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Reversible-deactivation polymerization is defined as a chain polymerization propagated by chain carriers that are deactivated reversibly, bringing them into one or more active-dormant equilibria. An example of a reversible-deactivation polymerization is group-transfer polymerization. | 0 | Theoretical and Fundamental Chemistry |
6-Hydroxymelatonin (6-OHM) is a naturally occurring, endogenous, major active metabolite of melatonin. Similar to melatonin, 6-OHM is a full agonist of the MT and MT receptors. It is also an antioxidant and neuroprotective, and is even more potent in this regard relative to melatonin. | 1 | Applied and Interdisciplinary Chemistry |
The pair of trigonometric functions can be thought of as parametrizing the unit circle. The stereographic projection gives an alternative parametrization of the unit circle:
Under this reparametrization, the length element of the unit circle goes over to
This substitution can sometimes simplify integrals involving trigonometric functions. | 0 | Theoretical and Fundamental Chemistry |
In 1946, Leo Sommer and Frank C. Whitmore reported that radically chlorinating liquid ethyltrichlorosilane gave an isomeric mixture with exhibited unexpected reactivity in aqueous base. All chlorides pendant to silicon hydrolyze, but the geminal chlorine on carbon failed to hydrolyze, and the vicinal chlorine eliminated to ethene: The same behavior appeared with n-propyltrichlorosilane. The α and γ isomers resisted hydrolysis, but a hydroxyl group replaced the β chlorine: They concluded that silicon inhibits electrofugal activity at the α carbon.
The silicon effect also manifests in certain compound properties. Trimethylsilylmethylamine (MeSiCHNH) is a stronger base (conjugate pK 10.96) than neopentylamine (conjugate pK 10.21); trimethylsilylacetic acid (pKa 5.22) is a poorer acid than trimethylacetic acid (pKa 5.00).
In 1994, Yong and coworkers compared the free-energy effects of α- and β-Si(CH) moieties on C–H homo- and heterolysis. They, too, concluded that the β silicon atom could stabilize carbocations and the α silicon destabilize carbocations. | 0 | Theoretical and Fundamental Chemistry |
Once inside the mitochondria, each cycle of β-oxidation, liberating a two carbon unit (acetyl-CoA), occurs in a sequence of four reactions:
This process continues until the entire chain is cleaved into acetyl CoA units. The final cycle produces two separate acetyl CoAs, instead of one acyl CoA and one acetyl CoA. For every cycle, the Acyl CoA unit is shortened by two carbon atoms. Concomitantly, one molecule of FADH, NADH and acetyl CoA are formed. | 1 | Applied and Interdisciplinary Chemistry |
The Public Affairs Office works with the PAAC to advocate for increased research budgets for the major governmental funding agencies, primarily the National Institutes of Health and the National Science Foundation. ASBMB has developed a set of recommendations for pre-medical course requirements consistent with the new Medical College Admission Test. Advocacy efforts also focus on protecting the conditions that promote a successful research environment. In addition, the office works to maintain a healthy relationship between ASBMB members, government officials, and the public in order to foster awareness of the importance of science to everyday life.
As part of their advocacy efforts, ASBMB organizes Capitol Hill Day, an annual event that allows graduate students and trainees to meet their congressional representatives in Washington, D.C. | 1 | Applied and Interdisciplinary Chemistry |
In polymer chemistry, systems have been described based on addition polymerization with 1,4-benzenedithiol and 1,4-diethynylbenzene, in the synthesis of other addition polymer systems in the synthesis of dendrimers, in star polymers, in graft polymerization, block copolymers, and in polymer networks. Another reported application is the synthesis of macrocycles via dithiol coupling. | 0 | Theoretical and Fundamental Chemistry |
In its main applications, dithionite is generally prepared in situ by reduction of sulfur dioxide by sodium borohydride, described by the following idealized equation:.
Dithionite is a reducing agent. At pH 7, the potential is −0.66 V vs NHE. Redox occurs with formation of sulfite:
: + 2 HO → 2 + 2 e + 2 H
Dithionite undergoes acid hydrolytic disproportionation to thiosulfate and bisulfite:
:2 + HO → + 2
It also undergoes alkaline hydrolytic disproportionation to sulfite and sulfide:
:3 NaSO + 6 NaOH → 5 NaSO + NaS + 3 HO
It is formally derived from dithionous acid (HSO), but this acid does not exist in any practical sense. | 1 | Applied and Interdisciplinary Chemistry |
The United Nations framework for Sustainable Development Goals recognizes the damaging effects of eutrophication for marine environments. It has established a timeline for creating an Index of Coastal Eutrophication and Floating Plastic Debris Density (ICEP) within Sustainable Development Goal 14 (life below water). SDG 14 specifically has a target to: "by 2025, prevent and significantly reduce marine pollution of all kinds, in particular from land-based activities, including marine debris and nutrient pollution".
Policy and regulations are a set of tools to minimize causes of eutrophication. Nonpoint sources of pollution are the primary contributors to eutrophication, and their effects can be minimized through common agricultural practices. Reducing the amount of pollutants that reach a watershed can be achieved through the protection of its forest cover, reducing the amount of erosion leeching into a watershed. Also, through the efficient, controlled use of land using sustainable agricultural practices to minimize land degradation, the amount of soil runoff and nitrogen-based fertilizers reaching a watershed can be reduced. Waste disposal technology constitutes another factor in eutrophication prevention.
Because a body of water can have an effect on a range of people reaching far beyond that of the watershed, cooperation between different organizations is necessary to prevent the intrusion of contaminants that can lead to eutrophication. Agencies ranging from state governments to those of water resource management and non-governmental organizations, going as low as the local population, are responsible for preventing eutrophication of water bodies. In the United States, the most well known inter-state effort to prevent eutrophication is the Chesapeake Bay. | 1 | Applied and Interdisciplinary Chemistry |
The first known IPN was a combination of phenol-formaldehyde resin with vulcanized natural rubber made by Jonas Aylsworth in 1914. However, this was before Staudinger's hypothesis on macromolecules and thus the terms "polymer" or "IPN" were not yet used. The first usage of the term "interpenetrating polymer networks" was first introduced by J.R. Millar in 1960 while discussing networks of sulfonated and unsulfonated styrene–divinylbenzene copolymers. | 0 | Theoretical and Fundamental Chemistry |
Deuterated (i.e. where all or some hydrogen atoms are replaced with deuterium) compounds are often used as internal standards in mass spectrometry. Like other isotopically labeled species, such standards improve accuracy, while often at a much lower cost than other isotopically labeled standards. Deuterated molecules are usually prepared via hydrogen isotope exchange reactions. | 0 | Theoretical and Fundamental Chemistry |
In the Semail Nappe of Oman in the United Arb Emirates, silicified serpentinite was found. The occurrence of such geological features is rather unusual. It is a pseudomorphic alteration where the protolith of serpentinite was already silicified. Due to tectonic events, basal serpentinite was fractured and groundwater permeated along the faults, forming a large-scale circulation of groundwater within the strata. Through hydrothermal dissolution, silica precipitated and crystallized around the voids of serpentinite. Therefore, silicification can only be seen along groundwater paths. The silicification of serpentinite was formed under the condition where groundwater flow and carbon dioxide concentration are low. | 0 | Theoretical and Fundamental Chemistry |
Other hypothetical gene therapies could include changes to physical appearance, metabolism, mental faculties such as memory and intelligence, and well-being (by increasing resistance to depression or relieving chronic pain, for example). | 1 | Applied and Interdisciplinary Chemistry |
In organosulfur chemistry, a sulfonate is a salt, anion or ester of a sulfonic acid. Its formula is , containing the functional group , where R is typically an organyl group, amino group or a halogen atom. Sulfonates are the conjugate bases of sulfonic acids. Sulfonates are generally stable in water, non-oxidizing, and colorless. Many useful compounds and even some biochemicals feature sulfonates. | 0 | Theoretical and Fundamental Chemistry |
conversion of carbon dioxide| into gaseous hydrocarbons. The proposed reaction mechanisms involve the creation of a highly reactive carbon radical from carbon monoxide and carbon dioxide which then reacts with photogenerated protons to ultimately form methane. Efficiencies of -based photocatalysts are low, although nanostructures such as carbon nanotubes and metallic nanoparticles help. | 0 | Theoretical and Fundamental Chemistry |
The 1d version of the Kuramoto–Sivashinsky equation is
An alternate form is
obtained by differentiating with respect to and substituting . This is the form used in fluid dynamics applications.
The Kuramoto–Sivashinsky equation can also be generalized to higher dimensions. In spatially periodic domains, one possibility is
where is the Laplace operator, and is the biharmonic operator. | 1 | Applied and Interdisciplinary Chemistry |
Plastics are used extensively in the manufacture of electrical items, such as circuit boards and electrical cables. These applications can be harsh, exposing the plastic to a mixture of thermal, chemical and electrochemical attack. Many electric items like transformers, microprocessors or high-voltage cables operate at elevated temperatures for years, or even decades, resulting in low-level but continuous thermal oxidation. This can be exacerbated by direct contact with metals, which can promote the formation of free-radicals, for instance, by the action of Fenton reactions on hydroperoxides. High voltage loads can also damage insulating materials such as dielectrics, which degrade via electrical treeing caused by prolonged electrical field stress. | 0 | Theoretical and Fundamental Chemistry |
X-ray radiography is similar to gamma-ray radiography but instead of using a radioactive source, it uses a high-energy bremsstrahlung spectrum with energy in the 5–10 MeV range created by a linear particle accelerator (LINAC). Such X-ray systems can penetrate up to 30–40 cm of steel in vehicles moving with velocities up to 13 km/h. They provide higher penetration but also cost more to buy and operate. They are more suitable for the detection of special nuclear materials than gamma-ray systems. They also deliver about 1000 times higher dose of radiation to potential stowaways. | 0 | Theoretical and Fundamental Chemistry |
The term "thermal diode" can refer to:
* a (possibly non-electrical) device which allows heat to flow preferentially in one direction;
* an electrical (semiconductor) diode in reference to a thermal effect or function;
* or it may describe both situations, where an electrical diode is used as a heat pump or thermoelectric cooler. | 0 | Theoretical and Fundamental Chemistry |
Dexpramipexole was originally identified as a candidate therapy for amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease by James Bennett, M.D., Ph.D., then of the University of Virginia.
The drug was initially investigated in ALS by Knopp Biosciences and Biogen Idec. A 2010 Phase II clinical trial showed a slowing of ALS disease progression and mortality benefits. In January 2013, Biogen Idec discontinued its development of dexpramipexole in ALS due to lack of efficacy in the Phase III study.
As a result of observing eosinophil lowering in the ALS trials, Knopp pivoted dexpramipexole clinical development to eosinophil associated diseases. In subsequent clinical trials, dexpramipexole significantly reduced eosinophil counts and glucocorticoid requirements in patients with hypereosinophilic syndrome and significantly reduced blood and tissue eosinophil counts in patients with chronic rhinosinusitis with nasal polyps. | 0 | Theoretical and Fundamental Chemistry |
Evolutionary simulations are performed by reproduction-mutation-selection life cycle. Populations are fixed at size and they will not go extinct. Non-overlapping generations are employed. In a typical evolutionary simulation, a single random viable individual that can produce a stable gene expression pattern is chosen as the founder. Cloned individuals are generated to create a population of identical individuals. According to the asexual or sexual reproductive mode, offspring are produced by randomly choosing (with replacement) parent individual(s) from current generation. Mutations can be acquired with probability μ and survive with probability equal to their fitness. This process is repeated until N individuals are produced that go on to found the following generation. | 1 | Applied and Interdisciplinary Chemistry |
European imperial expansion and exploration into Africa overlapped with the rise of the European pharmaceutical industry towards the end of the nineteenth century. British troops were the target of arrows poisoned with the extracts of various Strophanthus species. They were familiar with the deadly properties of these plants and brought samples back to Europe. Around this time, interest in the plant grew. It was known that ouabain was a cardiac poison, but there was some speculation about its potential medical uses.
In 1882, ouabain was first isolated from the plant by the French chemist Léon-Albert Arnaud as an amorphous substance, which he identified as a glycoside. Ouabain was seen as a possible treatment for certain cardiac conditions. | 0 | Theoretical and Fundamental Chemistry |
The temperature jump method is a technique used in chemical kinetics for the measurement of very rapid reaction rates. It is one of a class of chemical relaxation methods pioneered by the German physical chemist Manfred Eigen in the 1950s. In these methods, a reacting system initially at equilibrium is perturbed rapidly and then observed as it relaxes back to equilibrium. In the case of temperature jump, the perturbation involves rapid heating which changes the value of the equilibrium constant, followed by relaxation to equilibrium at the new temperature.
The heating usually involves discharging of a capacitor (in the kV range) through a small volume (< 1 mL) of a conducting solution containing the molecule/reaction to be studied. In some versions of the apparatus used, the solution is heated instead by the output of a pulsed laser which emits in the near infra-red. When laser heating is employed, the solution need not be conducting. In both cases, the temperature of the solution is caused to rise by a small amount in microseconds (or less in the case of laser heating). This allows the study of the shift in equilibrium of reactions that equilibrate in milliseconds (or microseconds with laser temperature jump), these changes most commonly being observed using absorption spectroscopy or fluorescence spectroscopy. Due to the small volumes involved the temperature of the solution returns to that of its surroundings in minutes.
The fractional extent of the reaction (i.e. the percentage change in concentration of a measurable species) depends on the molar enthalpy change (ΔH°) between the reactants and products and the equilibrium position. If K is the equilibrium constant and dT is the change in temperature then the enthalpy change is given by the Van 't Hoff equation:
where R is the universal gas constant and T is the absolute temperature. When a single step in a reaction is perturbed in a temperature jump experiment, the reaction follows a single exponential decay function with time constant equal to a function of the forward (k) and reverse (k) rate constants. For the perturbation of a simple equilibrium which is first order in both directions, the reciprocal of the time constant equals the sum of the two rate constants
The two rate constants can be determined from the values of and the equilibrium constant :, yielding two equations for two unknowns.
In more complex reaction networks, when multiple reaction steps are perturbed, then the reciprocal time constants are given by the eigenvalues of the characteristic rate equations. The ability to observe intermediate steps in a reaction pathway is one of the attractive features of this technology.
Related chemical relaxation methods include pressure jump, electric field jump and pH jump. | 0 | Theoretical and Fundamental Chemistry |
β-Hydroxybutyric acid, also known as 3-hydroxybutyric acid or BHB, is an organic compound and a beta hydroxy acid with the chemical formula CHCH(OH)CHCOH; its conjugate base is β-hydroxybutyrate, also known as 3-hydroxybutyrate. β-Hydroxybutyric acid is a chiral compound with two enantiomers: -β-hydroxybutyric acid and -β-hydroxybutyric acid. Its oxidized and polymeric derivatives occur widely in nature. In humans, -β-hydroxybutyric acid is one of two primary endogenous agonists of hydroxycarboxylic acid receptor 2 (HCA), a G protein-coupled receptor (GPCR). | 1 | Applied and Interdisciplinary Chemistry |
A growing trend in the world of elemental analysis has revolved around the speciation, or determination of oxidation state of certain metals such as chromium and arsenic. The toxicity of those elements varies with the oxidation state, so new regulations from food authorities requires speciation of some elements. One of the primary techniques to achieve this is to separate the chemical species with high-performance liquid chromatography (HPLC) or field flow fractionation (FFF) and then measure the concentrations with ICP-MS. | 0 | Theoretical and Fundamental Chemistry |
With improvements in measuring techniques such as atomic force microscopy, confocal microscopy, and scanning electron microscope, researchers were able to produce and image droplets at ever smaller scales. With the reduction in droplet size came new experimental observations of wetting. These observations confirmed that the modified Young's equation does not hold at the micro-nano scales. Jasper proposed that including a term in the variation of the free energy may be the key to solving the contact angle problem at such small scales. Given that the variation in free energy is zero at equilibrium:
The variation in the pressure at the free liquid-vapor boundary is due to Laplace pressure, which is proportional to the mean curvature. Solving the above equation for both convex and concave surfaces yields:
where
This equation relates the contact angle, a geometric property of a sessile droplet to the bulk thermodynamics, the energy at the three phase contact boundary, and the mean curvature of the droplet. For the special case of a sessile droplet on a flat surface ():
In the above equation, the first two terms are the modified Young's equation, while the third term is due to the Laplace pressure. This nonlinear equation correctly predicts the sign and magnitude of , the flattening of the contact angle at very small scales, and contact angle hysteresis. | 0 | Theoretical and Fundamental Chemistry |
In chromatography, the retardation factor, R, is the fraction of the sample in the mobile phase at equilibrium, defined as: | 0 | Theoretical and Fundamental Chemistry |
* Capacitance probe, or fringe capacitance sensor. Capacitance probes use capacitance to measure the dielectric permittivity of the soil. The volume of water in the total volume of soil most heavily influences the dielectric permittivity of the soil because the dielectric constant of water (80) is much greater than the other constituents of the soil (mineral soil: 4, organic matter: 4, air: 1). Thus, when the amount of water changes in the soil, the probe will measure a change in capacitance (from the change in dielectric permittivity) that can be directly correlated with a change in water content. Circuitry inside some commercial probes change the capacitance measurement into a proportional millivolt output. Other configuration are like the neutron probe where an access tube made of PVC is installed in the soil. The probe consists of sensing head at fixed depth. The sensing head consists of an oscillator circuit, the frequency is determined by an annular electrode, fringe-effect capacitor, and the dielectric constant of the soil.
* Electrical impedance sensor, which consists of soil probes and using electrical impedance measurement. The most common configuration is based on the standing wave principle (Gaskin & Miller, 1996). The device comprises a 100 MHz sinusoidal oscillator, a fixed impedance coaxial transmission line, and probe wires which is buried in the soil. The oscillator signal is propagated along the transmission line into the soil probe, and if the probe's impedance differs from that of the transmission line, a proportion of the incident signal is reflected back along the line towards the signal source. | 0 | Theoretical and Fundamental Chemistry |
Nanodiamonds (NDs) are carbon nanoparticles which can vary from ~4-100 nm in diameter. NDs are typically formed in two ways: from micron-sized diamond particles under high-pressure high-temperature conditions, called high-pressure high-temperature nanodiamonds (HPHT NDs) and by shock-wave compression, called detonation nanodiamonds (DNDs). The surfaces of these NDs can be modified by processes such as oxidation and aminification to alter adsorption properties. | 1 | Applied and Interdisciplinary Chemistry |
The journal is abstracted and indexed in:
*Chemical Abstracts
*Current Contents/Engineering, Computing & Technology
*Inspec
*Materials Science Citation Index
*Scopus
According to the Journal Citation Reports, the journal has a 2020 impact factor of 7.205. | 1 | Applied and Interdisciplinary Chemistry |
Some authors refer to the grand potential as the Landau free energy or Landau potential and write its definition as:
named after Russian physicist Lev Landau, which may be a synonym for the grand potential, depending on system stipulations. For homogeneous systems, one obtains . | 0 | Theoretical and Fundamental Chemistry |
Depletion gilding is a decorative process, with no significant industrial applications. It is not widely used in modern times, having been superseded by processes more suited to mass production, such as electroplating. Some individual artisans and small shops continue to practice it.
However, depletion gilding was widely used in antiquity. While it requires skill to execute it well, the process itself is technologically simple, and uses materials that are readily available to most ancient civilizations. Some form of depletion gilding has been used by nearly every culture that developed metalworking. The South American Sican culture in particular developed depletion gilding to a high art. Some ancient alloys, such as tumbaga, may have been developed specifically for use in depletion gilding. The technique was not known to be used by Anglo-Saxons until detailed examination with electron microscopes of treasures such as the Staffordshire Hoard revealed its use in the twenty-first century.
Certain cultures are thought to have attached mythical or spiritual significance to the process. Gold was considered sacred in many early civilizations and was highly valued in nearly all of them, and anything relating to it had the potential to take on cultural importance. Moreover, the ability to turn what appeared to be an object made of copper into what seemed to be pure gold would be very impressive. There is some speculation that depletion gilding may have contributed to the concepts of alchemy, a major goal of which was to physically transform one metal into another. | 1 | Applied and Interdisciplinary Chemistry |
There are 20 naturally occurring amino acids, however some of these share similar characteristics. For example, leucine and isoleucine are both aliphatic, branched hydrophobes. Similarly, aspartic acid and glutamic acid are both small, negatively charged residues.
Although there are many ways to classify amino acids, they are often sorted into six main classes on the basis of their structure and the general chemical characteristics of their side chains (R groups).
Physicochemical distances aim at quantifying the intra-class and inter-class dissimilarity between amino acids based on their measurable properties, and many such measures have been proposed in the literature. Owing to their simplicity, two of the most commonly used measures are the ones of Grantham (1974) and Miyata et al (1979). A conservative replacement is therefore an exchange between two amino acids separated by a small physicochemical distance. Conversely, a radical replacement is an exchange between two amino acids separated by a large physicochemical distance. | 1 | Applied and Interdisciplinary Chemistry |
As of August 2008, Cancer Care Ontario reports that the current average incremental cost to perform a PET scan in the province is CA$1,000–1,200 per scan. This includes the cost of the radiopharmaceutical and a stipend for the physician reading the scan.
In the United States, a PET scan is estimated to be US$5,000, and most insurance companies do not pay for routine PET scans after cancer treatment due to the fact that these scans are often unnecessary and present potentially more risks than benefits.
In England, the National Health Service reference cost (2015–2016) for an adult outpatient PET scan is £798.
In Australia, as of July 2018, the Medicare Benefits Schedule Fee for whole body FDG PET ranges from A$953 to A$999, depending on the indication for the scan. | 1 | Applied and Interdisciplinary Chemistry |
Metal nitrosyls, compounds featuring NO ligands, are numerous. In contrast to metal carbonyls, however, homoleptic metal nitrosyls are rare. NO is a stronger π-acceptor than CO. Well known nitrosyl carbonyls include CoNO(CO) and Fe(NO)(CO), which are analogues of Ni(CO). | 0 | Theoretical and Fundamental Chemistry |
Cellular models are instrumental in dissecting a complex pathological process into simpler molecular events. Parkinson's disease (PD) is multifactorial and clinically heterogeneous; the aetiology of the sporadic (and most common) form is still unclear and only a few molecular mechanisms have been clarified so far in the neurodegenerative cascade. In such a multifaceted picture, it is particularly important to identify experimental models that simplify the study of the different networks of proteins and genes involved. Cellular models that reproduce some of the features of the neurons that degenerate in PD have contributed to many advances in our comprehension of the pathogenic flow of the disease. In particular, the pivotal biochemical pathways (i.e. apoptosis and oxidative stress, mitochondrial impairment and dysfunctional mitophagy, unfolded protein stress and improper removal of misfolded proteins) have been widely explored in cell lines, challenged with toxic insults or genetically modified. The central role of a-synuclein has generated many models aiming to elucidate its contribution to the dysregulation of various cellular processes. Classical cellular models appear to be the correct choice for preliminary studies on the molecular action of new drugs or potential toxins and for understanding the role of single genetic factors. Moreover, the availability of novel cellular systems, such as cybrids or induced pluripotent stem cells, offers the chance to exploit the advantages of an in vitro investigation, although mirroring more closely the cell population being affected. | 0 | Theoretical and Fundamental Chemistry |
Modern drill pipe is made from the welding of at least three separate pieces: box tool joint, pin tool joint, and the tube. The green tubes are received by the drill pipe manufacturer from the steel mill. The ends of the tubes are then upset to increase the cross-sectional area of the ends. The tube end may be externally upset (EU), internally upset (IU), or internally and externally upset (IEU). Standard max upset dimensions are specified in API 5DP, but the exact dimensions of the upset are proprietary to the manufacturer. After upsetting, the tube then goes through a heat treating process. Drill pipe steel is commonly quenched and tempered to achieve high yield strengths (135 ksi is a common tube yield strength).
The tool joints (connectors) are also received by the manufacturer as green tubes. After a quench and temper heat treat, the tool joints are cut into box (female) and pin (male) threads. Tool joints are commonly 120 ksi Specified Minimum Yield Strength (SMYS), rather than the 135 ksi of the tube. They generally are stiffer than the tube, increasing the likelihood of fatigue failure at the junction. The lower SMYS on the connection increases the fatigue resistance. Higher strength steels are typically harder and more brittle, making them more susceptible to cracking and subsequent stress crack propagation.
Tubes and tool joints are welded using rotary inertia or direct drive friction welding. The tube is held stationary while the tool joint is revolved at high RPMs. The tool joint is then firmly pressed onto the upset end of the tube while the tool joint is rotating. The heat and force during this interaction weld the two together. Once the "ram horns" or excess material is removed, the weld line can only be seen under a microscope. Inertia friction welding is the traditional proven method. Direct drive friction welding is controlled and monitored up to 1,000 times a second, resulting in a fine quality weld that does not necessarily need a full heat treat quench and temper regime. | 1 | Applied and Interdisciplinary Chemistry |
Wootz steel originated in the mid-1st millennium BC in India, in present-day Tiruchirappalli, Kodumanal, Erode, Tamil Nadu. There are several ancient Tamil, North Indian, Greek, Chinese and Roman literary references to high-carbon Tamil steel. In later times, wootz steel was also made in Golconda in Telangana, Karnataka and Sri Lanka. The steel was exported as cakes of steely iron that came to be known as "Wootz". The method was to heat black magnetite ore in the presence of carbon in a sealed clay crucible inside a charcoal furnace to completely remove slag. An alternative was to smelt the ore first to give wrought iron, then heat and hammer it to remove slag. The carbon source was bamboo and leaves from plants such as Avārai. Locals in Sri Lanka adopted the production methods of creating wootz steel from the Chera Tamils by the 5th century BC. Joseph Needham in 1971 claimed China produced a similar steel also by the 5th century BCE but more recent research in China (2009) showed that Needham erroneously identified the ancient Chinese steel as hyper-eutectoid and similar to wootz but it was really produced via co-fusion process instead (smelting cast iron and wrought iron together). Genuine wootz in China was mentioned for the first time much later, during the Bei Wei Dynasty (386-534 CE) under the name “Bintie” or “Pin t’ieh” as being produced in India, ingots were initially given by Persian Kings as valuable presents, later the Chinese called "bintie" the various co-fusion hard steels they produced. In Sri Lanka, this early steel-making method employed a unique wind furnace, driven by the monsoon winds. Production sites from antiquity have emerged, in places such as Anuradhapura, Tissamaharama and Samanalawewa, as well as imported artifacts of ancient iron and steel from Kodumanal. Recent archaeological excavations (2018) of the Yodhawewa site (in Mannar District) discovered a lower half-spherical furnace, crucible fragments, and lid fragments related to the crucible steel production through the carburization process. A 200 BC Tamil trade guild in Tissamaharama, in the South East of Sri Lanka, brought with them some of the oldest iron and steel artifacts and production processes to the island from the classical period.
Trade between India and Sri Lanka through the Arabian Sea introduced wootz steel to Arabia. The term muhannad مهند or hendeyy هندي in pre-Islamic and early Islamic Arabic refers to sword blades made from Indian steel, which were highly prized, and are attested in Arabic poetry. Further trade spread the technology to the city of Damascus, where an industry developed for making weapons of this steel. This led to the development of Damascus steel. The 12th century Arab traveler Edrisi mentioned the "Hinduwani" or Indian steel as the best in the world. Arab accounts also point to the fame of Teling steel, which can be taken to refer to the region of Telangana. The Golconda region of Telangana clearly being the nodal centre for the export of wootz steel to West Asia.
Another sign of its reputation is seen in a Persian phraseto give an "Indian answer", meaning "a cut with an Indian sword". Wootz steel was widely exported and traded throughout ancient Europe and the Arab world, and became particularly famous in the Middle East. | 1 | Applied and Interdisciplinary Chemistry |
According to preliminary findings of a novel method of SGLT-2 inhibition, the antisense oligonucleotide ISIS 388626 improved plasma glucose in rodents and dogs by reducing mRNA expression in the proximal renal tubules by up to 80% when given once a week. It did not affect SGLT-1. A study results on long-term use of ISIS 388626 in non-human primates observed more than 1000 fold increase in glucosuria without any associated hypoglycemia. This increase in glucosuria can be attributed to a dose-dependent reduction in the expression of SGLT-2, where the highest dose led to more than 75% reduction. In 2011, Ionis Pharmaceuticals initiated a clinical phase 1 study with ISIS-SGLT-2RX, a 12-nucleotide antisense oligonucleotide. Results from this study were published in 2017 and the treatment was "associated with unexpected renal effects". The authors concluded that "Before the concept of antisense-mediated blocking of SGLT2 with ISIS 388626 can be explored further, more preclinical data are needed to justify further investigations." | 1 | Applied and Interdisciplinary Chemistry |
Advanced process control systems for process miniaturization will increase the need for controlling the security and ownership of process intelligence in a knowledge-based business. It will become more difficult to control intellectual property through the traditional method of patents; therefore, trademarks, brand recognition, and copyright laws will play a more important role in value security for knowledge-based businesses of the future.
Techno-economic analysis, as taught in traditional chemical process design, will also dramatically shift from a conservative viewpoint of utilization of historical trend economics and cash flow analysis. Economic viability of a given enterprise will be more linked to acquisition of real-time economic information, that can rapidly change based on empirical observations created by an emerging discipline of microprocess development systems; therefore, the models will be more based on "what can be?" rather that "what has the past shown?" | 1 | Applied and Interdisciplinary Chemistry |
One of the first in vitro tests for aspirin was through the Trinder reaction. Aqueous ferric chloride was added to a urine sample, and the formation of the iron complex turned the solution purple. This test was not specific to acetylsalicylic acid but would occur in the presence of any phenol or enol. The downfall of this test occurs in the presence of hyperbilirubinemia or elevated bilirubin. When the level of bilirubin exceeds 1 mg/dl, a false positive could occur. | 0 | Theoretical and Fundamental Chemistry |
Macrocyclic molecules such as cyclodextrins act often as the second coordination sphere for metal complexes. | 0 | Theoretical and Fundamental Chemistry |
The chemical composition of meteorites can be analyzed quite accurately using EPMA. This can reveal much about the conditions that existed in the early Solar System. | 0 | Theoretical and Fundamental Chemistry |
Native gels are run in non-denaturing conditions so that the analytes natural or bioactive structure is maintained. This allows the physical size of the folded or assembled complex to affect the mobility, allowing for analysis of all four levels of the biomolecular structure. For biological samples, detergents are used only to the extent that they are necessary to lyse lipid membranes in the cell. Complexes normally remain associated and folded as they would be in the cell. One downside, however, is that complexes may not separate cleanly or predictably, as it is difficult to predict how the molecules shape and size will affect its mobility. Addressing and solving this problem is a major aim of preparative native PAGE.
Unlike denaturing methods, native gel electrophoresis does not use a charged denaturing agent. The molecules being separated (usually proteins or nucleic acids), therefore, differ not only in molecular mass and intrinsic charge, but also the cross-sectional area, and thus experience different electrophoretic forces dependent on the shape of the overall structure. For proteins, since they remain in the native state they may be visualized not only by general protein staining reagents but also by specific enzyme-linked staining.
A specific experiment example of an application of native gel electrophoresis is to check for enzymatic activity to verify the presence of the enzyme in the sample during protein purification. For example, for the protein alkaline phosphatase, the staining solution is a mixture of 4-chloro-2-2-methylbenzenediazonium salt with 3-phospho-2-naphthoic acid-2-4-dimethyl aniline in Tris buffer. This stain is commercially sold as a kit for staining gels. If the protein is present, the mechanism of the reaction takes place in the following order: it starts with the de-phosphorylation of 3-phospho-2-naphthoic acid-2-4-dimethyl aniline by alkaline phosphatase (water is needed for the reaction). The phosphate group is released and replaced by an alcohol group from water. The electrophile 4-chloro-2-2-methylbenzenediazonium (Fast Red TR Diazonium salt) displaces the alcohol group forming the final product Red Azo dye. As its name implies, this is the final visible-red product of the reaction. In undergraduate academic experimentation of protein purification, the gel is usually run next to commercial purified samples to visualize the results and conclude whether or not purification was successful.
Native gel electrophoresis is typically used in proteomics and metallomics. However, native PAGE is also used to scan genes (DNA) for unknown mutations as in single-strand conformation polymorphism. | 1 | Applied and Interdisciplinary Chemistry |
Cosmids are predominantly plasmids with a bacterial oriV, an antibiotic selection marker and a cloning site, but they carry one, or more recently two, cos sites derived from bacteriophage lambda. Depending on the particular aim of the experiment, broad host range cosmids, shuttle cosmids or mammalian cosmids (linked to SV40 oriV and mammalian selection markers) are available. The loading capacity of cosmids varies depending on the size of the vector itself but usually lies around 40–45 kb. The cloning procedure involves the generation of two vector arms which are then joined to the foreign DNA. Selection against wild type cosmid DNA is simply done via size exclusion. Cosmids, therefore, always form colonies and not plaques. Also the clone density is much lower with around 10 – 10 CFU per µg of ligated DNA.
After the construction of recombinant lambda or cosmid libraries the total DNA is transferred into an appropriate E. coli host via a technique called in vitro packaging. The necessary packaging extracts are derived from E. coli cI857 lysogens (red- gam- Sam and Dam (head assembly) and Eam (tail assembly) respectively). These extracts will recognize and package the recombinant molecules in vitro, generating either mature phage particles (lambda-based vectors) or recombinant plasmids contained in phage shells (cosmids). These differences are reflected in the different infection frequencies seen in favour of lambda-replacement vectors. This compensates for their slightly lower loading capacity. Phage libraries are also stored and screened more easily than cosmid libraries.
Target DNA: the genomic DNA to be cloned has to be cut into the appropriate size range of restriction fragments. This is usually done by partial restriction followed by either size fractionation or dephosphorylation (using calf-intestine phosphatase) to avoid chromosome scrambling, i.e. the ligation of physically unlinked fragments. | 1 | Applied and Interdisciplinary Chemistry |
The only approved indication for oral vancomycin therapy is in the treatment of pseudomembranous colitis, where it must be given orally to reach the site of infection in the colon. Following oral administration, the fecal concentration of vancomycin is around 500 µg/mL (sensitive strains of Clostridium difficile have a mean inhibitory concentration of ≤2 µg/mL) | 0 | Theoretical and Fundamental Chemistry |
A metamorphic reaction is a chemical reaction that takes place during the geological process of metamorphism wherein one assemblage of minerals is transformed into a second assemblage which is stable under the new temperature/pressure conditions resulting in the final stable state of the observed metamorphic rock.
Examples include the production of talc under varied metamorphic conditions:
:serpentine + carbon dioxide → talc + magnesite + water
:chlorite + quartz → kyanite + talc + water | 0 | Theoretical and Fundamental Chemistry |
The genus Ancyronyx was established in 1847 by the German entomologist Wilhelm Ferdinand Erichson based on the type species Macronychus variegatus first described in 1824 by the German coleopterologist Ernst Friedrich Germar. It was regarded as a monotypic species until the French entomologist Antoine Henri Grouvelle described the second species, A. acaroides in 1896. It is the sole member of the tribe Ancyronychini, and is classified under the subfamily Elminae of the riffle beetle family, Elmidae. | 1 | Applied and Interdisciplinary Chemistry |
Isomerization of epoxides to allylic alcohols under strongly basic conditions proceeds by a β-elimination process. A model has been advanced that invokes an initial complex between the lithium amide base and epoxide. Concerted C–O bond cleavage and deprotonation proceeds via a syn transition state to give an allylic alkoxide, which is protonated upon workup. Deprotonation typically occurs at the exist in the transition state for cis double bond formation.
Other processes may take place competitively under basic conditions, particularly when β-elimination is slow or not possible. These pathways likely begin with lithiation of a carbon in the epoxide ring, followed by α-elimination to afford a carbene intermediate. 1,2-hydrogen migration leads to ketones, while intramolecular C–H insertion affords cyclic alcohols with the formation of a new carbon-carbon bond.
In many cases when hexamethylphosphoramide (HMPA) is used as an additive with lithium amide bases, selectivity for the formation of allylic alcohols increases. These reactions are believed to proceed through E2 elimination. | 0 | Theoretical and Fundamental Chemistry |
This basic concept is more correctly known as an aspirating skimmer, since some skimmer designs using an aspirator do not use a "Pin-Wheel"/"Adrian-Wheel" or "Needle-Wheel". "Pin-Wheel"/"Adrian-Wheel" describes the look of an impeller that consists of a disk with pins mounted perpendicular (90°) to the disc and parallel to the rotor. "Needle-Wheel" describes the look of an impeller that consists of a series of pins projecting out perpendicular to the rotor from a central axis. "Mesh-Wheel" describes the look of an impeller that consists of a mesh material attached to a plate or central axis on the rotor. The purpose of these modified impellers is to chop or shred the air that is introduced via an air aspirator apparatus or external air pump into very fine bubbles. The Mesh-Wheel design provides excellent results in the short term because of its ability to create fine bubbles with its thin cutting surfaces, but its propensity for clogging makes it an unreliable design.
The air aspirator differs from the venturi by the positioning of the water pump. With a venturi, the water is pushed through the unit, creating a vacuum to draw in air. With an air aspirator, the water is pulled through the unit, creating a vacuum to draw in air. These terms, however, are often incorrectly interchanged.
This style of protein skimmer has become very popular with public aquariums and is believed to be the most popular type of skimmer used with residential reef aquariums today. It has been particularly successful in smaller aquariums due to its usually compact size, ease of set up and use, and quiet operation. Since the pump is pushing a mixture of air and water, the power required to turn the rotor can be decreased and may result in a lower power requirement for that pump vs. the same pump with a different impeller when it is only pumping water. | 0 | Theoretical and Fundamental Chemistry |
Bioreactor landfills are a relatively new technology. For the newly developed bioreactor landfills initial monitoring costs are higher to ensure that everything important is discovered and properly controlled. This includes gases, odours and seepage of leachate into the ground surface.
The increased moisture content of bioreactor landfill may reduce the structural stability of the landfill by increasing the pore water pressure within the waste mass.
Since the target of bioreactor landfills is to maintain a high moisture content, gas collection systems can be affected by the increased moisture content of the waste. | 1 | Applied and Interdisciplinary Chemistry |
* Carson Jeffries, "Dynamic Nuclear Orientation", New York, Interscience Publishers, 1963
* Anatole Abragam and Maurice Goldman, "Nuclear Magnetism: Order and Disorder", New York : Oxford University Press, 1982
* Tom Wenckebach, [http://www.wenckebach.net/html/dnp-book.html "Essentials of Dynamic Nuclear Polarization"], Spindrift Publications, The Netherlands, 2016 | 0 | Theoretical and Fundamental Chemistry |
Acylals in organic chemistry are a group of chemical compounds sharing a functional group with the general structure RCH(OOCR). Acylals are obtained by reaction of carbonyls with acetic anhydride or other acid anhydrides and a suitable catalyst, for instance with sulfated zirconia at low temperatures when used as protective groups for aldehydes. High temperature exposure converts the acylal back to the aldehyde. | 0 | Theoretical and Fundamental Chemistry |
David Michael Patrick Mingos, FRS (born 6 August 1944) is a British chemist and academic. He was Principal of St Edmund Hall, Oxford from 1999 to 2009, and Professor of Inorganic Chemistry at the University of Oxford. | 0 | Theoretical and Fundamental Chemistry |
Prepared samples are combusted from 1000 up to 1200 degrees C in an oxygen-rich atmosphere. All carbon present converts to carbon dioxide, flows through scrubber tubes to remove interferences such as chlorine gas, and water vapor, and the carbon dioxide is measured either by absorption into a strong base then weighed, or using an infrared detector. Most modern analyzers use non-dispersive infrared (NDIR) for detection of the carbon dioxide. Compared to the conventional high temperature catalytic oxidation, the great benefit of the combustion-method is the high oxidation power, so that oxidation-promoting catalysts are superfluous. | 0 | Theoretical and Fundamental Chemistry |
UDP-Galactose is especially relevant in glycolysis. It is derived from galactose an epimer of glucose, and via the Leloir Pathway, it is used be used as a precursor for the metabolism of glucose into pyruvate. When lactose is hydrolyzed, D-Galactose enters the liver via the bloodstream. There, galactokinase phosphorylates it to galactose-1-phosphate using ATP. This compound then engages in a "ping-pong" reaction with UDP-Glucose, catalyzed by uridylyltransferase, yielding glucose-1-phosphate and UDP-Galactose. This glucose-1-phosphate feeds into glycolysis, while UDP-Galactose undergoes epimerization to regenerate UDP-Glucose. | 1 | Applied and Interdisciplinary Chemistry |
In physics, deflection is a change in a moving object's velocity, hence its trajectory, as a consequence of contact (collision) with a surface or the influence of a non-contact force field. Examples of the former include a ball bouncing off the ground or a bat; examples of the latter include a beam of electrons used to produce a picture, or the relativistic bending of light due to gravity. | 0 | Theoretical and Fundamental Chemistry |
In the Late Bronze Age, the site became an administrative center of a larger region in the kingdom of Isuwa. The city was heavily fortified, probably due to the Hittite threat from the west. It was culturally influenced by the Hurrians, Mitanni and the Hittites.
Around 1350 BC, Šuppiluliuma I of the Hittites conquered Melid in his war against Tushratta of Mitanni. At the time Melid was a regional capital of Isuwa at the frontier between the Hittites and the Mitanni; it was loyal to Tushratta. Suppiluliuma I used Melid as a base for his military campaign to sack the Mitanni capital Washukanni. | 1 | Applied and Interdisciplinary Chemistry |
* Endomycetales (yeasts): Candida albicans, Candida cylindracea, Candida melibiosica, Candida parapsilosis, and Candida rugosa. | 1 | Applied and Interdisciplinary Chemistry |
NADK is highly regulated by the redox state of the cell. Whereas NAD is predominantly found in its oxidized state NAD, the phosphorylated NADP is largely present in its reduced form, as NADPH. Thus, NADK can modulate responses to oxidative stress by controlling NADP synthesis. Bacterial NADK is shown to be inhibited allosterically by both NADPH and NADH. NADK is also reportedly stimulated by calcium/calmodulin binding in certain cell types, such as neutrophils. NAD kinases in plants and sea urchin eggs have also been found to bind calmodulin. | 1 | Applied and Interdisciplinary Chemistry |
It was founded in 1910 as the Aluminium Plant & Vessel Company Limited, fabricating equipment for breweries and vegetable oil in Wandsworth. In the 1950s it moved to Crawley and expanded considerably, under the name A.P.V. Co. Ltd. In 1967 it acquired Kestner Evaporator and Engineering Co, another major process plant manufacturer.
Continuing expansion led to a works of 1600 employees under the name APV International, supplying equipment services to the dairy, food and chemical industries by 1984. In addition a foundry employing 350 people named APV Paramount made high alloy steels and Vent-Axia a subsidiary company making fans, were near by.
In 1987 it merged with Baker Perkins to become APV Baker, later shortened to APV. The two manufacturing arms remained physically separate and the APV section was acquired by Siebe plc in 1997. After the merger of Siebe with BTR plc, APV was acquired by SPX Corporation in 2007 where it remains as a brand name for pumps, valves, heat exchangers, mixers and homogenizers in the process industries. | 1 | Applied and Interdisciplinary Chemistry |
The mean age of all the particles inside the control volume at time t is the first moment of the age distribution:
The mean residence time or mean transit time, that is the mean age of all the particles leaving the control volume at time t, is the first moment of the residence time distribution:
The mean age and the mean transit time generally have different values, even in stationary conditions:
* : examples include water in a lake with the inlet and outlet on opposite sides and radioactive material introduced high in the stratosphere by a nuclear bomb test and filtering down to the troposphere.
* : E and I are exponential distributions. Examples include radioactive decay and first order chemical reactions (where the reaction rate is proportional to the amount of reactant).
* : most of the particles entering the control volume pass through quickly, but most of the particles contained in the control volume pass through slowly. Examples include water in a lake with the inlet and outlet that are close together and water vapor rising from the ocean surface, which for the most part returns quickly to the ocean, while for the rest is retained in the atmosphere and returns much later in the form of rain. | 0 | Theoretical and Fundamental Chemistry |
where = number of electrons produced, = number of photons absorbed.
Assuming each photon absorbed in the depletion layer produces a viable electron-hole pair, and all other photons do not,
where t is the measurement time (in seconds),
= incident optical power in watts,
= optical power absorbed in depletion layer, also in watts. | 0 | Theoretical and Fundamental Chemistry |
Iron was never smelted by Native Americans, thus the New World never entered a proper "Iron Age" before European discovery, and the term is not used of the Americas. But there was limited use of native (unsmelted) iron ore, from magnetite, iron pyrite and ilmenite (iron–titanium), especially in the Andes (Chavin and Moche cultures) and Mesoamerica, after 900 BCE and until . Various forms of iron ore were mined,
drilled and highly polished. There is considerable evidence that this technology, its raw materials and end products were widely traded in Mesoamerica throughout the Formative era (2000–200BCE).
Lumps of iron pyrite, magnetite, and other materials were mostly shaped into mirrors, pendants, medallions, and headdress ornaments for decorative and ceremonial effect.
However, concave iron ore mirrors were apparently used for firing and optical purposes by the Olmec (1500–400BCE) and Chavin (900–300BCE) cultures,
and ilmenite "beads" may have served as hammers for fine work.
The Olmec and Izapa (300BCE – 100CE) also seem to have used iron magnetism to align and position monuments.
They may have developed a zeroth-order compass using a magnetite bar.
Some Mesoamerican uses of native iron seem to have been military. Steven Jones proposed that the Olmec sewed ilmenite "beads" into protective mail armour or helmets. Iron pyrite mosaics and plates formed protective tezcacuitlapalli (mirrored back flap shields) and breastplate ornaments in the military attire of the Teotihuacan (100 BCE – 600 CE), Toltec (800–1150 CE) and Chichen Itza (800–1200 CE) cultures. | 1 | Applied and Interdisciplinary Chemistry |
Iatrochemical principles form a major part of the Indian alchemical tradition (Sanskrit rasaśāstra, रसशास्त्र). Alchemical texts start to be composed in Sanskrit in South Asia from the end of the first millennium CE, and a flourishing literature developed and continued even into the twentieth century. These works contain extensive chapters on the use of alchemical recipes for healing.
The use of plants, minerals and metals in medical therapeutics also existed in India. In Ayurvedic medicine, substances used in these therapeutics were known as Rasa dravyas. Ayurvedic medicine instills the belief that every material had the potential to be used as a substance. This drove the creation of new products and new uses for common substances in nature. The people of Ayurvedic medicine categorize the materials in nature into three categories: Janagama, substances from animals such as milk, urine, blood, and meat, Audbhida or substances from plants such as stems, roots or leaves, and Paarthiwa or metal/mineral substances such as gold, silver, copper or sulfur. There was especially an emphasis on the element, Mercury, in this culture. The name of these specific practices in Ayurvedic medicine, were termed Rasashaastra, which means the "Science of Mercury". which has eventually become known as Iatrochemistry in current terminology. Much of the focus of Rasashaastra was on the processing of these metals to become ingestible by the human body. The therapeutic effect of the materials such as metals and minerals that were known to be indigestible by the human body were combined with plants or animal materials to increase their delivery ability to human body. | 1 | Applied and Interdisciplinary Chemistry |
It is not possible to directly measure the wind stress on the ocean surface. To obtain measurements of the wind stress, another easily measurable quantity like wind speed is measured and then via a parametrization the wind stress observations are obtained. Still, measurements of the wind stress are important as the value of the drag coefficient is not known for unsteady and non-ideal conditions. Measurements of the wind stress for such conditions can resolve the issue of the unknown drag coefficient. Four methods of measuring the drag coefficient are known as the Reynolds stress method, the dissipation method, the profile method and a method of using radar remote sensing. | 1 | Applied and Interdisciplinary Chemistry |
The development of methods to detect and identify biomolecules has been motivated by the ability to improve the study of molecular structure and interactions. Before the advent of fluorescent labeling, radioisotopes were used to detect and identify molecular compounds. Since then, safer methods have been developed that involve the use of fluorescent dyes or fluorescent proteins as tags or probes as a means to label and identify biomolecules. Although fluorescent tagging in this regard has only been recently utilized, the discovery of fluorescence has been around for a much longer time.
Sir George Stokes developed the Stokes Law of Fluorescence in 1852 which states that the wavelength of fluorescence emission is greater than that of the exciting radiation. Richard Meyer then termed fluorophore in 1897 to describe a chemical group associated with fluorescence. Since then, Fluorescein was created as a fluorescent dye by Adolph von Baeyer in 1871 and the method of staining was developed and utilized with the development of fluorescence microscopy in 1911.
Ethidium bromide and variants were developed in the 1950s, and in 1994, fluorescent proteins or FPs were introduced. Green fluorescent protein or GFP was discovered by Osamu Shimomura in the 1960s and was developed as a tracer molecule by Douglas Prasher in 1987. FPs led to a breakthrough of live cell imaging with the ability to selectively tag genetic protein regions and observe protein functions and mechanisms. For this breakthrough, Shimomura was awarded the Nobel Prize in 2008.
New methods for tracking biomolecules have been developed including the use of colorimetric biosensors, photochromic compounds, biomaterials, and electrochemical sensors. Fluorescent labeling is also a common method in which applications have expanded to enzymatic labeling, chemical labeling, protein labeling, and genetic labeling. | 1 | Applied and Interdisciplinary Chemistry |
GPCRs are involved in a wide variety of physiological processes. Some examples of their physiological roles include:
# The visual sense: The opsins use a photoisomerization reaction to translate electromagnetic radiation into cellular signals. Rhodopsin, for example, uses the conversion of 11-cis-retinal to all-trans-retinal for this purpose.
# The gustatory sense (taste): GPCRs in taste cells mediate release of gustducin in response to bitter-, umami- and sweet-tasting substances.
# The sense of smell: Receptors of the olfactory epithelium bind odorants (olfactory receptors) and pheromones (vomeronasal receptors)
# Behavioral and mood regulation: Receptors in the mammalian brain bind several different neurotransmitters, including serotonin, dopamine, histamine, GABA, and glutamate
# Regulation of immune system activity and inflammation: chemokine receptors bind ligands that mediate intercellular communication between cells of the immune system; receptors such as histamine receptors bind inflammatory mediators and engage target cell types in the inflammatory response. GPCRs are also involved in immune-modulation, e. g. regulating interleukin induction or suppressing TLR-induced immune responses from T cells.
# Autonomic nervous system transmission: Both the sympathetic and parasympathetic nervous systems are regulated by GPCR pathways, responsible for control of many automatic functions of the body such as blood pressure, heart rate, and digestive processes
# Cell density sensing: A novel GPCR role in regulating cell density sensing.
# Homeostasis modulation (e.g., water balance).
# Involved in growth and metastasis of some types of tumors.
# Used in the endocrine system for peptide and amino-acid derivative hormones that bind to GCPRs on the cell membrane of a target cell. This activates cAMP, which in turn activates several kinases, allowing for a cellular response, such as transcription. | 1 | Applied and Interdisciplinary Chemistry |
The original carbon isotope reference material was a Belemnite fossil from the PeeDee Formation in South Carolina, known as the Pee Dee Belemnite (PDB). This PDB standard was rapidly consumed and subsequently researchers used replacement standards such as PDB II and PDB III. The carbon isotope reference frame was later established in Vienna against a hypothetical material called the Vienna Pee Dee Belemnite (VPDB). As with the original SMOW, VPDB never existed as a physical solution or solid. In order to make measurements researchers use the reference material NBS-19, colloquially known as the Toilet Seat Limestone, which has an isotopic ratio defined relative to the hypothetical VPDB. The exact origin of NBS-19 is unknown but it was a white marble slab and has a grain size of 200-300 micrometers. To improve the accuracy of carbon isotope measurements, in 2006 the δC scale was shifted from a one-point calibration against NBS-19 to a two point-calibration. In the new system the VPDB scale is pinned to both the LSVEC LiCO reference material and to the NBS-19 limestone (Coplen et al., 2006a; Coplen et al., 2006b). NBS-19 is now also exhausted and has been replaced with IAEA-603. | 0 | Theoretical and Fundamental Chemistry |
Pregnanediol glucuronide, or 5β-pregnane-3α,20α-diol 3α-glucuronide, is the major metabolite of progesterone and the C3α glucuronide conjugate of pregnanediol (5β-pregnane-3α,20α-diol). Approximately 15 to 30% of a parenteral dose of progesterone is metabolized into pregnanediol glucuronide. While this specific isomer is referred to as pregnanediol glucuronide and is the most major form, there are actually many possible isomers of the metabolite. | 1 | Applied and Interdisciplinary Chemistry |
Another branch in targeted therapy is the increasing use of monoclonal antibodies in cancer therapy. Although monoclonal antibodies (immune proteins which can be selected to precisely bind to almost any target) have been around for decades, they were derived from mice and did not function particularly well when administered to humans, causing allergic reactions and being rapidly removed from circulation. "Humanization" of these antibodies (genetically transforming them to be as similar to a human antibody as possible) has allowed the creation of a new family of highly effective humanized monoclonal antibodies. Trastuzumab, a drug used to treat breast cancer, is a prime example. | 1 | Applied and Interdisciplinary Chemistry |
Thermocouples can generally be used in the testing of prototype electrical and mechanical apparatus. For example, switchgear under test for its current carrying capacity may have thermocouples installed and monitored during a heat run test, to confirm that the temperature rise at rated current does not exceed designed limits. | 1 | Applied and Interdisciplinary Chemistry |
Like LTR retrotransposons, non-LTR retrotransposons contain genes for reverse transcriptase, RNA-binding protein, nuclease, and sometimes ribonuclease H domain but they lack the long terminal repeats. RNA-binding proteins bind the RNA-transposition intermediate and nucleases are enzymes that break phosphodiester bonds between nucleotides in nucleic acids. Instead of LTRs, non-LTR retrotransposons have short repeats that can have an inverted order of bases next to each other aside from direct repeats found in LTR retrotransposons that is just one sequence of bases repeating itself.
Although they are retrotransposons, they cannot carry out reverse transcription using an RNA transposition intermediate in the same way as LTR retrotransposons. Those two key components of the retrotransposon are still necessary but the way they are incorporated into the chemical reactions is different. This is because unlike LTR retrotransposons, non-LTR retrotransposons do not contain sequences that bind tRNA.
They mostly fall into two types – LINEs (Long interspersed nuclear elements) and SINEs (Short interspersed nuclear elements). SVA elements are the exception between the two as they share similarities with both LINEs and SINEs, containing Alu elements and different numbers of the same repeat. SVAs are shorter than LINEs but longer than SINEs.
While historically viewed as "junk DNA", research suggests in some cases, both LINEs and SINEs were incorporated into novel genes to form new functions. | 1 | Applied and Interdisciplinary Chemistry |
Before the advent of SPPS, solution methods for chemical peptide synthesis relied on tert-butyloxycarbonyl (abbreviated Boc) as a temporary N-terminal α-amino protecting group. The Boc group is removed with acid, such as trifluoroacetic acid (TFA). This forms a positively charged amino group in the presence of excess TFA (note that the amino group is not protonated in the image on the right), which is neutralized and coupled to the incoming activated amino acid. Neutralization can either occur prior to coupling or in situ during the basic coupling reaction.
The Boc/Bzl approach retains its usefulness in reducing peptide aggregation during synthesis. In addition, Boc/benzyl SPPS may be preferred over the Fmoc/tert-butyl approach when synthesizing peptides containing base-sensitive moieties (such as depsipeptides or thioester moeities), as treatment with base is required during the Fmoc deprotection step (see below).
Permanent side-chain protecting groups used during Boc/benzyl SPPS are typically benzyl or benzyl-based groups. Final removal of the peptide from the solid support occurs simultaneously with side chain deprotection using anhydrous hydrogen fluoride via hydrolytic cleavage. The final product is a fluoride salt which is relatively easy to solubilize. Scavengers such as cresol must be added to the HF in order to prevent reactive cations from generating undesired byproducts. | 1 | Applied and Interdisciplinary Chemistry |
Keesom forces, also known as dipole–dipole interactions, result from two molecules that have permanent dipoles due to electronegativity differences between atoms in the molecule. This dipole causes a coulombic attraction between the two molecules. | 0 | Theoretical and Fundamental Chemistry |
The lipid pump sequesters carbon from the ocean's surface to deeper waters via lipids associated with overwintering vertically migratory zooplankton. Lipids are a class of hydrocarbon rich, nitrogen and phosphorus deficient compounds essential for cellular structures. This lipid carbon enters the deep ocean as carbon dioxide produced by respiration of lipid reserves and as organic matter from the mortality of zooplankton.
Compared to the more general biological pump, the lipid pump also results in a "lipid shunt", where other nutrients like nitrogen and phosphorus that are consumed in excess must be excreted back to the surface environment, and thus are not removed from the surface mixed layer of the ocean. This means that the carbon transported by the lipid pump does not limit the availability of essential nutrients in the ocean surface. Carbon sequestration via the lipid pump is therefore decoupled from nutrient removal, allowing carbon uptake by oceanic primary production to continue. In the Biological Pump, nutrient removal is always coupled to carbon sequestration; primary production is limited as carbon and nutrients are transported to depth together in the form of organic matter.
The contribution of the lipid pump to the sequestering of carbon in the deeper waters of the ocean can be substantial: the carbon transported below 1,000 metres (3,300 ft) by copepods of the genus Calanus in the Arctic Ocean almost equals that transported below the same depth annually by particulate organic carbon (POC) in this region. A significant fraction of this transported carbon would not return to the surface due to respiration and mortality. Research is ongoing to more precisely estimate the amount that remains at depth. The export rate of the lipid pump may vary from 1–9.3 g C m y across temperate and subpolar regions containing seasonally-migrating zooplankton. The role of zooplankton, and particularly copepods, in the food web is crucial to the survival of higher trophic level organisms whose primary source of nutrition is copepods. With warming oceans and increasing melting of ice caps due to climate change, the organisms associated with the lipid pump may be affected, thus influencing the survival of many commercially important fish and endangered marine mammals. As a new and previously unquantified component of oceanic carbon sequestration, further research on the lipid pump can improve the accuracy and overall understanding of carbon fluxes in global oceanic systems. | 0 | Theoretical and Fundamental Chemistry |
Gas Engine Row has many large stationary gas engines from the early 1900s. On the row is an operational Fairbanks-Morse mine hoist winding engine, a pumphouse powered by a Fairbanks-Morse engine, a horsepower 1922 Fairbanks-Morse type YV engine connected to a large alternator, an enormous 1914 Chicago-Pneumatic hot-bulb air compressor, an Western engine, a Western engine, a Western engine and many other stationary engines. Almost all of the engines on Gas Engine Row can be seen running during the shows.
Steam Engine Row showcases many different types and sizes of stationary steam engines; from a monstrous Allis Chalmers Corliss engine with a flywheel, to a small J. Lefel & Sons portable engine. They are all powered by steam from two large boilers, nicknamed Pat and Rich, after two long-time museum volunteers who maintain and operate them. | 1 | Applied and Interdisciplinary Chemistry |
High power mercury vapor black light lamps are made in power ratings of 100 to 1,000 watts. These do not use phosphors, but rely on the intensified and slightly broadened 350–375 nm spectral line of mercury from high pressure discharge at between , depending upon the specific type. These lamps use envelopes of Woods glass or similar optical filter coatings to block out all the visible light and also the short wavelength (UVC) lines of mercury at 184.4 and 253.7 nm, which are harmful to the eyes and skin. A few other spectral lines, falling within the pass band of the Woods glass between 300 and 400 nm, contribute to the output.
These lamps are used mainly for theatrical purposes and concert displays. They are more efficient UVA producers per unit of power consumption than fluorescent tubes. | 0 | Theoretical and Fundamental Chemistry |
In organic chemistry, an acyl cyanide is a functional group with the formula and structure . It consists of an acyl group () attached to cyanide (). Examples include acetyl cyanide, formyl cyanide, and oxalyl dicyanide. Acyl cyanides are reagents in organic synthesis. | 0 | Theoretical and Fundamental Chemistry |
The E2 subunit, or dihydrolipoyl acetyltransferase, for both prokaryotes and eukaryotes, is generally composed of three domains. The N-terminal domain (the lipoyl domain), consists of 1–3 lipoyl groups of approximately 80 amino acids each. The peripheral subunit binding domain (PSBD), serves as a selective binding site for other domains of the E1 and E3 subunits. Finally, the C-terminal (catalytic) domain catalyzes the transfer of acetyl groups and acetyl-CoA synthesis. In Gammaproteobacteria, 24 copies of E2 form the cubic core of the pyruvate dehydrogenase complex, in which 8 E2 homotrimers are located at the vertices of the cubic core particle. | 1 | Applied and Interdisciplinary Chemistry |
No federal legislation lays out protocols or restrictions about human genetic engineering. This subject is governed by overlapping regulations from local and federal agencies, including the Department of Health and Human Services, the FDA and NIH's Recombinant DNA Advisory Committee. Researchers seeking federal funds for an investigational new drug application, (commonly the case for somatic human genetic engineering,) must obey international and federal guidelines for the protection of human subjects.
NIH serves as the main gene therapy regulator for federally funded research. Privately funded research is advised to follow these regulations. NIH provides funding for research that develops or enhances genetic engineering techniques and to evaluate the ethics and quality in current research. The NIH maintains a mandatory registry of human genetic engineering research protocols that includes all federally funded projects.
An NIH advisory committee published a set of guidelines on gene manipulation. The guidelines discuss lab safety as well as human test subjects and various experimental types that involve genetic changes. Several sections specifically pertain to human genetic engineering, including Section III-C-1. This section describes required review processes and other aspects when seeking approval to begin clinical research involving genetic transfer into a human patient. The protocol for a gene therapy clinical trial must be approved by the NIH's Recombinant DNA Advisory Committee prior to any clinical trial beginning; this is different from any other kind of clinical trial.
As with other kinds of drugs, the FDA regulates the quality and safety of gene therapy products and supervises how these products are used clinically. Therapeutic alteration of the human genome falls under the same regulatory requirements as any other medical treatment. Research involving human subjects, such as clinical trials, must be reviewed and approved by the FDA and an Institutional Review Board. | 1 | Applied and Interdisciplinary Chemistry |
In organic chemistry, the term acetylenic designates
*A doubly unsaturated position (sp-hybridized) on a molecular framework, for instance in an alkyne such as acetylene;
*An ethynyl fragment, HCC–, or substituted homologue. | 0 | Theoretical and Fundamental Chemistry |
Clay minerals can be classified as 1:1 or 2:1. A 1:1 clay would consist of one tetrahedral sheet and one octahedral sheet, and examples would be kaolinite and serpentinite. A 2:1 clay consists of an octahedral sheet sandwiched between two tetrahedral sheets, and examples are talc, vermiculite, and montmorillonite. The layers in 1:1 clays are uncharged and are bonded by hydrogen bonds between layers, but 2:1 layers have a net negative charge and may be bonded together either by individual cations (such as potassium in illite or sodium or calcium in smectites) or by positively charged octahedral sheets (as in chlorites).
Clay minerals include the following groups:
* Kaolin group which includes the minerals kaolinite, dickite, halloysite, and nacrite (polymorphs of ).
** Some sources include the kaolinite-serpentine group due to structural similarities.
* Smectite group which includes dioctahedral smectites, such as montmorillonite, nontronite and beidellite, and trioctahedral smectites, such as saponite. In 2013, analytical tests by the Curiosity rover found results consistent with the presence of smectite clay minerals on the planet Mars.
* Illite group which includes the clay-micas. Illite is the only common mineral in this group.
* Chlorite group includes a wide variety of similar minerals with considerable chemical variation.
* Other 2:1 clay types exist such as palygorskite (also known as attapulgite) and sepiolite, clays with long water channels internal to their structure.
Mixed layer clay variations exist for most of the above groups. Ordering is described as a random or regular order and is further described by the term reichweite, which is German for range or reach. Literature articles will refer to an R1 ordered illite-smectite, for example. This type would be ordered in an illite-smectite-illite-smectite (ISIS) fashion. R0 on the other hand describes random ordering, and other advanced ordering types are also found (R3, etc.). Mixed layer clay minerals which are perfect R1 types often get their own names. R1 ordered chlorite-smectite is known as corrensite, R1 illite-smectite is rectorite.
X-ray rf(001) is the spacing between layers in nanometers, as determined by X-ray crystallography. Glycol (mg/g) is the adsorption capacity for glycol, which occupies the interlayer sites when the clay is exposed to a vapor of ethylene glycol at for eight hours. CEC is the cation exchange capacity of the clay. (%) is the percent content of potassium oxide in the clay. DTA describes the differential thermal analysis curve of the clay. | 0 | Theoretical and Fundamental Chemistry |
The location of FAM227B, 15q21.2, was found to be associated with oral cancer. The 15q21.2 locus is mentioned in other literature as well. FGF7 is a neighbour of FAM227B in the 15q21.2 locus (rs10519227), and encodes for the fibroblast growth factor, which is involved in processes such as embryonic development, cell growth, tissue repair, tumor growth, invasion, and morphogenesis. FGF works as a signal for thyroid gland development, and an SNP on intron 2 of FGF7 has been associated with thyroid growth/goiter growth. This association was only significant at the genome level in males. It was found that the abnormal goiter growth is likely due to variant signals that cause increased levels of TSH. FAM227B was found to be related to at least some of the 48 significant DMRs (differentially methylated regions) between HF (high fertile) and LF (low fertile) groups in the genome of spermatozoa from boar animal model. FAM227B was found to be upregulated in LOXL2 knockdown. Knocking down LOXL2 results in lower levels of H3K4ox, resulting in chromatin decompaction, thus continuing activation of DNA damage response. This results in anticancer agents being more effective against cancerous cell lines. FAM227B was found to be a genetic risk variant in breast cancer. FAM227B was differentially expressed in prostrate genes of Esr2 knockout rats compared to wildtype rats. Esr2 is involved in anti-proliferation and differentiation. FAM227B was part of 20 upregulated genes in chorionic girdle during trophoblast development in horses. Protein FAM227B was differentially expressed in cardiovascular disease. FAM227B was found to be a candidate causal gene for lung cancer. FAM227B has a predicted p53 binding site. | 1 | Applied and Interdisciplinary Chemistry |
Using the Reynolds-Colburn analogy for turbulent flow with a thermal log and viscous sub layer model, the following correlation for turbulent heat transfer for is applicable
where | 1 | Applied and Interdisciplinary Chemistry |
The Froude number is used to compare the wave making resistance between bodies of various sizes and shapes.
In free-surface flow, the nature of the flow (supercritical or subcritical) depends upon whether the Froude number is greater than or less than unity.
One can easily see the line of "critical" flow in a kitchen or bathroom sink. Leave it unplugged and let the faucet run. Near the place where the stream of water hits the sink, the flow is supercritical. It hugs the surface and moves quickly. On the outer edge of the flow pattern the flow is subcritical. This flow is thicker and moves more slowly. The boundary between the two areas is called a "hydraulic jump". The jump starts where the flow is just critical and Froude number is equal to 1.0.
The Froude number has been used to study trends in animal locomotion in order to better understand why animals use different gait patterns as well as to form hypotheses about the gaits of extinct species.
In addition particle bed behavior can be quantified by Froude number (Fr) in order to establish the optimum operating window. | 1 | Applied and Interdisciplinary Chemistry |
Greenhouse gases are infrared active, meaning that they absorb and emit infrared radiation in the same long wavelength range as what is emitted by the Earth's surface, clouds and atmosphere.
99% of the Earths dry atmosphere (excluding water vapor) is made up of nitrogen () (78%) and oxygen () (21%). Because their molecules contain two atoms of the same element, they have no asymmetry in the distribution of their electrical charges, and so are almost totally unaffected by infrared thermal radiation, with only an extremely minor effect from collision-induced absorption. A further 0.9% of the atmosphere is made up by argon (Ar), which is monatomic, and so completely transparent to thermal radiation. On the other hand, carbon dioxide (0.04%), methane, nitrous oxide and even less abundant trace gases account for less than 0.1% of Earths atmosphere, but because their molecules contain atoms of different elements, there is an asymmetry in electric charge distribution which allows molecular vibrations to interact with electromagnetic radiation. This makes them infrared active, and so their presence causes greenhouse effect. | 1 | Applied and Interdisciplinary Chemistry |
Similar N-glycan biosynthesis pathway have been found in prokaryotes and Archaea. However, compared to eukaryotes, the final glycan structure in eubacteria and archaea does not seem to differ much from the initial precursor made in the endoplasmic reticulum. In eukaryotes, the original precursor oligosaccharide is extensively modified en route to the cell surface. | 0 | Theoretical and Fundamental Chemistry |
Plastoquinone is found within photosystem II in two specific binding sites, known as Q and Q. The plastoquinone at Q, the primary binding site, is very tightly bound, compared to the plastoquinone at Q, the secondary binding site, which is much more easily removed. Q is only transferred a single electron, so it has to transfer an electron to Q twice before Q is able to pick up two protons from the stroma and be replaced by another plastoquinone molecule. The protonated Q then joins a pool of free plastoquinone molecules in the membrane of the thylakoid. The free plastoquinone molecules eventually transfer electrons to the water-soluble plastocyanin so as to continue the light-dependent reactions. There are additional plastoquinone binding sites within photosystem II (Q and possibly Q), but their function and/or existence have not been fully elucidated. | 0 | Theoretical and Fundamental Chemistry |
Bengt Nordén graduated 1967 with a Master of Science degree in chemistry, theoretical physics and mathematics from Lund University and was awarded his Ph.D. in 1971 from Lund University where he became Associate Professor of Inorganic Chemistry in 1972. In 1979 he was appointed to the Chair Professorship of Physical Chemistry of Chalmers University of Technology.
Nordén's research concerns optical Linear dichroism spectroscopy of macroscopically oriented, mainly bio-macromolecular systems. He has developed novel DNA-binding ligands, such as bis-intercalating compounds and peptide nucleic acids (PNA), and demonstrated DNA-ligand reorganisations between groove-binding and intercalation binding geometries involving extreme activation energies and recognition due to kinetic (in contrast to thermodynamic) selection. His method “Site Specific Linear Dichroism by Molecular Replacement” methodology applied to DNA complexes with RecA and Rad51 recombination proteins has revealed details of the recombination mechanism and is also applied to study structure of membrane proteins in a true membrane environment.
Nordén was councilor for Science and Technology to the Swedish Government in 1991-1994. He was Chairman of the selection committee for the European Science Foundation’s Young Research Investigator Awards 2003-2006; chemistry editor of the Swedish National Encyclopedia, Chairman of the Chemistry Section of the Swedish Research Council 1996-2000. He is currently Chair of the Nanyang Technological University Research Council (Singapore) and Chair of the board of editors of Quarterly Reviews of Biophysics
Nordén is a member of the Royal Swedish Academy of Sciences since 1991 and was member of the Nobel Committee for Chemistry from 1995 to 2004, and the Committees chairman from 2000 to 2003 and the Academys Chemistry Section chairman 2004-2009. He is a member of the Royal Swedish Academy of Engineering Sciences, The Royal Physiographic Society in Lund, The Royal Society of Arts and Sciences in Gothenburg (Kungliga Vetenskaps- och Vitterhetssamhället i Göteborg), The National Academy of Sciences of Germany (German Academy of Sciences Leopoldina), the Swedish Academy of Engineering Sciences in Finland, The Norwegian Academy of Science, The Finnish Society of Science and Letters, and The Academy of Sciences for the Developing World (TWAS). | 0 | Theoretical and Fundamental Chemistry |
In the study of abstract polytopes, a chiral polytope is that it is a polytope that is as symmetric as possible without being mirror-symmetric, formalized in terms of the action of the symmetry group of the polytope on its flags. | 0 | Theoretical and Fundamental Chemistry |
CO at high pressures has antimicrobial properties. While its effectiveness has been shown for various applications, the mechanisms of inactivation have not been fully understood although they have been investigated for more than 60 years. | 0 | Theoretical and Fundamental Chemistry |
He helped start MITs chemical engineering curriculum in the late 1880s. In 1887, he was appointed by the newly formed Massachusetts Board of Health to a landmark study of sanitary quality of the states inland waters. As consulting chemist to the Massachusetts State Board of Health, he was in charge of the famous Lawrence Experiment Station laboratory conducting the water sampling, testing, and analysis. There he put to work the environmental chemist and first female graduate of MIT, Ellen Swallow Richards. This research created the famous "normal chlorine" map of Massachusetts that was the first of its kind and was the template for others. As a result, Massachusetts established the first water-quality standards in America, and the first modern sewage treatment plant was created.
As a professor, Drown published a number of papers on metallurgy, mostly in Transactions of the American Institute of Mining Engineers. He was a founding member of the Institute, and served as its secretary, and editor of its Transactions from 1871 till 1884. He was elected its president in 1897. | 0 | Theoretical and Fundamental Chemistry |
Researchers at Bristol-Myers Squibb found that increased steric bulk of the N-terminal amino acid side-chain led to increased stability. To additionally increase stability the trans-rotamer was stabilized with a cis-4,5-methano substitution of the pyrrolidine ring, resulting in an intramolecular van-der-Waals interaction, thus preventing intramolecular cyclisation. Because of that increased stability, the researchers continued their investigation on cis-4,5-methano cyanopyrrolidines and came across with a new adamantyl derivative, which showed extraordinary ex vivo DPP-4 inhibition in rat plasma. Also noted, high microsomal turnover rate which indicated that the derivative was quickly converted to an active metabolite. After hydroxylation on the adamantyl group they had a product with better microsomal stability and improved chemical stability. That product was named saxagliptin (Onglyza) (Figure 6). In June 2008 AstraZeneca and Bristol-Myers Squibb submitted a new drug application for Onglyza in the United States and a marketing authorization application in Europe. Approval was granted in the United States by the FDA in July 2009 for Onglyza 5 mg and Onglyza 2.5 mg. This was later combined with extended-release metformin (taken once daily) and approved by the FDA in January 2011 under the trade name Kombiglyze XR. | 1 | Applied and Interdisciplinary Chemistry |
The great majority of photogeochemical research is performed in the laboratory, as it is easier to demonstrate and observe a particular reaction under controlled conditions. This includes confirming the identity of materials, designing reaction vessels, controlling light sources, and adjusting the reaction atmosphere. However, observation of natural phenomena often provides initial inspiration for further study. For example, during the 1970s it was generally agreed that nitrous oxide (NO) has a short residence time in the troposphere, although the actual explanation for its removal was unknown. Since NO does not absorb light at wavelengths greater than 280 nm, direct photolysis had been discarded as a possible explanation. It was then observed that light would decompose chloromethanes when they were absorbed on silica sand, and this occurred at wavelengths far above the absorption spectra for these compounds. The same phenomenon was observed for NO, leading to the conclusion that particulate matter in the atmosphere is responsible for the destruction of NO via surface-sensitized photolysis. Indeed, the idea of such a sink for atmospheric NO was supported by several reports of low concentrations of NO in the air above deserts, where there is a high amount of suspended particulate matter. As another example, the observation that the amount of nitrous acid in the atmosphere greatly increases during the day lead to insight into the surface photochemistry of humic acids and soils and an explanation for the original observation. | 0 | Theoretical and Fundamental Chemistry |
The Golden Gate Cloning principle can also be applied to perform mutagenesis termed Golden Mutagenesis. The technology is easy to implement as a web tool is available for primer design (https://msbi.ipb-halle.de/GoldenMutagenesisWeb/) and the vectors are deposited at addgene (http://www.addgene.org/browse/article/28196591/). | 1 | Applied and Interdisciplinary Chemistry |
Meta-selective C–H functionalization refers to the regioselective reaction of a substituted aromatic ring on the C–H bond meta to the substituent.
Substituted aromatic ring is an important type of substructure in pharmaceuticals and industrial compounds. Thus, synthetic methods towards substituted aromatic rings are always of great interest to chemists.
Traditionally, regioselectivity on the aromatic ring is achieved by the electronic effect of substituents. Taking the well-known Friedel–Craft electrophilic aromatic substitution as example, electron donating groups direct the electrophile to ortho-/para-position while electron withdrawing groups direct the electrophile to meta-position. However, with complicated systems, electronic difference between different C–H bonds can be subtle and electronic directing effect alone could become less synthetically useful.
The fast development of C–H activation in the past few decades provides synthetic chemists with the powerful tools to synthesize functionalized aromatic compounds with high selectivity. The widely used approach to achieve ortho-selectivity involves metal-chelating directing groups, which forms a relatively stable 6- or 7-membered cyclic pre-transition state to bring the metal catalyst to the proximity of the ortho-hydrogen. However, applying the same strategy to meta- or para- C-H functionalization does not work because the corresponding cyclophane-like cyclic pre-transition state is highly strained. Thus, while ortho-selectivity has been achieved by numerous catalytic systems, meta- and para-selectivity remains a challenge.
In recent years, new strategies that override the electronic and steric bias have been developed to address meta-C–H functionalization. However, before these discoveries, synthesis of meta-substituted aromatic compounds could be either limited or cumbersome. For example, before the development of the C–H activation involving one-pot synthetic route to meta-substituted phenol derivatives by Maleczka and co-workers, the traditional synthesis requires 10 steps from TNT. Some early attempts utilize steric and electronic effects to achieve meta-selectivity. However, they are either limited to certain structure of substrates or are not highly selective. In recent years, several highly selective meta-C-H functionalization strategies have been reported which can override the intrinsic electronic and steric properties of the substrates and can apply to a wide range of substrate derivatives. The development of the modern meta-C-H functionalization strategies “open doors for numerous possibilities” for synthesis and catalyst development. | 0 | Theoretical and Fundamental Chemistry |
In fluid dynamics, it is sometimes more appropriate to work in terms of kinematic viscosity (sometimes also called the momentum diffusivity), defined as the ratio of the dynamic viscosity () over the density of the fluid (). It is usually denoted by the Greek letter nu ():
and has the dimensions , therefore resulting in the SI units and the derived units:
: <math>
[\nu]
= \mathrm {\frac {m^2} {s}}
= \mathrm {\frac {N{\cdot}m} {kg} {\cdot}s}
= \mathrm {\frac {J}{kg} {\cdot}s}
energy per unit mass multiplied by time. | 1 | Applied and Interdisciplinary Chemistry |
The innate immune system has evolved to protect against infection by detecting pathogen-associated molecular patterns (PAMPs), and triggering a complex set of responses collectively known as "inflammation". Many cells express specific pattern recognition receptors (PRRs) for exogenous RNA including toll-like receptor 3,7,8 (TLR3, TLR7, TLR8), the RNA helicase RIG1 (RARRES3), protein kinase R (PKR, a.k.a. EIF2AK2), members of the oligoadenylate synthetase family of proteins (OAS1, OAS2, OAS3), and others. All of these proteins can specifically bind to exogenous RNA molecules and trigger an immune response.
The specific chemical, structural or other characteristics of long RNA molecules that are required for recognition by PRRs remain largely unknown despite intense study. At any given time, a typical mammalian cell may contain several hundred thousand mRNA and other, regulatory long RNA molecules. How cells distinguish exogenous long RNA from the large amount of endogenous long RNA is an important open question in cell biology. Several reports suggest that phosphorylation of the 5-end of a long RNA molecule can influence its immunogenicity, and specifically that 5-triphosphate RNA, which can be produced during viral infection, is more immunogenic than 5-diphosphate RNA, 5-monophosphate RNA or RNA containing no 5 phosphate. However, in vitro-transcribed (ivT) long RNA containing a 7-methylguanosine cap (present in eukaryotic mRNA) is also highly immunogenic despite having no 5 phosphate, suggesting that characteristics other than 5'-phosphorylation can influence the immunogenicity of an RNA molecule.
Eukaryotic mRNA contains chemically modified nucleotides such as N-methyladenosine, 5-methylcytidine, and 2'-O-methylated nucleotides. Although only a very small number of these modified nucleotides are present in a typical mRNA molecule, they may help prevent mRNA from activating the innate immune system by disrupting secondary structure that would resemble double-stranded RNA (dsRNA), a type of RNA thought to be present in cells only during viral infection.
The immunogenicity of long RNA has been used to study both innate and adaptive immunity. | 1 | Applied and Interdisciplinary Chemistry |
The simplest type of glow discharge is a direct-current glow discharge. In its simplest form, it consists of two electrodes in a cell held at low pressure (0.1–10 torr; about 1/10000th to 1/100th of atmospheric pressure). A low pressure is used to increase the mean free path; for a fixed electric field, a longer mean free path allows a charged particle to gain more energy before colliding with another particle. The cell is typically filled with neon, but other gases can also be used. An electric potential of several hundred volts is applied between the two electrodes. A small fraction of the population of atoms within the cell is initially ionized through random processes, such as thermal collisions between atoms or by gamma rays. The positive ions are driven towards the cathode by the electric potential, and the electrons are driven towards the anode by the same potential. The initial population of ions and electrons collides with other atoms, exciting or ionizing them. As long as the potential is maintained, a population of ions and electrons remains. | 0 | Theoretical and Fundamental Chemistry |
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