allyl thiocyanate:
Sulfenyl chlorides (RSCl) also convert to thiocyanates.
Aryl thiocyanates are traditionally produced by the Sandmeyer reaction, which involves combining copper(I) thiocyanate and diazonium salts:
Some arylthiocyanates can also often be obtained by thiocyanogenation, i.e. the reaction of thiocyanogen. This reaction is favored for electron-rich aromatic substrates. | 0 | Theoretical and Fundamental Chemistry |
The American Society of Mechanical Engineers (ASME) has developed two separate and distinct standards on temperature Measurement, B40.200 and PTC 19.3.
B40.200 provides guidelines for bimetallic-actuated, filled-system, and liquid-in-glass thermometers. It also provides guidelines for thermowells.
PTC 19.3 provides guidelines for temperature measurement related to Performance Test Codes with particular emphasis on basic sources of measurement errors and techniques for coping with them. | 0 | Theoretical and Fundamental Chemistry |
This bibliography of Rutherford Aris contains a comprehensive listing of the scientific publications of Aris, including books, journal articles, and contributions to other published material. | 1 | Applied and Interdisciplinary Chemistry |
One of the most commonly used fiber production methods is the crosslinking of sodium alginate by CaCl, where the formed calcium alginate will act as the crosslinking point to link the alginate chains together to form the network and solidified the polymer. Afterward, this alginate hydrogel fiber can be used as a template for the polymerization of secondary networks. Additionally, by controlling the fluid dynamics inside the microfluid device, the diameter and the shape of the resulting fiber can be tuned without doing modification to the devices.
A practice would be the production of alginate solution reported by Yang et al. They used the sodium alginate as core fluid and CaCl as shealth fluid, the crosslinked network (hydrogel fiber) formed once this two fluid met, the laminar flow kept its tubular shape during the reaction. | 0 | Theoretical and Fundamental Chemistry |
Fas signaling pathway involves activating apoptosis (programmed cell death). This happens through the interaction of Fas receptor and Fas ligand. As mentioned, Fas ligand/FasL is a type II transmembrane protein that can exist in both membrane-anchored and soluble forms. The interaction between FasR on an adjacent cell and membrane anchored FasL leads to the trimerization, forming the death-inducing signaling complex (DISC).
Upon ensuing death domain (DD) aggregation, the receptor complex is internalized via the cellular endosomal machinery. This allows the adaptor molecule Fas-associated death domain (FADD) to bind the death domain (DD) of Fas through its own death domain (DD). FADD also contains a death effector domain (DED) near its amino terminus, which facilitates binding to the DED of FADD-like ICE (FLICE), more commonly referred to as caspase-8. FLICE can then self-activate through proteolytic cleavage into p10 and p18 subunits, of which two form the active heterotetramer enzyme. Active caspase-8 is then released from the DISC into the cytosol, where it cleaves other effector caspases, eventually leading to DNA degradation, membrane blebbing, and other hallmarks of apoptosis.
Some reports have suggested that the extrinsic Fas pathway is sufficient to induce complete apoptosis in certain cell types through death-inducing signaling complex (DISC) assembly and subsequent caspase-8 activation. These cells are dubbed Type 1 cells and are characterized by the inability of anti-apoptotic members of the Bcl-2 family (namely Bcl-2 and Bcl-xL) to protect from Fas-mediated apoptosis. Characterized Type 1 cells include H9, CH1, SKW6.4, and SW480, all of which are lymphocyte lineages except for SW480, which is of the colon adenocarcinoma lineage.
Moreover, the pathways in the Fas signal cascade exhibit evidence for crosstalk. In most cell types, caspase-8 catalyzes the cleavage of the pro-apoptotic BH3-only protein Bid into its truncated form, tBid. BH-3 only members of the Bcl-2 family engage exclusively anti-apoptotic members of the family (Bcl-2, Bcl-xL), allowing Bak and Bax to translocate to the outer mitochondrial membrane, thus permeabilizing it and facilitating release of pro-apoptotic proteins such as cytochrome c and Smac/DIABLO, an antagonist of inhibitors of apoptosis proteins (IAPs).
Additionally, the c-FLIP protein, structurally resembling caspase-8 but lacking enzymatic activity, plays a dual role in Fas-induced apoptosis. At low concentrations, c-FLIP is believed to promote caspase-8 activation. There is a possibility it is because caspase-8 binds to c-FLIP with higher affinity than to itself (caspase-8 homo-dimerization). However, at high concentrations, c-FLIP reduces the proteolytic activity of caspase-8, potentially by competing for binding to FADD. This dual role underscores the complexity of Fas signaling and its regulation by c-FLIP at different concentrations. | 1 | Applied and Interdisciplinary Chemistry |
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