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Organic reactions are chemical reactions involving organic compounds. The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis, organic reactions are used in the construction of new organic molecules. The production of many man-made chemicals such as drugs, plastics, food additives, fabrics depend on organic reactions.
The oldest organic reactions are combustion of organic fuels and saponification of fats to make soap. Modern organic chemistry starts with the Wöhler synthesis in 1828. In the history of the Nobel Prize in Chemistry awards have been given for the invention of specific organic reactions such as the Grignard reaction in 1912, the Diels–Alder reaction in 1950, the Wittig reaction in 1979 and olefin metathesis in 2005. | 0 | Theoretical and Fundamental Chemistry |
Because BIK1 is a possible regulator of the FLS2-BAK1 complex, it is speculated that in vitro, BAK1 phosphorylates BIK1, which then phosphorylates both FLS2 and BAK1. However, in vivo, BIK1 is not phosphorylated until about 5-10 minutes after the addition of FS2, and the peak phosphorylation occurs just after the phosphorylation of the FS2-BAK1 complex. It is speculated that BIK1 activation might be enhanced through transphosphorylation by BAK1 rather than by FLS2 because FLS2 more likely serves as a scaffold protein for the arrangement of the BAK1-FLS2 complex. This hypothesis will require more testing in vivo. Research has shown that BIK1 and BAK1 are signaling partners for the flagellin receptor FLS2 and that the three together initiate defense response. However, BIK1 and BAK1 phosphorylate different residues of the FLS2 receptor with the exception of only a select few. This suggests that both BAK1 and BIK1 play unique roles in defense response by a series of phosphorylation reactions with one another and the flagellin receptor FLS2. | 1 | Applied and Interdisciplinary Chemistry |
Adil E. Shamoo (born August 1, 1941) is an Iraqi biochemist with an interest in biomedical ethics and foreign policy. He is currently a professor at the Department of Biochemistry and Molecular Biology at the University of Maryland. | 1 | Applied and Interdisciplinary Chemistry |
Light enters the eye, passes through the optical media, then the inner neural layers of the retina before finally reaching the photoreceptor cells in the outer layer of the retina. The light may be absorbed by a chromophore bound to an opsin, which photoisomerizes the chromophore, initiating both the visual cycle, which "resets" the chromophore, and the phototransduction cascade, which transmits the visual signal to the brain. The cascade begins with graded polarisation (an analog signal) of the excited photoreceptor cell, as its membrane potential increases from a resting potential of -70 mV, proportional to the light intensity. At rest, the photoreceptor cells are continually releasing glutamate at the synaptic terminal to maintain the potential. The transmitter release rate is lowered (hyperpolarization) as light intensity increases. Each synaptic terminal makes up to 500 contacts with horizontal cells and bipolar cells. These intermediate cells (along with amacrine cells) perform comparisons of photoreceptor signals within a receptive field, but their precise functionalities are not well understood. The signal remains as a graded polarization in all cells until it reaches the RGCs, where it is converted to an action potential and transmitted to the brain. | 1 | Applied and Interdisciplinary Chemistry |
After amplifying and then concentrating the target analyte, the samples are labeled with a fluorescent dye using an antibody for specificity and then finally loaded into a microcapillary tube. This tube is placed in a specially constructed apparatus so it is totally surrounded by optical fibers to capture all light emitted once the dye is excited using a laser. | 1 | Applied and Interdisciplinary Chemistry |
The volatility of the tetrachloride and tetraiodide complexes of Ti(IV) is exploited in the purification of titanium by the Kroll and van Arkel–de Boer processes, respectively.
Metal halides act as Lewis acids. Ferric and aluminium chlorides are catalysts for the Friedel-Crafts reaction, but due to their low cost, they are often added in stoichiometric quantities.
Chloroplatinic acid (HPtCl) is an important catalyst for hydrosilylation. | 0 | Theoretical and Fundamental Chemistry |
"Methylmercury" is a shorthand for the hypothetical "methylmercury cation", sometimes written methylmercury(1+) cation or methylmercury(II) cation. This functional group is composed of a methyl group bonded to an atom of mercury. Its chemical formula is (sometimes written as ).The Methylmercury compound has an overall charge of +1, with Hg in the +2 oxidation state. Methylmercury exists as a substituent in many complexes of the type (L = Lewis base) and MeHgX (X = anion).
As a positively charged ion, it readily combines with anions such as chloride (), hydroxide () and nitrate (). It has particular affinity for sulfur-containing anions, particularly thiols (). Thiols are generated when the amino acid cysteine and the peptide glutathione form strong complexes with methylmercury: | 0 | Theoretical and Fundamental Chemistry |
The Frank Newman Speller Award is an annual award for significant contributions to corrosion engineering and is administered by NACE International. (The organization was previously known as the National Association of Corrosion Engineers.) The award is named in honor of Frank Newman Speller, a Canadian-born American metallurgical engineer notable for his pioneering text on corrosion. | 1 | Applied and Interdisciplinary Chemistry |
Sulfur is found in oxidation states ranging from +6 in Sulfate| to −2 in sulfides. Thus, elemental sulfur can either give or receive electrons depending on its environment. On the anoxic early Earth, most sulfur was present in minerals such as pyrite (FeS). Over Earth history, the amount of mobile sulfur increased through volcanic activity as well as weathering of the crust in an oxygenated atmosphere. Earth's main sulfur sink is the oceans , where it is the major oxidizing agent.
When is assimilated by organisms, it is reduced and converted to organic sulfur, which is an essential component of proteins. However, the biosphere does not act as a major sink for sulfur, instead the majority of sulfur is found in seawater or sedimentary rocks including: pyrite rich shales, evaporite rocks (anhydrite and baryte), and calcium and magnesium carbonates (i.e. carbonate-associated sulfate). The amount of sulfate in the oceans is controlled by three major processes:
# input from rivers
# sulfate reduction and sulfide re-oxidation on continental shelves and slopes
# burial of anhydrite and pyrite in the oceanic crust.
The primary natural source of sulfur to the atmosphere is sea spray or windblown sulfur-rich dust, neither of which is long lived in the atmosphere. In recent times, the large annual input of sulfur from the burning of coal and other fossil fuels has added a substantial amount of SO which acts as an air pollutant. In the geologic past, igneous intrusions into coal measures have caused large scale burning of these measures, and consequential release of sulfur to the atmosphere. This has led to substantial disruption to the climate system, and is one of the proposed causes of the Permian–Triassic extinction event.
Dimethylsulfide [(CH)S or DMS] is produced by the decomposition of dimethylsulfoniopropionate (DMSP) from dying phytoplankton cells in the ocean's photic zone, and is the major biogenic gas emitted from the sea, where it is responsible for the distinctive “smell of the sea” along coastlines. DMS is the largest natural source of sulfur gas, but still only has a residence time of about one day in the atmosphere and a majority of it is redeposited in the oceans rather than making it to land. However, it is a significant factor in the climate system, as it is involved in the formation of clouds. | 0 | Theoretical and Fundamental Chemistry |
Classical transport models a plasma in a magnetic field as a large number of particles traveling in helical paths around a line of force. In typical reactor designs, the lines are roughly parallel, so particles orbiting adjacent lines may collide and scatter. This results in a random walk process which eventually leads to the particles finding themselves outside the magnetic field.
Neoclassical transport adds the effects of the geometry of the fields. In particular, it considers the field inside the tokamak and similar toroidal arrangements, where the field is stronger on the inside curve than the outside simply due to the magnets being closer together in that area. To even out these forces, the field as a whole is twisted into a helix, so that the particles alternately move from the inside to the outside of the reactor.
In this case, as the particle transits from the outside to the inside, it sees an increasing magnetic force. If the particle energy is low, this increasing field may cause the particle to reverse directions, as in a magnetic mirror. The particle now travels in the reverse direction through the reactor, to the outside limit, and then back towards the inside where the same reflection process occurs. This leads to a population of particles bouncing back and forth between two points, tracing out a path that looks like a banana from above, the so-called banana orbits.
Since any particle in the long tail of the Maxwell–Boltzmann distribution is subject to this effect, there is always some natural population of such banana particles. Since these travel in the reverse direction for half of their orbit, their drift behavior is oscillatory in space. Therefore, when the particles collide, their average step size (width of the banana) is much larger than their gyroradius, leading to neoclassical diffusion across the magnetic field. | 1 | Applied and Interdisciplinary Chemistry |
The Tsuji–Wilkinson decarbonylation reaction is a method for the decarbonylation of aldehydes and some acyl chlorides. The reaction name recognizes Jirō Tsuji, whose team first reported the use of Wilkinson's catalyst (RhCl(PPh)) for these reactions:
:RC(O)X + RhCl(PPh) → RX + RhCl(CO)(PPh) + PPh
Although decarbonylation can be effected by several transition metal complexes, Wilkinson's catalyst has proven the most effective. | 0 | Theoretical and Fundamental Chemistry |
An estimated 160 TBq (about 250 kg) of technetium-99 was released into the environment up to 1994 by atmospheric nuclear tests. The amount of technetium-99 from civilian nuclear power released into the environment up to 1986 is estimated to be on the order of 1000 TBq (about 1600 kg), primarily by outdated methods of nuclear fuel reprocessing; most of this was discharged into the sea. In recent years, reprocessing methods have improved to reduce emissions, but the primary release of technetium-99 into the environment is by the Sellafield plant, which released an estimated 550 TBq (about 900 kg) from 1995–1999 into the Irish Sea. From 2000 onwards the amount has been limited by regulation to 90 TBq (about 140 kg) per year. | 0 | Theoretical and Fundamental Chemistry |
Mesoscopic heat engines are nanoscale devices that may serve the goal of processing heat fluxes and perform useful work at small scales. Potential applications include e.g. electric cooling devices. In such mesoscopic heat engines, work per cycle of operation fluctuates due to thermal noise. There is exact equality that relates average of exponents of work performed by any heat engine and the heat transfer from the hotter heat bath. This relation transforms the Carnots inequality into exact equality. This relation is also a Carnot cycle equality | 0 | Theoretical and Fundamental Chemistry |
One of the major potential applications of aluminum-based nanogalvanic alloys is hydrogen production for fuel cells. Due to their high energy efficiency, non-toxic nature, and transportation ease, the alloy powders have also been considered as an alternative energy source for batteries (when coupled with fuel cells) during reconnaissance for soldiers on the battlefield. Additionally, the alloy powder may also be 3D-printed into self-cannibalizing drone components that could recharge the drone's hydrogen supply by making contact with water whenever it runs low on power. ARL researchers also discovered that the hydrogen generation rate increases by almost two-fold when the aluminum based nanogalvanic alloy powder comes in contact with urine, when compared with pure water. Because of this unique property, scientists have considered applying the aluminum powder in austere environments where power and water are scarce, such as deserts or space, where urine could be repurposed as a fuel source. | 1 | Applied and Interdisciplinary Chemistry |
RiPPs consist of any peptides (i.e. molecular weight below 10 kDa) that are ribosomally-produced and undergo some degree of enzymatic post-translational modification. This combination of peptide translation and modification is referred to as "post-ribosomal peptide synthesis" (PRPS) in analogy with nonribosomal peptide synthesis (NRPS).
Historically, the current sub-classes of RiPPs were studied individually, and common practices in nomenclature varied accordingly in the literature. More recently, with the advent of broad genome sequencing, it has been realized that these natural products share a common biosynthetic origin. In 2013, a set of uniform nomenclature guidelines were agreed upon and published by a large group of researchers in the field. Prior to this report, RiPPs were referred to by a variety of designations, including post-ribosomal peptides, ribosomal natural products, and ribosomal peptides.
The acronym "RiPP" stands for "ribosomally synthesized and post-translationally modified peptide". | 1 | Applied and Interdisciplinary Chemistry |
According to metallurgist Jack Harris, "Oxidation is usually accompanied by a net expansion so that when it occurs in a confined space stresses are generated in the metal component itself or in any surrounding medium such as stone or cement. So much energy is released by oxidation that the stresses generated are of sufficient magnitude to deform or fracture all known materials."
As early as 1915, it was recognized that certain modern metal alloys are more susceptible to excessive oxidation when subjected to weathering than other metals. At that time, there was a trend to replace wrought iron fasteners with mild steel equivalents, which were less expensive. Unexpectedly, the mild steel fasteners failed in real world use much more quickly than anticipated, leading to a return to use of wrought iron in certain applications where length of service was important. | 1 | Applied and Interdisciplinary Chemistry |
An electrocatalyst is a catalyst that participates in electrochemical reactions. Electrocatalysts are a specific form of catalysts that function at electrode surfaces or, most commonly, may be the electrode surface itself. An electrocatalyst can be heterogeneous such as a platinized electrode. Homogeneous electrocatalysts, which are soluble, assist in transferring electrons between the electrode and reactants, and/or facilitate an intermediate chemical transformation described by an overall half reaction. Major challenges in electrocatalysts focus on fuel cells. | 0 | Theoretical and Fundamental Chemistry |
A (by no means exhaustive) selection of models of biological systems involving multi-state molecules and using some of the tools discussed here is give in the table below. | 1 | Applied and Interdisciplinary Chemistry |
A dominant role for the mitochondria is the production of ATP, as reflected by the large number of proteins in the inner membrane for this task. This is done by oxidizing the major products of glucose: pyruvate, and NADH, which are produced in the cytosol. This type of cellular respiration, known as aerobic respiration, is dependent on the presence of oxygen. When oxygen is limited, the glycolytic products will be metabolized by anaerobic fermentation, a process that is independent of the mitochondria. The production of ATP from glucose and oxygen has an approximately 13-times higher yield during aerobic respiration compared to fermentation. Plant mitochondria can also produce a limited amount of ATP either by breaking the sugar produced during photosynthesis or without oxygen by using the alternate substrate nitrite. ATP crosses out through the inner membrane with the help of a specific protein, and across the outer membrane via porins. After conversion of ATP to ADP by dephosphorylation that releases energy, ADP returns via the same route. | 1 | Applied and Interdisciplinary Chemistry |
Chemical thermodynamics is the study of the interrelation of energy with chemical reactions or with a physical change of state within the confines of the laws of thermodynamics. The primary objective of chemical thermodynamics is determining the spontaneity of a given transformation. | 0 | Theoretical and Fundamental Chemistry |
Illustrative of their alkylating activity are reactions with potassium iodide in acetone, chloroacetone reacts faster than 1-chloropropane by a factor of 36,000. Halo ketones react with phosphites in the Perkow reaction.
The halo group can be removed in reductive dehalogenation of halo ketones. α-Halo ketones can also be converted to alkenes by treatment with hydrazine.
Due to the presence of two electron withdrawing groups (carbonyl and halide), the α-hydrogen is acidic. This property is exploited in the Favorskii rearrangement, where base abstracts first an acidic α-hydrogen and the resulting carbanion then displaces the halogen.
In crossed aldol reactions between halo ketones and aldehydes, the initial reaction product is a halohydrin which can subsequently form an oxirane in the presence of base.
α-Halo ketones can react with amines to form an α-halo imine, which can be converted back to the parent halo ketone by hydrolysis, so that halo imines may be used as masked versions of halo ketones. This allows some chemical transformations to be achieved that are not possible with the parent halo ketones directly. | 0 | Theoretical and Fundamental Chemistry |
A 2018 Cochrane review found that it produced moderate improvement in sleep onset and maintenance. The authors suggest that where preferred non-pharmacological treatment strategies have been exhausted, eszopiclone provides an efficient treatment for insomnia. In 2014, the US Food and Drug Administration asked that the starting dose be lowered from 2 milligrams to 1 milligram after it was observed in a study that even eight hours after taking the drug at night, some people were not able to cope with their next-day activities like driving and other activities that require full alertness.
Eszopiclone is slightly effective in the treatment of insomnia where difficulty in falling asleep is the primary complaint. The benefit over placebo was found to be of questionable clinical significance. Although the drug effect and the placebo response were rather small and of questionable clinical importance, the two together produce a reasonably large clinical response. | 0 | Theoretical and Fundamental Chemistry |
Mercury is a toxic heavy metal, and as such it is important to be able to detect it in biological systems. Sensors include:
*Mercury Sensors (MS), a family of sensors that comprise complexes of fluorescein and napthofluorescein. The MS1 probe increases its emission upon binding of Hg(II), while maintaining great affinity for mercury over other heavy metal ions.
*The S3 sensor is based on a BODIPY complex which undergoes a significant increase in fluorescence upon the binding of Hg(II).
*MF1 uses a soft thioether chelator for Hg(II) bound to a fluorescein-like xanthenone reporter. It has good contrast upon binding mercury and good selectivity. MF1 is sensitive enough that it has been proposed to be used to test fish for toxic levels of mercury. | 0 | Theoretical and Fundamental Chemistry |
Relatively little is known about isotopic fractionation of zinc by biological processes, but several studies have elucidated that Zn isotopes fractionate during surface adsorption, intracellular uptake processes and speciation. Many organisms, including certain species of fish, plants and marine phytoplankton, have both high- and low-affinity Zn transport systems, which appear to fractionate Zn isotopes differently. A study by John et al. observed apparent isotope effects associated with Zn uptake by the marine diatom Thalassiosira oceanica of -0.2‰ for high-affinity uptake (at low Zn concentrations) and -0.8‰ for low-affinity uptake (at high Zn concentrations). Additionally, in this study, unwashed cells were enriched in Zn, indicating preferential adsorption of Zn to the extracellular surfaces of T. oceanica. Results from John et al. demonstrating apparent discrimination against the heavy isotope (Zn) during uptake conflict with results by Gélabert et al. in which marine phytoplankton and freshwater periphytic organisms preferentially uptook Zn from solution. The latter authors explained these results as due to a preferential partitioning of Zn into a tetrahedrally coordinated structure (i.e., with carboxylate, amine or silanol groups on or inside the cell) over an octahedral coordination with six water molecules in the aqueous phase, consistent with quantum mechanical predictions. Kafantaris and Borrok grew model organisms B. subtilis, P. mendocina and E. coli, as well as a natural bacterial consortium collected from soil, on high and low concentrations of Zn. In the high [Zn] condition, the average fractionation of Zn isotopes imparted by cellular surface adsorption was +0.46‰ (i.e., Zn was preferentially adsorbed), while fractionation upon intracellular incorporation varied from -0.2 to +0.5‰ depending on the bacterial species and growth phase. Empirical models of the low [Zn] condition estimated larger Zn isotope fractionation factors for surface adsorption ranging from +2 to +3‰. Overall, Zn isotope ratios in microbes appear to be driven by a number of complex factors including surface interactions, bacterial metal metabolism and metal speciation, but by understanding the relative contributions of these factors to Zn isotope signals, one can use Zn isotopes to investigate metal-binding pathways operating in natural communities of microbes. | 0 | Theoretical and Fundamental Chemistry |
In order to study gas phase interstellar chemistry, it is convenient to distinguish two types of interstellar clouds: diffuse clouds, with T=30-100 K, and n=10–1000 cm, and dense clouds with T=10-30K and density n=-. Ion chemical routes in both dense and diffuse clouds have been established for some works (Hartquist 1990). | 1 | Applied and Interdisciplinary Chemistry |
There are two types of neuraminidase inhibitors commonly available for treatment and prophylaxis of influenza infections: Zanamivir and Oseltamivir. They interfere with the release of progeny virions from infected host cells, prevent infection process of new host cells and stop spread of infection in respiratory tract by mimicking natural substrate and fitting into active site of neuraminidase enzyme. They interrupt the detachment of progeny virions. Viral replication rate is then reduced and that allows human immune system to destroy the remaining viruses. | 1 | Applied and Interdisciplinary Chemistry |
The recovery of benthic communities is primarily dependent upon the length and severity of hypoxic conditions inside the hypoxic zone. Less severe conditions and temporary depletion of oxygen allow rapid recovery of benthic communities in the area due to reestablishment by benthic larvae from adjacent areas, with longer conditions of hypoxia and more severe oxygen depletion leading to longer reestablishment periods. Recovery also depends upon stratification levels within the area, so heavily stratified areas in warmer waters are less likely to recover from anoxic or hypoxic conditions in addition to being more susceptible to eutrophication driven hypoxia. The difference in recovery ability and susceptibility to hypoxia in stratified marine environments is expected to complicate recovery efforts of dead zones in the future as ocean warming continues.
Small scale hypoxic systems with rich surrounding communities are the most likely to recover after nutrient influxes leading to eutrophication stop. However, depending on the extent of damage and characteristics of the zone, large scale hypoxic condition could also potentially recover after a period of a decade. For example, the Black Sea dead zone, previously the largest in the world, largely disappeared between 1991 and 2001 after fertilizers became too costly to use following the collapse of the Soviet Union and the demise of centrally planned economies in Eastern and Central Europe. Fishing has again become a major economic activity in the region.
While the Black Sea "cleanup" was largely unintentional and involved a drop in hard-to-control fertilizer usage, the U.N. has advocated other cleanups by reducing large industrial emissions. From 1985 to 2000, the North Sea dead zone had nitrogen reduced by 37% when policy efforts by countries on the Rhine River reduced sewage and industrial emissions of nitrogen into the water. Other cleanups have taken place along the Hudson River and San Francisco Bay. | 0 | Theoretical and Fundamental Chemistry |
Metals in their native state are those found in nature as free elements (chemically uncombined). They are usually attached to or mixed with varying amounts of undesired material (gangue), and require only physical separation to produce usable metal.
Most metallic ores in the Earth's crust require chemical processing to produce metal. Oxides and sulfides require smelting. Bauxite, an ore of aluminium, requires electrolysis.
Many metals are found in uncombined metallic form, in varying degrees of purity. These "metals found as metals" are referred to as native metals, which are a subset of native element minerals. The most well-known native metals are native copper and gold. Nonreactive noble metals usually occur in nature as native metals. | 1 | Applied and Interdisciplinary Chemistry |
The synthesis of the all-important dipeptide-like side chain involves alkylation of the tert-butyl ester of -alanine (2) with ethyl 2-bromo-4-phenylbutanoate (1); the presominane of the desired isomer is attributable to asymmetric induction from the adjacent chiral center. Reaction of the product with hydrogen chloride then cleaves the tert-butyl group to give the half acid (3). Coupling of that acid to the secondary amine on tetrahydroisoquinoline (4) gives the corresponding amine. The tert-butyl ester in this product is again cleaved with hydrogen chloride to afford moexipril (5). | 0 | Theoretical and Fundamental Chemistry |
A statue of Hans Christian Ørsted was installed in the Ørsted Park in 1880. A commemorative plaque is located above the gate on the building in where he lived and worked.
In 1885, a statue of Ørsted was installed in the Oxford University Museum of Natural History.
Ørsted's likeness has appeared twice on Danish banknotes; for the first time on 500kroner notes issued in 1875, and for the second time on 100kroner notes issued between 1962 and 1974. | 1 | Applied and Interdisciplinary Chemistry |
Chlorofluorocarbons (CFCs) are anthropogenic compounds that have been released into the atmosphere since the 1930s in various applications such as in air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans, and as solvents. The entry of CFCs into the ocean makes them extremely useful as transient tracers to estimate rates and pathways of ocean circulation and mixing processes. However, due to production restrictions of CFCs in the 1980s, atmospheric concentrations of CFC-11 and CFC-12 has stopped increasing, and the CFC-11 to CFC-12 ratio in the atmosphere have been steadily decreasing, making water dating of water masses more problematic. Incidentally, production and release of sulfur hexafluoride (SF) have rapidly increased in the atmosphere since the 1970s. Similar to CFCs, SF is also an inert gas and is not affected by oceanic chemical or biological activities. Thus, using CFCs in concert with SF as a tracer resolves the water dating issues due to decreased CFC concentrations.
Using CFCs or SF as a tracer of ocean circulation allows for the derivation of rates for ocean processes due to the time-dependent source function. The elapsed time since a subsurface water mass was last in contact with the atmosphere is the tracer-derived age. Estimates of age can be derived based on the partial pressure of an individual compound and the ratio of the partial pressure of CFCs to each other (or SF). | 1 | Applied and Interdisciplinary Chemistry |
Streng was among the first women to receive a degree in mining engineering from Donetsk Mining Institute. She was born in the Russia Empire. During World War II she fled the Soviet Union with her husband and son. The family settled in West Germany for several years, then emigrated to the United States in 1950. Lucia Streng earned money painting china lamps until she and her husband found positions at Temple University. | 0 | Theoretical and Fundamental Chemistry |
In chaos theory and fluid dynamics, chaotic mixing is a process
by which flow tracers develop into complex fractals under the action
of a fluid flow.
The flow is characterized by an exponential growth of fluid filaments.
Even very simple flows, such as the blinking vortex,
or finitely resolved wind fields can generate exceptionally complex
patterns from initially simple tracer fields.
The phenomenon is still not well understood and is the subject
of much current research. | 1 | Applied and Interdisciplinary Chemistry |
The magnetic field induces a sine wave in a rotating coil. The amplitude of the signal is proportional to the strength of the field, provided it is uniform, and to the sine of the angle between the rotation axis of the coil and the field lines. This type of magnetometer is obsolete. | 0 | Theoretical and Fundamental Chemistry |
DNA microarray studies done on different fish species exposed to low-oxygen conditions have shown that at the genetic level fish respond to hypoxia by changing the expression of genes involved in oxygen transport, ATP production, and protein synthesis. In the liver of mudsuckers exposed to hypoxia there were changes in the expression of genes involved in heme metabolism such as hemopexin, heme oxygenase 1, and ferritin. Changes in the sequestration and metabolism of iron may suggest hypoxia induced erythropoiesis and increased demand for hemoglobin synthesis, leading to increased oxygen uptake and transport. Increased expression of myoglobin, which is normally only found in muscle tissue, has also been observed after hypoxia exposure in the gills of zebrafish and in non-muscle tissue of the common carp suggesting increased oxygen transport throughout fish tissues.
Microarray studies done on fish species exposed to hypoxia typically show a metabolic switch, that is, a decrease in the expression of genes involved in aerobic metabolism and an increase in expression of genes involved in anaerobic metabolism. Zebrafish embryos exposed to hypoxia decreased expression of genes involved in the citric acid cycle including, succinate dehydrogenase, malate dehydrogenase, and citrate synthase, and increased expression of genes involved in glycolysis such as phosphoglycerate mutase, enolase, aldolase, and lactate dehydrogenase. A decrease in protein synthesis is an important response to hypoxia to decrease ATP demand for whole organism metabolic suppression. Decreases in the expression of genes involved in protein synthesis, such as elongation factor-2 and several ribosomal proteins, have been shown in the muscle of the mudsucker and gills of adult zebrafish after hypoxia exposure .
Research in mammals has implicated hypoxia inducible factor (HIF) as a key regulator of gene expression changes in response to hypoxia However, a direct link between fish HIFs and gene expression changes in response to hypoxia has yet to be found. Phylogenetic analysis of available fish, tetrapod, and bird HIF-α and -β sequences shows that the isoforms of both subunits present in mammals are also represented in fish Within fish, HIF sequences group close together and are distinct from tetrapod and bird sequences. As well, amino acid analysis of available fish HIF-α and -β sequences reveals that they contain all functional domains shown to be important for mammalian HIF function, including the basic helix-loop-helix (bHLH) domain, Per-ARNT-Sim (PAS) domain, and the oxygen-dependent degradation domain (ODD), which render the HIF-α subunit sensitive to oxygen levels. The evolutionary similarity between HIF sequences in fish, tetrapods and birds, as well as the conservation of important functional domains suggests that HIF function and regulation is similar between fish and mammalian species. There is also evidence of novel HIF mechanisms present in fish not found in mammals. In mammals, HIF-α protein is continuously synthesized and regulated post-translationally by changing oxygen conditions, but it has been shown in different fish species that HIF-α mRNA levels are also responsive to hypoxia. In the hypoxia tolerant grass carp, substantial increases in HIF-1α and HIF-3α mRNA were observed in all tissues after hypoxia exposure. Likewise, mRNA levels of HIF-1α and HIF-2α were hypoxia-responsive in the ovaries of the Atlantic croaker during both short and long term hypoxia. | 0 | Theoretical and Fundamental Chemistry |
Levan was first discovered through research on nattō, a traditional Japanese dish. Natto was known as a "superfood" which promoted health and longevity in Japan during the late 1800s. In 1881, Edmund Oscar von Lippmann first discovered "lävulan" (levan) as the remaining gum from molasses in sugar beet production. Later in 1901, Greig-Smith coined the name “levan” based on the levorotatory properties of this substance in polarized light. | 1 | Applied and Interdisciplinary Chemistry |
The most common boundary that comes upon in confined fluid flow problems is the wall of the conduit. The appropriate requirement is called the no-slip boundary condition, wherein the normal component of velocity is fixed at zero, and the tangential component is set equal to the velocity of the wall. It may run counter to intuition, but the no-slip condition has been firmly established in both experiment and theory, though only after decades of controversy and debate.
Heat transfer through the wall can be specified or if the walls are considered adiabatic, then heat transfer across the wall is set to zero. | 1 | Applied and Interdisciplinary Chemistry |
Normality is defined as the number of gram or mole equivalents of solute present in one litre of solution. The SI unit of normality is equivalents per litre (Eq/L).
where is normality, is the mass of solute in grams, is the equivalent weight of solute, and is the volume of the entire solution in litres. | 0 | Theoretical and Fundamental Chemistry |
Electrophilic additions can be affected with a wide variety of organometallic reagents. Organosilanes offer the advantage of greater robustness to a wide array of reaction conditions than allyl compounds of more electropositive metals, and do not spontaneously undergo allylic rearrangement or epimerization. Additionally, organosilanes are rarely toxic and their reactions can be easily tracked by NMR spectroscopy (because of distinctive changes in the position of resonance of the methyl groups attached to silicon as addition occurs). Reactions of allylsilanes are similar in many respects to reactions of silyl enol ethers—in fact, allylsilanes can be used as masked enolate equivalents. After addition of the allylsilane, ozonolysis provides the corresponding carbonyl compound. | 0 | Theoretical and Fundamental Chemistry |
F magnetic resonance imaging (MRI) is a viable alternative to H MRI. The sensitivity issues can be overcome by using soft nanoparticles. Application include pH-, temperature-, enzyme-, metal ion- and redox responsive- contrast agents. They can also be used for long-term cell labelling. | 0 | Theoretical and Fundamental Chemistry |
Each member company is entitled to put one representative on the board of directors. The Board then elects an executive committee that directs the detailed business through the President and the Secretary of the company. The president is elected by the board of directors.
A Technical Advisory Committee, which also has one representative from each member company, oversees the research program. This committee elects a chairman and a smaller Technical Committee. The Technical Committee works with the FRI Technical Director (a full-time employee of FRI) to execute the research projects performed by the staff. Full-time staff currently includes eight technicians and six chemical engineers. | 1 | Applied and Interdisciplinary Chemistry |
Another route to is the Raschig process: aqueous ammonium nitrite is reduced by Bisulfite| and Sulfur dioxide| at 0 °C to yield a hydroxylamido-N,N-disulfonate anion:
This anion is then hydrolyzed to give hydroxylammonium sulfate :
Solid can be collected by treatment with liquid ammonia. Ammonium sulfate, , a side-product insoluble in liquid ammonia, is removed by filtration; the liquid ammonia is evaporated to give the desired product.
The net reaction is:
A base then frees the hydroxylamine from the salt: | 0 | Theoretical and Fundamental Chemistry |
Laying a firehose up a stairwell takes time, and this time is saved by having fixed hose outlets already in place. There is also a tendency for heavy wet hoses to slide downward when placed on an incline (such as the incline seen in a stairwell), whereas standpipes do not move. The use of standpipes keeps stairwells clear and is safer for exiting occupants.
Standpipes go in a direct up and down direction rather than looping around the stairwell, greatly reducing the length and thus the loss of water pressure due to friction loss. Additionally, standpipes are rigid and do not kink, which can occur when a firehose is improperly laid on a stairwell.
Standpipe systems also provide a level of redundancy, should the main water distribution system within a building fail or be otherwise compromised by a fire or explosion. | 1 | Applied and Interdisciplinary Chemistry |
For a simple overview of the development of ARBs, see figure 3.
Because of saralasin, the first Ang II antagonist, and the development of the first ACE inhibitor captopril, it was generally acknowledged that Ang II receptor antagonists might be promising as effective antihypertensive agents.
Saralasin was developed in the early 1970s and is an octapeptide analogue of Ang II, where the amino acids Asp, Ile and Phe have been replaced with Ser, Val and Ala, respectively. Saralasin was not orally bioavailable, had short duration of action and showed partial agonist activity and therefore it was not suitable as a drug.
Thus the goal was to develop a smaller nonpeptide substance with similar inhibition and binding features. At this time, a group at DuPont had already started the screening of nonpeptide mimics of Ang II using existing substances from chemical libraries.
Research investigators at Takeda discovered in 1982 the weak nonpeptide Ang II antagonists S-8307 and S-8308 from a group of 1-benzylimidazole-5-acetic acid derivatives. S-8307 and S-8308 have moderate potency, short duration of action and limited oral bioavailability, however they are selective and competitive AT receptor antagonists without partial agonist activity. A group at DuPont postulated that both Ang II and the Takeda leads were bound at the same receptor site. These two substances served as lead compounds for further optimization of AT receptor blockers.
Using nuclear magnetic resonance studies on the spatial structure of Ang II, scientists at DuPont discovered that the Takeda structures had to be enlarged at a particular position to resemble more closely the much larger peptide Ang II.
Computer modeling was used to compare S-8308 and S-8307 with Ang II and it was seen that Ang II contains two acidic residues near the NH terminus. These groups were not mimicked by the Takeda leads and therefore it was hypothesized that acidic functional groups would have to be added to the compounds.<br />
The 4-carboxy-derivative EXP-6155 had a binding activity which was ten-fold greater than that of S-8308 which further strengthened this hypothesis.
By replacing the 4-carboxy-group with a 2-carboxy-benzamido-moiety the compound EXP-6803 was synthesized. It had highly increased binding affinity but was only active when administered intravenously.
Replacing the 2-carboxy-benzamido-group with a 2-carboxy-phenyl-group created the lipophilic biphenyl-containing EXP-7711, which exhibited good oral activity but slightly less affinity for the AT receptor. <br />
Then the polar carboxyl group was replaced with a more lipophilic tetrazole group in order to increase oral bioavailability and duration of action further and the compound thus formed was named losartan. This development took place in 1986 and losartan became the first successful Ang II antagonist drug, approved as such in the United States in 1995 and was marketed by Merck.
This development was an extensive program and it is estimated that the process from the Takeda structures to the final substance, losartan, took more than fifty person-years of work in biological testing and chemical modifications. This represents an excellent investment given that a recent study estimated that losartan administration in the European union may reduce health care provision costs by 2.5 billion euro over 3.5 years.
Using a different lead, optimization from S-8308, eprosartan was developed by SmithKline Beecham in 1992. Eprosartan does not have a biphenyl-methyl structure but in order to mimic the C-terminal end of Ang II the 5-acetic acid group was replaced with an a-thienylacrylic acid and a 4-carboxy-moiety. Eprosartan is a selective, potent and competitive AT antagonist and its binding to AT receptors is rapid, reversible, saturable and of high affinity. | 1 | Applied and Interdisciplinary Chemistry |
An allomone is any chemical substance released by an individual of one species that affects the behavior of a member of another species to the benefit of the originator but not the receiver. Production of allomones is a common form of defense, such as by plant species against insect herbivores or prey species against predators. Sometimes species produce the sex pheromones of the organisms they exploit as prey or pollinators (such as bolas spiders and some orchids). Male sex pheromone of Dacini fruit flies, besides acting as aggregation pheromone to form lek, also acts as an allomone to deter lizard predation. The term "Allomone" was proposed by Brown, Eisner, and Whittaker to denote those substances which confer an advantage upon the emitter. | 1 | Applied and Interdisciplinary Chemistry |
Many plants or plant parts contain chemicals from the naturally colored anthocyanin family of compounds. They are red in acidic solutions and blue in basic. Anthocyanins can be extracted with water or other solvents from a multitude of colored plants and plant parts, including from leaves (red cabbage); flowers (geranium, poppy, or rose petals); berries (blueberries, blackcurrant); and stems (rhubarb). Extracting anthocyanins from household plants, especially red cabbage, to form a crude pH indicator is a popular introductory chemistry demonstration.
Litmus, used by alchemists in the Middle Ages and still readily available, is a naturally occurring pH indicator made from a mixture of lichen species, particularly Roccella tinctoria. The word litmus is literally from colored moss in Old Norse (see Litr). The color changes between red in acid solutions and blue in alkalis. The term litmus test has become a widely used metaphor for any test that purports to distinguish authoritatively between alternatives.
Hydrangea macrophylla flowers can change color depending on soil acidity. In acid soils, chemical reactions occur in the soil that make aluminium available to these plants, turning the flowers blue. In alkaline soils, these reactions cannot occur and therefore aluminium is not taken up by the plant. As a result, the flowers remain pink.
Another natural pH indicator is the spice turmeric. It turns yellow when exposed to acids and reddish brown when in presence of an alkalis. | 0 | Theoretical and Fundamental Chemistry |
The retinoblastoma protein is involved in the growth and development of mammalian hair cells of the cochlea, and appears to be related to the cells' inability to regenerate. Embryonic hair cells require pRb, among other important proteins, to exit the cell-cycle and stop dividing, which allows maturation of the auditory system. Once wild-type mammals have reached adulthood, their cochlear hair cells become incapable of proliferation. In studies where the gene for pRb is deleted in mice cochlea, hair cells continue to proliferate in early adulthood. Though this may seem to be a positive development, pRb-knockdown mice tend to develop severe hearing loss due to degeneration of the organ of Corti. For this reason, pRb seems to be instrumental for completing the development of mammalian hair cells and keeping them alive. However, it is clear that without pRb, hair cells have the ability to proliferate, which is why pRb is known as a tumor suppressor. Temporarily and precisely turning off pRb in adult mammals with damaged hair cells may lead to propagation and therefore successful regeneration. Suppressing function of the retinoblastoma protein in the adult rat cochlea has been found to cause proliferation of supporting cells and hair cells. pRb can be downregulated by activating the sonic hedgehog pathway, which phosphorylates the proteins and reduces gene transcription. | 1 | Applied and Interdisciplinary Chemistry |
*The main criticism applied to the yeast two-hybrid screen of protein–protein interactions are the possibility of a high number of false positive (and false negative) identifications. The exact rate of false positive results is not known, but earlier estimates were as high as 70%. This also, partly, explains the often found very small overlap in results when using a (high throughput) two-hybrid screening, especially when using different experimental systems.
The reason for this high error rate lies in the characteristics of the screen:
*Certain assay variants overexpress the fusion proteins which may cause unnatural protein concentrations that lead to unspecific (false) positives.
*The hybrid proteins are fusion proteins; that is, the fused parts may inhibit certain interactions, especially if an interaction takes place at the N-terminus of a test protein (where the DNA-binding or activation domain is typically attached).
*An interaction may not happen in yeast, the typical host organism for Y2H. For instance, if a bacterial protein is tested in yeast, it may lack a chaperone for proper folding that is only present in its bacterial host. Moreover, a mammalian protein is sometimes not correctly modified in yeast (e.g., missing phosphorylation), which can also lead to false results.
*The Y2H takes place in the nucleus. If test proteins are not localized to the nucleus (because they have other localization signals) two interacting proteins may be found to be non-interacting.
*Some proteins might specifically interact when they are co-expressed in the yeast, although in reality they are never present in the same cell at the same time. However, in most cases it cannot be ruled out that such proteins are indeed expressed in certain cells or under certain circumstances.
Each of these points alone can give rise to false results. Due to the combined effects of all error sources yeast two-hybrid have to be interpreted with caution. The probability of generating false positives means that all interactions should be confirmed by a high confidence assay, for example co-immunoprecipitation of the endogenous proteins, which is difficult for large scale protein–protein interaction data. Alternatively, Y2H data can be verified using multiple Y2H variants or bioinformatics techniques. The latter test whether interacting proteins are expressed at the same time, share some common features (such as gene ontology annotations or certain network topologies), have homologous interactions in other species. | 1 | Applied and Interdisciplinary Chemistry |
The concentration entrance length describes the length needed for the concentration profile in a flow to be fully developed. The concentration entrance length can be determined by relating it to the hydrodynamic entrance length with the Schmidt number or by experimental techniques. The Schmidt number describes the ratio of momentum diffusivity to mass diffusivity.
where
* is the concentration entrance length,
* is the pipe inner diameter,
* is the Reynolds number (based on the pipe diameter), and
* is the Schmidt number. | 1 | Applied and Interdisciplinary Chemistry |
The FDA approved Phase I clinical trials on thalassemia major patients in the US for 10 participants in July. The study was expected to continue until 2015.
In July 2012, the European Medicines Agency recommended approval of a gene therapy treatment for the first time in either Europe or the United States. The treatment used Alipogene tiparvovec (Glybera) to compensate for lipoprotein lipase deficiency, which can cause severe pancreatitis. The recommendation was endorsed by the European Commission in November 2012, and commercial rollout began in late 2014. Alipogene tiparvovec was expected to cost around $1.6 million per treatment in 2012, revised to $1 million in 2015, making it the most expensive medicine in the world at the time. , only the patients treated in clinical trials and a patient who paid the full price for treatment have received the drug.
In December 2012, it was reported that 10 of 13 patients with multiple myeloma were in remission "or very close to it" three months after being injected with a treatment involving genetically engineered T cells to target proteins NY-ESO-1 and LAGE-1, which exist only on cancerous myeloma cells. | 1 | Applied and Interdisciplinary Chemistry |
Any two state system can be modeled as a two-level atom. This leads to many systems being described as an "Artificial Atom". For instance a superconducting loop which can create a magnetic flux passing through it can act as an artificial atom as the current can induce a magnetic flux in either direction through the loop depending on whether the current is clockwise or counterclockwise.
The hamiltonian for this system is described as where .
This models the dipole interaction of the atom with a 1-D electromagnetic wave.
It is easy to see that this is truly analogous to a real two-level atom due to the fact that the fluorescence appears in the spectrum as the Mollow triplet, precisely like a true two-level atom.
These artificial atoms are often used to explore the phenomena of quantum coherence. This allows for the study of squeezed light which is known for creating more precise measurements. It is difficult to explore the resonance fluorescence of squeezed light in a typical two-level atom as all modes of the electromagnetic field must be squeezed which cannot easily be accomplished. In an artificial atom, the number of possible modes of the field is significantly limited allowing for easier study of squeezed light. In 2016 D.M. Toyli et al., performed an experiment in which two superconducting parametric amplifiers were used to generate squeezed light and then detect resonance fluorescence in artificial atoms from the squeezed light. Their results agreed strongly with the theory describing the phenomena. The implication of this study is it allows for resonance fluorescence to assist in qubit readout for squeezed light. The qubit used in the study was an aluminum transmon circuit that was then coupled to a 3-D aluminum cavity. Extra silicon chips were introduced to the cavity to assist in the tuning of resonance to that of the cavity. The majority of the detuning that did occur was a result of the degeneration of the qubit over time. | 0 | Theoretical and Fundamental Chemistry |
In the first case, two solid plates are placed in a solution of rigid spherical macromolecules. If the distance between two plates, , is smaller than the diameter of solute molecules, , then no solute can enter between the plates. This results in pure solvent existing between the plates. The difference in concentration of macromolecules in the solution between the plates and the bulk solution causes a force equal to the osmotic pressure to act on the plates. In a very dilute and monodisperse solution the force is defined by
where is the force, and is the total number of solute molecules. The force causes the entropy of the macromolecules to increase and is attractive when | 0 | Theoretical and Fundamental Chemistry |
The annealing temperature has a dramatic influence on the rate of recrystallization which is reflected in the above equations. However, for a given temperature there are several additional factors that will influence the rate.
The rate of recrystallization is heavily influenced by the amount of deformation and, to a lesser extent, the manner in which it is applied. Heavily deformed materials will recrystallize more rapidly than those deformed to a lesser extent. Indeed, below a certain deformation recrystallization may never occur. Deformation at higher temperatures will allow concurrent recovery and so such materials will recrystallize more slowly than those deformed at room temperature e.g. contrast hot and cold rolling. In certain cases deformation may be unusually homogeneous or occur only on specific crystallographic planes. The absence of orientation gradients and other heterogeneities may prevent the formation of viable nuclei. Experiments in the 1970s found that molybdenum deformed to a true strain of 0.3, recrystallized most rapidly when tensioned and at decreasing rates for wire drawing, rolling and compression (Barto & Ebert 1971).
The orientation of a grain and how the orientation changes during deformation influence the accumulation of stored energy and hence the rate of recrystallization. The mobility of the grain boundaries is influenced by their orientation and so some crystallographic textures will result in faster growth than others.
Solute atoms, both deliberate additions and impurities, have a profound influence on the recrystallization kinetics. Even minor concentrations may have a substantial influence e.g. 0.004% Fe increases the recrystallization temperature by around 100 °C (Humphreys and Hatherly 2004). It is currently unknown whether this effect is primarily due to the retardation of nucleation or the reduction in the mobility of grain boundaries i.e. growth. | 1 | Applied and Interdisciplinary Chemistry |
Faradaic efficiency of a cell design is usually measured through bulk electrolysis where a known quantity of reagent is stoichiometrically converted to product, as measured by the current passed. This result is then compared to the observed quantity of product measured through another analytical method. | 0 | Theoretical and Fundamental Chemistry |
RNA-targeting small molecules represent a class of small molecules, organic compounds with traditional drug properties (e.g., Lipinski's rule of five) that can bind to RNA secondary or tertiary structures and alter translation patterns, localization, and degradation. | 1 | Applied and Interdisciplinary Chemistry |
A pressure exchanger transfers pressure energy from a high pressure fluid stream to a low pressure fluid stream. Many industrial processes operate at elevated pressures and have high pressure waste streams. One way of providing a high pressure fluid to such a process is to transfer the waste pressure to a low pressure stream using a pressure exchanger.
One particularly efficient type of pressure exchanger is a rotary pressure exchanger. This device uses a cylindrical rotor with longitudinal ducts parallel to its rotational axis. The rotor spins inside a sleeve between two end covers. Pressure energy is transferred directly from the high pressure stream to the low pressure stream in the ducts of the rotor. Some fluid that remains in the ducts serves as a barrier that inhibits mixing between the streams. This rotational action is similar to that of an old fashioned machine gun firing high pressure bullets and it is continuously refilled with new fluid cartridges. The ducts of the rotor charge and discharge as the pressure transfer process repeats itself.
The performance of a pressure exchanger is measured by the efficiency of the energy transfer process and by the degree of mixing between the streams. The energy of the streams is the product of their flow volumes and pressures. Efficiency is a function of the pressure differentials and the volumetric losses (leakage) through the device computed with the following equation:
where Q is flow, P is pressure, L is leakage flow, HDP is high pressure differential, LDP is low pressure differential, the subscript B refers to the low pressure feed to the device and the subscript G refers to the high pressure feed to the device.
Mixing is a function of the concentrations of the species in the inlet streams and the ratio of flow volumes to the device. | 1 | Applied and Interdisciplinary Chemistry |
Classical thermodynamics is the description of the states of thermodynamic systems at near-equilibrium, that uses macroscopic, measurable properties. It is used to model exchanges of energy, work and heat based on the laws of thermodynamics. The qualifier classical reflects the fact that it represents the first level of understanding of the subject as it developed in the 19th century and describes the changes of a system in terms of macroscopic empirical (large scale, and measurable) parameters. A microscopic interpretation of these concepts was later provided by the development of statistical mechanics. | 0 | Theoretical and Fundamental Chemistry |
OCP was first described in 1981 by Holt and Krogmann who isolated it from the unicellular cyanobacterium Arthrospira maxima, although its function would remain obscure until 2006. The crystal structure of the OCP was reported in 2003. At the same time the protein was shown to be an effective quencher of singlet oxygen and was suggested to be involved in photoprotection, or carotenoid transport. In 2000, it was demonstrated that cyanobacteria could perform photoprotective fluorescence quenching independent of lipid phase transitions, differential transmembrane pH, and inhibitors. The action spectrum for this quenching process suggested the involvement of carotenoids, and the specific involvement of the OCP was later demonstrated by Kirilovsky and coworkers in 2006. In 2008, OCP was shown to require photoactivation by strong blue-green light for its photoprotective quenching function. Photoactivation is accompanied by a pronounced color change, from orange to red, which had been previously observed by Kerfeld et al in the initial structural studies. In 2015 a combination of biophysical methods by researchers in Berkeley showed that the visible color change is the consequence of a 12Å translocation of the [https://today.lbl.gov/2015/07/01/protein-shifts-more-than-just-color-for-cyanobacterial-photoprotection/ carotenoid]. | 0 | Theoretical and Fundamental Chemistry |
Minigenes were first described as the somatic assembly of DNA segments and consisted of DNA regions known to encode the protein and the flanking regions required to express the protein. The term was first used in a paper in 1977 to describe the cloning of two minigenes that were designed to express a peptide.
RNA splicing was discovered in the late 1970s through the study of adenoviruses that invade mammals and replicate inside them. Researchers identified RNA molecules that contained sequences from noncontiguous parts of the virus’s genome. This discovery led to the conclusion that regulatory mechanisms existed which affected mature RNA and the genes it expresses. Using minigenes as a splice reporting vector to explore the effects of RNA splicing regulation naturally followed and remains the major use of minigenes to date. | 1 | Applied and Interdisciplinary Chemistry |
Gay-Lussac's law states that:
Therefore,
* , or
* , or
:where P is the pressure, T is the absolute temperature, and k is another proportionality constant. | 0 | Theoretical and Fundamental Chemistry |
Ligands containing atomic chirality centers such asymmetric carbon, which usually do not have C-symmetry, remain important in catalysis. Examples include cinchona alkaloids and certain phosphoramidites. P-chiral monophosphines have also been investigated. | 0 | Theoretical and Fundamental Chemistry |
Climate change is likely to increase the frequency, intensity and duration of cyanobacterial blooms in many eutrophic lakes, reservoirs and estuaries. Bloom-forming cyanobacteria produce a variety of neurotoxins, hepatotoxins and dermatoxins, which can be fatal to birds and mammals (including waterfowl, cattle and dogs) and threaten the use of waters for recreation, drinking water production, agricultural irrigation and fisheries. Toxic cyanobacteria have caused major water quality problems, for example in Lake Taihu (China), Lake Erie (USA), Lake Okeechobee (USA), Lake Victoria (Africa) and the Baltic Sea.
Climate change favours cyanobacterial blooms both directly and indirectly. Many bloom-forming cyanobacteria can grow at relatively high temperatures. Increased thermal stratification of lakes and reservoirs enables buoyant cyanobacteria to float upwards and form dense surface blooms, which gives them better access to light and hence a selective advantage over nonbuoyant phytoplankton organisms. Protracted droughts during summer increase water residence times in reservoirs, rivers and estuaries, and these stagnant warm waters can provide ideal conditions for cyanobacterial bloom development.
The capacity of the harmful cyanobacterial genus Microcystis to adapt to elevated CO levels was demonstrated in both laboratory and field experiments. Microcystis spp. take up CO and and accumulate inorganic carbon in carboxysomes, and strain competitiveness was found to depend on the concentration of inorganic carbon. As a result, climate change and increased CO levels are expected to affect the strain composition of cyanobacterial blooms. | 0 | Theoretical and Fundamental Chemistry |
Cefalexin is a β-lactam antibiotic of the cephalosporin family. It is bactericidal and acts by inhibiting synthesis of the peptidoglycan layer of the bacterial cell wall. As cefalexin closely resembles d-alanyl-d-alanine, an amino acid ending on the peptidoglycan layer of the cell wall, it is able to irreversibly bind to the active site of PBP, which is essential for the synthesis of the cell wall. It is most active against gram-positive cocci, and has moderate activity against some gram-negative bacilli. However, some bacterial cells have the enzyme β-lactamase, which hydrolyzes the β-lactam ring, rendering the drug inactive. This contributes to antibacterial resistance towards cefalexin. | 0 | Theoretical and Fundamental Chemistry |
The term operando first appeared in catalytic literature in 2002. It was coined by Miguel A. Bañares, who sought to name the methodology in a way that captured the idea of observing a functional material — in this case a catalyst — under actual working, i.e. device operation, conditions. The first international congress on operando spectroscopy took place in Lunteren, Netherlands, in March 2003, followed by further conferences in 2006 (Toledo, Spain),2009 (Rostock, Germany), 2012 (Brookhaven, USA), and 2015 (Deauville, France). The name change from in situ to operando for the research field of spectroscopy of catalysts under working conditions was proposed at the Lunteren congress.
The analytical principle of measuring the structure, property and function of a material, a component disassembled or as part of a device simultaneously under operation conditions is not restricted to catalysis and catalysts. Batteries and fuel cells have been subject to operando studies with respect to their electrochemical function. | 0 | Theoretical and Fundamental Chemistry |
A major limitation of classical omic studies is the isolation of only one level of biological complexity. For example, transcriptomic studies may provide information at the transcript level, but many different entities contribute to the biological state of the sample (genomic variants, post-translational modifications, metabolic products, interacting organisms, among others). With the advent of high-throughput biology, it is becoming increasingly affordable to make multiple measurements, allowing transdomain (e.g. RNA and protein levels) correlations and inferences. These correlations aid the construction or more complete biological networks, filling gaps in our knowledge.
Integration of data, however, is not an easy task. To facilitate the process, groups have curated database and pipelines to systematically explore multiomic data:
*Multi-Omics Profiling Expression Database (MOPED), integrating diverse animal models,
* The Pancreatic Expression Database, integrating data related to pancreatic tissue,
* [http://www.linkedomics.org/ LinkedOmics], connecting data from TCGA cancer datasets,
* OASIS, a web-based resource for general cancer studies,
* BCIP, a platform for breast cancer studies,
* C/VDdb, connecting data from several cardiovascular disease studies,
* ZikaVR, a multiomic resource for Zika virus data
* Ecomics, a normalized multi-omic database for Escherichia coli data,
* GourdBase, integrating data from studies with gourd,
* MODEM, a database for multilevel maize data,
* SoyKB, a database for multilevel soybean data,
*[https://www.proteomicsdb.org/ ProteomicsDB], a multi-omics and multi-organism resource for life science research | 1 | Applied and Interdisciplinary Chemistry |
In 1772, the chemist Joseph Priestley carried out a series of experiments relating to the gases involved in respiration and combustion. In his first experiment, he lit a candle and placed it under an upturned jar. After a short period of time, the candle burned out. He carried out a similar experiment with a mouse in the confined space of the burning candle. He found that the mouse died a short time after the candle had been extinguished. However, he could revivify the foul air by placing green plants in the area and exposing them to light. Priestley's observations were some of the first experiments that demonstrated the activity of a photosynthetic reaction center.
In 1779, Jan Ingenhousz carried out more than 500 experiments spread out over 4 months in an attempt to understand what was really going on. He wrote up his discoveries in a book entitled Experiments upon Vegetables. Ingenhousz took green plants and immersed them in water inside a transparent tank. He observed many bubbles rising from the surface of the leaves whenever the plants were exposed to light. Ingenhousz collected the gas that was given off by the plants and performed several different tests in attempt to determine what the gas was. The test that finally revealed the identity of the gas was placing a smouldering taper into the gas sample and having it relight. This test proved it was oxygen, or, as Joseph Priestley had called it, de-phlogisticated air.
In 1932, Robert Emerson and his student, William Arnold, used a repetitive flash technique to precisely measure small quantities of oxygen evolved by chlorophyll in the algae Chlorella. Their experiment proved the existence of a photosynthetic unit. Gaffron and Wohl later interpreted the experiment and realized that the light absorbed by the photosynthetic unit was transferred. This reaction occurs at the reaction center of Photosystem II and takes place in cyanobacteria, algae and green plants. | 0 | Theoretical and Fundamental Chemistry |
A material's flash point is a metric of how easy it is to ignite the vapor of the material as it evaporates into the atmosphere. It is defined as the lowest material temperature required for fuel oils in the materials to begin to give off flammable vapors in the quantity high enough to support a flash of fire when ignited by an external source. A lower flash point indicates higher flammability. Materials with flash points below are regulated in the United States by OSHA as potential workplace hazards. | 0 | Theoretical and Fundamental Chemistry |
Whether a process can occur spontaneously depends not only on the enthalpy change but also on the entropy change () and absolute temperature . If a process is a spontaneous process at a certain temperature, the products have a lower Gibbs free energy than the reactants (an exergonic process), even if the enthalpy of the products is higher. Thus, an endothermic process usually requires a favorable entropy increase () in the system that overcomes the unfavorable increase in enthalpy so that still . While endothermic phase transitions into more disordered states of higher entropy, e.g. melting and vaporization, are common, spontaneous chemical processes at moderate temperatures are rarely endothermic. The enthalpy increase in a hypothetical strongly endothermic process usually results in , which means that the process will not occur (unless driven by electrical or photon energy). An example of an endothermic and exergonic process is | 0 | Theoretical and Fundamental Chemistry |
A supersolid is a special quantum state of matter where particles form a rigid, spatially ordered structure, but also flow with zero viscosity. This is in contradiction to the intuition that flow, and in particular superfluid flow with zero viscosity, is a property exclusive to the fluid state, e.g., superconducting electron and neutron fluids, gases with Bose–Einstein condensates, or unconventional liquids such as helium-4 or helium-3 at sufficiently low temperature. For more than 50 years it was thus unclear whether the supersolid state can exist. | 0 | Theoretical and Fundamental Chemistry |
Other experiments carried out in the physics of plasmas have also highlighted the emergence of Peregrine solitons in other fields ruled by the nonlinear Schrödinger equation. | 1 | Applied and Interdisciplinary Chemistry |
OCO-3 is constructed from spare equipment from the OCO-2 mission. Thus its physical characteristics are similar, but with some adaptations. A 2-axis pointing mirror was added, which will allow targeting of cities and other areas on order of for area mapping (also called "snapshot mode"). A resolution context camera was also added. An onboard cryocooler will maintain detector temperatures of around . Entrance optics were modified to maintain a similar ground footprint to OCO-2.
Similar to OCO and OCO-2, the main measurement will be of reflected near-IR sunlight. Grating spectrometers separate incoming light energy into different components of the electromagnetic spectrum (or wavelengths or "colors"). Because and molecular oxygen absorb light at specific wavelengths, the signal or absorption levels at different wavelengths provide information on the amount of gases. Three bands are used called Weak (around 1.6 μm), Strong (around 2.0 μm), and Oxygen-A (around 0.76 μm). There are 1,016 spectral elements per band, and measurements are made simultaneously at 8 side-by-side locations or "footprints" each about or smaller, 3 times per second. | 1 | Applied and Interdisciplinary Chemistry |
Achinewhu married Eunice Achinewhu (nee Eunice Nyema Otto) in 1972 and they have four children.
He is a reverend canon of the Church of Nigeria Anglican Communion. He is a crown of peace, justice of peace, and the national president of Peace Builders Association (Council of Ambassadors for Peace and Unification) | 1 | Applied and Interdisciplinary Chemistry |
As the Sverdrup balance argues, subtropical ocean gyres have a weak equatorward flow and subpolar ocean gyres have a weak poleward flow over most of their area. However, there must be some return flow that goes against the Sverdrup transport in order to preserve mass balance. In this respect, the Sverdrup solution is incomplete, as it has no mechanism in which to predict this return flow. Contributions by both Henry Stommel and Walter Munk resolved this issue by showing that the return flow of gyres is done through an intensified western boundary current. Stommel's solution relies on a frictional bottom boundary layer which is not necessarily physical in a stratified ocean (currents do not always extend to the bottom).
Munk's solution instead relies on friction between the return flow and the sidewall of the basin. This allows for two cases: one with the return flow on the western boundary (western boundary current) and one with the return flow on the eastern boundary (eastern boundary current). A qualitative argument for the presence of western boundary current solutions over eastern boundary current solutions can be found again through the conservation of potential vorticity. Considering again the case of a subtropical northern hemisphere gyre, the return flow must be northward. In order to move northward (an increase in planetary vorticity ), there must be a source of positive relative vorticity to the system. The relative vorticity in the shallow-water system is:
Here is again the meridional velocity and is the zonal velocity. In the sense of a northward return flow, the zonal component is neglected and only the meridional velocity is important for relative vorticity. Thus, this solution requires that in order to increase the relative vorticity and have a valid northward return flow in the northern hemisphere subtropical gyre.
Due to friction at the boundary, the velocity of flow must go to zero at the sidewall before reaching some maximum northward velocity within the boundary layer and decaying to the southward Sverdrup transport solution far away from the boundary. Thus, the condition that can only be satisfied through a western boundary frictional layer, as the eastern boundary frictional layer forces . One can make similar arguments for subtropical gyres in the southern hemisphere and for subpolar gyres in either hemisphere and see that the result remains the same: the return flow of an ocean gyre is always in the form of a western boundary current.
The western boundary current must transport on the same order of water as the interior Sverdrup transport in a much smaller area. This means western boundary currents are much stronger than interior currents, a phenomenon called "western intensification". | 1 | Applied and Interdisciplinary Chemistry |
The FASN gene has been investigated as a possible oncogene. FAS is upregulated in breast and gastric cancers, as well as being an indicator of poor prognosis, and so may be worthwhile as a chemotherapeutic target. FAS inhibitors are therefore an active area of drug discovery research.
FAS may also be involved in the production of an endogenous ligand for the nuclear receptor PPARalpha, the target of the fibrate drugs for hyperlipidemia, and is being investigated as a possible drug target for treating the metabolic syndrome. Orlistat which is a gastrointestinal lipase inhibitor also inhibits FAS and has a potential as a medicine for cancer.
In some cancer cell lines, this protein has been found to be fused with estrogen receptor alpha (ER-alpha), in which the N-terminus of FAS is fused in-frame with the C-terminus of ER-alpha.
An association with uterine leiomyomata has been reported. | 1 | Applied and Interdisciplinary Chemistry |
The Hamiltonian formulation can be derived from Luke's Lagrangian description by using Leibniz integral rule on the integral of :
with the value of the velocity potential at the free surface, and the Hamiltonian density — sum of the kinetic and potential energy density — and related to the Hamiltonian as:
The Hamiltonian density is written in terms of the surface potential using Green's third identity on the kinetic energy:
where is equal to the normal derivative of at the free surface. Because of the linearity of the Laplace equation — valid in the fluid interior and depending on the boundary condition at the bed and free surface — the normal derivative is a linear function of the surface potential , but depends non-linear on the surface elevation . This is expressed by the Dirichlet-to-Neumann operator , acting linearly on .
The Hamiltonian density can also be written as:
with the vertical velocity at the free surface . Also is a linear function of the surface potential through the Laplace equation, but depends non-linear on the surface elevation :
with operating linear on , but being non-linear in . As a result, the Hamiltonian is a quadratic functional of the surface potential . Also the potential energy part of the Hamiltonian is quadratic. The source of non-linearity in surface gravity waves is through the kinetic energy depending non-linear on the free surface shape .
Further is not to be mistaken for the horizontal velocity at the free surface:
Taking the variations of the Lagrangian with respect to the canonical variables and gives:
provided in the fluid interior satisfies the Laplace equation, , as well as the bottom boundary condition at and at the free surface. | 1 | Applied and Interdisciplinary Chemistry |
Lute (from Latin Lutum, meaning mud, clay etc.) was a substance used to seal and affix apparatus employed in chemistry and alchemy, and to protect component vessels against heat damage by fire; it was also used to line furnaces. Lutation was thus the act of "cementing vessels with lute".
In pottery, luting is a technique for joining pieces of unfired leather-hard clay together, using a wet clay slip or slurry as adhesive. The complete object is then fired. Large objects are often built up in this way, for example the figures of the Terracotta Army in ancient China. The edges being joined might be scored or cross-hatched to promote adhesion, but clay and water are the only materials used. | 1 | Applied and Interdisciplinary Chemistry |
The bacterial flagellar motor has been proposed to follow a dissipative allosteric model, where ultrasensitivity comes as a combination of protein binding affinity and energy contributions from the proton motive force (see Flagellar motors and chemotaxis below). | 1 | Applied and Interdisciplinary Chemistry |
The P element has found wide use in Drosophila research as a mutagen. The mutagenesis system typically uses an autonomous but immobile element, and a mobile nonautonomous element. Flies from subsequent generations can then be screened by phenotype or PCR. Naturally-occurring P elements contain coding sequence for the enzyme transposase and recognition sequences for transposase action. Transposase regulates and catalyzes the excision of a P element from the host DNA, cutting at the two recognition sites, and then reinserting randomly. It is the random insertion that may interfere with existing genes, or carry an additional gene, that can be used for genetic research.
To use this as a useful and controllable genetic tool, the two parts of the P element must be separated to prevent uncontrolled transposition. The normal genetic tools are DNA coding for transposase with no transposase recognition sequences so it cannot insert and a "P Plasmid". P Plasmids always contain a Drosophila reporter gene, often a red-eye marker (the product of the white gene), and transposase recognition sequences. They may contain a gene of interest, an E. coli selectable marker gene, often some kind of antibiotic resistance, an origin of replication or other associated plasmid "housekeeping" sequences. | 1 | Applied and Interdisciplinary Chemistry |
A transposable element (TE, transposon, or jumping gene) is a nucleic acid sequence in DNA that can change its position within a genome, sometimes creating or reversing mutations and altering the cells genetic identity and genome size. Transposition often results in duplication of the same genetic material. In the human genome, L1 and Alu elements are two examples. Barbara McClintocks discovery of them earned her a Nobel Prize in 1983. Its importance in personalized medicine is becoming increasingly relevant, as well as gaining more attention in data analytics given the difficulty of analysis in very high dimensional spaces.
Transposable elements make up a large fraction of the genome and are responsible for much of the mass of DNA in a eukaryotic cell. Although TEs are selfish genetic elements, many are important in genome function and evolution. Transposons are also very useful to researchers as a means to alter DNA inside a living organism.
There are at least two classes of TEs: Class I TEs or retrotransposons generally function via reverse transcription, while Class II TEs or DNA transposons encode the protein transposase, which they require for insertion and excision, and some of these TEs also encode other proteins. | 1 | Applied and Interdisciplinary Chemistry |
For modeling of the glass flow in a glass melting furnace the finite element method is applied commercially, based on data or models for viscosity, density, thermal conductivity, heat capacity, absorption spectra, and other relevant properties of the glass melt. The finite element method may also be applied to glass forming processes. | 0 | Theoretical and Fundamental Chemistry |
There have been a number of reported procedures which take advantage of a chemical reagent/catalyst to perform racemization of the starting material and an enzyme to selectively react with one enantiomer, called chemoenzymatic dynamic kinetic resolutions. PSL-C was utilized along with a ruthenium catalyst (for racemization) to produce enantiopure (>95% ee) δ-hydroxylactones.
More recently, secondary alcohols have been resolved by Bäckvall with yields up to 99% and ee's up to >99% utilizing CALB and a ruthenium racemization complex.
A second type of chemoenzymatic dynamic kinetic resolution involves a π-allyl complex from an allylic acetate with palladium. Here, racemization occurs with loss of the acetate, forming a cationic complex with the transition metal center, as shown below. Palladium has been shown to facilitate this reaction, while ruthenium has been shown to affect a similar reaction, also shown below. | 0 | Theoretical and Fundamental Chemistry |
Cellular metabolism is represented by a large number of metabolic reactions involving the conversion of the carbon source (usually glucose) into the building blocks needed for macromolecular biosynthesis. These reactions form metabolic networks within cells. These networks can then be used to study metabolism within cells.
To allow these networks to interact, a tight connection between them is necessary. This connection is provided by usage of common cofactors such as ATP, ADP, NADH and NADPH. In addition to this, sharing of some metabolites between the different networks further tightens the connections between the different networks. | 1 | Applied and Interdisciplinary Chemistry |
Alliance Medical and Siemens Healthcare are the only producers in the United Kingdom. A dose of FDG in England costs about £130. In Northern Ireland, where there is a single supplier, doses cost up to £450. IBA Molecular North America and Zevacor Molecular, both of which are owned by Illinois Health and Science (IBAM having been purchased as of 1 August 2015), Siemens' PETNET Solutions (a subsidiary of Siemens Healthcare), and Cardinal Health are producers in the U.S. | 1 | Applied and Interdisciplinary Chemistry |
The retromer complex is highly conserved: homologs have been found in C. elegans, mouse and human. The retromer complex consists of 5 proteins in yeast: Vps35p, Vps26p, Vps29p, Vps17p, Vps5p. The mammalian retromer consists of Vps26, Vps29, Vps35, SNX1 and SNX2, and possibly SNX5 and SNX6. It is proposed to act in two subcomplexes: (1) A cargo recognition heterotrimeric complex that consist of Vps35, Vps29 and Vps26, and (2) SNX-BAR dimers, which consist of SNX1 or SNX2 and SNX5 or SNX6 that facilitate endosomal membrane remodulation and curvature, resulting in the formation of tubules/vesicles that transport cargo molecules to the trans-golgi network (TGN). Humans have two orthologs of VPS26: VPS26A, which is ubiquitous, and VPS26B, which is found in the central nervous system, where it forms a unique retromer that is dedicated to direct recycling of neuronal cell surface proteins such as APP back to the plasma membrane with the assistance of the cargo receptor SORL1. | 1 | Applied and Interdisciplinary Chemistry |
Recently, photoredox catalysis has been applied to biocatalysis, enabling unique, previously inaccessible transformations. Photoredox chemistry relies upon light to generate free radical intermediates. These radical intermediates are achiral thus racemic mixtures of product are obtained when no external chiral environment is provided. Enzymes can provide this chiral environment within the active site and stabilize a particular conformation and favoring formation of one, enantiopure product. Photoredox enabled biocatalysis reactions fall into two categories:
# Internal coenzyme/cofactor photocatalyst
# External photocatalyst
Certain common hydrogen atom transfer (HAT) cofactors (NADPH and Flavin) can operate as single electron transfer (SET) reagents. Although these species are capable of HAT without irradiation, their redox potentials are enhance by nearly 2.0 V upon visible light irradiation. When paired with their respective enzymes (typically ene-reductases) This phenomenon has been utilized by chemists to develop enantioselective reduction methodologies. For example medium sized lactams can be synthesized in the chiral environment of an ene-reductase through a reductive, baldwin favored, radical cyclization terminated by enantioselective HAT from NADPH.
The second category of photoredox enabled biocatalytic reactions use an external photocatalyst (PC). Many types of PCs with a large range of redox potentials can be utilized, allowing for greater tunability of reactive compared to using a cofactor. Rose bengal, and external PC, was utilized in tandem with an oxidoreductase to enantioselectively deacylate medium sized alpha-acyl-ketones.
Using an external PC has some downsides. For example, external PCs typically complicate reaction design because the PC may react with both the bound and unbound substrate. If a reaction occurs between the unbound substrate and the PC, enantioselectivity is lost and other side reactions may occur. | 0 | Theoretical and Fundamental Chemistry |
Contact angle, the angle at which a liquid droplet meets at a solid surface, is another way to characterize polymer surfaces. Contact angle (θ) is a measure of the wetting ability of the liquid on a solid surface. Generally, due to low surface energy, liquids will not wet polymer surfaces and the contact angle will be greater than 90°. The liquid molecules are more attracted to other liquid molecules as compared to the polymer surface. Because the polymer surfaces are solid surfaces, surface tension cannot be measured in a traditional way such as using a Wilhelmy plate. Instead, contact angles can be used to indirectly estimate the surface tension of polymer surfaces. This is accomplished by measuring the contact angles of a series of liquids on a polymer surface. A Fox and Zisman plot of cos θ versus surface tensions of the liquids(γ) gives a straight line which can be extrapolated back to determine the critical surface tension of the solid (γ).
Where:
: is the contact angle
: is the surface tension of the liquid
: is the critical surface tension of the solid
The variable β was previously determined to be approximately 0.03 to 0.04. While the actual surface tension of the solid polymer surface cannot be determined, the Fox and Zisman plot serves as an estimate. However, this estimate may be skewed if there are significant intermolecular forces between the surface and the liquid. Also, this plot is not applicable for binary mixtures of liquids dropped onto a polymer surface. Some estimated surface tensions of different polymers and the contact angles of different liquids on polymer surfaces is shown below. | 0 | Theoretical and Fundamental Chemistry |
All family members are capable of catalyzing the hydrolysis of PIP, a phosphatidylinositol at the inner leaflet of the plasma membrane into the two second messengers, inositol trisphosphate (IP) and diacylglycerol (DAG).
The chemical reaction may be expressed as:
:1-phosphatidyl-1-myo-inositol 4,5-bisphosphate + HO -myo-inositol 1,4,5-trisphosphate + diacylglycerol
PLCs catalyze the reaction in two sequential steps. The first reaction is a phosphotransferase step that involves an intramolecular attack between the hydroxyl group at the 2 position on the inositol ring and the adjacent phosphate group resulting in a cyclic IP intermediate. At this point, DAG is generated. However, in the second phosphodiesterase step, the cyclic intermediate is held within the active site long enough to be attacked by a molecule of water, resulting in a final acyclic IP product. It should be mentioned that bacterial forms of the enzyme, which contain only the catalytic lipase domain, produce cyclic intermediates exclusively, whereas the mammalian isoforms generate predominantly the acyclic product. However, it is possible to alter experimental conditions (e.g., temperature, pH) in vitro' such that some mammalian isoforms will alter the degree to which they produce mixtures of cyclic/acyclic products along with DAG. This catalytic process is tightly regulated by reversible phosphorylation of different phosphoinositides and their affinity for different regulatory proteins. | 1 | Applied and Interdisciplinary Chemistry |
The detector used in a spectroradiometer is determined by the wavelength over which the light is being measured, as well as the required dynamic range and sensitivity of the measurements. Basic spectroradiometer detector technologies generally fall into one of three groups: photoemissive detectors (e.g. photomultiplier tubes), semiconductor devices (e.g. silicon), or thermal detectors (e.g. thermopile).
The spectral response of a given detector is determined by its core materials. For example, photocathodes found in photomultiplier tubes can be manufactured from certain elements to be solar-blind – sensitive to UV and non-responsive to light in the visible or IR.
CCD (Charge Coupled Device) arrays typically one dimensional (linear) or two dimensional (area) arrays of thousands or millions of individual detector elements (also known as pixels) and CMOS sensors. They include a silicon or InGaAs based multichannel array detector capable of measuring UV, visible and near-infra light.
CMOS (Complementary Metal Oxide Semiconductor) sensors differs from a CCD in that they add an amplifier to each photodiode. This is called an active pixel sensor because the amplifier is part of the pixel. Transistor switches connect each photodiode to the intrapixel amplifier at the time of readout. | 0 | Theoretical and Fundamental Chemistry |
Edward Frankland first reported the compound in 1848 from zinc and ethyl iodide, the first organozinc compound discovered. He improved the synthesis by using diethyl mercury as starting material. The contemporary synthesis consists of the reaction of a 1:1 mixture of ethyl iodide and ethyl bromide with a zinc-copper couple, a source of reactive zinc. | 0 | Theoretical and Fundamental Chemistry |
In 2019, Stephan and co-workers at the University of Toronto reported the first examples of di-vinyl-substituted diphosphenes via a ring opening/dimerization process from kinetically unstable 2H-phosphirenes. | 0 | Theoretical and Fundamental Chemistry |
* [http://www.math.ucsb.edu/~atzberg/SIB_Codes/index.html Stochastic Immersed Boundary Methods in 3D, P. Atzberger, UCSB]
* [http://www.math.nyu.edu/~griffith/IBAMR/ Immersed Boundary Method for Adaptive Meshes in 3D, B. Griffith, NYU.]
* [http://www.math.utah.edu/IBIS/ Immersed Boundary Method for Uniform Meshes in 2D, A. Fogelson, Utah]
* [https://www.tu-braunschweig.de/ifl/simulationswerkzeuge/ifls/ IFLS, IFL, TU Braunschweig] | 1 | Applied and Interdisciplinary Chemistry |
The Paternò–Büchi reaction, named after Emanuele Paternò and George Büchi, who established its basic utility and form, is a photochemical reaction, specifically a 2+2 photocycloaddition, which forms four-membered oxetane rings from an excited carbonyl and reacting with an alkene.
With substrates benzaldehyde and 2-methyl-2-butene the reaction product is a mixture of structural isomers:
Another substrate set is benzaldehyde and furan or heteroaromatic ketones and fluorinated alkenes.
The alternative strategy for the above reaction is called the Transposed Paternò−Büchi reaction. | 0 | Theoretical and Fundamental Chemistry |
In the 2017 Queens Birthday Honours, Brooker was appointed a Member of the New Zealand Order of Merit, for services to science. Later that year, she won the Hector Medal from the Royal Society of New Zealand. Also in 2017, Brooker was selected as one of the Royal Society Te Apārangis "150 women in 150 words", celebrating the contributions of women to knowledge in New Zealand.
Brooker was elected a Fellow of the Royal Society of New Zealand in 2007, and a Fellow of the Royal Society of Chemistry in 2011. She is also a Fellow of the New Zealand Institute of Chemistry. In October 2019, Brooker was appointed one of seven inaugural sesquicentennial distinguished chairs, or , at Otago University. She was awarded the University's Distinguished Research Medal in 2015. | 0 | Theoretical and Fundamental Chemistry |
Imiquimod (cardinally used in dermatology) is a TLR7 agonist, and its successor resiquimod, is a TLR7 and TLR8 agonist. Recently, resiquimod has been explored as an agent for cancer immunotherapy, acting through stimulation of tumor-associated macrophages.
Several TLR ligands are in clinical development or being tested in animal models as vaccine adjuvants, with the first clinical use in humans in a recombinant herpes zoster vaccine in 2017, which contains a monophosphoryl lipid A component.
TLR7 messenger RNA expression levels in dairy animals in a natural outbreak of foot-and-mouth disease have been reported.
TLR4 has been shown to be important for the long-term side-effects of opioids. Its activation leads to downstream release of inflammatory modulators including TNF-α and IL-1β, and constant low-level release of these modulators is thought to reduce the efficacy of opioid drug treatment with time, and is involved in opioid tolerance, hyperalgesia and allodynia. Morphine induced TLR4 activation attenuates pain suppression by opioids and enhances the development of opioid tolerance and addiction, drug abuse, and other negative side effects such as respiratory depression and hyperalgesia. Drugs that block the action of TNF-α or IL-1β have been shown to increase the analgesic effects of opioids and reduce the development of tolerance and other side-effects, and this has also been demonstrated with drugs that block TLR4 itself.
The "unnatural" enantiomers of opioid drugs such as (+)-morphine and (+)-naloxone lack affinity for opioid receptors, still produce the same activity at TLR4 as their "normal" enantiomers. So, "unnatural" entianomers of opioids such as (+)-naloxone, can be used to block the TLR4 activity of opioid analgesic drugs without having any affinity for μ-opioid receptor | 1 | Applied and Interdisciplinary Chemistry |
If the heat flux of a boiling system is higher than the critical heat flux (CHF) of the system, the bulk fluid may boil, or in some cases, regions of the bulk fluid may boil where the fluid travels in small channels. Thus large bubbles form, sometimes blocking the passage of the fluid. This results in a departure from nucleate boiling (DNB) in which steam bubbles no longer break away from the solid surface of the channel, bubbles dominate the channel or surface, and the heat flux dramatically decreases. Vapor essentially insulates the bulk liquid from the hot surface.
During DNB, the surface temperature must therefore increase substantially above the bulk fluid temperature in order to maintain a high heat flux. Avoiding the CHF is an engineering problem in heat transfer applications, such as nuclear reactors, where fuel plates must not be allowed to overheat. DNB may be avoided in practice by increasing the pressure of the fluid, increasing its flow rate, or by utilizing a lower temperature bulk fluid which has a higher CHF. If the bulk fluid temperature is too low or the pressure of the fluid is too high, nucleate boiling is however not possible.
DNB is also known as transition boiling, unstable film boiling, and partial film boiling. For water boiling as shown on the graph, transition boiling occurs when the temperature difference between the surface and the boiling water is approximately above the T. This corresponds to the high peak and the low peak on the boiling curve. The low point between transition boiling and film boiling is the Leidenfrost point.
During transition boiling of water, the bubble formation is so rapid that a vapor film or blanket begins to form at the surface. However, at any point on the surface, the conditions may oscillate between film and nucleate boiling, but the fraction of the total surface covered by the film increases with increasing temperature difference. As the thermal conductivity of the vapor is much less than that of the liquid, the convective heat transfer coefficient and the heat flux reduces with increasing temperature difference. | 1 | Applied and Interdisciplinary Chemistry |
Salt hydrates (MN·nHO)
*Advantages
** High volumetric latent heat storage capacity
** Availability and low cost
** Sharp melting point
** High thermal conductivity
** High heat of fusion
** Non-flammable
** Sustainability
* Disadvantages
** Difficult to prevent incongruent melting and phase separation upon cycling, which can cause a significant loss in latent heat enthalpy.
** Can be corrosive to many other materials, such as metals. This can be overcome by only using specific metal-PCM pairings or encapsulation in small quantities in non-reactive plastic.
** Change of volume is very high in some mixtures
** Super cooling can be a problem in solid–liquid transition, necessitating the use of nucleating agents which may become inoperative after repeated cycling | 0 | Theoretical and Fundamental Chemistry |
Hormone producing cells are found in the endocrine glands, such as the thyroid gland, ovaries, and testes. Hormonal signaling involves the following steps:
# Biosynthesis of a particular hormone in a particular tissue.
# Storage and secretion of the hormone.
# Transport of the hormone to the target cell(s).
# Recognition of the hormone by an associated cell membrane or intracellular receptor protein.
# Relay and amplification of the received hormonal signal via a signal transduction process: This then leads to a cellular response. The reaction of the target cells may then be recognized by the original hormone-producing cells, leading to a downregulation in hormone production. This is an example of a homeostatic negative feedback loop.
# Breakdown of the hormone.
Exocytosis and other methods of membrane transport are used to secrete hormones when the endocrine glands are signaled. The hierarchical model is an oversimplification of the hormonal signaling process. Cellular recipients of a particular hormonal signal may be one of several cell types that reside within a number of different tissues, as is the case for insulin, which triggers a diverse range of systemic physiological effects. Different tissue types may also respond differently to the same hormonal signal. | 1 | Applied and Interdisciplinary Chemistry |
* Мир-Бабаев М.Ф. Научный подвиг гения (к 100-летию со дня рождения Ю.Г. Мамедалиева) – «Consulting & Business», 2005, No.8, с.8–12.
* Mir-Babayev M.F. The role of Azerbaijan in the World's oil industry – “Oil-Industry History” (USA), 2011, v. 12, no. 1, p. 109–123.
* Mir-Babayev M.F. Formula of Victory (Yusif Mamedaliyev) - "SOCAR plus", 2012, Autumn, p. 100–111. | 0 | Theoretical and Fundamental Chemistry |
The hydroboration reaction is a useful reaction to functionalize alkenes to alcohols. In the reaction the trimethylsilyl (TMS) group fulfill 2 roles in directing the stereoselectivity of the reaction. First, the bulky size of TMS helped the molecule to preferably adopt a conformation where the TMS is not close to the methyl group on the alkene. Second, the TMS group conferred a stereoelectronic effect on the molecule by adopting an anti conformation to the directing orbitals of the alkene. For the regioselectivity of the reaction, the TMS group can stabilize the developing partial positive charge on the secondary carbon a lot better than a methyl group. | 0 | Theoretical and Fundamental Chemistry |
ChemMedChem is a biweekly peer-reviewed scientific journal covering medicinal chemistry. It is published by Wiley-VCH on behalf of Chemistry Europe. In addition to original research in the form of full papers and shorter communications, the journal contains review-type articles (reviews, minireviews, patent reviews, essays, highlights) as well as occasional book reviews and conference reports.
Topics covered include drug design, development and delivery, molecular modeling, combinatorial chemistry, drug target validation, lead generation, ADMET studies, and, as of 2017, nanomedicine (including targeted drug delivery, theranostics, and nanodrugs).
The first volume was published at the beginning of 2006 under the two founding chemical societies, the German Chemical Society and the Italian Chemical Society.
According to the Journal Citation Reports, the journal has a 2021 impact factor of 3.540. | 1 | Applied and Interdisciplinary Chemistry |
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